Proliferation kinetics and PCNA expression of HL-60 cells following ionizing irradiation and granulocytic differentiation

The human promyelocytic leukaemia cell line, HL-60, was investigated with regard to proliferation and terminal differentiation following irradiation. The cells were X-irradiated and induced with 1.25% dimethyl sulfoxide (DMSO) towards the granulocytic lineage. Proliferation was measured via cell growth, clonogenicity and the bromodeoxyuridine/DNA incorporation assay. Immunohistochemical detection of proliferating cell nuclear antigen (PCNA) expression was used to discriminate cycling from non-cycling cells. The differentiation obtained was proved by testing for the immune function of the respiratory burst (NBT reduction test). The HL-60 cells studied revealed a high radiosensitivity (D₀= 0.63 Gy). After induction with DMSO, declines in cell growth, clonogenicity and PCNA positivity of the cells indicated a decrease in proliferation and an increase in differentiation. Starting on day 2 in culture, irradiation after seeding with 1 Gy accelerated the loss of the PCNA expression in induced cells (46%v. 3% PCNA-negative control cells on day 3). Induced cells gained the capability of exerting the respiratory burst, which was found to be dose-dependent radiosensitive (42% and 12% NBT-positive cells after 1 and 2 Gy, respectively, v. 53% NBT-positive control cells on day 8). Subpopulations in the cell line were evident in all parameters investigated. We discuss the HL-60 cell, not only as a model comparable to human progenitor cells, but also as a suitable tool in radiobiological research with regard to proliferation and differentiation following ionizing irradiation.     

EMF induces differentiation in HL-60 cells

This investigation provides evidence that a 60-Hz electromagnetic field (EMF) at 1 gauss (G) can drive differentiation of cultured hematopoietic progenitor cells. HL-60 cells are known to differentiate from a nonphagocytic suspension culture to an attached fibroblast-like culture with high phagocytic activity in the presence of the tumor-promoting phorbol ester 12-O-tetradecanoylphorbal-13-acetate (TPA). The effect of 60-Hz EMF at 1 G on differentiation is approximately equivalent to treatment of the cells with 250-500 pg/ml TPA. Furthermore, the effect of both EMF and TPA treatment on differentiation is additive at low TPA concentrations. The results strongly suggest similarities between the effects of TPA treatment and EMF exposure and thus provide an approach for tracing the origins of the molecular effects of EMF exposure, as many transduction pathways in the differentiative process are defined.     

S-Adenosylhomocysteine hydrolase activity during differentiation of HL-60 cells

Early changes in S-adenosylhomocysteine (SAH) hydrolase activity during DMSO-induced granulocytic differentiation of HL-80 ceils were followed. Within 24 h a decrease of activity of SAH hydrolase could be detected in induced cultures but not in control cultures. This decrease could be shown to be associated with G1 phase of the cell cycle and was detected prior to phenotypic changes of the ceils.     

Uptake of transcobalamin II-bound cobalamin by HL-60 cells: effects of differentiation induction

Binding and uptake of transcobalamin II-bound cobalamin by HL-60 promyelocytic leukemia cells proceed through receptor-mediated endocytosis. The affinity constant of the receptor for transcobalamin II-cobalamin was found to be 6.1 liter/nmol and the maximal rate of uptake 12 pmol/10(9) cells/h. This uptake is mediated by about 3000 receptor sites per cell. Evidence is presented that the receptor recirculates from the cell surface to the lysosomes and vice versa. Upon differentiation induction of the cells by either DMSO in granulocytic direction or by 1,25-dihydroxy-vitamin D3 in monocytic direction a rapid decline in cellular uptake and cell surface binding of the protein-bound vitamin ensues. In particular the internalization of the complex decreases faster than all other observed signs of the ongoing differentiation process, such as reduction in the OKT9-reactive transferrin receptor, increase in lineage-specific surface markers, and decrease in [3H]thymidine incorporation and actual cell proliferation. The transcobalamin II receptor on the cell surface appears to be a proliferation-associated membrane component in human leukemic cells.     

