INHIBITION OF TUMOR-GROWTH BY ELIMINATION OF GRANULOCYTES

As observed for many types of cancers, heritable variants of ultraviol et light-induced tumors often grow more aggressively than the parental tumors. The aggressive growth of some variants is due to the loss of a T cell-recognized tumor specific antigen; however, other variants re tain such antigens. We have analyzed an antigen retention variant and found that the variant tumor cells grow at the same rate as the parent al tumor cells in vitro, but grew more rapidly than the parental cells in the T cell-deficient host. The growth of the variant cells was sti mulated in vitro by factors released from tumor-induced leukocytes and by several defined growth factors. In addition, the variant cancer ce lls actually attracted more leukocytes in vitro than the parental cell s. Furthermore, elimination of granulocytes in vivo in nude mice by a specific antigranulocyte antibody inhibited the growth of the variant cancer; indicating that this tumor requires granulocytes for rapid gro wth.