Growth and Differentiation of a Human T-Cell Leukemia Cell Line, CCRF-CEM, Grafted in Mice1

The growth of human CCRF-CEM T-cell lymphoblastic leukemia was studied in mice immune deprived by different techniques, and in CD-nu/ nu atli>mie mice. Female CBA/CaJ mice were immune deprived by infant thymectomy, priming with l-/î-i>-arabinofuranosylcytosine(200 mg/kg) 48 h prior to total body irradiation (925 cGy) designated Oara-Cy; or after thymectomy the mice received 925 cGy total body irradiation with marrow reconstitution (4 x HI"nucleated cells), designated «•» HM. Only in mice immune deprived by «-> IIAI. subsequently given a single dose of cyclophosphamide(100 mg/kg) 18-24 h before transplantation of CCRFCEM, was there progressive reproducible engraftment and tumor growth. For mice immune deprived in this manner the tumor engraftment rate was 100 and 80% of tumors achieved >1 cm ' within 46 days. In immunedeprived CBA/CaJ mice, but not CD-nu/nu athymic mice, tumor trans planted to the s.c. site metastasized to paraaortic and axillary nodes. Metastatic spread to lymph nodes was confirmed by immunophenotyping and by karyotyping. In contrast to the CCRF-CEM cells in culture, which expressed cytoplasmic CD3 (T3) but not surface CD3, both s.c. and metastatic CCRF-CEM cells xenografted in mice expressed surface CD3. The CCRF-CEM line was exposed to phorbol-12-myristate 13-acetate in vitro to mimic the apparent differentiation which occurred in the xeno grafted cells, and a similar expression of surface CD3 after treatment was seen. This surface expression of CD3 was accompanied by production of inKN \ for the T-cell receptor a chain and surface expression of the T-cell receptor. Identical T-cell receptor ßand 7 chain gene re arrangements were found for the CCRF-CEM line in vitro and the xenografted cells in vivo, demonstrating that only one clone was present and that differences in immunophenotyping were not the result of clonal selection. These results suggest that host (mouse) hematopoictic factors could affect human leukemic cell differentiation. be propagated only in newborn mice (5), suggesting a possible influence of host immunity. Further immune deprivation of athymic mice enhances successful heterotransplantation of hu man leukemic cells (6), using established cell lines (1, 7). Transplantation to the intracranial site in athymic mice in creases the ability to transplant human lymphomas (8). There are two reports of successful engraftment of human T-cell leukemia (1, 7), using the MOLT-4 line, and in both instances further immune deprivation of athymic mice was necessaryIt has been postulated that T-cell leukemias may be sensitive to natural killer cells (9), and that the decrease in natural killer activity that occurs after irradiation (10) might explain the increased tumor growth (7). Despite the increased rate of engraftment, few data are avail able concerning the uniformity of growth of individual tumors, which would allow such tumors to have utility as preclinical models. The T-cell leukemia, CCRF-CEM, has been used ex tensively for studies of drug metabolism and cytotoxicity in vitro, hence we were interested in developing a reproducible model which would allow extension of these experiments in vivo. CCRF-CEM cells have been grown as xenografts in athymic nude mice (11), although a systematic study of growth characteristics has not been reported. We have xenografted CCRF-CEM cells into immune-deprived mice and have docu mented that the resulting tumors are human by karyotyping, immunophenotyping, and genotyping (using T-cell receptor genes). We report the growth, metastatic characteristics, and the apparent ability of these human cells to differentiate in immune-deprived mice.