Growth dynamics of multicell spheroids from three murine tumors.

The growth of multicell spheroids from three murine tumors was characterized and compared. Multicell spheroids displayed growth kinetic patterns similar to those reported for certain types of solid tumors. Growth was exponential initially but decreased in rate as the spheroids increased in size and eventually approached a horizontal asymptote. Further, multicell spheroids from the different tumors exhibited different rates of growth, in agreement with in vivo growth kinetic data. Radioautographic data revealed that the proliferating cells in actively growing spheroids were only present in an outer shell and that the thickness of this "proliferating shell" varied among the three types, suggesting at least one possible basis for the difference in growth rates.