Gene Summary

Gene:RBL1; RB transcriptional corepressor like 1
Aliases: PRB1, p107, CP107
Summary:The protein encoded by this gene is similar in sequence and possibly function to the product of the retinoblastoma 1 (RB1) gene. The RB1 gene product is a tumor suppressor protein that appears to be involved in cell cycle regulation, as it is phosphorylated in the S to M phase transition and is dephosphorylated in the G1 phase of the cell cycle. Both the RB1 protein and the product of this gene can form a complex with adenovirus E1A protein and SV40 large T-antigen, with the SV40 large T-antigen binding only to the unphosphorylated form of each protein. In addition, both proteins can inhibit the transcription of cell cycle genes containing E2F binding sites in their promoters. Due to the sequence and biochemical similarities with the RB1 protein, it is thought that the protein encoded by this gene may also be a tumor suppressor. Two transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Jul 2008]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:retinoblastoma-like protein 1
Source:NCBIAccessed: 29 August, 2019


What does this gene/protein do?
Show (17)
Pathways:What pathways are this gene/protein implicaed in?
Show (4)

Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 29 August 2019 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Prostate Cancer
  • Transcription
  • Proteins
  • Nuclear Proteins
  • Tumor Suppressor Gene
  • Messenger RNA
  • Retinoblastoma-Like Protein p130
  • Cancer DNA
  • Urinary Tract
  • Knockout Mice
  • Mutation
  • Phosphoproteins
  • Promoter Regions
  • Neoplasm Proteins
  • Chromosome 20
  • DNA Methylation
  • RB1
  • Papillomavirus Infections
  • Epigenetics
  • Cancer Gene Expression Regulation
  • E2F Transcription Factors
  • Base Sequence
  • RBL1
  • Signal Transduction
  • Cell Proliferation
  • Cell Cycle Proteins
  • Viral Core Proteins
  • Genes, Retinoblastoma
  • Xenograft Models
  • Neoplastic Cell Transformation
  • Cell Differentiation
  • Cell Cycle
  • Retinoblastoma
  • Protein Binding
  • Phosphorylation
  • DNA-Binding Proteins
  • Apoptosis
  • MicroRNAs
  • Transcription Factors
  • p53 Protein
  • Cervical Cancer
Tag cloud generated 29 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (2)

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).

Latest Publications: RBL1 (cancer-related)

Starrett GJ, Serebrenik AA, Roelofs PA, et al.
Polyomavirus T Antigen Induces
MBio. 2019; 10(1) [PubMed] Free Access to Full Article Related Publications
APOBEC3B is a single-stranded DNA cytosine deaminase with beneficial innate antiviral functions. However, misregulated APOBEC3B can also be detrimental by inflicting APOBEC signature C-to-T and C-to-G mutations in genomic DNA of multiple cancer types. Polyomavirus and papillomavirus oncoproteins induce APOBEC3B overexpression, perhaps to their own benefit, but little is known about the cellular mechanisms hijacked by these viruses to do so. Here we investigate the molecular mechanism of APOBEC3B upregulation by the polyomavirus large T antigen. First, we demonstrate that the upregulated APOBEC3B enzyme is strongly nuclear and partially localized to virus replication centers. Second, truncated T antigen (truncT) is sufficient for APOBEC3B upregulation, and the RB-interacting motif (LXCXE), but not the p53-binding domain, is required. Third, genetic knockdown of RB1 alone or in combination with RBL1 and/or RBL2 is insufficient to suppress truncT-mediated induction of

Gillison ML, Akagi K, Xiao W, et al.
Human papillomavirus and the landscape of secondary genetic alterations in oral cancers.
Genome Res. 2019; 29(1):1-17 [PubMed] Free Access to Full Article Related Publications
Human papillomavirus (HPV) is a necessary but insufficient cause of a subset of oral squamous cell carcinomas (OSCCs) that is increasing markedly in frequency. To identify contributory, secondary genetic alterations in these cancers, we used comprehensive genomics methods to compare 149 HPV-positive and 335 HPV-negative OSCC tumor/normal pairs. Different behavioral risk factors underlying the two OSCC types were reflected in distinctive genomic mutational signatures. In HPV-positive OSCCs, the signatures of APOBEC cytosine deaminase editing, associated with anti-viral immunity, were strongly linked to overall mutational burden. In contrast, in HPV-negative OSCCs, T>C substitutions in the sequence context 5'-ATN-3' correlated with tobacco exposure. Universal expression of HPV

Szurián K, Csala I, Marosvári D, et al.
EZH2 is upregulated in the proliferation centers of CLL/SLL lymph nodes.
Exp Mol Pathol. 2018; 105(2):161-165 [PubMed] Related Publications
Lymph node involvement of chronic lymphocytic leukaemia/small lymphocytic lymphoma (CLL/SLL) is characterised by the diffuse infiltration of small neoplastic lymphocytes, which is accompanied by the presence of proliferation centres (PCs) comprising prolymphocytes and paraimmunoblasts. There is increasing evidence of accumulation of various molecular alterations in the tumour cells of PCs, which may explain why extended PCs are related to a less favourable prognosis. To further characterize PCs, we compared the expression level of EZH2 protein, the overexpression of which has recently been recognized as poor prognostic factor in CLL/SLL, in the PCs and the intervening small cell areas in lymph nodes of 15 patients with CLL/SLL. We also investigated the mutational profile of EZH2 and the expression of its upstream regulators c-Myc, E2F1, pRB and miR-26a. Our results showed a significantly increased expression of EZH2 in the PCs. No EZH2 mutations were detected, however, overexpression of c-Myc, E2F1 and pRb proteins as well as reduced expression of the tumor suppressor miR-26a were demonstrated in the PCs. In summary our findings indicate that EZH2 pathway is significantly upregulated in the PCs of CLL/SLL lymph nodes, providing further evidence for the distinguished biological features of the PCs.

