Local and metastatic growth and in vivo differentiation of human myeloid leukemia cells transplanted in nude mice.

Cells from the established human myeloid cell lines KG-1, KG-1a, and HL-60, transplanted subcutaneously (sc) into nude mice, developed discrete tumors (myelosarcomas). These myelosarcomas had a host's age-associated pattern of growth identical to that of experimental tumors produced by sc transplantation of cells derived from malignant solid neoplasias. Thus, leukemia cells yielded either localized myelosarcomas at the site of inoculation or a disseminated neoplastic growth after inoculation in adult (more than 4 weeks old) or newborn (1-3 days old) nude mice, respectively. Human myeloid leukemia cells proliferating in the nude mice preserved the human karyotype and a surface antigenic determinant and did not influence the hematopoietic tissues of the host. The KG-1 and HL-60 cell lines consistently attained varying degrees of differentiation along the myeloid series in vitro, and these features were maintained during proliferation in the mice. Furthermore, cells of the variant subline KG-1a, which had a blastic morphology, developed signs of differentiation that were not seen in culture. The presence of readily identifiable markers, such as cytoplasmic granules containing myeloperoxidase, in the cell lines tested makes these models particularly useful for studying the influence of a biological environment on cell differentiation and its influence on tumor growth. These experimental systems are also suitable for investigating the mechanism(s) of metastases and for in vivo experimental therapeutic trials.