Reduced expression of phospholipase C-delta, a signal-transducing enzyme, in rat colon neoplasms induced by methylazoxymethanol acetate.
Phospholipase C (PLC), which hydrolyzes phosphoinositides, has been implicated as a key enzyme in signal transduction. We examined the expression of an isozyme of PLC, PLC-delta, in rat colon neoplasms induced by methylazoxymethanol (MAM) acetate. Large-bowel neoplasms were observed in five of 10 rats given MAM acetate (25 mg/kg body weight, by interperitoneal injection at 6 and 7 wk of age) 40 wk after treatment. Expression of PLC-delta in the neoplasms was not detected by northern blot analysis, and a low level of expression was detected by immunoblot analysis, although PLC-delta expression was apparent in the non-neoplastic colon mucosae of MAM acetate-treated rats as well as in the colon mucosae of control rats. Furthermore, analysis by reverse transcriptase-polymerase chain reaction revealed that the ratio of the expression of PLC-delta to that of beta-actin in the neoplasms was significantly lower than the ratios in the non-neoplastic colon mucosae of carcinogen-treated and control rats (P < 0.01). However, the ornithine decarboxylase (ODC) activity in the neoplasms was significantly greater than that of the non-neoplastic and control mucosae (P < 0.001). The differences in the levels of PLC-delta expression in neoplastic and non-neoplastic tissues and the inverse correlation of PLC-delta expression with ODC activity may suggest that PLC-delta has little effect on the PLC-mediated mitogenic signaling system, at least in MAM acetate-induced colon neoplasms in rats.
Yoshimi
N
N
Department of Pathology, Gifu University School of Medicine, Japan.
Wang
A
A
Makita
H
H
Suzui
M
M
Mori
H
H
Okano
Y
Y
Banno
Y
Y
Nozawa
Y
Y
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D003106:Colon / Q000187:drug effects / Q000201:enzymology; D003110:Colonic Neoplasms / Q000139:chemically induced / Q000201:enzymology*; D015151:Immunoblotting; D007413:Intestinal Mucosa / Q000187:drug effects / Q000201:enzymology; D007527:Isoenzymes / Q000032:analysis* / Q000502:physiology; D008297:Male; D008746:Methylazoxymethanol Acetate; D008969:Molecular Sequence Data; D009955:Ornithine Decarboxylase / Q000378:metabolism; D016133:Polymerase Chain Reaction / Q000379:methods; D012194:RNA-Directed DNA Polymerase; D051381:Rats; D011916:Rats, Inbred F344; D015398:Signal Transduction / Q000502:physiology; D010738:Type C Phospholipases / Q000032:analysis* / Q000502:physiology
D007527:Isoenzymes; D008746:Methylazoxymethanol Acetate; D012194:RNA-Directed DNA Polymerase; D010738:Type C Phospholipases; D009955:Ornithine Decarboxylase