Objective: To establish a method for SNP genotyping of multi-genes by allele-specific oligonucleotide probe ligation mediated by a thermostable ligase, and to explore the genetic polymorphisms of drug-metabolizing enzymes in breast cancer patients and their association with chemotherapeutic responses.
Methods: 10 SNP loci of enzyme genes related to chemotherapeutic drugs such as taxanes, anthracyclines and cyclophosphamide were selected, and were genotyped for blood samples from 126 breast cancer patients by the established method. Their correlations with therapeutic responses were retrospectively evaluated.
Results: The lower detection limit of genomic DNA by this developed method was 6.25 ng. The fluorescent peak locations of ligation products on ABI PRISM 377 DNA sequencer were accurate and consistent with prospective sizes in bases (Bias range 0.08 - 0.69 bp, x(-) = 0.31 bp, s = 0.18 bp). Same genotyping results were obtained for repeat tests of 8 random samples, which were further confirmed by sequencing analysis. The 10 SNP loci were polymorphic of different frequency in the breast cancer patients. The combinations with GSTP1 genotypes and GSTM1 genotypes were related to anthracycline-based chemotherapy efficacy (P = 0.037), and the low GSTs activity group (GSTP1 variant allele + GSTM1 null) showed the best effects (85.7%). GSTM1 genotypes and their combinations with GSTP1 and/or CYP3A5*3 genotypes were related to taxane-based therapy efficacy (P < 0.05 for all), and both the low GSTs activity group and the drug slow-metabolising group (low GSTs activity group + CYP3A5*3 wild allele) showed better effects (100%).
Conclusion: The established method is reliable and applicable in multiplex SNPs genotyping of multi-genes. SNPs combination may have a better clinical application value for prediction of chemotherapeutic responses.