Vitamin D receptor gene polymorphism in Egyptian pediatric acute lymphoblastic leukemia correlation with BMD

We studied the frequencies of the 3' and 5'-end vitamin D receptor (VDR) gene polymorphisms and their correlation with bone mineral density (BMD) in Egyptian pediatric acute lymphoblastic leukemia (ALL) patients receiving calcium and vitamin D supplements. The purpose of this study is to find out the relation between VDR polymorphism and the response to vitamin D intake in pediatric ALL cases who receive corticosteroid therapy which predispose to osteoporosis. This study might shed the light on some genetic variants that are effect the response of individuals to vitamin D therapy.

Forty newly diagnosed pediatrics ALL cases were studied. Three SNPs at the 3'-end of the VDR gene (BsmI rs1544410, ApaI rs739837and TaqI rs731236) and two SNPs at the 5'-end (Cdx-2 rs11568820 and GATA rs4516035) were analyzed by Allelic discrimination assay. Of those twenty-six cases with initial BMD data available were further analyzed with regards to the effect of various VDR genotypes/haplotypes on BMD.

The genotype frequencies at 3'-end of VDR gene were, TaqI TT 23%, Tt 54% and tt 23%, BsmI bb 19.2%, Bb 65.4% and BB 15.4% and ApaI AA 12%, Aa 27% and aa 61%. The frequencies at the 5'-end were Cdx-2 GG 34.5%, GA 54% and AA 11.5% and GATA AA 8%, AG 50% and GG 42%. Eight and four possible haplotypes were observed at the 3' and 5'-ends of the VDR gene respectively. The Tt genotype was significantly correlated with high BMD as compared to other TaqI genotypes (P = 0.0420). There was a trend towards higher BMD with the genotype Bb as compared to other BsmI genotypes. No statistical significance was found between the other VDR genotypes or haplotypes studied and BMD.

This is the first report on VDR gene polymorphisms in Egyptian pediatric ALL patients. The Tt genotype was associated with increased BMD. Our study showed marked genetic heterogeneity in VDR gene in Egyptian pediatric ALL patients.