Ji Likeng, Chen Jiongyu, He Lifang, Zhang Fan, Deng Zihao, Lin Jiediao, Qi Zhaochang, Luo Xi, Giuliano Armando E, Cui Xiaojiang, Lin Stanley Li, Cui Yukun
Shantou Key Laboratory of Precision Diagnosis and Treatment in Women's Cancer, Cancer Hospital of Shantou University Medical College, Shantou, Guangdong, China.
Department of Surgery, Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA.
Oncogene. 2025 Mar;44(8):530-544. doi: 10.1038/s41388-024-03238-3. Epub 2024 Dec 2.
Approximately 70% of breast cancer (BC) cases are luminal-type (estrogen receptor-positive, ER+), suitable for endocrine therapy with tamoxifen as the most commonly used drug. However, about 30% of these patients develop tamoxifen resistance due to various mechanisms, primarily involving PI3K pathway activation through mutations or unknown pathways. Here, we discover, via bioinformatics analysis and clinical samples, that N6 adenine-specific DNA methyltransferase 1 (N6AMT1) is highly expressed in luminal breast cancer but downregulated in tamoxifen-resistant (TamR) BC cells. ChIP-qPCR and luciferase reporter assays showed that FOXA1 binds to the N6AMT1 promoter and enhances its transcription. In TamR models, FOXA1 and N6AMT1 are downregulated, increasing p110α protein levels (but not mRNA), phospho-AKT levels, and tamoxifen resistance. In vivo, N6AMT1 overexpression enhanced tamoxifen sensitivity, while knockdown reduced it; this sensitivity could be restored with the p110α inhibitor A66. Clinically, decreased N6AMT1 expression correlates with poor prognosis in luminal BC patients. In TamR BC organoids, combining tamoxifen with A66 further reduced growth compared to either treatment alone. Mechanistically, increased p110α levels result from inhibited degradation by E3 ubiquitin ligase NEDD4L. These findings suggest N6AMT1 as a potential luminal breast cancer biomarker and highlight the N6AMT1-p110α pathway as a therapeutic target to sensitize cells to tamoxifen.
大约70%的乳腺癌（BC）病例为管腔型（雌激素受体阳性，ER+），适合以内分泌治疗为主，他莫昔芬是最常用的药物。然而，这些患者中约有30%会因各种机制产生他莫昔芬耐药性，主要涉及通过突变激活PI3K途径或未知途径。在这里，我们通过生物信息学分析和临床样本发现，N6腺嘌呤特异性DNA甲基转移酶1（N6AMT1）在管腔型乳腺癌中高表达，但在他莫昔芬耐药（TamR）的BC细胞中下调。染色质免疫沉淀定量聚合酶链反应（ChIP-qPCR）和荧光素酶报告基因检测表明，叉头框蛋白A1（FOXA1）与N6AMT1启动子结合并增强其转录。在TamR模型中，FOXA1和N6AMT1下调，导致p110α蛋白水平（而非mRNA）、磷酸化AKT水平升高以及他莫昔芬耐药。在体内，N6AMT1过表达增强了他莫昔芬敏感性，而敲低则降低了敏感性；使用p110α抑制剂A66可恢复这种敏感性。临床上，N6AMT1表达降低与管腔型BC患者的不良预后相关。在TamR BC类器官中，与单独使用任一治疗相比，他莫昔芬与A66联合使用可进一步降低生长。从机制上讲，p110α水平升高是由于E3泛素连接酶NEDD4L介导的降解受到抑制。这些发现表明N6AMT1是一种潜在的管腔型乳腺癌生物标志物，并突出了N6AMT1-p110α途径作为使细胞对他莫昔芬敏感的治疗靶点。
