The association between the T309G polymorphism of the MDM2 gene and sensitivity to anticancer drug is dependent on the p53 mutational status in cellular models

Background:

We investigated, in the panel of 60 human tumour cell lines of the National Cancer Institute (NCI-60), whether the R72P polymorphism of TP53 and the T309G polymorphism of MDM2 were associated to the in vitro cytotoxicity of anticancer agents, extracted from the NCI database. For validation, the same study was performed independently on a second panel of tumour cell lines, JFCR-45.

Methods:

Both SNPs were identified in cell DNA using PCR-RFLP techniques confirmed by direct sequencing and by pyrosequencing. For the analysis of the results, the mutational status of p53 was taken into account.

Results:

In the NCI-60 panel, the TP53 rare-allele frequency was 32% and the MDM2 rare-allele frequency 39%. The MDM2 alleles were distributed according to Hardy–Weinberg equilibrium whereas this was only found, for the TP53 alleles, in p53 non-mutated cell lines. Comparable results were obtained in the JFCR-45 validation set. The TP53 SNP had low impact on anticancer drug cytotoxicity in either panel. In contrast, the MDM2 gene polymorphism had a major impact on anticancer drug cytotoxicity, essentially in p53 non-mutated cell lines. Presence of the rare allele was associated to significantly higher MDM2 protein expression and to increased sensitivity to DNA-interfering drugs. In the JFCR-45 panel, a similar effect of the MDM2 gene polymorphism was observed, but was less dependent on the p53 mutational status.

Conclusions:

We hypothesised that cell lines harbouring the MDM2 G allele presented a lower availability of p53 for DNA repair, translating into higher sensitivity to DNA-damaging agents.