HSP90AB1 and breast carcinoma: To support our observations of increased FN matrix in HSP90β-treated cells, we tested the effect of non-toxic concentrations of HSP90 inhibitors on FN levels by western blot in both the Hs578T breast cancer cell line and the MEF-1 fibroblast line (given the core role of fibroblasts in ECM production) (Figure 11).