Search

Background The gene encoding the E3 ubiquitin ligase substrate-binding adaptor SPOP is frequently mutated in primary prostate cancer, but how SPOP mutations contribute to prostate cancer pathogenesis remains poorly understood. Stress granules (SG) assembly is an evolutionarily conserved strategy for survival of cells under stress, and often upregulated in human cancers. We investigated the role of SPOP mutations in aberrant activation of the SG in prostate cancer and explored the relevanve of the mechanism in therapy resistance. Methods We identified SG nucleating protein Caprin1 as a SPOP interactor by using the yeast two hybrid methods. A series of functional analyses in cell lines, patient samples, and xenograft models were performed to investigate the biological significance and clinical relevance of SPOP regulation of SG signaling in prostate cancer. Results The cytoplasmic form of wild-type (WT) SPOP recognizes and triggers ubiquitin-dependent degradation of Caprin1. Caprin1 abundance is elevated in SPOP-mutant expressing prostate cancer cell lines and patient specimens. SPOP WT suppresses SG assembly, while the prostate cancer-associated mutants enhance SG assembly in a Caprin1-dependent manner. Knockout of SPOP or expression of prostate cancer-associated SPOP mutants conferred resistance to death caused by SG inducers (e.g. docetaxel, sodium arsenite and H2O2) in prostate cancer cells. Conclusions SG assembly is aberrantly elevated in SPOP-mutated prostate cancer. SPOP mutations cause resistance to cellular stress induced by chemtherapeutic drug such as docetaxel in prostate cancer.

MicroRNA-34a (miR-34a) is a tumor suppressive microRNA, which induces G1 arrest, apoptosis and senescence by repressing the expression of multiple oncogenes. This study aimed to investigate the biological function and molecular mechanisms of miR-34a in human renal cell carcinoma (RCC) cells. Quantitative polymerase chain reaction (qPCR) revealed that miR-34a expression was significantly downregulated in eight of the 10 (80%) RCC tissues compared with adjacent normal tissues. In RCC cell lines, several other target genes of miR-34a were dysregulated at the mRNA level when the expression of miR-34a was elevated. In addition, western blot analysis and qPCR revealed that forced expression of miR-34a downregulated the expression of Notch1 at the protein and mRNA level. The Cell Counting Kit-8 identified that transient forced expression of miR-34a inhibited cell growth and resulted in cell cycle arrest, which was evaluated by flow cytometry. Our data demonstrated that miR-34a inhibits cell proliferation by downregulating Notch1 in RCC cell lines.

Clear cell renal cell carcinoma (ccRCC) is the most common primary kidney cancer in adults, and the identification of biomarkers involved in the pathogenesis and prognosis of ccRCC is crucial for early diagnosis and anticancer treatment. In this study, we demonstrate that thioredoxin domain-containing protein 5 (TXNDC5) expression is markedly upregulated in ccRCC tissues in comparison with adjacent non-cancerous tissues through quantitative RT-PCR, Western blotting, and immunohistochemical analyses. Importantly, TXNDC5 expression is negatively correlated with the overall survival of patients. Knockdown of TXNDC5 by siRNAs inhibits the cell growth, migration, and invasion of ccRCC cells as well as sensitizes ccRCC cells to chemotherapeutic drugs, such as Camptothecin and 5-Fluorouracil. Moreover, we used complementary DNA (cDNA) microarray analyses to explore the underlying molecular mechanisms of TXNDC5 in the pathogenesis of ccRCC. We demonstrate that knockdown of TXNDC5 affects the messenger RNA (mRNA) and protein levels of numerous important genes associated with tumorigenesis. In summary, our findings indicate that TXNDC5 performs an essential function in ccRCC pathogenesis and can serve as a novel prognostic marker of ccRCC.

Ubiquitin-like with PHD and RING finger domain 1 (UHRF1) is a multi-domain ubiquitin E3 ligase that plays critical roles in regulation of DNA methylation and histone ubiquitination. In this study, we found UHRF1 is frequently overexpressed in human clear cell Renal Cell Carcinoma (ccRCC) tissues both at mRNA and protein levels. We showed that UHRF1 directly interacts with p53 both in vivo and in vitro. A new domain (PD) in UHRF1 was required for interaction with p53. We found that UHRF1 down-regulates p53 transactivation activity which was depends on the ubiquitin E3 ligase function. UHRF1 can promote non-degradative ubiquitination of p53, suppress p53 pathway activation and p53-dependent apoptosis in ccRCC cells. Together, our study suggests that UHRF1, which overexpressed ccRCC, may act as a p53 regulator, suppress p53 pathway activation and help ccRCC cells to escape from p53-dependent apoptosis.

Background Renal cell carcinoma (RCC) is characterized by inherent resistance to chemotherapy. Earlier studies demonstrated that microRNAs (miRNAs) might be involved in the chemosensitivity of cancers. MicroRNA let-7, a putative tumor suppressor, is dysregulated in many cancers. Our study aims to investigate the exact role of let-7 in chemotherapy sensitivity of 5-fluorouracil (5-FU) in RCC. Methods The clinical significance of let-7b and let-7c expression in surgically resected specimens was assessed by qRT-PCR. Cell proliferation assay and colony formation assay were used to assess the survival of 786-O cells treated with let-7b or let-7c combined with 5-FU. Western blot was used to detect the expression of Akt2 and caspase-7. Luciferase assay was used to detect the direct binding of let-7b and let-7c to the 3′-untranslated region (UTR) of Akt2. Results Expression of let-7b and let-7c was significantly decreased in 32 paired clear cell renal cell carcinoma tissue specimens and the dysregulation of let-7b was associated with pathological grade. Transfection of let-7b or let-7c combined with 5-FU inhibited proliferation and potentiated the antitumor efficacies of 5-FU at tolerated concentration. let-7b and let-7c suppressed the luciferase activity of reporter plasmid containing the 3′-UTR of Akt2. Overexpression of let-7b and let-7c reduced Akt2 expression, and Akt2 inhibition enhanced the sensitivity to 5-FU by affecting apoptotic pathway. Conclusions Expression of let-7b and let-7c was frequently decreased in clear cell renal cell carcinoma tissues. The dysregulation of let-7b and let-7c may be involved in chemoresistance of RCC cells to 5-FU by down-regulating Akt2. Electronic supplementary material The online version of this article (doi:10.1186/s12957-015-0596-4) contains supplementary material, which is available to authorized users.