Research IndicatorsGraph generated 31 August 2019 using data from PubMed using criteria.
Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic. Tag cloud generated 31 August, 2019 using data from PubMed, MeSH and CancerIndex
Specific Cancers (7)
Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.
Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).
OMIM, Johns Hopkin University
Referenced article focusing on the relationship between phenotype and genotype.
International Cancer Genome Consortium.
Summary of gene and mutations by cancer type from ICGC
Cancer Genome Anatomy Project, NCI
COSMIC, Sanger Institute
Somatic mutation information and related details
GEO Profiles, NCBI
Search the gene expression profiles from curated DataSets in the Gene Expression Omnibus (GEO) repository.
Latest Publications: CLDN4 (cancer-related)
Zheng Q, Wang C, Wang L, et al.Interaction with SP1, but not binding to the E-box motifs, is responsible for BHLHE40/DEC1-induced transcriptional suppression of CLDN1 and cell invasion in MCF-7 cells.
Mol Carcinog. 2018; 57(9):1116-1129 [PubMed
] Related Publications
Basic helix-loop-helix family member e40 (BHLHE40) is located in 3p26.1 and acts as a transcriptional repressor of the circadian rhythm by suppressing the expression of the clock genes and clock-controlled genes. Recent research indicated that BHLHE40 may be involved in regulating tumor cell progression. However the mechanism by which BHLHE40 regulates the invasion and metastasis of tumor cells is unclear. Our in vitro assays showed that BHLHE40 promoted tumor cell invasion while BHLHE40 silencing by siRNA suppressed tumor cell invasion of MCF-7 cells. BHLHE40 suppressed the mRNA and protein expression of CLDN1 CLDN4 and CDH1 and promoted the expression of SNAI1 and SNAI2. Reporter assays demonstrated that BHLHE40 suppressed CLDN1 transcription but not through direct binding to the E-box motifs in the CLDN1 promoter. Further studies demonstrated BHLHE40 suppressed CLDN1 transcription by preventing the interaction between SP1 and a specific motif within the promoter region of CLDN1. BHLHE40 could not further suppress CLDN1 transactivation after SP1 siRNA transfection that is, BHLHE40-induced suppression of CLDN1 relied on SP1. Furthermore our data indicated that SP1 was a major regulator of CLDN1 transcription by binding to a specific motif that was located at -233 to -61 bp upstream of the transcription start site. Immunoprecipitation and co-localization data revealed an interaction between BHLHE40 and SP1. By constructing deletion mutants we found that the BHLH and Orange regions are both essential for the BHLHE40-SP1 interaction. BHLHE40 probably acts as an inhibitory nuclear cofactor or perhaps recruits other inhibitory cofactors to inhibit the SP1-mediated CLDN1 transactivation. These results suggest that BHLHE40 facilitates cell invasion and may be used as a novel target for breast cancer prevention and treatment.
BACKGROUND: The subtype of claudin-low breast cancer can be reliably determined only by gene-expression profiling. Attempts have been made to develop immunohistochemical surrogates, which nearly always focus on membranous claudin expression.
METHODS: We assessed the immunohistochemical expression of both membranous and cytoplasmic claudins 3, 4 and 7 in a series of 197 non-metastatic breast cancers, enriched with triple-negative breast cancers (TNBCs; 60%). The expression of epithelial-to-mesenchymal transition-regulating transcription factors Sip1, Zeb1 and vimentin had previously been determined in the same material.
RESULTS: In multivariate analysis, strong cytoplasmic claudin 3 expression was associated with poor relapse-free survival (RFS), disease-free survival, distant disease-free survival, breast cancer-specific survival and overall survival among TNBC patients (for RFS, RR 5.202, 95% CI 1.210-22.369, p = 0.027, vs. T-class, RR 0.663, 95% CI 0.168-2.623, p = 0.558, and N-class, RR 3.940, 95% CI 0.933-16.631, p = 0.062). Cytoplasmic claudin 3 expression was also associated with strong nuclear Sip1 expression (p = 0.000053), TNBC phenotype (p = 0.012) and within them, non-basal-like phenotype (p = 0.026). Cytoplasmic claudin 7 was associated with dismal RFS (RR 6.328, 95% CI 1.401-28.593, p = 0.016, vs. T-class, RR 0.692, 95% CI 0.242-1.982, p = 0.493, and N-class, RR 2.981, 95% CI 1.1016-8.749, p = 0.047). Low cytoplasmic expression of claudins 3, 4 and 7 together also predicted poor RFS (RR 6.070, 95% CI 1.347-27.363, p = 0.019, vs. T-class, RR 0.677, 95% CI 0.237-1.934, p = 0.467, and N-class, RR 3.167, 95% CI 1.079-9.290, p = 0.036).
CONCLUSIONS: Immunohistochemical expression levels of cytoplasmic claudins 3 and 7 appear to be novel prognostic factors in TNBC.
Liu Y, Chang K, Fu K, et al.DNA demethylation of claudin-4 suppresses migration and invasion in laryngeal squamous carcinoma cells.
Hum Pathol. 2018; 75:71-80 [PubMed
] Related Publications
Claudin-4 (CLDN4) is a member of the claudin transmembrane protein family, which consists of integral membrane proteins that are components of the epithelial cell tight junctions; these tight junctions regulate movement of solutes and ions through the paracellular space. CLDN4 is also a differentiation marker and is believed to indicate an epithelial phenotype. However, the role of CLDN4 in laryngeal squamous carcinoma is still unclear. Here, we showed that CLDN4 expression was down-regulated in laryngeal squamous carcinoma tissues and negatively correlated with methyl-CpG-binding protein 2. In addition, CLDN4 was hypermethylated in HEp-2 cells. DNA demethylation of CLDN4 by 5-aza-2'-deoxycytidine suppressed migration and invasion of HEp-2 cells, whereas CLDN4 silencing restored the migration and invasion of HEp-2 cells. Therefore, CLDN4 plays a key role in laryngeal squamous carcinoma progression.
