Sep 30

QP 18 - Radiation and Cancer Biology 5: Cellular Radiation Effects & DNA Damage Response

1107 - Irradiated Tumor Cell-Derived Extracellular Vesicles Foster Immunosuppressive Macrophages Formation to Promote Esophageal Squamous Cell Carcinoma Progression

05:44pm - 05:50pm PT

Room 307/308

Presenter(s)

Xi Yang, MD, PhD - Fudan University Shanghai Cancer Center, Shanghai, Shanghai

S. Jiang¹, X. Yang², and Z. Zhu²; ¹Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China, Shanghai, China, ²Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China

Purpose/Objective(s):

Radiotherapy can reshape the tumoral microenvironment towards an immunosuppressive microenvironment. The precise modulation of the tumor immunosuppressive microenvironment has emerged as a promising approach for therapeutic intervention. However, the underlying mechanisms of the immunosuppressive microenvironment induced by radiotherapy in esophageal squamous cell carcinoma (ESCC) remains unclear.

Materials/Methods:

Tumor models were established with a dose of 15Gy/1 fraction irradiation. The expression of PD-L1⁺macrophages and CD8⁺T cells was tested by flow cytometry assay. RNA-sequencing analysis was used to identify RNAs in EVs derived from irradiated and non-irradiated ESCC cells. RNA pulldown, mass spectrum and RNA binding protein immunoprecipitation assay were used to identified DYNLL1-AS1 binding protein. Dual-Luciferase Reporter Assay was performed to measure the luciferase activity of PD-L1 in the macrophages. DYNLL1-AS1, CD68, PD-L1 and CD8 expression in ESCC tissue samples of patients were detected by ISH and IHC.

Results:

Irradiated ESCC cells upregulated PD-L1in macrophages in vivo and in vitro. Mechanistic investigations reveal that irradiated EVs (IR-EVs) derived from ESCC cells increased PD-L1⁺macrophage abundance and decreased T cell activity. RNA-sequencing analysis revealed that DYNLL1-AS1 was increased in IR-EVs and identified as key signaling molecules mediating the macrophages’ PD-L1 expression. Further analysis revealed that DYNLL1-AS1 targeting SEC22B to promote the nuclear translocation of FOXP1, which induces PD-L1 expression of macrophages. In addition, DYNLL1-AS1 expression was positive correlated with high PD-L1⁺TAMs infiltration in tumor tissues, and also predicts poorer tumor regression grade of ESCC patients with neoadjuvant immunotherapy. Finally, higher DYNLL1-AS1 expression in the tumor tissues of ESCC patients was corelated with poorer prognosis.

Conclusion:

IR-EVs-DYNLL1-AS1 targeting SEC22B to promote the nuclear translocation of FOXP1, which upregulates PD-L1 expression of macrophages to foster immune suppression. EVs-DYNLL1-AS1 may be a potential predictive biomarker for prognosis and a therapeutic strategy against immune tolerance of ESCC.