Preclinical emergence of vandetanib as a potent antitumour agent in mesothelioma: molecular mechanisms underlying its synergistic interaction with pemetrexed and carboplatin

BACKGROUND: Although pemetrexed, a potent thymidylate synthase (TS) inhibitor, enhances the cytoytoxic effect of platinum compounds against malignant pleural mesothelioma (MPM), novel combinations with effective targeted therapies are warranted. To this end, the current study evaluates new targeted agents and their pharmacological interaction with carboplatin-pemetrexed in human MPM cell lines. METHODS: We treated H2052, H2452, H28 and MSTO-211H cells with carboplatin, pemetrexed and targeted compounds (gefitinib, erlotinib, sorafenib, vandetanib, enzastaurin and ZM447439) and evaluated the modulation of pivotal pathways in drug activity and cancer cell proliferation. RESULTS: Vandetanib emerged as the compound with the most potent cytotoxic activity, which interacted synergistically with carboplatin and pemetrexed. Drug combinations blocked Akt phosphorylation and increased apoptosis. Vandetanib significantly downregulated epidermal growth factor receptor (EGFR)/Erk/Akt phosphorylation as well as E2F-1 mRNA and TS mRNA/protein levels. Moreover, pemetrexed decreased Akt phosphorylation and expression of DNA repair genes. Finally, most MPM samples displayed detectable levels of EGFR and TS, the variability of which could be used for patients' stratification in future trials with vandetanib-pemetrexed-carboplatin combination. CONCLUSION: Vandetanib markedly enhances pemetrexed-carboplatin activity against human MPM cells. Induction of apoptosis, modulation of EGFR/Akt/Erk phosphorylation and expression of key determinants for pemetrexed and carboplatin activity contribute to this synergistic interaction, and, together with the expression of these determinants in MPM samples, warrant further clinical investigation