title: Early downregulation of Mcl-1 regulates apoptosis triggered by cardiac glycoside UNBS1450.
abstract: Cardiac glycosides (CGs), prescribed to treat cardiovascular alterations, display potent anti-cancer activities. Despite their well-established target, the sodium/potassium (Na(+)/K(+))-ATPase, downstream mechanisms remain poorly elucidated. UNBS1450 is a hemi-synthetic cardenolide derived from 2″-oxovorusharin extracted from the plant Calotropis procera, which is effective against various cancer cell types with an excellent differential toxicity. By comparing adherent and non-adherent cancer cell types, we validated Mcl-1 as a general and early target of UNBS1450. A panel of CGs including cardenolides ouabain, digitoxin and digoxin as well as bufadienolides cinobufagin and proscillaridin A allowed us to generalize our findings. Our results show that Mcl-1, but not Bcl-xL nor Bcl-2, is rapidly downregulated prior to induction of apoptosis. From a mechanistic point of view, we exclude an effect on transcription and demonstrate involvement of a pathway affecting protein stability and requiring the proteasome in the early CG-induced Mcl-1 downregulation, without the involvement of caspases or the BH3-only protein NOXA. Strategies aiming at preventing UNBS1450-induced Mcl-1 downregulation by overexpression of a mutated, non-ubiquitinable form of the protein or the use of the proteasome inhibitor MG132 inhibited the compound's ability to induce apoptosis. Altogether our results point at Mcl-1 as a ubiquitous factor, downregulated by CGs, whose modulation is essential to achieve cell death.
authors.affiliation: Laboratoire de Biologie Moléculaire et Cellulaire du Cancer, Hôpital Kirchberg, 9, rue Edward Steichen, Luxembourg 2540, Luxembourg.
authors.forename: C
authors.identifier: 0000000193088176
authors.initials: C
authors.lastname: Cerella
authors.affiliation: Laboratoire de Biologie Moléculaire et Cellulaire du Cancer, Hôpital Kirchberg, 9, rue Edward Steichen, Luxembourg 2540, Luxembourg.
authors.forename: F
authors.initials: F
authors.lastname: Muller
authors.affiliation: Laboratoire de Biologie Moléculaire et Cellulaire du Cancer, Hôpital Kirchberg, 9, rue Edward Steichen, Luxembourg 2540, Luxembourg.
authors.forename: A
authors.initials: A
authors.lastname: Gaigneaux
authors.affiliation: Laboratoire de Biologie Moléculaire et Cellulaire du Cancer, Hôpital Kirchberg, 9, rue Edward Steichen, Luxembourg 2540, Luxembourg.
authors.forename: F
authors.initials: F
authors.lastname: Radogna
authors.affiliation: Laboratoire de Biologie Moléculaire et Cellulaire du Cancer, Hôpital Kirchberg, 9, rue Edward Steichen, Luxembourg 2540, Luxembourg.
authors.forename: E
authors.initials: E
authors.lastname: Viry
authors.affiliation: 1] Laboratoire de Biologie Moléculaire et Cellulaire du Cancer, Hôpital Kirchberg, 9, rue Edward Steichen, Luxembourg 2540, Luxembourg [2] Department of Pharmacy, College of Pharmacy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: S
authors.initials: S
authors.lastname: Chateauvieux
authors.affiliation: Laboratoire de Biologie Moléculaire et Cellulaire du Cancer, Hôpital Kirchberg, 9, rue Edward Steichen, Luxembourg 2540, Luxembourg.
authors.forename: M
authors.initials: M
authors.lastname: Dicato
authors.affiliation: Department of Pharmacy, College of Pharmacy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea.
authors.forename: M
authors.identifier: 0000000301154725
authors.initials: M
authors.lastname: Diederich
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D031107:Calotropis / Q000378:metabolism; D002298:Cardenolides / Q000494:pharmacology*; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D019169:Jurkat Cells; D007976:Leupeptins / Q000494:pharmacology; D061986:MCF-7 Cells; D064549:Myeloid Cell Leukemia Sequence 1 Protein / Q000096:biosynthesis* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; C494811:BCL2L1 protein, human; D002298:Cardenolides; D007976:Leupeptins; C579095:MCL1 protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2; C510008:UNBS 1450; D051020:bcl-X Protein; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde