Enhancement of the caspase-independent apoptotic sensitivity of pancreatic cancer cells by DHMEQ, an NF-kappaB inhibitor.
The effects of the nuclear factor (NF)-kappaB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), combined with tumor necrosis factor (TNF)-alpha were evaluated in PK-8 pancreatic cancer cells. NF-kappaB was activated by TNF-alpha; however, the administration of DHMEQ abrogated its transcriptional activity. The addition of DHMEQ to TNF-alpha markedly induced apoptosis in PK-8 cells with down-regulation of anti-apoptotic c-FLIP and survivin. Combined treatment significantly suppressed cell viability in vitro, and the anti-tumor effect of DHMEQ was also significant in vivo. We investigated the apoptosis signaling pathway involved in these cell killing effects. Truncated Bid was produced by activated caspase-8, and the subsequent depolarization of the mitochondrial membrane potential (Delta Psi m) peaked at 6 h. Then, the activity of caspase-3 was up-regulated 8-fold. Z-VAD-fmk (a pan-caspase inhibitor) perfectly inhibited the up-regulation of caspase-3 but failed to reverse the cell viability. The above findings indicated that the growth inhibitory effect of combined treatment largely depended on mitochondria-associated caspase-independent apoptosis. The intracellular behavior of apoptosis-inducing factor (AIF) following depolarization of Delta Psi m suggested that AIF executed such a caspase-independent apoptosis. Interestingly, caspase-dependent apoptosis appeared within 6 h, whereas the caspase-independent apoptosis lagged. Thus, the addition of DHMEQ to TNF-alpha was capable of inducing caspase-independent apoptosis in pancreatic cancer cells. Once caspase-independent apoptosis was induced, the apoptosis demonstrated powerful cytotoxicity. Therefore, DHMEQ in combination with TNF-alpha may be a promising treatment for pancreatic cancer.
Matsumoto
Gaku
G
Department of Surgery, Tokyo Metropolitan Komagome Hospital, Bunkyo-ku, Tokyo 113-8677, Japan.
Muta
Mariko
M
Umezawa
Kazuo
K
Suzuki
Tomoyoshi
T
Misumi
Keizo
K
Tsuruta
Koji
K
Okamoto
Atsutake
A
Toi
Masakazu
M
D017209:Apoptosis / Q000187:drug effects*; D001549:Benzamides / Q000494:pharmacology*; D053148:Caspase 3; D020169:Caspases / Q000096:biosynthesis / Q000378:metabolism*; D002470:Cell Survival; D003512:Cyclohexanones / Q000494:pharmacology*; D004347:Drug Interactions; D006801:Humans; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology; D010190:Pancreatic Neoplasms / Q000473:pathology*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D015854:Up-Regulation
D001549:Benzamides; D003512:Cyclohexanones; D014409:Tumor Necrosis Factor-alpha; C464444:dehydroxymethylepoxyquinomicin; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases