“…Since then, derivative approaches are now able to model metastasis due to expression of co-operating oncogenes (Sinn et al, 1987;Guy et al, 1992;Podsypanina et al, 2008;Adams et al, 2011) and assess mechanisms of pathway perturbation including TGF-b and WNT (Pierce et al, 1995;Li et al, 2000). The introduction of conditional and inducible systems to drive the expression of transgenes has enabled these models to be further refined (Sandgren et al, 1995;Moody et al, 2002;Podsypanina et al, 2008;Menezes et al, 2014;Rutkowski et al, 2014), including a model in mice of invasive lobular breast cancer created using CRISPR/Cas9-mediated disruption of PTEN (Annunziato et al, 2016).…”