Research IndicatorsGraph generated 01 September 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 01 September, 2019 using data from PubMed, MeSH and CancerIndex
Specific Cancers (3)
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: RBM5 (cancer-related)
A key step in pre-mRNA splicing is the recognition of 3' splicing sites by the U2AF large and small subunits, a process regulated by numerous trans-acting splicing factors. How these trans-acting factors interact with U2AF in vivo is unclear. From a screen for suppressors of the temperature-sensitive (ts) lethality of the C. elegans U2AF large subunit gene uaf-1(n4588) mutants, we identified mutations in the RNA binding motif gene rbm-5, a homolog of the tumor suppressor gene RBM5. rbm-5 mutations can suppress uaf-1(n4588) ts-lethality by loss of function and neuronal expression of rbm-5 was sufficient to rescue the suppression. Transcriptome analyses indicate that uaf-1(n4588) affected the expression of numerous genes and rbm-5 mutations can partially reverse the abnormal gene expression to levels similar to that of wild type. Though rbm-5 mutations did not obviously affect alternative splicing per se, they can suppress or enhance, in a gene-specific manner, the altered splicing of genes in uaf-1(n4588) mutants. Specifically, the recognition of a weak 3' splice site was more susceptible to the effect of rbm-5. Our findings provide novel in vivo evidence that RBM-5 can modulate UAF-1-dependent RNA splicing and suggest that RBM5 might interact with U2AF large subunit to affect tumor formation.
Prabhu VV, Devaraj NRegulating RNA Binding Motif 5 Gene Expression- A Novel Therapeutic Target for Lung Cancer.
J Environ Pathol Toxicol Oncol. 2017; 36(2):99-105 [PubMed
] Related Publications
RNA-binding motif protein 5 (RBM5), also known as LUCA-15/H37, is a gene that maps to human chromosome 3p21.3, a critical region that is deleted in a large number of human cancers, of which the majority are lung cancers, and that is predicted to contain one or more tumor suppressor genes (TSGs). RBM5 is a tumor suppressor gene and is most frequently deleted at the earliest stage of lung cancer development. It represents a significant area of recent progress in cancer genomic, cytogenetic, and molecular biological research because of its role in the induction of cell cycle arrest and apoptosis and the regulation of inhibition of in lung cancer metastasis. RBM5 is involved in the suppression of epidermal growth factor receptor (EGFR) expression, thus preventing proliferation, angiogenesis, invasion, and metastasis of lung cancer. In this way it exhibits its tumor suppressive capacity during lung cancer progression. Exploration of RBM5's potential importance in inhibiting tumor metastasis includes downstream players in the RBM5-mediated metastasis suppressor pathway(s). This review highlights the differential expression of the RBM5 tumor suppressor gene which impacts cell proliferation and apoptosis control during lung cancer progression. Regulating RBM5 expression may be a novel therapeutic target for lung cancer.
Cigarette smoking is undoubtedly a risk factor for lung cancer. Moreover, smokers with genetic mutations on chromosome 3p21.3, a region frequently deleted in cancer and notably in lung cancer, have a dramatically higher risk of aggressive lung cancer. The RNA binding motif 5 (RBM5) is one of the component genes in the 3p21.3 tumour suppressor region. Studies using human cancer specimens and cell lines suggest a role for RBM5 as a tumour suppressor. Here we demonstrate, for the first time, an in vivo role for RBM5 as a tumour suppressor in the mouse lung. We generated Rbm5 loss-of-function mice and exposed them to a tobacco carcinogen NNK. Upon exposure to NNK, Rbm5 loss-of-function mice developed lung cancer at similar rates to wild type mice. As tumourigenesis progressed, however, reduced Rbm5 expression lead to significantly more aggressive lung cancer i.e. increased adenocarcinoma nodule numbers and tumour size. Our data provide in vivo evidence that reduced RBM5 function, as occurs in a large number of patients, coupled with exposure to tobacco carcinogens is a risk factor for an aggressive lung cancer phenotype. These data suggest that RBM5 loss-of-function likely underpins at least part of the pro-tumourigenic consequences of 3p21.3 deletion in humans.
OBJECTIVE: miR-483-5p has been identified as a miRNA oncogene in certain cancers. However, its role in prostate cancer has not been sufficiently investigated. In this study, we investigated the role of miR-483-5p in prostate cancer and examined RBM5 regulation by miR-483-5p.
MATERIAL AND METHODS: Expression levels of miR-483-5p were determined by quantitative real-time PCR. The effect of miR-483-5p on proliferation was evaluated by MTT assay, cell invasion was evaluated by trans-well invasion assays, and target protein expression was determined by western blotting in LNCaP, DU-145, and PC-3 cells. Luciferase reporter plasmids were constructed to confirm the action of miR-483-5p on downstream target gene RBM5 in HEK-293T cells.
RESULTS: we observed that miR-483-5p was upregulated in prostate cancer cell lines and tissues. A miR-483-5p inhibitor inhibited prostate cancer cell growth and invasion in DU-145 and PC-3 cells. miR-483-5p directly bound to the 3' untranslated region (3'UTR) of RBM5 in HEK-293T cells. RBM5 overexpression inhibited prostate cancer cell growth and invasion in LNCaP cells. Enforced RBM5 expression alleviated miR- 483-5p promotion of prostate cancer cell growth and invasion in LNCaP cells.
CONCLUSION: The present study describes a potential mechanism underlying a miR-483- 5p/RBM5 link that contributes to prostate cancer development.
Kobayashi T, Ishida J, Shimizu Y, et al.Decreased RNA-binding motif 5 expression is associated with tumor progression in gastric cancer.
