Antitumor activity of selective MEK1/2 inhibitor AZD6244 in combination with PI3K/mTOR inhibitor BEZ235 in gefitinib-resistant NSCLC xenograft models

Abstract

PurposeAlthough the EGF receptor tyrosine kinase inhibitors (EGFR-TKI) gefitinib have shown dramatic effects against EGFR mutant lung cancer, patients become resistant by various mechanisms, including gatekeeper EGFR-T790M mutation, MET amplification, and KRAS mutation, thereafter relapsing. AZD6244 is a potent, selective, and orally available MEK1/2 inhibitor. In this study, we evaluated the therapeutic efficacy of AZD6244 alone or with BEZ235, an orally available potent inhibitor of phosphatidylinositol 3–kinase (PI3K) and mammalian target of rapamycin (mTOR), in gefitinib-resistant non-small cell lung carcinoma (NSCLC) models.Experimental designNCI-H1975 with EGFR-T790M mutation, NCI-H1993 with MET amplification and NCI-H460 with KRAS/PIK3CA mutation human NSCLC cells were subcutaneous injected into the athymic nude mice respectively. Mice were randomly assigned to treatment with AZD6244, BEZ235, AZD6244 plus BEZ235, or control for 3 weeks, then all mice were sacrificed and tumor tissues were subjected to western blot analyses and immunohistochemical staining.ResultsAZD6244 could inhibit the tumor growth of NCI-H1993, but slightly inhibit the tumor growth of NCI-1975 and NCI-H460. Combining AZD6244 with BEZ235 markedly enhanced their antitumor effects and without any marked adverse events. Western blot analysis and immunohistochemical staining revealed that AZD6244 alone reduced ERK1/2 phosphorylation, angiogenesis, and tumor cell proliferation. Moreover, MEK1/2 inhibition resulted in decreased AKT phosphorylation in NCI-H1993 tumor model. BEZ235 also inhibited AKT phosphorylation as well as their downstream molecules in all three tumor models. The antiangiogenic effects were substantially enhanced when the agents were combined, which may due to the reduced expression of matrix metallopeptidase-9 in tumor tissues (MMP-9).ConclusionsIn this study, we evaluated therapy directed against MEK and PI3K/mTOR in distinct gefitinib-resistant NSCLC xenograft models. Combining AZD6244 with BEZ235 enhanced their antitumor and antiangiogenic effects. We concluded that the combination of a selective MEK inhibitor and a PI3K/mTOR inhibitor was effective in suppressing the growth of gefitinib-resistant tumors caused by EGFR T790M mutation, MET amplification, and KRAS/PIK3CA mutation. This new therapeutic strategy may be a practical approach in the treatment of these patients.

The comparison between dual inhibition of mTOR with MAPK and PI3K signaling pathways in KRAS mutant NSCLC cell lines

“…It was shown that AZD6244 was not effective at inhibiting H460 injected athymic nude mice tumors. However, AZD6244 and BEZ235 combination reduced cell viability and tumor volume [40]. Hata et al determined MEK and PI3K inhibitor combinations do not cause apoptosis in most human KRAS mutant NSCLC cell lines.…”

Expression of EGFR and Molecules Downstream to PI3K/Akt, Raf-1-MEK-1-MAP (Erk1/2), and JAK (STAT3) Pathways in Invasive Lung Adenocarcinomas Resected at a Single Institution

“…While therapies targeting EGFR and, more recently, ALK are effective in treating tumors that harbor molecular alterations, there is heterogeneity in results due to the complexity of signaling pathways involved both in oncogenesis and in acquired resistance. Therefore, analyses of other molecular signatures and profiles in protein expression may be critical in understanding the development in effective new drugs and combinations [ 7 – 11 ].…”

“…The activation of the downstream molecules Akt and the signal transduction and activator of transcription (STAT), which promotes cell survival, may be responsible for resistance to apoptosis induced by therapies [ 13 ]. Another pathway that may act in the inhibition of apoptosis is the ERK1/2 pathway [ 11 , 14 , 15 ]. Furthermore, enzyme repair cross-complementation group 1 (ERCC1) also plays a key role in excision repair enzyme pathways and its expression has been suggested to correlate with survival in lung carcinomas, as well as predicting sensitivity to platinum-based chemotherapy [ 16 – 19 ].…”

Preclinical activity of EGFR and MEK1/2 inhibitors in the treatment of biliary tract carcinoma

“…The antiangiogenic role of another MEK inhibitor, Selumetinib, was previously reported in lung cancer cells resistant to anti-EGFR therapies [29]. Further, Trametinib demonstrated an anti-angiogenetic activity also in HUVEC cells but not in in vivo model of renal cell carcinoma [30].…”