en Pediatric Hematology & Oncology Pediatric Hematology & Oncology پژوهشي Original Article <p><strong>Background:</strong> The frequency of the multi-drug resistance 1 (MDR1) gene C3435T polymorphism differs in various ethnical populations such as Asian, African, and Caucasians populations. A silent C3435T polymorphism in exon 26 of MDR1 has been reported to be associated with a decreased expression of P-gp in TT genotypes carriers compared with CC genotypes carriers. </p><p><strong>Materials and Methods:</strong> To evaluate the association between MDR1 gene C3435T polymorphism and acute lymphocyte leukemia (ALL), 126 ALL patients (72 males and 54 females) with a mean age of 11.42 ± 6.55 and 139 healthy controls (79 males and 60 females) with a mean age of 12.15 ± 7.5 who were referred to Dr. Sheykh hospital, Mashhad, Iran, between 2005-2007 were enrolled in our study and their C3435T MDR1 polymorphism was investigated using PCR-RFLP. </p><p><strong>Results:</strong> The mutant homozygous TT and TC genotypes were found to be associated with the incidence of ALL (p<0.05). There was no significant difference for T allele frequency between ALL patients and healthy controls (OR=1.08, 95% CI 0.84-1.66, p=0.33). </p><p><strong>Conclusion:</strong> TT genotypes carriers are at higher risk of developing ALL than carriers of other genotypes. </p> p-glycoprotein, multi-drug resistance, acute lymphoblastic leukemia, polymorphism 63 67 http://ijbc.ir/browse.php?a_code=A-10-2-21&slc_lang=en&sid=1 Behnoush Miladpour 1003194753284600159 1003194753284600159 Yes Amireh Nejat Shokouhi 1003194753284600160 1003194753284600160 No Abbas Shirdel 1003194753284600161 1003194753284600161 No Reza Entezari Heravi 1003194753284600162 1003194753284600162 No Abdollah Banihashem 1003194753284600163 1003194753284600163 No Habibollah Esmaeili 1003194753284600164 1003194753284600164 No Azam Khedri 1003194753284600165 1003194753284600165 No Javad Behravan 1003194753284600166 1003194753284600166 No