Intramedullary Influences on in Vitro Granulopoiesis in Human Acute Myeloid Leukemia

Summary

Provision of granulocyte-monocyte colony stimulating activity by human bone marrow (CSA_BM) was determined in 21 patients with acute myeloid leukemia (AML) utilizing in vitro culture techniques to assess intramedullary cellular interactions on human granulopoiesis. CSA_BM production of these patients was compared to that from normal marrow by testing the capacity of conditioned mediums from adherent marrow cells to promote granulocytemonocyte colony formation in agar of relatively light density nonadherent human marrow target cells.

Morphologic, cytochemical, density and phagocytic characteristics of normal marrow cells suggested that CSA_BM production was provided by mid-density adherent cells including those of the monocyte-macrophage series. Significantly decreased CSA_BM provision was found in 62% of patients with AML at diagnosis or relapse. Only 33% of these patients entered chemotherapy-induced complete remission, in contrast to an 88% remission rate in the patients with normal CSA_BM. Sequential studies in 9 patients during complete remission showed normal or increased CSA_BM, which generally decreased concomitant with relapse. These findings suggest that adequate CSA_BM provision may be essential for sustaining normal granulopoiesis in AML and may reflect persistence of a normal marrow monocyte-macrophage population. Monitoring this parameter appears useful for evaluating microenvironmental influences on granulopoiesis and assessing prognosis in AML.

Microenvironmental influences within bone marrow and spleen have been shown to be critical for hemopoietic stem cell proliferation and differentiation in experimental animals (McCulloch, Siminovich et al., 1965; Trentin, 1971; Gallagher, McGarry et al., 1971; Knospe and Crosby, 1971; Chamberlin, Barone et al., 1974; Matioli and Rife, 1976; Cline, LeFevre et al., 1977). Histologic and functional studies by these investigators have demonstrated that locally active cell-derived factors provide stromal influences contributing to the support of hemopoiesis.

In vitro marrow culture techniques have permitted analysis of factors involved in the regulation of granulopoiesis by evaluating the ability of granulocytic progenitor cells (CFU-C) to form granulocyte-macrophage colonies in agar under the necessary influence of the humoral stimulatory substance termed colony stimulating activity (CSA) (Rickard, Shadduck et al., 1970; Metcalf, 1973). Human marrow cells require cellular sources of CSA for their in vitro proliferation, whereas murine marrow is stimulated as well by CSA present in serum and urine (Foster, Metcalf et al., 1968; Metcalf and Stanley, 1969; Pike and Robinson, 1970; Metcalf and Moore, 1975). Recent studies in mice have shown that marrow CFU-C proliferation is related predominantly to intramedullary CSA elaboration by cells firmly adherent to the inner surfact of hemopoietic bone (Chan and Metcalf, 1972; Chan and Metcalf, 1973). Thus, local production of CSA within the marrow plays a major role in influencing granulopoiesis.

Cellular sources of CSA are also present within human marrow and can be selectively harvested by their adherence and density characteristics (Haskill, McKnight et al., 1972; Messner, Till et al., 1973; Moore, Williams et al., 1973; Senn, Messner et al., 1974). We have employed these physical separation techniques to evaluate marrow cell-derived CSA levels in normal subjects and patients with acute myeloid leukemia (AML) in order to determine the possible role of human marrow CSA provision as a microenvironmental stimulus for granulopoiesis.

Portions of this paper have been published in the Cold Spring Harbor Conference on Cell Proliferation Volume 5. Differentiation of Normal and Neoplastic Hematopoietic Cells. P. Greenberg and B. Mara, pp. 405–409, 1978.