PTEN-induced kinase 1 gene single-nucleotide variants as biomarkers in adjuvant chemotherapy for colorectal cancer

ABSTRACT Background Fluoropyrimidine-based adjuvant chemotherapy is globally recommended for postoperative stage III colon cancer and high-risk stage II patients. However, adjuvant chemotherapy is often associated with severe adverse events and is not highly effective in preventing recurrence. Therefore, a recurrence-prevention biomarker of adjuvant chemotherapy for colorectal cancer is necessary for providing such treatments to appropriate patients. Autophagy (including mitophagy) is activated under chemotherapy-induced stress and contributes to chemotherapy resistance. Expression of autophagy-related genes and their single-nucleotide polymorphisms are reported to be effective predictors of chemotherapy response in some cancers. Our goal was to evaluate the relationship between the single-nucleotide variants of autophagy-related genes and recurrence rates to identify the recurrence-prevention biomarkers of adjuvant chemotherapy in colorectal cancer. Methods We analyzed surgical or biopsy specimens from 84 patients who underwent radical surgery followed by fluoropyrimidine-based adjuvant chemotherapy at Saitama Medical University International Medical Center between January and December 2016. Using targeted enrichment sequencing, we identified single-nucleotide variants and insertions/deletions in 50 genes, including autophagy-related genes, and examined their association with colorectal cancer patient relapse rates. Results We detected 560 single-nucleotide variants or insertions/deletions in the target region. The results of Fisher’s exact test indicated that the recurrence rate of colorectal cancer after adjuvant chemotherapy was significantly lower in patients with the single- nucleotide variants (c.1018G>A [ p C [ p < 0.01]) of the mitophagy-related gene PTEN-induced kinase 1. Conclusions The two single-nucleotide variants of this mitophagy-related gene may be biomarkers of non-recurrence in colorectal cancer patients who received postoperative adjuvant chemotherapy.