We verified the mass spectrometry result with co-immunoprecipitation of Hsp90α and tPA in conditioned media from HT-1080 fibrosarcoma cells (Figure 5b), the cell line for which we originally discovered the interaction of extracellular hsp90α and MMP-2, and MDA-MB231 cells (data not shown). This evidence concerns the gene MMP2 and fibrosarcoma.