title: Monepantel induces autophagy in human ovarian cancer cells through disruption of the mTOR/p70S6K signalling pathway.
abstract: We have recently shown that the novel anthelmintic drug monepantel (MPL) inhibits growth, proliferation and colony formation, arrests the cell cycle and induces cleavage of PARP-1 in ovarian cancer cell lines. Here we report on the mechanism behind the anticancer properties of MPL. The cytotoxic effect of MPL on ovarian cancer cells (OVCAR-3 and A2780) was investigated employing a panel of tests used for the detection of apoptosis and autophagy. Apoptosis and autophagy were defined by caspase activity, DNA-laddering, Annexin-V and acridine orange (AO) staining. Autophagy markers such as LC3B, SQSTM1/p62 and mammalian target of rapamycin (mTOR) pathway related proteins were assessed by western blotting and ELISA techniques. MPL did not activate caspases 3 or 8, nor did it alter the percentage of Annexin V positive stained cells. Failure to cause DNA laddering and the inability of z-VAD-fmk to block the MPL antiproliferative effects led to the ruling out of apoptosis as the mechanism behind MPL-induced cell death. On the other hand, accumulation of acidic vacuoles with distinct chromatin morphology and an increase in punctuate localization of green fluorescent protein-LC3B, and MPL-induced changes in the expression of SQSTM1/p62 were all indicative of MPL-induced autophagy. Consistent with this, we found inhibition of mTOR phosphorylation leading to suppression of the mTOR/p70S6K signalling pathway. Our findings provide the first evidence to show that MPL triggers autophagy through the deactivation of mTOR/p70S6K signalling pathway.
authors.affiliation: Cancer Research Laboratory, Department of Surgery, University of New South Wales, St George Hospital Sydney, New South Wales, 2217, Australia.
authors.forename: Farnaz
authors.initials: F
authors.lastname: Bahrami
authors.affiliation: Cancer Research Laboratory, Department of Surgery, St George Hospital Sydney, New South Wales, 2217, Australia.
authors.forename: Mohammad H
authors.initials: MH
authors.lastname: Pourgholami
authors.affiliation: Cancer Research Laboratory, Department of Surgery, University of New South Wales, St George Hospital Sydney, New South Wales, 2217, Australia.
authors.forename: Ahmed H
authors.initials: AH
authors.lastname: Mekkawy
authors.affiliation: Novartis Centre de Recherche Santé Animale CH-1566 St Aubin (FR), Switzerland.
authors.forename: Lucien
authors.initials: L
authors.lastname: Rufener
authors.affiliation: Cancer Research Laboratory, Department of Surgery, University of New South Wales, St George Hospital Sydney, New South Wales, 2217, Australia.
authors.forename: David L
authors.initials: DL
authors.lastname: Morris
keywords: Monepantel; PARP; apoptosis; autophagy; mTOR; ovarian cancer; p70S6K