Growth characteristics of murine B16 melanoma multicellular spheroids: a model for invasion and effects of doxorubicin treatments.

Multicellular spheroids, derived from murine B16 melanoma cells, showed unique growth characteristics: when they reached about 500 microns in diameter, their morphology changed rapidly and they became amoeba-like irregular-shaped aggregates. This morphological characteristic closely resembled that of invasive cancer, and may serve as a model for local invasion. To test the possibility that the changes mentioned above can be inhibited by a drug, spheroids were treated with 0.8 microgram/ml of doxorubicin for one hour and their morphology was observed temporally. Although this concentration of the drug decreased the survival of the melanoma cells in monolayer to about 10(-3), the growth was not delayed nor were the "invasion"-like changes inhibited in the spheroids. We believe this system of multicellular spheroids is a useful model to study the mechanisms of tumour invasion, although doxorubicin could not inhibit "invasion"-like changes in this system.