Transferrin receptor expression in canine lymphoma.

Transferrin receptor 1 (TfR1) expression was measured by immunohistochemistry in 78 archived cases of canine B-cell and T-cell lymphoma with an anti-human TfR1 monoclonal antibody that was validated in the dog by immunohistochemistry and immunoblotting. The canine lymphoma cases were initially classified on the basis of World Health Organization criteria and then subdivided into the following 4 subgroups: low-grade B-cell (LGB), high-grade B-cell (HGB), low-grade T-cell (LGT), and high-grade T-cell (HGT). A visual scoring system and densitometric analysis of the proportion and intensity of positive staining were used to quantify TfR1 expression. TfR1 expression was also correlated to mitotic rate. TfR1 expression was significantly lower in the LGT tumors compared to all other lymphoma subgroups (LGB, HGB, and HGT). LGB tumors showed a TfR1 expression similar to those of the high-grade tumors (HGB and HGT). Significant correlations were found between mitotic rate and densitometric TfR1 variables in the T-cell tumors but not in the B-cell tumors. Further studies are needed to investigate the underlying molecular basis of the high TfR1 expression in LGB lymphomas and its pathological relevance. The anti-human TfR1 monoclonal antibody is a useful tool for measurement of total cellular transferrin receptor expression in the dog; however, an antibody with specificity for the canine TfR1 ectodomain is needed to investigate the potential of this receptor as an oncolytic target.