Role of GSTP1 functional polymorphisms in molecular pathogenesis of colorectal cancer

Glutathione S-transferase P1 (GSTP1) plays a crucial role in the detoxification of harmful substances and cancer-causing agents. Single nucleotide polymorphisms (SNPs) in GSTP1 can affect its ability to catalyze reactions and detoxify, thereby influencing the risk of developing colorectal cancer (CRC). This study aimed to investigate the impact of functional SNPs (fSNPs) in GSTP1 on the risk of CRC, as well as their structural and functional consequences. We analyzed a total of 126 selected GSTP1 SNPs, including fSNPs rs1695 A > G (I105V) and rs1138272 C > T (A114V), in CRC patients (n = 103) and controls (n = 107) of south Indian origin using PCR-sequencing analysis with genomic DNA from blood samples. To assess the structural integrity of GSTP1 fSNPs, we conducted in silico analysis using various tools such as Swiss PDB Viewer, pyMOL mutagenesis wizard, ProSA-Web, and Pdbsum. Additionally, we performed functional characterization of GSTP1 fSNPs using cell and molecular biology techniques. Our findings revealed a significant association between the I105V fSNP and CRC risk, while the A114V fSNP did not show any significance. However, both fSNPs exhibited stronger linkage disequilibrium in patients compared to controls. In silico analysis indicated a loss of structural integrity and reduced electrostatic potential energy in the double mutant GSTP1 (V105/V114) compared to the native (I105/A114) or single mutant (V105/A114 and I105/V114) forms. Furthermore, FHC cells transfected with the GSTP1 I105V variant exhibited increased proliferation, invasion, and colony formation, along with decreased GST activity compared to carriers of the wild-type GSTP1. On the other hand, the GSTP1 A114V variant did not show a significant effect. Interestingly, FHC cells transfected with the double mutant GSTP1 variant (V105/V114) demonstrated synergistic and enhanced effects compared to the GSTP1 I105V variant. Consistent with these findings, plasma GST activity was significantly lower in haplogroups carrying both fSNPs compared to haplogroups with single or no fSNPs. To summarize, our findings indicate that while GSTP1 I105V alone contributes to the etiology of CRC, A114V does not; however, their combined presence has a more significant impact.