PTK6 and breast cancer: A semisynthetic analogue of sipholenol A, sipholenol A-4-O-3′,4′-dichlorobenzoate (69, Figure 19) was associated with the suppression of the Brk and FAK signaling pathway in vitro and in vivo, also inhibited MDA-MB-231, MCF-7, BT-474 and T-47D breast cancer cells with IC50 values of 7.5 μM, 15.2 μM, 20.1 μM and 25.1 μM, respectively, making it a potentially interesting pro-drug for sipholenol A [89].