Induction of acetylcholinesterase activity in mouse neuroblastoma tissue culture cells

Tryptanthrin induces growth inhibition and neuronal differentiation in the human neuroblastoma LA-N-1 cells

Neuroblastoma is one of the most common extracranial solid cancers found in young children. The prognosis of neuroblastoma patients in advanced stages having N-myc amplification remains poor despite intensive multimodal therapy. Agents that trigger neuroblastoma cells to undergo cellular differentiation and thereby stop proliferation have attracted considerable interest as an alternative therapy. Tryptanthrin (12-dihydro-6,12-dioxoindolo-(2,1-b)-quinazoline) is a weakly basic alkaloid isolated from the dried roots of medicinal indigo plants known as Banlangen. It has been shown to possess various biological activities, such as anti-microbial, anti-inflammatory and anti-tumor activities. However, its effects and mechanism(s) of action on human neuroblastoma cells remain poorly understood. Therefore, the objective of this study is to investigate the effects of tryptanthrin on the growth and differentiation of human neuroblastoma LA-N-1 cells with N-myc amplification. Our results show that tryptanthrin inhibited the growth of the human neuroblastoma cells in a dose- and time-dependent manner. Mechanistic studies indicated that tryptanthrin induced cell cycle arrest of the human neuroblastoma LA-N-1 cells at the G0/G1 phase. Tryptanthrin also induced neuronal differentiation of LA-N-1 cells, as assessed by morphological criteria, enhancement of acetylcholine esterase activity and up-regulation of various differentiation markers. Moreover, tryptanthrin treatment led to the significant reduction of N-myc expression in LA-N-1 cells while siRNA directed against N-myc induced morphological differentiation of LA-N-1 cells. These results, when taken together, suggest that tryptanthrin suppressed the growth and induced neuronal differentiation in the human neuroblastoma LA-N-1 cells and might be exploited as a potential therapeutic candidate for the treatment of high-risk neuroblastomas with N-myc-amplification.

Neuroblastoma cell lines--a versatile in vitro model in neurobiology

Neuroblastoma (NB) cell lines are transformed, neural crest derived cells, capable of unlimited proliferation in vitro. These cell lines retain the ability of differentiation into neuronal cell types on treatment with various agents. This ability of NB cells to proliferate as well as to differentiate makes it an excellent in vitro system for various studies. This review article focuses on the applications and potential uses of murine and human NB cell lines. NB cells are extensively used for testing neurotoxicity of putative drugs such as antimalarial or anticancer agents. NB cell lines have wide applications in virus research to understand various aspects of virus-host cell interactions at the molecular and cellular levels. They have been used to dissect the relationships between proliferation, differentiation and apoptosis. This feature has been useful in understanding the pediatric cancer--neuroblastoma and for development of newer therapies.

Early and late hormonal modulation of cholinergic maturation in culture of embryonic mesencephali

Dissociated cells from 13- and 17-day-old embryonic rat mesencephali have grown in primary cultures in order to compare the early and late influences of different agents--insulin, dexamethasone and nerve growth factor (NGF)--on the expression of cholinergic maturation process. We have studied cholin acetyltransferase (ChAT) activity, which is regarded as a specific marker for cholinergic function of the brain, and a widely used differentiation marker, the acetyl-cholinesterase (AchE) enzyme. Biochemical maturation of increasing specific activity of ChAT in both younger and older cells was taken into consideration. During cultivation the AchE activity was slightly increased in younger cells, but a dramatic decrease could be noted in older ones. Insulin in concentration from 10 to 27 micrograms mL-1 causes a significant inhibition in ChAT activity in comparison with the enzyme activity measured in control cultures (insulin ranging from 1 to 100 ng), independently of embryos age. This polypeptide hormone is able to enhance AchE activity in the cultured cells, especially in older ones. With continuous treatment of the culture with dexamethasone, a synthetic glucocorticoid, the ChAT activity in younger cells reaches a maximum curve by day 9 (nine). At this time the AchE activity shows a slighter, no significant increase than at any other time during cultivation. In cell cultures taken from 17-day-old embryos however dexamethasone treatment evoked a significant decrease in ChAT activity with a concomitant increase of AchE activity which was compared to insulin treatment. In spite of the fact that the NGF is able to enhance the ChAT activity, no significant alteration in AchE activity can be measured in younger cell cultures. These results suggest an uneven expression of the enzymes in embryonic rat mesencephali in the presence of above agents depending on the age of cells.

Spectrin expression in neuroblastoma cells

Mouse neuroblastoma cells express a spectrin-related molecule containing 240 kDal (kiloDalton) and 235 kDal subunits in a 1:1 ratio. The 240 kDal and 235 kDal subunits are nearly identical to the alpha and beta subunits respectively of brain spectrin by two dimensional chymotryptic peptide mapping analysis. The neuroblastoma cells do not express a measureable quantity of a red blood cell (rbc)-type spectrin molecule. Neuroblastoma spectrin has been localized throughout the cell body, and neurites of these cells by indirect immunofluorescence studies. As neuroblastoma cells are homogeneous, neuron-like, available in large quantity, and synthesize a single variant of spectrin which is closely related to brain spectrin(240/235), it is the best available model system for the study of the synthesis, assembly and turnover of a neuronal spectrin subtype.

Serum regulation of acetylcholinesterase in cultured myotubes

A large (20S) collagen-tailed form of acetylcholinesterase associated with the neuromuscular junction appears in cultures of chick embryo muscle cells when horse serum is withdrawn from the medium. In this report, 10-day-old cultures were incubated 2 days in serum-free medium or in medium containing either horse, bovine, fetal calf, chicken, heat-treated horse or chicken serum, low (less than 100K) or high (less than 100K) molecular weight fractions of horse serum, or fibronectin. Total acetylcholinesterase activity and activity of the 20S form increased in medium without serum, with fetal calf serum and with the low-molecular-weight fraction of horse serum. The largest increase occurred with fibronectin. The results suggest that a factor(s) greater than 100K in adult sera inhibits total acetylcholinesterase production and formation of the 20S form of the enzyme.

Differentiation of neuroblastoma cells induced by an inhibitor of mevalonate synthesis: relation of neurite outgrowth and acetylcholinesterase activity to changes in cell proliferation and blocked isoprenoid synthesis

Mevinolin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, stimulates neurite outgrowth and acetylcholinesterase (ACE) activity in C1300 (Neuro-2A) murine neuroblastoma cells. Sprouting of neurites began within 4-8 h, before changes in cell proliferation could be detected by [3H]thymidine incorporation or flow cytometry. In contrast, the increase in ACE activity was temporally correlated with suppression of DNA synthesis, which occurred after 8 h. The activity of the membrane marker enzyme phosphodiesterase I was not stimulated by mevinolin. Suppression of protein synthesis with cycloheximide blocked the induction of ACE activity but only partially inhibited neurite outgrowth in the mevinolin-treated cultures. When mevinolin was removed from the culture medium, most of the cells retracted their neurites within 2 h, but ACE activity did not decline until DNA synthesis began to return to control levels after 10 h. Similarly, retraction of neurites in differentiated cells exposed to colchicine was not accompanied by a decrease in ACE activity. DNA histograms suggested that mevinolin arrests neuroblastoma cells in both the G1 and G2/M compartments of the cell cycle. Other cytostatic drugs that arrest cells at different stages of the cell cycle did not cause Neuro-2A cells to form neurites such as those seen in the mevinolin-treated cultures. When incorporation of [3H]acetate into isoprenoid compounds was studied in cultures containing mevinolin in concentrations ranging from 0.25 microM to 25 microM, the labeling of cholesterol, dolichol, and ubiquinone was suppressed by 90% or more at all concentrations. However, significant growth arrest and cell differentiation were observed only at the highest concentrations of mevinolin. Supplementing the medium with 100 microM mevalonate prevented the cellular response to mevinolin, but additions of cholesterol, dolichol, ubiquinone, or isopentenyl adenine were generally ineffective. The cholesterol content of neuroblastoma cells incubated with 25 microM mevinolin for 24 h was not diminished, and protein glycosylation, measured by [3H]mannose incorporation, was decreased only after 24 h at high mevinolin concentration. These studies suggest that the stimulation of neurite outgrowth and the increase in ACE activity induced by mevinolin are independent phenomena. Whereas neurite outgrowth is not related directly to the effects of mevinolin on cell cycling, the induction of ACE is correlated with the inhibition of cell proliferation.(ABSTRACT TRUNCATED AT 400 WORDS)

Induction of differentiation in murine neuroblastoma cells by mevinolin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase

Mevinolin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, stimulated outgrowth of neurites and increased acetylcholinesterase activity in C1300-N2A murine neuroblastoma cells cultured in medium containing 10% fetal calf serum. Changes in cell morphology and enzyme activity were concentration-dependent in the range of 0.25-25 microM mevinolin, and were accompanied by decreased incorporation of [3H]thymidine into DNA. The expression of differentiated characteristics induced by 25 microM mevinolin was blocked by simultaneous addition of 100 microM mevalonate to the culture medium. The data suggest that changes in intracellular levels of mevalonate or one of its isoprenoid derivatives may play a role in the regulation of cell differentiation.

Histochemical demonstration of acetylcholinesterase in neuroblastoma

The presence of acetylcholinesterase in the tumour cells of neuroblastoma has been shown by enzyme histochemistry. For comparison, some other tumours likely to be found in children and commonly presenting histologically as small cell tumours have also been studied. Acetylcholinesterase activity was seen in rhabdomyosarcoma, but, compared with neuroblastoma, the activity was focal and sparse. One Ewing's tumour and a lymphoblastic lymphoma were negative for the enzyme reaction. Some of the ultrastructural features of neuroblastoma are correlated with the presence of this enzyme. Acetylcholinesterase enzyme histochemistry may provide a useful adjunct in the distinction of neuroblastoma from other small cell tumours.

Nerve growth factor and neural oncology

The precise role of the nerve growth factor protein (NGF) during the growth and development of the human nervous system is not determined. Although it appears to influence a number of neural functions, its mechanism of action is poorly understood. A number of researchers have proposed that NGF may be involved in several pathological conditions including cancer. It has been shown that NGF is secreted by certain sarcoma (23), neuroblastoma (113), and glioma (7,102,136) cell lines and can bind to neuroblastoma and metastatic melanoma cell lines (42). Neuroblastoma (136,181) and pheochromocytoma (165) cells in vitro can be induced by NGF to differentiate toward a morphologically "more benign" state and appropriate NGF treatment of rats can reduce the number of chemically induced gliomas and neurinomas (174,178). NGF can also reduce the growth of intracerebrally inoculated anaplastic glioma cells (172). Anti-NGF treatment of rats (178) and mice (179) can alter the tumor distribution observed following ethylnitrosourea or benzo(a)pyrene treatment (10). In humans, it has been reported that serum levels of NGF are usually elevated in persons "at risk" for neurofibromatosis (156). The precise nature of the NGF role is not known in these instances. Further understanding of the action of NGF could be of clinical importance.

Nervous system-specific protein D2 associated with neurite outgrowth in nerve cell cultures

Dissociated cerebral cells from fetal rat brain were grown in culture for various periods. After 12 days in culture the nervous system-specific surface membrane protein D2 reached both maximal specific concentration and maximal amount. Moreover, most of this D2 protein was in the perinatal form with high electrophoretic mobility. The amount of perinatal D2 protein possibly followed the amount of neurites in this system. D2 protein was also found in 2 neuroblastoma C-1300 clones: Neuro 2a and NB 41A3. By addition of gangliosides, Neuro 2a cells could be induced to differentiate and form processes, and D2 protein was significantly increased. However, in both differentiated and undifferentiated neuroblastoma cells D2 protein was present in the adult form with slow electrophoretic mobility. NB 41A3 cells were unaffected by gangliosides and D2 protein was not changed. Thus ganglioside treatment of Neuro 2a tumor cells was followed by a cellular response only partly similar to developmental events concomitant to differentiation of primary cells.