Tumour Biol. 2017; 39(3):1010428317694547 [PubMed
] Related Publications
RNA-binding motif 5 is a putative tumor suppressor gene that modulates cell cycle arrest and apoptosis. We recently demonstrated that RNA-binding motif 5 inhibits cell growth through the p53 pathway. This study evaluated the clinical significance of RNA-binding motif 5 expression in gastric cancer and the effects of altered RNA-binding motif 5 expression on cancer biology in gastric cancer cells. RNA-binding motif 5 protein expression was evaluated by immunohistochemistry using the surgical specimens of 106 patients with gastric cancer. We analyzed the relationships of RNA-binding motif 5 expression with clinicopathological parameters and patient prognosis. We further explored the effects of RNA-binding motif 5 downregulation with short hairpin RNA on cell growth and p53 signaling in MKN45 gastric cancer cells. Immunohistochemistry revealed that RNA-binding motif 5 expression was decreased in 29 of 106 (27.4%) gastric cancer specimens. Decreased RNA-binding motif 5 expression was correlated with histological differentiation, depth of tumor infiltration, nodal metastasis, tumor-node-metastasis stage, and prognosis. RNA-binding motif 5 silencing enhanced gastric cancer cell proliferation and decreased p53 transcriptional activity in reporter gene assays. Conversely, restoration of RNA-binding motif 5 expression suppressed cell growth and recovered p53 transactivation in RNA-binding motif 5-silenced cells. Furthermore, RNA-binding motif 5 silencing reduced the messenger RNA and protein expression of the p53 target gene p21. Our results suggest that RNA-binding motif 5 downregulation is involved in gastric cancer progression and that RNA-binding motif 5 behaves as a tumor suppressor gene in gastric cancer.
BACKGROUND: Gliomas are one of the most common malignant brain tumors and bring a big threat to human life as traditional therapy is unsatisfactory. RBM5 was a RNA-binding motif protein and was reported as a tumor suppressor. But the role of RBM5 in gliomas was unknown.
METHODS: The mRNA level of RBM5 was determined in gliomas tissues and cell lines by real-time quantitative PCR (qRT-PCR) assay while the association of RBM5 expression with prognosis was analyzed by Kaplan-Meier method and compared by log-rank test. Lentivirus was used to overexpress RBM5 in gliomas cells. MTT and BrdU incorporation assay were used to determine cell proliferation and DNA synthesis when the ability of cell migration and invasion was analyzed by transwell assay with/without Matrigel. Cell apoptosis rate was determined with fluorescence-activated cell sorting (FACS) method. Then, expression of apoptosis molecules and critical members in Wnt/β-catenin pathway were detected by western blot analysis.
RESULTS: RBM5 was shown to be downregulated in gliomas tissues and gliomas cell lines. And decreased RBM5 expression was clinically correlated with tumor stage, patient age, and poor prognosis of gliomas patients. The proliferation and DNA synthesis was dramatically inhibited when RBM5 was overexpressed in SHG44 or U251 cells. Also, the ability of cell migration and invasion was disrupted. Then, the level of β-catenin and Cyclin D1 significantly decreased when DKK1 and P-GSK-3β increased reversely in SHG44 cells, which suggested that RBM5 inhibited canonical Wnt/β-catenin signaling. Meanwhile, we demonstrated that caspase3-mediated apoptotic pathway was activated by RBM5 as Bax, TNF-α, and cleaved caspase3 were greatly upregulated while antiapoptotic molecule Bcl-2 was downregulated. Additionally, that apoptotic rate increased significantly from less than 1 to 32% in RBM5-overexpressed SHG44 cells further supported the pro-apoptosis role of RBM5 in gliomas cells.
CONCLUSIONS: RBM5 plays a suppressor role in human gliomas by inhibiting Wnt/β-catenin signaling and inducing cell apoptosis. This study improves our knowledge about the carcinogenesis and progression of human gliomas, which would greatly contribute to the therapy for gliomas patients.
Cancer-initiating cells (CIC) undergo asymmetric growth patterns that increase phenotypic diversity and drive selection for chemotherapeutic resistance and tumor relapse. WNT signaling is a hallmark of colon CIC, often caused by APC mutations, which enable activation of β-catenin and MYC Accumulating evidence indicates that long noncoding RNAs (lncRNA) contribute to the stem-like character of colon cancer cells. In this study, we report enrichment of the lncRNA RBM5-AS1/LUST during sphere formation of colon CIC. Its silencing impaired WNT signaling, whereas its overexpression enforced WNT signaling, cell growth, and survival in serum-free media. RBM5-AS1 has been little characterized previously, and we determined it to be a nuclear-retained transcript that selectively interacted with β-catenin. Mechanistic investigations showed that silencing or overexpression of RBM5-AS1 caused a respective loss or retention of β-catenin from TCF4 complexes bound to the WNT target genes SGK1, YAP1, and MYC Our work suggests that RBM5-AS1 activity is critical for the functional enablement of colon cancer stem-like cells. Furthermore, it defines the mechanism of action of RBM5-AS1 in the WNT pathway via physical interactions with β-catenin, helping organize transcriptional complexes that sustain colon CIC function. Cancer Res; 76(19); 5615-27. ©2016 AACR.
Zhang XL, Liu N, Weng SF, Wang HSBisphenol A Increases the Migration and Invasion of Triple-Negative Breast Cancer Cells via Oestrogen-related Receptor Gamma.
Basic Clin Pharmacol Toxicol. 2016; 119(4):389-95 [PubMed
] Related Publications
Triple-negative breast cancer (TNBC) is characterized by great metastasis and invasion capability. Our study revealed that nanomolar bisphenol A (BPA), one of the most ubiquitous endocrine disruptors, can increase wound closure and invasion of both MDA-MB-231 and BT-549 cells. BPA treatment can increase protein and mRNA expression of matrix metalloproteinase-2 (MMP-2) and MMP-9, while had no effect on the expression of vimentin (Vim) and fibronectin (FN) in TNBC cells. The expression of G-protein-coupled receptor (GPER), which has been suggested to mediate rapid oestrogenic signals, was not varied in BPA-treated MDA-MB-231 and BT-549 cells. Its inhibitor G15 also had no effect on BPA-induced MMPs expression and cell invasion. Interestingly, BPA treatment can significantly increase the mRNA and protein expressions of oestrogen-related receptor γ (ERRγ), but not ERRα or ERRβ, in both MDA-MB-231 and BT-549 cells. The knock-down of ERRγ can markedly attenuate BPA-induced expression of MMP-2 and MMP-9 in TNBC cells. BPA treatment can activate both ERK1/2 and Akt in TNBC cells. Both inhibitors of ERK1/2 (PD98059) and Akt (LY294002) can attenuate BPA-induced ERRγ expression and cell invasion of MDA-MB-231 cells. Collectively, our data revealed that BPA can increase the expression of MMPs and in vitro motility of TNBC cells via ERRγ. Both activation of ERK1/2 and Akt participated in this process. Our study suggests that more attention should be paid to the roles of xenoestrogens such as BPA in the development and progression of TNBC.
Yang C, Sun C, Liang X, et al.Integrative analysis of microRNA and mRNA expression profiles in non-small-cell lung cancer.
