Steroid hormone receptors and the differentiation of myeloid leukemic cells

The effect of steroid on myeloid leukemic cells: The potential of short-course high-dose methylprednisolone treatment in inducing differentiation, apoptosis and in stimulating myelopoiesis

Several in vitro studies have shown that dexamethasone (Dex) and prednisolone can induce differentiation of some mouse and human myeloid leukemic cells to macrophages and granulocytes. Based on in vitro experiments, we have shown that short-course (3-7 days) high-dose methylprednisolone (HDMP) (20-30 mg/kg/day) treatment can induce differentiation of myeloid leukemic cells in vivo in children with different subtypes of acute myeloblastic leukemia (AML) (AML-M1, -M2, -M3, -M4, -M7). We have also shown that induction of apoptosis of myeloid leukemic cells with or without differentiation is possible by short-course HDMP treatment. In addition, short-course HDMP treatment has been shown to be effective in accelerating leukocyte recovery, possibly stimulating normal CD34-positive hematopoietic progenitor cells. Addition of HDMP to mild cytotoxic chemotherapy (low-dose cytosine arabinoside (LD-Ara-c), weekly mitoxantrone and Ara-c or 6-thioguanine) increased the remission rate (87-89%) and improved the outcome of AML children. We believe that the results of our 17-year clinical experience will provide important benefits to AML patients.

Myeloprotective effect of short-course high-dose methylprednisolone treatment before consolidation therapy in children with acute myeloblastic leukemia

In our previous studies, short-course high-dose methylprednisolone (HDMP) has been shown to shorten the chemotherapy-induced neutropenic period by stimulating the CD34(+) hematopoietic progenitor cells in children with acute leukemia. In this study, we investigate the role of short-course HDMP on induction of a myeloprotective effect when administered before consolidation therapy consisting of high-dose cytosine arabinoside and daunorubicin. Thirty-four consecutive newly diagnosed children with acute myeloblastic leukemia (AML) who received 64 courses of consolidation regimen were entered into the study. The patients received HDMP (group A) at a daily dose of 30 mg/kg methylprednisolone starting 4 days before the initiation of consolidation therapy. The control group did not receive HDMP (group B). There were no differences in the white blood cell (WBC) and absolute neutrophil counts (ANC) between group A (at day -4) and group B (at day 0) at the beginning of the study (medians: 3 x 10(9)/L vs. 3.2 x 10(9)/L and 1.5 x 10(9)/L vs. 1.7 x 10(9)/L, respectively). The WBC count increased significantly from 3 x 10(9)/L to 6.4 x 10(9)/L, and ANC increased from 1.5 x 10(9)/L to 3.9 x 10(9)/L after 4 days of HDMP treatment in group A (P < 0.01). Following high-dose chemotherapy, the median values of WBC and ANC also remained higher than the control values during the 16 days of the follow-up period. The neutropenic period was significantly shorter in the HDMP group than in the control group (9 +/- 5.2 days vs. 22 +/- 4.7 days) (P < 0.05). The duration of hospitalization and the interval between two chemotherapy cycles were significantly decreased in group A when compared group B (9 +/- 2.7 vs. 14 +/- 2.7 days; 22 +/- 4.7 vs. 26 +/- 4.2 days, respectively) (P < 0.05). Moreover, following consolidation therapy, the number of patients with ANC values below 0.5 x 10(9)/L was lower in group A when compared the group B. In conclusion, the administration of short-course (4 days) HDMP before high-dose chemotherapy has been found to be beneficial for reducing the duration and severity of neutropenia. Further studies with short-course HDMP are required to evaluate its myeloprotective effects in patients with other malignancies.

Glucocorticoids have pleiotropic effects on small intestinal crypt cells

Glucocorticoids have long been known to accelerate maturation of the intestinal tract, but the molecular mechanisms that account for their physiological function in the epithelium remain poorly characterized. Using rat intestinal epithelial cell lines (IEC-6, IEC-17, and IEC-18) as models, we have characterized glucocorticoid receptors in crypt cells and documented striking morphological, ultrastructural, and functional alterations induced by these hormones in intestinal cells. They include arrest of growth, formation of tight junctions, appearance of long, slender microvilli, reorganization of the endoplasmic reticulum and trans-Golgi network, and downregulation of the cell cycle regulatory proteins cyclin-dependent kinase 6 and p27(Kip1). These effects are consistent with the activation or modulation of multiple genes important in the physiological function of absorptive villous cells but are probably not directly involved in the induction of cell differentiation.

