Abstract 1886: Role of PRMT1 and p120 catenin in mediating EMT and Osimeritinib resistance in NSCLC

Osimeritinib, a Tyrosine Kinase Inhibitor (TKI) has become a first-line therapy in EGFR-mutant NSCLC patients. Resistance to Osimeritinib treatment may occur due to acquired C797S mutations, MET amplifications and ALK rearrangements and other mechanisms not clearly defined. EMT may be one of the reasons for TKI resistance. EMT is a process by which epithelial cells acquire mesenchymal characteristics that increase invasiveness. We hypothesize that loss of E-cadherin during EMT, results in abnormal expression and localization of p120 catenin, an E-cadherin regulating protein, and Kaiso factor, a transcription repressor of Wnt signaling, promoting oncogenesis. Protein arginine methyl transferase 1 (PRMT1) an EMT regulator catalyzes the methylation of Twist1, which represses E-cadherin. However, the role of PRMT1, p120 catenin, and Kaiso factor in Osimeritinib resistance is still unknown. We earlier studied PRMT1/p120 catenin in NSCLC cell lines with and without EGFR mutations and determined their role in Erlotinib resistance. Recently, to study the resistance mechanisms, we have made parental (P) NSCLC cells, H2170, H358, H1975 and H3255 cells resistant to Osimeritinib. MTT cell viability assays were performed on the parental cell lines and Osimeritinib resistant cell lines (OR) which showed that the H2170OR, H3255OR, H358OR, H1975OR cell lines had IC50 for Osimeritinib, 140, 2.8, 4.6, 10 fold higher in comparison to H2170P, H3255P, H358P, and H1975P cell lines, respectively. We further performed qPCR to study the modulation of EMT biomarkers in Osimeritinib resistant NSCLC cells as compared to parental cells and found that there was upregulation of PRMT1, p120 catenin and Kaiso factor by 1.5 fold to 3.67 fold respectively in H1975 cells and 1 fold to 5.73 fold in H3255 cells. Immunofluorescence studies in H1975OR and H3255OR cells for expression of PRMT1 showed that there was 3.18 fold increase as compared to 2.21 fold increase in Erlotinib resistant H1975 (H1975ER) and 4.77 fold increase in H3255OR as compared to 2.27 fold increase in H3255ER. We further investigated the cancer stem cell (CSC) markers BMI and Oct-4 expression in Erlotinib resistant cells and found an increase in CSC by 1.1 fold and 1.2 fold in H358ER cells. Studies with these CSC markers in Osimeritinib resistant cell lines are being conducted. Furthermore, we corelated the expression of PRMT1 with smoking in NSCLC tumors from Winnebago county area. Our results showed a trend that smokers had higher expression and that 29% of smokers with less than a 30 pack-year history show high expression of PRMT1 compared to 44% in smokers with greater than a 30 pack-year history. In conclusion, biomarkers like PRMT1 may mediate the process of EMT by methylation of transcriptional factors such as Twist1 and upregulation of p120 that prevents transcriptional repression of Kaiso factor target genes, promoting the EMT process in Osimeritinib and Erlotinib resistant cells. Citation Format: Kavya Sri Racherla, Nabiha H. Khan, Sanjana Singh, Neelu Puri. Role of PRMT1 and p120 catenin in mediating EMT and Osimeritinib resistance in NSCLC [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1886.