Cancer Gene Ther. 2016; 23(4):90-7 [PubMed
] Related Publications
Non-small-cell lung cancer (NSCLC) represents the most common deadly disease. Emerging evidences suggest that abnormal epigenetic modulation via mRNAs and microRNAs (miRNAs) might be involved in the tumorigenesis. To explore novel therapeutic target of NSCLC, a more detailed mRNAs and miRNA expression profiling study is needed. High-quality total RNA including miRNA was isolated from NSCLC tissue and para-carcinoma tissue and used for RNA and small RNA sequencing. Results were analyzed bioinformatically and validated using quantitative real-time (qRT)-PCR. A total of 3530 genes (1977 up-regulated and 1553 down-regulated) and 211 miRNAs (171 up-regulated and 30 down-regulated) were differentially expressed (DE) in NSCLC tissue versus adjacent normal tissues. Furthermore, 157 novel miRNAs were predicted in our samples. Of these, 918 significant miRNA-mRNA pairs were identified, consisting of 100 miRNAs and 443 mRNAs. Gene ontology analysis revealed that most of the target genes were enriched in the terms of plasma membrane, binding, and multiple biological-molecular signaling processes. Pathway analysis of these miRNA signatures highlights their critical roles in calcium signaling pathway. Using qRT-PCR, the expression of several DE genes (KRAS and RBM5) and miRNAs (miR-1-5p, let-7b-5p, miR-21-5p, miR-1290, miR-149-5p, chr8_28846, chrX_31594, and chr9_29897) were confirmed. The integrative analysis based on mRNA and miRNA profiling may provide more potential molecular for the tumorigenesis and development of NSCLC.
BACKGROUND: Dysfunctions in autophagy and apoptosis are closely interacted and play an important role in cancer development. RNA binding motif 5 (RBM5) is a tumor suppressor gene, which inhibits tumor cells' growth and enhances chemosensitivity through inducing apoptosis in our previous studies. In this study, we investigated the relationship between RBM5 overexpression and autophagy in human lung adenocarcinoma cells.
METHODS: Human lung adenocarcinoma cancer (A549) cells were cultured in vitro and were transiently transfected with a RBM5 expressing plasmid (GV287-RBM5) or plasmid with scrambled control sequence. RBM5 expression was determined by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) and Western blot. Intracellular LC-3 I/II, Beclin-1, lysosome associated membrane protein-1 (LAMP1), Bcl-2, and NF-κB/p65 protein levels were detected by Western blot. Chemical staining with monodansylcadaverine (MDC) and acridine orange (AO) was applied to detect acidic vesicular organelles (AVOs). The ultrastructure changes were observed under transmission electron microscope (TEM). Then, transplanted tumor models of A549 cells on BALB/c nude mice were established and treated with the recombinant plasmids carried by attenuated Salmonella to induce RBM5 overexpression in tumor tissues. RBM5, LC-3, LAMP1, and Beclin1 expression was determined by immunohistochemistry staining in plasmids-treated A549 xenografts.
RESULTS: Our study demonstrated that overexpression of RBM5 caused an increase in the autophagy-related proteins including LC3-I, LC3-II, LC3-II/LC3-I ratio, Beclin1, and LAMP1 in A549 cells. A large number of autophagosomes with double-membrane structure and AVOs were detected in the cytoplasm of A549 cells transfected with GV287-RBM5 at 24 h. We observed that the protein level of NF-κB/P65 was increased and the protein level of Bcl-2 decreased by RBM5 overexpression. Furthermore, treatment with an autophagy inhibitor, 3-MA, enhanced RBM5-induced cell death and chemosensitivity in A549 cells. Furthermore, we successfully established the lung adenocarcinoma animal model using A549 cells. Overexpression of RBM5 enhanced the LC-3, LAMP1, and Beclin1 expression in the A549 xenografts.
CONCLUSIONS: Our findings showed for the first time that RBM5 overexpression induced autophagy in human lung adenocarcinoma cells, which might be driven by upregulation of Beclin1, NF-κB/P65, and downregulation of Bcl-2. RBM5-enhanced autophagy acts in a cytoprotective way and inhibition of autophagy may improve the anti-tumor efficacy of RBM5 in lung cancer.
Lv XJ, Du YW, Hao YQ, et al.RNA-binding motif protein 5 inhibits the proliferation of cigarette smoke-transformed BEAS-2B cells through cell cycle arrest and apoptosis.
Oncol Rep. 2016; 35(4):2315-27 [PubMed
] Related Publications
Cigarette smoking has been shown to be the most significant risk factor for lung cancer. Recent studies have also indicated that RNA-binding motif protein 5 (RBM5) can modulate apoptosis and suppress tumor growth. The present study focused on the role of RBM5 in the regulation of cigarette smoke extract (CSE)-induced transformation of bronchial epithelial cells into the cancerous phenotype and its mechanism of action. Herein, we exposed normal BEAS-2B cells for 8 days to varying concentrations of CSE or dimethylsulfoxide (DMSO), followed by a recovery period of 2 weeks. Next, the RBM5 protein was overexpressed in these transformed BEAS-2B cells though lentiviral infection. Later, the morphological changes, cell proliferation, cell cycle, apoptosis, invasion and migration were assessed. In addition, we analyzed the role of RBM5 in xenograft growth. The expression of RBM5 along with the genes related to cell cycle regulation, apoptosis and invasion were also examined. Finally, our results revealed that BEAS-2B cells exposed to 100 µg/ml CSE acquired phenotypic changes and formed tumors in nude mice, indicative of their cancerous transformation and had reduced RBM5 expression. Subsequent overexpression of RBM5 in these cells significantly inhibited their proliferation, induced G1/S arrest, triggered apoptosis and inhibited their invasion and migration, including xenograft growth. Thus, we established an in vitro model of CSE-induced cancerous transformation and concluded that RBM5 overexpression inhibited the growth of these transformed cells through cell cycle arrest and induction of apoptosis. Therefore, our study suggests the importance of RBM5 in the pathogenesis of smoking-related cancer.
