Treatment of second-and third-line patients with non-smallcell lung carcinoma (NSCLC) with the epidermal growth factor receptor (EGFR) kinase inhibitor erlotinib significantly increased survival relative to placebo. Whereas patient tumors with EGFR mutations have shown responses to EGFR inhibitors, an exclusive role for mutations in patient survival benefit from EGFR inhibition is unclear. Here we show that wild-type EGFR-containing human NSCLC lines grown both in culture and as xenografts show a range of sensitivities to EGFR inhibition dependent on the degree to which they have undergone an epithelial to mesenchymal transition (EMT). NSCLC lines which express the epithelial cell junction protein E-cadherin showed greater sensitivity to EGFR inhibition in vitro and in xenografts. In contrast, NSCLC lines having undergone EMT, expressing vimentin and/or fibronectin, were insensitive to the growth inhibitory effects of EGFR kinase inhibition in vitro and in xenografts. The differential sensitivity of NSCLC cells with epithelial or mesenchymal phenotypes to EGFR inhibition did not correlate with cell cycle status in vitro or with xenograft growth rates in vivo, or with total EGFR protein levels. Cells sensitive to EGFR inhibition, with an epithelial cell phenotype, did exhibit increased phosphorylation of EGFR and ErbB3 and a marked increase in total ErbB3. The loss of E-cadherin and deregulation of B-catenin associated with EMT have been shown to correlate with poor prognosis in multiple solid tumor types. These data suggest that EMT may be a general biological switch rendering non-small cell lung tumors sensitive or insensitive to EGFR inhibition. (Cancer Res 2005; 65(20): 9455-62)

OSI-906 is a novel, potent, selective and orally bioavailable dual IGF-1R/IR kinase inhibitor with favorable preclinical drug-like properties, which has demonstrated in vivo efficacy in tumor models and is currently in clinical testing.

Insulin-like growth factor-1 receptor (IGF-1R) is a receptor tyrosine kinase (RTK) and critical activator of the phosphatidylinositol 3-kinase-AKT pathway. IGF-1R is required for oncogenic transformation and tumorigenesis. These observations have spurred anticancer drug discovery and development efforts for both biological and small-molecule IGF-1R inhibitors. The ability for one RTK to compensate for another to maintain tumor cell viability is emerging as a common resistance mechanism to antitumor agents targeting individual RTKs. As IGF-1R is structurally and functionally related to the insulin receptor (IR), we asked whether IR is tumorigenic and whether IR-AKT signaling contributes to resistance to IGF-1R inhibition. Both IGF-1R and IR(A) are tumorigenic in a mouse mammary tumor model. In human tumor cells coexpressing IGF-1R and IR, bidirectional cross talk was observed following either knockdown of IR expression or treatment with a selective anti-IGF-1R antibody, MAB391. MAB391 treatment resulted in a compensatory increase in phospho-IR, which was associated with resistance to inhibition of IRS1 and AKT. In contrast, treatment with OSI-906, a small-molecule dual inhibitor of IGF-1R/IR, resulted in enhanced reduction in phospho-IRS1/phospho-AKT relative to MAB391. Insulin or IGF-2 activated the IR-AKT pathway and decreased sensitivity to MAB391 but not to OSI-906. In tumor cells with an autocrine IGF-2 loop, both OSI-906 and an anti-IGF-2 antibody reduced phospho-IR/phospho-AKT, whereas MAB391 was ineffective. Finally, OSI-906 showed superior efficacy compared with MAB391 in human tumor xenograft models in which both IGF-1R and IR were phosphorylated. Collectively, these data indicate that cotargeting IGF-1R and IR may provide superior antitumor efficacy compared with targeting IGF-1R alone. Mol Cancer Ther; 9(10); 2652-64. ©2010 AACR.

The receptor for epidermal growth factor (EGFR) is overexpressed in many cancers. One important signaling pathway regulated by EGFR is the phosphatidylinositol 3'-kinase (PI3K)-phosphoinositide-dependent kinase 1-Akt pathway. Activation of Akt leads to the stimulation of antiapoptotic pathways, promoting cell survival. Akt also regulates the mammalian target of rapamycin (mTOR)-S6K-S6 pathway to control cell growth in response to growth factors and nutrients. Recent reports have shown that the sensitivity of non-small-cell lung cancer cell lines to EGFR inhibitors such as erlotinib (Tarceva, OSI Pharmaceuticals) is dependent on inhibition of the phosphatidylinositol 3'-kinase-phosphoinositide-dependent kinase 1-Akt-mTOR pathway. There can be multiple inputs to this pathway as activity can be regulated by other receptors or upstream mutations. Therefore, inhibiting EGFR alone may not be sufficient for substantial inhibition of all tumor cells, highlighting the need for multipoint intervention. Herein, we sought to determine if rapamycin, an inhibitor of mTOR, could enhance erlotinib sensitivity for cell lines derived from a variety of tissue types (non-small-cell lung, pancreatic, colon, and breast). Erlotinib could inhibit extracellular signal-regulated kinase, Akt, and S6 only in cell lines that were the most sensitive. Rapamycin could fully inhibit S6 in all cell lines, but this was accompanied by activation of Akt phosphorylation. However, combination with erlotinib could down-modulate rapamycin-stimulated Akt activity. Therefore, in select cell lines, inhibition of both S6 and Akt was achieved only with the combination of erlotinib and rapamycin. This produced a synergistic effect on cell growth inhibition, observations that extended in vivo using xenograft models. These results suggest that combining rapamycin with erlotinib might be clinically useful to enhance response to erlotinib.

Epidermal growth factor receptor (EGFR) and insulin-like growth factor