Protein-free medium for C-1300 mouse neuroblastoma cells

An optimized medium, designated MCDB 411, has been developed for mouse neuroblastoma cells. At cell densities of 1 x 10(4) cells/cm2 or greater, several different clones of C1300 mouse neuroblastoma cells can be cultured serially in Medium MCDB 411 with no serum or other undefined supplementation and with a doubling time of about 24 h. At clonal densities it is necessary to supplement the medium with 1.0 micrograms/ml insulin. Alternately, good clonal growth can be obtained without direct supplementation by coating the culture dishes with insulin and rinsing off all that is not tightly bound. Primary cultures of cells from serially transplanted C1300 tumors that have never been cultured previously in vitro can be established directly in unsupplemented Medium MCDB 411 with rapid initiation of multiplication and no apparent crisis or selection for minority cell types. The availability of a synthetic medium that supports growth of neuroblastoma cells without supplementation should facilitate the use of these cells as model systems for the study of neuronal function and differentiation.

Developments in the biology of neuroblastoma: implications for diagnosis and treatment

There has been little improvement in the prognosis for neuroblastoma in childhood over recent years. The authors review recent investigations into the biology of the tumour and discuss their implications for diagnosis and therapy. Immunological studies suggest a heterogeneity in cell-surface antigens on different human neuroblastoma lines/fresh tumours. The reagents being developed against these antigens will play a rôle in the diagnosis of metastatic spread, and may be useful in autologous bone-marrow transplantation programmes. The occasional in vivo differentiation of the tumour is reviewed, with particular reference to in vitro studies on the differentiation of human and murine neuroblastoma cell-lines. This work may have implications for therapy if ways can be found to cause in vivo differentiation of the tumour into a benign ganglioneuroma.

Effects of sodium butyrate and dimethylsulfoxide on biochemical properties of human colon cancer cells

Sodium butyrate and dimethylsulfoxide (DMSO) have marked effects on the growth, morphology, and biochemistry of two human colonic adenocarcinoma cell lines in culture. Doubling times were increased between 18% and 660% while cell viability was unaffected. Both cell lines formed colonies in soft agar in the absence of butyrate of DMSO, but no colonies were observed in the presence of these agents. However, no differences in in vivo tumorigenicities, when cells were implanted in athymic mice, were seen following treatment. Gross morphological alterations including cell enlargement, process formation, and cellular flattening occurred during culture in butyrate or DMSO. Acrylamide gel electrophoresis in sodium dodecyl sulfate revealed no change in membrane protein constituents, but autoradiographic analysis of membrane glycoproteins demonstrated differences between treated and untreated cells. Ganglioside compositions were altered, and a sialyltransferase required for the synthesis of GM3 ganglioside was elevated by butyrate. Although cytoplasmic aminooligopeptidase remained unaffected by butyrate or DMSO, brush border-associated activity was enhanced by butyrate. Alkaline phosphatase also rose dramiatically during culture in butyrate but was not enhanced by DMSO.