Metastatic melanoma is an aggressive skin cancer and is one of the global malignancies with high mortality and morbidity. It is essential to identify and verify diagnostic biomarkers of early metastatic melanoma. Previous studies have systematically assessed protein biomarkers and mRNA-based expression characteristics. However, molecular markers for the early diagnosis of metastatic melanoma have not been identified. To explore potential regulatory targets, we have analyzed the gene microarray expression profiles of malignant melanoma samples by co-expression analysis based on the network approach. The differentially expressed genes (DEGs) were screened by the EdgeR package of R software. A weighted gene co-expression network analysis (WGCNA) was used for the identification of DEGs in the special gene modules and hub genes. Subsequently, a protein-protein interaction network was constructed to extract hub genes associated with gene modules. Finally, twenty-four important hub genes (RASGRP2, IKZF1, CXCR5, LTB, BLK, LINGO3, CCR6, P2RY10, RHOH, JUP, KRT14, PLA2G3, SPRR1A, KRT78, SFN, CLDN4, IL1RN, PKP3, CBLC, KRT16, TMEM79, KLK8, LYPD3 and LYPD5) were treated as valuable factors involved in the immune response and tumor cell development in tumorigenesis. In addition, a transcriptional regulatory network was constructed for these specific modules or hub genes, and a few core transcriptional regulators were found to be mostly associated with our hub genes, including GATA1, STAT1, SP1, and PSG1. In summary, our findings enhance our understanding of the biological process of malignant melanoma metastasis, enabling us to identify specific genes to use for diagnostic and prognostic markers and possibly for targeted therapy.
Shah K, Patel S, Mirza S, Rawal RMUnravelling the link between embryogenesis and cancer metastasis.
Gene. 2018; 642:447-452 [PubMed
] Related Publications
PURPOSE: Cancer as opposed to embryonic development is characterized by dysregulated, uncontrolled and clonal growth of cells. Inspite of that they share certain commonality in gene expression patterns and a number of cellular & molecular features. Consequently, in the present study we aimed to evaluate the role of a definite set of genes in fetal liver, primary liver cancers and metastatic liver tissue.
METHODS: The relative expression of fourteen candidate genes obtained by data mining and manual curation of published data (CXCL12, CXCR4, CK7, CDH1, CTNNB1, CLDN4, VEGFA, HIF1A, MMP9, p53, OPN, CDKN2A, TGFBR2, MUC16, β-actin) were performed on 62 tissues (32 liver metastasis tissues and 30 primary Liver cancer tissues), Fetal liver tissues (below and above 20weeks of gestation) and 2 sets of control samples by real-time quantitative reverse transcription PCR (qRT-PCR).
RESULTS: Results showed significant down-regulation of MMP9 and TP53 in Fetal liver above 20weeks of gestation whereas it was up-regulated in fetal liver below 20weeks of gestation, primary liver cancers and liver metastasis. Contradictory to that OPN and CDKN2A were significantly up-regulated in primary liver cancer, liver metastasis; down-regulated in fetal liver above 20weeks of gestation but were not expressed during early embryo development (below 20weeks of gestation). Moreover, MMP9 and TP53 demonstrated a strong correlation with MUC16 whereas CDKN2A and OPN showed correlation with CXCL12/CXCR4 signifying that MUC16, CXCL12/CXCR4 might be involved in the complex process of cancer metastasis.
CONCLUSION: MMP9, OPN, TP53 and CDKN2A were the identified markers that were expressed in a similar pattern in early embryonic development and cancer development & invasion suggesting that these genes are activated during embryogenesis and might be re-expressed in cancer metastasis. Moreover, these genes govern a pathway that might be activated during cancer metastasis. Thus, targeting these molecules may provide better treatment for metastatic liver cancers.
Thousands of genes have been well demonstrated to play important roles in cancer progression. As genes do not function in isolation, they can be grouped into "networks" based on their interactions. In this study, we discover a network regulating Claudin-4 in gastric cancer. We observe that Claudin-4 is up-regulated in gastric cancer and is associated with poor prognosis. Claudin-4 reinforce proliferation, invasion, and EMT in AGS, HGC-27, and SGC-7901 cells, which could be reversed by miR-596 and miR-3620-3p. In addition, lncRNA-KRTAP5-AS1 and lncRNA-TUBB2A could act as competing endogenous RNAs to affect the function of Claudin-4. Our results suggest that non-coding RNAs play important roles in the regulatory network of Claudin-4. As such, non-coding RNAs should be considered as potential biomarkers and therapeutic targets against gastric cancer.Non-coding RNAs can modify the expression of proteins in cancer networks. Here the authors reveal a regulatory network in gastric cancer whereby claudin-4 expression is reduced by specific miRNAs, which are in turn bound by specific lncRNAs acting as competing endogenous RNAs (ceRNAs), resulting in increased claudin-4 expression.
Makise N, Yoshida A, Komiyama M, et al.Dedifferentiated Liposarcoma With Epithelioid/Epithelial Features.
Am J Surg Pathol. 2017; 41(11):1523-1531 [PubMed
] Related Publications
Dedifferentiated liposarcoma (DDLPS) demonstrates a variety of growth patterns, and their histologic resemblance to other spindle cell mesenchymal tumors has been widely recognized. However, epithelioid morphology in DDLPS has only rarely been documented. Here, we report 6 cases of DDLPS with striking epithelioid/epithelial features. The patients were 5 men and 1 woman with a median age of 61 years. All tumors were located in the internal trunk. During follow-up of 1 to 41 months, local recurrence, distant metastases, and tumor-related death occurred in 4, 2, and 4 patients, respectively. Beside well-differentiated liposarcoma component and conventional high-grade spindle cell morphology, all tumors focally exhibited growth comprising small or large epithelioid cells in diffuse or sheet-like proliferation. Rhabdoid cells were present in 2 cases. All 5 tumors tested harbored MDM2 amplification. Cytokeratin and/or epithelial membrane antigen were at least focally positive in all 5 tumors tested. One case contained a small focus of novel heterologous epithelial differentiation with acinar structures, wherein cytokeratin, MOC31, and claudin-4 were diffusely expressed and H3K27me3 expression was lost. DDLPS with epithelioid/epithelial features may lead to misdiagnosis of carcinoma or mesothelioma, and their diagnosis should be based on correlation with clinicopathologic and molecular findings. The epithelioid morphology in DDLPS may suggest an aggressive behavior based on this small series. In addition, we document 2 cases of MDM2-amplified undifferentiated neoplasm with epithelioid features in the internal trunk that lacked association with well-differentiated liposarcoma histology and showed rapid clinical course. Whether these latter tumors belong to DDLPS with epithelioid features requires further study.
Azimi I, Milevskiy MJG, Kaemmerer E, et al.TRPC1 is a differential regulator of hypoxia-mediated events and Akt signalling in PTEN-deficient breast cancer cells.
