Figure 5

Pan-cytokeratin staining of lung and secondary tumor sections. At day 44 following tumor cell transplantation, groups of mice (N = 8–10) were euthanized. Lungs and primary tumor masses were excised from the animals. Tissue was fixed in formalin, paraffin embedded, and sectioned for staining with an antibody against pan-cytokeratin as a marker for 4 T1 cells. The chromogen, DAB, stains brown and was used to detect the presence of anti-pan-cytokeratin antibody binding to tumor cells. Panel B shows a representative anti-pan-cytokeratin stained microscopic lung section from a mouse transplanted with 4 T1 tumor cells. Panels C and D show representative anti-pan-cytokeratin stained microscopic lung sections from two HV-68 infected mice transplanted with 4 T1 tumor cells. Circled regions in Panels C and D indicate areas of increased staining for cytokeratins in infected mice. Pan-cytokeratin staining was also used to identify secondary metastatic tumor masses as being composed of 4 T1 cells. Tumor sections from a representative mock treated mouse (Panel F) and from two representative HV-68 infected mice (Panels G and H) showed similar staining for this tumor marker. It should be noted that due to increased mucus in lung tissues of tumor bearing mice, there was higher background staining as evident by the secondary antibody-only control (Figure5A). This increased background staining was not observed in the control for primary tumors (Figure5E).