Increased expression of COX-2 and pancytokeratin in the bones of arthritic mice challenged with 4T1 cells. Bone sections from various experimental groups (indicated in the Figure) stained for COX-2 (a to f) and pancytokeratin (g to l). Brown staining represents positive staining. All images taken at 200 × magnification. (m to s) Representative Faxitron x-ray images of bones. (m) Balb/c + TUBO; (n) Balb/c + 4T1; (o) Balb/c + Zymosan + 4T1; (p) SKG + TUBO; (q) SKG + Zymosan + Tubo; (r) SKG + 4T1 (showing small radiolucencies in distal femur, proximal tibia, and head of humerus indicating apparent osteolytic bone lesions); (s) SKG + Zymosan A + 4T1 (showing radiolucencies in the distal femur, proximal tibia and head of humerus possibly due to osteolytic bone lesion). Six to seven mice from each group were examined using the faxitron x-ray. No lytic or sclerotic lesions were observed in any other experimental group. (t) Percentage of mice that developed bone metastasis.