J Cell Sci. 2017; 130(14):2292-2305 [PubMed
] Related Publications
Hypoxia is a feature of the tumour microenvironment that promotes invasiveness, resistance to chemotherapeutics and cell survival. Our studies identify the transient receptor potential canonical-1 (TRPC1) ion channel as a key component of responses to hypoxia in breast cancer cells. This regulation includes control of specific epithelial to mesenchymal transition (EMT) events and hypoxia-mediated activation of signalling pathways such as activation of the EGFR, STAT3 and the autophagy marker LC3B, through hypoxia-inducible factor-1α (HIF1α)-dependent and -independent mechanisms. TRPC1 regulated HIF1α levels in PTEN-deficient MDA-MB-468 and HCC1569 breast cancer cell lines. This regulation arises from effects on the constitutive translation of HIF1α under normoxic conditions via an Akt-dependent pathway. In further support of the role of TRPC1 in EMT, its expression is closely associated with EMT- and metastasis-related genes in breast tumours, and is enhanced in basal B breast cancer cell lines. TRPC1 expression is also significantly prognostic for basal breast cancers, particularly those classified as lymph node positive. The defined roles of TRPC1 identified here could be therapeutically exploited for the control of oncogenic pathways in breast cancer cells.
Hahn-Strömberg V, Askari S, Ahmad A, et al.Expression of claudin 1, claudin 4, and claudin 7 in colorectal cancer and its relation with CLDN DNA methylation patterns.
Tumour Biol. 2017; 39(4):1010428317697569 [PubMed
] Related Publications
Altered claudin expression has been described in colon, prostatic, ovarian, and breast carcinoma. However, the role of epigenetic modifications in these genes and their role in colorectal cancer is unknown. We aimed our study to investigate whether claudin protein expression and methylation of CLDN can influence the tumorigenesis of colorectal cancer. A total of 31 patients diagnosed with colorectal carcinoma was used in this study. Immunohistochemical staining was used to study protein expression in both tumor and the adjacent nonneoplastic mucosa of claudin 1, 4, and 7. To detect the DNA methylation pattern of CLDN1, 4, and 7, genomic DNA was extracted from both the tumor and the adjacent nonneoplastic mucosa. Methylation analysis was carried out using bisulfite pyrosequencing. Cell membrane staining intensity of all claudins was found significantly lower in colorectal cancer tissues when compared to paired normal mucosa (p ≤ 0.001). For claudin 4, the percentage of cells staining positively was also significantly reduced (p = 0.04). In normal mucosa, cytoplasm showed no staining for claudins in any patient, whereas in paired colorectal cancer tissues, significant cytoplasmic staining appeared both for claudin 1 (p = 0.04) and claudin 4 (p = 0.01). Tumor samples were significantly hypomethylated in CLDN1 (p < 0.05). In conclusion, our results show that CLDN1 is significantly hypomethylated in tumor samples and that the membrane staining intensity for claudin 1, 4, and 7 is significantly lower in colorectal cancer tissues than in adjacent nonneoplastic tissue. Colorectal cancer cells showed dystopic cytoplasmic location of claudins.
BACKGROUND: Bacterial toxins have evolved to an effective therapeutic option for cancer therapy. The Clostridium perfringens enterotoxin (CPE) is a pore-forming toxin with selective cytotoxicity. The transmembrane tight junction proteins claudin-3 and -4 are known high affinity CPE receptors. Their expression is highly upregulated in human cancers, including breast, ovarian and colon carcinoma. CPE binding to claudins triggers membrane pore complex formation, which leads to rapid cell death. Previous studies demonstrated the anti-tumoral effect of treatment with recombinant CPE-protein. Our approach aimed at evaluation of a selective and targeted cancer gene therapy of claudin-3- and/or claudin-4- expressing colon carcinoma in vitro and in vivo by using translation optimized CPE expressing vector.
METHODS: In this study the recombinant CPE and a translation optimized CPE expressing vector (optCPE) was used for targeted gene therapy of claudin-3 and/or -4 overexpressing colon cancer cell lines. All experiments were performed in the human SW480, SW620, HCT116, CaCo-2 and HT-29 colon cancer and the isogenic Sk-Mel5 and Sk-Mel5 Cldn-3-YFP melanoma cell lines. Claudin expression analysis was done at protein and mRNA level, which was confirmed by immunohistochemistry. The CPE induced cytotoxicity was analyzed by the MTT cytotoxicity assay. In addition patient derived colon carcinoma xenografts (PDX) were characterized and used for the intratumoral in vivo gene transfer of the optCPE expressing vector in PDX bearing nude mice.
RESULTS: Claudin-3 and -4 overexpressing colon carcinoma lines showed high sensitivity towards both recCPE application and optCPE gene transfer. The positive correlation between CPE cytotoxicity and level of claudin expression was demonstrated. Transfection of optCPE led to targeted, rapid cytotoxic effects such as membrane disruption and necrosis in claudin overexpressing cells. The intratumoral optCPE in vivo gene transfer led to tumor growth inhibition in colon carcinoma PDX bearing mice in association with massive necrosis due to the intratumoral optCPE expression.
CONCLUSIONS: This novel approach demonstrates that optCPE gene transfer represents a promising and efficient therapeutic option for a targeted suicide gene therapy of claudin-3 and/or claudin-4 overexpressing colon carcinomas, leading to rapid and effective tumor cell killing in vitro and in vivo.
Moldvay J, Fábián K, Jäckel M, et al.Claudin-1 Protein Expression Is a Good Prognostic Factor in Non-Small Cell Lung Cancer, but only in Squamous Cell Carcinoma Cases.
Pathol Oncol Res. 2017; 23(1):151-156 [PubMed
] Related Publications
The aim of the study was to investigate the correlation between claudin (CLDN) protein expression and clinicopathological parameters as well as survival in histological subtypes of non-small cell lung cancer. Archived surgical resection specimens of 137 pathologic stage I primary bronchial cancers including 49 adenocarcinomas of non-lepidic variants (ADC), 46 adenocarcinomas of lepidic variants (L-ADC), and 42 squamous cell carcinomas (SCC) were examined. Immunohistochemistry (IHC) using antibodies against CLDN1,-2,-3,-4,-7 proteins as well as semiquantitative estimation (IHC scores 0-5) were performed. Claudin IHC scores of L-ADC differed significantly from ADC (CLDN1: p = 0.009, CLDN2: p = 0.005, CLDN3: p = 0.004, CLDN4: p = 0.001, CLDN7: p < 0.001, respectively) and SCC (CLDN1: p < 0.001, CLDN3: p < 0.001, CLDN7: p < 0.001, respectively). Highly significant CLDN3-CLDN4 parallel expression could be demonstrated in ADC and L-ADC (p < 0.001 in both), which was not observed in SCC (p = 0.131). ADC and SCC showed no correlation with smoking, whereas in case of L-ADC heavier smoking correlated with higher CLDN3 expression (p = 0.020). Regarding claudin expression and survival, in SCC significant correlation could be demonstrated between CLDN1 IHC positivity and better survival (p = 0.038). In NSCLC as a whole, high CLDN2 expression proved to be a better prognostic factor when compared with cases where CLDN2 IHC score was 0-1 vs. 2-5 (p = 0.009), however, when analyzed separately, none of the histological subgroups showed correlation between CLDN2 expression and overall survival. The claudin expression pattern was significantly different not only between the SCC-ADC and SCC-L-ADC but also between the L-ADC and ADC histological subgroups, which strongly underlines that L-ADC represents a distinct entity within the ADC group. CLDN1 overexpression is a good prognostic factor in NSCLC, but only in the SCC subgroup.
