STIMULATION OF TUMOR CELL GROWTH BY A SUBSTANCE PRODUCED BY NORMAL AND TUMOR CELLS

It has been shown that a dialyzable substance produced by normal and tumor cells can stimulate the growth of a myeloid, erythroid, and two lymphoid leukemias, and a sarcoma. The growth stimulation of the tumor cells was observed as an increase in cloning efficiency and number of cells per colony. Rat granulocytes stimulated the growth of mouse tumor cells as efficiently as a variety of mouse cells. The stimulating substance was found in conditioned medium, and it was produced by all the normal and tumor cells tested. Copyright © 1969 Wiley‐Liss, Inc.