Cancer-associated somatic mutations outside protein-coding regions remain largely unexplored. Analyses of the TERT locus have indicated that non-coding regulatory mutations can be more frequent than previously suspected and play important roles in oncogenesis. Using a computational method called SASE-hunter, developed here, we identified a novel signature of accelerated somatic evolution (SASE) marked by a significant excess of somatic mutations localized in a genomic locus, and prioritized those loci that carried the signature in multiple cancer patients. Interestingly, even when an affected locus carried the signature in multiple individuals, the mutations contributing to SASE themselves were rarely recurrent at the base-pair resolution. In a pan-cancer analysis of 906 samples from 12 tumor types, we detected SASE in the promoters of several genes, including known cancer genes such as MYC, BCL2, RBM5 and WWOX. Nucleotide substitution patterns consistent with oxidative DNA damage and local somatic hypermutation appeared to contribute to this signature in selected gene promoters (e.g. MYC). SASEs in selected cancer gene promoters were associated with over-expression, and also correlated with the age of onset of cancer, aggressiveness of the disease and survival. Taken together, our work detects a hitherto under-appreciated and clinically important class of regulatory changes in cancer genomes.
BACKGROUND: RNA binding motif 5 (RBM5) is a tumor suppressor gene that modulates apoptosis through the regulation of alternative splicing of apoptosis-related genes. Our previous studies suggested that RBM5 expression was negatively correlated with the expression of epidermal growth factor receptor (EGFR) in non-small cell lung cancer (NSCLC) tissues. This study was aimed at determining whether RBM5 is able to regulate EGFR expression.
METHODS: Both in vitro and in vivo studies were carried out to determine the effect of RBM5 on the expression of EGFR. Lentiviral vector-mediated RBM5 overexpression was employed in lung adenocarcinoma cell line A549. A549 xenograft mice were treated with recombinant RBM5 plasmid carried by attenuated Salmonella typhi Ty21a. Real-time quantitative polymerase chain reaction and Western blot were carried out to detect RBM5 and EGFR expression.
RESULTS: Both in vivo and in vitro studies indicated that the expression of EGFR mRNA and protein was decreased significantly in the RBM5 overexpression group compared to control groups as shown by real-time PCR and Western blot analysis. We identified that RBM5 overexpression inhibited EGFR expression both in A549 cells and in A549 xenograft mice model.
CONCLUSIONS: Our study demonstrated that EGFR expression is regulated by RBM5 in lung adenocarcinomas cells either in a direct or indirect way, which might be meaningful with regards to target therapy in lung cancer.
Tao S, He H, Chen Q, Yue WGPER mediated estradiol reduces miR-148a to promote HLA-G expression in breast cancer.
Biochem Biophys Res Commun. 2014; 451(1):74-8 [PubMed
] Related Publications
Breast cancer is the most common malignant diseases in women. miR-148a plays an important role in regulation of cancer cell proliferation and cancer invasion and down-regulation of miR-148a has been reported in both estrogen receptor (ER) positive and triple-negative (TN) breast cancer. However, the regulation mechanism of miR-148a is unclear. The role of estrogen signaling, a signaling pathway is important in development and progression of breast cancer. Therefore, we speculated that E2 may regulate miR-148a through G-protein-coupled estrogen receptor-1 (GPER). To test our hypothesis, we checked the effects of E2 on miR-148a expression in ER positive breast cancer cell MCF-7 and TN cancer cell MDA-MB-231. Then we used GPER inhibitor G15 to investigate whether GPER is involved in regulation of E2 on miR-148a. Furthermore, we analyzed whether E2 affects the expression of HLA-G, which is a miR-148a target gene through GPER. The results showed that E2 induces the level of miR-148a in MCF-7 and MDA-MB-231 cells, GPER mediates the E2-induced increase in miR-148a expression in MCF-7 and MDA-MB-231 cells and E2-GPER regulates the expression of HLA-G by miR-148a. In conclusion, our findings offer important new insights into the ability of estrogenic GPER signaling to trigger HLA-G expression through inhibiting miR-148a that supports immune evasion in breast cancer.
Impaired Fas-mediated apoptosis is associated with poor clinical outcomes and cancer chemoresistance. Soluble Fas receptor (sFas), produced by skipping of exon 6, inhibits apoptosis by sequestering Fas ligand. Serum sFas is associated with poor prognosis of non-Hodgkin's lymphomas. We found that the alternative splicing of Fas in lymphomas is tightly regulated by a long-noncoding RNA corresponding to an antisense transcript of Fas (FAS-AS1). Levels of FAS-AS1 correlate inversely with production of sFas, and FAS-AS1 binding to the RBM5 inhibits RBM5-mediated exon 6 skipping. EZH2, often mutated or overexpressed in lymphomas, hyper-methylates the FAS-AS1 promoter and represses the FAS-AS1 expression. EZH2-mediated repression of FAS-AS1 promoter can be released by DZNeP (3-Deazaneplanocin A) or overcome by ectopic expression of FAS-AS1, both of which increase levels of FAS-AS1 and correspondingly decrease expression of sFas. Treatment with Bruton's tyrosine kinase inhibitor or EZH2 knockdown decreases the levels of EZH2, RBM5 and sFas, thereby enhancing Fas-mediated apoptosis. This is the first report showing functional regulation of Fas repression by its antisense RNA. Our results reveal new therapeutic targets in lymphomas and provide a rationale for the use of EZH2 inhibitors or ibrutinib in combination with chemotherapeutic agents that recruit Fas for effective cell killing.
Zhang L, Zhang Q, Yang Y, Wu CThe RNA recognition motif domains of RBM5 are required for RNA binding and cancer cell proliferation inhibition.
Biochem Biophys Res Commun. 2014; 444(3):445-50 [PubMed
] Related Publications
RBM5 is a known putative tumor suppressor gene that has been shown to function in cell growth inhibition by modulating apoptosis. RBM5 also plays a critical role in alternative splicing as an RNA binding protein. However, it is still unclear which domains of RBM5 are required for RNA binding and related functional activities. We hypothesized the two putative RNA recognition motif (RRM) domains of RBM5 spanning from amino acids 98-178 and 231-315 are essential for RBM5-mediated cell growth inhibition, apoptosis regulation, and RNA binding. To investigate this hypothesis, we evaluated the activities of the wide-type and mutant RBM5 gene transfer in low-RBM5 expressing A549 cells. We found that, unlike wild-type RBM5 (RBM5-wt), a RBM5 mutant lacking the two RRM domains (RBM5-ΔRRM), is unable to bind RNA, has compromised caspase-2 alternative splicing activity, lacks cell proliferation inhibition and apoptosis induction function in A549 cells. These data provide direct evidence that the two RRM domains of RBM5 are required for RNA binding and the RNA binding activity of RBM5 contributes to its function on apoptosis induction and cell growth inhibition.
