Inhibition of human pancreatic cancer cell (MIA PaCa-2) growth by cholera toxin and 8-chloro-cAMP in vitro.
The effects of cholera toxin (CT) and 8-chloro-cAMP (8-Cl-cAMP) on cell growth were investigated using two human pancreatic carcinoma cell lines (MIA PaCa-2, Panc-1). CT, which catalyses the ADP ribosylation of Gs, suppresses the proliferation of MIA PaCa-2(PC) cells. CT at the low dose of 0.1 pg ml-1 was inhibitory of PC cell growth, and the maximum suppression (70%) was achieved at a CT concentration of 100 pg ml-1. This phenomenon was reversible. The production of cAMP by CT (100 pg ml-1) in PC cells was enhanced 320-fold compared with the control. In addition, cAMP analogues (8-Cl-cAMP, 8-Br-cAMP) and forskolin decreased the growth rate of PC cells in a dose-dependent manner. These results support the view that CT suppresses PC cell growth by stimulating cAMP production. Conversely, Panc-1 cells were far less sensitive to CT in cell growth and cAMP production. 8-Cl-cAMP was also less effective on Panc-1 cell growth. The binding of an insulin-like growth factor (IGF)-I and transforming growth factor (TGF)-alpha, which has been shown to stimulate PC cell growth in an autocrine manner, to PC cells was not modified in cells treated with CT or 8-Cl-cAMP. The results suggest that the inhibitory actions of these substances do not occur at the level of the receptor for IGF-I or EGF/TGF-alpha. We have previously shown that phorbol esters, which decrease the binding of TGF-alpha to PC cells, has an anti-proliferative activity on these tumour cells. Inhibited cell growth by maximum suppressive dose of CT or 8-Cl-cAMP was further inhibited by TPA. In addition, an oncogene product of K-ras which is commonly activated in pancreatic cancer, was increased by CT and 8-Cl-cAMP. It is concluded that CT and 8-Cl-cAMP inhibit PC cell growth, presumably in a similar manner, and their mechanism(s) of action may be different from that of TPA. The anti-proliferative effect of CT or 8-Cl-cAMP was enhanced by TPA, implying that the combination of these substances results in increased inhibition of the PC cell growth.
Ohmura
E
E
Department of Medicine, Tokyo Women's Medical College, Japan.
Wakai
K
K
Isozaki
O
O
Murakami
H
H
Onoda
N
N
Emoto
N
N
Shizume
K
K
Tsushima
T
T
Demura
H
H
Robins
R K
RK
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002772:Cholera Toxin / Q000494:pharmacology*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis; D004357:Drug Synergism; D004815:Epidermal Growth Factor / Q000378:metabolism; D006801:Humans; D007155:Immunologic Factors / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000970:Antineoplastic Agents; D007155:Immunologic Factors; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D002772:Cholera Toxin; C044258:8-chloro-cyclic adenosine monophosphate; D000242:Cyclic AMP; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D013755:Tetradecanoylphorbol Acetate