Introduction

Non steroidal anti-inflammatory drugs (NSAIDs) have a well-recognised anti-neoplastic action in many human and animal studies. Telomerase is an enzyme which synthesises telomeric DNA, allowing cells to bypass homeostatic mechanisms and to replicate without limit. It has been postulated that NSAIDs may have direct inhibitory effects on telomerase in human malignancies however, to the authors' knowledge, there have been no studies in canine cancer lines to date. The aim of this study was to evaluate the effects of NSAIDs on telomerase activity, cyclo-oxygenase (COX) expression, and cell proliferation in a canine bladder transitional cell carcinoma (TCC) cell line.

Materials and Methods

A canine TCC cell line kindly donated by Purdue University was treated with 4 different concentrations of piroxicam (1.0-160 ug/ml) and meloxicam (0.1-160 ug/ml) based on in vivo serum concentrations and previous studies. Assessment of COX 1 and 2 expression (western blot and RT-PCR), cell proliferation (using haemocytometry) and telomerase activity (TRAP and RT-PCR) were performed at various time points up to 21 days and compared to control cultures incubated with DMSO. ANOVA was performed to determine statistical significance (p<0.05) of changes in cell proliferation and telomerase activity.

Results

Cell Proliferation

Significant reductions in cell growth were seen at 19 days at all NSAID concentrations. Meloxicam 160 µg/ml induced significant reductions in cell growth at all 4 time points (5, 10, 15 and 19 days).

COX Expression

There was no effect on COX-1 protein expression at any of the drug concentrations examined. COX 2 expression measured by quantitative RT-PCR was up-regulated at 160 µg/ml meloxicam and piroxicam at day 7 and at 160 µg/ml meloxicam at day 21.

Telomerase Activity

There was no significant effect on telomerase activity at any of the NSAID concentrations examined.

Conclusion and Clinical Relevance

All concentrations of both the NSAIDs significantly inhibit TCC cell proliferation after 19 days of treatment. Telomerase activity is unaffected which suggests that telomerase suppression is not the mechanism of the NSAIDs anti-proliferative effect. In addition COX expression is not down regulated indicating that the mechanism is also COX independent.

Meloxicam appears to be as effective as piroxicam in suppressing TCC cell growth after 19 days of treatment, however at high concentrations, growth suppression occurs much earlier. Further studies are required to determine the efficacy of meloxicam in the clinical treatment of canine TCC.