Store-operated calcium channels in HL-60 cells effects of temperature,differentiation and loperamide

The effect of temperature on calcium release and influx has been compared in differentiated and undifferentiated HL-60 cells. Receptor-mediated release of intracellular calcium by ATP was little affected by temperature in HL-60 cells. In differentiated HL-60 cells the store-operated calcium (SOC) channel-dependent sustained elevation of calcium levels after ATP was maximal at 25-29 degrees C; at higher temperatures calcium levels returned relatively rapidly towards basal levels. In undifferentiated cells, a SOC channel-dependent sustained elevation of calcium levels was not observed with levels returning to basal levels much more rapidly than in differentiated cells. The initial thapsigargin-initiated elevation of calcium did not become maximal until about 25 degrees C in both differentiated and undifferentiated HL-60 cells. In differentiated cells, the SOC channel-dependent sustained elevation of calcium after thapsigargin was maximal at 30-37 degrees C, while in undifferentiated cells, the sustained elevation was maximal at 25-30 degrees C. Loperamide, which augments the SOC channel-dependent sustained elevation of calcium, showed a temperature-dependent response that was maximal at about 22 degrees C after either ATP or thapsigargin and was minimal at 37 degrees C. In contrast, inhibition of SOC channel-dependent elevation of calcium by miconazole or trifluoperazine was not greatly affected by temperature.     

Synergistic effects of ionizing radiation and 60 Hz magnetic fields

Experiments designed to evaluate the synergistic production of clastogenic effects by ionizing radiation and 60 Hz magnetic fields were performed using human lymphocytes from peripheral blood. Following exposure to ionizing radiation, cells were cultured in 60 Hz magnetic fields having field strengths up to 1.4 mT. Cells exposed to both ionizing radiation and 60 Hz magnetic fields demonstrated an enhanced frequency of near tetraploid chromosome complements, a feature not observed following exposure to only ionizing radiation. The results are discussed in the context of a multiple-stage model of cellular transformation, employing both initiating and promoting agents. © 1993 Wiley-Liss. Inc.     

Retinoic acid differentiation of HL-60 cells promotes cytoskeletal polarization

Retinoic acid (RA) treatment of HL-60 cells in vitro induces granulocytic differentiation, involving reorganization of the nucleus and cytoplasm, development of chemoattractant-directed migration, and eventual apoptosis. The present studies with HL-60/S4 cells document that major elements of the cytoskeleton are changed: actin increases by 50%; vimentin decreases by more than 95%. The cellular content of alpha-tubulin does not significantly change; but the centrosomal-microtubule (MT) array moves away from the lobulating nucleus. Cytoskeletal-modifying chemicals modulate this polarized reorganization: Taxol and cytochalasin D enhance centrosome movement; nocodazole reverses it. Cytoskeletal-modifying chemicals do not appear to affect nuclear lobulation or the integrity of envelope-limited chromatin sheets (ELCS). Employing bcl-2-overexpressing HL-60 cells permitted demonstration of nuclear lobulation, ELCS formation, and centrosome-MT movement concomitantly during RA-induced differentiation, implying independence between the cellular reorganization and apoptotic programs. RA appears to promote an inherent potential in HL-60 cells for cytoskeletal polarization, likely to be important for chemoattractant-directed cell migration, an established characteristic of mature granulocytes.     

Triphenyltin enhances the neutrophilic differentiation of promyelocytic HL-60 cells

Triphenyltin (TPT) is an environmental endocrine disruptor and toxic substance, but little information is available on its immunological effects. To assess the effect of TPT on leukocyte differentiation, we investigated its effect on the neutrophilic differentiation of HL-60 cells induced by dimethyl sulfoxide and granulocyte colony-stimulating factor (G-CSF) for 6 days. At a low concentration, 10(-7)M, TPT increased superoxide production by differentiated HL-60 cells stimulated with opsonized zymosan (OZ) by about 45% and increased expression of CD18, a component of the OZ-receptor, by about 90%. Real-time PCR analysis revealed that TPT augmented the expression not only of CD18 but also of components of superoxide-generating NADPH-oxidase, p47phox, 2.7-fold, and p67phox, 2.0-fold, and of granulocyte colony-stimulating factor receptor (G-CSFR), 3.0-fold, whereas various other endocrine disruptors, including parathion, vinclozolin, and bisphenol A, had no such enhancing effects. The results of a DNA macroarray analysis showed that TPT enhanced the expression of G-CSFR and certain other neutrophil functional proteins, including CD14 and myeloid leukemia cell differentiation protein (MCL-1), and that TPT induced a decrease in expression of LC-PTP, leukocyte protein-tyrosine phosphatase, to about half the control level. The TPT-dependent suppression of LC-PTP was confirmed by real-time PCR analysis, and the results of immunoblotting indicated that TPT enhances the expression of myeloid specific tyrosine kinase hck by about 30% at the protein level, and this together with the reduction of LC-PTP may enhance tyrosine phosphorylation, in turn resulting in enhancement of superoxide production. These findings suggest that TPT may have an enhancing effect on the neutrophilic maturation of leukocytes.     

Interferon-inducible gene expression in HL-60 cells: effects of the state of differentiation.

The promyelocytic leukemia line HL-60 can be terminally differentiated in vitro to either monocyte/macrophages or granulocytes. We used this cell line to test whether the state of differentiation of a cell changes its response to interferon (IFN). The characteristics of expression of several IFN-alpha- and IFN-gamma-inducible genes in undifferentiated and differentiated HL-60 cells were examined. p67, an IFN-gamma-inducible protein, was induced similarly in three cell types, whereas another IFN-gamma-inducible protein, p56, was induced strongly only in undifferentiated cells. In contrast, two isozymes of 2,5(A)-synthetase were induced better in differentiated cells in response to either IFN. Several IFN-alpha-inducible mRNAs, e.g., 561, 6-16, 1-8, and 2A, were induced much more strongly in granulocytes than in macrophages or in undifferentiated cells. Electrophoretic mobility shift assays using the IFN-stimulated response element of gene 561 and nuclear extracts of IFN-alpha-treated cells revealed the appearance of one complex and the disappearance of another one, concomitant with differentiation of the cells to granulocytes. These observations suggest that expression of IFN-inducible genes in HL-60 cells is regulated by trans-acting factors whose activity changes with the state of differentiation of the cells. Our study may have implications in the optimal clinical use of IFNs. Inducing cellular differentiation may augment the efficacy of IFNs as antitumor agents.     

Glutamine promotes colony formation in bone marrow and HL-60 cells; accelerates myeloid differentiation in induced HL-60 cells

Several studies indicate that glutamine is a critical requirement for growth of cultured cells. The present studies describe the effect of deprivation of glucose or glutamine on mouse bone marrow cell or HL-60 cell colony formation in soft agar. The mouse bone marrow cells were induced to undergo granulocyte/macrophage type differentiation by colony-stimulating factor. Glutamine, but not glucose, was found to be an indispensable metabolite for the cloning of HL-60 cells or differentiated mouse bone marrow cells. In addition, the effect of glucose or glutamine on the rate of differentiation of dimethylsulfoxide (DMSO)-induced HL-60 cells in liquid culture was studied. Glutamine was found to be superior to glucose in its ability to support the proliferation and myeloid differentiation of HL-60 cells. When an optimal concentration of DMSO was used, the rate of differentiation of induced HL-60 cells was found to be a function of the concentration of glutamine. In addition to these studies glutamine utilization and product formation was studied in induced and uninduced HL-60 cells after 60 min incubation with 1 mM initial glutamine concentration. The fractional distribution of the glutamine carbon into its metabolic products remained unchanged in induced versus uninduced HL-60 cells. However, the rate of utilization of glutamine and product formation by terminally differentiated HL-60 cells was less than the rate of utilization of glutamine by undifferentiated HL-60 cells. The data do not explain the role of glutamine in the complex process of differentiation but establish the critical requirements for glutamine, but not glucose, in myelopoiesis.     

Glutamine promotes colony formation in bone marrow and HL-60 cells; Accelerates myeloid differentiation in induced HL-60 cells

Summary Several studies indicate that glutamine is a critical requirement for growth of cultured cells. The present studies describe the effect of deprivation of glucose or glutamine on mouse bone marrow cell or HL-60 cell colony formation in soft agar. The mouse bone marrow cells were induced to undergo granulocyte/macrophage type differentiation by colony-stimulating factor. Glutamine, but not glucose, was found to be an indispensable metabolite for the cloning of HL-60 cells or differentiated mouse bone marrow cells. In addition, the effect of glucose or glutamine on the rate of differentiation of dimethylsulfoxide (DMSO)-induced HL-60 cells in liquid culture was studied. Glutamine was found to be superior to glucose in its ability to support the proliferation and myeloid differentiation of HL-60 cells. When an optimal concentration of DMSO was used, the rate of differentiation of induced HL-60 cells was found to be a function of the concentration of glutamine. In addition to these studies glutamine utilization and product formation was studied in induced and uninduced HL-60 cells after 60 min incubation with 1 mM initial glutamine concentration. The fractional distribution of the glutamine carbon into its metabolic products remained unchanged in induced versus uninduced HL-60 cells. However, the rate of utilization of glutamine and product formation by terminally differentiated HL-60 cells was less than the rate of utilization of glutamine by undifferentiated HL-60 cells. The data do not explain the role of glutamine in the complex process of differentiation but establish the critical requirements for glutamine, but not glucose, in myelopoiesis. This work has been supported by USPHS Grants AM 31624 and CA 00859 and a Faculty Research Grant from Texas College of Osteopathic Medicine.     

