Do early premalignant changes in normal breast epithelial cells predict cancer development?

A recent report suggests that, in an in vitro model of premalignant breast cells (vHMECs), silencing of INK4A gene is accompanied by over-expression of cyclo-oxygenase (COX)-2. This suggests that COX-2 over-expression may be an early event in breast cancer aetiology permitting clones within the normal epithelium to evade apoptosis, to increase their numbers and perhaps acquire further changes that promote the formation of hyperplasias, and eventually carcinomas. While COX-2 expression in normal breast epithelium in vivo has not been proven to be linked to an increased risk of breast cancer, its over-expression in the premalignant model in vitro does provide preliminary evidence that COX-2 inhibition may be a useful chemoprevention strategy.

Endothelin-1 Induces Cyclooxygenase-2 Expression and Generation of Reactive Oxygen Species in Endothelial Cells

Since both endothelin-1 (ET-1) and aldosterone have been shown to induce expression of several pro-inflammatory genes, including cyclooxygenase-2 (COX-2), in the vasculature as a cardiovascular risk hormone, the present study was undertaken to examine the effects of ET-1 and aldosterone on COX-2 gene expression as measured by a real-time reverse transcriptase-polymerase chain reaction in aortic endothelial cells. Treatment with ET-1(10 M) markedly upregulated COX-2 mRNA levels in rat endothelial cells, whereas aldosterone (10 M) did not show any effect. The ET-1-induced COX-2 upregulation was inhibited by pretreatment with a non-selective endothelin receptor antagonist (TAK044), a protein kinase C inhibitor (GF109203X), and a MEK inhibitor (PD98059). Furthermore, ET-1 increased intracellular reactive oxygen species generation as estimated by the measurement of dichlorofluorescein fluorescence, whose effect was blocked by a COX-2 inhibitor (NS398). Our data show that ET-1 induces COX-2 upregulation in rat endothelial cells via a protein kinase C-dependent and extracellular signal-regulated kinase-dependent pathway, which may largely contribute to the generation of intracellular reactive oxygen species.

[Effect of celecoxib on enhancing the chemotherapic sensitivity of hydroxyurea to K562 cells and its mechanism]

OBJECTIVE

To determine whether celecoxib can enhance the anti-proliferative effect of hydroxyurea on K562 cells and to reveal its molecular mechanism.

METHODS

K562 cells were treated with low dose celecoxib (40 micromol/L) or hydroxyurea (10 mmol/L) and celecoxib (40 micromol/L) combined with hydroxyurea (10 mmol/L) for 36 h. The effects of the drugs on K562 cell growth inhibitation, apoptosis inducement and its molecular mechanism were analyzed by MTT assay, DNA fragment analysis, Western blotting, and RT-PCR.

RESULTS

The treatment of celecoxib (40 micromol/L) combined with hydroxyurea (10 mmol/L) could significantly inhibit the K562 cell viability and induce the K562 cell apoptosis than those treatments of celecoxib or hydroxyurea alone. The combination of celecoxib and hydroxyurea could evidently inhibit the expression of COX-2 protein or COX-2 mRNA of K562 cells.

CONCLUSION

Celecoxib can enhance the anti-proliferative effect of hydroxyurea on K562 cells, which is associated with the down-regulation of both COX-2 protein and COX-2 mRNA on K562 cells.

[The significance of the expression of cyclooxygenase-2 in bladder transitional cell carcinoma tissues]

OBJECTIVE

To investigate the expression of cyclooxygenase-2 (COX-2) in bladder transitional cell carcinoma tissues, and understand its clinical significance.

METHODS

Reversal transcription polymerase chain reaction (RT-PCR) was used to assess the expression of COX-2 mRNA in 52 cases of bladder transitional cell carcinoma tissues and 17 cases of normal bladder tissues far from neoplasm; Western blot was used to assess the expression of COX-2 protein in 49 cases of bladder cancerous tissues and 17 cases of normal tissues.

