REGENERATING HEMATOPOIETIC-TISSUE AS A SOURCE OF A LOW-MOLECULAR-WEIGHT FACTOR THAT INHIBITS PROLIFERATION OF LEUKEMIA-CELLS

A low-molecular-weight leukemia cell proliferation-inhibiting factor ( LCPIF) was isolated by chromatography from an aqueous extract of regen erating hemopoietic tissue. LCPIF was approximately 1000-fold more eff ective in inhibiting DNA synthesis in leukemia cells than the initial extract. This activity did not change upon treatment with proteinase K but was strongly inhibited by sequential treatment with endo-alpha-N- acetylgalactosaminidase and proteinase K. LCPIF was identified as a gl ycoprotein of molecular weight less than 3 kD.