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Do altering in ornithine decarboxylase activity and gene expression contribute to antiproliferative properties of COX inhibitors?

Ostrowski J, Wocial T, Skurzak H, Bartnik W - Br. J. Cancer (2003)

Bottom Line: An induction of COX-2 found in neoplastic tissues results in increased cell growth, inhibition of apoptosis, activation of angiogenesis, and decreased immune responsiveness.Aspirin exhibited a small antiproliferative effect that was not associated with apoptosis.The two COX inhibitors did not change c-myc expression, significantly decreased the expression of Egr-1, and differentially altered expression of c-fos; aspirin did not change, but celecoxib dramatically decreased the levels of c-fos-mRNA.

View Article: PubMed Central - PubMed

Affiliation: Department of Gastroenterology, Medical Center for Postgraduate Education, Warsaw, Poland. jostrow@warman.com.pl

ABSTRACT
Two isoforms of cyclooxygenase (COX) participate in growth control; COX-1 is constitutively expressed in most cells, and COX-2 is an inducible enzyme in response to cellular stimuli. An induction of COX-2 found in neoplastic tissues results in increased cell growth, inhibition of apoptosis, activation of angiogenesis, and decreased immune responsiveness. Although both COX-1 and COX-2 inhibitors are suppressors of cell proliferation and appear to be chemopreventive agents for tumorigenesis, the molecular mechanisms mediating antiproliferative effect of COX inhibitors are still not well defined. This study contrasts and compares the effects of aspirin and celecoxib, inhibitors of COX-1 and COX-2, in rat hepatoma HTC-IR cells. The following were assessed: cell proliferation and apoptosis, ornithine decarboxylase (ODC) activity, and pattern expression of three immediate-early genes, c-myc, Egr-1, and c-fos. We have shown that the treatment of hepatocytes in vitro with the selective COX-2 inhibitor, celecoxib, was associated with induction of apoptosis and complete inhibition of cellular proliferation. Aspirin exhibited a small antiproliferative effect that was not associated with apoptosis. Treatment with celecoxib produced dose- and time-dependent decrease in ODC activity. In addition, at higher drug concentration the decrease in ODC activity was greater in proliferating than in resting cells. Much lesser inhibitory effect on ODC activity was observed in aspirin-treated cells. The two COX inhibitors did not change c-myc expression, significantly decreased the expression of Egr-1, and differentially altered expression of c-fos; aspirin did not change, but celecoxib dramatically decreased the levels of c-fos-mRNA. Our study revealed that celecoxib and aspirin share the ability to inhibit ODC activity and alter the pattern of immediate-early gene expression. It seems that some of the observed effects are likely to be related to COX-independent pathways. The precise mechanisms of action of COX inhibitors should be defined before using these drugs for cancer chemopreventive therapy.

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The effects of celecoxib and aspirin on proliferation of rat hepatoma HTC-IR cells determined by [3H]thymidine incorporation. Cells were grown in 96-well plates in DMEM containing 10% FBS. After 24 h, cells were exposed to varying concentrations (2.5, 5, 25, and 50 μg ml−1) of celecoxib or aspirin, and 72 h later 0.1 μCi of [3H]thymidine was added to each well for additional 4 h. The radioactivity of collected cellular DNA was determined by scintillation counting. Three independent experiments were performed and the results represent means±s.d. of radioactivity counts expressed in d.p.m. a, b, c indicate significant decrease (a, P<0.05; b, P<0.01; c, P<0.001) in [3H]thymidine incorporation in aspirin- and celecoxib-treated cells compared to cells treated with DMSO.
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fig2: The effects of celecoxib and aspirin on proliferation of rat hepatoma HTC-IR cells determined by [3H]thymidine incorporation. Cells were grown in 96-well plates in DMEM containing 10% FBS. After 24 h, cells were exposed to varying concentrations (2.5, 5, 25, and 50 μg ml−1) of celecoxib or aspirin, and 72 h later 0.1 μCi of [3H]thymidine was added to each well for additional 4 h. The radioactivity of collected cellular DNA was determined by scintillation counting. Three independent experiments were performed and the results represent means±s.d. of radioactivity counts expressed in d.p.m. a, b, c indicate significant decrease (a, P<0.05; b, P<0.01; c, P<0.001) in [3H]thymidine incorporation in aspirin- and celecoxib-treated cells compared to cells treated with DMSO.

Mentions: The results of MTT test were further confirmed by two other proliferation tests. Incorporation of [3H]thymidine into DNA of cultured HTR-IR cells was strongly inhibited by the treatment with celecoxib and only moderately diminished by higher concentrations of aspirin (Figure 2Figure 2


Do altering in ornithine decarboxylase activity and gene expression contribute to antiproliferative properties of COX inhibitors?

