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Roscovitine, a small molecule CDK inhibitor induces apoptosis in multidrug-resistant human multiple myeloma cells
O. Komina, E. Noßke, M. Maurer and J. Wesierska-Gadek

Small molecule inhibitors of cyclin-dependent kinases (CDKs) show high therapeutic potential against rapidly dividing cancers and malignancies, characterized by the accumulation of transformed cells due to deregulation of apoptosis, such as multiple myeloma. In the present study we addressed the possibility that pharmacological CDK inhibitors like Roscovitine (ROSC) may be effective against human multiple myeloma cells that have acquired resistance to doxorubicin (DOX). For this purpose we selected an experimental model of human multiple myeloma-sensitive (RPMI-8226S) and doxorubicin-resistant (RPMI-8226DOX40) cell lines. Exposure of RPMI-8826 cells to ROSC markedly increased the proportion of hypoploid cells, representing cells undergoing apoptosis, in both sensitive and resistant cells. Unlike ROSC, DOX at high dosage did not elevate the apoptosis rate in the RPMI-8226DOX40 cell line. Our results show that ROSC has the capacity to induce apoptosis in the RPMI-8226DOX40 cells overexpressing the P-gp glycoprotein. Since ROSC not only inhibits cell cycle-related CDKs but also negatively regulates kinases involved in the regulation of transcription, its administration to quiescent multidrug-resistant cells might be advantageous. Inhibition of transcription of pro-survival genes such as BCL2 and MCL-1 as well as destabilization of survivin seems to improve its therapeutic efficacy.

Keywords: Caspase-3 activation; doxorubicin; MDR1; P-gp; RPMI-8226 cells; ts p53 mutant; wt p53

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