The Roles And Mechanism Of FATS In Immunomodulation Of Melanoma

Background: Melanoma,arises from melanocytes,is an aggressive malignancy with a low survival rate and poor prognosis.Current available therapeutic strategies for melanoma are limited.Therefore,it is important to develop systematic therapeutic strategies and novel therapeutic methods to improve the therapeutic effect of melanoma.Present study shows that immunotherapeutic approaches may bring new breakthough in treatment of human cancers.C10orf90 is a newly identified common fragile sites(CFSs)gene named fragile-site associated tumor suppressor(FATS)according to its tumor suppressive function in FATS overexpressive cancer cell lines.It has been shown that CFSs may be associated with immune regulation.However,studies of FATS gene are limited at present.Especially,in tumor immunology,the function of FATS remains unknown.Our early-stage study suggested that FATS may serve as an important immune regulator.Objective: To explore whether FATS deficiency could regulate the tumor microenvironment,promote immunologic cytotoxicity of tumor,inhibit pro-tumor immunity and finally,suppress the progression of melanima in vivo.To further study the potential cellular and molecular mechanism of FATS in vitro.Methods: In the in vivo study,mice melanoma cell line(B16)was applied for subcutaneous implant in wild type mice and FATS deficiency mice.Tumors were observed and measured daily.Using flow cytometry,real-time PCR and multiple cytokine ELISA assay,histology and immunohistochemistry to evaluate the effect of FATS in peripheral immune organ,serum and tumor microenvironment.In the in vitro study,cell differentiation,mixed cells co-culture,flow cytometry,real-time PCR and western blotting were used to further investigate the potential cellular and molecular mechanisms of FATS in tumor immunology.Finally,adoptive therapy was used to further verify the effect of FATS deficiency on melanoma.Results: In the in vivo study,our results showed that FATS deficiency in mice could significantly inhibit the tumor incidence and growth of melanoma implanted with B16 cells and increase the infiltration of inflammatory cells in tumor tissues.In addition,in peripheral immune organ,especially in tumor microenvironment,FATS-deficient mice present increased numbers and frequency of tumor suppressor cells,including cytotoxic T lymphocyte,NK,??T and M1 macrophage,while inhibited numbers and frequency of tumor promoter cells Treg cell and M2 macrophage.Besides,IL-2,related to T cell proliferation and several important cytokines secreted by M1 macrophage,such as IL-12,were increased in serum of FATS-deficient mice.Furthermore,macrophages separated from FATS-deficient mice possess more powerful ability in tumor cytotoxicity and promoting T cells proliferation than that from wild-type mice.Moreover,compared with wild-type mice,FATS-deficient mice showed lower expression of VEGF in macrophage and suppressed angiogenesis in tumor tissues.In the in vitro study,marrow-derived macrophage from FATS-deficient mice exhibited an intrinsic bias toward M1 polarization and inhibited M2 polarization.Meanwhile,FATS deficiency promoted apotosis in M2 macrophage and activated NF-?B signaling pathway in macrophage,which is important for the polarization of M1 macrophage.Adoptive therapy of FATS-deficienct macrophage significantly inhibited the growth of malenoma.Conclusion: These results demonstrated the inhibitory effect of FATS deficiency on the development and progression of melanoma via regulating tumor immune microenvironment.Through activating NF-?B signaling pathway in macrophage and promoting apoptosis of M2 macrophage,FATS deficiency facilitated the M1 macrophages polarization and reduced M2 macrophages,furthermore,promoted anti-tumor immunity and inhibited angiogenesis in tumor tissues.Therefore,FATS could be a potential immune therapeutic target for malignant tumors.