Gabig TG, Waltzer WC, Whyard T, Romanov VClostridium perfringens enterotoxin as a potential drug for intravesical treatment of bladder cancer.
Biochem Biophys Res Commun. 2016; 478(2):887-92 [PubMed
] Related Publications
The current intravesical treatment of bladder cancer (BC) is limited to a few chemotherapeutics that show imperfect effectiveness and are associated with some serious complications. Thus, there is an urgent need for alternative therapies, especially for patients with high-risk non-muscle invasive (NMIBC). Clostridium perfringens enterotoxin (CPE), cytolytic protein binds to its receptors: claudin 3 and 4 that are expressed in epithelial cells. This binding is followed by rapid cell death. Claudin 4 is present in several epithelial tissue including bladder urothelium and its expression is elevated in some forms of BC. In addition to directly targeting BC cells, binding of CPE to claudins increases urothelium permeability that creates conditions for better accession of the tumor. Therefore, we evaluated CPE as a candidate for intravesical treatment of BC using a cellular model. We examined cytotoxicity of CPE against BC cells lines and 3D cultures of cells derived from surgical samples. To better elucidate cellular mechanisms, activated by CPE and to consider the use of CPE non-toxic fragment (C-CPE) for combination treatment with other drugs we synthesized C-CPE, compared its cytotoxic activity with CPE and examined claudin 4 expression and intracellular localization after C-CPE treatment. CPE induced cell death after 1 h in low aggressive RT4 cells, in moderately aggressive 5637 cells and in the primary 3D cultures of BC cells derived from NMIBC. Conversely, non-transformed urothelial cells and cells derived from highly aggressive tumor (T24) survived this treatment. The reason for this resistance to CPE might be the lower expression of CLDNs or their inaccessibility for CPE in these cells. C-CPE treatment for 48 h did not affect cell viability in tested cells, but declined expression of CLDN4 in RT4 cells. C-CPE increased sensitivity of RT4 cells to Mitommycin C and Dasatinib. To better understand mechanisms of this effect we examined expression and phosphorylation status of EphA2 and Src after C-CPE treatment and found changes in expression and phosphorylated status of these regulatory molecules. These observations show that after additional preclinical studies CPE and C-CPE in combinations with other drugs can be considered as a potential modalities for intravesical treatment of BC because of its ability to effectively destroy BC cells expressing claudin 4 and low toxicity against normal urothelium.
Wahdan-Alaswad R, Harrell JC, Fan Z, et al.Metformin attenuates transforming growth factor beta (TGF-β) mediated oncogenesis in mesenchymal stem-like/claudin-low triple negative breast cancer.
Cell Cycle. 2016; 15(8):1046-59 [PubMed
] Free Access to Full Article Related Publications
Mesenchymal stem-like/claudin-low (MSL/CL) breast cancers are highly aggressive, express low cell-cell adhesion cluster containing claudins (CLDN3/CLDN4/CLDN7) with enrichment of epithelial-to-mesenchymal transition (EMT), immunomodulatory, and transforming growth factor-β (TGF-β) genes. We examined the biological, molecular and prognostic impact of TGF-β upregulation and/or inhibition using in vivo and in vitro methods. Using publically available breast cancer gene expression databases, we show that upregulation and enrichment of a TGF-β gene signature is most frequent in MSL/CL breast cancers and is associated with a worse outcome. Using several MSL/CL breast cancer cell lines, we show that TGF-β elicits significant increases in cellular proliferation, migration, invasion, and motility, whereas these effects can be abrogated by a specific inhibitor against TGF-β receptor I and the anti-diabetic agent metformin, alone or in combination. Prior reports from our lab show that TNBC is exquisitely sensitive to metformin treatment. Mechanistically, metformin blocks endogenous activation of Smad2 and Smad3 and dampens TGF-β-mediated activation of Smad2, Smad3, and ID1 both at the transcriptional and translational level. We report the use of ID1 and ID3 as clinical surrogate markers, where high expression of these TGF-β target genes was correlated to poor prognosis in claudin-low patients. Given TGF-β's role in tumorigenesis and immunomodulation, blockade of this pathway using direct kinase inhibitors or more broadly acting inhibitors may dampen or abolish pro-carcinogenic and metastatic signaling in patients with MCL/CL TNBC. Metformin therapy (with or without other agents) may be a heretofore unrecognized approach to reduce the oncogenic activities associated with TGF-β mediated oncogenesis.
Madaras L, Balint N, Gyorffy B, et al.BRCA Mutation-Related and Claudin-Low Breast Cancer: Blood Relatives or Stepsisters.
Pathobiology. 2016; 83(1):1-12 [PubMed
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BACKGROUND: BRCA mutation-associated (BRCAmut) breast cancer represents a heterogeneous group displaying certain molecular features. Claudin-low breast cancers (CLBC) overlap with characteristics of BRCAmut tumors; therefore, we have investigated whether these are identical subtypes.
METHODS: Using public gene expression data, CLDN, CDH1, 9-cell line claudin-low predictor (9CLCLP) and PAM50 expression was evaluated in BRCAmut and BRCA wild-type (BRCAwt) breast cancer cases focusing on their possible overlap with the CLBC subtype. A separate formalin-fixed, paraffin-embedded (FFPE) cohort of 22 BRCAmut and 19 BRCAwt tumor tissues was used for immunohistochemical examination of AR, CD24, CD44, CK5/6, claudin-1, -3, -4 and -7, E-cadherin, EGFR, estrogen receptor (ER), EZH2, HER2, Ki67, p53, progesterone receptor (PgR) and vimentin expression.
