Association between Arsenic Level, Gene Expression in Asian Population, and In Vitro Carcinogenic Bladder Tumor

The IARC classified arsenic (As) as “carcinogenic to humans.” Despite the health consequences of arsenic exposure, there is no molecular signature available yet that can predict when exposure may lead to the development of disease. To understand the molecular processes underlying arsenic exposure and the risk of disease development, this study investigated the functional relationship between high arsenic exposure and disease risk using gene expression derived from human exposure. In this study, a three step analysis was employed: (1) the gene expression profiles obtained from two diverse arsenic-exposed Asian populations were utilized to identify differentially expressed genes associated with arsenic exposure in human subjects, (2) the gene expression profiles induced by arsenic exposure in four different myeloma cancer cell lines were used to define common genes and pathways altered by arsenic exposure, and (3) the genetic profiles of two publicly available human bladder cancer studies were used to test the significance of the common association of genes, identified in step 1 and step 2, to develop and validate a predictive model of primary bladder cancer risk associated with arsenic exposure. Our analysis shows that arsenic exposure to humans is mainly associated with organismal injury and abnormalities, immunological disease, inflammatory disease, gastrointestinal disease, and increased rates of a wide variety of cancers. In addition, arsenic exerts its toxicity by generating reactive oxygen species (ROS) and increasing ROS production causing the imbalance that leads to cell and tissue damage (oxidative stress). Oxidative stress activates inflammatory pathways leading to transformation of a normal cell to tumor cell specifically; there is significant evidence of the advancing changes in oxidative/nitrative stress during the progression of bladder cancer. Therefore, we examined the relation of differentially expressed genes due to exposure of arsenic in human and bladder cancer and developed a bladder cancer risk prediction model. In this study, integrin-linked kinase (ILK) was one of the most significant pathways identified between both arsenic exposed population which plays a key role in eliciting a protective response to oxidative damage in epidermal cells. On the other hand, several studies showed that arsenic trioxide (ATO) is useful for anticancer therapy although the mechanisms underlying its paradoxical effects are still not well understood. ATO has shown remarkable efficacy for the treatment of multiple myeloma; therefore, it will be helpful to understand the underlying cancer biology by which ATO exerts its inhibitory effect on the myeloma cells. Our study found that MAPK is one of the most active network between arsenic gene and ATO cell line which is involved in indicative of oxidative/nitrosative damage and well associated with the development of bladder cancer. The study identified a unique set of 147 genes associated with arsenic exposure and linked to molecular mechanisms of cancer. The risk prediction model shows the highest prediction ability for recurrent bladder tumors based on a very small subset (NKIRAS2, AKTIP, and HLA-DQA1) of the 147 genes resulting in AUC of 0.94 (95% CI: 0.744-0.995) and 0.75 (95% CI: 0.343-0.933) on training and validation data, respectively.

Alternative Splicing Related Genetic Variants in lncRNA BCLETare Associated with Bladder Cancer Risk in the Chinese Population

Background: Although thousands of alternative splicing related single nucleotide polymorphisms (AS-SNPs) have been uncovered in human tumors, the potential function of AS-SNPs involved in bladder cancer is rarely reported. Here we identified bladder cancer risk-associated AS-SNPs and revealed its underlying causal mechanism in bladder carcinogenesis.Methods: Variants with annotation of “splice-3” or “splice-5” were extracted as AS-SNPs through the database of Single Nucleotide Polymorphism (dbSNP). Two-stage case-control studies comprising 1,630 cases and 2,504 controls were conducted to assess the association between the AS-SNPs and bladder cancer risk. A series of experiments including luciferase reporter assays, RNA immunoprecipitation, and malignant phenotype were performed to comprehensively investigate the genetic and epigenetic biological effects of AS-SNPs in the development of bladder cancer.Results: We identified the potential causal variant rs558814 A>G located in intron of lncRNA BCLET (Bladder Cancer Low-Expressed Transcript) was significantly associated with a reduced risk of bladder cancer [odds ratio (OR) = 0.84, 95% confidence interval (CI) = 0.76 to 0.92, P = 3.26 × 10−4]. The SNP rs558814 exerted transcriptional activity regulatory effect and thus facilitated the expression of BCLET transcripts including BCLET-long and BCLET-short. In addition, both BCLET transcripts overexpression remarkably inhibited in vitro and in vivo bladder cancer phenotypes including cell proliferation, clone formation, invasion, migration and apoptosis. Mechanistically, lncRNA BCLET bound to MSANTD2 mRNA, masked splicing site of MSANTD2 mRNA, and thereby facilitated the expression of MSANTD2-004 transcript, which lacks the first exon and remarkably inhibited the progression of bladder cancer.Conclusions: Our findings not only revealed the important role of AS related genetic variants rs558814 and its associated gene BCLET in bladder cancer progression, but also provided the perspective to understand the etiology and pathology of cancers from the alternative splicing regulation mechanism.

Association of Dietary Carrot Intake With Bladder Cancer Risk in a Prospective Cohort of 99,650 Individuals With 12.5 Years of Follow-Up

Previous studies have provided limited evidence for the effect of carrot intake on bladder cancer incidence. This study aimed to evaluate the association between carrot consumption and bladder cancer risk in the Prostate, Lung, Colorectal, and Ovarian Cancer (PLCO) Screening cohort. PLCO enrolled 154,897 participants between November 1993 and July 2001 from 10 clinical screening centers throughout the United States. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox regression model adjusting for confounders. A meta-analysis was also performed based on all available prospective studies with DerSimonian and Laird random-effects model to calculate summary relative risk (RR) and 95% CI. After a median of 12.5 years of follow-up, 762 incident bladder cancer cases occurred. We found no statistically significant association between dietary carrot intake and bladder cancer risk. The multivariate-adjusted HR of bladder cancer for participants in the highest category of total carrot intake compared with those in the lowest category was 0.96 (95% CI: 0.76–1.22; P for trend = 0.436). Corresponding adjusted HR was 0.98 (95% CI 0.90–1.06) per 1 SD increment of carrot intake. A meta-analysis based on two previous cohort studies and our study also found no significant association between carrot intake and bladder cancer risk (Summary HR 1.02, 95% CI 0.95–1.10) without obvious heterogeneity between studies (P = 0.859, I2 = 0.0%). In summary, analysis of the PLCO cohort did not provide evidence that dietary consumption of carrot was associated with the risk of bladder cancer.