Normal Human Marrow Stromal Cells Induce Clonal Growth of Human Malignant T-Lymphoblasts

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1 International Journal of Cell Cloning 3: (1985) Normal Human Marrow Stromal Cells Induce Clonal Growth of Human Malignant T-Lymphoblasts Rafael L. Gallardo, Harinder S. Juneja, Frank H. Gardner, Srinivasan Rajaraman Division of Hematology-Oncology, Department of Internal Medicine and Department of Pathology, University of Texas Medical Branch, Galveston, TX, USA Key Words. Marrow stromal cells - Fibroblast * Leukemia - Lymphoblast * CFU-gm * BFU-e Abstract. The effect of marrow stromal cells (MSC) on the clonal growth of a human malignant T-lyrnphoblast (MTL) cell line was investigated in a bilayer culture system. The MSC consistently stimulated clonal growth of MTL, and no stimulatory humoral factor was present in the medium conditioned by the MSC. These observations and other reports suggest that marrow stromal cells may provide a microenvironment in vivo that is not only conducive to the growth of malignant lymphoblasts, but may actually enhance proliferation of malignant T-lymphoblasts in the bone marrow. Introduction Hematopoiesis in murine and human long-term bone marrow cultures is dependent on the marrow microenvironment [l, 21. When the adherent layers from short-term marrow stromal cell (MSC) cultures are transplanted under the renal capsule, they can transfer the inductive microenvironment for normal hematopoiesis [3]. Interestingly, normal murine marrow hematopoietic cells and human leukemic cells also influence MSC, suggesting that local regulation of hematopoiesis may involve a mutual interaction between hematopoietic stem cells and marrow stromal cells [4, 51. We and others have reported that normal human MSC grown in short-term cultures have potent myeloid colony-stimulating activity (CSA) [6, 71. The MSC from patients with aplastic anemia have a significantly poorer CSA and poorer colony-stimulating factor (CSF)-enhancing activity than that of normal individuals, suggesting that the microenvironment is abnormal in acquired aplastic anemia [7,8]. However, the effect of normal MSC on erythroid colony formation by burstforming unitserythroid (BFU-e) is variable; i.e., some normal human MSC inhibit Correspondence: Harinder S. Juneja, M.D., Room MW404, John Sealy HospitaLE65, Hematology-Oncology Division, University of Texas Medical Branch, Galveston, TX (USA). Received August 1, 1984; accepted March 4, Press, Inc.

2 Gallardo/Juneja/Gardner/Rajaraman 170 BFU-e, while others do not affect their growth [9, lo]. The effect of MSC on the proliferation of human malignant hematopoietic cells has not been studied. We have evaluated the effect of normal human MSC on the clonal growth of human malignant T-lymphoblasts (MTL). Materials and Methods Primary MSC cultures We used the methodology described previously [ll]. Briefly, bone marrow aspirates were obtained from six normal volunteers and bone marrow buffy coat cells were prepared by centrifugation at loo0 X g for 10 minutes. Nucleated buffy coat cells (5 X lo6) were plated in 100 mm Petri dishes (Falcon, Oxnard, CA) in Eagle s minimal essential medium (GIBCO Laboratories, Grand Island, NY) supplemented with 15% fetal calf serum (FCS; Sterile Systems, Logan, UT) and 2 mm L-glutamine. Cultures were incubated at 37 C in a humidified atmosphere of 5% C02 in air, and fed twice a week. MSC were used in experiments when they reached near confluency, usually 3 to 4 weeks after plating. MSC were collected by trypsinization. Malignant Lymphoblast Cultures A T-lymphoblast cell line (CEM), derived from a patient with acute lymphoblastic leukemia, was obtained from the American Type Culture Collection (ATCC CCL 119, Rockville, MD, USA). The CEM cell line was grown in Eagle s supplemented with 10% FCS and 2 MLglutamine at 37 C in a humidified atmosphere of 5% C02 in air. The population doubling time was 24 h. Flow cytometry analysis of these cells showed a diploid DNA content. The cell line was examined by obtaining DNA histograms on a flow cytometer twice during three months. The diploid DNA content of the cells did not change for the duration of these experiments (data not shown). Malignant T-Lymphoblast MSC Co-Culture fiperiments Using a bilayer system, cultures were plated in 24-well tissue culture plates (Falcon, Oxnard, CA) [12]. A 0.5 ml aliquot of 0.45% agar in Eagle s was layered to prevent the MSC from adhering to the bottom of the wells. The second layer consisted of 0.75 ml of 0.3% agar in Eagle s supplemented with 20% FCS, containing 5 X lo3 MTL mixed with one of several concentrations of MSC (1 x 104 to 20 x 104 per ml). The plates were evaluated for clusters/colonies on days 1 through 14. Aggregates (<40 cells) began appearing by day 7 and colonies ( 240 cells) were present on days 10 through 14. All colony counts reported here were conducted on day 14. In four experiments, a dose-response curve was obtained by co-culturing a varying number of MTL (500 to lo,ooo/well) with a fixed number (1 x los) of MSC. Effect of MSC-Conditioned Medium on MTL The medium conditioned for 4 days by near confluent MSC cultures was collected and used as MSC-conditioned medium (MSC-CM). The MSC-CM was centrifuged at lo00 X g for 10 min, filtered through a 0.45 fi Millipore filter, and stored at -20 C. The media was concentrated tenfold using an Amicon ultra concentrator. A membrane that excluded

