SNP rs34172460 (S258A)Â in Gene CIP2A Correlates with Bortezomib Resistance in Multiple Myeloma Patients

Introduction: The proteasome inhibitor (PI) bortezomib is a novel anticancer drug that shows activity especially for treating patients with multiple myeloma (MM). However, its clinical efficacy has been hampered by the emergence of drug-resistance phenomena, the genetic and molecular basis of which remains elusive. We propose that the resistance to bortezomib treatment may be related to a polymorphism in a gene known to be a target for bortezomib's activity which has been identified as CIP2A which is a tumor suppressor PP2A inhibitor. We have used a high resolution melting curve (HRM) approach to screen several CIP2A SNPs containing significant genetic changes that may be different between bortezomib sensitive and resistant MM patients. In this study, we evaluated SNPs in this gene in healthy subjects and MM patients who were sensitive or resistant to bortezomib-based therapy.

Methods: A panel of DNA samples was purified from MM patients (N=73) and healthy subjects (N=95). The samples were divided into three groups: bortezomib sensitive MM patients (N=61), bortezomib resistant MM patients (N=12), and healthy subjects. A single nucleotide polymorphism (SNP) of the bortezomib target genes CIP2A was selected. The PCR prime pairs for each SNP marker were designed with the software "Primer Expression 3" (Thermo Fisher Scientific). The genotype of each DNA sample was determined with the high resolution melt curve (HRM) technology on a real-time PCR instrument, StepOne Plus (Thermo Fisher Scientific).

Results: The frequency of heterozygosity and homozygosity of CIP2A, SNP rs34172460(S258A) was 0.049 (3 out of 61 cases) in the bortezomib sensitive group, while it was 0.25 (3 out of 12 cases) in the bortezomib resistant group, a 5-fold increase in the frequency of this SNP. The frequency of heterozygosity and homozygosity of this same SNP in the healthy subjects was only 0.03 (3 out of 95 samples).The minor allele frequency (MAF) in the normal population is 0.046, according to the SNP data base, compatible with what we observed in both our healthy subjects and the bortezomib sensitive MM patients.

Conclusion: This preliminary data suggests that heterozygotic and homozygotic mutants of rs34172460(S258A) may have an impact on resistance to bortezomib among patients with multiple myeloma.