Abstract A030: Fusion between macrophages and cancer cells up-regulates signal regulatory protein pathway and contributes to malignant progression of pancreatic cancer after radiation
Authors: Ch'ang Hui Ju , Tsai Yi-Chih , Li Ting Wei , Liu Rui-Jun , Huang Tze-Sing , Wan Sse-Pei , Chen Su-Liang , Jiang Shih-Sheng 
Published: January 2024

Introduction: Fusion between tumor cells with leukocytes contributes to tumor heterogeneity, resulting in tumorigenesis, metastasis, and treatment resistance. Recent studies demonstrate that an inflammatory microenvironment enhances tumor-macrophage fusion. We hypothesize that tumor-macrophage fusion hybrids contribute to radiation induced pancreatic cancer progression. Materials and Methods: Tumor tissues of female patients receiving previous bone marrow transplantation (BMT) from male donors due to leukemia/lymphoma were collected for Y chromosome and immunofluorescence study. Murine subcutaneous tumor models of cre-loxP or dual fluorescence system were established to demonstrate fusion between Pan02, a murine pancreatic adenocarcinoma cell line, and stromal cells of ROSA (Gt(ROSA)26Sor tm4(ACTB-tdTomato,-EGFP)Luo/Jnarl) mice with or without local radiation exposure. KC (pdx-1-cre-KrasLSL-G12D) mice, were given whole body irradiation followed by BMT from ROSA mice to measure fusion between pancreatic cancer and hematopoietic cells. Liposomal chlodronate, a macrophage depleting agent, and immunofluorescence staining of fusion hybrids in ROSA mice tumors were used to demonstrate macrophage as a fusion partner. Fusion hybrid clones of murine/human pancreatic adenocarcinoma cells with macrophages were selected from co-culture and sorting followed by studies including ploidy, clonogenicity, migration and radio-sensitivity. Affymetrix microarray analysis was used to find differentially expressed genes of fusion hybrids. Results: Fusion phenomenon was demonstrated by showing colocalization of Y chromosomes with epithelial markers in cancer tissues from female patients receiving prior BMT from male donors. Fusion hybrids were found in pancreas tumors of KC mice after BMT from ROSA mice. Fusion hybrids within tumors increased by time, three folds within 6 weeks; and 2.5 folds after 20Gy radiation exposure. Liposomal clodronate reduced fusion hybrids and tumor growth. Immunofluorescence stain of tumor tissues demonstrated CD11b(+) macrophage to be the major fusion partner. Purified Fusion hybrids showed enhanced migration, proliferation, aneuploidy and radio-resistance. Model based gene analysis of microarray study disclosed signal regulatory protein (SIRP) signal pathway was significantly upregulated in fusion hybrids. Upregulated SIRP signal molecules, including DAP12, PyK2, were validated by immunoblots. Silencing DAP12 in myeloid cells from human peripheral blood showed decreased fusion rate with Panc-1 cells. DAP12mRNA depletion in Panc-1 fusion hybrids disclosed enhanced radio-sensitivity. Defactinib (VS6063), a PyK2 inhibitor, reduced fusion phenomenon and suppressed pancreatic tumor growth of mice after local radiation. Conclusions: Fusion between pancreatic cancer cells and macrophages contribute to radiation enhanced malignant progression of pancreatic cancer. SIRP signal pathway is a potential target to disrupt fusion phenomenon and ameliorate pancreatic cancer progression after radiation.

Citation Format: Hui Ju Ch'ang, Yi-Chih Tsai, Ting Wei Li, Rui-Jun Liu, Tze-Sing Huang, Sse-Pei Wan, Su-Liang Chen, Shih-Sheng Jiang. Fusion between macrophages and cancer cells up-regulates signal regulatory protein pathway and contributes to malignant progression of pancreatic cancer after radiation [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A030.