Quantitative studies of the growth response of the Krebs ascites tumor.

Abstract

Growth of the Krebs-2 ascites tumor of mice has been quantitated by estimating the volume of ascites by dye dilution and the concentration of tumor cells from total and differential cell counts. Tumor development has been shown to consist of an initial phase of rapid cell multiplication with little or no lag (doubling time, ca. 16 hours) followed by a period of slowed growth toward an asymptote. The course and rate of tumor growth are similar for inocula of 106 to 20 × 106 cells. Growth appears to be more nearly exponential when the number of tumor cells is comparatively small. With increasing cell numbers, the growth rate gradually declines. An exponential fit may be applied from 106 to 2 × 108 tumor cells, and a cube root transformation is applicable with cell numbers from 107 to 4 × 108. Neither expression accounts for the entire growth pattern, which, however, appears to be a function mainly of the total number of free tumor cells. Ascitic volume increases linearly with tumor cell number and exponentially with body weight. However, prediction from weight to ascites to cells is not suitable for quantitative evaluation of the growth curve owing to the large error of estimate. The body weight change is a complex function of tumor growth, reflecting not only the ascites but also the associated anasarca and wasting. Differences in survival time with varying inoculum size may be considerably in excess of the time required for attainment of equivalent cell numbers. The results are discussed in connection with related observations on the growth of the Ehrlich ascites tumor.