title: Pentoxifylline and the proteasome inhibitor MG132 induce apoptosis in human leukemia U937 cells through a decrease in the expression of Bcl-2 and Bcl-XL and phosphorylation of p65.
abstract: BACKGROUND
  In Oncology, the resistance of the cancerous cells to chemotherapy continues to be the principal limitation. The nuclear factor-kappa B (NF-κB) transcription factor plays an important role in tumor escape and resistance to chemotherapy and this factor regulates several pathways that promote tumor survival including some antiapoptotic proteins such as Bcl-2 and Bcl-XL. In this study, we investigated, in U937 human leukemia cells, the effects of PTX and the MG132 proteasome inhibitor, drugs that can disrupt the NF-κB pathway. For this, we evaluated viability, apoptosis, cell cycle, caspases-3, -8, -9, cytochrome c release, mitochondrial membrane potential loss, p65 phosphorylation, and the modification in the expression of pro- and antiapoptotic genes, and the Bcl-2 and Bcl-XL antiapoptotic proteins.
  
  
  RESULTS
  The two drugs affect the viability of the leukemia cells in a time-dependent manner. The greatest percentage of apoptosis was obtained with a combination of the drugs; likewise, PTX and MG132 induce G1 phase cell cycle arrest and cleavage of caspases -3,-8, -9 and cytochrome c release and mitochondrial membrane potential loss in U937 human leukemia cells. In these cells, PTX and the MG132 proteasome inhibitor decrease p65 (NF-κB subunit) phosphorylation and the antiapoptotic proteins Bcl-2 and Bcl-XL. We also observed, with a combination of these drugs overexpression of a group of the proapoptotic genes BAX, DIABLO, and FAS while the genes BCL-XL, MCL-1, survivin, IκB, and P65 were downregulated.
  
  
  CONCLUSIONS
  The two drugs used induce apoptosis per se, this cytotoxicity was greater with combination of both drugs. These observations are related with the caspases -9, -3 cleavage and G1 phase cell cycle arrest, and a decrease in p65 phosphorylation and Bcl-2 and Bcl-XL proteins. As well as this combination of drugs promotes the upregulation of the proapoptotic genes and downregulation of antiapoptotic genes. These observations strongly confirm antileukemic potential.
authors: División de Inmunología, Centro de Investigación Biomédica de Occidente CIBO, Instituto Mexicano del Seguro Social IMSS, Sierra Mojada 800, Col, Independencia, Guadalajara, Jalisco 44340, México.
authors: Alejandro
authors: A
authors: Bravo-Cuellar
authors: Georgina
authors: G
authors: Hernández-Flores
authors: José Manuel
authors: JM
authors: Lerma-Díaz
authors: Jorge Ramiro
authors: JR
authors: Domínguez-Rodríguez
authors: Luis F
authors: LF
authors: Jave-Suárez
authors: Ruth
authors: R
authors: De Célis-Carrillo
authors: Adriana
authors: A
authors: Aguilar-Lemarroy
authors: Paulina
authors: P
authors: Gómez-Lomeli
authors: Pablo Cesar
authors: PC
authors: Ortiz-Lazareno
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007938:Leukemia / Q000188:drug therapy / Q000235:genetics / Q000473:pathology; D007976:Leupeptins / Q000494:pharmacology*; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D010431:Pentoxifylline / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics*; D015398:Signal Transduction; D020298:U937 Cells; D051020:bcl-X Protein / Q000096:biosynthesis / Q000235:genetics*
chemical_list: C494811:BCL2L1 protein, human; D002352:Carrier Proteins; C484020:HSAJ2425 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D007976:Leupeptins; D016328:NF-kappa B; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D010431:Pentoxifylline