Evaluation of the influence of the C-X-C motif chemokine ligand 12 / C-X-C chemokine receptor 4 axis on canine mammary gland tumor cell migration

C-X-C motif chemokine ligand 12 (CXCL12) is one of the chemokines that binds to C-X-C chemokine receptor 4 (CXCR4) on tumor cell membranes and induces chemotaxis and/or migration. Mammary gland tumors (MGT) are the most common neoplasms in intact female dogs, with local invasion and distant metastasis regarded as problems. However, the influence of the CXCL12/CXCR4 axis on canine MGT cell migration has not been elucidated. This study aimed to evaluate the expression of CXCL12 and CXCR4 in canine MGT cells and tissues and investigate the influence of CXCL12 protein on the migratory ability of MGT cells. CXCL12 expression was evaluated in 10 canine malignant MGT tissues. CXCL12 expression in tumor cells was identified in all examined tissues; however, the staining pattern and intensity differed between the tumors. Immunocytochemistry revealed three canine MGT cell lines as CXCR4-positive. Migratory ability was evaluated using a wound healing assay, and the migration of CXCR4-positive MGT cells was significantly activated by the addition of CXCL12 protein. This influence was canceled by pre-treatment with a CXCR4 antagonist. The results of our study suggest that the CXCL12/CXCR4 axis may be associated with the migration of canine MGT.

Antitumor Activities in Mouse Xenograft Models of Canine Fibroblastic Tumor by Defucosylated Mouse-Dog Chimeric Anti-HER2 Monoclonal Antibody (H77Bf)

Human epidermal growth factor receptor 2 (HER2) is a cell surface type I transmembrane glycoprotein that is overexpressed on a variety of solid tumors and transduces the oncogenic signaling upon homo- and heterodimerization with HER families. Anti-HER2 monoclonal antibodies (mAbs) including trastuzumab and its antibody-drug conjugate have been shown to improve patients' survival in HER2-positive breast, gastric, and lung cancers. Canine tumors have advantages as naturally occurring tumor models, and share biological and histological characteristics with human tumors. In this study, we generated a defucosylated version of mouse-dog chimeric anti-HER2 mAb (H77Bf) derived from H₂Mab-77 (mouse IgG₁, kappa). H77Bf possesses the high binding affinity (a dissociation constant: 8.7 × 10^-10 M) for a dog HER2 (dHER2)-expressing canine fibroblastic tumor cell line (A-72). H77Bf exhibited antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity for A-72 cells. Moreover, intraperitoneal administration of H77Bf significantly suppressed the development of A-72 tumor compared with the control dog IgG in a mouse xenograft model. These results indicate that H77Bf exerts antitumor activities against dHER2-expressing canine cancers, which could provide a valuable information for canine cancer treatment.