Human myelopoiesis in culture of liquid medium lacking colony stimulating factors: therapeutic implications for cancer patients with leukopenia.

Patients with cancer often develop leukopenia caused by chemotherapy. Since their treatment with human colony stimulating factors (CSFs) has limitations, it is imperative to determine if CSFs are essential in regulating human myelopoiesis. For this purpose, human primary precursor myeloid cells were cultured in media lacking exogenous human CSFs and stem cell factor (SCF), and supplemented with human sera, or with fetal bovine or other types of animal sera. Cells cultured in human sera survive well, proliferate actively, and differentiate toward granulocytes. Most cells cultured in fetal bovine serum die, few differentiate toward monocytes-macrophages. Cells cultured in other types of animal sera die rapidly. Antibodies neutralizing human serum's CSFs and SCF do not abolish its myeloregulatory activity. It is concluded that cell growth factors other than CSFs and SCF present in human serum regulate human myelopoiesis in vitro. These findings bear important therapeutic implication for patients with cancer having leukopenia.