AT-rich Interaction Domain 1A Gene Variations: Genetic Associations and Susceptibility to Gastric Cancer Risk

Implication of ARID1A Undercurrents and PDL1, TP53 Overexpression in Advanced Gastric Cancer

AT-rich interactive domain-containing protein 1A (ARID1A), TP53 and programmed cell death-ligand 1 (PDL1) are involved in several protein interactions that regulate the expression of various cancer-related genes involved in the progression of the cell cycle, cell proliferation, DNA repair, and apoptosis. In addition, gene expression analysis identified some common downstream targets of ARID1A and TP53. It has been established that tumors formed by ARID1A-deficient cancer cells exhibited elevated PDL1 expression. However, the aberrations in these molecules have not been studied in this population especially in Gastric Cancer (GC). In this backdrop we aimed to investigate the role of the ARID1A mutation and expression of ARID1A, TP53 and PDL1 genes in the etiopathogenesis of Gastric Cancer (GC) in the ethnic Kashmiri population (North India). The study included 103 histologically confirmed GC cases. The mutations, if any, in exon-9 of ARID1A gene was analysed by Polymerase Chain Reaction (PCR) followed by Sanger sequencing. The mRNA expression of the ARID1A, TP53 and PDL1 genes was analysed by Quantitative real time-PCR (qRT-PCR). We identified a nonsense mutation (c.3219; C > T) in exon-9 among two GC patients (∼2.0%), which introduces a premature stop codon at protein position 1073. The mRNA expression of the ARID1A, TP53 and PDL1 gene was significantly reduced in 25.3% and elevated in 47.6 and 39.8% of GC cases respectively with a mean fold change of 0.63, 2.93 and 2.43. The data revealed that reduced mRNA expression of ARID1A and elevated mRNA expression of TP53 and PDL1 was significantly associated with the high-grade and advanced stage of cancer. Our study proposes that ARAD1A under-expression and overexpression of TP53 and PDL1 might be crucial for tumor progression with TP53 and PDL1 acting synergistically.

Genetic association of ARID5B with the risk of colorectal cancer within Jammu and Kashmir, India

Colorectal cancer (CRC), which includes the development of cancer from the colon or rectum, is one of the highly prevalent cancers in the populations of Jammu and Kashmir (J&K) in India. However, case-control genetic association studies on CRC are lacking in this population. Various genome-wide association studies have previously shown that single-nucleotide polymorphisms (SNPs) of the AT-rich interaction domain 5B (ARID5B) gene located on chromosome 10q21.2 contribute substantially to the development of colorectal cancer. The association between ARID5B and CRC risk in north Indian population groups is still unknown. To understand the role of ARID5B SNPs in CRC in the population of J&K, we designed a case-control study to investigate the association of the cancer susceptibility variant rs10740055 of ARID5B with CRC in the population of J&K. The study included 180 cases and 390 healthy controls. Genotyping of the rs10740055 variant was performed by RT-PCR using the TaqMan assay technique. Hardy-Weinberg equilibrium of the variant was assessed using the chi-squared test. The allele- and genotype-specific risks were estimated by odds ratios (ORs) with 95% confidence intervals (CIs). The rs10740055 variant showed a higher risk for colorectal cancer with an OR of 3.35 (1.99-5.65 at 95% CI) and P = 0.000005 corrected for age, gender, ethnicity, BMI, alcohol intake and smoking. Our results indicate that the A allele of rs10740055 imparts risk to the population and also that a larger sample size is needed for further statistical validation. The association of other variants in other ARID family genes should also be tested as their role cannot be ruled out.

ARID1 proteins: from transcriptional and post-translational regulation to carcinogenesis and potential therapeutics

The ARID1 proteins are mutually exclusive subunits of the BRG1/BRM-associated factor (BAF) complexes that play an important role in chromatin remodeling and regulate many fundamental cell functions. The role of ARID1s is well defined as a tumor-suppressive. The cancer cells evolve different mechanisms to downregulate ARID1s and inactivate their functions. ARID1s are frequently mutated in human cancer. The recent findings of ARID1A/B downregulation at transcriptional and translational levels along with their low levels in human cancers indicate the significance of regulatory mechanisms of ARID1s in cancers. In this review, we present the current knowledge on the regulation and alterations of ARID1 protein expression in human cancers and indicate the importance of regulators of ARID1s as a prognostic marker and in potential therapeutic strategies.