Morphologic evidence of apoptosis in childhood acute myeloblastic leukemia treated with high-dose methylprednisolone

We have previously demonstrated that various subtypes of AML children respond to high-dose methylprednisolone (HDMP; 20-30 mg/kg/day) which could induce in vivo differentiation of myeloid leukemic cells to mature granulocytes. In this study we have evaluated whether apoptosis occurs in AML cells of patients treated by HDMP using morphological criteria. For light and electron microscopic examination bone marrow aspirates were obtained four days and two weeks after methylprednisolone (30 mg/kg/day) treatment from two children with newly diagnosed AML (AML-M3 and AML-M4). In both patients maturation of leukemic cells has previously been reported four days (in patient with AML-M3) and two weeks (in patient with AML-M4) after HDMP treatment. Electron microscopy revealed the characteristic ultrastructural changes of various stages of apoptosis four days after HDMP treatment in a case with AML-M3. Morphologic evidence of apoptosis induced by HDMP were also detected on Wright-stained and toluidine blue stained semithin sections of BM preparations in a patient with AML-M4 and AML-M3 respectively. These findings suggest that HDMP which could induce in vivo terminal differentiation in myeloid leukemic cells is also able to induce apoptosis in patients with AML. The possibility of HDMP-induced apoptosis should be evaluated in a larger series of patients with AML and other types of malignant tumors.

High remission rate in acute myeloblastic leukemia in children treated with high-dose methylprednisolone

Since the differentiating effect of high-dose methylprednisolone (HDMP) on myeloid leukemic cells has been shown in one of our patients with acute myeloblastic leukemia (AML-M4), 27 previously untreated children with AML were given HDMP (20-30 mg/kg per day) combined with cytosine arabinoside (Ara-C; 3 mg/kg) for the first 2 weeks of induction therapy. Marked clinical improvement was observed in all patients with the exception of one who died within 24 hours of the treatment. Enlarged liver and spleen (greater than 5 cm) became nonpalpable in 3 (37%) out of 8 and 5 (100%) out of 5 patients, respectively, and bone marrow blasts decreased below 5% in 7 patients (27%) within 2 wk of HDMP and Ara-C treatment. Adriamycin (1 mg/kg) was added 2 wk after initiation of induction therapy. Twenty-two (84.6%) of the 26 patients achieved complete remission, 3 (11.5%) had partial remission and no response was obtained in one. Treatment was well tolerated. The addition of HDMP as a differentiating and/or cytolytic agent to conventional anti-leukemic chemotherapy increased the complete remission rate and prolonged the duration of remission of our AML patients.

Dexamethasone caused alterations in poly(A) polymerase levels of a human leukemic cell line

The effect of glucocorticosteroids upon the poly(A) synthetic and degrading activity has been studied in steroid sensitive and resistant human leukemic cell lines. At least a two-fold increase in the levels of poly(A) polymerase activity was found in soluble, cytoplasmic extracts from the steroid sensitive human malignant T-cells of the MOLT3 line after 24-h treatment with dexamethasone. Longer exposure time of the cultured cells to the steroid resulted in a gradual decrease of the poly(A) polymerase activity level. Pretreatment of the cells with progesterone, a competitive inhibitor of dexamethasone, prevented the dexamethasone induced increase in the level of poly(A) polymerase activity, while progesterone alone had no effect on the enzyme level. In contrast, the levels of poly(A) nucleases activity remained constant following steroid treatment. In the steroid resistant human leukemic B-cell line Daudi no alterations in the poly(A) metabolizing enzymes could be measured in response to dexamethasone. Thus we suggest that poly(A) polymerase levels may be used to predict sensitivity of leukemic cells to glucocorticosteroid treatment.

Steroid receptors in pulmonary lymphangiomyomatosis

As an initial step in investigating the role of steroid hormones in lymphangiomyomatosis, the cytosolic receptors for steroid hormones were determined by a dextran charcoal method. Specific saturable receptors were found for estrogens (measured with [3H] estradiol +/- unlabeled diethylstilbestrol), progestins (measured with [3H] R5020 +/- unlabeled R5020), and glucocorticoids (measured with [3H] dexamethasone +/- unlabeled dexamethasone); they were absent for androgens (measured with [3H] R1881 +/- unlabeled R1881). Even though receptor levels were of low absolute value, they were significant because specimens of normal lung display no receptor at all. Steroid hormones may have direct effects on pulmonary lymphangiomyomatosis tissue mediated by specific receptors.

