Correlation between Thymidylate Synthase Gene Variants, RNA and Protein Levels in Primary Colorectal Adenocarcinomas

Abstract

This study was designed to compare thymidylate synthase (TS) genotype, mRNA and protein levels in primary colorectal adenocarcinoma, and to examine the correlation between microsatellite instability (MSI) and TS expression. The TS genotype of 68 patients with colorectal cancer was determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism analysis in peripheral blood mononuclear cells and tumour tissue. The TS mRNA levels in tumour tissue were measured by reverse-transcription PCR, and TS protein levels and MSI status were assessed using immunohistochemistry. Significantly higher mRNA and protein levels were observed in patients with the TS 3R/3R versus the 2R/2R and 2R/3R genotypes. There was no correlation between TS single nucleotide polymorphism and TS expression. Individuals homozygous for the six base-pair insertion in the 3'-untranslated region had significantly higher TS mRNA levels than heterozygous and homozygous wild type individuals. The TS mRNA and protein levels were significantly higher in microsatellite unstable tumours compared with microsatellite stable tumours. There was a significant association between the number of TS enhancer region repeats (in blood) and intratumoural TS mRNA and protein levels. A larger case series investigating the role of TS gene polymorphisms as predictors of sensitivity to 5-fluorouracil-based chemotherapy is required.

Thymidylate synthase expression and genotype have no major impact on the clinical outcome of colorectal cancer patients treated with 5-fluorouracil

“…These findings suggest that the number of repeats could be more important than their sequence differences for the regulation of TS mRNA expression in vivo. Other authors reported similar results, confirmed both at the RNA and protein level, on CRC tissue samples [31]. On the other hand, a positive correlation between TS protein expression/activity and the 3RG allele in normal mucosa has also been observed [32].…”

Pronounced between‐subject and circadian variability in thymidylate synthase and dihydropyrimidine dehydrogenase enzyme activity in human volunteers

“…A strong correlation between TSA pbmc and TYMS gene expression in PBMCs clearly suggests that BSV in TS activity is regulated at a transcriptional level. Within cancer tissue, others have also found correlations between TS protein and gene expression [45,46]. One volunteer carried the G > C SNP in the 2R allele and was identified with the 2RC/3RC genotype of TYMS.…”

Analysis of Polymorphisms and Haplotype Structure of the Human Thymidylate Synthase Genetic Region: A Tool for Pharmacogenetic Studies

“…A 6-bp insertion/deletion polymorphism (TTAAAG) in the 3′-UTR of the thymidylate synthase gene was proposed to influence Tyms expression [29], [30] and 5FU-related toxicity in patients [31] in several studies. This polymorphism occurred in less than 20% of the chromosomes analyzed and was observed on multiple haplotype backgrounds (results not shown).…”