Abstract B54: Characterizing pathway vulnerabilities and tumor heterogeneity through signaling-associated complexes

Signaling pathways controlling cellular proliferation are major targets of cancer therapeutics, however, accurate assessment of activation status of targetable signaling cascades remains a challenge. We have developed proximity ligation assay (PLA)-based methodologies to detect signaling-associated complexes for a variety of receptor tyrosine kinases, intracellular adaptors and phosphorylation events in formalin-fixed, paraffin-embedded tissues. By assessing the degree of functional association of oncogenic kinases (such as EGFR and ALK) with intracellular adaptor molecules, it is possible to characterize the activation status of targetable kinase activity and monitor variations across tissue types, within tissues and in response to perturbations. Here, we present data for a panel of PLAs using cell lines, patient specimens and patient-derived xenografts models. We show that EGFR-GRB2 PLA reflects erlotinib pharmacodynamics and has predictive capacity for response to both erlotinib and cetuximab. We demonstrate that PLA can identify alterations in multiple bypass signaling cascades associated with therapeutic escape using both in vitro models of acquired resistance and patient specimens. We observe striking intratumoral variation in abundance of signaling-associated complexes, likely reflecting influences from the tumor microenvironment and phenotypic heterogeneity. We are currently expanding our PLA panel to include emerging therapeutic targets (MET and FGFR1) and evaluating performance of these assays to characterize signaling complexes in circulating tumor cells obtained from advanced stage non-small cell lung cancer patients. Collectively, our data suggests that PLA-based methodologies can be harnessed to explore the cancer interactome and can be important tools to enable precision medicine. Citation Format: Matthew A. Smith, Leah Clark, Richard Hall, Kate Fisher, Takeshi Yoshida, Vincent Vuaroqueaux, Heinz-Herbert Fiebig, Ann Chen, Eric B. Haura. Characterizing pathway vulnerabilities and tumor heterogeneity through signaling-associated complexes. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Drug Sensitivity and Resistance: Improving Cancer Therapy; Jun 18-21, 2014; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(4 Suppl): Abstract nr B54.