GPCR Signaling in SCCHN: Integration with EGFR

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ABSTRACT Head and neck squamous cell carcinomas (HNSCC) are frequently lethal and predictive biomarkers to guide therapy are lacking. EGFR targeting was FDA-approved in 2006 for HNSCC. EGFR signaling is activated by direct stimulation and transactivation by G-protein-coupled receptors (GPCR). We previously identified GPCR- induced activation of phosphoinositide-3-kinase (PI3K) both upstream and downstream of EGFR. Co-targeting of PI3K in combination with EGFR inhibition was associated with enhanced antitumor effects in HNSCC preclinical models. We recently completed a randomized, placebo-controlled, window-of-opportunity clinical trial where treatment with erlotinib plus the GPCR inhibitor/NSAID sulindac significantly reduced tumor proliferation. Aspirin, like sulindac, inhibits cyclooxygenase (COX) and GPCR signaling. A recent study in colon cancer reported that aspirin use in patients whose tumors harbored PIK3CA mutations was associated with significantly longer survival compared with patients whose tumors contained wild-type (WT) PIK3CA. We have now determined the mutational profile of HNSCC and find PIK3CA genetic alterations in nearly 25% of tumors. Preliminary results indicate that PIK3CA mutation enhances sensitivity to NSAID treatment. As NSAIDs are well tolerated, this provides an immediate opportunity to implement potentially effective approaches for PIK3CA mutant HNSCC. We developed novel HNSCC models to identify oncogenic "driver" mutations in this cancer. In addition, we can assess PIK3CA mutation and amplification in human HNSCC tumors to be grown as heterotopic tumorgrafts in mice and in a HNSCC cohort with known NSAID use. This project will elucidate the role of PIK3CA alterations in mediating sensitivity to NSAIDs, alone or in combination with EGFR blockade in HNSCC.