Ostrowski J, Wocial T, Skurzak H, Bartnik W - Br. J. Cancer (2003)

The effects of celecoxib and aspirin on proliferation of rat hepatoma HTC-IR cells determined by [3H]thymidine incorporation. Cells were grown in 96-well plates in DMEM containing 10% FBS. After 24 h, cells were exposed to varying concentrations (2.5, 5, 25, and 50 μg ml−1) of celecoxib or aspirin, and 72 h later 0.1 μCi of [3H]thymidine was added to each well for additional 4 h. The radioactivity of collected cellular DNA was determined by scintillation counting. Three independent experiments were performed and the results represent means±s.d. of radioactivity counts expressed in d.p.m. a, b, c indicate significant decrease (a, P<0.05; b, P<0.01; c, P<0.001) in [3H]thymidine incorporation in aspirin- and celecoxib-treated cells compared to cells treated with DMSO.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2376368&req=5

fig2: The effects of celecoxib and aspirin on proliferation of rat hepatoma HTC-IR cells determined by [3H]thymidine incorporation. Cells were grown in 96-well plates in DMEM containing 10% FBS. After 24 h, cells were exposed to varying concentrations (2.5, 5, 25, and 50 μg ml−1) of celecoxib or aspirin, and 72 h later 0.1 μCi of [3H]thymidine was added to each well for additional 4 h. The radioactivity of collected cellular DNA was determined by scintillation counting. Three independent experiments were performed and the results represent means±s.d. of radioactivity counts expressed in d.p.m. a, b, c indicate significant decrease (a, P<0.05; b, P<0.01; c, P<0.001) in [3H]thymidine incorporation in aspirin- and celecoxib-treated cells compared to cells treated with DMSO.
Mentions: The results of MTT test were further confirmed by two other proliferation tests. Incorporation of [3H]thymidine into DNA of cultured HTR-IR cells was strongly inhibited by the treatment with celecoxib and only moderately diminished by higher concentrations of aspirin (Figure 2Figure 2

Bottom Line: An induction of COX-2 found in neoplastic tissues results in increased cell growth, inhibition of apoptosis, activation of angiogenesis, and decreased immune responsiveness.Aspirin exhibited a small antiproliferative effect that was not associated with apoptosis.The two COX inhibitors did not change c-myc expression, significantly decreased the expression of Egr-1, and differentially altered expression of c-fos; aspirin did not change, but celecoxib dramatically decreased the levels of c-fos-mRNA.

View Article: PubMed Central - PubMed

Affiliation: Department of Gastroenterology, Medical Center for Postgraduate Education, Warsaw, Poland. jostrow@warman.com.pl

ABSTRACT
Two isoforms of cyclooxygenase (COX) participate in growth control; COX-1 is constitutively expressed in most cells, and COX-2 is an inducible enzyme in response to cellular stimuli. An induction of COX-2 found in neoplastic tissues results in increased cell growth, inhibition of apoptosis, activation of angiogenesis, and decreased immune responsiveness. Although both COX-1 and COX-2 inhibitors are suppressors of cell proliferation and appear to be chemopreventive agents for tumorigenesis, the molecular mechanisms mediating antiproliferative effect of COX inhibitors are still not well defined. This study contrasts and compares the effects of aspirin and celecoxib, inhibitors of COX-1 and COX-2, in rat hepatoma HTC-IR cells. The following were assessed: cell proliferation and apoptosis, ornithine decarboxylase (ODC) activity, and pattern expression of three immediate-early genes, c-myc, Egr-1, and c-fos. We have shown that the treatment of hepatocytes in vitro with the selective COX-2 inhibitor, celecoxib, was associated with induction of apoptosis and complete inhibition of cellular proliferation. Aspirin exhibited a small antiproliferative effect that was not associated with apoptosis. Treatment with celecoxib produced dose- and time-dependent decrease in ODC activity. In addition, at higher drug concentration the decrease in ODC activity was greater in proliferating than in resting cells. Much lesser inhibitory effect on ODC activity was observed in aspirin-treated cells. The two COX inhibitors did not change c-myc expression, significantly decreased the expression of Egr-1, and differentially altered expression of c-fos; aspirin did not change, but celecoxib dramatically decreased the levels of c-fos-mRNA. Our study revealed that celecoxib and aspirin share the ability to inhibit ODC activity and alter the pattern of immediate-early gene expression. It seems that some of the observed effects are likely to be related to COX-independent pathways. The precise mechanisms of action of COX inhibitors should be defined before using these drugs for cancer chemopreventive therapy.

Show MeSH
Related in: MedlinePlus