Viral etiology of human cancer: a historical perspective

In vitro growth and quantification of early (CD33–/CD38–) myeloid progenitor cells: stem cell factor requirement and effects of previous chemotherapy DARIO FERRERO, CRISTINA CHERASCO, BARBARA ORTOLANO, FULVIA GIARETTA, BENEDETTO BRUNO Divisione di Ematologia dell’Università di Torino, Azienda Ospedaliera "San Giovanni Battista", Turin, Italy Correspondence: Dario Ferrero, M.D., Divisione di Ematologia dell' Università di Torino, Azienda Ospedaliera “San Giovanni Battista”, via Genova 3, 10126 Turin, Italy. Phone: international +39-011-6336728/6335329 – Fax: international +39-011-6963737. Background and Objective. All culture systems exploring the early (pre-CFU) hematopoietic compartment are generally complex, time-consuming and unsuitable for routine application. The aim of our study was to develop a stroma-free culture system to quantify early bone marrow (BM) myeloid progenitor cells. Design and Methods. Low density, progenitor cell enriched BM cells underwent a double cytotoxic treatment with CD38 and CD33 monoclonal antibodies + rabbit complement, which depleted 99% of CFU-GM and BFU-E. Then they were cultured, both in agar and in limiting-dilution liquid culture, in the presence of 5637 cell line supernatant (containing GM-CSF, GCSF and interleukin 1), stem cell factor (SCF) and interleukin 3 (IL3). Results. The largest number (median 14.9 on 1 105 cells) and size (>50,000 cells) of myelomonocytic cell clones from CD33–/CD38– progenitors was reached after 3-4 weeks of liquid culture. SCF, but not IL3, was essential for that growth. The frequency of CD33–/ CD38– progenitors grown in liquid culture was approximately three times greater than the LTC-IC frequency in the same cell suspension. An average 93% of CD33–/CD38– progenitors displayed HLA-DR antigens and 43% generated secondary CFU-GM. In the BM of 9/10 patients, previously exposed to chemotherapy, CD33–/CD38– progenitor frequency was quite low (median 0.9 on 1 105 cells), in spite of normal cellularity and morphology and sustained disease remission. Interpretation and Conclusions. CD33–/CD38– progenitors can be grown and quantified in a stroma-free culture system in a relatively short time. The test can reveal long-lasting, subclinical BM damage induced by chemotherapy and could also be valuable for estimating the amount of early myeloid progenitors for transplantation purposes. ©1999, Ferrata Storti Foundation