Effect of Tolfenamic Acid on Canine Cancer Cell Proliferation, Specificity Protein (Sp) Transcription Factors, and Sp-Regulated Proteins in Canine Osteosarcoma, Mammary Carcinoma, and Melanoma Cells

Background Tolfenamic acid (TA) is an NSAID currently under investigation as an anticancer agent in humans. TA induces proteosome-dependent degradation of transcription factors Sp 1, 3, and 4. These proteins are known to be overexpressed in many human cancers. Hypothesis To evaluate the protein expression of Sps in canine tissue, and efficacy of TA against several canine tumor cell lines. Methods Six canine cell lines (2 osteosarcoma, 2 mammary carcinoma, 2 melanoma) were evaluated. Protein levels of Sp 14 and their downstream targets were evaluated using Western Blots. Cell survival and TUNEL assays were performed on cell lines, and Sp1 expression was evaluated on histologic samples from archived canine cases. Animals Six immortalized canine cancer cell lines derived from dogs were used. Archived tissue samples were also used. Results Sps were highly expressed in all 6 cell lines and variably expressed in histologic tissues. TA decreased expression of Sps 14 in all cell lines. All of the downstream targets of Sps were inhibited in the cell lines. Variable Sp1 expression was identified in all histologic samples examined. TA significantly inhibited cell survival in all cell lines in a dose dependant fashion. The number of cells undergoing apoptosis was significantly increased (P < .05) in all cell lines after exposure to TA in a dose-dependent fashion. Conclusions, and Clinical Importance Tolfenamic acid is a potential anticancer NSAID and further investigation is needed to determine its usefulness in a clinical setting.