We have been taking unbiased in vivo approaches to the identification key events regulating breast cancer invasion and metastasis. Although cell-based screens have been highly informative in identifying genes involved in tumour cell survival, migration and invasion, these in vitro approaches are largely unsuitable for interrogating the later stages of the metastatic process, in particular the processes of cell dissemination, tumour cell extravasations from the circulation and colonisation of secondary sites.

Using the 4T1 mouse mammary carcinoma model, we have performed an in vivo functional metastasis screen that integrates RNAi technology and massively parallel sequencing. 12 ‘hits' that suppress tumour cell colonisation of the lungs were identified. 3 of the top 5 hits have been validated as novel metastasis suppressor genes in both mouse and human cell lines and functional studies have been undertaken to interrogate mechanism of action. Critically, these findings are clinically relevant in primary breast cancers where there is a significant correlation between elevated expression levels of these suppressor genes and reduced frequency of metastatic events.

In conjunction, we have profiled tumour cells and cancer associated fibroblasts isolated by FACsorting, without intervening in vitro culture, from tumours of the 4T1 cell line series. This has enabled us to identify tumour cell components involved in fibroblast recruitment and activation, and to identify a role for cancer associated fibroblasts in tumour immune modulation.

Together these approaches have been used to uncover novel mechanisms involved in tumour: stroma interactions in breast cancers.