Divergently evolved FOXA1 mutations drive prostate tumorigenesis or therapy-resistant intra-luminal plasticity [scRNA-Seq]

FOXA1 is recurrently altered in hormone-driven malignancies, with activating hotspot mutations detected in 10-40% of primary prostate cancers based on ethnicity. Yet, the tumorigenic potential and pathobiology of FOXA1 remain unexplored in vivo. Here, we generated and characterized knock-in mouse models harboring FOXA1 mutant transgenes that represent distinct classes of activating mutations. Our findings reveal that FOXA1 class 1 mutations (i.e., wing 2 alterations) in a Trp53-null background, drive high-grade, invasive luminal adenocarcinoma with full penetrance by 40 weeks of age. These hyperproliferative lesions retain luminal characteristics, gain expression of NSD2, and regress upon androgen withdrawal—mirroring features of primary human prostate adenocarcinomas. Mechanistically, class 1 mutants aberrantly activate mTORC1/2 signaling and reprogram androgen receptor (AR) activity by expanding the enhancer landscape at non-canonical chimeric AR-half elements enriched in patient tumors. In contrast, FOXA1 class 2 mutations (i.e., C-terminal truncations) do not drive transformation but induce intra-luminal plasticity in androgen-intact normal tissues, which is otherwise triggered in response to castration. Class 2 mutants lead to a 10- to 20-fold expansion of Ar+/Ck8+ luminal epithelia expressing stem/progenitor markers such as Trop2, Ck4, and Psca. Mechanistically, class 2 mutants maintain AR activity while de-compacting over 40,000 new cis-regulatory elements bound by Klf5 and AP-1 transcription factors to activate stemness and WNT gene programs. Class 2-mutant-expressing prostate epithelial cells resist castration-induced atrophy, remain proliferative in androgen-deprived conditions, and form organoids and allografts at higher frequencies. Additionally, metastatic prostate tumors from patients harboring class 2 mutations show elevated KLF5 expression and stemness signatures. Collectively, our data establish FOXA1 as a critical oncogene in both primary and advanced AR-dependent prostate cancers, revealing its functional versatility in driving either tumor initiation or therapy resistance depending on the mutation class. Comparative RNA profiles of the anterior and dorsal lobes of the mouse prostate tissues upon overexpression of the FOXA1 R265-71del mutation in conjunction with Trp53 loss. These tissues were obtained from 100 week-old male mice.

叉头框蛋白A1（FOXA1）在激素驱动型恶性肿瘤中频发发生遗传学改变，基于种族背景，10%~40%的原发性前列腺癌中可检测到其激活性热点突变。然而，FOXA1的致瘤潜能及其病理生物学特性尚未在体内得到研究。本研究构建并表征了携带代表不同类别激活性突变的FOXA1突变转基因的基因敲入小鼠模型。研究结果显示，在Trp53缺失（Trp53-null）背景下，FOXA1 1类突变（即翼区2变异）可在40周龄时完全外显，诱发高级别浸润性腔面型腺癌。此类过度增殖病灶保留腔面表型，上调核受体结合SET结构域蛋白2（NSD2）的表达，并在雄激素剥夺后发生消退，这与原发性人前列腺腺癌的特征一致。机制上，1类突变体异常激活雷帕霉素靶蛋白复合物1/2（mTORC1/2）信号通路，并通过扩增患者肿瘤中富集的非经典嵌合雄激素受体（AR）半位点的增强子图谱，重编程AR的活性。与之相反，FOXA1 2类突变（即C端截短突变）并不诱发细胞转化，但可在雄激素完整的正常组织中诱导腔内可塑性——这一表型通常仅在去势刺激下才会触发。2类突变体可使表达滋养层细胞表面抗原2（Trop2）、细胞角蛋白4（Ck4）及前列腺干细胞抗原（Psca）等干/祖细胞标志物的Ar阳性/Ck8阳性腔上皮细胞扩增10~20倍。机制上，2类突变体在维持AR活性的同时，对超过40000个被Klf5和AP-1转录因子结合的新顺式调控元件进行去致密化，从而激活干性及WNT基因程序。表达2类突变体的前列腺上皮细胞可抵抗去势诱导的萎缩，在雄激素剥夺条件下仍保持增殖能力，并能以更高效率形成类器官及同种异体移植瘤。此外，携带2类突变的患者转移性前列腺肿瘤中，KLF5表达升高且干性特征显著。综上，本研究数据证实FOXA1是原发性及晚期AR依赖性前列腺癌的关键致癌基因，并揭示其根据突变类型不同，可通过驱动肿瘤起始或治疗抵抗发挥功能多样性。本数据集包含联合Trp53缺失、过表达FOXA1 R265-71del突变的小鼠前列腺前叶与背叶组织的比较转录组谱，所有组织均取自100周龄雄性小鼠。