The promoter is the center for regulation of gene transcription due to containing numerous transcription factor binding sites. The aim of the study was to determine whether genetic variations at excision repair cross complementation group 5 (ERCC5) promoter could affect transcription factor binding and whether such single nucleotide polymorphism (SNP)-dependent binding could affect gene expression, drug response, and clinical outcome.
A total of 170 patients who were cytologically or histologically confirmed with advanced colorectal cancer (CRC), at least 1 measurable lesion, and underwent oxaliplatin-based chemotherapy were studied. The polymerase chain reaction–ligation detection reaction (PCR-LDR) was used to analyze SNPs. The reporter gene assay system and electrophoretic mobility shift assays (EMSA) were performed to investigate the effect of SNPs on the ERCC5 promoter activity and DNA-binding activity, respectively. The mRNA and protein expression of ERCC5 in tumor tissues of colorectal cancer patients with different genotypes were detected by real-time PCR and western blot, respectively.
Both −763A and −763G allele had nuclear protein-binding ability. +25A allele did not show any nuclear protein-binding ability, whereas +25G allele did. The relative luciferase activity of the −763A/+25G haplotype was significantly higher than other 3 haplotypes (P < 0.05). The expression level of ERCC5 mRNA and protein was significantly higher in tumor tissues with −763AA+25GG genotype combination than that with −763GG+25AA genotype combination (P < 0.05, respectively). Allelic variants (−763AA vs −763AG or –763GG, +25GG versus +25AG or +25AA) were significantly associated with shorter progression-free survival (PFS) and overall survival (OS) (P < 0.05, respectively). At multivariate analysis, patients with risk genotypes (−763AA or +25GG genotype) demonstrated a significantly increasing risk of progression (P = 0.01) or worse OS (P = 0.001).
The ERCC5 promoter polymorphisms at −763 and +25 may be important functional variants and predictors of clinical outcome of CRC patients who received oxaliplatin chemotherapy.