Cooperative effect of 1 alpha,25-dihydroxyvitamin D3 and dexamethasone in inducing differentiation of mouse myeloid leukemia cells

Murine myeloid leukemia cells (MI) are induced to differentiate into macrophages by the metabolically active form of vitamin D3,1 alpha,25-dihydroxyvitamin D3[1 alpha,25(OH)2D3] (E. Abe et al., (1981) Proc. Natl. Acad. Sci. USA 78, 4990-4994). At 0.12-120 nM, 1 alpha,25(OH)2D3 suppressed cell growth in a dose-dependent manner and markedly induced phagocytic activity, lysozyme activity, and C3-receptor formation. The potency of 1 alpha,25(OH)2D3, at 0.12-120 nM, in inducing differentiation was nearly equivalent to that of 10-10,000 nM of dexamethasone, one of the most potent stimulators of Ml cells. Simultaneous treatment with low physiological plasma concentrations of 1 alpha,25(OH)2D3 (0.12 nM) and dexamethasone (10 nM) induced differentiation of Ml cells equivalent to the responses obtained only by using much higher concentrations of the respective steroids when used separately. In addition, two variant clones of Ml cells resistant to either 1 alpha,25(OH)2D3 or dexamethasone were isolated. One was resistant to 120 nM of 1 alpha,25(OH)2D3 but sensitive to 10-1000 nM of dexamethasone. The other was resistant to 1000 nM of dexamethasone but sensitive to 12 nM of 1 alpha,25(OH)2D3. This suggests that the mechanism of action of 1 alpha,25(OH)2D3 in inducing differentiation of Ml cells is different at least in part from that of dexamethasone, and that combination therapy by both steroids may be useful in reducing leukemogenicity of Ml cells in vivo.

Control of growth and normal differentiation in leukemic cells: regulation of the developmental program and restoration of the normal phenotype in myeloid leukemia

The origin and evolution of malignancy involves a sequence of genetic changes. Evidence has, however, been obtained with various types of tumors that malignant cells have not lost the genes that control normal growth and differentiation. An in vitro cloning and cell culture system has been developed to determine and dissect the controls that regulate normal myeloid cell growth, differentiation, and malignancy and to suggest a new approach to the therapy of myeloid leukemia based on the induction of normal differentiation in malignant cells. Experiments on induction of normal cell differentiation and restoration of the normal phenotype in myeloid leukemia by the physiological inducer of differentiation, the appropriate molecular form of the macrophage and granulocyte-inducing protein MGI, have also been used to formulate a general model for regulation of developmental programs and the origin and evolution of the malignancy.

Differentiation of mouse myeloid leukemia cells induced by 1 alpha,25-dihydroxyvitamin D3

Mouse myeloid leukemia cells can be induced to differentiate into macrophages in vitro by 1 alpha,25-dihydroxyvitamin D3, the active form of vitamin D3. The minimal concentration of 1 alpha,25-dihydroxyvitamin D3 to induce the cell differentiation was 0.12 nM. The degree of cell differentiation in various markers induced by 12 nM 1 alpha,25-dihydroxyvitamin D3 was nearly equivalent to that induced by 1 microM dexamethasone, the most potent known stimulator. Among several markers of the differentiation by 1 alpha,25-dihydroxyvitamin D3, phagocytic activity was induced within 24 hr, and this was followed by induction of lysozyme and locomotive activities. Similar changes were also induced by 0.01-1 microM 1 alpha-hydroxyvitamin D3. 25-Hydroxyvitamin D3 and 24R,25-dihydroxyvitamin D3 showed only weak inducing activity. These results suggest the possibility that, in addition to its wellknown biological activities in enhancing intestinal calcium transport and bone mineral mobilization, 1 alpha, 25-dihydroxyvitamin D3 is involved in the differentiation of bone marrow cells.

Constitutive gene expression in myeloid leukemia and cell competence for induction of differentiation by the steroid dexamethasone

Regulation of the cytoplasmic protein changes during myeloid cell differentiation has been analyzed with two-dimensional gel electrophoresis and differentiation-defective cell mutants. The cells studied include a clone of myeloid leukemia cells (clone 11) that can be induced to differentiate to macrophages by the protein inducer MGI and the steroid dexamethasone (Dex) and mutant clones that were inducible for differentiation to macrophages by MGI but not by Dex. The mutants were not defective in the specific binding of [3H]Dex to cytoplasmic receptors or in the transport and nuclear binding of the receptor--steroid complex. The protein patterns in the mutants showed both specific constitutive protein changes and nonresponding proteins. Twenty-one percent of the Dex-induced protein changes and 2% of the MGI-induced protein changes in clone 11 were constitutively expressed in the mutants. In addition, 28% of the proteins that responded to Dex in clone 11 did not respond to Dex in the mutants, whereas only 4% of the proteins that responded to MGI in clone 11 did not respond to MGI. The higher percentage of constitutive changes was thus associated with a larger defect in induction. The proteins with an abnormal response to Dex still showed a normal response to MGI, and the constitutive changes and nonresponding proteins were different for the two inducers. It is suggested that specific constitutive protein changes expressed by the mutants produced an asynchrony in the developmental program, resulting in a defective response to Dex and to MGI, and that this may apply to other inducers and developmental programs.

