Cucurbitacin B Controls M2 Macrophage Polarization to Suppresses Metastasis via Targeting JAK-2/STAT3 Signalling Pathway

Abstract Background Colorectal cancer is one of the most high-risk human malignant tumors. Tumor-associated macrophages (TAMs) represent a substantial proportion of all tumor-infiltrating immune cells in the tumor microenvironment (TME), as it generally displays M1 or M2 phenotype with tumor-inhibiting or tumor-promoting activity. Cucurbitacin B has been reported to produce varieties of pharmacological effects for the treatment of cancer. Methods Cell viability and proliferation were measured by CCK8 as well as colony formation assays, and cell apoptosis were analyzed by flow cytometry. The underlying mechanism was determined using western blot, microscale thermophores and immunofluorescence assays. In addition, the supernatant of cucurbitacin B-induced M2-like macrophages and colon cells were co-cultured in vitro, transwell and wound healing assay were employed to the related phenotypes. Two mouse model were established to investigate the anti-apoptosis and anti-metastasis of cucurbitacin B. Results Herein, our study was performed to evaluate the anti-tumor and anti-metastasis effect of cucurbitacin B. It was observed that cucurbitacin B inhibited the phosphorylation of JAK2 and STAT3, and translocation from the cytosol to the nucleus. Meanwhile, we observed that cucurbitacin B bound to STAT3. Further experimentation demonstrated that cucurbitacin B reduced the polarization of M2 macrophage by down-regulating JAK2/STAT3 signaling pathway. Cucurbitacin B-induced M2-like macrophages was found to diminish the migration of CRC cells. In vitro study suggested that cucurbitacin inhibited the CRC cells proliferation via JAK2/STAT3 and suppressed the cell migration by suppressing M2-like macrophages polarization. Consistent with in vitro results, the cucurbitacin B therapy significantly inhibited tumor growth and metastasis in mice. Moreover, in vivo the treatment with cucurbitacin B enhanced anti-tumor immunity by regulating M2-like macrophages and promoted the expression of CD4 and CD8 in tumor microenvironment. Conclusion Collectively, our results provided that cucurbitacin B might be a potential candidate agent for adjuvant therapy in the process of CRC growth and metastasis.