Department of Molecular Biology, Genentech Inc, 1 DNA Way, South San Francisco, CA, 94080, USA.
Department of Bioinformatics and Computational Biology, Genentech Inc, 1 DNA Way, South San Francisco, CA, 94080, USA.
Breast Cancer Res. 2019 Dec 27;21(1):152. doi: 10.1186/s13058-019-1238-5.
PIK3CA mutations are frequent in human breast cancer. Pik3caH1047R mutant expression in mouse mammary gland promotes tumorigenesis. TP53 mutations co-occur with PIK3CA mutations in human breast cancers. We previously generated a conditionally activatable Pik3caH1047R;MMTV-Cre mouse model and found a few malignant sarcomatoid (spindle cell) carcinomas that had acquired spontaneous dominant-negative Trp53 mutations.
A Pik3caH1047R;Trp53R270H;MMTV-Cre double mutant mouse breast cancer model was generated. Tumors were characterized by histology, marker analysis, transcriptional profiling, single-cell RNA-seq, and bioinformatics. Cell lines were developed from mutant tumors and used to identify and confirm genes involved in metastasis.
We found Pik3caH1047R and Trp53R270H cooperate in driving oncogenesis in mammary glands leading to a shorter latency than either alone. Double mutant mice develop multiple histologically distinct mammary tumors, including adenocarcinoma and sarcomatoid (spindle cell) carcinoma. We found some tumors to be invasive and a few metastasized to the lung and/or the lymph node. Single-cell RNA-seq analysis of the tumors identified epithelial, stromal, myeloid, and T cell groups. Expression analysis of the metastatic tumors identified S100a4 as a top candidate gene associated with metastasis. Metastatic tumors contained a much higher percentage of epithelial-mesenchymal transition (EMT)-signature positive and S100a4-expressing cells. CRISPR/CAS9-mediated knockout of S100a4 in a metastatic tumor-derived cell line disrupted its metastatic potential indicating a role for S100a4 in metastasis.
Pik3caH1047R;Trp53R270H;MMTV-Cre mouse provides a preclinical model to mimic a subtype of human breast cancers that carry both PIK3CA and TP53 mutations. It also allows for understanding the cooperation between the two mutant genes in tumorigenesis. Our model also provides a system to study metastasis and develop therapeutic strategies for PIK3CA/TP53 double-positive cancers. S100a4 found involved in metastasis in this model can be a potential diagnostic and therapeutic target.
PIK3CA 突变在人类乳腺癌中很常见。Pik3caH1047R 突变在小鼠乳腺中的表达促进了肿瘤的发生。TP53 突变与人类乳腺癌中的 PIK3CA 突变共同发生。我们之前生成了一种条件激活的 Pik3caH1047R；MMTV-Cre 小鼠模型，发现少数恶性肉瘤样（梭形细胞）癌获得了自发的显性负 Trp53 突变。
生成了 Pik3caH1047R；Trp53R270H；MMTV-Cre 双突变小鼠乳腺癌模型。通过组织学、标志物分析、转录谱分析、单细胞 RNA-seq 和生物信息学对肿瘤进行了特征描述。从突变肿瘤中开发了细胞系，用于鉴定和确认参与转移的基因。
我们发现 Pik3caH1047R 和 Trp53R270H 合作驱动乳腺发生癌变，潜伏期比单独使用任何一种突变都短。双突变小鼠会发展出多种组织学上不同的乳腺肿瘤，包括腺癌和肉瘤样（梭形细胞）癌。我们发现一些肿瘤具有侵袭性，少数转移到肺和/或淋巴结。肿瘤的单细胞 RNA-seq 分析鉴定出上皮、基质、髓样和 T 细胞群。对转移性肿瘤的表达分析确定 S100a4 是与转移相关的顶级候选基因。转移性肿瘤中上皮-间充质转化（EMT）特征阳性和 S100a4 表达细胞的比例明显更高。CRISPR/CAS9 介导的转移性肿瘤衍生细胞系中 S100a4 的敲除破坏了其转移潜力，表明 S100a4 参与了转移。
Pik3caH1047R；Trp53R270H；MMTV-Cre 小鼠提供了一种临床前模型，可以模拟携带 PIK3CA 和 TP53 突变的人类乳腺癌的一种亚型。它还允许了解两种突变基因在肿瘤发生中的合作。我们的模型还为研究转移和为 PIK3CA/TP53 双阳性癌症开发治疗策略提供了一个系统。在该模型中发现参与转移的 S100a4 可以作为潜在的诊断和治疗靶点。
