Abstract 1714: CRACD/KIAA1211 loss drives cell plasticity and immune evasion of small cell lung cancer

Abstract

Abstract Small cell lung carcinoma (SCLC) is a lethal neuroendocrine type of lung cancer with limited therapeutic options. Despite recent advances in cancer immunotherapy, its efficacy is limited to a small subset of SCLC patient tumors. The molecular origin of the refractoriness to immunotherapy remains elusive. CRACD (Capping protein inhibiting regulator of actin dynamics; KIAA1211/CRAD) gene is frequently mutated and transcriptionally downregulated in SCLC. Cracd knockout (KO) causes the transformation of preneoplastic neuroendocrine cells and significantly accelerates SCLC development in a mouse model initiated by the loss of Rb1, Trp53, and Rbl2 in the lung epithelium. Cracd KO induces tumor cell plasticity generating deregulated cell lineage trajectories of SCLC tumors. Strikingly, Cracd KO SCLC tumors display the complete loss of CD8+ T cells due to epigenetic suppression of the MHC-I pathway. Furthermore, single-cell transcriptomic analyses of SCLC patient samples classified SCLC by concurrent features: CRACD inactivation and tumor antigen presentation impairment. This study suggests CRACD as a tumor suppressor of SCLC that regulates proliferation and immune recognition of cells, providing novel insight into the mechanism of SCLC evading immune surveillance. Citation Format: Shengzhe Zhang, Kee-Bum Kim, Yuanjian Huang, Dong-Wook Kim, Bongjun Kim, Kyung-Pil Ko, Gengyi Zou, Jie Zhang, Sohee Jun, Nicole A. Kirk, Ye Eun Hwang, Young Ho Ban, Joseph M. Chan, Charles M. Rudin, Kwon-Sik Park, Jae-Il Park. CRACD/KIAA1211 loss drives cell plasticity and immune evasion of small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1714.