FOXA1 suppresses cancer immunity independent of DNA binding

Exclusion of lymphocytes from tumors is a major barrier for effective immuno- and chemo-therapy of cancer. We found that FOXA1 overexpression inversely correlates with expression of antigen processing and presentation and interferon signaling genes in different cancer types. FOXA1 binds to STAT proteins and inhibits expression of antigen presentation and interferon response genes and tumor immunity independent of the forkhead domain - DNA binding function. Increased FOXA1 also correlates with immunotherapy resistance in murine triple negative breast tumor and bladder cancer in patients and chemo-resistance in breast cancer patients. Our results reveal that FOXA1 is a key immune suppressor, suggesting that FOXA1 overexpression may predict tumor resistance to immuno- and chemo-therapies and that depletion of FOXA1 may therapeutically convert cancers from ‘immune-cold’ to ‘immune-hot’ diseases. To determine the inhibitory effect of FOXA1 variants on the DNA binding ability of STAT2, cells were expressed of Vetor as control, FOXA1-WT, FOXA1-R261G and FOXA1△αH3, and then the endogenous FOXA1 in LNCaP cells was knocked down by specific siRNA for next STAT2 chromatin immunoprecipitation sequencing (ChIP-seq).

肿瘤淋巴细胞浸润缺失是制约癌症有效免疫治疗与化疗实施的核心障碍。本研究发现，在多种癌症类型中，叉头框蛋白A1（FOXA1）的过表达与抗原加工与呈递相关基因以及干扰素信号通路基因的表达呈负相关。FOXA1可结合信号转导与转录激活因子（STAT）家族蛋白，并可在不依赖叉头结构域DNA结合功能的前提下，抑制抗原呈递、干扰素应答相关基因以及肿瘤免疫相关基因的表达。FOXA1表达上调还与小鼠三阴性乳腺癌模型、患者膀胱癌的免疫治疗耐药性，以及乳腺癌患者的化疗耐药性相关。本研究结果表明，FOXA1是关键的免疫抑制因子，提示FOXA1过表达可作为肿瘤对抗免疫治疗与化疗的耐药性预测标志物，而敲低FOXA1有望将癌症从‘免疫冷肿瘤’转化为‘免疫热肿瘤’，从而实现治疗获益。为探究FOXA1突变体对STAT2 DNA结合能力的抑制作用，本研究设置空载体（Vector）作为对照组，分别转染FOXA1野生型（FOXA1-WT）、FOXA1-R261G突变体以及FOXA1△αH3突变体至细胞中；随后通过特异性小干扰RNA（siRNA）敲低LNCaP细胞中的内源性FOXA1，以开展后续的STAT2染色质免疫共沉淀测序（ChIP-seq）实验。