Further purification of a CFU-S inhibitor: in vivo effects after cytosine arabinoside treatment.

This paper describes a large scale extraction procedure which allows the preparation of a stable CFU-S inhibitor from fetal calf bone marrow. The use of BioGel P-2 gels results in an increase of the specific activity of the inhibitor as well as in the yield of the preparation. When injected into mice, the inhibitory fraction (Ve/Vo 1.17-1.8) prevent CFU-S entry into cycle after cytosine arabinoside at a dose of 4 micrograms per mouse. When administered during lethal protocols of Ara-C treatment, it significantly increases the percentage of surviving animals. Thus, this low molecular weight factor (below 2,000 D), devoid of species-specificity, enhances the tolerance of animals to high doses of chemotherapy and might be of interest in cancer treatment.