of Granulopoietic Factor(s) in the Plasma ofNude Mice Transplanted With a Human Lung Cancer and in the Tumor Tissue

RANULOCYTOSIS without any evidence of infection has been observed in some patients with nonhematologicmalignancies. The precise mechanism ofthis phenomenon, however, remains unexplained in most cases. We investigated a patient with a poorly differentiated squamous cell carcinoma of the lung who developed a mild but persistent neutrophilia. This tumor (OTUK-tumor) was successfully transplanted into nude mice of the BALB/c strain bred under specific pathogen-free conditions.1 These mice developed a marked neutrophilia pan passu with the growth of the transplanted tumor, in marked contrast to those transplanted with other human tumors. The number of peripheral neutrophils returned to normal after removal of the tumor. In view of the known production of various hormones including erythropoietin by human tumors,2 the most plausible explanation for this phenomenon seemed to be the production ofgranulopoietic factor(s) by this tumor. The present studies were designed, therefore, to prove their hypothesis with the in vitro agar culture technique. This technique, involving the formation of granulocyte-macrophage colonies, has been widely applied as a quantitative assay of in vitro granulopoiesis in terms of colony-stimulating activity (CSA).3 The present results indicated that the OTUK-tumor produced granulopoietic