In vitro effects and clinical evaluation of a human chorionic gonadotrophin preparation in acute leukemia

Commercial human chorionic gonadotrophin (HCG) preparations decrease the tumorigenicity of human tumors in immunodeficient mice and induce apoptotic cell death in animal tumor models. Preliminary studies in humans have demonstrated tumor regression in patients with Kaposi's sarcoma given intralesional injections of HCG. To further evaluate HCG's antitumor activity we conducted in vitro and clinical evaluations of HCG in acute myeloid leukemia (AML). In HL-60 leukemic cell lines, a 20-40% inhibition of cell density was demonstrated by trypan blue exclusion method at low concentrations of an HCG preparation (2 x 10(-3)-2 x 10(-2)). Similar concentrations also resulted in a reduction in the proportion of cells in G(2)M phase of the cell cycle, as well as enhanced differentiation compared to control cells. Fifteen patients with advanced AML with marrow blast counts >30%, and five with marrow blast counts between 10 and 26% were given daily subcutaneous injections of HCG 2-4 IU and oral levamisole 50 mg weekly. Five patients with absolute blast counts in the blood ranging from 0 to 3500/mu l and percent blasts in the marrow ranging from 16 to 81% were observed to have no progressive increase in either marrow or peripheral blast counts for 70-121 days. One patient with a pretreatment blast count of 10% in the marrow, no circulating blasts and minor cytopenias had a decrease in marrow blasts to less than 5% which has persisted at 550 days. No significant improvement from baseline levels of neutrophils, hemoglobin or platelets were observed in any of the patients treated. Increases in apoptotic cell death were observed in over 50% of patients' cells with some demonstrating peak levels similar to experiences in patients treated with DNA-damaging chemotherapy. A decreased expression of bcl-2 was seen in the majority of patients ranging from 6 to 62%. These new observations suggest that HCG preparations may inhibit leukemic cell growth through enhancement of cell death mechanisms and could be used in judicious combinations with other approaches. The results confirm the pro-apoptotic effects of HCG preparations reported in patients with Kaposi's sarcoma. Identification of the active component of HCG preparations and further understanding of its growth modulatory action will be important in its development as a clinically useful agent.