Selective Killing of Adriamycin-Resistant (G2 Checkpoint-Deficient and MRP1-Expressing) Cancer Cells by Docetaxel

Zoya N. Demidenko, Dorota Halicka, Jan Kunicki, James A. McCubrey, 

Zbigniew Darzynkiewicz and Mikhail V. Blagosklonny

DOI: 10.1158/0008-5472.CAN-04-4428 Published May 2005

Abstract

Chemotherapy of cancer is limited by toxicity to normal cells. Drug resistance further limits the therapy. Here, we investigated selective killing of drug-resistant cancer cells by antagonistic drug combinations, which can spare (because of drug antagonism) normal cells. We used paired cell lines that are resistant to Adriamycin due to either expression of MRP1 or lack of G2 checkpoints. The goal was to selectively kill Adriamycin-resistant cancer cells with Docetaxel (Taxotere), while protecting parental (Adriamycin-sensitive) cells, using cytostatic concentrations of Adriamycin. Taxotere kills cells in mitosis. Therefore, by arresting parental cells in G2, 20 to 40 ng/mL of Adriamycin prevented cell death caused by Taxotere. Also, Adriamycin prevented the effects of Taxotere in normal human lymphocytes. In contrast, Taxotere selectively killed MRP1-expressing leukemia cells, which did not undergo G2 arrest in the presence of Adriamycin. Also, in the presence of Adriamycin, HCT116-p21−/− cancer cells with a defective G2 checkpoint entered mitosis and were selectively killed by Taxotere. Finally, 20 ng/mL of Adriamycin protected normal FDC-P1 hematopoietic cells from Taxotere. Whereas parental cells were protected by Adriamycin, the mitogen-activated protein/extracellular signal-regulated kinase inhibitor PD90598 potentiated the cytotoxic effect of Taxotere selectively in Raf-1–transformed FDC-P1 leukemia cells. We propose a therapeutic strategy to prevent normal cells from entering mitosis while increasing apoptosis selectively in mitotic cancer cells.

Introduction

Microtubules represent one of the best drug targets identified to date ( 1– 5). Docetaxel (Taxotere), a microtubule-stabilizing taxane, is widely used in the therapy of breast, ovarian, prostate, lung, head and neck, gastric, bladder and other cancers ( 6– 9). Yet, microtubules are universal cellular structures that are necessary for all normal cells. As a consequence, all microtubule-active agents cause dose-limiting side effects ( 10, 11).

Microtubule dynamics is much faster during mitosis (M) than during interphase (G1, S, G2) of the cell cycle ( 2). At low concentrations, which do not cause polymerization of tubulin, taxanes inhibit mitotic progression ( 2, 12). Numerous studies indicate that inhibition of mitotic progression and mitotic arrest correlate with the cytotoxicity of microtubule-active drugs ( 13– 21). When arrested in G1 and/or G2, cells are resistant to microtubule-active drugs ( 22– 27). DNA-damaging agents cause G1 and/or G2 arrest ( 28). In particular, low concentrations of Adriamycin can cause G2 arrest without apoptosis. Therefore, low concentrations of Adriamycin can protect cells from microtubule-active drugs ( 24, 26). But how can we arrest normal cells in G2 without arresting cancer cells? First, cancer cells may have defective G2 checkpoints ( 29– 31). Following DNA damage, such cancer cells continue to proliferate and enter mitosis ( 28). Second, cancer cells may acquire drug resistance, for instance, due to expression of MRP1 ( 32). Adriamycin is a substrate of MRP1, whereas Taxotere is not ( 33, 34). In the presence of low concentrations of Adriamycin, in theory, Taxotere could kill MRP1-expressing cells selectively. Here we investigated these scenarios. We showed that following pretreatment with low concentrations of Adriamycin, Taxotere selectively killed MRP1-expressing and G2 checkpoint–deficient cells. We also determined a protective window: namely, concentrations of Adriamycin that arrest cell cycle without causing cell death. Finally, the mitogen-activated protein/extracellular signal-regulated kinase (MEK) inhibitor PD90859 potentiated the effects of Taxotere in Raf-1-transformed cells arrested in mitosis, whereas normal FDC-P1 hematopoietic cells were protected by Adriamycin. https://cancerres.aacrjournals.org/content/65/10/4401.article-info

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