Cancer Stem Cell Gene Variants in CD44 Predict Outcome in Stage II and Stage III Colon Cancer Patients

Background/Aim: Growing evidence suggests that human cancers are stem cell diseases and recent data support the existence of cancer stem cells (CSCs) in a variety of malignancies, including colon cancer. These CSCs were shown to be capable of initiating tumor development and progression. Several studies have suggested CD133, CD26 and CD44 as markers of tumor-initiating cells of colon cancer. The purpose of the present study was to assess the impact of single-nucleotide polymorphisms (SNPs) in stem cell-related genes on clinical outcome in a large cohort of colon cancer patients with clinical stage II and III. Patients and Methods: Data from 599 consecutive patients with colon cancer stage II and III, treated between 1995 and 2011 at a single centre, were retrospectively evaluated. Genomic DNA was extracted from paraffin-embedded normal tissue distant from the tumor to obtain germline DNA. Allelic distribution of polymorphisms was tested for deviation from Hardy-Weinberg equilibrium using x(2)-test. The association of polymorphisms with time to recurrence (TTR) and overall survival (OS) was analyzed using Kaplan-Meier curves and compared by the log-rank test. Case-wise deletion for missing polymorphisms was used in univariable and multivariable analyses. Results: CD44 rs187115 showed a statistically significant association with TTR; patients carrying at least one G allele had a significant reduced risk of recurrence compared to patients with the homozygous A/A variant (hazard ratio (HR)=0.67, 95% confidence interval (CI)=0.48-0.94, p=0.019). CD44 rs13347 showed a statistically significant association with OS. Patients carrying at least one T allele in rs13347 had a significantly reduced risk of death compared to patients with the homozygous C/C variant (HR=0.61, 95% CI=0.41-0.92, p=0.019). None of the other investigated polymorphisms (CD44 rs187116, CD44 rs7116432, CD44 rs353639, DPP4 rs2268889, DPP4 rs3788979, DPP4 rs7608798 and CD133 rs2240688) were associated with either TTR or OS. Conclusion: Germline variants rs13347 and rs187115 in the stem cell gene CD44 are prognostically relevant in stage II and III colon cancer patients.