Predicting clinical outcome in feline oral squamous cell carcinoma: tumour initiating cells, telomeres and telomerase.

Feline oral squamous cell carcinoma (SCC) has very poor prognosis. Here, a retrospective pilot study was conducted on 20 feline oral SCC patients who underwent stereotactic radiation therapy (SRT), to evaluate: (1) the value of putative tumour initiating cell (TIC) markers of human head and neck SCC (CD44, Bmi-1); (2) telomere length (TL) specifically in putative TICs; and (3) tumour relative telomerase activity (TA). Significant inverse correlations were found between treatment outcomes and Bmi-1 expression, supporting the predictive value of Bmi-1 as a negative prognostic indicator. While TL exhibited a wide range of variability, particularly in very short fractions, many tumours possessed high levels of TA, which correlated with high levels of Bmi-1, Ki67 and EGFR. Taken together, our results imply that Bmi-1 and telomerase may represent novel therapeutic targets in feline oral SCC, as their inhibition - in combination with SRT - would be expected to have beneficial treatment outcome.