A SOLUBLE‐FACTOR(S) SECRETED BY A HUMAN SKIN CANCER CELL LINE SUPPORTS CLONAL GROWTH OF ADULT T‐CELL LEUKEMIA CELLS

Leukemic cells from four out of eight patients with adult T‐cell leukemia (ATL) were successfully grown by cocultivation with HSC‐I cells, a human skin cancer cell line, in the presence of interleukin‐2. Three of these four cultures of growing cells showed rearrangement of the T‐cell receptor β‐chain gene like the original leukemic cells in vivo, and also showed conservation of the patterns of HTLV‐I integration of the original leukemic cells in vivo. Cell‐to‐cell contact between HSC‐I cells and leukemic cells was not necessary for growth of the leukemic cells. The results indicate that some soluble growth factor secreted by HSC‐I cells and interleukin‐2 are required for the in vitro growth of leukemic cells from some patients with adult T‐cell leukemia.