Growth inhibition by dehydrothyrsiferol - a non-Pgp modulator, derived from a marine red alga - in human breast cancer cell lines

The novel marine terpenoid dehydrothyrsiferol (DHT) has been isolated from a Canarian red alga Laurencia viridis sp. nov (Ceramiales, Rhodomelaceae) ( I). Its cytotoxicity against three human breast cancer cell Lines, namely T 47D, ZR-75-1, and Hs578T was examined and compared with the chemotherapeuti c compound doxorubicin and the mitosis-inhibitor colchicine. Primary breast carcinomas exhibit MDR1 gene expression (3). As the investigated mammary c ell lines did not exhibit rhodamine 123 efflux we proved in a P-glycoprotei n (Pgp) overexpressing human epidermoid cancer cell line that the marine me tabolite does not modulate Pgp mediated drug transport. Therefore, it could be used in Pgp expressing cancer cells without interference.