RESULTS: In the data sets, CLDN1 (ROC = 0.785, p < 0.001), CDH1 (ROC = 0.785, p < 0.001), CLDN7 (ROC = 0.723, p < 0.001), CLDN3 (ROC = 0.696, p = 0.020) and CLDN4 (ROC = 0.685, p = 0.027) were expressed at higher level in BRCAmut than BRCAwt tumor tissue. The PAM50 subtype differed from the assigned immunohistochemistry (IHC)-based subtype in 30%. Based on accessible 9CLCLP predictor genes, BRCAmut breast cancer does not display the claudin-low phenotype. Utilizing FFPE samples, claudins were evidently expressed in both BRCAmut and BRCAwt cases. However, at the protein level, only claudin-3 expression was higher in BRCAmut tumors, while claudin-1, -4 and -7 and E-cadherin expression was lower compared to BRCAwt cases. A CD24low/CD44high phenotype was found in BRCAmut tumors upon comparison with BRCAwt cases (p < 0.001 and p = 0.001, respectively).
CONCLUSIONS: There is a prominent correlation between the genes under focus herein and BRCA mutation status. BRCAmut tumors bear stem cell characteristics displaying a distinct cell adhesion molecule profile characterized by high expression of CDH1 and CLDN4 according to public gene expression data set analysis, and higher claudin-3 expression as detected by IHC; thus, BRCAmut breast carcinomas are not identical with the previously identified claudin-low subtype of breast cancer.
Hatta M, Naganuma K, Kato K, Yamazaki J3-Deazaneplanocin A suppresses aggressive phenotype-related gene expression in an oral squamous cell carcinoma cell line.
Biochem Biophys Res Commun. 2015 Dec 4-11; 468(1-2):269-73 [PubMed
] Related Publications
In tumor tissues, alterations of gene expression caused by aberrant epigenetic modifications confer phenotypic diversity on malignant cells. Although 3-deazaneplanocin A (DZNep) has been shown to reactivate tumor suppressor genes in several cancer cells, it remains unclear whether DZNep attenuates the malignant phenotypes of oral squamous cell carcinoma (OSCC) cells. In this study, we investigated the effect of DZNep on the expression of genes related to aggressive phenotypes, such as epithelial-mesenchymal transition, in OSCC cells. We found that DZNep reduced the cellular levels of polycomb group proteins (EZH2, SUZ12, BMI1, and RING1A) and the associated trimethylation of Lys27 on histone H3 and monoubiquitination of Lys119 on histone H2A in the poorly differentiated OSCC cell line SAS. Immunocytochemical staining demonstrated that DZNep induced the reorganization of filamentous actin and the membrane localization of E-cadherin associated with cell-cell adhesions. We also found an inhibitory effect of DZNep on cell proliferation using a WST assay. Finally, quantitative RT-PCR analysis demonstrated that genes involved in the aggressive phenotypes (TWIST2, EGFR, ACTA2, TGFB1, WNT5B, and APLIN) were down-regulated, whereas epithelial phenotype genes (CDH1, CLDN4, IVL, and TGM1) were up-regulated in SAS cells treated with DZNep. Collectively, our findings suggest that DZNep reverses the aggressive characteristics of OSCC cells through the dynamic regulation of epithelial plasticity via the reprogramming of gene expression patterns.
DE Vicente JC, Fernández-Valle Á, Vivanco-Allende B, et al.The prognostic role of claudins -1 and -4 in oral squamous cell carcinoma.
Anticancer Res. 2015; 35(5):2949-59 [PubMed
] Related Publications
Claudin dysregulation has been described in various tumor types; however, its clinical relevance is poorly understood. We present a study in which we assessed the expression of claudin 1 (CLDN1) and CLDN4 in oral squamous cell carcinoma (OSCC), as well as their prognostic relevance. Immunohistochemical analysis of CLDN1 and CLDN4 expression was carried out on tissue sections from 65 OSCCs. The presence of CLDN1 in the invasive front of tumor islands was associated with neck node metastasis, and the expression of CLDN4 was associated with higher histological grade, and tumor recurrence. Membranous staining for CLDN4 in tumor cells, and weak intensity of CLDN4 immunoexpression were predictive for poorer survival. In a multivariate analysis for disease recurrence, CLDN1 immunostaining was statistically significant. Specifically, CDLN1 expression in the tumor invasive front was associated with tumor recurrence. Our results indicate that CLDN4 expression is correlated with poor prognosis, and CLDN1 expression may be an indicator of recurrence of OSCC.
Yang Y, Cheon S, Jung MK, et al.Interleukin-18 enhances breast cancer cell migration via down-regulation of claudin-12 and induction of the p38 MAPK pathway.
Biochem Biophys Res Commun. 2015; 459(3):379-86 [PubMed
] Related Publications
Interleukin-18 (IL-18) was recently reported to have a pro-tumor effect in various cancers. Increased IL-18 levels in the serum of cancer patients correlated with malignancy, and IL-18 acts a crucial factor for cell migration in gastric cancer and melanoma. Claudins, which are the most important tight junction proteins, are also linked with cancer progression and metastasis. However, the relationship between claudins and IL-18 is not well-understood. Here, we show that the migratory ability of MCF-7 cells was reduced when endogenous IL-18 expression was inhibited with IL-18 siRNA. Moreover, exogenous IL-18 enhanced breast cancer cell migration and suppressed the expression of the tight junction proteins claudin-1, claudin-3, claudin-4, and claudin-12 in MCF-7 cells. Knockdown of claudin-3, claudin-4, and claudin-12, but not claudin-1, increased breast cancer migration with maximal effects observed in claudin-12 siRNA-transfected cells. To investigate whether the mitogen-activated protein kinase (MAPK) signaling pathway is involved in IL-18-induced cell migration and claudin-12 expression, cells were pretreated with SB203580 (an inhibitor of p38 MAPK) or PD98059 (an inhibitor of ERK1/2) prior to the addition of IL-18. Although pretreatment of MCF-7 cells with SB203580 blocked both the enhanced cell migration and the decreased claudin-12 expression, PD98059 only blocked cell migration and did not affect claudin-12 expression. In addition, exogenous IL-18 induced rapid phosphorylation of p38 MAPK. These results suggest that IL-18 is an important factor inducing breast cancer cell migration through down-regulation of claudin-12 and activation of the p38 MAPK pathway.
INTRODUCTION: Triple-negative breast cancer (TNBC) is a heterogeneous disease with no definitive prognostic markers. As a major component of tight junctions, claudins (CLDNs) presumably play an important role in carcinogenesis and progression of breast cancer. This study was aimed at determining the relationship between the expression of CLDNs and the clinical outcomes of TNBCs.