Pellatt AJ, Mullany LE, Herrick JS, et al.
The TGFβ-signaling pathway and colorectal cancer: associations between dysregulated genes and miRNAs.
J Transl Med. 2018; 16(1):191 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The TGFβ-signaling pathway plays an important role in the pathogenesis of colorectal cancer (CRC). Loss of function of several genes within this pathway, such as bone morphogenetic proteins (BMPs) have been seen as key events in CRC progression.
METHODS: In this study we comprehensively evaluate differential gene expression (RNASeq) of 81 genes in the TGFβ-signaling pathway and evaluate how dysregulated genes are associated with miRNA expression (Agilent Human miRNA Microarray V19.0). We utilize paired carcinoma and normal tissue from 217 CRC cases. We evaluate the associations between differentially expressed genes and miRNAs and sex, age, disease stage, and survival months.
RESULTS: Thirteen genes were significantly downregulated and 14 were significantly upregulated after considering fold change (FC) of > 1.50 or < 0.67 and multiple comparison adjustment. Bone morphogenetic protein genes BMP5, BMP6, and BMP2 and growth differentiation factor GDF7 were downregulated. BMP4, BMP7, INHBA (Inhibin beta A), TGFBR1, TGFB2, TGIF1, TGIF2, and TFDP1 were upregulated. In general, genes with the greatest dysregulation, such as BMP5 (FC 0.17, BMP6 (FC 0.25), BMP2 (FC 0.32), CDKN2B (FC 0.32), MYC (FC 3.70), BMP7 (FC 4.17), and INHBA (FC 9.34) showed dysregulation in the majority of the population (84.3, 77.4, 81.1, 80.2, 82.0, 51.2, and 75.1% respectively). Four genes, TGFBR2, ID4, ID1, and PITX2, were un-associated or slightly upregulated in microsatellite-stable (MSS) tumors while downregulated in microsatellite-unstable (MSI) tumors. Eight dysregulated genes were associated with miRNA differential expression. E2F5 and THBS1 were associated with one or two miRNAs; RBL1, TGFBR1, TGIF2, and INHBA were associated with seven or more miRNAs with multiple seed-region matches. Evaluation of the joint effects of mRNA:miRNA identified interactions that were stronger in more advanced disease stages and varied by survival months.
CONCLUSION: These data support an interaction between miRNAs and genes in the TGFβ-signaling pathway in association with CRC risk. These interactions are associated with unique clinical characteristics that may provide targets for further investigations.

Hasegawa T, Glavich GJ, Pahuski M, et al.
Characterization and Evidence of the miR-888 Cluster as a Novel Cancer Network in Prostate.
Mol Cancer Res. 2018; 16(4):669-681 [PubMed] Free Access to Full Article Related Publications
Prostate cancer afflicts 1 in 7 men and is the second leading cause of male cancer-related deaths in the United States. MicroRNAs (miRNAs), an extensive class of approximately 22 nucleotide noncoding RNAs, are often aberrantly expressed in tissues and fluids from prostate cancer patients, but the mechanisms of how specific miRNAs regulate prostate tumorigenesis and metastasis are poorly understood. Here, miR-888 was identified as a novel prostate factor that promotes proliferation and migration. miR-888 resides within a genomic cluster of 7 miRNA genes (

Hassani S, Khaleghian A, Ahmadian S, et al.
Redistribution of cell cycle by arsenic trioxide is associated with demethylation and expression changes of cell cycle related genes in acute promyelocytic leukemia cell line (NB4).
Ann Hematol. 2018; 97(1):83-93 [PubMed] Related Publications
PML-RARα perturbs the normal epigenetic setting, which is essential to oncogenic transformation in acute promyelocytic leukemia (APL). Transcription induction and recruitment of DNA methyltransferases (DNMTs) by PML-RARα and subsequent hypermethylation are components of this perturbation. Arsenic trioxide (ATO), an important drug in APL therapy, concurrent with degradation of PML-RARα induces cell cycle change and apoptosis. How ATO causes cell cycle alteration has remained largely unexplained. Here, we investigated DNA methylation patterns of cell cycle regulatory genes promoters, the effects of ATO on the methylated genes and cell cycle distribution in an APL cell line, NB4. Analysis of promoter methylation status of 22 cell cycle related genes in NB4 revealed that CCND1, CCNE1, CCNF, CDKN1A, GADD45α, and RBL1 genes were methylated 60.7, 84.6, 58.6, 8.7, 33.4, and 73.7%, respectively, that after treatment with 2 μM ATO for 48 h, turn into 0.6, 13.8, 0.1, 6.6, 10.7, and 54.5% methylated. ATO significantly reduced the expression of DNMT1, 3A, and 3B. ATO induced the expression of CCND1, CCNE1, and GADD45α genes, suppressed the expression of CCNF and CDKN1A genes, which were consistent with decreased number of cells in G1 and S phases and increased number of cells in G2/M phase. In conclusion, demethylation and alteration in the expression level of the cell cycle related genes may be possible mechanisms in ATO-induced cell cycle arrest in APL cells. It may suggest that ATO by demethylation of CCND1 and CCNE1 and their transcriptional activation accelerates G1 and S transition into the G2/M cell cycle arrest.