RESULTS

Positive expression of COX-2 mRNA was detected in 83% (43/52) of bladder cancer tissues and in 29% (5/17) of normal tissues by RT-PCR and there was significant difference in expression of COX-2 mRNA between cancer tissues and normal tissues. Western blot analysis showed that expression of COX-2 protein was correlation with the stage and grade of cancer.

CONCLUSION

COX-2 is overexpressed in bladder transitional cell carcinoma. COX-2 maybe play a certain role in carcinogenesis and progression of bladder cancer and turn into a useful target of chemoprevention of bladder cancer.

Altered prostanoid production by fibroblasts cultured from the lungs of human subjects with idiopathic pulmonary fibrosis

BACKGROUND

Prostanoids are known to participate in the process of fibrogenesis. Because lung fibroblasts produce prostanoids and are believed to play a central role in the pathogenesis of idiopathic pulmonary fibrosis (IPF), we hypothesized that fibroblasts (HF) cultured from the lungs of patients with IPF (HF-IPF) have an altered balance between profibrotic (thromboxane [TX]A2) and antifibrotic (prostacyclin [PGI2]) prostaglandins (PGs) when compared with normal human lung fibroblasts (HF-NL).

METHODS

We measured inducible cyclooxygenase (COX)-2 gene and protein expression, and a profile of prostanoids at baseline and after IL-1beta stimulation.

RESULTS

In both HF-IPF and HF-NL COX-2 expression was undetectable at baseline, but was significantly upregulated by IL-1beta. PGE2 was the predominant COX product in IL-1beta-stimulated cells with no significant difference between HF-IPF and HF-NL (28.35 [9.09-89.09] vs. 17.12 [8.58-29.33] ng/10(6) cells/30 min, respectively; P = 0.25). TXB2 (the stable metabolite of TXA2) production was significantly higher in IL-1beta-stimulated HF-IPF compared to HF-NL (1.92 [1.27-2.57] vs. 0.61 [0.21-1.64] ng/10(6) cells/30 min, respectively; P = 0.007) and the ratio of PGI2 (as measured by its stable metabolite 6-keto-PGF1alpha) to TXB2 was significantly lower at baseline in HF-IPF (0.08 [0.04-0.52] vs. 0.12 [0.11-0.89] in HF-NL; P = 0.028) and with IL-1beta stimulation (0.24 [0.05-1.53] vs. 1.08 [0.51-3.79] in HF-NL; P = 0.09).

CONCLUSION

An alteration in the balance of profibrotic and antifibrotic PGs in HF-IPF may play a role in the pathogeneses of IPF.

[Expression and activity of cyclooxygenases-1 and -2 in acetic acid induced gastric ulcer in rats]

OBJECTIVE

To investigate the dynamic changes of the expression and activity of the two forms of cyclooxygenase (COX-1 and COX-2) in animal model of gastric ulcer and their role in the pathological process of gastric ulcer.

METHODS

Acetic acid was perfused into the gastric cavitties of 130 rats to produce animal model of /gastric ulcer. Specimens of the base part and margin of gastric ulcer and normal gastric tissue around were collected 1 hour to 15 days after the induction. RT-PCR and Western blotting were used to detect the expression of COX-1 mRNA and COX-2 mRNA and their protein levels. The total COX activity was determined by determining the ability of tissue homogenate to metabolize arachidonic acid to produce PGE2.

RESULTS

After the ulcer induction, the expression of COX-2 mRNA and its protein were highly induced at the ulcer base in inflammation stage (6 hours to 3 days) and kept at a high level during the healing stage (3 days to 15 days), while the expression of COX-1 remained relatively stable. The homogenates from tissues of basal and marginal parts of ulcer showed very high level of COX activity during the ulcer healing stage. The COX activity of normal tissue around ulcer showed little change before and after ulcer induction.

CONCLUSION

COX, especially COX-2, which maintains a high level of expression and activity during the ulcer healing stage, may play an important role in ulcer healing and tissue remodeling.