Analysis of cell-surface protein changes accompanying differentiation of HL-60 cells

The cell-surface proteins of HL-60 human promyelocytic leukemia cells have been compared to those of normal human neutrophils. Proteins of HL-60 cells surface labeled with 125I differed markedly from those of normal neutrophils, as shown by immunoprecipitation and polyacrylamide electrophoresis. Differentiation of HL-60 cells by treatment with dimethylformamide, trans-retinoic acid, or 12-O-tetradecanoylphorbol acetate did not modify the predominant surface-labeled proteins of HL-60 cells to produce a pattern similar to that of normal, mature neutrophils. However, the agents did induce greater quantities of minor cell-surface proteins immunoprecipitated by hyperimmune anti-human neutrophil serum. These immunoprecipitated proteins resembled several of the surface-labeled polypeptides of normal human neutrophils.     

Dose rate effects of low-LET ionizing radiation on fish cells

Radiobiological responses of a highly clonogenic fish cell line, eelB, to low-LET ionizing radiation and effects of dose rates were studied. In acute exposure to 0.1–12 Gy of gamma rays, eelB’s cell survival curve displayed a linear–quadratic (LQ) relationship. In the LQ model, α, β, and α/β ratio were 0.0024, 0.037, and 0.065, respectively; for the first time that these values were reported for fish cells. In the multi-target model, n, D _o, and D _q values were determined to be 4.42, 2.16, and 3.21 Gy, respectively, and were the smallest among fish cell lines being examined to date. The mitochondrial potential response to gamma radiation in eelB cells was at least biphasic: mitochondria hyperpolarized 2 h and then depolarized 5 h post-irradiation. Upon receiving gamma rays with a total dose of 5 Gy, dose rates (ranging between 83 and 1366 mGy/min) had different effects on the clonogenic survival but not the mitochondrial potential. The clonogenic survival was significantly higher at the lowest dose rate of 83 mGy/min than at the other higher dose rates. Upon continuous irradiation with beta particles from tritium at 0.5, 5, 50, and 500 mGy/day for 7 days, mitochondria significantly depolarized at the three higher dose rates. Clearly, dose rates had differential effects on the clonogenic survival of and mitochondrial membrane potential in fish cells.     

The effects of ionizing radiation on osteoblast-like cells in vitro

The well-described detrimental effects of ionizing radiation on the regeneration of bone within a fracture site include decreased osteocyte number, suppressed osteoblast activity, and diminished vascularity. However, the biologic mechanisms underlying osteoradionecrosis and the impaired fracture healing of irradiated bone remain undefined. Ionizing radiation may decrease successful osseous repair by altering cytokine expression profiles resulting from or leading to a change in the osteoblastic differentiation state. These changes may, in turn, cause alterations in osteoblast proliferation and extracellular matrix formation. The purpose of this study was to investigate the effects of ionizing radiation on the proliferation, maturation, and cytokine production of MC3T3-E1 osteoblast-like cells in vitro. Specifically, the authors examined the effects of varying doses of ionizing radiation (0, 40, 400, and 800 cGy) on the expression of transforming growth factor-beta1 (TGF-beta1), vascular endothelial growth factor (VEGF), and alkaline phosphatase. In addition, the authors studied the effects of ionizing radiation on MC3T3-E1 cellular proliferation and the ability of conditioned media obtained from control and irradiated cells to regulate the proliferation of bovine aortic endothelial cells. Finally, the authors evaluated the effects of adenovirus-mediated TGF-beta1 gene therapy in an effort to "rescue" irradiated osteoblasts. The exposure of osteoblast-like cells to ionizing radiation resulted in dose-dependent decreases in cellular proliferation and promoted cellular differentiation (i.e., increased alkaline phosphatase production). Additionally, ionizing radiation caused dose-dependent decreases in total TGF-beta1 and VEGF protein production. Decreases in total TGF-beta1 production were due to a decrease in TGF-beta1 production per cell. In contrast, decreased total VEGF production was secondary to decreases in cellular proliferation, because the cellular production of VEGF by irradiated osteoblasts was moderately increased when VEGF production was corrected for cell number. Additionally, in contrast to control cells (i.e., nonirradiated), conditioned media obtained from irradiated osteoblasts failed to stimulate the proliferation of bovine aortic endothelial cells. Finally, transfection of control and irradiated cells with a replication-deficient TGF-beta1 adenovirus before irradiation resulted in an increase in cellular production of TGF-beta1 protein and VEGF. Interestingly, this intervention did not alter the effects of irradiation on cellular proliferation, which implies that alterations in TGF-beta1 expression do not underlie the deficiencies noted in cellular proliferation. The authors hypothesize that ionizing radiation-induced alterations in the cytokine profiles and differentiation states of osteoblasts may provide insights into the cellular mechanisms underlying osteoradionecrosis and impaired fracture healing.     