Dabrowska M, Sirotnak FM
E2F site in the essential promoter region does not confer S phase-specific transcription of the ABCC10 gene in human prostate cancer cells.
Acta Biochim Pol. 2017; 64(2):371-374 [PubMed] Related Publications
ABCC10 (MRP7) plays a role in cellular detoxification and resistance to anticancer drugs. Since ABCC10 gene transcription in human prostate cancer CWR22Rv1 cells was found dependent on E2F binding sequence motif, ABCC10 expression in G

Moghaddaskho F, Eyvani H, Ghadami M, et al.
Demethylation and alterations in the expression level of the cell cycle-related genes as possible mechanisms in arsenic trioxide-induced cell cycle arrest in human breast cancer cells.
Tumour Biol. 2017; 39(2):1010428317692255 [PubMed] Related Publications
Arsenic trioxide (As

Ku SY, Rosario S, Wang Y, et al.
Rb1 and Trp53 cooperate to suppress prostate cancer lineage plasticity, metastasis, and antiandrogen resistance.
Science. 2017; 355(6320):78-83 [PubMed] Free Access to Full Article Related Publications
Prostate cancer relapsing from antiandrogen therapies can exhibit variant histology with altered lineage marker expression, suggesting that lineage plasticity facilitates therapeutic resistance. The mechanisms underlying prostate cancer lineage plasticity are incompletely understood. Studying mouse models, we demonstrate that Rb1 loss facilitates lineage plasticity and metastasis of prostate adenocarcinoma initiated by Pten mutation. Additional loss of Trp53 causes resistance to antiandrogen therapy. Gene expression profiling indicates that mouse tumors resemble human prostate cancer neuroendocrine variants; both mouse and human tumors exhibit increased expression of epigenetic reprogramming factors such as Ezh2 and Sox2. Clinically relevant Ezh2 inhibitors restore androgen receptor expression and sensitivity to antiandrogen therapy. These findings uncover genetic mutations that enable prostate cancer progression; identify mouse models for studying prostate cancer lineage plasticity; and suggest an epigenetic approach for extending clinical responses to antiandrogen therapy.

Lee J, Jung JH, Chae YS, et al.
Long Noncoding RNA snaR Regulates Proliferation, Migration and Invasion of Triple-negative Breast Cancer Cells.
Anticancer Res. 2016; 36(12):6289-6295 [PubMed] Related Publications
AIM: We evaluated the role of long noncoding ribonucleic acid (lncRNA) in breast cancer cell lines by quantitative reverse transcription-polymerase change reaction.
MATERIALS AND METHODS: The effects of small NF90-associated RNA (snaR) with RNA interference on proliferation, migration and invasion of MDA-MB-231 cells were observed by 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide, wound healing and transwell assay.
RESULTS: Among 90 lncRNAs, E2F transcription factor 4, p107/p130-binding (E2F4) antisense, insulin-like growth factor 2 antisense (IGF2AS), snaR, and small nucleolar RNA host gene 5 (SNHG5) were up-regulated in MDA-MB-231 and 7SK, antisense noncoding RNA in the INK4 locus (ANRIL), IGF2AS, Nespas, p53 mRNA, and snaR were up-regulated in MCF-7 cells. Down-regulation of snaR inhibited the proliferation, migration, and invasion of MDA-MD-231 breast cancer cells.
CONCLUSION: LncRNA snaR was found to be up-regulated in breast cancer cells, and the cancer progression of MDA-MB-231 cells was significantly suppressed by down-regulation of snaR. Therefore, snaR knockdown has potential as a treatment modality for triple-negative breast cancer.

Kruer TL, Dougherty SM, Reynolds L, et al.
Expression of the lncRNA Maternally Expressed Gene 3 (MEG3) Contributes to the Control of Lung Cancer Cell Proliferation by the Rb Pathway.
PLoS One. 2016; 11(11):e0166363 [PubMed] Free Access to Full Article Related Publications
Maternally expressed gene 3 (MEG3, mouse homolog Gtl2) encodes a long noncoding RNA (lncRNA) that is expressed in many normal tissues, but is suppressed in various cancer cell lines and tumors, suggesting it plays a functional role as a tumor suppressor. Hypermethylation has been shown to contribute to this loss of expression. We now demonstrate that MEG3 expression is regulated by the retinoblastoma protein (Rb) pathway and correlates with a change in cell proliferation. Microarray analysis of mouse embryonic fibroblasts (MEFs) isolated from mice with genetic deletion of all three Rb family members (TKO) revealed a significant silencing of Gtl2/MEG3 expression compared to WT MEFs, and re-expression of Gtl2/MEG3 caused decrease in cell proliferation and increased apoptosis. MEG3 levels also were suppressed in A549 lung cancer cells compared with normal human bronchial epithelial (NHBE) cells, and, similar to the TKO cells, re-constitution of MEG3 led to a decrease in cell proliferation and elevated apoptosis. Activation of pRb by treatment of A549 and SK-MES-1 cells with palbociclib, a CDK4/6 inhibitor, increased the expression of MEG3 in a dose-dependent manner, while knockdown of pRb/p107 attenuated this effect. In addition, expression of phosphorylation-deficient mutant of pRb increased MEG3 levels in both lung cancer cell types. Treatment of these cells with palbociclib also decreased the expression of pRb-regulated DNA methyltransferase 1 (DNMT1), while conversely, knockdown of DNMT1 resulted in increased expression of MEG3. As gene methylation has been suggested for MEG3 regulation, we found that palbociclib resulted in decreased methylation of the MEG3 locus similar to that observed with 5-aza-deoxycytidine. Anti-sense oligonucleotide silencing of drug-induced MEG3 expression in A549 and SK-MES-1 cells partially rescued the palbociclib-mediated decrease in cell proliferation, while analysis of the TCGA database revealed decreased MEG3 expression in human lung tumors harboring a disrupted RB pathway. Together, these data suggest that disruption of the pRb-DNMT1 pathway leads to a decrease in MEG3 expression, thereby contributing to the pro-proliferative state of certain cancer cells.

