S100A6 and breast cancer: In addition, overexpression of PDGFD (9, 10), a provascular growth factor in ovarian and colon cancers, predicts chemoresistance, and exosomes secreted by Mesenchymal Stem Cells(MSCs) can affect S100 Calcium Binding Protein A6(S100A6)expression to mediate chemotherapy resistance in breast cancer (11).