Evaluation of the chemosensitivity of primary cultured malignant melanoma cells using the collagen gel droplet-embedded culture drug sensitivity test.

Malignant melanoma usually shows resistance to a standard chemotherapy regimen. A useful in vitro method to evaluate individual chemosensitivity is required to select effective anti-cancer drugs. This study aimed to establish in vitro tumor response testing for malignant melanoma. We determined the chemosensitivity of primary cultured melanoma cells using the collagen gel droplet-embedded culture drug sensitivity test (CD-DST). Nineteen tests were carried out for 15 cases of malignant melanoma. Primary cultured melanoma cells in collagen gel droplets were exposed to anti-cancer drugs, including cisplatin, adriamycin, dacarbazine, nimustine and vincristine. After a 7-day incubation in a serum-free medium, living melanoma cells in a collagen droplet were detected by image analysis after staining with Neutral red reagent. In vitro drug exposure conditions were determined to reproduce the value of the plasma area under the time-drug concentration curve in vivo. The rate of evaluation of the primary culture of melanoma cells was 78.9% (15/19 tests). The chemosensitivity of cisplatin, adriamycin, dacarbazine, nimustine and vincristine was 15, 62, 0, 0 and 62%, respectively. Dacarbazine was not suitable for CD-DST due to its prodrug characteristics. The CD-DST method was able to evaluate the chemosensitivity of malignant melanoma to anti-cancer drugs in vitro. This method can also be applied to estimate the efficacy of newly developed anti-cancer drugs in vitro.