Polymorphisms of pluripotency transcription factors for predicting cetuximab efficacy in metastatic colorectal cancer: Data from FIRE-3 and TRIBE trials.

Abstract

98 Background: Cancer stem cells are subpopulation of cancer cells characterized by the self-renewal ability, and primarily maintained by a network of pluripotency transcription factors (PTFs). Despite their chemo-resistant phenotype, recent clinical trials data show cetuximab (Cet) is more beneficial for a subset of metastatic colorectal cancer (mCRC) categorized in a mesenchymal/stem-like subtype based on transcriptomic classifications. We investigated whether single nucleotide polymorphisms (SNPs) in PTF encoding genes have predictive values for the efficacy of Cet in mCRC patients. Methods: Genomic and clinical data from three independent cohorts of patient treated with first-line chemotherapy ( n = 451, in total) were tested: Cet cohort (FOLFIRI+Cet arm in FIRE-3 trial, n = 129); bevacizumab (Bev) cohort 1 (FOLFIRI+Bev arm in FIRE-3 trial, n = 107) and Bev cohort 2 (FOLFIRI+Bev arm in TRIBE trial, n = 215), as controls. Genomic DNA extracted from blood samples was genotyped using an OncoArray (Illumina, Inc., San Diego, CA, USA). Eight SNPs in PTF encoding genes ( NANOG rs11055786, NANOG rs11055767, NANOGP8 rs2168958, NANOGP8 rs9944179, POU5F1 rs3130501, POU5F1 rs3130932, SOX2 rs11915160, and MYC rs3891248) were tested for association with progression-free survival (PFS) and overall survival (OS), using Cox proportional hazards model. Results: In the Cet cohort, three SNPs were significantly associated with PFS in univariate analysis: NANOG rs11055767 (C/C vs any A allele, hazard ratio [HR] = 0.62, 95% confidence interval [CI] = 0.42–0.94, log-rank p = 0.02), NANOGP8 rs2168958 (A/A vs any C allele, HR = 2.12, 95% CI = 1.36–3.29, log-rank p < 0.01), and NANOGP8 rs9944179 (G/G vs any A allele, HR = 3.68, 95% CI = 1.46–9.31, log-rank p < 0.01). Multivariate analysis confirmed the significance in NANOGP8 rs2168958 and NANOGP8 rs9944179. Furthermore, two SNPs were significantly associated with OS in multivariate analysis: POU5F1 rs313051 (G/G vs any A allele, HR = 0.46, 95% CI = 0.22–0.99, adjusted p = 0.04) and POU5F1 rs3130932 (A/A vs any C allele, HR = 0.46, 95% CI = 0.22–0.93, adjusted p = 0.03). Both in the Bev cohorts 1 and 2, no significant associations between the SNPs and clinical outcomes were observed. Conclusions: The current findings suggest that polymorphisms in the PTF genes could be predictive markers for Cet in patients with mCRC. Further studies are warranted to validate the predictive utility.