Involvement of caspase-9 in autophagy-mediated cell survival pathway.
Nonsteroidal anti-inflammatory drugs (NSAIDs) have been considered for use in the prevention and treatment of cancer malignancy. FR122047 (FR) is known to have an anti-inflammatory effect, but the anticancer activity of the chemical has not yet been identified. In the present study, we could find that treatment of breast cancer MCF-7 cells with FR led to apoptosis accompanying with apparent activation of caspases. Treatment of caspase-specific inhibitors revealed that FR-induced apoptosis was caspase-8-dependent and inhibition of caspase-9 activity resulted in unexpected, marked enhancement of cell death. Knockdown of caspase-9 expression by specific siRNA caused increased susceptibility to FR-induced cell death, consistent with the results obtained with treatment of caspase-9 inhibitor. Inhibition of caspase-9 blocked the autophagic process by modulating lysosomal pH and acid-dependent cathepsin activities and augmented cell death due to blockage of cytoprotective autophagy. MCF-7 cells treated with sulforaphane, an autophagy-inducing drug, also showed marked accumulation of LC3-II, and co-treatment with caspase-9 inhibitor brought about increased susceptibility to sulforaphane-induced cell death. Different from the cases with FR or sulforaphane, etoposide- or doxorubicin-induced cell death was suppressed with co-treatment of caspase-9 inhibitor, and the drugs failed to induce significant autophagy in MCF-7 cells. Taken together, our data originally suggest that inhibition of caspase-9 may block the autophagic flux and enhance cell death due to blockage of cytoprotective autophagy.
Jeong
Hyo-Soon
HS
Department of Animal Biotechnology, Konkuk University, Seoul, South Korea.
Choi
Hye Yeon
HY
Lee
Eung-Ryoung
ER
Kim
Jung-Hyun
JH
Jeon
Kilsoo
K
Lee
Hyun-Joo
HJ
Cho
Ssang-Goo
SG
D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D016588:Anticarcinogenic Agents / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D053453:Caspase 9 / Q000235:genetics / Q000378:metabolism*; D061945:Caspase Inhibitors; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003593:Cytoplasm / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005047:Etoposide / Q000494:pharmacology; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D017879:Isothiocyanates; D008928:Mitochondria / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013454:Sulfoxides; D013861:Thiocyanates / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000903:Antibiotics, Antineoplastic; D016588:Anticarcinogenic Agents; D000972:Antineoplastic Agents, Phytogenic; D061945:Caspase Inhibitors; D017879:Isothiocyanates; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D013454:Sulfoxides; D013861:Thiocyanates; D005047:Etoposide; D004317:Doxorubicin; D053453:Caspase 9; C016766:sulforaphane