Abstract 4377: The role of Src in TRAIL signaling in non-small cell lung cancer cells
Authors: Looff Margot de , Jong Steven de , Kruyt Frank A.E. 
Published: August 2018

Abstract
Introduction: Non-small cell lung cancer (NSCLC) is the most prevalent form of lung cancer and accounts for most cancer-related deaths worldwide. Despite progress in the treatment of subgroups of patients with targeted therapies, better treatments are required to improve overall prognosis. Agents that target the tumor-necrosis factor (TNF) related apoptosis-inducing ligand (TRAIL) receptors (TRAIL-R1 and -R2) are able to trigger selective apoptosis in tumor cells, however showed discouraging activity in clinical studies. Resistance to TRAIL-induced apoptosis and non-canonical pro-tumorigenic signaling hampers therapeutic efficacy. Previously, we found that TRAIL induces migration and invasion via RIPK1/Src/STAT3 pathway in apoptosis resistant NSCLC cells. Here we aim to analyze in more detail the role of Src in TRAIL non-canonical signaling and apoptosis resistance.
Methods: Cytotoxicity to rhTRAIL was assessed by MTT assays. Src was chemically inhibited or genetically ablated by short hairpin(sh)RNA or CRISPR/CAS9. Src phosphorylation was studied by western blotting. Protein interactions were examined by co-immunoprecipitation (IP) and subsequent western blotting. Src interacting proteins were examined by co-IP experiments in conjunction with LC-mass spectrometric (MS) analyses.
Results: The function of Src in TRAIL signaling was examined in TRAIL resistant A549 and sensitive H460 NSCLC cells. rhTRAIL treatment revealed distinct Src phosphorylation patterns, indicating that Src is differentially activated by TRAIL. Subsequently, co-IP experiments were performed showing that in A549 cells Src interacts with RIPK1 and Caspase-8 upon TRAIL treatment, but not in H460 cells. Next, we explored the possible role of Src in regulating TRAIL-induced apoptosis by chemical modulation of Src or by gene silencing or genetic knockout of Src. We found no role for Src in regulating sensitivity or resistance to TRAIL-induced apoptosis. To further investigate possible biological consequences of TRAIL-dependent Src activation we performed co-IP coupled with LC-MS analysis. Abundant differences were found in the Src interactome of A549 and H460 cells and in absence and presence of TRAIL. Various proteins known to be involved in tumor signaling were identified to be in complex with Src, including components of the RAF/MEK/ERK, Wnt and SMAD3 signaling pathways. Currently, mechanistic and validation studies are in progress to elucidate the role of these proteins.
Conclusions: Src has no role in controlling sensitivity or resistance to TRAIL-induced apoptosis in the examined NSCLC cells. On the contrary, the Src interactome showed the activation of various pro-tumorigenic pathways by TRAIL. We anticipate that a deeper knowledge of TRAIL signaling will lead to novel therapeutic strategies to improve TRAIL-receptor targeted therapy. Supported by a grant from the Dutch Cancer Society (KWF 2011-5211).
Citation Format: Margot de Looff, Steven de Jong, Frank A.E. Kruyt. The role of Src in TRAIL signaling in non-small cell lung cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4377.