Targeting SRC tyrosine kinase to overcome resistance to HER-inhibitors in humancancer

Inhibition of the human epidermal growth factor receptor (HER) signalling by antibodies or small molecules has been pursued as a paradigm to treat different type of human cancers. These targeted agents are able to induce tumor regressions and prolong survival of cancer patients, proving the critical role of HER related signal transduction pathways for tumor growth and maintenance. The clinical benefit observed with this new anticancer agents is, however, limited to a subset of patients, clinically meaningful responses are often only transient and the development of resistance, even in responders, is sooner or later observed. Several studies have provided new insights into the molecular basis of HER inhibitors resistance, such as activation of other tyrosine kinase receptors, loss of function of intracellular suppressors, activation of angiogenesis, mutations of key signalling transducers. In this respect our research group has contributed to the rational design of treatment strategies, from preclinical to clinical applications, based on the functional role of the target and to the development of combination treatments based on the identification and combined blockade of signalling proteins acting as “escape” pathways and responsible for resistance to targeted drugs. This research proposal is aimed to investigate the role of SRC tyrosine kinase in human cancer cell models of constitutive or acquired resistance against HER inhibitors, elucidating the mechanistic insights that may correlate SRC activity and response to targeted agents. To accomplish this task we will conduct studies in vitro and in vivo, in cell lines and in human tumors generated by our group, either sensitive or resistant to anti-HER and other targeted agents. In particular, this research proposal will primarily focus on human colorectal and breast cancer cell models. Preliminary data obtained in our laboratory seem to correlate resistance to anti-HER agents and increased SRC-mediated anti-apoptotic signalling, mainly dependent from sphingosine kinase-1 (SPHK1) activation. To better investigate these findings, we will study the role of signalling proteins responsible for SRC-dependent tumor growth and invasion, trying to unmask its play in conditioning the resistant phenotype and to define biological correlations with well know determinants of resistance, such as KRAS mutations. To this aim we will use biochemical, molecular biology, imaging and histochemical and molecular pathology techniques taking advantage of the expertise of collaborating groups. Large protein expression and activation evaluations will be performed with proteomic and phosphoproteomic analyses on cancer cells and tissues. In addition to that, we plan to identify new biomarkers of response/resistance in cancer patient surgical samples through Tissue MicroArray-based analysis, in order to confirm in vivo the results obtained from in vitro experiments. Our studies should provide the opportunity to design new treatment combination and schedule strategies to be easily transferred into clinical practice and to better select patients to be treated with novel targeted agents.