Effect of dacarbazine (DTIC) on cultures from malignant melanoma of the choroid: an immunohistochemical and electron microscopic study.

INTRODUCTION

Dacarbazine (DTIC) is a very effective chemotherapeutic agent used in the treatment of cutaneous melanoma; it also could have a potential therapeutic value as an antimetastatic agent in the treatment of choroidal melanoma.

OBJECTIVE

To study the HMB-45 and S100 protein expression in choroidal melanoma cultures with and without DTIC, and compare the immunohistochemical and electron microscopic changes in both groups.

METHODS

Five- and seven-day cultures of choroidal melanoma (n = 21) were cultivated in diffusion chambers. The cultures were divided in two groups: I group (control group)--the cells were grown in 199-medium; II group--the cells were in 199-medium supplemented with 0.03 mg/ml of DTIC. Immunohistochemical studies were performed with paraffin-embedded material of the cultures by the avidin-biotin-alkaline phosphatase technique. Araldit-embedded material was studied by electron microscopy.

RESULTS

The expression of HMB-45 and S100 protein in the cultures with DTIC ranged from slightly positive to negative. The tumor cells were severely damaged. Electron microscopy in this group showed presence only of cellular fragments. In the DTIC-free group the HMB-45 and S100 expressions were strongly positive. There were no electron microscopic evidence of cellular death.

CONCLUSION

DTIC suppresses the growth of choroidal melanoma in vitro. These results indicate that further studies are warranted to elucidate the effect of DTIC in vivo.