Association of ABCB1 gene polymorphisms and haplotypes with therapeutic efficacy of glucocorticoids in Chinese patients with immune thrombocytopenia.

Resistance to glucocorticoids (GCs) remains a tricky problem complicating the therapy of ITP. Recently, ATP binding cassette gene B1 gene (ABCB1) was reported to be correlated with susceptibility and therapeutic efficacy of autoimmune diseases through P-glycoprotein (Pgp). We investigated three single nucleotide polymorphisms (SNPs) of ABCB1 and their haplotypes by PCR-RFLP (restriction fragment length polymorphism) method in 471 ITP patients and 383 healthy controls, patients were further assigned into GCs-responsive and -non-responsive group according to the therapeutic effects of GCs. We observed a remarkable difference in genotypes of G2677T/A between GCs-responsive and non-responsive group, but not between patients and controls. A frequently expression of T/A allele within G2677T/A was recorded in GCs-responsive group. Furthermore, we found that some haplotypes (CGC, CTC/CAC, CTT/CAT, TGC, TGT, TTC/TAC and TTT/TAT, in the order of position 1236-2677-3435) were presented significantly differences between non-responsive and responsive group. No difference of C1236T and C3435T polymorphisms was observed between ITP and controls, and between the GCs-responsive and -non-responsive group. Our findings suggest that ABCB1 polymorphisms, as well as haplotypes derived from C1235T, G2677T/A and C3435T, are associated with inter-individual differences of GCs treatment in ITP.