Frondoside A from sea cucumber and nymphaeols from Okinawa propolis: Natural anti-cancer agents that selectively inhibit PAK1 in vitro.

A sulfated saponin called "Frondoside A" (FRA) from sea cucumber and ingredients from Okinawa propolis (OP) have been previously shown to suppress the PAK1-dependent growth of A549 lung cancer as well as pancreatic cancer cells. However, the precise molecular mechanism underlying their anti-cancer action still remains to be clarified. In this study, for the first time, we found that both FRA and OP directly inhibit PAK1 in vitro in a selective manner (far more effectively than two other oncogenic kinases, LIMK and AKT). Furthermore, at least two major anti-cancer ingredients of OP, nymphaeols A and C, also directly inhibit PAK1 in vitro in a selective manner. To the best of our knowledge, FRA is the first marine compound that selectively inhibits PAK1. Likewise, these nymphaeols are the first propolis ingredients that selectively inhibit PAK1.