Inhibition of the PI3K-Akt signaling pathway enhances the sensitivity of Fas-mediated apoptosis in human gastric carcinoma cell line, MKN-45.
It is well known that Fas ligand and anti-Fas antibodies can induce apoptosis, although some cancer cells are resistant to their stimuli. On the other hand, phosphatidylinositol 3'-kinase (PI3 K) and Akt mediate the survival signal and allow the cells to escape from apoptosis in various human cancers. Thus, we postulated that LY294002, a PI3 K inhibitor, should inactivate Akt, consequently inhibiting cell proliferation and increase apoptosis in the human gastric carcinoma cell line, MKN-45. Previously, we reported that MKN-45 was resistant against the anti-Fas antibody, CH-11, without interferon-gamma pretreatment in vitro. LY294002 caused a decrease of phosphorylated-Akt and an inhibition of cell proliferation via cell cycle arrest in the G0/G1 phase by P27/Kip1 accumulation, but there was no obvious induction of apoptosis. The simultaneous treatment of LY294002 and CH-11 significantly induced apoptosis confirmed by morphology and DNA ladder formation. Decreased phosphorylated-Akt by LY294002 treatment led to a down-regulation of Mcl-2 and phosphorylated Bad proteins, which are anti-apoptotic factors and belong to the Bcl-2 family. On the other hand, expression levels of the other anti-apoptotic factors, such as FLICE-inhibitory protein (FLIP), Bcl-2 and Bcl-XL, which are associated with the Fas-mediated apoptotic signal pathway, did not change after LY294002 treatment. We concluded that: 1) the PI3K-Akt pathway plays an important role in preventing Fas-mediated apoptosis; and 2) a PI3 K inhibitor, such as LY294002, might be a useful anti-tumoral agent for gastric carcinoma.
Osaki
Mitsuhiko
M
Division of Organ Pathology, Department of Microbiology and Pathology, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago, 683-8503 Tottori, Japan. osamitsu@grape.med.tottori-u.ac.jp
Kase
Satoru
S
Adachi
Keiko
K
Takeda
Ami
A
Hashimoto
Kiyoshi
K
Ito
Hisao
H
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002277:Carcinoma / Q000188:drug therapy* / Q000378:metabolism; D045744:Cell Line, Tumor; D002867:Chromones / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D053222:Fas Ligand Protein; D005434:Flow Cytometry; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors*; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction / Q000187:drug effects; D013274:Stomach Neoplasms / Q000188:drug therapy* / Q000378:metabolism
D000970:Antineoplastic Agents; D002867:Chromones; D004791:Enzyme Inhibitors; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt