MDR modulation in acute myelogenous leukemia: is it dead?

Multifunctional Gold Nanoparticles Overcome MicroRNA Regulatory Network Mediated-Multidrug Resistant Leukemia

Resistance to chemotherapy and molecularly targeted therapies is a major problem in current leukemia treatments. Here, we investigated cross-talk between the miR-221 network and P-glycoprotein (P-gp) in doxorubicin-induced drug resistance of leukemia cells. Multifunctional gold nanoparticles were designed and synthesized to co-deliver three anticancer agents, AS1411, doxorubicin and anti-221, for improving leukemia treatment efficacy. These nanoparticles significantly inhibited the proliferation and clonogenic potential, and induced apoptosis of drug-resistant leukemia cells. The decreased growth of drug-resistant cells induced by these nanoparticles was associated with marked downregulation of miR-221 and DNMT1, leading to restored p27kip1 and p15ink4b tumor suppressor expression, as well as miR-221-mediated reduction of P-gp expression. Finally, primary blasts derived from leukemia patients experiencing chemoresistant relapse that were exposed to these nanoparticles were sensitized to doxorubicin, as evidenced by suppression of leukemic cell growth and a significant reduction of the doxorubicin IC50 value. Our findings provide proof of concept that this novel drug delivery system can precisely reverse the multidrug resistant leukemia phenotype based on preclinical models of leukemia, providing the framework for future clinical trials aimed at overcoming drug resistance and improving patient outcome.

Upregulation of multi drug resistance genes in doxorubicin resistant human acute myelogeneous leukemia cells and reversal of the resistance

The major problem in the treatment of acute myeloid leukemia (AML) patients results from multidrug resistance to administered anticancer agents. Drug resistance proteins, MDR1 and MRP1, which work as drug efflux pumps, can mediate the multidrug resistance of human leukemia cells. In this study, the mechanisms of resistance to doxorubicin-induced cell death in human HL60 AML cells were examined. Continuous exposure of cells to step-wise increasing concentrations of doxorubicin resulted in the selection of HL60/DOX cells, which expressed about 10.7-fold resistance as compared to parental sensitive cells. The expression analyses of MRP1 and MDR1 drug efflux proteins in doxorubicin-sensitive and -resistant HL60 cells revealed that there was an upregulation of MRP1 gene in HL60/DOX cells as compared to parental sensitive cells. On the other hand, while there was no expression of MDR1 gene in parental cells, the expression of MDR1 gene was upregulated in HL60/DOX cells. HL60/DOX cells also showed cross-resistance to cytosine arabinoside (Ara-c). This resistance was reversed by a combination therapy of Ara-c and cyclosporine A. However, the expression levels of CD15 and CD16 surface markers were significantly decreased in HL60/DOX cells.

Treatment by design in leukemia, a meeting report, Philadelphia, Pennsylvania, December 2002

Novel approaches have been designed to treat leukemia based on our understanding of the genetic and biochemical lesions present in different malignancies. This meeting report summarizes some of the recent advances in leukemia treatment. Based on the discoveries of cellular oncogenes, chromosomal translocations, monoclonal antibodies, multidrug resistance pumps, signal transduction pathways, genomics/proteonomic approaches to clinical diagnosis and mutations in biochemical pathways, clinicians and basic scientists have been able to identify the particular genetic mutations and signal transduction pathways involved as well as design more appropriate treatments for the leukemia patient. This meeting report discusses these exciting new therapies and the results obtained from ongoing clinical trials. Furthermore, rational approaches to treat complications of tumor lysis syndrome by administration of the recombinant urate oxidase protein, also known as rasburicase, which corrects the biochemical defect present in humans, were discussed. Clearly, over the past 25 years, molecular biology and biotechnology has provided the hematologist/oncologist novel bullets in their arsenal that will allow treatment by design in leukemia.

Quinine as a multidrug resistance inhibitor: a phase 3 multicentric randomized study in adult de novo acute myelogenous leukemia

Based on our previous demonstration that quinine could be used clinically to reverse P-glycoprotein-mediated resistance, we designed a multicenter, randomized trial aiming to determine whether quinine would improve the survival of adult patients (15-60 years old) with de novo acute myelogenous leukemia (AML). These patients randomly received (n = 213) or did not receive (n = 212) a 30 mg/kg/day continuous intravenous infusion of quinine in combination with induction chemotherapy combining idarubicine and cytarabine and, depending on bone marrow examination at day 20, an additional course of cytarabine and mitoxantrone. The mean steady-state quinine concentration was 7.8 mg/L and the mean multidrug resistance reversing activity of serum was 1.96. Complete remission (CR) was obtained in 344 patients (80.9%) without significant influence of quinine. Of the patients in complete remission, 82 were assigned to receive HLA-matched bone marrow transplants, whereas 262 were assigned to 2 courses of intensive consolidation chemotherapy, with or without quinine, depending on initial randomization. The 4-year actuarial overall survival (OS) of the 425 eligible patients was 42.0% +/- 2.5%, without significant influence of quinine. Of 160 patients who could be studied, 54 demonstrated rhodamine 123 efflux. In these patients, quinine significantly improved the CR rate from 12 of 25 (48.0%) to 24 of 29 (82.8%) (P =.01). However, there was no significant difference in OS. Neither mdr1 gene nor P-glycoprotein expression influenced the outcome. We conclude that quinine does not improve the survival of adult patients with de novo AML, even though it improves CR rate in a small subgroup of patients defined by rhodamine 123 efflux.