Pan D, Chen Y, Du Y, et al.
Methylation of promoter of RBL1 enhances the radioresistance of three dimensional cultured carcinoma cells.
Oncotarget. 2017; 8(3):4422-4435 [PubMed] Free Access to Full Article Related Publications
Three dimensional (3D) culture in vitro is a new cell culture model that more closely mimics the physiology features of the in vivo environment and is being used widely in the field of medical and biological research. It has been demonstrated that cancer cells cultured in 3D matrices are more radioresistant compared with cells in monolayer (2D). However, the mechanisms causing this difference remain largely unclear. Here we found that the cell cycle distribution and expression of cell cycle regulation genes in 3D A549 cells are different from the 2D. The higher levels of the promotor methylation of cell cycle regulation genes such as RBL1 were observed in 3D A549 cells compared with cells in 2D. The treatments of irradiation or 5-Aza-CdR activated the demethylation of RBL1 promotor and resulted in the increased expression of RBL1 only in 3D A549 cells. Inhibition of RBL1 enhanced the radioresistance and decreased the G2/M phase arrest induced by irradiation in 2D A549 and MCF7 cells. Overexpression of RBL1 sensitized 3D cultured A549 and MCF7 cells to irradiation. Taken together, to our knowledge, it is the first time to revealthat the low expression of RBL1 due to itself promotor methylation in 3D cells enhances the radioresistance. Our finding sheds a new light on understanding the features of the 3D cultured cell model and its application in basic research into cancer radiotherapy and medcine development.

Eyvani H, Moghaddaskho F, Kabuli M, et al.
Arsenic trioxide induces cell cycle arrest and alters DNA methylation patterns of cell cycle regulatory genes in colorectal cancer cells.
Life Sci. 2016; 167:67-77 [PubMed] Related Publications
AIMS: Cell cycle dysregulation is important in tumorigenesis. Transcriptional silencing of cell cycle regulatory genes, due to DNA methylation, is a common epigenetic event in malignancies. As
MAIN METHODS: The methylation-specific PCR (MSP) and/or restriction enzyme-based methods were used to study the promoter methylation patterns of 24 cell cycle regulatory genes in CRC cell lines. Gene expression level and cell cycle distribution were determined by Real-time PCR and flow cytometric analyses, respectively.
KEY FINDINGS: Our methylation analysis indicated that only promoters of RBL1 (p107), CHFR and p16 genes were aberrantly methylated in three cell lines. As
SIGNIFICANCE: These data suggest that demethylation and alteration in the expression level of the cell cycle-related genes may be possible mechanisms in As

Kooi IE, van Mil SE, MacPherson D, et al.
Genomic landscape of retinoblastoma in Rb
Genes Chromosomes Cancer. 2017; 56(3):231-242 [PubMed] Related Publications
Several murine retinoblastoma models have been generated by deleting the genes encoding for retinoblastoma susceptibility protein pRb and one of its family members p107 or p130. In Rb

Mushtaq M, Gaza HV, Kashuba EV
Role of the RB-Interacting Proteins in Stem Cell Biology.
Adv Cancer Res. 2016; 131:133-57 [PubMed] Related Publications
Human retinoblastoma gene RB1 is the first tumor suppressor gene (TSG) isolated by positional cloning in 1986. RB is extensively studied for its ability to regulate cell cycle by binding to E2F1 and inhibiting the transcriptional activity of the latter. In human embryonic stem cells (ESCs), only a minute trace of RB is found in complex with E2F1. Increased activity of RB triggers differentiation, cell cycle arrest, and cell death. On the other hand, inactivation of the entire RB family (RB1, RBL1, and RBL2) in human ESC induces G2/M arrest and cell death. These observations indicate that both loss and overactivity of RB could be lethal for the stemness of cells. A question arises why inactive RB is required for the survival and stemness of cells? To shed some light on this question, we analyzed the RB-binding proteins. In this review we have focused on 27 RB-binding partners that may have potential roles in different aspects of stem cell biology.

Alessio N, Capasso S, Di Bernardo G, et al.
Mesenchymal stromal cells having inactivated RB1 survive following low irradiation and accumulate damaged DNA: Hints for side effects following radiotherapy.
Cell Cycle. 2017; 16(3):251-258 [PubMed] Free Access to Full Article Related Publications
Following radiotherapy, bone sarcomas account for a significant percentage of recurring tumors. This risk is further increased in patients with hereditary retinoblastoma that undergo radiotherapy. We analyzed the effect of low and medium dose radiation on mesenchymal stromal cells (MSCs) with inactivated RB1 gene to gain insights on the molecular mechanisms that can induce second malignant neoplasm in cancer survivors. MSC cultures contain subpopulations of mesenchymal stem cells and committed progenitors that can differentiate into mesodermal derivatives: adipocytes, chondrocytes, and osteocytes. These stem cells and committed osteoblast precursors are the cell of origin in osteosarcoma, and RB1 gene mutations have a strong role in its pathogenesis. Following 40 and 2000 mGy X-ray exposure, MSCs with inactivated RB1 do not proliferate and accumulate high levels of unrepaired DNA as detected by persistence of gamma-H2AX foci. In samples with inactivated RB1 the radiation treatment did not increase apoptosis, necrosis or senescence versus untreated cells. Following radiation, CFU analysis showed a discrete number of cells with clonogenic capacity in cultures with silenced RB1. We extended our analysis to the other members of retinoblastoma gene family: RB2/P130 and P107. Also in the MSCs with silenced RB2/P130 and P107 we detected the presence of cells with unrepaired DNA following X-ray irradiation. Cells with unrepaired DNA may represent a reservoir of cells that may undergo neoplastic transformation. Our study suggests that, following radiotherapy, cancer patients with mutations of retinoblastoma genes may be under strict controls to evaluate onset of secondary neoplasms following radiotherapy.

