Both high and low dose rate x-irradiation of purified marrow stromal cells in vitro have been demonstrated by us to alter the growth of added purified hematopoietic stem cells. Dose rates of 5 or 20 rad/min (low) stabilize some parameters of hematopoiesis significantly better than an equivalent leukemia-cell lethal standardized dose delivered at 200 rad min (high), including: production and release from stromal cells of growth factors including granulocyte-macrophage colony stimulating factor-1 (FM-CSF-1) required for proliferation in agar overlay of committed granulocyte-macrophage progenitor cells (GM-CFUc). However, other parameters of hematopoiesis including cumulative production in liquid overlay of total hemopoietic cells and pluripotential hematopoietic stem cells (CFUs) are equally depressed at both low and high dose rates. These physiologic alterations of stromal cells are independent of proliferative integrity as measured by clonagenic survival of replated cells. The protective effect of low dose rate irradiation is lost by prior in vitro exposure of stromal cells to the chemotherapeutic alkylating agent, L-PAM. We will now determine the mechanism of these non-lethal physiologic effects of irradiation on marrow stromal cells, and the critical dose rate for each detectable biologic effect. Methods will involve continuous bone marrow cultures; preparation of purified stromal and hematopoietic stem cell cultures; identification of the phenotype of stromal cells surviving each irradiation dose; measurement of self-renewal capacity of CFUs; quantitation of levels of synthesis of multipotential cell CSF also known as Interleukin-3 (IL-3) and CSF-1; and study of the kinetics of repair of x-ray damage in these compared to other stromal cell cultures that have been treated prior to irradiation with the aklylating agent, L-Phenylalanine mustard; nitrosyl urea; adriamycin or busulfan in vitro. These studies should: improve understanding of irradiation effects that alter cell to cell interaction; and aid in modification of the sequence of chemotherapy and total body irradiation in drug/x-ray protocols to optimize clinical marrow engraftment and improve survival in bone marrow transplantion.

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National Cancer Institute (NCI)
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Radiation Study Section (RAD)
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University of Massachusetts Medical School Worcester
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FitzGerald, T J; Henault, S; Sakakeeny, M et al. (1990) Expression of transfected recombinant oncogenes increases radiation resistance of clonal hematopoietic and fibroblast cell lines selectively at clinical low dose rate. Radiat Res 122:44-52
Santucci, M A; FitzGerald, T J; Harigaya, K et al. (1990) Gamma-irradiation response of cocultivated bone marrow stromal cell lines of differing intrinsic radiosensitivity. Int J Radiat Oncol Biol Phys 18:1083-92
Anklesaria, P; FitzGerald, T J; Kase, K et al. (1989) Improved hematopoiesis in anemic Sl/Sld mice by splenectomy and therapeutic transplantation of a hematopoietic microenvironment. Blood 74:1144-51
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Ohta, M; Anklesaria, P; Wheaton, M et al. (1989) Retroviral src gene expression in continuous marrow culture increases the self-renewal capacity of multilineage hematopoietic stem cells. Leukemia 3:206-26
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Greenberger, J S; FitzGerald, T J; Anklesaria, P (1989) Recent studies of the hematopoietic microenvironment in long-term bone marrow cultures. Immunol Res 8:226-35
FitzGerald, T J; Henault, S; Santucci, M A et al. (1989) Recombinant murine GM-CSF increases resistance of some factor dependent hematopoietic progenitor cells to low-dose-rate gamma irradiation. Int J Radiat Oncol Biol Phys 17:323-35
FitzGerald, T J; Santucci, M A; Harigaya, K et al. (1988) Radiosensitivity of permanent human bone marrow stromal cell lines: effect of dose rate. Int J Radiat Oncol Biol Phys 15:1153-9
Greenberger, J S; FitzGerald, T J; Klassen, V et al. (1988) Alteration in hematopoietic stem cell seeding and proliferation by both high and low dose rate irradiation of bone marrow stromal cells in vitro. Int J Radiat Oncol Biol Phys 14:85-94

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