Feasibility of novel PPP1R15A and proposed ANXA11 single nucleotide polymorphisms as predictive markers for bevacizumab regimen in metastatic colorectal cancer

Abstract

Purpose: Bevacizumab improves survival in patients with metastatic colorectal cancer (mCRC) under chemotherapy, but few predictive markers have been identified. Methods: To investigate chemosensitive single nucleotide polymorphisms (SNPs) of mCRC, we performed exome sequencing and RNA sequencing in 19 patients. A clinical association analysis was performed with the other 116 patients who had received chemotherapy to bevacizumab regimens. In vivo biodistribution studies and [18F]FDG-PET imaging were performed on mice bearing human colorectal cancer (HCT116 and SW480) xenografts after injection of bevacizumab with 5-FU, leucovorin, and irinotecan (FOLFIRI). Results: PPP1R15Ars557806 showed the most significant association with FRB-driven tumor IR in exome sequencing and the highest correlation (r=0.74) with drug responses in RNA sequencing. Patients homozygous for the reference alleles (GG) of PPP1R15A rs557806 exhibited greater disease control rate and a tendency toward greater objective response rate (ORR) than those with homozygous or heterozygous substitution alleles (GC and CC; P=0.027 and 0.073, respectively). In xenografted mice, HCT116 clones transfected with the G allele at PPP1R15A rs557806 were more sensitive to bevacizumab regimens than those with the C allele. Tumor volume of xenografts with the G allele was significantly lower than that of xenografts with the C allele (P=0.004, day 13). [18F]FDG uptake decreased to 75% in HCT116 xenograft-bearing mice with the G allele, whereas [18F]FDG uptake was 42% in mice xenografts with the C allele (P=0.032). ANXA11 rs1049550, a predictive biomarker of SNP described in our previous study, was validated using the xenograft model. Tumor volume and [18F]FDG uptake analyses showed that tumors in the SW480 xenografts expressing the substitution allele (T) at ANXA11 rs1049550 were more susceptible to FOLFIRI plus bevacizumab-induced suppression than those expressing the reference allele (C) (P=0.001 and 0.026, respectively). Conclusion: ANXA11 rs1049550 and PPP1R15A rs557806 may improve the identification of mCRC patients sensitive to bevacizumab regimens, and further validation is required in large cohorts.