Realgar-induced differentiation is associated with MAPK pathways in HL-60 cells

The clinical efficacy and safety of realgar (arsenic sulfide, As(4)S(4)) in the treatment of acute promyelocytic leukemia in China have given rise to an upsurge in research on the underlying mechanism. We prepared realgar nanoparticles (RNPs) to examine their effect on the differentiation of HL-60 cells. Treatment with RNPs at 6 microM for 72 h induced cell differentiation that was assessed by morphological change, NBT reductive ability, and elevation of CD11b expression at both mRNA and protein levels. The RNP-induced differentiation was synergized, enhanced and suppressed by the inhibition of p38 MAPK, JNK and ERK pathways, respectively. Our findings demonstrate that MAPK signaling pathways are closely related to the RNP-induced differentiation in HL-60 cells.     

Interferon effects upon fluorouracil metabolism by HL-60 cells

In order to better understand the synergistic antiproliferative effects of interferon in combination with fluorouracil (FUra), we studied effects of alpha 2-interferon upon FUra induced inhibition of thymidylate synthase of HL-60 cells. The 50% inhibitory dose for FUra decreased from approximately 75 microM to 10 microM following interferon treatment, as measured by whole cell activity assays. Enhanced FUra inhibition of cytosolic [3H] - FdUMP binding of interferon treated cells was also noted. FdUMP accumulation following FUra treatment increased over 10 fold in interferon treated cells, but dUMP did not increase. These results suggest that interferon can sensitize cells to FUra inhibition of thymidylate synthase by enhancing accumulation of FdUMP.     

Calcium stores in electropermeabilized HL-60 cells before and after differentiation

Non-induced HL-60 cells (N-IND) and HL-60 cells induced to differentiate with 2 microM retinoic acid (IND) were electropermeabilized with electrical discharges, and the intracellular Ca2+ stores were measured in each type of cell. Both N-IND and IND cells accumulate Ca2+ in the presence of ATP after electropermeabilization. The Ca2+ is stored in at least two different compartments; accumulation in one of the compartments is inhibited by oligomycin and CCCP, and it is not releasable by Ins(1,4,5)P3. The maximal accumulation of Ca2+ by the Ins(1,4,5)P3 sensitive pool is about 0.3 nmol/10(6) cells and 0.9 nmol/10(6) cells for the N-IND and for the IND cells, respectively, and the half-maximal value occurs at a free Ca2+ concentration of 0.23 microM and 0.63 microM, respectively. The oligomycin + CCCP sensitive pool hardly accumulates any Ca2+ at this level of free Ca2+, but at higher free [Ca2+] (greater than microM) its maximal capacity is 80-100-fold higher than the Ins(1,4,5)P3-sensitive pool (about 17-18 nmol/10(6) cells). It is concluded that at physiological free Ca2+ concentrations, the non-mitochondrial Ca2+ pool is regulating the intracellular free Ca2+ in N-IND and IND HL-60 cells, and that this Ca2+ pool can be mobilized by Ins(1,4,5)P3. Furthermore, the capacity of this pool increases about 3-fold when the cells are induced to differentiate with retinoic acid.     

PAF-acether transfer activity in HL-60 cells is induced during differentiation

Platelet-activating factor is a proinflammatory lipid active at subnanomolar concentrations. The intermembrane transfer of a biologically active PAF analog has been previously demonstrated in macrophages. Here we demonstrate that the specific activity of this transfer activity increases when HL-60 cells are induced to differentiate by treatment with dimethyl sulfoxide, dibutyryl cAMP or phorbol diester. In undifferentiated HL-60 cells, methylcarbamyl-PAF transfer activity was only 0.56 U.min-1.mg-1. This basal value was increased 2.6 and 6.7 times upon granulocytic and macrophagic differentiation, respectively. On the other hand, the transfer of 2-O-methyl-PAF, a cytotoxic analog with no PAF biological activity, remained very low and did not vary during differentiation.