The joint effects of arsenic and risk diplotypes of insulin-like growth factor binding protein-3 in renal cell carcinoma

miRNA-182-5p, via HIF2α, contributes to arsenic carcinogenesis: evidence from human renal epithelial cells

Chronic exposure to high levels of arsenic has been associated with high risks for many cancers, including renal cell carcinoma (RCC). However the underlying mechanisms are not clear. In the present study, chronic arsenite exposure (2 μM or 5 μM, 30 weeks) induced malignant transformation of HK-2 human renal epithelial cells as indicated by elevated colony formation (6.2- and 5.4-fold increase, respectively), secreted MMP-9 activity (10.1- and 11.3-fold increase, respectively) and proliferation rate (1.2- and 1.3-fold increase in 72 h, respectively). Lipid accumulation, typical of clear cell RCC, was observed in arsenic-transformed (As-TM) cells. Overexpression of hypoxia-inducible factor 2α (HIF2α) and suppression of carnitine palmitoyltransferase 1A (CPT1A) were found at the level of mRNA (1.5- and 0.49-fold of control, respectively) and protein (4.0- and 0.28-fold of control, respectively) after exposure to 2 μM arsenite for 20 weeks. Silencing of HIF2α significantly attenuated arsenite-induced malignant phenotypes and lipid accumulation. Inactivation of Von Hippel-Lindau (VHL) and impaired protein degradation of HIF2α were not found in As-TM cells. Expression of miR-182-5p and miR-802 in As-TM cells was 42.4% and 54.0% of control, respectively (p < 0.05). The levels of mRNA and protein of HIF2α were increased 2.4 folds and 1.6 folds of negative control in response to the miR-182-5p inhibitor, respectively, but decreased to 58.1% and 50.1% of negative control in response to miR-182-5p mimics, respectively. No significant alteration was observed in HIF2α expression when miR-802 was silenced. Our data provide further evidence for the carcinogenic role of arsenic in the kidney. Moreover, the miR-182-5p/HIF2α pathway is indicated to be involved in malignant transformation of human renal epithelial cells under arsenite exposure.

Adiponectin gene polymorphisms and obesity increase the susceptibility to arsenic-related renal cell carcinoma

Our recent study found that high urinary total arsenic levels were associated with renal cell carcinoma (RCC). Recent studies demonstrated that low circulating adiponectin was related to RCC. The aim of the present study was to explore the relationship between adiponectin gene (ADIPOQ) polymorphisms and RCC and investigate whether individuals with an ADIPOQ risk genotype, obesity, and high urinary total arsenic levels have a modified odds ratio (OR) of RCC. A total of 389 RCC patients and 389 age- and sex-matched controls were recruited between November 2006 and December 2012 in Taiwan. Image-guided biopsy or surgical resection of renal tumors was performed to pathologically verify RCC. Genomic DNA was used to examine the genotypes of the ADIPOQ rs182052, ADIPOQ rs2241766, ADIPOQ rs1501299, and ADIPOQ rs1063539 SNPs by PCR-RFLP. HPLC-HG-AAS was used to measure the concentrations of urinary arsenic species. Participants with the ADIPOQ rs182052 G/A+A/A genotype had a significantly higher OR of RCC compared with those with the ADIPOQ rs182052 G/G genotype. The OR (95% confidence interval [CI]) was 1.70 (1.23-2.36). The OR of RCC for the combined effect of high urinary total arsenic levels and obesity, which was dose-dependent, in individuals with the ADIPOQ rs182052 G/A+A/A genotype was 9.33 (3.85-22.62). The present study found significant combined effects of obesity and the ADIPOQ rs182052 G/A+A/A genotype on the arsenic-related risk of RCC in a population with low arsenic exposure. Arsenic exposure, obesity, and the ADIPOQ rs182052 polymorphism could be predictors of a higher OR of RCC.