MATERIALS AND METHODS: The surgical specimens of primary breast tumors from a consecutive cohort of 173 TNBC patients were retrospectively collected. The membranous expression of CLDN1, CLDN2, CLDN4, and CLDN7 was measured by immunohistochemistry. Then, the associations between CLDN expression, clinicopathological features, and clinical outcomes were assessed.
RESULTS: Positive CLDN1, CLDN2, CLDN4, and CLDN7 membrane expression was detected in 44.5%, 54.9%, 76.9%, and 73.4% of the cohort specimens, respectively. A lack of CLDN1 expression was related to only lymph node metastasis (P = 0.014). The rate of CLDN4-positive tumors was significantly increased in tumors of a higher grade (P = 0.003). Importantly, negative CLDN1 expression was associated with worse relapse-free survival (RFS) in both lymph node positive (LN+) and negative (LN-) cases (both P<0.001). Similarly it was also associated with shorter overall survival (OS)(P = 0.003 in LN+ cases; P = 0.018 in LN- cases). In the LN+ subgroup, CLDN2-negative cases had a significantly higher risk of recurrence (P = 0.008). Multivariate analysis revealed that negative CLDN1 expression was an independent prognostic factor for high risk of both recurrence and death (HR 5.529, 95% CI 2.664-11.475, P<0.001; HR 3.459, 95% CI 1.555-7.696, P = 0.002). However, neither CLDN4 nor CLDN7 expression was associated with survival.
CONCLUSION: In TNBC, the CLDN1-negative phenotype predicts a high risk of recurrence and death. The absence of CLDN1 expression is strongly suggested to be an independent adverse prognostic factor in this heterogeneous subtype of breast cancer.
Al Sawah E, Marchion DC, Xiong Y, et al.The Chinese herb polyphyllin D sensitizes ovarian cancer cells to cisplatin-induced growth arrest.
J Cancer Res Clin Oncol. 2015; 141(2):237-42 [PubMed
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PURPOSE: We evaluated the effects of polyphyllin D (PD), a natural compound with anti-neoplastic activity and a major component of the Chinese herb Paris polyphylla, on ovarian cancer (OVCA) cell line proliferation and platinum sensitivity.
METHODS: A panel of 20 OVCA cell lines was subjected to PD treatment, MTS proliferation assays, and determination of IC50. Pre-treatment, baseline genome-wide Affymetrix expression analysis was performed on each cell line, and Pearson's correlation was performed to identify genes associated with OVCA PD sensitivity. Twelve cell lines were treated with PD with and without cisplatin, and the effects of PD on cisplatin IC50 were quantified. Genes associated with OVCA PD sensitivity were evaluated for associations with survival in a publically available clinico-genomic dataset of 218 patients with OVCA.
RESULTS: Our results showed that PD exhibited anti-proliferative effects against all OVCA cell lines tested, with IC50 values ranging from 0.2 to 1.4 μm. Furthermore, in all cell lines, PD treatment significantly decreased cisplatin IC50 (mean IC50 reduction of 2.1 µm; P < 0.02). Pearson's correlation test identified 25 probe sets, representing 18 unique genes to be associated with PD sensitivity (FDR = 0). We found that one of these genes was associated with overall survival in women with OVCA: CLDN4 (P = 0.014).
CONCLUSION: Our findings highlight the value of PD as a natural product with anti-cancer properties, which may also enhance the activity of existing therapeutic agents.
Liszka LDuctal adenocarcinoma of the pancreas usually retained SMAD4 and p53 protein status as well as expression of epithelial-to-mesenchymal transition markers and cell cycle regulators at the stage of liver metastasis.
Pol J Pathol. 2014; 65(2):100-12 [PubMed
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There are limited data on the biology of metastatic pancreatic ductal adenocarcinoma (PDAC). The aim of the present study was to compare the expression of immunohistochemical markers that may be involved in the development of metastatic disease in primary PDAC and in synchronous liver metastatic tissues. Thirty-two stains (corresponding to proteins encoded by 31 genes: SMAD4, TP53, ACTA2, CDH1, CDKN1A, CLDN1, CLDN4, CLDN7, CTNNB1, EGFR, ERBB2, FN1, KRT19, MAPK1/MAPK3, MAPK14, MKI67, MMP2, MMP9, MUC1 (3 antibodies), MUC5AC, MUC6, MTOR, MYC, NES, PTGS2, RPS6, RPS6KB1, TGFB1, TGFBR1, VIM) were evaluated using tissue microarray of 26 pairs of primary PDACs and their liver metastases. There were no significant differences in expression levels of examined proteins between primary and secondary lesions. In particular, metastatic PDAC retained the primary tumour's SMAD4 protein status in all and p53 protein status in all but one case. This surprising homogeneity also involved expression levels of markers of epithelial-to-mesenchymal transition as well as cell cycle regulators studied. In conclusion, the biological profiles of primary PDACs and their liver metastases seemed to be similar. Molecular alterations of PDAC related to a set of immunohistochemical markers examined in the present study were already present at the stage of localized disease.
Cholangiocarcinoma (CCA) is the second most common-primary liver cancer. The difficulties in diagnosis limit successful treatment of CCA. At present, histological investigation is the standard diagnosis for CCA. However, there are some poor-defined tumor tissues which cannot be definitively diagnosed by general histopathology. As molecular signatures can define molecular phenotypes related to diagnosis, prognosis, or treatment outcome, and CCA is the second most common cancer found after hepatocellularcarcinoma (HCC), the aim of this study was to develop a predictive model which differentiates CCA from HCC and normal liver tissues. An in-house PCR array containing 176 putative CCA marker genes was tested with the training set tissues of 20 CCA and 10 HCC cases. The molecular signature of CCA revealed the prominent expression of genes involved in cell adhesion and cell movement, whereas HCC showed elevated expression of genes related to cell proliferation/differentiation and metabolisms. A total of 69 genes differentially expressed in CCA and HCC were optimized statistically to formulate a diagnostic equation which distinguished CCA cases from HCC cases. Finally, a four-gene diagnostic equation (CLDN4, HOXB7, TMSB4 and TTR) was formulated and then successfully validated using real-time PCR in an independent testing set of 68 CCA samples and 77 non-CCA controls. Discrimination analysis showed that a combination of these genes could be used as a diagnostic marker for CCA with better diagnostic parameters with high sensitivity and specificity than using a single gene marker or the usual serum markers (CA19-9 and CEA). This new combination marker may help physicians to identify CCA in liver tissues when the histopathology is uncertain.
