Abstract
Abstract Osimeritinib (OR), a Tyrosine Kinase Inhibitor is a first-line therapy in EGFR-mutant NSCLC patients. Resistance to OR 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 localization of p120 catenin, an E-cadherin regulating protein, and Kaiso factor, a repressor of Wnt signaling, promoting oncogenesis. Protein arginine methyl transferase 1 (PRMT1) an EMT regulator catalyzes methylation of Twist1, which represses E-cadherin. However, their role in OR resistance is still unknown. We have made parental (P) NSCLC cells, H2170, H358, H1975 and H3255 resistant to OR. MTT assays were performed on the parental cells and OR resistant cells which showed that the H2170OR, H3255OR, H358OR, H1975OR cells had IC50 for OR, 2.8-14 fold higher in comparison to parental cells, respectively. We further performed qPCR to study the modulation of EMT biomarkers in OR cells as compared to parental cells and found upregulation of PRMT1, p120 catenin and Kaiso factor by 1.5-3.67 fold respectively in H1975 cells and 1.5-5.73 fold in H3255 cells. Immunofluorescence studies in H1975OR 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. After transfection with p120 siRNA we found that OR efficacy was increased by 33% in comparison to mock siRNA and OR treated cells. The percentage wound closure after 24 hours was found to be 26.2% in the p120-catenin siRNA transfected cells as compared to 7.4%.in mock siRNA transfected cells (p<0.05) indicating its role in EMT and cell migration. Furthermore, our results showed increased expression of p120 catenin in smokers with 50% of smokers showing high expression compared to 0% and 5.8% of quit smokers and nonsmokers indicating that high p-120 expression was associated with smoking (P=0.002). In conclusion, biomarkers like PRMT1 may mediate the process of EMT by methylation of Twist1 and upregulation of p120 that prevents transcriptional repression of Kaiso factor target genes, promoting EMT in OR and ER resistant cells. p-120 expression was found to be higher in smokers compared to quit/nonsmokers indicating that it may have a potential role in lung cancer. Citation Format: Kavya Sri Racherla, Katrina Dovalovsky, Neelu Puri. Role of emt biomarkers in mediating osimertinib resistance in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1431.
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