Effect of retinoids on growth inhibition of two canine melanoma cell lines

Two new canine melanoma cell lines (CMM1 and CMM2) were established from th e patients with oral malignant melanomas. Histopathological type of both CM M1 and CMM2 was a mixed cell type consisted of spindle-shaped cells, polygo nal cells, and oval cells. Doubling time of CMM1 and CMM2 were 18.4 +/- 1.9 6 hr and 21.0 +/- 0.73 hr, respectively. The effect of two kinds of retinoi ds (all-irans retinoic acid and 9-cis retinoic acid) on the proliferation o f these cells were examined by morphological changes, proliferation assay a nd apoptosis assay. However, the retinoids did not suppress growth rate of these cells. This result suggests that retinoids used in this study did not induce differentiation, apoptosis, and growth inhibition of the canine mel anoma cell lines.