Reduced expression of phospholipase C-delta, a signal-transducing enzyme, in rat colon neoplasms induced by methylazoxymethanol acetate.

Abstract

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.

• Authors: N Yoshimi, A Wang, H Makita, M Suzui, H Mori, Y Okano, Y Banno, Y Nozawa
• Journal: Molecular carcinogenesis (Mol Carcinog) Vol. 11 Issue 4 Pg. 192-6 (Dec 1994) ISSN: 0899-1987 [Print] United States
• PMID: 7528022 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Isoenzymes
• Methylazoxymethanol Acetate
• RNA-Directed DNA Polymerase
• Type C Phospholipases
• Ornithine Decarboxylase

Topics

• Animals
• Base Sequence
• Blotting, Northern
• Colon (drug effects, enzymology)
• Colonic Neoplasms (chemically induced, enzymology)
• Immunoblotting
• Intestinal Mucosa (drug effects, enzymology)
• Isoenzymes (analysis, physiology)
• Male
• Methylazoxymethanol Acetate
• Molecular Sequence Data
• Ornithine Decarboxylase (metabolism)
• Polymerase Chain Reaction (methods)
• RNA-Directed DNA Polymerase
• Rats
• Rats, Inbred F344
• Signal Transduction (physiology)
• Type C Phospholipases (analysis, physiology)