Epigenetic modifications but not genetic polymorphisms regulate KEAP1 expression in colorectal cancer

Abstract

Kelch-like ECH-associated protein 1 (KEAP1), as a negative regulator of nuclear factor erythroid 2 like 2 (NRF2), plays a pivotal role in NRF2 signaling pathway and involves in tumorigenesis. Polymorphisms and methylation in gene promoter region may influence its expression and be related to cancer susceptibility. In this study, we examined the effect of the KEAP1-NRF2 interaction on the risk of colorectal cancer (CRC). The polymorphisms of NRF2 and KEAP1 were genotyped using the improved multiplex ligase detection reaction assay. KEAP1 promoter methylation and histone modification were analyzed using bisulfite genome sequencing and chromatin immunoprecipitation (ChIP) assay, respectively. The KEAP1 rs1048290 CC genotype and C allele were associated with increased risks of CRC (CC vs GG: odds ratio [OR] = 1.39; 95% confidence interval [CI], 1.08-1.78; CC vs GG/GC: OR = 1.29; 95% CI, 1.05-1.58; C vs G: OR = 1.18; 95% CI, 1.04-1.34). The rs1048290-rs11545829 GT haplotype was associated with a reduced risk of CRC. KEAP1-NRF2 interaction analysis revealed that the rs6721961, rs35652124, rs1048290, and rs11545829 conferred the susceptibility to CRC. The hypermethylation of KEAP1 promoter resulted in lower levels of KEAP1 messenger RNA (mRNA). After treatment with 5-aza-2′-deoxycytidine/trichostatin A, KEAP1 promoter methylation was decreased and KEAP1 mRNA levels were increased. ChIP-quantitative polymerase chain reaction results showed an enhanced enrichment of H3K4Me3 and H3K27Ac to the promoter of KEAP1. In vitro methylation analysis showed that the methylated plasmid decreased the transcriptional activity by 70%-84%. These findings suggest that the KEAP1-NRF2 pathway could potentially impact CRC risk and the downregulation of KEAP1 could be explained in part by epigenetic modifications.

Epigenetic Regulation of NRF2/KEAP1 by Phytochemicals

“…Hypermethylation of these CpG sites markedly lowered NRF2 expression in prostate tumorigenesis [32]. As discussed above, KEAP1 promoter methylation was first reported in lung cancer, but similar observations have been linked to poor prognosis in glioma, breast cancer, non-small cell lung carcinoma, colorectal cancer, clear renal cell carcinoma, and pancreatic cancer [33][34][35][36][37][38].…”

Epigenetic Therapeutics Targeting NRF2/KEAP1 Signaling in Cancer Oxidative Stress

“…Aberrant hypermethylation in KEAP1 promoter region was the most common alteration found in nearly half of the non-small cell lung cancer (NSCLC) cases ( Muscarella et al, 2011a ), and has been proven to be associated with poor prognosis in various cancers including malignant glioma, breast cancer and pancreatic cancer ( Muscarella et al, 2011b ; Barbano et al, 2013b ; Zhang et al, 2016b ). Numbers of research has revealed that 5-aza-2′-deoxycytidine (5-aza) treatment demethylated the CpG sites in the KEAP1 promoter region, synergistically contributing to KEAP1 overexpression, NRF2 degradation and inactivation of various relevant signal pathways ( Wang et al, 2008b ; Guo et al, 2015c ; Gao et al, 2019 ), which were related to enhanced survival and reduced lymph node metastasis of NSCLC patients ( Chien et al, 2015 ). Contrary to 5-aza, Fumonisin B, a common toxic mycotoxins of cereal grains, activated NRF2/KEAP1 pathway by hypermethylating CpG islands in KEAP1 gene, consequently enhancing ROS production along with promoting cell membrane damage in human hepatoma cells ( Arumugam et al, 2021 ).…”

Association of variations in platinum resistance-related genes and prognosis in lung cancer patients

“…Transcription factor NFE2L2 (nuclear factor, erythroid 2 like 2), also named NRF2, functions as an oncogene or tumor suppressor, it regulates the cellular antioxidant response and promotes cancer chemotherapy resistance, metastasis, and progression [26][27][28]. The rs6706649 and rs6721961 in NFE2L2 may influence breast cancer prognosis, rs6721961 and rs35652124 are associated with susceptibility to colorectal cancer [29,30].…”