ABSTRACT
The tumour stroma is believed to contribute to some of the most malignant characteristics of epithelial tumours. However, signalling between stromal and tumour cells is complex and remains poorly understood. Here we show that the genetic inactivation of Pten in stromal fibroblasts of mouse mammary glands accelerated the initiation, progression and malignant transformation of mammary epithelial tumours. This was associated with the massive remodelling of the extracellular matrix (ECM), innate immune cell infiltration and increased angiogenesis. Loss of Pten in stromal fibroblasts led to increased expression, phosphorylation (T72) and recruitment of Ets2 to target promoters known to be involved in these processes. Remarkably, Ets2 inactivation in Pten stroma-deleted tumours ameliorated disruption of the tumour microenvironment and was sufficient to decrease tumour growth and progression. Global gene expression profiling of mammary stromal cells identified a Pten-specific signature that was highly represented in the tumour stroma of patients with breast cancer. These findings identify the Pten-Ets2 axis as a critical stroma-specific signalling pathway that suppresses mammary epithelial tumours.
Subject(s)
Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Fibroblasts/metabolism , Neoplasms, Glandular and Epithelial/metabolism , Neoplasms, Glandular and Epithelial/pathology , PTEN Phosphohydrolase/metabolism , Stromal Cells/metabolism , Animals , Cell Line, Tumor , Cell Proliferation , Cell Transformation, Neoplastic , Extracellular Matrix/metabolism , Gene Deletion , Gene Expression Regulation, Neoplastic , Humans , Immunity, Innate , Mammary Neoplasms, Experimental/metabolism , Mammary Neoplasms, Experimental/pathology , Mice , Mice, Transgenic , PTEN Phosphohydrolase/deficiency , PTEN Phosphohydrolase/genetics , Proto-Oncogene Protein c-ets-2/deficiency , Proto-Oncogene Protein c-ets-2/metabolismABSTRACT
We developed stromal- and epithelial-specific cre-transgenic mice to directly visualize epithelial-mesenchymal transition (EMT) during cancer progression in vivo. Using three different oncogene-driven mouse mammary tumor models and cell-fate mapping strategies, we show in vivo evidence for the existence of EMT in breast cancer and show that myc can specifically elicit this process. Hierarchical cluster analysis of genome-wide loss of heterozygosity reveals that the incidence of EMT in invasive human breast carcinomas is rare, but when it occurs it is associated with the amplification of MYC. These data provide the first direct evidence for EMT in breast cancer and suggest that its development is favored by myc-initiated events.
