SERIAL TRANSPLANTATION OF ADULT T-CELL LEUKEMIA-CELLS INTO SEVERE COMBINED IMMUNODEFICIENT MICE

The precise mechanism of the neoplastic cell growth of adult T cell le ukemia (ATL) still remains unclear. In the present study, we have succ eeded in serial transplantation of ATL cells from a patient into sever e combined immunodeficient (SCID) mice. In this model, we found that o nly a leukemic cell clone from an ATL patient could be successively tr ansplanted into SCID mice, although it was difficult to maintain leuke mic cell clones in vitro, suggesting that the microenvironment provide d by SCID mice is suitable for leukemic cell growth. We could not dete ct human T cell leukemia virus type I (HTLV-I) mRNA or interleukin 2 ( IL-2) mRNA in either the tumor cells growing in mice or the original l eukemic cells. Thus, it appears that neither HTLV-I viral expression n or the IL-2 autocrine mechanism is directly involved in the neoplastic cell growth of fresh ATL cells as well as HTLV-I-infected cell lines, at least in SCID mice. In addition, we could passage frozen cells and obtain a large number of expanded leukemic cells in this model. Such a serial transplantation model, which can avoid the changes in the nat ure of leukemic cells that are frequently observed in in vitro culture , and which can propagate leukemic cell clones, would be very suitable not only to study the mechanism of neoplastic cell growth, but also t o test potential therapeutic agents for ATL.