Abrogating G₂/M checkpoint through WEE1 inhibition in combination with chemotherapy as a promising therapeutic approach for mesothelioma

Abstract

Malignant mesothelioma (MM) is a very aggressive asbestos-related neoplasm of the serous membranes, whose incidence is increasing worldwide. Although the introduction of new drug combinations, such as cisplatin plus pemetrexed/gemcitabine, has determined an improvement in the patient quality of life, MM remains a universally fatal disease. The observation that key G₁/S checkpoint regulators are often functionally inactivated in MM prompted us to test whether the use of G₂/M checkpoint inhibitors, able to sensitize G₁/S checkpoint-defective cancer cells to DNA-damaging agents, could be successful in MM. We treated six MM cell lines, representative of different histotypes (epithelioid, biphasic, and sarcomatoid), with cisplatin in combination with MK-1775, an inhibitor of the G₂/M checkpoint kinase WEE1. We observed that MK-1775 enhanced the cisplatin cytotoxic effect in all MM cell lines, except the sarcomatoid cell line, which is representative of the most aggressive histotype. As expected, the enhancement in cisplatin toxicity was accompanied by a decrease in the inactive phosphorylated form of cyclin-dependent kinase 1 (CDK1), a key substrate of WEE1, which is indicative of G₂/M checkpoint inactivation. Consistently, we also observed a decrease in G₂/M accumulation and an increase in mitotic entry of DNA-damaged cells and apoptosis, probably due to the loss of the cell ability to arrest cell cycle in response to DNA damage, irrespectively of p53 mutational status. Notably, this treatment did not increase cisplatin cytotoxicity on normal cells, thus suggesting a possible use of MK-1775 in combination with cisplatin for a safe and efficient treatment of epithelioid and biphasic MM.

Keywords: :

• WEE1
• MK-1775
• cisplatin
• mesothelioma
• CDK1
• G2/M checkpoint
• apoptosis

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Disclosure of Potential Conflicts of Interest

No potential conflict of interest was disclosed.

Acknowledgments

This study was supported by the Sbarro Health Research Organization (http://www.shro.org), Human Health Foundation (http://www.hhfonlus.org), Fondazione T. and L. de Beaumont Bonelli (http://www.giuliotarro.it) and the Commonwealth of Pennsylvania. The authors wish to thank Giovanni Gaudino (University of Hawaii Cancer Center, Manoa) for providing REN cells; Michele Fimiani, Giancarlo Mariotti, and Stefania Mei (University of Siena, Italy) for providing primary human skin fibroblasts; Laura Pisapia and Pasquale Barba (Consiglio Nazionale delle Ricerche-Institute of Genetics and Biophysics, Naples, Italy) for FACS analyses; and Carmelina Antonella Iannuzzi for technical help.