Compartments of tubulin and tubulin-like proteins in differentiating neubroblastoma cells

Cytoplasmic, tubular and particulate fractions of differentiating neuroblastoma cells were prepared and the tubulin together with tubulin-like proteins was measured in each cell fraction during different stages of cell differentiation. In undifferentiated cells, 73%, 5% and 22% of the tubulin and tubulin-like proteins were contained in the cytoplasmic, tubular and particulate fractions, respectively. After 5 days of differentiation, the overall content of tubulin and tubulin-like proteins had increased by 73%. This corresponded to increases of 45%, 145% and 100% in the cytoplasmic, microtubular and particulate fractions, respectively. The increase in membrane-bound (particulate) tubulin and tubulin-like proteins was significantly greater than the total increase of proteins in the particulate fraction. Polyacrylamide gel electrophoresis of the proteins in each subcellular fraction revealed the presence of protein bands corresponding to the alpha and beta subunits of tubulin. Whereas these bands indicated equal amounts of protein in the alpha and beta positions for the tubular and particulate cell fractions, an analysis of the cytoplasmic fraction revealed much more protein migrating to the alpha-tubulin position than to the beta-tubulin position, especially during cell differentiation. Furthermore, two overlapping but distinct protein bands were demonstrable in the position of the alpha-tubulin from the cytoplasmic fraction. These bands were designated alpha 1 and alpha 2. The particulate fraction contained only the alpha 1 and the tubular fraction only the alpha 2 protein band. The addition of 1 mM dibutyryl cyclic AMP to the neuroblastoma cells, at the time when the serum was withdrawn, enhanced the rate of differentiation and the redistribution of tubulin and tubulin-like proteins within the 3 cellular compartments. These results are discussed as they relate to the regulation, biosynthesis, turnover and compartmentation of tubulin and tubulin-like proteins in differentiating neuroblastoma cells.

Effects of 6-aminonicotinamide on growth and acetylcholinesterase activity during differentiation of neuroblastoma cells in vitro

Addition of 6-AN (0.01 mg/ml) to growing cultures of C-1300 neuroblastoma cells strongly reduced cell division. This growth inhibition was accompanied by a higher cell volume and a lower protein content per cell as compared to controls. Concurrently the specific activity of AChE increased markedly incontrols and 6-AN-treated cultures. During the experimental periods the specific activity of AChE was significantly higher after 6-AN. Morphologically, 6-AN-treated cultures showed characteristic signs of differentiation, i.e. enlarged, flattened cells with long branched processes. The described effect of 6-AN on growth and differentiation of neuroblastoma cells was less pronounced if cells received the antimetabolite after a subcultivation period of 5 days.

Tumor promoters inhibit morphological differentiation in cultured mouse neuroblastoma cells

When added to mouse neuroblastoma cultures, the potent tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) inhibits spontaneous neurite formation as well as that induced in response to serum deprivation, prostaglandin E1, 5-bromo-2'-deoxyuridine, and papaverine. Other tumor-promoting macrocyclic plant diterpenes also inhibit neurite formation, whereas nonpromoting diterpenes do not. Inhibition by TPA was reversible and was unrelated to toxicity.

Nuclear control of neurite induction in neuroblastoma cells

Induction of neurite formation in neuroblastoma cells by dibutyryl cyclic 3':5'-AMP (db-cAMP) or prostaglandin EI (PGE1) was enhanced after enucleation. Cells selected for resistance to db-cAMP were induced to form neurites by db-cAMP or PGE1 only after, but not before enucleation. Inhibition of protein synthesis inhibited neurite induction in nucleated, but not in enucleated cells, and enucleated cells were less sensitive to inhibition of neurite formation by concanavalin A (ConA). Colchicine, vinblastine and cytochalasin B (CB), compounds that interfere with the assembly of microtubules and microfilaments, inhibited induction in both types of cells. It is suggested that enucleation removes a nuclear inhibitor of neurite induction by db-cAMP and PGE1, and that neurite induction in nucleated cells requires that cAMP activates the assembly of microtubules and microfilaments and inactivates the nuclear inhibitor.

