Ethanolic and partially purified aqueous extracts from the sea cucumber Holothuria polii induce a tumor suppressive phenotype in MDA-MB-231 breast cancer cells -

Abstract

The concept of functional food has always been implemented in traditional remedies against various chronic diseases. Sea cucumbers are considered as one of the most important functional foods for their effectiveness against various human disorders. We soughtto investigate the presence of anti-cancer bioactivities in Holothuria polii, the most abundant sea cucumbers inhabiting theLebanese coastin the Mediterranean. Sea cucumber ethanolic extract (SCE) inhibited the proliferation of highly invasive breast cancer MDA-MB-231 cells by 60percent in both, 2D (plastic) and 3D (matrigel) cultures compared to untreated cells. Cell cycle analysis showed a 140percent S-phase prolongation in SCE treated cells compared to untreated cells in 2D conditions. Further, SCE treatment favored spherical aggregate morphology over stellate outgrowths in 3D cultures of MDA-MB-231 cells, coupled by a 70percent decrease in their invasive ability as shown by trans-well matrigel invasion assays. RT-qPCR data showed that SCE treatment decreased the mRNA levels of Vimentin in 2D and 3D cultures of MDA-MB-231 cells by 20percent and 40percent respectively. Twist expression was decreased by 60percent in 3D but not in 2D cultures, in contrast to Zeb1 expression, which showed a 25percent decrease in 2D cultures but not in 3D conditions. Western blot analysis demonstrated a decrease in Vimentin protein expression in 2D and 3D cultures of SCE treated MDA-MB-231 and a downregulation in N-Cadherin expression in 3D conditions. Bio-guided fractionation showed that the aqueous (Aq) fraction among all the collected fractions retained the activity detected in SCE, whereby Aq fractiontreatment decreased proliferation and invasion, prolonged S-phase of the cell cycle, favored spherical clusters over stellate outgrowths and decreased the expression of EMT markers in MDA-MB-231 cells. In conclusion, the tumor suppressive phenotype induced by SCE and the purified Aq fraction is not solely attributed to an inhibition in cellular proliferation but also in conjunction with a partial reestablishm