Abstract 2152: TNIK, a novel activator of FAK and YAP signaling, is a therapeutic target in lung squamous cell carcinoma

Lung squamous cell carcinoma (LSCC) is the second most common type of lung cancer. No precision therapies have been approved for the treatment of LSCC and the genetic drivers of LSCC are unknown in approximately 60% of the cases. As a result, treatment of LSCC is still limited to chemotherapy and/or radiotherapy. Analysis of LSCC samples from the TCGA reveals that nearly 50% of LSCC patients harbor distal amplification of the 3q chromosome that includes the resident protein kinase gene TNIK. Recent studies have pinpointed TNIK as a potential oncogenic driver in cancer cells with distal 3q amplification (Cancer Discov. 2013; 3:1044). However, the therapeutic potential of TNIK in LSCC remains unexplored. To determine if amplified TNIK is a genetic driver in LSCC, we analyzed TNIK expression in a panel of LSCC cell lines. We show that TNIK is overexpressed in LSCC cell lines in comparison with primary lung cells from healthy donors, consistent with observations in patient tumors based on analysis of TCGA data. Furthermore, we demonstrate that TNIK genetic depletion or pharmacological inhibition significantly reduces survival of LSCC cells with 3q amplification in vitro and in in vivo LSCC cell-line derived mouse xenografts. Importantly, we have generated LSCC patient-derived xenograft (PDX) mouse models to test TNIK inhibitors and have observed that inhibition of TNIK catalytic activity suppresses tumor growth in LSCC PDX mouse models. To elucidate the molecular mechanisms underpinning TNIK-driven LSCC cell viability we have used a combination of reverse-phase protein arrays, motif-driven screens for proteins with TNIK consensus phosphorylation sites, co-expression experiments, peptide mapping and mass spectrometry. Through these approaches, we have identified the tumor suppressor MERLIN as a novel TNIK substrate and determined that TNIK phosphorylates MERLIN at Ser13, Thr272 and Thr576. We also demonstrate that TNIK is required for stabilization of the YAP transcription factor, and activation of the focal adhesion kinase, FAK, two oncogenic pathways that are inhibited by MERLIN. In conclusion, we have pinpointed the protein kinase TNIK as a promising therapeutic target in LSCC that maintains survival of LSCC cells through modulation of novel a TNIK-MERLIN-YAP/FAK signaling pathway. Citation Format: Pedro Torres-Ayuso, Elvira An, Katherine M. Nyswaner, Daniel A. Ritt, Suzanne I. Specht, Sudipto Das, Thorkell Andresson, Christina M. Robinson, Simone Difilippan