Cancer-associated fibroblasts (CAFs) are crucial co-mediators of breast cancer progression. Estrogen is the predominant driving force in the cyclic regulation of the mammary extracellular matrix, thus potentially affecting the tumor-associated stroma. Recently, a third estrogen receptor, estrogen (G-protein-coupled) receptor (GPER), has been reported to be expressed in breast CAFs. In this study, GPER was detected by immunohistochemical analysis in stromal fibroblasts of 41.8% (59/141) of the primary breast cancer samples. GPER expression in CAFs isolated from primary breast cancer tissues was confirmed by immunostaining and RT-PCR analyses. Tamoxifen (TAM) in addition to 17β-estradiol (E₂) and the GPER agonist G1 activated GPER, resulting in transient increases in cell index, intracellular calcium, and ERK1/2 phosphorylation. Furthermore, TAM, E₂, and G1 promoted CAF proliferation and cell-cycle progression, both of which were blocked by GPER interference, the selective GPER antagonist G15, the epidermal growth factor receptor (EGFR) inhibitor AG1478, and the ERK1/2 inhibitor U0126. Importantly, TAM as well as G1 increased E₂ production in breast CAFs via GPER/EGFR/ERK signaling when the substrate of E₂, testosterone, was added to the medium. GPER-induced aromatase upregulation was probably responsible for this phenomenon, as TAM- and G1-induced CYP19A1 gene expression was reduced by GPER knockdown and G15, AG1478, and U0126 administration. Accordingly, GPER-mediated CAF-dependent estrogenic effects on the tumor-associated stroma are conceivable, and CAF is likely to contribute to breast cancer progression, especially TAM resistance, via a positive feedback loop involving GPER/EGFR/ERK signaling and E₂ production.
Chen Y, Li Z, He Y, et al.Estrogen and pure antiestrogen fulvestrant (ICI 182 780) augment cell-matrigel adhesion of MCF-7 breast cancer cells through a novel G protein coupled estrogen receptor (GPR30)-to-calpain signaling axis.
Toxicol Appl Pharmacol. 2014; 275(2):176-81 [PubMed
] Related Publications
Fulvestrant (ICI 182 780, ICI) has been used in treating patients with hormone-sensitive breast cancer, yet initial or acquired resistance to endocrine therapies frequently arises and, in particular, cancer recurs as metastasis. We demonstrate here that both 17-beta-estradiol (E2) and ICI enhance cell adhesion to matrigel in MCF-7 breast cancer cells, with increased autolysis of calpain 1 (large subunit) and proteolysis of focal adhesion kinase (FAK), indicating calpain activation. Additionally, either E2 or ICI induced down-regulation of estrogen receptor α without affecting G protein coupled estrogen receptor 30 (GPR30) expression. Interestingly, GPR30 agonist G1 triggered calpain 1 autolysis but not calpain 2, whereas ER agonist diethylstilbestrol caused no apparent calpain autolysis. Furthermore, the actions of E2 and ICI on calpain and cell adhesion were tremendously suppressed by G15, or knockdown of GPR30. E2 and ICI also induced phosphorylation of extracellular regulated protein kinases 1 and 2 (ERK1/2), and suppression of ERK1/2 phosphorylation by U0126 profoundly impeded calpain activation triggered by estrogenic and antiestrogenic stimulations indicating implication of ERK1/2 in the GPR30-mediated action. Lastly, the E2- or ICI-induced cell adhesion was dramatically impaired by calpain-specific inhibitors, ALLN or calpeptin, suggesting requirement of calpain in the GPR30-associated action. These data show that enhanced cell adhesion by E2 and ICI occurs via a novel GPR30-ERK1/2-calpain pathway. Our results indicate that targeting the GPR30 signaling may be a potential strategy to reduce metastasis and improve the efficacy of antiestrogens in treatment of advanced breast cancer.
Bechara EG, Sebestyén E, Bernardis I, et al.RBM5, 6, and 10 differentially regulate NUMB alternative splicing to control cancer cell proliferation.
Mol Cell. 2013; 52(5):720-33 [PubMed
] Related Publications
RBM5, a regulator of alternative splicing of apoptotic genes, and its highly homologous RBM6 and RBM10 are RNA-binding proteins frequently deleted or mutated in lung cancer. We report that RBM5/6 and RBM10 antagonistically regulate the proliferative capacity of cancer cells and display distinct positional effects in alternative splicing regulation. We identify the Notch pathway regulator NUMB as a key target of these factors in the control of cell proliferation. NUMB alternative splicing, which is frequently altered in lung cancer, can regulate colony and xenograft tumor formation, and its modulation recapitulates or antagonizes the effects of RBM5, 6, and 10 in cell colony formation. RBM10 mutations identified in lung cancer cells disrupt NUMB splicing regulation to promote cell growth. Our results reveal a key genetic circuit in the control of cancer cell proliferation.
BACKGROUND: RBM5 (RNA-binding motif protein 5, also named H37/LUCA-15) gene from chromosome 3p21.3 has been demonstrated to be a tumor suppressor. Current researches in vitro confirm that RBM5 can suppress the growth of lung adenocarcinoma cells by inducing apoptosis. There is still no effective model in vivo, however, that thoroughly investigates the effect and molecular mechanism of RBM5 on lung adenocarcinoma.
METHOD: We established the transplanted tumor model on BALB/c nude mice using the A549 cell line. The mice were treated with the recombinant plasmids carried by attenuated Salmonella to induce the overexpression of RBM5 in tumor tissues. RBM5 overexpression was confirmed by immunohistochemistry staining. H&E staining was performed to observe the histological performance on plasmids-treated A549 xenografts. Apoptosis was assessed by TUNEL staining with a TUNEL detection kit. Apoptosis-regulated genes were detected by Western blot.
RESULTS: We successful established the lung adenocarcinoma animal model in vivo. The growth of tumor xenografts was significantly retarded on the mice treated with pcDNA3.1-RBM5 carried by attenuated Salmonella compared to that on mice treated with pcDNA3.1. Overexpression of RBM5 enhanced the apoptosis in tumor xenografts. Furthermore, the expression of Bcl-2 protein was decreased significantly, while the expression of BAX, TNF-α, cleaved caspase-3, cleaved caspase-8, cleaved caspase-9 and cleaved PARP proteins was significantly increased in the pcDNA3.1-RBM5-treated mice as compared to that in the control mice.