Abd El-Ghani SF, Kasem RF, Ghallab NA, Shaker OGDetection of claudin-4 in salivary gland neoplasms (a study utilizing RT-PCR and immunohistochemistry).
J Oral Pathol Med. 2013; 42(10):781-7 [PubMed
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BACKGROUND: Claudins are transmembrane proteins of tight junctions emerging as targets for diagnosis, prediction of prognosis, disease recurrence, and metastasis. Our goal was to evaluate expression of claudin-4 in the most common benign and malignant salivary gland neoplasms.
METHODS: Claudin-4 gene levels and protein expression were determined by real-time polymerase chain reaction (PCR), and immunohistochemistry in a total of 30 specimens containing normal salivary tissue, pleomorphic adenoma, Warthin's tumor, mucoepidermoid carcinoma, and adenoid cystic carcinoma.
RESULTS: We identified down-regulation of claudin-4 gene levels and protein expression from normal control to benign salivary gland neoplasms and reached their lowest values in the malignant salivary gland neoplasms.
CONCLUSIONS: Low claudin-4 expression could be considered as a sign of increasing cellular disorientation and invasion of salivary gland tumors.
Siar CH, Abbas SAClaudin expression and tight junction protein localization in the lining epithelium of the keratocystic odontogenic tumors, dentigerous cysts, and radicular cysts.
Oral Surg Oral Med Oral Pathol Oral Radiol. 2013; 115(5):652-9 [PubMed
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OBJECTIVE: The aim of this study was to evaluate the expression and localization of tight junction proteins (TJPs) or claudins in the keratocystic odontogenic tumor (KCOT) and to correlate with its biological behavior.
STUDY DESIGN: Five claudins (-1, -3, -4, -5, and 7) were examined immunohistochemically in 25 KCOTs and compared with 10 dentigerous cysts (DCs) and 10 radicular cysts (RCs).
RESULTS: Marked claudin-3 loss of expression in KCOT basal layer (n=24/25; 96%) compared with DCs (n=1/10; 10%) and RCs (n=5/10; 50%) (P<.05) suggests that claudin-3 downregulation may indicate altered or loss of basal cell polarity and impaired barrier function of KCOT lining epithelium and this might contribute indirectly to its biological behavior. In contrast, claudins-1, -4, -5, and -7 distribution patterns were less distinctive in all three entities, suggesting that these TJP molecules probably play limited roles in influencing their different growth potentials.
CONCLUSION: Present findings suggest that differential claudin expressions in the lining epithelium of KCOTs, DCs, and RCs probably reflect their neoplastic or nonneoplastic nature.
Hashimi SM, Yu S, Alqurashi N, et al.Immunotoxin-mediated targeting of claudin-4 inhibits the proliferation of cancer cells.
Int J Oncol. 2013; 42(6):1911-8 [PubMed
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Immunotoxins are engineered chimeric proteins that consist of a fragment of a toxin fused to a modified antibody or growth factor capable of targeting specific cells. Furthermore, these proteins can be targeted to receptors that are commonly overexpressed on cancer cells. The majority of immunotoxins function by binding to cells, translocating into the cytosol and inhibiting protein synthesis. In this study, the expression of claudin‑4 (CLDN4) in various cancer cells was analysed as a potential target for immunotoxins. To target CLDN4-expressing cancer cells, the c-terminal CLDN4‑binding domain of Clostridium perfringens enterotoxin (CPE) was fused to the Pseudomonas aeruginosa exotoxin A (ETA) domain to create an immunotoxin (CPE‑ETA'). Subsequently, the capacity of such an immunotoxin in suppressing the proliferation of CLDN4-positive cancer cells was investigated. We report that head and neck squamous carcinoma cells (HN5) have an elevated CLDN4 expression compared to the other cell lines tested. Our findings further demonstrate that CPE‑ETA' is highly potent against MCF-7 breast [50% inhibitory concentration (IC50) 9.8 ng/ml] and HN5 head/neck (IC50 8.8 ng/ml) cancer cell lines, while it has no cytotoxic effects on HeLa cells (CLDN4‑negative). The immunotoxin was subsequently expressed in the tumour colonising oncolytic strain, Clostridium ghonii. Most importantly, the strictly anaerobic Clostridium ghonii was able to overexpress and secrete a functional CPE‑ETA' fusion protein. Our findings open the possibility of the targeted delivery of the immunotoxin locally to tumour sites at a high concentration using strictly anaerobic Clostridium ghonii for the treatment of CLDN4-positive cancer cells.
Nordfors K, Haapasalo J, Sallinen PK, et al.Expression of claudins relates to tumour aggressivity, location and recurrence in ependymomas.
Histol Histopathol. 2013; 28(9):1137-46 [PubMed
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The aim of our study was to assess the nature and importance of claudin expression in grade I-III ependymomas. The expression of claudins 2-5, 7, 10, TWIST, and ZEB1 were investigated in a series of 61 ependymomas using immunohistochemistry. All the claudins were expressed in ependymomas, except for CLDN4. CLDN5 positive tumours were associated with higher grade (p=0.049), whereas CLDN10 was lower in higher grade tumours (p=0.039). CLDN5 and CLDN3 were overexpressed in ependymomas of cerebral location (p=0.036, p=0.007, respectively). CLDN5 positive tumours showed more nuclear atypia, endothelial proliferation, mitosis, and hypercellularity (p=0.007, p=0.018, p=0.041, p=0.010, respectively). CLDN5 positivity correlated to higher proliferation (p=0.015). CLDN7 was more often positive in primary tumours (p=0.041). Positive ZEB1 expression was associated with CLDN2 negativity (p=0.031). TWIST-negative tumours were more often also CLDN5 and 10 negative (p=0.013, p=0.017, respectively). CLDN5 was related to more aggressive tumours compared to CLDN2 and 10, which tended to display a better degree of differentiation and a better prognosis. CLDN2 and CLDN5 were expressed commonly in ependymomas, while the parental ependymal cells in the central nervous system were usually negative. Evidently, claudins influence growth and differentiation in ependymomas.
