Granulopoiesis and thrombopoiesis in mice bearing transplanted mammary cancer.

Growth of a transplantable mammary cancer in CE mice (CE 1460 MA CA) was paralleled by hyperplasia of the granulocytic elements of the bone marrow and peripheral leukocytosis (up to 350,000 leukocytes/cu mm) with a lymphoid-myeloid ratio re versal to 1:4 and a shift to the left. About 5-20% of the granulo cytic elements in the blood and bone marrow showed morpho logic abnormalities. Hematocrit values decreased 10-15%. Peripheral platelet levels manifested a slight depression in the face of bone marrow megakaryocytopenia and splenic megakaryocytosis. Extramedullary granulopoiesis, with the presence of mitoses and all stages of development of the granulocyte series in diffuse and discrete foci, was observed in the liver, spleen, lungs, lymph nodes, and adrenals of CE 1460 tumor bearers. The development of foci of extramedullary granulopoiesis, despite the absence of métastasesin the bone marrow, suggests that the former resulted from direct stimulation of both intraand extramedullary hemopoietic tissue by a tumor-elaborated, granulocyte-specific factor, rather than from a reduction of bone marrow space available for granulopoiesis. In BALB/C mice, another transplantable mammary cancer (BALB/C 2301 MA CA) induced periodic fluctuation of platelets between base-line and elevated levels and bone marrow megakaryocytosis but no change in splenic megakaryoctye levels. The bone marrow erythroid-myeloid ratio and the peripheral leuko cytes' lymphoid-myeloid ratio remained normal. Hematocrit values decreased 10-15C¿.No foci of extramedullary granulo poiesis developed in the host tissues. The tumor specificity of the leukemoid and thrombocytic re sponses was suggested by the host response to transplantation of the respective tumors into (BALB/C x CE) FI hybrid mice and by the regression of the specific CE 1460 tumor-associated and BALB/C 2301 tumor-associated hématologiechanges following tumor excision.