Objective: To establish a feasible algorithm for individual identification of colorectal cancer tissue by investigating its STR mutation.
Methods: Fifty pairs of fresh colorectal cancer and homologous normal tissues (CR-N group) were genotyped with Identifiler Kit and the mutations generated in cancer tissues were determined. The mutation rates, the numbers of locus matched without identical allele (A0), 1 identical allele (A1), or 2 identical alleles (A2) and the number of total identical alleles (IA(n)) were calculated. Frequency distributions of A0, A1, A2 and IA(n) were compared among CR-N group, unrelated individual pairs (UI group) and full sibling pairs (FS group). Discrimination functions were established for individual identification from tumor tissues with discriminatory analysis.
Results: The frequency of STR genotypic alteration (STR(GA)) was 3.33% in the 50 colorectal cancer samples. A1, A1 and IA(n) were fitted to skew distribution in CR-N group, which were significantly different from those in UI or FS group. Based on IA, and A,/A2, discrimination functions were established and validated with an error rate as low as 0.00% for individual identification from colorectal cancer tissue.
Conclusion: Discrimination functions established in this study could be a feasible method for individual identification of colorectal cancer samples, which usually have a high frequency of STR(GA).