MDM2 SNP309 and TP53 SNPArg72Pro Polymorphisms in Myelodysplastic Syndrome.

Myelodysplastic syndrome (MDS) encompasses a heterogeneous group of clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis, refractory cytopenia and a tendency to progress towards acute myeloid leukemia (AML). The progression of the disease may be associated with genetic or epigenetic alterations and a possible change in protein function. MDM2/P53 pathway plays an important role in the control of apoptotic and proliferation mechanisms. Single nucleotide polymorphisms (SNPs) were identified in the TP53 and MDM2 genes. MDM2 SNP309 results in higher levels of MDM2 and attenuates p53 pathway. The SNP in codon 72 of the TP53 gene results in either a C or G nucleotide and leads to either Proline (Pro) or Arginine (Arg), respectively. The Arg variant has been shown to be more potent in apoptosis induction and the Pro variant has been shown to be better in inducing cell-cycle arrest and to have a greater ability to repair damaged-DNA. The aim of the present study was to investigate the incidence of MDM2 and TP53 polymorphisms in MDS patients and to correlate the frequency of these SNPs with age, neutrophis and platelets at diagnosis, low risk versus high risk disease according to FAB (RA and RARS versus AREB and AREBt) and IPSS (Low and Int-1 versus Int-2 and high), cytogenetic risk (low versus intermediate and high risk), disease progression and overall survival.

We studied 103 healthy controls and 63 patients with MDS. According to FAB, patients were distributed as follows: 43 RA, 10 RARS, 7 RAEB, 1 RAEBt and 2 CMML. The median follow-up time was 40 months (range 2 – 159 months). Samples were obtained from peripheral blood or bone marrow and were screened for the presence of polymorphisms MDM2 SNP309 and TP53 SNPArg72Pro, by PCR analysis with specific primers and appropriate restriction enzyme. Appropriate statistical analyses were used for each test.

The frequencies of genotypes for MDM2 SNP309 and TP53Pro7Arg were similar between MDS and healthy controls; MDM2 SNP309: 51% vs 53%, for TT, 38% vs 32% for TG, and 11% vs 15% for GG, TP53Pro7Arg: 47.5% vs 44%, for Arg/Arg, 47,5% vs 42% for Pro/Arg, and 5% vs 14% for Pro/Pro. No differences were observed between MDS patients with presence or absence of the polymorphisms in relation to age, neutrophis and platelets at diagnosis, low risk versus high risk disease according to FAB, IPSS and cytogenetic risk, disease progression and overall survival.

MDM2 and TP53 polymorphisms have been described to affect the risk for cancer, onset age and overall survival in solid tumors and leukemias. This was the first study to report these SNPs in MDS and leads to believe that these polymorphisms are not associated with risk for the disease and with clinical data. Keywords: MDM2, p53, myelodysplasia, polymorphisms

No relevant conflicts of interest to declare.