Suppression of MMP9 expression (by inhibiting NFκB and AP‐1) and reduction of lung metastasis by PEITC, BITC, and SFN was shown in an A549 xenograft mouse model.70 The inhibition of MMP2 activity by PEITC and BITC, which was accompanied by reduced cell migration and invasion, was also reported in the human melanoma cell line A375.S271 and in the mouse melanoma cell line B16F10.72 Both MMP2 and MMP9 are client proteins of HSP90 (Table 1), but whether or not the inhibitory effect of PEITC could be in part a consequence of HSP90 inhibition has not been investigated. Here, MMP9 is linked to melanoma.