Enhanced Polymer One-step Staining for Proliferating Cell Nuclear Antigen (EPOS-PCNA) in NR-S1 Tumors of Mouse Tongues. Comparison with the PCNA and Bromodeoxyuridine (BrdU) Immunohistochemistry.

Enhanced polymer one-step staining for proliferating cell nuclear antigen (EPOS-PCNA) consists of monoclonal mouse anti-PCNA and horseradish peroxidase coupled to an inert polymer backbone. This reagent was developed to shorten immunostaining time. In order to clarify the characteristics of this new immunohistochemical reagent, we applied this reagent to the formalin-fixed, paraffin-embedded NR-S1 tumors of mouse tongues, and the staining results were compared with those from conventional PCNA and BrdU immunostaining. Positive reaction for EPOS-PCNA was observed to be granular or diffuse in the tumor cell nuclei. These positive cells were scattered in the NR-S1 tumor. The distribution and staining patterns of EPOS-PCNA were similar to those of PCNA. Their labeling indices (Lls) were also similar, although the Lls in EPOS-PCNA were higher than those in BrdU. We conclude that EPOS-PCNA is a simple, timesaving, and reliable method for assessing cell kinetics of tumor tissues.