2929 - CXCL3 Signaling and the Tumor-Promoting Activity of Cancer-Associated Fibroblasts in Esophageal Squamous Cell Carcinoma

H. Zhang¹, J. Yue², L. Qiu³, L. Ding², H. Jiang⁴, K. Zhang⁵, L. Zhu³, and R. Zhou³; ¹Affiliated Hangzhou Cancer Hospital, Zhejiang University School of Medicine; Key Laboratory of Clinical Cancer Pharmacology and Toxicology Research of Zhejiang Province, Affiliated Hangzhou First Peoples Hospital, Zhejiang University School of Medicine, Hangzhou, China, ²Hangzhou Cancer Hospital, Hangzhou, China, ³Hangzhou Cancer Hospital, hangzhou, Zhejiang, China, ⁴Department of Radiation Oncology, Affiliated Hangzhou First Peoples Hospital, Westlake University School of Medicine, Hangzhou, Zhejiang, China, ⁵Department of Radiation Oncology, Hangzhou Cancer Hospital, Hangzhou, China

Purpose/Objective(s): Cancer-associated fibroblasts (CAFs), as one major component of tumor microenvironment (TME), are closely associated with tumor initiation and progression. Our previous studies have discovered that CAFs induced the resistance of esophageal squamous cell carcinoma (ESCC) cells to a variety of chemotherapeutic drugs such as cisplatin and paclitaxel. Furthermore, CAFs attenuated ionizing irradiation (IR)-induced cancer cells death by regulating DNA damage response. However, CAFs are significantly heterogeneous and different subtypes have different functions. Even some CAFs subtypes display anti-tumor activity. Our study aimed to discover the heterogeneity among ESCC CAFs and screened the subtype of CAFs which have significant pro-tumor activity. Materials/

Methods: By single-cell RNA-sequencing (scRNA-seq), we analyzed the heterogeneity among ESCC CAFs which had been isolated from primary ESCC patients who did not receive any therapy before surgery. Using transwell assay, we detected the invasion ability of CAFs subtypes as well as ESCC cells. By immunofluorescence analysis, we analyzed the radiosensitivity of CAFs subtypes by detecting the expression of ?-H2AX, a marker of DNA double-stranded breaks (DSBs) following irradiation. We further detected the cells survival after irradiation using flow cytometry (FCM).
Results: By scRNA-seq, we found several subtypes existed among ESCC CAFs. Especially, the CAFs subtype with high expression of CXCL3 (CXCL3^high CAFs) showed significant pro-tumor activity. CXCL3^high CAFs significantly promoted the invasion ability and radioresistance of ESCC cells compared with CXCL3^low CAFs. When CAFs were transfected with CXCL3 siRNA, their tumor-promoting activity was significantly reversed. Furthermore, down-regulation of CXCL3 expression in CAFs attenuated their invasion ability and enhanced their radiosensitivity. The co-culture of CAFs and ESCC cells induced the activation of autocrine/paracrine CXCL3 signaling.
Conclusion: CXCL3 signaling regulates the malignant behaviors of ESCC CAFs. Targeting CXCL3^high CAFs may be a promising approach of treating ESCC.