3 Strornal Cells Induce Growth of Lyrnphoblasts 171 substances with a molecular weight of < 10,000daltons was used. This procedure was used to exclude possible small molecular weight inhibitors ( < l0,ooo daltons). The concentrated media was dialyzed against 100 X volume of Eagle's for 48 h at 4"C, with a change of the dialyzing medium at 24 h. The initial and tenfold concentrated and dialyzed MSC-conditioned medium were tested by adding 2.5%, 5%, lo%, 20%, and 30% (v/v) of each to the single-layer agar culture (0.3%) containing 5 X lo3 MTL. To determine if the MSC- CM contained a factor that stimulated MTL to release an autocnne factor, 1 X lo6 MTL/ml were incubated in diluted and tenfold concentrated MSC-CM for 24 h; the resultant conditioned medium was tested for its ability to stimulate MTL colony formation at lo%, 20%, and 30% (vlv). Characterization of h47l Cells in Co-Culture Experiments and Liquid Culture MTL colonies collected with a Pasteur pipet were blown on a glass slide and Wright- Giemsa stained. The morphology of the cells in the colonies was similar to that of the MTL cells grown in liquid culture. In three representative experiments, cytocentrifuge preparations were prepared from the MTL cells in liquid cultures and the cells composing the colonies in the co-cultures. The cytospin preparations were air dried for 60 min, fixed for 60 i n, fixed with cold (4 C) acetone for 10 min, and washed in phosphate-buffered saline (ph 7.6) for 5 min. The cells were stained by Avidin-Biotin-Peroxidase-complex method of Hsu et al. [13]. The following antibodies were used: OKT 11, OKT 4A, OKT 3 (Ortho Diagnostic Systems, Inc., Raritan, NJ), and Leu 14 (Becton Dickinson Monoclonal Center, Inc., Mountainview, CA). The concentration used for each monoclonal antibody gave optimal labelling and minimal background staining (1 to 10 pgglml). Appropriate controls were run concurrently. Results The MSC grown in our laboratory have a fibroblastic morphology; immunofluorescence studies with specific antibodies to various types of collagen show the MSC are positive for collagens type I and III and negative for type IV [7]. These fibroblastic cells wre alkaline phosphatase positive. As determined by nonspecific esterase stains, the percentage of macrophages in the primary MSC cultures used in this study was 0% to 0.1 %. MSC grown in other laboratories have similar characteristics [14]. On immunocytochemical studies, both the MTL in liquid cultures and the cells from the colonies in co-cultures with MSC gave positive reactions with OKT 11, OKT 4A, and OKT 3 and gave a negative reaction with Leu 14. These results indicate that the colonies seen in the co-culture studies were MTL colonies. All six normal MSC stimulated MTL colonies in a dose-dependent manner. The co-culture of MCS with MTL stimulated the formation of MTL colonies in 5 experiments, while in the control cultures no MTL colonies were formed in the absence of the MSC (Fig. 1,2). The optimal concentration of MSC was 1 X 10s/ml

4 Colonies / 5 X 103 MTL

5 Stromal Cells Induce Growth of Lymphoblasts 173 in 4 experiments and 2 x 105/ml in 1 experiment. In one experiment in which MTL colonies were formed spontaneously in the absence of MSC, the presence of MSC further enhanced colony formation by MTL in a dose-dependent manner. The optimal concentration of MSC in this experiment was 1 X 105/ml. When a dose-response curve was prepared for experiments with a varying number of MTL (500-10,000/ml) and a fixed number of MSC (i.e. 1 x 105/ml), the number of MTL colonies and the number of MTL plated were linearly correlated (R = , P =.001). MSC-CM, diluted or concentrated and dialyzed, failed to stimulate MTL colony formation at several concentrations tested. The MSC-CM failed to induce the MTL to produce autocrine factors. Discussion Marrow stromal cells grown in short-term cultures support proliferation of human granulocyte/macrophage colony-forming units [6-81. Our results indicate that normal human MSC also induce clonal growth of malignant human hematopoietic cells. The induction of MTL colony formation by MSC is demonstrated with subclones capable of spontaneous colony formation as well as those lacking the capacity for spontaneous clonal growth in semisolid medium. The means by which MSC stimulate MTL colony formation is not clear. We were unable to demonstrate any stimulatory humoral factor in the MSC- CM. The absence of MTL colony-stimulating activity in the MSC-CM may be the result of a rapid utilization or degradation of such activity by proteases, and therefore the presence of a humoral factor cannot be totally excluded. Dialysis of the concentrated medium prior to use in experiments excludes the presence of low molecular weight inhibitors ( < l0,ooo daltons); however, the presence of high molecular weight inhibitors cannot be ruled out. Interestingly, we and other investigators have reported that MSC exhibit myeloid CSA. In those studies, CSA was not detected in the MSC-CM [6, 7,9]. Thus, we speculate that a close cell-to-cell interaction or a short-range factor may be responsible for the growth-stiniulatory activity of the MSC. Even though the production of myeloid CSA by endothelial cells and fibroblasts is regulated by a stimulatory monokine [15, 161, no such interaction was possible in our experiments because few to no monocytes were present in our system. Our data also suggests that the MSC do not produce any humoral factor capable of inducing MTL to produce autocrine factors. Fibroblastic cells of human and murine fetal origins also share with human MSC the capability to support growth and differentiation of normal hematopoietic stem cells [13, 171. The ability of normal MSC to support the growth of MTL suggests that the MSC may play a role in the in vivo growth of malignant lymphoblasts.

