Data Sheet 1_A novel prognostic signature identifies MFAP4 as a tumor suppressor linking the tumor microenvironment to PI3K/AKT signaling in triple-negative breast cancer.pdf

BackgroundTriple-negative breast cancer (TNBC) remains a clinical challenge due to its aggressiveness and limited therapeutic options. The tumor microenvironment (TME), particularly the extracellular matrix (ECM), is a critical regulator of TNBC progression, yet the key molecular drivers remain largely elusive. This study aimed to identify novel TME-related prognostic biomarkers and elucidate their functional roles in TNBC.
MethodWe constructed and validated a multi-gene prognostic model using TNBC datasets from Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases. The model’s association with TME characteristics was assessed using ESTIMATE algorithm and immune infiltration analyses. The biological functions of the key gene, Microfibril Associated Protein 4 (MFAP4), were investigated in vitro via proliferation and migration assays. The underlying mechanism was explored through Western blotting and validated by a functional rescue experiment using a PI3K/AKT/mTOR pathway agonist.
ResultsWe established a robust 11-gene prognostic model that effectively stratified TNBC patients into high- and low-risk groups with distinct overall and metastasis-free survival. The low-risk group was characterized by an immune-active microenvironment. Notably, MFAP4, an ECM-related gene within the signature, was identified as a key tumor suppressor. MFAP4 expression was significantly downregulated in TNBC tissues and correlated with worse prognosis. Overexpression of MFAP4 markedly suppressed TNBC cell proliferation and migration. Mechanistically, MFAP4 inhibited the phosphorylation of key components of the PI3K/AKT/mTOR pathway. Crucially, pharmacological activation of this pathway with MHY1485 partially rescued the anti-tumor effects induced by MFAP4.
ConclusionOur study established a TME-centric prognostic signature and, more importantly, identified MFAP4 as a novel tumor suppressor in TNBC. We provide the first evidence that MFAP4 inhibits TNBC malignancy by restraining the PI3K/AKT/mTOR signaling pathway, thereby establishing a critical link between the ECM and intracellular oncogenic signaling. MFAP4 represents a promising prognostic biomarker and a potential therapeutic target for TNBC.

背景 三阴性乳腺癌（Triple-negative breast cancer, TNBC）因其高侵袭性与有限的治疗选择，仍是临床亟待解决的难题。肿瘤微环境（tumor microenvironment, TME），尤其是细胞外基质（extracellular matrix, ECM），是调控TNBC进展的关键调节因素，但其核心分子驱动机制仍尚不明确。本研究旨在筛选新型TME相关预后生物标志物，并阐明其在TNBC中的功能作用。
方法 本研究利用来自基因表达综合数据库（Gene Expression Omnibus, GEO）与癌症基因组图谱（The Cancer Genome Atlas, TCGA）的TNBC数据集，构建并验证了多基因预后模型。采用ESTIMATE算法与免疫浸润分析评估该模型与TME特征的关联。针对核心基因微丝相关蛋白4（Microfibril Associated Protein 4, MFAP4），通过体外增殖与迁移实验探究其生物学功能。通过蛋白质印迹（Western blotting）探索其潜在作用机制，并利用PI3K/AKT/mTOR通路激动剂开展功能挽救实验予以验证。
结果 本研究构建了稳健的11基因预后模型，可有效将TNBC患者分为高风险组与低风险组，两组患者的总生存期与无转移生存期存在显著差异。低风险组以免疫激活型微环境为特征。值得注意的是，该特征基因集内的ECM相关基因MFAP4被鉴定为关键肿瘤抑制因子。MFAP4在TNBC组织中表达显著下调，且与不良预后相关。MFAP4过表达可显著抑制TNBC细胞的增殖与迁移。机制上，MFAP4可抑制PI3K/AKT/mTOR通路关键组分的磷酸化。至关重要的是，使用MHY1485对该通路进行药理学激活，可部分挽救MFAP4诱导的抗肿瘤效应。
结论 本研究构建了以TME为核心的预后特征基因集，更为重要的是，鉴定出MFAP4为TNBC中的新型肿瘤抑制因子。本研究首次证实，MFAP4通过抑制PI3K/AKT/mTOR信号通路以遏制TNBC恶性表型，从而建立了ECM与细胞内致癌信号通路之间的关键关联。MFAP4有望成为TNBC极具前景的预后生物标志物与潜在治疗靶点。