Constitutive uncoupling of pathways of gene expression that control growth and differentiation in myeloid leukemia: a model for the origin and progression of malignancy

Chemical carcinogens and tumor promoters have pleiotropic effects. Tumor initiators can produce a variety of mutations and tumor promotres can regulate a variety of physiological molecles that control growth and differentiation. The appropriate mutation and the regulation of the appropriate molecules to induce cell growth can initiate and promote the sequence of changes required for transformation of normal cells into malignant cells. After this sequence of changes, some tumors can still be induced to revert with a high frequency from a malignant phenotype to a nonmalignant phenotype. Results obtained from analysis of regulation of growth and differentiation in normal and leukemic myeloid cells, the phenotypic reversion of malignancy by induction of normal differentiation in myeloid leukemia, and the blocks in differentiation-defective leukemic cell mutants have been used to propose a general model for the origin and progression of malignancy. The model states that malignancy originates by changing specific pathways of gene expresion required for growth from inducible to constitutive in cells that can still be induced to differentiate normally by the physiological inducer of differentiation. The malignant cells, unlike the normal cells, then no longer require the physiological inducer for growth. This changes the requirements for growth and uncouples growth from differentiation. Constitutive expression of other specific pathways can uncouple other controls, which then causes blocks in differentiation and the further progression of malignancy. The existence of specific constitutive pathways of gene expression that uncouple controls in malignant cells can also exlain the expresion of fetal proteins, hormones, and some other specialized products of normal development in various types of tumors.

Glucocorticoid receptors and glucocorticoid sensitivity of human leukemic cells

We have established optimal conditions for the measurement of glucocorticoid receptors (GR) in human white cells using a whole-cell binding assay with [3H]dexamethasone as the ligand, and the subsequent determination of the GR content in normal human lymphocytes and in leukemic cells of patients with various forms of acute and chronic leukemia. A number of leukemia cell lines in continuous culture were also subjected to the GR assay, and the results were correlated with the sensitivity of these cell lines to glucocorticoid steroids in vitro. The GR content of normal human lymphocytes amounted to 4,850 +/- 1,340 (mean +/- SD) receptors/cell. The mean equilibrium dissociation constant (KD) of the interaction of [3H]dexamethasone with the GR was 1.2 x 10(-8) M. Steroidal compounds with a known glucocorticoid potency effectively competed for the binding, whereas steroids devoid of glucocorticoid activity (e.g. estradiol-17 beta and testosterone) were ineffective. The GR content of the blast cells obtained from eight patients suffering from acute leukemia and four patients with a blast crisis of chronic myelocytic leukemia was found to be highly variable (3,230-29,900 receptors/cell), while the lymphocytes of six patients with chronic lymphatic leukemia contained a rather stable GR content (2,930-5,120 receptors/cell), which was comparable with that of normal lymphocytes. GR was identified in all the 12 malignant continuous white cell lines studied. Large cells contained more GR than the smaller ones. There was no apparent correlation between the GR concentration and the sensitivity of the cells in vitro to glucocorticoids as judged by [3H]thymidine incorporation studies. Distribution of the surface markers in the leukemic cell lines did not relate to the GR concentration. We conclude that the presence of GR is probably a universal feature of the leukemic cells, and, from a clinical standpoint, probably does not alone imply steroid responsiveness.

Requirements for RNA and protein synthesis in the induction of several differentiation-markers in a myeloid leukemia cell line

In a myeloid leukemia cell line, the inducibilities of the Fc receptor, phagocytosis and cell motility were compared. Thymidine analogues such as BUdR, BCdR and IUdR blocked the induction of phagocytosis and motility but not induction of the Fc receptor. This BUdR susceptibility in the induction of phagocytosis and motility was lost in a BUdR resistant line which was isolated for its growth capability in a high concentration of BUdR. Actinomycin D and puromycin brought about a marked decrease in the inducibility of phagocytosis but not in that of the Fc receptor. This led us to the following conclusion: There is a genetic control in the inducibility of phagocytosis and motility in this cell line, and the incorporation of BUdR into cellular DNA results in the DNA becoming unresponsive to a differentiation-stimulating factor. In contrast, gene activation does not seem to be necessary for induction of the Fc receptor. The order of induction of several differentiation markers was also discussed.