6 Gallardo/Juneja/Gardner/Rajaraman 174 This is supported by a brief report of human MSC being essential in the propagation of a cell line of malignant lymphomatous tissue obtained from a child [18] and by a similar report on the rnurine system [19]. Even though the exact nature of the interaction between MSC and the malignant T-lymphoblasts is not clear, our findings indicate that MSC may provide an in vivo microenvironment that not only supports but actively promotes proliferation of malignant lymphoblasts in the bone marrow. Acknowledgments The excellent technical assistance of Mr. Sang Lee and Mrs. Mairryee Sahu is greatly appreciated. We thank Dr. J.A. Hokanson of the biostatics division of the UTMB Cancer Center for help with the statistical analysis of the data and Ms. Eva Morgan for help in preparing this manuscript. References Dexter TM, Allen TD, Lajtha L,G. Conditions controlling the proliferation of haemopoietic stem cells in vitro. J Cell Physiol 1977;91: Gartner S, Kaplan HS. Long-term culture of human bone marrow cells. Proc Natl Acad Sci USA 1980; Freidenstein AT, Chailakhyan RK, Latsinik NV, Panasyuk AF, Keiliss-Borok IV. Stromal cells responsible for transferring the microenvironment of the hemopoietic tissues. Cloning in vitro and retransplantation in vivo. Transplantation 1974;17: Gurevich OA, Drize NI, Udalov GA, Chertkov IL. Effect of hematopoiesis on bone marrow stromal precursor cells. Bull Exp Biol Med (Trans]) 1983;95: Nagao T, Yamauchi K, Komatsuda M, Noguchi K, Shimizu M, Yonekura S, Nozaki H. Inhibition of human bone marrow fibroblast colony formation by leukemic cells. Blood 1983;62: Greenberg BR, Wilson FD, Woo L. Granulopoietic effects of human bone marrow fibroblastic cells and abnormalities in the "granulopoietic microenvironment." Blood 1981;58: Juneja HS, Lee S, Gardner FH. Functionally abnormal marrow fibroblasts in aplastic anemia. Exp Hematol 1985;13: Gordon MY, Gordon-Smith EC. Bone marrow fibroblast function in relation to granulopoiesis in aplastic anemia. Br J Haematol 1983;53: Gordon MY, Kearney L, Hibbin JA. Effects of human marrow stromal cells on proliferation by human granulocytic (GM-CFC), erythroid (BFU-E) and mixed (mix- CFC) colony forming cells. Br J Haematol 1983;53: Juneja HS, Lee S, Garcia J, Gardner FH. Effects of normal human marrow stromal cells on erythroid colony formation by burst forming units. Exp Hematol 1983;ll (suppl 14): 31. Juneja HS, Gardner FH, Minguell JJ, Helmer RE. Abnormal marrow fibroblasts in aplastic anemia. Exp Hematol 1984;12 (2):

7 Stromal Cells Induce Growth of Lymphoblasts 175 Hoch S, Schur PH, Schwaber J. Improved method for cloning human B-Cell lines. Cell Immunol 1982;72: Hsu SM, Raine L, Fanger H. A comparative study of the peroxidase-antiperoxidase method and avidin-biotin complex method for studying polypeptide hormones with radioimmunoassay antibodies. Am J Clin Path ;75: Castro-Malaspina H, Gay RE, Resnick G. et al. Characterization of human bone marrow fibroblast colony-forming cells (CFU-F) and their progeny. Blood 1980;56: Bagby GC Jr, McCall E, Bergstrom KA, Burger D. A monokine regulates colony-stimdating activity production by vascular endothelial cells. Blood 1983;62: Bagby GC, McCall E, Layman DL: Regulation of colony-stimulating activity production. Interactions of fibroblasts, mononuclear phagocytes, and lactoferrin. J Clin Invest 1983;71: Lowenburg BS, Dicke KA. Induction of proliferation of haemopoietic stem cells in culture. Exp Hematol 1977;5: Seshadri R, Matthews C, Gardiakos C, Morley AA. The effect of bone marrow feeder cells on the cloning of childhood Non-Hodgkin s lymphoma cells [Abstract]. Int J Cell Cloning 1983;1:311. Zipori D. In vitro proliferation of mouse lymphoblastoid cell lines: g& modulation by various populations of adherent cells. Tissue Kinet 1980;13:28%298.