Hesbacher S, Pfitzer L, Wiedorfer K, et al.
RB1 is the crucial target of the Merkel cell polyomavirus Large T antigen in Merkel cell carcinoma cells.
Oncotarget. 2016; 7(22):32956-68 [PubMed] Free Access to Full Article Related Publications
The pocket protein (PP) family consists of the three members RB1, p107 and p130 all possessing tumor suppressive properties. Indeed, the PPs jointly control the G1/S transition mainly by inhibiting E2F transcription factors. Notably, several viral oncoproteins are capable of binding and inhibiting PPs. Merkel cell polyomavirus (MCPyV) is considered as etiological factor for Merkel cell carcinoma (MCC) with expression of the viral Large T antigen (LT) harboring an intact PP binding domain being required for proliferation of most MCC cells. Therefore, we analyzed the interaction of MCPyV-LT with the PPs. Co-IP experiments indicate that MCPyV-LT binds potently only to RB1. Moreover, MCPyV-LT knockdown-induced growth arrest in MCC cells can be rescued by knockdown of RB1, but not by p107 or p130 knockdown. Accordingly, cell cycle arrest and E2F target gene repression mediated by the single PPs can only in the case of RB1 be significantly reverted by MCPyV-LT expression. Moreover, data from an MCC patient indicate that loss of RB1 rendered the MCPyV-positive MCC cells LT independent. Thus, our results suggest that RB1 is the dominant tumor suppressor PP in MCC, and that inactivation of RB1 by MCPyV-LT is largely sufficient for its growth supporting function in established MCPyV-positive MCC cells.

Li T, Zheng Q, An J, et al.
SET1A Cooperates With CUDR to Promote Liver Cancer Growth and Hepatocyte-like Stem Cell Malignant Transformation Epigenetically.
Mol Ther. 2016; 24(2):261-275 [PubMed] Free Access to Full Article Related Publications
Long noncoding RNA CUDR plays an important role during tumorigenesis. Herein, we demonstrate that SET1A cooperates with CUDR to accelerate hepatocarcinogenesis and promote malignant transformation of hepatocyte-like stem cells. Mechanistically, CUDR enhances the phosphorylation of RB1, C-myc expression, and the interplay between the SET1A and pRB1. Notably, CUDR acts as a sponge cushion that shows a link between SET1A and pRB1, producing a activated pRB1-SET1A complex. On the other hand, the pRB1-SET1A complex may carry methyls(me) to occupy the position of H3K4, resulting in specific tri-methylation of forth lysine of histone H3 (H3K4me3). Thereby, the H3K4me3 loads on the TRF2 promoter region which causes the TRF2 overexpression. Ultimately, the excessive TRF2 binds to telomere repeat DNA, prolonging the telomere length. These findings provide the first demonstration that SET1A cooperates with CUDR to play a positive potential role during hepatocarcinogenesis and hepatocyte-like stem cells' malignant transformation epigenetically.

Mileo AM, Mattarocci S, Matarrese P, et al.
Hepatitis C virus core protein modulates pRb2/p130 expression in human hepatocellular carcinoma cell lines through promoter methylation.
J Exp Clin Cancer Res. 2015; 34:140 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Hepatitis C Virus (HCV) infection is associated with chronically evolving disease and development of hepatocellular carcinoma (HCC), albeit the mechanism of HCC induction by HCV is still controversial. The nucleocapsid (core) protein of HCV has been shown to be directly implicated in cellular transformation and immortalization, enhancing the effect of oncogenes and decreasing the one of tumor suppressor genes, as RB1 and its protein product pRB. With the aim of identifying novel molecular mechanisms of hepatocyte transformation by HCV, we examined the effect of HCV core protein on the expression of the whole Retinoblastoma (RB) family of tumor and growth suppressor factors, i.e. pRb, p107 and pRb2/p130.
METHODS: We used a model system consisting of the HuH-7, HCV-free, human hepatocellular carcinoma cell line and of the HuH-7-CORE cells derived from the former and constitutively expressing the HCV core protein. We determined pRb, p107 and pRb2/p130 protein and mRNA amount of the respective genes RB1, RBL1 and RBL2, RBL2 promoter activity and methylation as well as DNA methyltransferase 1 (DNMT1) and 3b (DNMT3b) expression level. The effect of pRb2/p130 over-expression on the HCV core-expressing HuH-7-CORE cells was also evaluated.
RESULTS: We found that the HCV core protein expression down-regulated pRb2/p130 protein and mRNA levels in HuH-7-CORE cells by inducing promoter hyper-methylation with the concomitant up-regulation of DNMT1 and DNMT3b expression. When pRb2/p130 expression was artificially re-established in HuH-7-CORE cells, cell cycle analysis outlined an accumulation in the G0/G1 phase, as expected.
CONCLUSIONS: HCV core appears indeed able to significantly down-regulate the expression and the function of two out of three RB family tumor and growth suppressor factors, i.e. pRb and pRb2/p130. The functional consequences at the level of cell cycle regulation, and possibly of more complex cell homeostatic processes, may represent a plausible molecular mechanism involved in liver transformation by HCV.

