Reprogramming of the tumour microenvironment by stromal PTEN-regulated miR-320

Abstract

PTEN (Phosphatase and tensin homolog deleted on chromosome 10) expression in stromal fibroblasts suppresses epithelial mammary tumours, but the underlying molecular mechanisms remain unknown. Using proteomic and expression profiling, we show that Pten loss from mammary stromal fibroblasts activates an oncogenic secretome that orchestrates the transcriptional reprogramming of other cell types in the microenvironment. Downregulation of miR-320 and upregulation of one of its direct targets, ETS2 (v-ets erythroblastosis virus E26 oncogene homolog 2) are critical events in Pten-deleted stromal fibroblasts responsible for inducing this oncogenic secretome, which in turn promotes tumour angiogenesis and tumour-cell invasion. Expression of the Pten–miR-320–Ets2-regulated secretome distinguished human normal breast stroma from tumour stroma and robustly correlated with recurrence in breast cancer patients. This work reveals miR-320 as a critical component of the Pten tumour-suppressor axis that acts in stromal fibroblasts to reprogramme the tumour microenvironment and curtail tumour progression. Ostrowski and colleagues identify a tumour-suppressive pathway in the tumour stroma. They show that PTEN loss in stromal fibroblasts downregulates miR-320, leading to the upregulation of the ETS2 transcription factor and the induction of a secretome that promotes tumour growth, invasion and angiogenesis.

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Bronisz, A., Godlewski, J., Wallace, J. et al. Reprogramming of the tumour microenvironment by stromal PTEN-regulated miR-320. Nat Cell Biol 14, 159–167 (2012). https://doi.org/10.1038/ncb2396

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