Gene Expression Levels Of Imatinib Transporters and Molecular Response To Imatinib Therapy In Chronic Myeloid Leukemia Patients

Imatinib mesylate (IM) is the standard first-line treatment for most CML patients. After an initial response, approximately 30 to 40% patients develop resistance to the drug. Various mechanisms of resistance to Imatinib therapy have been identified. One of the mechanisms proposed is varying expression levels of the drug transporters. In the present study, we determined the relative expression levels of Imatinib transporter genes (hOCT1, ABCB1, ABCG2) in CML patients by quantitative real time polymerase chain reaction (qRT-PCR) and correlated these levels with molecular response.

One hundred and ten CML patients were considered for gene expression analysis study for hOCT1 gene and eighty seven CML patients were considered for gene expression analysis study for ABCB1 and ABCG2 genes. CML patients who were on IM therapy for more than 2 years were divided into two groups: Responders: patients who achieve a Complete Molecular response (CMR) or a Major Molecular Response (MMR) [bcr/abl: abl ratio <1% as assessed by RQ-PCR] and Non-responders: those without CMR or MMR (bcr/abl: abl ratio =/> 1% as assessed by RQ-PCR). The relative transcript expression levels of the three genes were compared between responders and non-responders. No significant difference in the expression levels of hOCT1, ABCB1 and ABCG2 was found between the two categories - responders versus non-responders (p value > 0.05). The median transcript expression levels of hOCT1, ABCB1 and ABCG2 genes in responders were 30.63, 10.14 and 0.59 versus 40.13, 8.34 and 0.53 in non-responders, respectively.

We conclude that, in our study, the mRNA expression levels of IM transporter genes did no correlate with molecular response in CML patients.