Abstract 4930: PAI1, a β catenin transcriptional target, serves as a surrogate biomarker to predict EGFR TKI mediated drug persistence in EGFR mutant NSCLC
Authors: Arasada Rajeswara Rao , Wang Walter , Suman Shankar , Carbone David Paul 
Published: August 2019

Abstract
Lung cancer management has been transformed by the discovery and effective targeting of driver mutations such as epidermal growth factor receptor (EGFR). Tyrosine Kinase Inhibitors (TKIs) that block EGFR kinase activity such as erlotinib and osimertinib cause dramatic tumor shrinkage and prolonged responses in patients whose tumors have activating EGFR mutations. However, resistance universally develops. Drug persister cells with properties of cancer stem cell-like cells play a major role in drug resistance. In tumors without pre-existing resistant clones, some tumor clonogens survive, despite expressing the driver mutation, to acquire target reactivation or bypass resistance mechanisms. Identification of biomarkers that are mechanistically linked to EGFR TKI resistant cell populations would have clinical utility in early determination of disease recurrence in EGFR mutant NSCLC patients.
Previously, we have reported that EGFR-TKI treatment activates Notch3, and here we have identified that Notch3 activates β-catenin transcriptional target, PAI1, which could play a role in drug persistence and could be used for early identification of disease recurrence. Our in vitro ELISA studies have identified an increase in secreted PAI1 levels after treatment with the EGFR TKIs erlotinib and osimertinib demonstrate that measuring PAI1 levels could serve as an indicator of EGFR TKI persistence. To further validate PAI1 as a surrogate biomarker for EGFR TKI treatment, we performed a retrospective study in NSCLC patients (n = 42) with EGFR mutant tumors. Using ELISA to detect PAI1 protein in pre- and post-treatment serum samples as a mechanism-based indicator for β-catenin activation, we observed a broad range in pre-treatment PAI1 levels, spanning from 0.8 ng/ml to 134 ng/ml, suggesting a variable baseline β-catenin activation. Doing survival analysis after dichotomizing patients into low and high baseline PAI1 level groups, we found patients with low basal PAI1 levels had a significantly shorter PFS with EGFR TKI treatment compared to patients with high basal levels. Comparing patients with a ≥ 2-fold induction to those with less than 2-fold, there was a similar trend for worsened survival in those who showed significant induction of PAI1.
Overall, we demonstrate that PAI1 expression is a candidate marker for β-catenin activation and the development of drug persisters; thus, it is a potential surrogate marker for poor outcome in patients receiving EGFR TKI therapy and a potential biomarker for selecting patients for β-catenin-targeted therapy.
Citation Format: Rajeswara Rao Arasada, Walter Wang, Shankar Suman, David Paul Carbone. PAI1, a β catenin transcriptional target, serves as a surrogate biomarker to predict EGFR TKI mediated drug persistence in EGFR mutant NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4930.