Zhu S, Zhao L, Li Y, et al.
Suppression of RAD21 Induces Senescence of MDA-MB-231 Human Breast Cancer Cells Through RB1 Pathway Activation Via c-Myc Downregulation.
J Cell Biochem. 2016; 117(6):1359-69 [PubMed] Related Publications
Cellular senescence impedes cancer progression by limiting uncontrolled cell proliferation. To identify new genetic events controlling senescence, we performed a small interfering RNA screening human cancer cells and identified a number of targets potentially involved in senescence of MDA-MB-231 human breast cancer cells. Importantly, we showed that knockdown of RAD21 resulted in the appearance of several senescent markers, including enhanced senescence-associated β-galactosidase activity and heterochromatin focus formation, as well as elevated p21 protein levels and RB1 pathway activation. Further biochemical analyses revealed that RAD21 knockdown led to the downregulation of c-Myc and its targets, including CDK4, a negative regulator of RB1, and blockedRB1 phosphorylation (pRB1), and the RB1-mediated transcriptional repression of E2F. Moreover, c-Myc downregulation was partially mediated by proteasome-dependent degradation within promyelocytic leukemia (PML) nuclear bodies, which were found to be highly abundant during RAD21 knockdown-induced senescence. Exogenous c-Myc reconstitution rescued cells from RAD21 silencing-induced senescence. Altogether, data arising from this study implicate a novel function of RAD21 in cellular senescence in MDA-MB-231 cells that is mainly dependent onRB1 pathway activation via c-Myc downregulation.

Huang SJ, Gillan TL, Gerrie AS, et al.
Influence of clone and deletion size on outcome in chronic lymphocytic leukemia patients with an isolated deletion 13q in a population-based analysis in British Columbia, Canada.
Genes Chromosomes Cancer. 2016; 55(1):16-24 [PubMed] Related Publications
Deletion of the long arm of chromosome 13 (del(13q)) as the sole abnormality in chronic lymphocytic leukemia (CLL) portends a good prognosis; however, there is great outcome heterogeneity within this subgroup. The percentage of cells with a del(13q) (clone size) and the extent of the deletion are two factors that may affect outcome in CLL patients with isolated del(13q). We analyzed 248 CLL patients from the BC Provincial CLL database identified as having isolated del(13q) detected pretreatment by interphase fluorescence in situ hybridization to determine what impact clone and deletion size had on overall survival (OS) and treatment free survival (TFS). Patients with 60% or more of nuclei with a del(13q) had shorter TFS and shorter OS. A large deletion, encompassing the RB1 gene locus, was detected in half of the 90 cases with available specimens for testing, and there was no significant difference in OS and TFS between RB1-deleted and RB1-not-deleted cases. Further study in a larger sample size is required to determine the clinical interest of RB1 locus testing; however, clone size of del(13q) does predict TFS and OS and may better refine prognosis in this clinically heterogeneous population.

Zhang J, Huang JY, Chen YN, et al.
Whole genome and transcriptome sequencing of matched primary and peritoneal metastatic gastric carcinoma.
Sci Rep. 2015; 5:13750 [PubMed] Free Access to Full Article Related Publications
Gastric cancer is one of the most aggressive cancers and is the second leading cause of cancer death worldwide. Approximately 40% of global gastric cancer cases occur in China, with peritoneal metastasis being the prevalent form of recurrence and metastasis in advanced disease. Currently, there are limited clinical approaches for predicting and treatment of peritoneal metastasis, resulting in a 6-month average survival time. By comprehensive genome analysis will uncover the pathogenesis of peritoneal metastasis. Here we describe a comprehensive whole-genome and transcriptome sequencing analysis of one advanced gastric cancer case, including non-cancerous mucosa, primary cancer and matched peritoneal metastatic cancer. The peripheral blood is used as normal control. We identified 27 mutated genes, of which 19 genes are reported in COSMIC database (ZNF208, CRNN, ATXN3, DCTN1, RP1L1, PRB4, PRB1, MUC4, HS6ST3, MUC17, JAM2, ITGAD, IREB2, IQUB, CORO1B, CCDC121, AKAP2, ACAN and ACADL), and eight genes have not previously been described in gastric cancer (CCDC178, ARMC4, TUBB6, PLIN4, PKLR, PDZD2, DMBT1and DAB1).Additionally,GPX4 and MPND in 19q13.3-13.4 region, is characterized as a novel fusion-gene. This study disclosed novel biological markers and tumorigenic pathways that would predict gastric cancer occurring peritoneal metastasis.

Kumar A, Boyle EA, Tokita M, et al.
Deep sequencing of multiple regions of glial tumors reveals spatial heterogeneity for mutations in clinically relevant genes.
Genome Biol. 2014; 15(12):530 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The extent of intratumoral mutational heterogeneity remains unclear in gliomas, the most common primary brain tumors, especially with respect to point mutation. To address this, we applied single molecule molecular inversion probes targeting 33 cancer genes to assay both point mutations and gene amplifications within spatially distinct regions of 14 glial tumors.
RESULTS: We find evidence of regional mutational heterogeneity in multiple tumors, including mutations in TP53 and RB1 in an anaplastic oligodendroglioma and amplifications in PDGFRA and KIT in two glioblastomas (GBMs). Immunohistochemistry confirms heterogeneity of TP53 mutation and PDGFRA amplification. In all, 3 out of 14 glial tumors surveyed have evidence for heterogeneity for clinically relevant mutations.
CONCLUSIONS: Our results underscore the need to sample multiple regions in GBM and other glial tumors when devising personalized treatments based on genomic information, and furthermore demonstrate the importance of measuring both point mutation and copy number alteration while investigating genetic heterogeneity within cancer samples.

