Patient-derived xenografts of colorectal cancer for testing new pharmacological substances.

Abstract

e15612 Background: The purpose of this study was to create a patient-derived xenograft model of human colorectal cancer and to determine its histological and molecular characteristics, including the status of the KRAS, NRAS, BRAF genes and the presence of microsatellite instability factors. Methods: Biological materials obtained from tumors of 4 patients with colorectal cancer were used to create the first-generation in vivo model. The study was performed on immunodeficient Balb/c Nude mice (20 females aged 5-6 weeks). Subcutaneous xenografts were obtained by the implantation of a 3×3×3 mm donor tumor fragment to recipient animals under the skin of the right thigh, 5 samples from each patient. For the second, third and fourth PDX generations, mice of the same strain were used (n = 3 for each generation). All manipulations were performed in accordance with the rules for using laboratory animals. Genomic DNA was extracted from PDX samples, and mutations in exons 2, 3 and 4 of the KRAS and NRAS genes and BRAF V600 mutations were identified by direct sequencing. Microsatellite instability was determined by fragment analysis for five loci Bat-25, Bat-26, NR21, NR24, NR27. Results: Stable transplantable xenografts of colorectal cancer were obtained from two out of four patients. The average waiting time between implantation and growth of the first-generation xenograft was 28 days. The model was confirmed to reproduce the histotype, differentiation and mutational status of the KRAS, NRAS, BRAF genes and microsatellite instability similar to those of donor tumors. Conclusions: The results confirm the possibility of the model use for testing both new pharmacological substances with a cytotoxic effect and drugs based on monoclonal antibodies.