Thermochemotherapy for malignant melanoma: overcoming heterogeneity in drug sensitivity

Endo B (melanotic) and W (amelanotic) human malignant melanomas originated from the same tumor, both known to be heterogeneous in drug sensitivity to ACNU [( 1-(4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitroso- urea hydrochloride]), were treated experimentally with a combination therapy of ACNU and hyperthermia in mice. Whereas Endo W melanoma has no sensitivity, Endo B melanoma is sensitive to ACNU alone. However, in both types of melanomas, a marked synergistic effect of the combination therapy was noted. Histologically, marked degeneration of both tumor cells was detected. These results strongly suggest that thermochemotherapy may overcome the tumor heterogeneity in drug sensitivity.