Establishment of Canine Oral Mucosal Melanoma Cell Lines and Their Xenogeneic Animal Models

Canine oral melanoma is the most prevalent malignant tumor in dogs and has a poor prognosis due to its high aggressiveness and high metastasis and recurrence rates. More research is needed into its treatment and to understand its pathogenic factors. In this study, we isolated a canine oral mucosal melanoma (COMM) cell line designated as COMM6605, which has now been stably passaged for more than 100 generations, with a successful monoclonal assay and a cell multiplication time of 22.2 h. G-banded karyotype analysis of the COMM6605 cell line revealed an abnormal chromosome count ranging from 45 to 74, with the identification of a double-armed chromosome as the characteristic marker chromosome of this cell line. The oral intralingual and dorsal subcutaneous implantation models of BALB/c-nu mice were successfully established; Melan-A (MLANA), S100 beta protein (S100β), PNL2, tyrosinase-related protein 1 (TRP1), and tyrosinase-related protein 2 (TRP2) were stably expressed positively in the canine oral tumor sections, tumor cell lines, and tumor sections of tumor-bearing mice. Sublines COMM6605-Luc-EGFP and COMM6605-Cherry were established through lentiviral transfection, with COMM6605-Luc-EGFP co-expressing firefly luciferase (Luc) and enhanced green fluorescent protein (EGFP) and COMM6605-Cherry expressing the Cherry fluorescent protein gene. The COMM6605-Luc-EGFP fluorescent cell subline was injected via the tail vein and caused lung and lymph node metastasis, as detected by mouse live imaging, which can be used as an animal model to simulate the latter steps of hematogenous spread during tumor metastasis. The canine oral melanoma cell line COMM6605 and two sublines isolated and characterized in this study can offer a valuable model for studying mucosal melanoma.