Vilas JM, Ferreirós A, Carneiro C, et al.
Transcriptional regulation of Sox2 by the retinoblastoma family of pocket proteins.
Oncotarget. 2015; 6(5):2992-3002 [PubMed] Free Access to Full Article Related Publications
Cellular reprogramming to iPSCs has uncovered unsuspected links between tumor suppressors and pluripotency factors. Using this system, it was possible to identify tumor suppressor p27 as a repressor of Sox2 during differentiation. This led to the demonstration that defects in the repression of Sox2 can contribute to tumor development. The members of the retinoblastoma family of pocket proteins, pRb, p107 and p130, are negative regulators of the cell cycle with tumor suppressor activity and with roles in differentiation. In this work we studied the relative contribution of the retinoblastoma family members to the regulation of Sox2 expression. We found that deletion of Rb or p130 leads to impaired repression of Sox2, a deffect amplified by inactivation of p53. We also identified binding of pRb and p130 to an enhancer with crucial regulatory activity on Sox2 expression. Using cellular reprogramming we tested the impact of the defective repression of Sox2 and confirmed that Rb deficiency allows the generation of iPSCs in the absence of exogenous Sox2. Finally, partial depletion of Sox2 positive cells reduced the pituitary tumor development initiated by Rb loss in vivo. In summary, our results show that Sox2 repression by pRb is a relevant mechanism of tumor suppression.

Wang Q, Lv H, Lv W, et al.
Genome-wide haplotype association study identifies BLM as a risk gene for prostate cancer in Chinese population.
Tumour Biol. 2015; 36(4):2703-7 [PubMed] Related Publications
Prostate cancer (PC) is a common malignant tumor that occurs in the prostate epithelial cells. It is generally considered to be caused by both genetic and environmental factors. To identify the genetic risk factors of PC in Chinese population, we carried out a genome-wide haplotype-based association study. The 33 Chinese PC cases were from the public GEO database (GSE18333), and the 139 Chinese controls (CHB) were from the HapMap project. Our analysis included three stages: (1) identifying the linkage disequilibrium (LD) blocks and performing genome-wide haplotype association scan, (2) mapping PC-risk haplotypes to PC candidate genes, and (3) prioritizing PC candidate genes based on their similarity to known PC susceptibility genes. The results showed that (1) 749 haplotypes were significantly associated with PC (P < 1E-5). (2) Then, we mapped these significant haplotypes to genes and got 454 PC candidate genes. (3) After prioritizing the candidate genes based on their similarity to known PC susceptibility genes, we found that seven novel PC susceptibility genes including BLM, RPS6KA2, FRK, ERBB4, RBL1, PAK7, and ERBB2IP. Among the seven genes, BLM gene ranked first (P = 1.89E-04). A haplotype GGTTACCCCTC (rs2270131, rs2073919, rs11073953, rs12592875, rs16944863, rs2238337, rs414634, rs401549, rs17183344, rs16944884, and rs16944888) on chromosome 15q26.1 had significant association with PC (P = 2.37E-11). To our knowledge, this is the first genetic association study to show the significant association between BLM gene and PC susceptibility in Chinese population.

Benavente CA, Finkelstein D, Johnson DA, et al.
Chromatin remodelers HELLS and UHRF1 mediate the epigenetic deregulation of genes that drive retinoblastoma tumor progression.
Oncotarget. 2014; 5(20):9594-608 [PubMed] Free Access to Full Article Related Publications
The retinoblastoma (Rb) family of proteins are key regulators of cell cycle exit during development and their deregulation is associated with cancer. Rb is critical for normal retinal development and germline mutations lead to retinoblastoma making retinae an attractive system to study Rb family signaling. Rb coordinates proliferation and differentiation through the E2f family of transcription factors, a critical interaction for the role of Rb in retinal development and tumorigenesis. However, whether the roles of the different E2fs are interchangeable in controlling development and tumorigenesis in the retina or if they have selective functions remains unknown. In this study, we found that E2f family members play distinct roles in the development and tumorigenesis. In Rb;p107-deficient retinae, E2f1 and E2f3 inactivation rescued tumor formation but only E2f1 rescued the retinal development phenotype. This allowed the identification of key target genes for Rb/E2f family signaling contributing to tumorigenesis and those contributing to developmental defects. We found that Sox4 and Sox11 genes contribute to the developmental phenotype and Hells and Uhrf1 contribute to tumorigenesis. Using orthotopic human xenografts, we validated that upregulation of HELLS and UHRF1 is essential for the tumor phenotype. Also, these epigenetic regulators are important for the regulation of SYK.

Lam SK, Li YY, Zheng CY, Ho JC
Downregulation of thymidylate synthase and E2F1 by arsenic trioxide in mesothelioma.
Int J Oncol. 2015; 46(1):113-22 [PubMed] Related Publications
Malignant pleural mesothelioma is a global health issue. Arsenic trioxide (ATO) has been shown to suppress thymidylate synthase (TYMS) in lung adenocarcinoma and colorectal cancer, and induce apoptosis in acute promyelocytic leukemia. With TYMS as a putative therapeutic target, the effect of ATO in mesothelioma was therefore studied. A panel of 5 mesothelioma cell lines was used to study the effect of ATO on cell viability, protein expression, mRNA expression and TYMS activity by MTT assay, western blot, qPCR and tritium-release assay, respectively. The knockdown of TYMS and E2F1 was performed with a specific siRNA. Phosphatidylserine externalization and mitochondrial membrane depolarization were measured by Annexin V and JC-1 staining respectively. The in vivo effect of ATO was studied using a nude mouse xenograft model. Application of ATO demonstrated anticancer effects in the cell line model with clinically achievable concentrations. Downregulation of TYMS protein (except H226 cells and 1.25 µM ATO in H2052 cells) and mRNA expression (H28 cells), pRB1 (H28 cells) and E2F1 and TYMS activity (except H226 cells) were also evident. E2F1 knockdown decreased cell viability more significantly than TYMS knockdown. In general, thymidine kinase 1, ribonucleotide reductase M1, c-myc and skp2 were downregulated by ATO. p-c-Jun was downregulated in H28 cells while upregulated in 211H cells. Phosphatidylserine externalization, mitochondrial membrane depolarization, downregulation of Bcl-2 and Bcl-xL, and upregulation of Bak and cleaved caspase-3 were observed. In the H226 xenograft model, the relative tumor growth was aborted, and E2F1 was downregulated while cleaved caspase-3 was elevated and localized to the nucleus in the ATO treatment group. ATO has potent antiproliferative and cytotoxic effects in mesothelioma in vitro and in vivo, partially mediated through E2F1 targeting (less effect through TYMS targeting). There is sound scientific evidence to support the clinical application of ATO in treatment of mesothelioma.

