title: Synergism of arsenic trioxide and MG132 in Raji cells attained by targeting BNIP3, autophagy, and mitochondria with low doses of valproic acid and vincristine.
abstract: We previously demonstrated that arsenic trioxide (ATO) and proteasome inhibitor MG132 synergistically induced cell death in promonocytic leukaemia cell line U937 but were antagonistic in Burkitt's lymphoma cell line Raji. Here we explore the role of autophagy, expression of BNIP3, and mitochondrial mass, in determining whether ATO and MG132 interaction can be shifted from antagonism to synergism in Raji cells. Treatment with ATO+MG132 increased the percentage of cells with collapsed mitochondrial membrane potential (MMP) in U937 cells, but had no effect in Raji cells. Mitochondria were found in cytoplasmic marginal location in U937 cells but at perinuclear location in Raji cells. ATO+MG132 increased mitochondrial mass in U937 cells but decreased it in Raji cells, while autophagy was increased in both cell lines. BNIP3 was expressed in U937 cells at cytoplasmic marginal locations and was hardly detected in Raji cells. Histone deacetylase (HDAC) inhibitor valproic acid (VPA) increased expression of BNIP3 in Raji cells at perinuclear locations. However antagonism between ATO and MG132 was increased in the presence of low doses of VPA. Addition of vincristine (VCR) blocked autophagy, while VPA+VCR treatment of Raji cells at sub-cytotoxic doses caused BNIP3 and mitochondria to redistribute to cytoplasmic peripheral location and increased mitochondrial mass. ATO+MG132 in the presence of subcytotoxic doses of VPA+VCR caused collapse of MMP in Raji cells, while interaction between ATO and MG132 shifted from antagonism to synergism. We conclude that synergism between ATO and MG132 was attained in Raji cells by disruption of the perinuclear mitochondrial cluster, blockage of selective autophagy of mitochondria (mitophagy) by VCR, increased mitochondrial mass, and upregulation of BNIP3 by VPA.
authors.affiliation: Laboratorio de Inmunología Tumoral (LIT), IDEHU-CONICET, Facultad de Farmacia y Bioquímica, UBA, Buenos Aires, Argentina.
authors.forename: Victoria
authors.initials: V
authors.lastname: Cavaliere
authors.affiliation: Laboratorio de Immunotoxicologia (LaITo), IDEHU-CONICET, Hospital de Clínicas, José de San Martín, Universidad de Buenos Aires (UBA), Buenos Aires, Argentina.
authors.forename: Tomás
authors.initials: T
authors.lastname: Lombardo
authors.affiliation: Laboratorio de Inmunología Tumoral (LIT), IDEHU-CONICET, Facultad de Farmacia y Bioquímica, UBA, Buenos Aires, Argentina.
authors.forename: Susana N
authors.initials: SN
authors.lastname: Costantino
authors.affiliation: Servicio de Hematología, Hospital de Clínicas, José de San Martín (UBA), Buenos Aires, Argentina.
authors.forename: Laura
authors.initials: L
authors.lastname: Kornblihtt
authors.affiliation: Laboratorio de Inmunología Tumoral (LIT), IDEHU-CONICET, Facultad de Farmacia y Bioquímica, UBA, Buenos Aires, Argentina.
authors.forename: Elida M
authors.initials: EM
authors.lastname: Alvarez
authors.affiliation: Laboratorio de Immunotoxicologia (LaITo), IDEHU-CONICET, Hospital de Clínicas, José de San Martín, Universidad de Buenos Aires (UBA), Buenos Aires, Argentina. Electronic address: gblanco@ffyb.uba.ar.
authors.forename: Guillermo A
authors.initials: GA
authors.lastname: Blanco
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology; D001343:Autophagy / Q000187:drug effects*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects; D010087:Oxides / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020298:U937 Cells; D015854:Up-Regulation; D014635:Valproic Acid / Q000008:administration & dosage / Q000494:pharmacology; D014750:Vincristine / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D001152:Arsenicals; C090121:BNIP3 protein, human; D004791:Enzyme Inhibitors; D007976:Leupeptins; D008565:Membrane Proteins; D010087:Oxides; D011518:Proto-Oncogene Proteins; D014750:Vincristine; D014635:Valproic Acid; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D000077237:Arsenic Trioxide
keywords: Arsenic trioxide; Autophagy; BNIP3; Burkitt’s lymphoma; MG132; Mitochondria; Mitophagy; Synergism; Targeted combined therapies; Valproic acid