Catalpol Reactivates IL-7R–STAT5 Signaling and Reverses Radiation-Induced T Helper 1 Cells Deficiency to Limit Melanoma Metastasis to Lung

BACKGROUND: Radiation-induced quantitative deficiency of T helper 1 (Th1) cells accelerates lung tumor development. Here, we evaluated IL-7R-STAT5 signaling in Th1 recovery after irradiation and examined how catalpol contributes to Th1 reconstitution by targeting this signaling axis in mice. METHODS: ) cells, were analyzed in local radiotherapy (LRT) mice challenged with lung melanoma and single low-dose total body irradiation (SLTBI) mice without tumor. IL-7R-STAT5 signaling of Th1 from LRT mice, treated with or without catalpol, was evaluated using flow cytometry and RT-qPCR. The role of IL-7-IL-7R-STAT5 signaling in irradiated Th1 cells was further confirmed in irradiated EL4 cells following administration of IL-7 or catalpol. RESULTS: cells, and irradiated Th1 cells exhibited decreased activation of IL-7R-STAT5 signaling. Quantitative reduction of Th1 cells increased lung metastasis of B16 melanoma in irradiated mice. Irradiated EL4 cells also displayed decreased IL-7R-STAT5 signaling and reduced IFN-γ production in vitro. Treatment with catalpol could restore IL-7R-STAT5 signaling and promote Th1 recovery following irradiation both in vivo and in vitro. Catalpol-mediated restoration of IL-7R-STAT5 signaling in Th1 provided superior protection against B16 melanoma metastasis to the lung. CONCLUSIONS: IL-7R-STAT5 signaling is required for Th1 recovery after irradiation. Catalpol effectively promotes Th1 cell reconstitution and decreases B16 melanoma metastasis to the lung by enhancing IL-7R-STAT5 signaling. These findings provide new strategies for improving radiotherapy and immunotherapy outcomes in cancer.