AbstractBackgroundBreast cancers acquire aggressive capabilities via epithelial to mesenchymal transition (EMT), in which various integrins/integrin-linked kinase signalling are upregulated.MethodsWe investigated this in two patient-derived xenografts (PDXs) developed from breast-to-bone metastases, and its functional significance in a breast cancer cell line system. ED03 and EDW01 PDXs were grown subcutaneously in immunocompromised SCID mice through 11 passages and 7 passages, respectively. Tumour tissue was assessed using immunohistochemistry (IHC) for oestrogen receptor (ER)-alpha, E-cadherin, vimentin, Twist1, beta-catenin, P120-RasGAP, CD44, CD24 and Ki67, and RT-qPCR of EMT-related factors (CDH1,VIM,CD44,CD24), integrins beta 1 (ITGB1), alpha 2 (ITGA2) andILK. Integrin andILKexpression in epidermal growth factor (EGF)-induced EMT of the PMC42-ET breast cancer cell line was assessed by RT-qPCR and Western blotting, as were the effects of their transient knockdown via small interfering RNA +/− EGF. Cell migration, changes in cell morphology and adhesion of siRNA-transfected PMC42-ET cells to various extracellular matrix (ECM) substrates was assessed.ResultsThe ED03 (ER+/PR−/HER2−/lobular) and EDW01 (ER+/PR−/HER2−/ductal) PDXs were both classified as molecular subtype luminal A. ED03 xenografts exhibited mutated E-cadherin with minimal expression, but remained vimentin-negative across all passages. In EDW01, the hypoxic indicator gene CAIX and Twist1 were co-ordinately upregulated at passages 4–5, corresponding with a decrease in E-cadherin. At passages 6–7,VIMwas upregulated along withITGB1andITGA2, consistent with an increasing EMT. The ED03 PDX displayed minimal change over passages in mice, for all genes examined.ILK,ITGB1andITGA2mRNAs were also increased in the EGF-induced EMT of PMC42-ET cells (in whichCDH1was downregulated) although siRNA against these targets revealed that this induction was not necessary for the observed EMT. However, their knockdown significantly reduced EMT-associated adhesion and Transwell migration.ConclusionOur data suggest that despite an increase inITGA2andITGB1gene expression in the EMT exhibited by EDW01 PDX over multiple generations, this pathway may not necessarily drive the EMT process.