title: Arsenic induced apoptosis in malignant melanoma cells is enhanced by menadione through ROS generation, p38 signaling and p53 activation.
abstract: BACKGROUND
  Resistance to apoptosis is a prominent feature of melanoma. Pharmacological concentration of arsenic in combination with a widely known oxidant, menadione was explored in this study to synergistically sensitize malignant melanoma cells to apoptosis. The molecular mechanism of apoptosis and the signaling-pathways involved were thoroughly investigated. MATERIALS METHODS AND RESULTS: Menadione synergized NaAsO(2) to significantly increase ROS generation and facilitate the major apoptotic signaling events: alteration of mitochondrial membrane potential, cytochrome c release and anti-apoptotic protein Bcl-2 down-regulation and subsequent activation of caspase-9 and caspase-3 followed by poly-ADP-ribose polymerase-1 cleavage. Antioxidant N-acetyl-L: -cysteine antagonized these events. Investigation of the signaling-pathway revealed significant suppression of AP-1 activity but not NF-kappaB upon NaAsO(2) and menadione application. An increase in p38 phosphorylation and p53 protein expression did also dictate the apoptotic response. Suppression of p38 activation with SB203580 and inhibition of p53 expression by siRNA attenuated apoptosis. Transfection of p53, in p53 null HCT cells augmented the apoptotic events. Moreover, the treatment also led to tumor size reduction in BALB/c mice developed by intra-dermal B16 mouse melanoma cell injection; however, it had no detectable pro-proliferative or pro-apoptotic effect on non-tumor keratinocytes, normal fibroblasts or PBMC.
  
  
  CONCLUSIONS
  This study thus provides an insight into innovative mechanisms of melanoma sensitization, a proper cure against which is still elusive. Taken together, our data also provides the first evidence of arsenic activity accentuation by menadione through modulation of specific signaling-pathways.
authors.affiliation: Molecular & Human Genetics Division, Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Kolkata 700032, India.
authors.forename: Rajdeep
authors.initials: R
authors.lastname: Chowdhury
authors.forename: Suchandra
authors.initials: S
authors.lastname: Chowdhury
authors.forename: Paromita
authors.initials: P
authors.lastname: Roychoudhury
authors.forename: Chitra
authors.initials: C
authors.lastname: Mandal
authors.forename: Keya
authors.initials: K
authors.lastname: Chaudhuri
mesh_terms: D000818:Animals; D000933:Antifibrinolytic Agents / Q000494:pharmacology; D017209:Apoptosis; D001151:Arsenic / Q000494:pharmacology*; D018053:Arsenites / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D008545:Melanoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D017382:Reactive Oxygen Species; D017670:Sodium Compounds / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism / Q000502:physiology*; D024483:Vitamin K 3 / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D000933:Antifibrinolytic Agents; D018053:Arsenites; D017382:Reactive Oxygen Species; D017670:Sodium Compounds; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C017947:sodium arsenite; D024483:Vitamin K 3; D048051:p38 Mitogen-Activated Protein Kinases; D001151:Arsenic