A comparative analysis of the protein components of plasma membranes isolated from differentiated and undifferentiated mouse neuroblastoma cells in tissue culture

The plasma membranes of the cells of mouse neuroblastoma clone NB41A, were isolated without fixation by hardening procedures and were characterised by their enzyme activities and by their morphology in the light and electron microscopes. The membranes were prepared from two kinds of differentiated monolayer cultures; one in which the cells were induced to form long axon-like processes by the addition of N6,O2'-dibutyryladenosine 3':5'-monophosphate to the culture medium, and the other in which the cells were induced to form processes by the addition of 5-bromo-2'-deoxyuridine. The proteins from the solubilised membranes were compared with similar preparation from the membranes of undifferentiated cells, grown in suspension, by sodium dodecylsulphate polyacrylamide gel electrophoresis, using the incorporation of radioactive amino acids and L-fucose into proteins in the cultures to follow the differences in the patterns of polypeptide synthesis and glycosylation of the membrane proteins. The differentiated cells induced with either inducer show an increased incorporation of L-fucose into two distinct components with molecular weights of 60 000 and 70 000. The two types of induced cells differ from each other in that N6,O2'-dibutyryladenosine 3':5'-monophosphate stimulates both glycosylation and protein synthesis, with a relative increase in the low molecular weight proteins, but 5-bromo-2'-deoxyuridine stimulates mostly increased glycosylation of the membrane proteins.

The effect of medium pH on rate of growth, neurite formation and acetylcholinesterase activity in mouse neuroblastoma cells in culture

Cell division, neurite formation and acetylcholinesterase activity were examined in a clone (NBA2) of mouse neuroblastoma cells maintained for up to 120 hours in medium with pH values between 6.6 and 8.0. Growth rate decreased as pH was reduced from 7.8 to 6.6. Generation time at pH 7.4 was 25 hours, while the rate of cell division was negligible at pH 6.6. The total number of cells at stationary phase was less at the lower pH values. Neurite formation was enhanced markedly as the pH was reduced from 7.4 to 6.6. Acetylcholinesterase activity was 5- to 8-fold greater in cells exposed to medium at pH 6.6 than in cells maintained in medium at pH 7.4. The reduction in the rate of cell division and increases in neurite formation and acetylcholinesterase activity at pH 6.6 were reversible upon exposure of the cells to pH 7.4 medium. Cell viability was greater than 90% at all medium pH values over a period of 120 hours. Uncloned T-59 mouse neuroblastoma cells were affected similarly by changes in pH. These results show that manipulation of the environmental pH can reversibly alter growth, neurite formation, and acetylcholinesterase activity of mouse neuroblastoma cells in culture.

The ultrastructure of mouse neuroblastoma cells in tissue culture

Neuroblastoma cells grown in suspension culture are round and have no distinctive structural characteristics. However, cells transferred to substrates flatten, develop long neurites, and assume the morphology of normal neurons. The resemblance of monolayered neuroblastoma cells to normal neurons is amplified by treatment with hypertonic medium; under these conditions, cell division is inhibited and the neurites become long and differentiated. The treated cells contain clusters of clear vesicles, 400-600 A in diameter, which are morphologically indistinguishable from the synaptic vesicles of normal neurons. Specialized cell contacts are observed between the treated cells as well as between confluent cells grown in normal medium.

Modulation of cell-surface antigens of a murine neuroblastoma

Antisera were produced in rabbits to morphologically differentiated cells from the C1300 murine neuroblastoma (i.e., cells in which process formation was induced by maintenance on serum-free medium for 5 days). These antisera reacted more strongly in the complement fixation reaction with such "differentiated" cells than with "undifferentiated" (nonprocess-bearing) neuroblastoma cells. Adsorption of the antisera with undifferentiated cells removed the reactivity to cells without processes, while the reactivity with serum-free cells which possess processes was retained. Indirect immunofluorescence studies confirmed the results obtained by complement fixation and demonstrated that antibodies to the surface antigens of process-bearing cells could be adsorbed by particulate preparations from brain but not liver, spleen, or kidney. This is the first description of neural-associated cell-surface changes that correlate with the morphological differentiation in culture of neuroblastoma cells.