Targeting the Mevalonate Pathway Inhibits the Function of the Epidermal Growth Factor Receptor

Abstract

Purpose: The epidermal growth factor receptor (EGFR) is a key regulator of growth, differentiation, and survival of epithelial cancers. In a small subset of tumors, the presence of activating mutations within the ATP binding site confers increased susceptibility to gefitinib, a potent tyrosine kinase inhibitor of EGFR. Agents that can inhibit EGFR function through different mechanisms may enhance gefitinib activity in patients lacking these mutations. Mevalonate metabolites play significant roles in the function of the EGFR; therefore, mevalonate pathway inhibitors may potentiate EGFRtargeted therapies.Experimental Design: In this study, we evaluated the effect of lovastatin on EGFR function and on gefitinib activity. Effects on EGFR function were analyzed by Western blot analysis using phosphospecific antibodies to EGFR, AKT, and extracellular signal-regulated kinase. Cytotoxic effects of lovastatin and/or gefitinib were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and flow cytometry.Results: Lovastatin treatment inhibited EGF-induced EGFR autophosphorylation by 24 hours that was reversed by the coadministration of mevalonate. Combining lovastatin and gefitinib treatments showed enhanced inhibition of AKT activation by EGF in SCC9 cells. The combination of 10 Mmol/L lovastatin and 10 Mmol/L gefitinib treatments showed cooperative cytotoxicity in all 8 squamous cell carcinomas, 4 of 4 non -small cell lung carcinoma and 4 of 4 colon carcinoma cell lines tested. Isobologram and flow cytometric analyses of three representative cell lines with wild-type EGFR ATP binding sites confirmed that this combination was synergistic inducing a potent apoptotic response.Conclusions: Taken together, these results show that targeting the mevalonate pathway can inhibit EGFR function. They also suggest the potential utility of combining these clinically relevant therapeutic approaches.

Lovastatin inhibits EGFR dimerization and AKT activation in squamous cell carcinoma cells: potential regulation by targeting rho proteins

“…Using EGFR-targeting agents requires combination-based therapies to enhance their clinical activity. Our recent studies have shown that the depletion of mevalonate metabolites affects the activity of a number of cell signaling cascades, including inhibitory effects on EGFR activity and their downstream signaling pathways (Mantha et al, 2005;Niknejad et al, 2007). Combinations of statins with agents targeting EGFR activity, such as gefitinib, induce a potent synergistic cytotoxic response in a variety of responsive tumor types, including SCC (Mantha et al, 2005).…”

“…Our recent studies have shown that the depletion of mevalonate metabolites affects the activity of a number of cell signaling cascades, including inhibitory effects on EGFR activity and their downstream signaling pathways (Mantha et al, 2005;Niknejad et al, 2007). Combinations of statins with agents targeting EGFR activity, such as gefitinib, induce a potent synergistic cytotoxic response in a variety of responsive tumor types, including SCC (Mantha et al, 2005). Combining these two approaches, with each targeting the EGFR through distinct mechanisms, represents a novel combinational therapeutic approach in SCC, as well as in other cancers in which EGFR is involved in their pathogenesis (Dimitroulakos et al, 2006).…”

“…Protein extracts representing 50-100 mg of total protein were separated on a 10% sodium dodecyl sulfatepolyacrylamide gel electrophoresis gel (unless otherwise stated) and western blots were performed as previously described (Mantha et al, 2005). The primary antibodies used were specific for phospho-AKT, AKT, phospho-S6K1, S6K1, phospho-4EBP1, 4EBP1, EGFR (Cell Signaling Technology, Danvers, MA, USA); phosphotyrosine (clone PY20), rhoA, rac1, cdc42, cyclinD1 (Santa Cruz Biotechnology, Santa Cruz, CA, USA); EGFR, pEGFR 1068 (Cell Signalling Technology); and actin (Sigma).…”

“…Cells were pretreated with control media, 10 nM rapamycin or 10 mM lovastatin for 24 h, followed by a 48 h treatment of gefitinib and assayed for 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide activity as previously described (Mantha et al, 2005). Treatments were performed in replicates of six and the means were expressed as the percentage viability relative to the untreated control (100% viable).…”

Efectos de las estatinas en cáncer: ¿potencial rol en terapéutica y prevención?

“…trastuzumab, gefitinib) resultaría en una mayor respuesta terapéutica por parte de algunos cánceres (ej. tumores gastrointestinales, mama, pulmón) [38][39][40] . Los autores, tal como muestra la Figura 4, han demostrado la Inhibición de invasión y metástasis inhibición de rho ↓expresión de metaloproteinasas de la matriz (MMP-9)…”