Abstract 3348: Identification of circSPINT2 as a tumor suppressive circular RNA sensitizing lung cancer to 3rd generation EGFR-TKI treatment
Authors: Wang Mong-Lien (Lotus) , Shiou Shih-Hwa , Chen Yi-Chen , Tsai Ming-Long , Verusingam Nalini Devi , Ong Alan Han-Kiat 
Published: March 2024

Abstract
Introduction: Lung cancer remains a high incidence and mortality globally. Adenocarcinoma is the most common type of lung cancer with around 50% of patients in Asia expressing mutated EGFR, which makes EGFR an effective therapeutic target to treat lung adenocarcinoma (LAC). Unfortunately, resistance to EGFR-TKI often occurs in patients through either dynamic EGFR mutation, driver oncogenic pathway shift, or transdifferentiating to evade EGFR-TKI treatment. circRNAs are a type of RNA molecule with a circular shape. Their importance in several biological processes and disease progression was intensively studied recently, and have emerged as promising diagnostic, prognostic, and monitoring biomarkers for diseases like cancer. CircRNAs’ unique circular structure and resistance to degradation make them robust candidates for non-invasive diagnostics of cancers.
Aims: This study aimed to identify and investigate the involvement of a novel circular RNA (circSPINT2) in acquired resistance against the 3rd generation EGFR-TKI Osimertinib.
Materials & Methods: Comparative circRNA sequencing (circRNA-Seq), qRT-PCR, sanger sequencing, and RNase R treatment were applied to identify and verify the identity of Osimertinib-resistance-related circRNA. Biotinylated circRNA pull-down assay, miRNA-seq, and in-silico analysis were employed to delineate the downstream miRNA-mRNA regulatory axis. Osimertinib-resistant mouse xenograft model was established to explore the molecular mechanisms associated with both circSPINT2 and Osimertinib resistance.
Results: We identified circSPINT2 as particularly downregulated in Osimertinib-resistant cell lines (OR) using circRNA-Seq. Overexpression of circSPINT2 in resistant cells increased cellular sensitivity to Osimertinib, whereas knockdown of circSPINT2 conferred Osimertinib resistance in parental cells. The circSPINT2-dependent regulation of Osimertinib sensitivity is mediated through modulating apoptosis. In-vitro analysis indicated high circSPINT2 increased tumor suppressor RBP1 expression by sequestering oncogenic hsa-miR-1296 further improving Osimertinib sensitivity. Molecular and histologic analysis of subcutaneous xenograft tumors corroborated our in-vitro results.
Conclusion: Our study demonstrated circSPINT2 functions as a tumor suppressor, improving Osimertinib sensitivity via the hsa-miR-1296/RBP1 axis. circSPINT2 may serve as a prognostic and cancer biomarker to monitor Osimertinib resistance in LAC patients.
Citation Format: Mong-Lien (Lotus) Wang, Shih-Hwa Shiou, Yi-Chen Chen, Ming-Long Tsai, Nalini Devi Verusingam, Alan Han-Kiat Ong. Identification of circSPINT2 as a tumor suppressive circular RNA sensitizing lung cancer to 3rd generation EGFR-TKI treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3348.