The extent of tight junction (TJ) formation is one of many factors that regulate motility, invasion, and metastasis. Claudins are required for the formation and maintenance of TJs. Claudin-3 (CLDN3) and claudin-4 (CLDN4) are highly expressed in the majority of ovarian cancers. We report here that CLDN3 and CLDN4 each serve to constrain the growth of human 2008 cancer xenografts and limit metastatic potential. Knockdown of CLDN3 increased in vivo growth rate by 2.3-fold and knockdown of CLDN4 by 3.7-fold in the absence of significant change in in vitro growth rate. Both types of tumors exhibited increase in birth rate as measured by Ki67 staining and decrease in death rate as reflected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Knockdown of either claudin did not alter expression of other TJ protein but did reduce TJ formation as measured by transepithelial resistance and paracellular flux of dextran, enhance migration and invasion in in vitro assays, and increase lung colonization following intravenous injection. Knockdown of CLDN3 and CLDN4 increased total lung metastatic burden by 1.7-fold and 2.4-fold, respectively. Loss of either CLDN3 or CLDN4 resulted in down-regulation of E-cadherin mRNA and protein, increased inhibitory phosphorylation of glycogen synthase kinase-3β (GSK-3β), and activation of β-catenin pathway signaling as evidenced by increases in nuclear β-catenin, the dephosphorylated form of the protein, and transcriptional activity of β-catenin/T-cell factor (TCF). We conclude that both CLDN3 and CLDN4 mediate interactions with other cells in vivo that restrain growth and metastatic potential by sustaining expression of E-cadherin and limiting β-catenin signaling.
Xiao-Yu P, Yan J, Cui-Ping F, et al.Altered claudin-4 expression in progesterone-treated endometrial adenocarcinoma cell line Ishikawa.
Int J Gynecol Cancer. 2012; 22(9):1585-90 [PubMed
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OBJECTIVE: To detect the expression change of claudin-4 in Ishikawa endometrial adenocarcinoma cell line in response to progesterone. To determine whether claudin-4 is involved in the anticancer effect of progesterone.
METHODS: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to determine the 50% inhibitory concentration (IC50) of megestrol acetate (MA) in treating Ishikawa cells. After the Ishikawa cells were treated with MA at IC50, cell apoptosis was examined by flow cytometry and transmission electron microscopy. The messenger RNA and protein expression levels of claudin-4 were further quantified by real-time polymerase chain reaction and Western blot. The localization of claudin-4 was examined by immunofluorescent staining.
RESULTS: The IC50 of MA on Ishikawa cells was 15 mg/L incubated for 72 hours. Apoptosis percentage was elevated from 0.07% ± 0.02% to 3.93% ± 0.81% after MA treatment. The expression of claudin-4 at both protein and messenger RNA levels was significantly decreased after the treatment of MA (P < 0.05). The localization of claudin-4 transferred from cytomembrane to cytoplasm and nucleus.
CONCLUSION: Megestrol acetate can inhibit the growth of Ishikawa cells. It may work through decreasing claudin-4 expression and cell apoptosis. The localization change of claudin-4 may also be involved in the anticancer effect of progesterone.
Shang X, Lin X, Manorek G, Howell SBClaudin-3 and claudin-4 regulate sensitivity to cisplatin by controlling expression of the copper and cisplatin influx transporter CTR1.
Mol Pharmacol. 2013; 83(1):85-94 [PubMed
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Claudin-3 (CLDN3) and claudin-4 (CLDN4) are the major structural molecules that form tight junctions (TJs) between epithelial cells. We found that knockdown of the expression of either CLDN3 or CLDN4 produced marked changes in the phenotype of ovarian cancer cells, including an increase in resistance to cisplatin (cDDP). The effect of CLND3 and CLDN4 on cDDP cytotoxicity, cDDP cellular accumulation, and DNA adduct formation was compared in the CLDN3- and CLDN4-expressing parental human ovarian carcinoma 2008 cells and CLDN3 and CLDN4 knockdown sublines (CLDN3KD and CLDN4KD, respectively). Knockdown of CLDN3 or CLDN4 rendered human ovarian carcinoma 2008 cells resistant to cDDP in both in vitro culture and in vivo xenograft model. The net accumulation of platinum (Pt) and the Pt-DNA adduct levels were reduced in CLDN3KD and CLDN4KD cells. The endogenous mRNA levels of copper influx transporter CTR1 were found to be significantly reduced in the knockdown cells, and exogenous expression of CTR1 restored their sensitivity to cDDP. Reexpression of an shRNAi-resistant CLDN3 or CLDN4 up-regulated CTR1 levels, reversed the cDDP resistance, and enhanced TJ formation in the knockdown cells. Baseline copper (Cu) level, Cu uptake, and Cu cytotoxicity were also reduced in CLDN3KD and CLDN4KD cells. Cu-dependent tyrosinase activity was also markedly reduced in both types of CLDN knockdown cells when incubated with the substrate l-DOPA. These results indicate that CLDN3 and CLDN4 affect sensitivity of the ovarian cancer cells to the cytotoxic effect of cDDP by regulating expression of the Cu transporter CTR1.
Ricardo S, Gerhard R, Cameselle-Teijeiro JF, et al.Claudin expression in breast cancer: high or low, what to expect?
Histol Histopathol. 2012; 27(10):1283-95 [PubMed
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The evaluation of claudins (CLDNs) expression pattern in tumours can be important to understand breast carcinogenesis. The study of CLDNs became more appealing since it was found that CLDN3 and CLDN4 are putative therapeutic targets for Clostridium perfrigens enterotoxin (CPE), as well as for monoclonal antibody-based therapy. Moreover, the recently characterized CLDN-low molecular subgroup of breast tumours increased the interest in these molecules. Based on these facts, our aim was to explore the pattern of expression of CLDNs among a large series of invasive breast carcinomas. We also analysed the correlation between the combinatorial expression of CLDN3/CLDN4 and classical prognostic factors and biological markers. In addition, we also compared the characteristics of tumours with low expression of CLDN3, CLDN4 and CLDN7, assessed by immunohistochemistry (IHC), and the ones from CLDN-low subgroup of tumours previously defined by genomic assays. The combinatorial analysis of the expression of CLDN3/CLDN4 showed a significant association between high CLDN3/CLDN4 levels and triple-negative tumours, as well as with worse patient outcome. This combined analysis may provide useful information for breast carcinomas, since these two CLDN members are putative therapeutic targets. Comparing tumours with low expression of CLDN3, CLDN4 and CLDN7 with tumours previously referred to as CLDN-low by genomic assays, we demonstrated that the single IHC evaluation of these three specific CLDNs is insufficient to identify the CLDN-low molecular subtype of breast tumours. The analysis of several other molecular markers, such as EMT (epithelial-to-mesenchymal transition) and CSC (cancer stem cell) markers should probably be added to improve the identification of this subgroup of tumours by IHC, which probably are enriched in carcinomas with metaplastic differentiation.