DataSheet_1_IGF2BP family of RNA-binding proteins regulate innate and adaptive immune responses in cancer cells and tumor microenvironment.pdf

Insulin-like growth factor 2 mRNA-binding proteins (IGF2BP1, IGF2BP2, and IGF2BP3) are a family of RNA-binding proteins that play an essential role in the development and disease by regulating mRNA stability and translation of critical regulators of cell division and metabolism. Genetic and chemical inhibition of these proteins slows down cancer cell proliferation, decreases invasiveness, and prolongs life span in a variety of animal models. The role of RNA-binding proteins in the induction of tissues’ immunogenicity is increasingly recognized, but, the impact of the IGF2BPs family of proteins on the induction of innate and adaptive immune responses in cancer is not fully understood. Here we report that downregulation of IGF2BP1, 2, and 3 expression facilitates the expression of interferon beta-stimulated genes. IGF2BP1 has a greater effect on interferon beta and gamma signaling compared to IGF2BP2 and IGF2BP3 paralogs. We demonstrate that knockdown or knockout of IGF2BP1, 2, and 3 significantly potentiates inhibition of cell growth induced by IFNβ and IFNγ. Mouse melanoma cells with Igf2bp knockouts demonstrate increased expression of MHC I (H-2) and induce intracellular Ifn-γ expression in syngeneic T-lymphocytes in vitro. Increased immunogenicity, associated with Igf2bp1 inhibition, “inflames” mouse melanoma tumors microenvironment in SM1/C57BL/6 and SW1/C3H mouse models measured by a two-fold increase of NK cells and tumor-associated myeloid cells. Finally, we demonstrate that the efficiency of anti-PD1 immunotherapy in the mouse melanoma model is significantly more efficient in tumors that lack Igf2bp1 expression. Our retrospective data analysis of immunotherapies in human melanoma patients indicates that high levels of IGF2BP1 and IGF2BP3 are associated with resistance to immunotherapies and poor prognosis. In summary, our study provides evidence of the role of IGF2BP proteins in regulating tumor immunogenicity and establishes those RBPs as immunotherapeutic targets in cancer.

胰岛素样生长因子2 mRNA结合蛋白家族（insulin-like growth factor 2 mRNA-binding proteins，IGF2BP1、IGF2BP2、IGF2BP3）是一类RNA结合蛋白（RNA-binding proteins），通过调控细胞分裂与代谢关键调控因子的mRNA稳定性及翻译过程，在个体发育与疾病进程中发挥不可或缺的核心作用。对该家族蛋白进行遗传与化学抑制，可在多种动物模型中减缓癌细胞增殖、降低其侵袭能力，并延长模型动物的生存期。学界对RNA结合蛋白诱导组织免疫原性的作用已日益重视，但IGF2BP家族蛋白对癌症中先天与适应性免疫应答的调控效应尚未完全阐明。本研究发现，下调IGF2BP1、2、3的表达可促进干扰素β（interferon beta，IFNβ）刺激基因的表达。与IGF2BP2和IGF2BP3旁系同源亚型相比，IGF2BP1对干扰素β与干扰素γ（interferon gamma，IFNγ）信号通路的调控作用更为显著。实验结果显示，敲低或敲除IGF2BP1、2、3可显著增强IFNβ与IFNγ介导的细胞生长抑制效应。体外实验中，Igf2bp基因敲除的小鼠黑色素瘤细胞可上调MHC I（主要组织相容性复合体I类分子，Major Histocompatibility Complex class I，H-2）的表达，并诱导同基因T淋巴细胞内Ifn-γ的表达。在SM1/C57BL/6与SW1/C3H小鼠模型中，Igf2bp1抑制所介导的免疫原性增强可使小鼠黑色素瘤的肿瘤微环境发生炎性活化，具体表现为自然杀伤细胞（natural killer cells，NK细胞）与肿瘤相关髓系细胞的数量较对照组提升一倍。进一步研究表明，在小鼠黑色素瘤模型中，Igf2bp1缺失的肿瘤对抗程序性死亡受体1（programmed cell death protein 1，PD-1）免疫治疗的响应效率显著提升。对人类黑色素瘤患者免疫治疗的回顾性数据分析显示，IGF2BP1与IGF2BP3的高表达与免疫治疗耐药性及不良预后密切相关。综上，本研究证实了IGF2BP家族蛋白在调控肿瘤免疫原性中的作用，并确立了此类RNA结合蛋白作为癌症免疫治疗靶点的潜在价值。