Relationship between NF-κB expression and malignancy of canine mammary gland tumor tissues.

In this study, the nuclear expression of nuclear factor kappa B (NF-κB) in 48 tissues specimens from 25 canine spontaneous mammary gland tumor (MGT) patients was assessed by immunohistochemistry to compare their levels with clinical features, histological types, prognostic outcomes and proliferative activities, including the mitotic index (MI) and cylcinD1 expression. Twelve of eighteen (66.7%) malignant tumor tissues showed greater than 10% nuclear staining, while benign tumor and hyperplastic tissues showed less than 10% nuclear staining. Higher nuclear expression of NF-κB was positively correlated with larger tumor size, lymph node metastasis and higher MI; however, no correlation was observed with distant metastasis and cyclin D1 expression. Higher NF-κB nuclear expression correlated with shorter patient survival. These findings suggest that NF-κB is a useful prognostic factor for canine MGT patients.

Effects of NF-κB expression and its inhibition on canine mammary cancer cell lines in an immunodeficient mice model.

Two canine mammary gland tumor (MGT) cell lines, CHMp-5b and -13a, were transplanted into nude mice, and their tumor development and metastatic potential were evaluated. In addition, NF-κB, Ki-67 and cyclin D1 expressions in the tumor masses were evaluated, and the relationship between these expressions and malignancy of the tumors developed in nude mice was investigated. Lower activation of NF-κB was positively correlated with a lower potential of metastasis and better prognosis in nude mice xenografted with CHMp-13a compared with CHMp-5b. Then, CHMp-5b cells were treated with BAY11-7082, an inhibitor of NF-κB, and the expressions of I-κBα, p-I-κBα, cyclin D1 and Bcl-2 in these cells were evaluated by Western blot analysis. In addition, BAY11-7082 at a dose of 6 mg/kg was administered intraperitoneally to nude mice xenografted with CHMp-5b, and relationships between tumor growth and lung and lymph node metastasis in nude mice and NF-κB, I-κBα and p-I-κBα expressions in tissues of these mice were evaluated. BAY11-7082 treatment induced decreased expressions of p-I-κBα, cyclin D1 and Bcl-2 in a dose- and time-dependent manner, suggesting that BAY inhibited NF-κB in this cell line. CHMp-5b-xenografted mice treated with BAY11-7082 showed a reduction in tumor growth and metastasis. Therefore, inhibition of the NF-κB signaling pathway may be a promising novel therapeutic approach for canine MGTs.