CONCLUSIONS: In this study, we established a novel animal model to determine RBM5 function in vivo, and concluded that RBM5 inhibited tumor growth in mice by inducing apoptosis. The study suggests that although RBM5's involvement in the death receptor-mediated apoptotic pathway is still to be investigated, RBM5-mediated growth suppression, at least in part, employs regulation of the mitochondrial apoptotic pathways.
BACKGROUND: Recent studies have indicated that the nuclear RNA-binding protein RBM5 has the ability to modulate apoptosis and suppress tumor growth. The aim of this study is to investigate the expression of RBM5 in human prostate cancer and its mechanism of tumor suppression.
METHODS: The expression of RBM5 protein in cancerous prostatic tissues and normal tissues was examined by IHC. PC-3 cell line was used to determine the apoptotic function of RBM5 in vitro. PC-3 cells were transiently transfected with pcDNA3.1-RBM5. Cell viability was determined by MTT assay. Rhodamine 123 staining and Annexin V analysis were performed to observe the apoptotic activity of PC-3 cells overexpressing RBM5. Expression of apoptosis-related genes was assessed by western blot.
RESULTS: The expression of RBM5 protein was significantly decreased in cancerous prostatic tissues compared to the normal tissues. PC-3 cells overexpressing RBM5 showed not only significant growth inhibition compared with the vector controls, but also dysfunction of mitochondrial membrane potential and increased apoptotic activity. To further define RBM5 function in apoptotic pathways, we investigated differential expression profiles of various BH3-only proteins including Bid, Bad, and Bim, and apoptosis regulatory proteins include P53, cleaved caspase9, and cleaved caspase3. We found that the expression of both BH3-only proteins and apoptosis regulatory proteins was increased in RBM5 transfected cells.
CONCLUSION: The expression of RBM5 protein was significantly decreased in cancerous prostatic tissues, which suggests that RBM5 plays an important role in the pathogenesis of prostate cancer. RBM5 may induce the apoptosis of prostate cancer PC-3 cells by modulating the mitochondrial apoptotic pathway, and thus RBM5 might be a promising target for gene therapy on prostate cancer.
Masilamani TJ, Rintala-Maki ND, Wang K, Sutherland LCDownregulating activated epidermal growth factor receptor has no effect on RBM5 expression.
Chin Med J (Engl). 2012; 125(13):2378-81 [PubMed
] Related Publications
BACKGROUND: We were interested in determining how the tumor suppressor gene RBM5 is regulated in lung cancers. Previous studies suggested that the gene expression is related to histological subtype and smoking exposure, since in small cell lung cancers the RBM5 gene is deleted whereas in non-small cell lung carcinomas (NSCLC) RBM5 expression is reduced. Of particular interest was the recent finding that in lung adenocarcinomas, a histological subtype of NSCLC, smoking exposure correlated with mutational activity in the transforming growth factor alpha (TGF-a) signaling pathway. Lung adenocarcinomas from smokers were associated with activating KRAS mutations, whereas lung adenocarcinomas from never-smokers were associated with activating epidermal growth factor receptor (EGFR) mutations. We hypothesized that inhibition of RBM5 in lung adenocarcinomas is achieved indirectly via these activating mutations. The objective of the research described herein was to determine if EGFR activation and RBM5 expression are negatively correlated.
METHODS: EGFR expression in the lung adenocarcinoma cell line NCI-H1975 was inhibited using small interfering RNA. RBM5 expression was examined by real-time quantitative polymerase chain reaction and Western blotting.
RESULTS: Reduced EGFR expression did not correlate with any change in RBM5 expression at either the RNA or protein level.
CONCLUSION: These results suggest that RBM5 expression is not directly regulated by EGFR in non-smoker related lung adenocarinomas, and that some other mechanism operates to inhibit either the expression or function of this potential tumour suppressor in lung cancers that retain the RBM5 gene.
BACKGROUND: The loss of tumor suppressor gene (TSG) function is a critical step in the pathogenesis of human lung cancer. RBM5 (RNA-binding motif protein 5, also named H37/LUCA-15) gene from chromosome 3p21.3 demonstrated tumor suppressor activity. However, the role of RBM5 played in the occurrence and development of lung cancer is still not well understood.
METHOD: Paired non-tumor and tumor tissues were obtained from 30 adenocarcinomas. The expression of RBM5 mRNA and protein was examined by RT-PCR and Western blot. A549 cell line was used to determine the apoptotic function of RBM5 in vitro. A549 cells were transiently transfected with pcDNA3.1-RBM5. AnnexinV analysis was performed by flow cytometry. Expression of Bcl-2, cleaved caspase-3, caspase-9 and PAPP proteins in A549 lung cancer cells and the A549 xenograft BALB/c nude mice model was determined by Western blot. Tumor suppressor activity of RBM5 was also examined in the A549 xenograft model treated with pcDNA3.1-RBM5 plasmid carried by attenuated Salmonella typhi Ty21a.
RESULT: The expression of RBM5 mRNA and protein was decreased significantly in adenocarcinoma tissues compared to that in the non-tumor tissues. In addition, as compared to the vector control, a significant growth inhibition of A549 lung cancer cells was observed when transfected with pcDNA3.1-RBM5 as determined by cell proliferation assay. We also found that overexpression of RBM5 induced both early and late apoptosis in A549 cells using AnnexinV/PI staining as determined by flow cytometry. Furthermore, the expression of Bcl-2 protein was decreased, whereas the expression of cleaved caspase-3, caspase-9 and PARP proteins was significantly increased in the RBM5 transfected cells; similarly, expression of decreased Bcl-2 and increased cleaved caspase-3 proteins was also examined in the A549 xenograft model. More importantly, we showed that accumulative and stable overexpression of RBM5 in the A549 xenograft BALB/c nude mice model significantly inhibited the tumor growth rate in vivo as compared to that in the control.
CONCLUSION: Our study demonstrates that RBM5 can inhibit the growth of lung cancer cells and induce apoptosis both in vitro and in vivo, which suggests that RBM5 might be used as a potential biomarker or target for lung cancer diagnosis and chemotherapy. Moreover, we propose a novel animal model set up in BALB/c nude mice treated with attenuated Salmonella as a vector carrying plasmids to determine RBM5 function in vivo.
