More than 200,000 new cases and 160,000 deaths occur from lung cancer annually in the US, most from non-small cell lung cancer (NSCLC). The dismal outlook for patients with advanced NSCLC has prompted a search for more effective treatment strategies. New approaches are targeted against growth factors (EGF, VEGF), gene translocations (EML4-ALK), and oncogenes (RAS), but are applicable most commonly only to non-squamous subtypes of NSCLC. The most promising targeted therapy for squamous histology has had recent significant setbacks when trials of the IGF monoclonal antibody figitumumab failed to improve outcomes compared to chemotherapy alone and was associated with excess toxic deaths in the treatment arm. Since SCC patients account for ~40% of all NSCLC patients, there is a pressing need for more effective treatments. We demonstrated that the atypical PKC isozyme, PKCi, is an oncogene in NSCLC. PKCi is over-expressed in NSCLC cell lines and primary tumors, and PKCi expression may predict poor survival in NSCLC patients. The PKCi gene PRKCI is amplified in ~70% of SCC and PRKCI amplification drives elevated PKCi expression in these tumors. Genetic disruption of PKCi signaling blocks transformed growth of SCC cells in vitro and in vivo. We recently identified a small molecule PKCi inhibitor, aurothiomalate (ATM), which exhibits potent anti-tumor activity in NSCLC cells, particularly SCC cells harboring elevated PKCi expression as a result of PRKCI amplification. ATM disrupts the protein-protein interaction between PKCi and Par6, thereby inhibiting oncogenic PKCi signaling. ATM is FDA-approved for rheumatoid arthritis making it an attractive candidate for clinical development as an anti-tumor agent. We have established a safe dose for ATM in a phase I dose escalation clinical trial in advanced NSCLC patients. In preclinical studies, ATM exhibits synergistic anti-tumor activity against NSCLC tumor growth when combined with the mTOR inhibitor rapamycin. Based on these results, we hypothesize that ATM will be a safe and effective treatment for advanced SCC expressing elevated PKCi when used in combination with the mTOR inhibitor RAD001. This hypothesis will be tested in two interrelated specific aims.
In Aim 1 we will conduct a phase IB/II clinical trial to assess the safety and efficacy of combined therapy with ATM and RAD001 in the maintenance of advanced NSCLC patients.
In Aim 2 we will assess tumor and circulating blood biomarkers of PKCi and mTOR signaling as predictors of response to combined ATM/mTOR therapy. Successful completion of these aims will provide proof of principle for use of combined PKCi and mTOR targeted therapy in lung cancer and characterize candidate biomarkers that may be useful in identifying patients most likely to respond to this therapy.
Lung cancer is the number one cause of cancer death in the United States with a five year survival rate of approximately 15%. Protein kinase C9 (PKC9) is an oncogene and therapeutic target in lung cancer and a novel small molecule PKC9 inhibitor aurothiomalate (ATM) exhibits potent anti-tumor activity against lung cancer, especially when combined with an mTOR inhibitor. This project will assess the safety and efficacy of combined inhibition of PKC9 with ATM and mTOR with RAD001 in the maintenance therapy of patients with advanced squamous cell carcinoma of the lung, and assess the ability of surrogate markers of PKC9 and mTOR signaling to predict response to therapy.