The Mutational Status Of Genes Involved In DNA Repair and Folate Pathway Predicts Overall Survival Of Patients With Low-Risk, Untreated Myelodysplastic Syndrome

Despite the prediction of a fairly benign clinical course, a subset of patients with low-risk myelodysplastic syndromes (MDS) have a more aggressive disease and shorter overall survival. The DNA repair and folate pathway genes play an important role in prognosis and progression in both solid and hematological cancers, and their expression has been known to be associated with polymorphism of genes. However, the impact of polymorphisms of these genes on MDS patients outcome has not yet been demonstrated. The aim of this study was to investigate the association between the polymorphisms of genes encoding main proteins of BER system (XRCC1, XRCC3 and APE1) and folate-metabolizing enzymes (TS, MTHFR) and survival in IPSS low-intermediate1 MDS patients.

the study was designed according to the Schoenfeld design for biomarkers, assuming the presence of an unfavorable pharmacogenetic profile (one or more adverse genotypes) in at least one-third of the study population. Accordingly, 10 events in 54 patients would allow the detection of an Hazard Ratio (HR) >6 associated with the group having unfavorable genotypes (80% power and 5% type I error for a two-tailed test). We thus prospectively genotyped 54 MDS patients (median age 75 years) with IPSS low (n=23) or intermediate-1 (n=31) treated with best supportive care only. Genomic DNA was isolated from 1ml of peripheral blood by means of commercially available kits. Polymorphisms were determined by PCR-HRM (High Resolution Melting) assay and restriction digests of PCR products. All samples were analyzed for the following polymorphisms: XRCC1 194 (rs1799782 C/T, Arg/Trp) and 399 (rs25487 G/A, Arg/Gln), XRCC3 241 (rs861539 C/T, Thr/Met), TS5'-UTR (2R/3R and rs183205964 G/C) and 3'-UTR Ins/Del (rs11280056 6bp+/6bp-), MTHFR 677 (rs1801133 C/T, Ala/Val) and 1298 (rs801131 A/C, Gln/Ala), APE1 148 (rs1130409 T/G, Asp/Glu). The characteristics and laboratory features of MDS patients with each polymorphisms were compared using Х²-test and Mann-Whitney test. The associations between polymorphisms status and survival were assessed using Kaplan-Meier method and Log-rank test. For the multivariate survival analysis, Cox proportional hazard models, was used to identify the genotypes fitted as indicator variables. Before performing clinical correlations, genotype frequencies were checked for agreement with those expected under the Hardy-Weinberg equilibrium.

The frequencies of genotypes of studied gene polymorphisms in patients with low/Int-1 risk are listed in Table 1. At univariate analysis, a significantly shorter survival was associated with XRCC1 399 GG, TS3’-UTR -6/-6, TS5’-UTR 2R/3G, 3C/3G, 3G/3G and MTHFR 677 TT variant alleles. In multivariate analysis, using a stepwise logistic regression model, patients with TS3’-UTR -6/-6, XRCC1-399 GG, TS5’-UTR 2R/3G, 3C/3G, 3G/3G and MTHFR- 677 TT unfavorable genotypes presented with an Hazard Ratios of 4.65, 7.07, 11.44 and 67.12, respectively, if compared to the reference group of variant alleles (P=.058, P=.024, P=.026 and P=.000). Accordingly, we performed an exploratory analysis to investigate the effect on survival arising from the combination of the unfavorable genotypes to each other. As a fact, 3-years OS was 33% for those patients with ≥2 variant alleles, as compared to 62.5%, and 100%, respectively, for those with 2 or 0/1 variant alleles, suggesting that patients with a higher number of variant alleles had a shorter survival.

The mutational status of BER, TS and MTHFR genes predicts the overall survival of patients with low-Int-1 IPSS MDS treated with best supportive care only. If confirmed on larger series, these polymorphisms could help to identify a subset of low-risk MDS patients with shorter survival, who might benefit from an early therapy with hypometilating agents.

The study was supported in part by AIL Pesaro Onlus.

No relevant conflicts of interest to declare.