Among patients with non-small-cell lung cancer who receive erlotinib, the presence of an EGFR mutation may increase responsiveness to the agent, but it is not indicative of a survival benefit.

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.

Stable expression of high levels of activated forms of Haras (T24) or v‐Ki‐ras by transfection of Chinese hamster lung fibroblasts (CCL39) yielded cells highly tumorigenic in nude mice. Two classes of transformed cells were distinguished, one with moderate p21 expression (10‐fold increased) had retained growth factor dependency, the second with higher level of p21 (greater than 50‐fold) appeared autonomous for growth. Neither class of transformants expressing Ki‐ras or Ha‐ras displayed a significant basal activity of polyphosphoinositide‐specific phospholipase C, measured either in serum‐starved cells or during exponential growth in the presence of growth factors of the tyrosine kinase family (EGF, FGF, insulin). In the growth‐factor‐dependent class of T24‐Ha‐ras‐transfected cells (clone 39THaB), phospholipase C could be stimulated normally by serum, thrombin and AlF‐4. In the more growth autonomous class (clones 39THaC and 39Ki9), release of inositol phosphates after stimulation with thrombin or serum was drastically reduced. This desensitization, apparently at the receptor level since the response to AlF‐4 persisted, is, however, not specific to ras expression. We observed it to the same degree in polyoma virus‐transformed CCL39 cells. Finally, expression of mutated forms of p21 ras did not abrogate the sensitivity of phospholipase C activation to pertussis toxin. We conclude that the transforming potential of activated forms of p21ras does not result from persistent activation of phospholipase C and that ras GTP‐binding proteins cannot substitute for Gp.

Previous studies demonstrated that growth in DBA/2 mice of MDW4, a wheat germ agglutinin-resistant (WGA9 mutant of the highly metastatic MDAY-D2 DBA/2 mouse tumor, led to the emergence of WGA-sensitive (WGAS) revertants having higher ploidy levels at the site of inoculation as well as at distant visceral metastases. The results implied that MDW4 was nonmetastatic but progressed to become metastatic in vivo only after a cellular change took place which was accompanied by extinction of the WGAr phenotype and acquisition of a higher number of chromosomes. Results presented here provide strong and direct evidence for the underlying mechanism being spontaneous cell fusion in vivo between the MDW4

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