Xu XL, Singh HP, Wang L, et al.
Rb suppresses human cone-precursor-derived retinoblastoma tumours.
Nature. 2014; 514(7522):385-8 [PubMed] Free Access to Full Article Related Publications
Retinoblastoma is a childhood retinal tumour that initiates in response to biallelic RB1 inactivation and loss of functional retinoblastoma (Rb) protein. Although Rb has diverse tumour-suppressor functions and is inactivated in many cancers, germline RB1 mutations predispose to retinoblastoma far more strongly than to other malignancies. This tropism suggests that retinal cell-type-specific circuitry sensitizes to Rb loss, yet the nature of the circuitry and the cell type in which it operates have been unclear. Here we show that post-mitotic human cone precursors are uniquely sensitive to Rb depletion. Rb knockdown induced cone precursor proliferation in prospectively isolated populations and in intact retina. Proliferation followed the induction of E2F-regulated genes, and depended on factors having strong expression in maturing cone precursors and crucial roles in retinoblastoma cell proliferation, including MYCN and MDM2. Proliferation of Rb-depleted cones and retinoblastoma cells also depended on the Rb-related protein p107, SKP2, and a p27 downregulation associated with cone precursor maturation. Moreover, Rb-depleted cone precursors formed tumours in orthotopic xenografts with histological features and protein expression typical of human retinoblastoma. These findings provide a compelling molecular rationale for a cone precursor origin of retinoblastoma. More generally, they demonstrate that cell-type-specific circuitry can collaborate with an initiating oncogenic mutation to enable tumorigenesis.

Butcher LD, Garcia M, Arnold M, et al.
Immune response to JC virus T antigen in patients with and without colorectal neoplasia.
Gut Microbes. 2014; 5(4):468-75 [PubMed] Free Access to Full Article Related Publications
JC virus (JCV) is a polyomavirus that infects approximately 75% of the population and encodes a T antigen (T-Ag) gene, which is oncogenic and inactivates the p53 and pRb/p107/p130 protein families. Previous work in our lab has identified the presence of T-Ag in colorectal neoplasms. While JCV remains in a latent state for the majority of those infected, we hypothesized that a disturbance in immunological control may permit JCV to reactivate, which may be involved in the development of colorectal neoplasia. Our aim was to determine the cell mediated immune response to JCV T-Ag, and determine if it is altered in patients with colorectal adenomatous polyps (AP) or cancers (CRC). Peripheral blood mononuclear cells (PBMCs) isolated from the blood of patients undergoing colonoscopy or colorectal surgery were stimulated by a peptide library covering the entire T-Ag protein of JCV. Cytokine production and T cell proliferation were evaluated following T-Ag stimulation using Luminex and flow cytometry assays. JCV T-Ag peptides stimulated secretion of IL-2, which induced T cell expansion in all three groups. However, stronger IL-10 and IL-13 production was seen in patients without colorectal neoplasms. IP-10 was produced at very high levels in all groups, but not significantly differently between groups. Most patients exhibited CD4(+) and CD8(+) T cells in response to stimulation by the T-Ag clusters. The combination of IL-2 and IP-10 secretion indicates the presence of T-Ag-specific Th1 cells in all patients, which is higher in patients without carcinoma.

van der Linden MH, Willekes M, van Roon E, et al.
MLL fusion-driven activation of CDK6 potentiates proliferation in MLL-rearranged infant ALL.
Cell Cycle. 2014; 13(5):834-44 [PubMed] Free Access to Full Article Related Publications
Acute lymphoblastic leukemia in infants (< 1 year-of-age) is characterized by a high incidence of MLL rearrangements. Recently, direct targets of the MLL fusion protein have been identified. However, functional validation of the identified targets remained unacknowledged. In this study, we identify CDK6 as a direct target of the MLL fusion protein and an important player in the proliferation advantage of MLL-rearranged leukemia. CDK6 mRNA was significantly higher expressed in MLL-rearranged infant ALL patients compared with MLL wild-type ALL patients (P < 0.001). Decrease of MLL-AF4 and MLL-ENL fusion mRNA expression by siRNAs resulted in downregulation of CDK6, affirming a direct relationship between the presence of the MLL fusion and CDK6 expression. Knockdown of CDK6 itself significantly inhibited proliferation in the MLL-AF4-positive cell line SEM, whereas knockdown of the highly homologous gene CDK4 had virtually no effect on the cell cycle. Furthermore, we show in vitro sensitivity of MLL-rearranged leukemia cell lines to the CDK4/6-inhibitor PD0332991, inducing a remarkable G 1 arrest, and downregulation of its downstream targets pRB1 and EZH2. We therefore conclude that CDK6 is indeed a direct target of MLL fusion proteins, playing an important role in the proliferation advantage of MLL-rearranged ALL cells.

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