The effects of cyclooxygenase‐2 inhibition on apoptosis and cell cycle distribution using two in vitro models of nasal squamous cell carcinoma

Objective: Despite numerous attempts using a variety of therapeutic modalities, response rates and survival times for canine nasal squamous cell carcinoma remain poor. The goals of this study are to determine if a COX‐2 selective inhibitor induces apoptosis and alters cell cycle distribution in two in vitro models of nasal squamous cell carcinoma, and to establish a basis for future clinical trials using COX‐2 inhibitors as radiosensitizing agents. Methods: The nasal squamous cell carcinoma cell lines FAT‐7 (rat) and RPMI 2650 (human) were purchased from ATCC (Manassas, VA). Cell pellets were stained for COX‐2 expression using standard immunohistochemical techniques. Following the determination of growth kinetics for each cell line, cells were plated in triplicate using 25 cm² tissue culture flasks and incubated with different concentrations of a COX‐2 selective inhibitor (0, 1, 10, 50 and 100 μM) for 72 hours. Cells were stained with Annexin‐V and propidium iodide (Oncogene Research Products) and analyzed with flow cytometry to assess cell viability. Cell cycle distribution was determined using a propidium iodide methodology and flow cytometric analysis. Results: Preliminary results show that the addition of a COX‐2 selective inhibitor caused a dose‐dependent cytotoxicity on the FAT‐7 cells. Viability at 72 hours ranged from 95.4% for control samples to 7.46% for cells incubated at 100 μM. Changes in cell cycle distribution were also detected. Conclusions: Future study is warranted to determine if the addition of a COX‐2 selective inhibitor will increase response rates and overall survival in a population of spontaneously arising canine nasal squamous cell carcinomas.