title: Growth inhibition and pro-apoptotic activity of violacein in Ehrlich ascites tumor.
abstract: The continuing threat to biodiversity lends urgency to the need of identification of sustainable source of natural products. This is not so much trouble if there is a microbial source of the compound. Herein, violacein, a natural indolic pigment extracted from Chromobacterium violaceum, was evaluated for its antitumoral potential against the Ehrlich ascites tumor (EAT) in vivo and in vitro. Evaluation of violacein cytotoxicity using different endpoints indicated that EAT cells were twofold (IC(50)=5.0 microM) more sensitive to the compound than normal human peripheral blood lymphocytes. In vitro studies indicated that violacein cytotoxicity to EAT cells is mediated by a rapid (8-12h) production of reactive oxygen species (ROS) and a decrease in intracellular GSH levels, probably due to oxidative stress. Additionally, apoptosis was primarily induced, as demonstrated by an increase in Annexin-V positive cells, concurrently with increased levels of DNA fragmentation and increased caspase-2, caspase-9 and caspase-3 activities up to 4.5-, 6.0- and 5.5-fold, respectively, after 72 h of treatment. Moreover, doses of 0.1 and 1.0 microg kg(-1) violacein, administered intraperitoneally (i.p.) to EAT-bearing mice throughout the lifespan of the animals significantly inhibited tumor growth and increased survival of mice. In view of these results, a 35-day toxicity study was conducted in vivo. Complete hematology, biochemistry (ALT, AST and creatinine levels) and histopathological analysis of liver and kidney indicated that daily doses of violacein up to 1000 microg kg(-1) for 35 days are well tolerated and did not cause hematotoxicity nor renal or hepatotoxicity when administered i.p. to mice. Altogether, these results indicate that violacein causes oxidative stress and an imbalance in the antioxidant defense machinery of cells culminating in apoptotic cell death. Furthermore, this is the first report of its antitumor activity in vivo, which occurs in the absence of toxicity to major organs.
authors.affiliation: Biological Chemistry Laboratory, Instituto de Química, Universidade Estadual de Campinas, Campinas, SP, Brazil.
authors.forename: Natália
authors.initials: N
authors.lastname: Bromberg
authors.forename: Juliana L
authors.initials: JL
authors.lastname: Dreyfuss
authors.forename: Caio V
authors.initials: CV
authors.lastname: Regatieri
authors.forename: Marcelly V
authors.initials: MV
authors.lastname: Palladino
authors.forename: Nelson
authors.initials: N
authors.lastname: Durán
authors.forename: Helena B
authors.initials: HB
authors.lastname: Nader
authors.forename: Marcela
authors.initials: M
authors.lastname: Haun
authors.forename: Giselle Z
authors.initials: GZ
authors.lastname: Justo
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000009:adverse effects / Q000302:isolation & purification / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D002286:Carcinoma, Ehrlich Tumor / Q000188:drug therapy* / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D002861:Chromobacterium / Q000737:chemistry*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000009:adverse effects / Q000302:isolation & purification / Q000627:therapeutic use*; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D007211:Indoles; D017382:Reactive Oxygen Species; D005978:Glutathione; C063155:violacein