title: Decrease in c-Myc activity enhances cancer cell sensitivity to vinblastine.
abstract: The c-myc oncogene encodes for a transcriptional factor involved in many cellular processes such as proliferation, differentiation and apoptosis. According to these different functions, the role of c-Myc protein in cellular sensitivity to anti-cancer drugs is controversial. We defined the role of c-Myc in cancer cell sensitivity to vinblastine (VLB) using human colon cancer cells: LoVo wild-type or transfected with a plasmid containing the human c-myc gene in antisense orientation (LoVo-mycANS). Analysis of VLB cytotoxicity demonstrated a 3-fold increase in VLB sensitivity in LoVo-mycANS cells. Comparison between cells revealed different apoptosis kinetics: accumulation of cells in sub-G1 phase and poly(ADP-ribose) polymerase cleavage occurred earlier in LoVo-mycANS. Then, we demonstrated a mitochondrial membrane potential disruption followed by cytochrome c release that indicates the involvement of mitochondria in this apoptotic signaling pathway. This earlier apoptosis was accompanied by a Bcl-2 decrease and a p53 increase. In conclusion, the decrease in c-Myc expression enhanced the VLB sensitivity, triggering earlier apoptosis through induction of the intrinsic pathway. Thus, c-myc induction is a resistance factor and our findings suggest that tumors carrying low levels of c-Myc protein could be more responsive to vinca alkaloids treatment. Moreover, the downregulation of c-myc oncogene by an antisense strategy might represent a useful goal for improving the efficacy of this anti-neoplastic drug family.
authors.affiliation: CNRS FRE 2737, UFR Pharmacie, University of La Mediterranée, Marseille, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Bressin
authors.forename: Véronique
authors.initials: V
authors.lastname: Bourgarel-Rey
authors.forename: Manon
authors.initials: M
authors.lastname: Carré
authors.forename: Bertrand
authors.initials: B
authors.lastname: Pourroy
authors.forename: Diego
authors.initials: D
authors.lastname: Arango
authors.forename: Diane
authors.initials: D
authors.lastname: Braguer
authors.forename: Yves
authors.initials: Y
authors.lastname: Barra
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000378:metabolism; D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D016373:DNA, Antisense / Q000494:pharmacology; D015536:Down-Regulation; D004361:Drug Tolerance; D016193:G1 Phase / Q000187:drug effects; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014747:Vinblastine / Q000627:therapeutic use*; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D016373:DNA, Antisense; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D014747:Vinblastine; D045304:Cytochromes c; D011065:Poly(ADP-ribose) Polymerases