Prostaglandin-independent effects of aspirin on cell cycle and putrescine synthesis in human colon carcinoma cells

Abstract

Aspirin consumption has been reported to be able to reduce colorectal cancer risk in humans and in animal models of colon carcinogenesis. Although the mechanism involved in such an effect is not yet clear, both prostaglandin-dependent and -independent effects have been proposed. Using HT-29 Glc(-/+)cells, which originate from a human colon adenocarcinoma, we demonstrated in this study a dose-dependent effect of millimolar concentration of aspirin on cell growth that was concomitant with a rapid accumulation of the cells in the G0/G1 phase, followed by an accumulation in the G2/M phase and by a minor increase in the proportion of cells undergoing nuclear condensation. Cell membrane integrity and cell release into the culture medium were not affected by this treatment. The aspirin effects were apparently unrelated to prostaglandin biosynthesis inhibition, since although these cells were found to express high levels of cyclooxygenase 1 (COX-1) and low levels of COX-2 proteins, they did not produce any measurable net amounts of prostaglandins, based on both utilization of radiolabelled arachidonic acid and the radioimmunoassay of prostaglandins E2 and F2 alpha. In contrast, we identified polyamine biosynthesis as a cellular target of aspirin, since the treatment of HT-29 Glc(-/+) cells with aspirin reduced the flux of L-ornithine through ornithine decarboxylase, an effect that could not be explained by an acute action of the drug on the ornithine decarboxylase catalytic activity. Since polyamine biosynthesis is strictly necessary for HT-29 cell growth, our data suggest that reduced flux through ornithine decarboxylase may participate in the antiproliferative activity of aspirin towards colonic tumoral cells. It is concluded that in HT-29 Glc(-/+) cells that are not functional for prostaglandin production, aspirin can affect cell growth, cell cycle, and polyamine biosynthesis without affecting cell membrane integrity.

Cellular diamine levels in cancer chemoprevention: modulation by ibuprofen and membrane plasmalogens

“…Previous data demonstrating induction of SAT with aspirin [36] and our data demonstrating increased diamine exporter function with ibuprofen, suggest that augmentation of the diamine exporter -SAT membrane complex may be a mechanism of action that contributes to the cancer chemoprevention provided by aspirin and NSAIDs. Our data demonstrating that the actions of ibuprofen on cellular diamines are not stereospecific are consistent with previous publications demonstrating that the anti-cancer actions of aspirin [12] and NSAIDs [37] are independent of COX inhibition. These observations also suggest that safer analogs devoid of COX inhibition might be optimal drug candidates for cancer chemoprevention.…”

“…Similarly, the diamine cadaverine, which is generated by ODC metabolism of lysine (Figure 6), is exported via the diamine exporter [17,18,35]. Previous studies of the anti-cancer actions of aspirin have demonstrated that aspirin decreases polyamine synthesis at the level of ODC [12] and increases polyamine metabolism via induction of spermine/spermidine N-acetyltransferase [SAT; [36]]. With our studies of ibuprofen, we did not detect any drug effects on polyamine synthesis; however, we did measure increased cellular efflux of putrescine.…”

“…While aspirin and NSAIDs act to decrease local inflammation via cyclooxygenase (COX) inhibition, they also produce large decreases in the levels of the polyamines spermidine, putrescine and cadaverine, actions that are independent of COX inhibition [12]. Homeostatic regulation of intracellular polyamine and diamine levels is essential for normal cell growth and restriction of hyperplasia and neoplasia.…”

Aspirin Has Antitumor Effects via Expression of Calpain Gene in Cervical Cancer Cells

“…One of these mechanisms is COX-independent [14, 15]. It is well known that activation of p53 expression is involved [16].…”

Effect of azoxymethane and curcumin on transcriptional levels of cyclooxygenase-1 and -2 during initiation of colon carcinogenesis

“…Moreover, recent data suggest that many selective COX-2 inhibitors have multiple chemopreventive mechanisms including induction of apoptosis, which might be important in inhibiting the initiation of cancer, in a COX-2 independent pathway [35,36]. Eklou-Kalonji et al [37] also reported prostaglandin-independent effects of aspirin on cell growth and cell cycle in colon cancer cells. Thirdly, there are no available data demonstrating that curcumin inhibits COX-2 or PGE2 under normal conditions in contrast to an apparent inhibitory effect on highly enhanced COX-2 expression and PGE2 production observed in colon tumors or induced inflammation [38 Á40].…”