Immunohistochemistry and TRAP-ELISA comparative evaluation of telomerase in feline mammary tissues

Telomerase represents a marker for neoplastic tissues, employed as a diagnostic and prognostic tool for use in clinical medicine and in planning new therapies. The aim was to detect telomerase in 13 mammary samples and 2 positive control testes comparing two different methods: immunohistochemistry (to assess the presence of the catalytic subunit by anti-h-TERT MoAb, clone 44F12, Novocastra, diluted 1:50) and TRAP ELISA (a PCR based protocol which utilizes a colorimetric detection method). With TRAP, a cut off limit of 0.2 ΔA was considered discriminant between the 6 negative and 9 positive cases. Immunohistochemistry revealed a specific reaction mainly in nucleoli, at a lesser extent in nuclei and rarely in the cytoplasm of epithelial cells. The stroma showed nucleolar positivity only in two cases. Cut off between positive and negative cases was considered 20% of positive epithelial cells. Pearson correlation between TRAP and immunohistochemistry was significant only when nucleolar+nuclear (9 positive and 6 negative) stain was compared (R=0.69, P=0.009), and not when cytoplasmic stain was considered alone (R=0.31, P=0.3) or together with nucleolar+nuclear (R=0.53, P=0.59) stain. On the basis of these results only immunohistochemical nucleolar plus nuclear stain correlates with the results of TRAP allowing the former to be a method alternative to the latter.