ABSTRACT
Lactacystin (LC) is a specific inhibitor of the proteasome, and has recently been shown to induce apoptosis in certain cell lines. In the present study, we established Fas-resistant adult T-cell leukemia (ATL) cell subclones RSO4 and RST1 from their parental Fas-sensitive cell lines SO4 and ST1, and examined whether LC can overcome Fas resistance. LC completely inhibited proteasome function as determined by a peptidyl-MCA substrate (LLVY-MCA and LLE-MCA), and induced apoptosis in these cell lines irrespective of Fas sensitivity at low concentrations (approximately 10 microM). LC induced the activation of caspase 3 (CPP32/Yama) and caspase 6 proteases in an identical manner to Fas-mediated apoptosis. Moreover, LC induced the activation of caspase 8 (FLICE) protease, which is the initiator of the Fas-mediated apoptotic cascade. Synthesized proteasome inhibitory peptide MG-115 (ZLLnV-CHO) also induced apoptosis in these cell lines. These results indicated that proteasome inhibitors overcome Fas-resistance by bypassing the proximal part of the Fas signal. Inhibition of the proteasome function may be a new strategy for the treatment of ATL.
Subject(s)
Acetylcysteine/analogs & derivatives , Caspases/metabolism , Leukemia, T-Cell/pathology , Acetylcysteine/pharmacology , Adult , Anti-Bacterial Agents/pharmacology , Antigens, Surface/biosynthesis , Apoptosis , Caspase 8 , Caspase 9 , Cysteine Proteinase Inhibitors/pharmacology , Drug Resistance/immunology , Enzyme Activation/drug effects , Humans , Lactams , Sensitivity and Specificity , Tumor Cells, Cultured/enzymology , Tumor Cells, Cultured/metabolism , fas Receptor/immunology , fas Receptor/pharmacologyABSTRACT
A preventive role for human T-cell leukemia virus type-I (HTLV-I) and Fas-associated phosphatase-1 (FAP-1) in Fas-mediated apoptosis has been reported in HTLV-I-infected cells. In the present study, we examined whether these molecules increased during the acquisition of Fas-resistance in adult T-cell leukemia (ATL) cell lines. SO4, ST1 and KK1 are Fas-sensitive ATL cell lines, and produce small amounts of HTLV-I in vitro. Although their subclones RSO4 and RST1 are completely Fas-resistant, they produced an equivalent amount of HTLV-I to SO4 and ST1. Moreover, FAP-1 mRNA was not detected in these cell lines irrespective of Fas sensitivity. Thus, Fas resistance in ATL cells was not directly associated with the increased production of HTLV-I or FAP-1.
Subject(s)
Apoptosis/immunology , Carrier Proteins/biosynthesis , Human T-lymphotropic virus 1/isolation & purification , Leukemia, T-Cell/metabolism , Leukemia, T-Cell/virology , Protein Tyrosine Phosphatases/biosynthesis , fas Receptor/immunology , Antibodies, Monoclonal/pharmacology , Apoptosis/drug effects , Blotting, Southern , Carrier Proteins/genetics , Carrier Proteins/immunology , Clone Cells , DNA Fragmentation/drug effects , DNA, Complementary/biosynthesis , Drug Resistance, Neoplasm , Human T-lymphotropic virus 1/genetics , Humans , Leukemia, T-Cell/genetics , Leukemia, T-Cell/pathology , Protein Phosphatase 1 , Protein Tyrosine Phosphatase, Non-Receptor Type 13 , Protein Tyrosine Phosphatases/genetics , Protein Tyrosine Phosphatases/immunology , Proto-Oncogene Proteins c-bcl-2/biosynthesis , RNA, Messenger/biosynthesis , Reverse Transcriptase Polymerase Chain Reaction , Tumor Cells, Cultured , Virus Integration/genetics , fas Receptor/pharmacologyABSTRACT
We evaluated the clinical efficacy of LCR MTB, a reagent developed by Abbott in the USA, in the full automatic ligase chain reaction (LCR) for detection of DNA of M. tuberculosis complex using a thermostable ligase. Using 458 samples isolated from patients with tuberculosis, LCR was compared with a smear method and with a culture method, and was also compared with two other methods of gene amplification, MTD and Amplicor, using 340 and 200 of the 458 samples, respectively. The LCR method detected M. tuberculosis in 49.8% (228/458) of the samples, and was superior to the smear method (31.9%, 146/458) and the culture method (39.1%, 179/458) in sensitivity. The LCR method was also superior to the MTD and Amplicor methods; sensitivity were 37.9% (129/340) for MTD vs. 47.6% (162/340) for LCR, and 56.5% (113/200) for Amplicor vs. 59.5% (119/200) for LCR. These favorable results and the convenience of the LCR method, which enables rapid detection of target genes with a high degree of sensitivity, strongly suggest that LCR MTB is useful as a reagent for detection of M. tuberculosis using nucleic acid amplification.
