Abstract 1601: CD47 related to intratumor heterogeneity in alectinib-resistant ALK-rearranged lung cancer cell lines

Overcoming the treatment resistance of cancer is a problem to be solved in improving the prognosis of cancer patients. Recently, genome analysis has revealed that multiple clusters exist in one tumor, and it has been reported that intratumor heterogeneity causes treatment resistance even in lung cancer. However, the mechanism of intratumor heterogeneity has not yet been clarified. Previous studies of intratumor heterogeneity have mainly focused on analyzing cancer cells from patients, classifying clusters of different properties, and identifying factors that define their characteristics. Multiple clusters are present in the tumor tissue of a single patient, and analysis of multiple patients classifies them into even more clusters, but it is difficult to research all of them. To solve this problem, an early model of intratumor heterogeneity in which homogeneous cells become heterogeneous is needed.We hypothesized that intratumor heterogeneity cell model could be found in resistant strains.Alectinib was exposed in vitro to an ALK-positive lung cancer cell line (H2228) to create an alectinib-resistant cell line (H2228-AR1S). H2228-AR1S has two subpopulations that look different. Of the two subpopulations, the smaller cells have high CD47 expression (CD47 high subpopulation), and the scattered spindle-shaped cells have low CD47 expression (CD47 low subpopulation). Using flow cytometry, each subpopulation was isolated, and its properties were investigated. There was no difference in sensitivity to alectinib between the CD47 high subpopulation and the CD47 low subpopulation. In the low subpopulation of CD47, epithelial markers were decreased, and mesenchymal markers were increased using immunoblotting. It suggests that CD47 low subpopulation has undergone epithelial-mesenchymal transition (EMT). The CD47 high subpopulation had high sphere formation ability in vitro, and high tumorigenicity using Xenograft model. CD47 gene inhibition using siRNA reduced the sphere formation ability of the CD47 high subpopulation. This suggests that CD47 is involved in sphere formation.There have been no reports of CD47 being involved in the characteristics of intratumor heterogeneity. Furthermore, using intratumor heterogeneity cell model, we are exploring the mechanism that regulate division into two subpopulations. Citation Format: Tomoko Y. Funazo, Hiroaki Ozasa, Kentaro Hashimoto, Hiroshi Yoshida, Tatsuya Ogimoto, Kazutaka Hosoya, Hitomi Ajimizu, Takahiro Tsuji, Hironori Yoshida, Ryo Itotani, Yuichi Sakamori, Toyohiro Hirai. CD47 related to intratumor heterogeneity in alectinib-resistant ALK-rearranged lung cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1601.