Lung cancer is the leading cause of cancer death in the United States, with the majority of patients having non-small cell lung cancer (NSCLC). The 3rd most commonly mutated gene in NSCLC adenocarcinoma is the serine/threonine kinase LKB1, where ~25,000 patients have this mutation. Targeted therapies for LKB1 mutant patients do not exist thereby creating a significant unmet clinical need. In a transgenic genetically engineered mouse model (GEMM), the combination of Lkb1 and Kras mutations promote metastasis and create treatment-refractory tumors compared to Kras-only mice. Genomic and proteomic profiling show that these mice have increased expression of pro-metastatic pathways, notably the focal adhesion kinase (FAK). We published that LKB1 is indeed a FAK repressor in vitro, such that when LKB1 is absent, phosphorylated FAK (pFAK397) is hyperactivated. Consistent with this work, we now present preliminary in vivo data that pFAK397 is activated at the invasive front of high-grade metastatic tumors within the KrasG12D Lkb1fl/fl GEMM. This prompted us to test the intriguing possibility that pharmacologic FAK inhibition in this GEMM would repress metastasis due to pFAK397 inhibition. Our preliminary data show that treatment with a FAK inhibitor suppresses the rate of metastasis, suggesting that targeting FAK can be a viable anti-metastatic strategy for treating LKB1 mutant tumors. Similarly, FAK inhibitor treatment using in vitro Lkb1 null spheroids also potently inhibits invasion and suppresses pFAK397 activation. Based upon these preliminary and published data, we hypothesize that LKB1 inactivation in NSCLC represents a unique acquired tumor vulnerability that can be targeted pharmacologically with a FAK inhibitor. To test this hypothesis the objectives of this proposal are i) to determine if pharmacologic FAK inhibition can specifically suppress the metastasis of Lkb1-mutant lung tumors in vivo and ii) define which clinically observed LKB1 mutations cause pFAK397 activation and create a tumor vulnerability targetable by pharmacologic FAK inhibition. These objectives will be met by performing pre-clinical mouse trials in a unique and clinically-relevant GEMM to examine FAK inhibition as a strategy for inhibiting metastatic disease in Lkb1 mutant tumors. In addition, we will implement a novel LKB1 sequencing pipeline in patient samples from our clinically-annotated tumor bank, and determine if specific LKB1 mutations correlate with pFAK activation and clinical outcome. We have assembled a team of interdisciplinary investigators to facilitate the translational and multi-pronged nature of these studies. Since FAK inhibitors are in Phase I and II trials, we propose that the data from this proposal will provide a rational foundation to develop a future trial with FAK inhibitor specifically targeting patients with LKB1 loss-of-function mutations.
LKB1 is mutated in 20-30% of non-small cell lung cancers and ranks as the 3rd most frequently mutated gene in lung adenocarcinoma. LKB1 is a master regulator of lung cancer metastasis and its inactivation leads to increased phosphorylation of the key cell adhesion protein, focal adhesion kinase (FAK); therefore, the goal of this application is to determine if a pharmacological FAK inhibitor could serve as a viable treatment for patients with LKB1 mutations.
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