Li P, Wang K, Zhang J, et al.The 3p21.3 tumor suppressor RBM5 resensitizes cisplatin-resistant human non-small cell lung cancer cells to cisplatin.
Cancer Epidemiol. 2012; 36(5):481-9 [PubMed
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OBJECTIVE: Increasing RBM5 levels inhibit tumor cell growth and promote apoptosis. In this study, we investigated the role of RBM5 in the cisplatin resistance observed in human lung non-small cell lung cancer cells and evaluated the effect of RBM5 modulation on cell growth inhibition and apoptosis induced by cisplatin in the parental non-small cell lung cancer cells A549 and their cisplatin resistant counterparts, A549/DDP cells.
METHODS: RBM5 mRNA and protein expression in the A549 and A549/DDP cells was analyzed by semi-quantitative RT-PCR and western blot. The A549/DDP cells were then transfected with a pcDNA3-RBM5 plasmid, and an RBM5-specific siRNA was transfected into A549 cells, prior to treatment with cisplatin. Semi-quantitative RT-PCR and western blot analyses were performed to confirm the expression of RBM5 mRNA or protein, and knockdown of RBM5 mRNA or protein, respectively. MTT assays were used to evaluate chemosensitivity to cisplatin. Apoptosis was assessed by DAPI nuclear staining and flow cytometric analysis with an Annexin-V-FITC apoptosis kit. Cytosolic cytochrome c, cleaved caspase-3 and cleaved caspase-9 were detected by western blot.
RESULTS: The expression of RBM5 mRNA and protein was significantly reduced in the A549/DDP cells compared with the A549 cells. Exogenous expression of RBM5 by the pcDNA3-RBM5 resensitized the response of A549/DDP to cisplatin, resulting in a significant increase in tumor-suppressing activity induced by cisplatin. In contrast, downregulation of RBM5 with siRNA in the A549 cells inhibited cisplatin-induced apoptosis. We also found that the RBM5-enhanced chemosensitivity was associated with the release of cytochrome c into the cytosol, activation of caspase-9 and the downstream marker caspase-3.
CONCLUSION: Our results demonstrate that RBM5 may serve as a biomarker with the ability to predict a response to cisplatin. It may also act as a prognostic indicator in lung cancer patients. Our findings suggest that there may be clinical utility for ectopic RBM5 such as enhancing and resensitizing nonresponders to cisplatin.
BACKGROUND: RNA binding motif 5 (RBM5) is a tumor suppressor gene that modulates apoptosis through the regulation of alternative splicing of apoptosis-related genes. This study aimed to detect RBM5 expression in non-small cell lung cancer (NSCLC) and to associate RBM5 expression with clinicopathological data from NSCLC patients and EGFR and KRAS expression to better understand the potential role of RBM5 in NSCLC.
METHOD: Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting were performed to detect expression of mRNA and protein, respectively, of RBM5, EGFR and KRAS in 120 paired non-tumor and tumor samples of NSCLC.
RESULTS: The data showed that expression of RBM5 mRNA and protein was significantly reduced in NSCLC compared to normal tissues, whereas expression of both EGFR and KRAS genes was increased in NSCLC compared to normal tissues. Furthermore, the reduced RBM5 protein expression correlated with smoking status, tumor stage and lymph node metastasis of NSCLC, while overexpression of EGFR and KRAS proteins correlated with tumor stage and lymph node metastasis of NSCLC. Overexpression of KRAS protein was more frequent in smokers with NSCLC. In addition, expression of RBM5 mRNA and protein was negatively correlated with expression of EGFR and KRAS mRNA and protein in NSCLC tissues.
CONCLUSION: This study suggests further evaluation of RBM5 expression is warranted for use of RBM5 as a biomarker for NSCLC patients.
Notas G, Kampa M, Pelekanou V, Castanas EInterplay of estrogen receptors and GPR30 for the regulation of early membrane initiated transcriptional effects: A pharmacological approach.
Steroids. 2012; 77(10):943-50 [PubMed
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Estrogens exert their effect through ERα and ERβ intracellular transcription factors and rapid, usually membrane-initiated receptors, influencing cytosolic signaling and transcription. The nature of extranuclear estrogen elements has not been elucidated so far; classical or alternatively transcribed ER isoforms (ERα36, ERα46) anchored to the plasma membrane and GPR30 (GPER1) have been reported to exert early estrogen actions. Here, we used E2-BSA, an impermeable estradiol analog for a transcriptome analysis in four GREP1 positive breast cancer cell lines with different estrogen receptor profiles (T47D, MCF-7, MDA-MB-231 and SKBR3) in order to evaluate GPER1 transcriptional effects. Early effects of E2-BSA were assayed after 3h of incubation, in the absence/presence of ICI182,780 (ER-inhibitor) or G15 (GREP1-specific inhibitor). E2-BSA specifically modified 277-549 transcripts in the different cell lines. Two different clusters of transcripts could be identified: (1) the majority of transcripts were inhibited by both ICI182,780 and G15, suggesting an interaction of E2-BSA with a common ER-related element, or a direct ER-GPER1 interaction; (2) a small number of G15-only modified transcripts, in two cell lines (T47D and SKBR3 cells), indicative of specific GPER1-related effects. The latter transcripts were significantly related to pathways including FOXA2/FOXA3 transcription factor networks, RNA-Polymerases Transcription Regulation and lipid metabolism, while ICI/G15 inhibited transcripts affected pathways related to apoptosis, erythropoietin signaling, metabolic effects through the citric acid cycle, IL-4 and IL-5 mediated events and homologous DNA recombination. Finally, we review the current literature of GPER1 actions, in view of our results of ER-dependent and independent GPER1-modified pathways.
BACKGROUND: Most patients with ovarian cancer are diagnosed with advanced stage disease (i.e., stage III-IV), which is associated with a poor prognosis. Differentially expressed genes (DEGs) in stage III serous ovarian carcinoma compared to normal tissue were screened by a new differential display method, the annealing control primer (ACP) system. The potential targets for markers that could be used for diagnosis and prognosis, for stage III serous ovarian cancer, were found by cluster and survival analysis.
METHODS: The ACP-based reverse transcriptase polymerase chain reaction (RT PCR) technique was used to identify DEGs in patients with stage III serous ovarian carcinoma. The DEGs identified by the ACP system were confirmed by quantitative real-time PCR. Cluster analysis was performed on the basis of the expression profile produced by quantitative real-time PCR and survival analysis was carried out by the Kaplan-Meier method and Cox proportional hazards multivariate model; the results of gene expression were compared between chemo-resistant and chemo-sensitive groups.
