PTEN and breast cancer: For instance, the physical interaction of breast cancer cells and mesenchymal stem cells can confer resistance to trastuzumab in vitro by activation of non-receptor tyrosine kinase c-SRC and PTEN downregulation [351], and analysis of a prostate cancer TMA has revealed that stroma volume and altered expression of desmin and smooth muscle α-actin are each independent and significant predictors of biochemical recurrence [352].