title: Differential effects of proteasome inhibitors on cell cycle and apoptotic pathways in human YT and Jurkat cells.
abstract: Herein, we report differential effects of various proteasome inhibitors including clasto-lactacystin-beta-lactone, (-)-epigallocatechin gallate (EGCG) and N-Acetyl-Leu-Leu-Norleu-al (LLnL) on proteasomal activities of YT and Jurkat cells, human natural killer (NK) and T cell lines, respectively. The inhibitory rates of these inhibitors on the purified 20S proteasomal and 26S proteasomal chymotrypsin-like activity in whole cell extracts and intact cells did not show significant differences between the two cell lines. The viability of both cell lines was reduced in the presence of LLnL. Subsequent studies revealed a reduction of the mitochondrial membrane potential and caspase-3 activation in these two cell lines upon treatment with proteasome inhibitors; however, caspase-3 activation occurred much earlier in Jurkat cells. Cell cycle analysis indicated a sub-G(1) apoptotic cell population in Jurkat cells and G(2)/M arrest in YT cells after they were treated by proteasome inhibitors. Moreover, pretreatment of YT cells by a caspase inhibitor followed by a proteasome inhibitor did not increase the percentage of G(2)/M phase cells. In addition, accumulation of p27 and IkappaB-alpha was detected only in Jurkat cells, but not YT cells. In summary, proteasome inhibitors may act differentially in cell cycle arrest and apoptosis of tumors of NK and T cell origin, and may have similar effects on normal NK and T cells.
authors.affiliation: Department of Molecular Biology and Immunology, Institute for Cancer Research, University of North Texas Health Science Center, 3500 Camp Bowie Blvd., Fort Worth, TX 76107-2699, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Lu
authors.forename: Q Ping
authors.initials: QP
authors.lastname: Dou
authors.forename: Richard P
authors.initials: RP
authors.lastname: Kitson
authors.forename: David M
authors.initials: DM
authors.lastname: Smith
authors.forename: Ronald H
authors.initials: RH
authors.lastname: Goldfarb
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects*; D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D006801:Humans; D019169:Jurkat Cells; D061988:Proteasome Inhibitors
chemical_list: D015853:Cysteine Proteinase Inhibitors; D061988:Proteasome Inhibitors; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases