Relaxin 2 Suppresses Tumor Growth in Esophageal Squamous Cell Carcinoma EC9706 Cells Through Modulation of the STAT Signaling Pathway

ABSTRACT Esophageal carcinoma is a highly aggressive cancer with limited therapeutic options. Relaxin 2 (RLN2) has been identified as a regulator of various physiological processes, but its role in cancer, particularly in esophageal carcinoma, is less understood. This study investigates the anticancer effects of RLN2 in EC9706 esophageal carcinoma cells and explores its involvement in the STAT signaling pathway. The study utilized various assays, including CCK‐8 for cell viability, DAPI staining and annexin V‐FITC for apoptosis assessment, transwell chambers for cell migration and invasion, tube formation assay for angiogenesis, and western blot analysis for analyzing apoptosis‐related and STAT signaling proteins. Additionally, the in vivo anticancer potential of RLN2 was assessed using a mouse model. RLN2 demonstrated significant cytotoxicity against esophageal EC9706 cancer cells, inhibiting cell proliferation in a dose‐ and time‐dependent manner. Apoptosis was markedly increased with higher doses of RLN2, as evidenced by an increase in both early and late apoptotic cells. Proapoptotic proteins (Bad, Bax, Caspase‐3, Caspase‐9) were upregulated, while antiapoptotic proteins (Bcl‐2, Mcl‐1, Bcl‐xL) were downregulated in response to RLN2 treatment. RLN2 significantly inhibited cell migration, invasion, and angiogenesis in EC9706 cells. Furthermore, RLN2 increased the phosphorylation of STAT‐1, while the phosphorylation of STAT‐3 was reduced. In the in vivo model, RLN2 effectively suppressed tumor growth. RLN2 exhibits potent anticancer effects against EC9706 cells and in a mouse model, primarily through inducing intrinsic apoptosis, inhibiting cell migration and invasion, and blocking the STAT signaling pathway. These findings highlight RLN2's potential as a therapeutic agent for esophageal carcinoma.