Studies on growth and regression of Ehrlich mouse ascites tumor heterotransplants.

Despite its wide use for qualitative as well as quantitative studies on tumor biology, the Ehrlich mouse ascites tumor has rarely been used for studies on the regression of cancer heterotransplants. The absence of stroma in this form of malignant growth should facilitate the quantita tive approach to the analysis of events occurring during the destruction of neoplastic heterotransplants. According to Lewis (14), transplantation of 1 ml. of Ehrlich ascites tumor into the peritoneal cavity of rats resulted within 3-4 days in the formation of 30-50 ml. of thick, milky ascitic fluid containing many viable tumor cells. This fluid be came amber-colored shortly afterward, and only very few malignant cells were identified in the fluid. This was followed by a complete regression of the tumor and résorptionof the ascitic fluid. Ahlströmand Ising (1) reported a decrease in the total number of tumor cells 6 days following inocu lation of 1 ml. of mouse ascites tumor into the peritoneal cavity of rats. The authors observed a marked increase in the size of cancer cells during the first passage of this transplant in rats. Stroud et al. (18) studied the growth characteristics of the Krebs mouse ascites tumor when transplanted serially into rats. Our present report deals with some biological and morphological characteristics of the heterotransplant of Ehrlich mouse ascites tumor in the peritoneal cavity of rats.