RESULTS: A total of 114 DEGs were identified by the ACP-based RT PCR technique among patients with stage III serous ovarian carcinoma. The DEGs associated with an apoptosis inhibitory process tended to be up-regulated clones while the DEGs associated with immune response tended to be down-regulated clones. Cluster analysis of the gene expression profile obtained by quantitative real-time PCR revealed two contrasting groups of DEGs. That is, a group of genes including: SSBP1, IFI6 DDT, IFI27, C11orf92, NFKBIA, TNXB, NEAT1 and TFG were up-regulated while another group of genes consisting of: LAMB2, XRCC6, MEF2C, RBM5, FOXP1, NUDCP2, LGALS3, TMEM185A, and C1S were down-regulated in most patients. Survival analysis revealed that the up-regulated genes such as DDAH2, RNase K and TCEAL2 might be associated with a poor prognosis. Furthermore, the prognosis of patients with chemo-resistance was predicted to be very poor when genes such as RNase K, FOXP1, LAMB2 and MRVI1 were up-regulated.
CONCLUSION: The DEGs in patients with stage III serous ovarian cancer were successfully and reliably identified by the ACP-based RT PCR technique. The DEGs identified in this study might help predict the prognosis of patients with stage III serous ovarian cancer as well as suggest targets for the development of new treatment regimens.
Oh JJ, Taschereau EO, Koegel AK, et al.RBM5/H37 tumor suppressor, located at the lung cancer hot spot 3p21.3, alters expression of genes involved in metastasis.
Lung Cancer. 2010; 70(3):253-62 [PubMed
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The RBM5/H37 gene is located at the most 'sought-after' tumor suppressor locus in lung cancer, 3p21.3. This region of most frequent chromosomal deletion found at the earliest stage in lung cancer development houses 19 genes, many of which may act together as a 'tumor suppressor group', representing one of the most promising opportunities for development of new diagnostics/prognostics and therapeutics for lung cancer as well as for many other types of cancers. For the past decade, we have demonstrated tumor suppressor function of RBM5 in vitro and in vivo involving cell cycle arrest and apoptosis, as well as loss of RBM5 mRNA and protein expression in primary lung tumors. Here we report our latest data suggesting that RBM5 may regulate inhibition of metastasis in lung cancer. We performed cDNA microarray to identify global gene expression changes caused by RBM5 gene knockdown. In order to identify "consensus" pathways consistently deregulated by RBM5 loss irrespective of genetic background, the experiments were repeated in three different lung cancer cell lines of varying RBM5 expression levels, a normal lung epithelial cell line, and a normal breast epithelial cell line. Both Gene Set Enrichment Analysis (GSEA) and individual gene analysis identified consistent, statistically significant gene expression changes common to all five cell pairs examined. Genes involved in the functions of cell adhesion, migration and motility, known to be important in the metastatic process, were upregulated with RBM5-knockdown. These genes include Rac1, β-catenin, collagen, laminin and the overall gene set of the gene ontology group "proteinaceous extracellular matrix". Among these, we have focused on Rac1 and β-catenin which play essential roles in cell movement downstream of Wnt signaling. We have confirmed increased protein expression of β-catenin and increased protein activation of Rac1 with RBM5-knockdown. In addition, we found that RBM5 protein expression loss in primary lung tumors is correlated with increased lymph node metastasis in a small number of lung cancer patients. These data are corroborated by an independent report showing RBM5 as part of a 17-gene signature of metastasis in primary solid tumors. Taken together, the accumulated evidence suggests that RBM5 expression loss may increase the metastatic potential of tumors. Further study is warranted to evaluate the potential clinical utility of RBM5 in lung cancer diagnostics, prognostics and therapeutics.
Sutherland LC, Wang K, Robinson AGRBM5 as a putative tumor suppressor gene for lung cancer.
J Thorac Oncol. 2010; 5(3):294-8 [PubMed
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RBM5 is one member of a group of structurally related genes that includes RBM6 and RBM10. RBM10 maps to Xp11.23, and one allele is inactivated as a result of X chromosome inactivation. Both RBM5 and RBM6 map to 3p21.3, a tumor suppressor region that experiences loss of heterozygosity in the majority of lung cancers. Overexpression of RBM5, which encodes an RNA-binding protein involved in the regulation of alternative splicing and retards ascites associated tumor growth in immunocompromised mice, a phenomenon that may be related to an associated ability to modulate apoptosis. As part of our quest to gain a better understanding of how the proapoptotic activity of RBM5 might contribute to tumor suppressor function, we reviewed all the literature relating to RBM5 expression, with a focus on lung cancer. On the basis of the existing data, we suggest that-to more thoroughly assess the potential involvement of RBM5 as a lung cancer regulatory protein-more research is required regarding (a) the expression of not only full-length RBM5 but all of the alternate variants associated with the locus, in relation to histologic subtype and smoking history, and (b) the mutation status of various genes within the transforming growth factor-alpha signaling pathway, which may function to either directly or indirectly regulate RBM5 activity in RBM5-retaining lung cancers.
Similar to many genes involved in programmed cell death (PCD), the caspase 2 (casp-2) gene generates both proapoptotic and antiapoptotic isoforms by alternative splicing. Using a yeast RNA-protein interaction assay, we identified RBM5 (also known as LUCA-15) as a protein that binds to casp-2 pre-mRNA. In both transfected cells and in vitro splicing assay, RBM5 enhances the formation of proapoptotic Casp-2L. RBM5 binds to a U/C-rich sequence immediately upstream of the previously identified In100 splicing repressor element. Our mutagenesis experiments demonstrate that RBM5 binding to this intronic sequence regulates the ratio of proapoptotic/antiapoptotic casp-2 splicing isoforms, suggesting that casp-2 splicing regulation by RBM5 may contribute to its tumor suppressor activity. Our work has uncovered a player in casp-2 alternative splicing regulation and revealed a link between the alternative splicing regulator and the candidate tumor suppressor gene. Together with previous studies, our work suggests that splicing control of cell death genes may be an important aspect in tumorigenesis. Enhancing the expression or activities of splicing regulators that promote the production of proapoptotic splicing isoforms might provide a therapeutic approach to cancer.