The ATP-binding cassette transporter ABCG2 (BCRP) and ABCB1 (MDR1) variants are not associated with disease susceptibility and disease phenotype in Hungarian patients with inflammatory bowel diseases

Aims: MDR1 (ABCB1), a member of the ATP-binding cassette (ABC) transporters, is an attractive candidate gene for the pathogenesis of inflammatory bowel diseases (IBD) and perhaps response to therapy. Since limited data are available on MDR1 and ABCG2 polymorphisms in East European IBD patients, our aim was to study the ABCG2 and MDR1 variants and patients' response to medical therapy and/or disease phenotype in Hungarian patients. Methods: 414 unrelated IBD patients (CD: 265, age: 35.2±12.1years, duration: 8.7±7.6years and UC:149, age: 44.4±15.4 years, duration: 10.7±8.9 years) and 149 healthy subjects were investigated. ABCG2 G34A, C421A and MDR1 C3435T, G2677T/A SNPs were detected using real-time PCR. Detailed clinical phenotypes were determined by reviewing the medical charts. Results: The frequency of the ABCG2 and MDR1 SNPs was not significantly different among IBD, CD, UC patients and controls. The risk for steroid resistance was not different in CD patients carrying variant ABCG2 (19.6% vs. non-carriers 18.4%, p=NS) or MDR1 3435T (CC: 22.2% vs. CT/TT: 17.6%) alleles. Additionally, carriage of the variant allele was not associated to disease phenotype, presence of extraintestinal manifestations, smoking, response to infliximab therapy or need for surgery. In UC, the carriage of variant ABCG2 alleles seemed to be preventive for arthritis (15.5% vs. 31.7%, OR: 0.39, 95%CI: 0.16–0.98). Conclusions: MDR1 and ABCG2 SNPs were not associated to disease susceptibility or disease phenotype in Hungarian patients, as well as variant alleles did not predict the response to medical therapy or need for surgery. Further studies are needed to clarify the association between the presence of ABCG2 variants and arthritis in UC.