Hypoxia‐induced downregulation of miR‐30c promotes epithelial‐mesenchymal transition in human renal cell carcinoma

Abstract

MicroRNAs (miRNAs), which negatively regulate protein expression by binding protein-coding mRNAs, have been integrated into cancer development and progression as either oncogenes or tumor suppressor genes. miR-30c was reported to be downregulated in several types of cancer. However, its role in human renal cell carcinoma (RCC) remains largely unknown. Here, we show that miR-30c is significantly downregulated in human RCC tissues and cell lines. We found that miR-30c downregulation could be induced by hypoxia in RCC cells in a hypoxia-inducible factors (HIFs) dependent manner. Repression of miR-30c through its inhibitor resulted in reduction of E-cadherin production and promotion of epithelial-mesenchymal transition (EMT), while overexpression of miR-30c inhibited EMT in RCC cells. We identified Slug as a direct target of miR-30c in RCC cells. Slug was upregulated in RCC tissues and its expression could be induced by hypoxia, which is consistent with downregulation of miR-30c by hypoxia. Forced overexpression of Slug in 786-O cells reduced E-cadherin production, and promoted EMT as well as cell migration. Moreover, Slug overexpression abrogated the inhibitory role of miR-30c in regulating EMT and cell migration, indicating miR-30c regulates EMT through Slug in RCC cells. Our findings propose a model that hypoxia induces EMT in RCC cells through downregulation of miR-30c, which leads to subsequent increase of Slug expression and repression of E-cadherin production, and suggest a potential application of miR-30c in RCC treatment. (Cancer Sci 2013; 104: 1609-1617 R enal cell carcinoma (RCC), the most common type of kidney cancer, is one of the leading causes of cancer deaths in western countries, and the overall incidence of RCC is steadily increasing.(1) Despite more than 50% of renal tumors being detected incidentally due to advances in diagnosis, especially improved imaging techniques, about 20-30% of all patients are diagnosed with metastatic disease. In addition, another 20% of patients undergoing nephrectomy will develop metastatic RCC during follow-up. For patients with metastatic RCC, the prognosis is extremely poor, despite multimodal treatment.(2) Therefore, a major challenge for improving clinical outcomes is to understand molecular mechanisms of RCC in detail and search for molecular therapeutic targets.MicroRNAs (miRNAs) are small non-coding RNAs in the size range of 19-25 nucleotides that are cleaved from hairpin pre-miRNA precursors. By binding to imperfect complementary sequences in the 3′-untranslated region (3′UTR) of target mRNAs, miRNAs cause translational repression or mRNA degradation. miRNAs play critical roles in a wide variety of biological process including cell differentiation, proliferation, apoptosis and metabolism. (3,4) Notably, dysregulation of miRNAs has been extensively implicated in cancer pathogenesis in various tumor types.(5) They can act as potential oncogenes or tumor suppressor genes during cancer initiation and progression.(6,7) Accumulating evidence shows that miRNAs play r...

Hypoxia: a key player in antitumor immune response. A Review in the Theme: Cellular Responses to Hypoxia

“…Cells experiencing EMT can also reactivate stem cell-associated self-renewal programs, which suppose some degrees of plasticity (66). Several reports suggest that hypoxia promotes EMT in various cancer types, including prostate, breast, renal, pancreatic, myeloma, lung, ovarian, and squamous carcinoma (6,46,62,64,97,100,108). Experimental studies have revealed that the stabilization of HIF-1␣ by hypoxia can directly or indirectly stimulate the expression of several E-box-binding transcription factors known to regulate EMT, including TWIST1, ZEB2, and SNAIL (64,90,121,124), while discrepancies among models suggest context-dependent events.…”

The epigenetic landscape of renal cancer

“…High levels of VEGF, which can be secreted by RCC cells, promote the development of new blood vessels that associate with the tumour, and can also act in an autocrine manner to increase tumour cell migration and invasiveness 198 . miR-141, 200a, 200b and 200c) is among the most frequently downregulated group of mi RNAs in RCC [199][200][201][202][203] . This miRNA family and miR-30c are involved in the regulation of EMT [199][200][201][202][203] .…”

“…miR-141, 200a, 200b and 200c) is among the most frequently downregulated group of mi RNAs in RCC [199][200][201][202][203] . This miRNA family and miR-30c are involved in the regulation of EMT [199][200][201][202][203] . Their expression can be inhibited by TGFβ signalling, leading to reduced expression of ZEB1, ZEB2 and SIP1 (REFS 199,200,202), which transcriptionally repress E-cadherin and induce EMT 106,107 (FIG.…”

miR‑514a‑3p functions as a tumor suppressor in renal cell carcinoma

“…MicroRNAs (miRNAs/miRs) are a class of non-coding RNAs with a length of ~22 nucleotides (7,8). They regulate gene expression post-transcriptionally by imperfectly binding with the 3'-untranslated region (3'UTR) of targeted messenger RNAs (mRNAs) to suppress translation or induce mRNA degradation (7).…”