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J C Reed

Publications and source records attributed to J C Reed.

At least 289 records · Page 16Linked to original sources
PubMed1997

BAG-1 inhibits p53-induced but not apoptin-induced apoptosis.

BAG-1 has been identified as a Bcl-2-binding protein that inhibits apoptosis, either alone or in co-operation with Bcl-2. Here we show that BAG-1 inhibits p53- induced apoptosis in the human tumour cell line Saos-2. In contrast, BAG-1 was unable to inhibit the p53-independent pathway induced by apoptin, an apoptosis-inducing protein derived from chicken anaemia virus. Whereas BAG-1 seemed to co-operate with Bcl-2 to repress p53-induced apoptosis, co-expression of these proteins had no inhibitory effect on apoptin-induced apoptosis. Moreover, Bcl-2, and to some extent also BAG-1, paradoxically enhanced the apoptotic activity of apoptin. These results demonstrate that p53 and apoptin induce apoptosis through independent pathways, which are differentially regulated by BAG-1 and Bcl-2.

Journal Article↗
PubMed1997

Butyrate-induced reversal of dexamethasone resistance in autonomous rat Nb2 lymphoma cells.

The parental rat Nb2 lymphoma is a prolactin (PRL)-dependent T cell line. Exposure of a PRL-independent subline, Nb2-SFJCD1, to sodium butyrate (NaBT) causes transient reversal of their growth factor-independent proliferation in association with constitutive expression of protooncogenes pim-1 and c-myc. In the present study, we investigated the effect of NaBT treatment on the sensitivity of Nb2-SFJCD1 cells to dexamethasone (DEX)-induced apoptosis. Pretreatment with NaBT (2 mM, 72 h) partially reversed resistance to apoptosis in Nb2-SFJCD1 cells exposed to DEX (100 nM) for 12 h, assessed by flow cytometric analyses of DNA fragmentation. However, the cytolytic effect of DEX was abrogated by PRL in a time- and concentration-dependent manner. Evaluation of apoptosis-associated gene expression in NaBT-pre-treated cultures incubated with DEX or DEX+PRL indicated that the apoptosis resistance did not stem from altered bcl-2 or bax expression. However, there was a strong correlation between the resistance to DEX-activated apoptosis and their enhanced expression of pim-1 mRNA and protein. The results show that it is possible to reverse DEX-induced apoptosis of Nb2 pre-T cells and suggest the pim-1 gene product has an important role as a suppressor of this process, perhaps functioning as a mediator of PRL action.

Journal Article↗
PubMed1997

Role of apoptosis and apoptosis-related proteins in the cisplatin-resistant phenotype of human tumor cell lines.

Since apoptosis is the primary mode of cell death induced by cisplatin, the role of apoptosis and apoptosis-related gene products in cisplatin resistance was investigated in four human cisplatin-resistant cell lines of different tumour type. A common feature of the resistant sublines was a reduced susceptibility to drug-induced apoptosis compared to parental sensitive lines. Loss of wild-type p53 function was not a general event associated with the development of drug resistance. An increased bcl-2 expression was found in resistant cells characterized by mutant p53 (A431/Pt and IGROV-1/Pt), whereas in osteosarcoma (U2-OS/Pt) and in ovarian carcinoma (A2780/CP) cells with wild-type p53, bcl-2 levels were markedly reduced. U2-OS/Pt cells had a 16-fold increase in the level of Bcl-xL protein. Stable transfection of U2-OS cells with bcl-xL cDNA conferred a low level of drug resistance to cisplatin, suggesting that overexpression of this gene contributes to the cisplatin-resistant phenotype of this osteosarcoma cell system. In conclusion, these observations suggest a variable contribution of apoptosis-related genes to cisplatin resistance depending on the biological background of the cell system and presumably reflecting different pathways of apoptosis.

Journal Article↗
PubMed1997

Spontaneous overexpression of the long form of the Bcl-X protein in a highly resistant P388 leukaemia.

A novel resistant variant of murine P388 leukaemia, P388/SPR, was identified by de novo resistance to doxorubicin (DOX) in vivo. This mutant displayed a similar level of cross-resistance to etoposide (VP-16) and other topoisomerase II (topo II) inhibitors. Further analysis of the phenotype revealed a broad cross-resistance to vinca alkaloids, alkylating agents, antimetabolites, aphidicolin and UV light. Low-level expression of mdr1 and P-glycoprotein (P-gp), as well as a modest impairment of cellular drug accumulation and partial reversion of resistance to DOX and VP-16 by cyclosporine, confirmed a moderate role of P-gp in conferring drug resistance in P388/SPR cells. Consistent changes in neither topo II expression or activity nor glutathione metabolism could be detected. Induction of apoptosis was significantly reduced in P388/SPR cells, as indicated by minimal DNA fragmentation. Analysis of oncogenes regulating apoptotic cell death revealed a marked decrease of bcl-2 in combination with a moderate reduction of bax protein, but a striking overexpression of the long form of the bcl-X protein. Transfection of human bcl-X-L into P388 cells conferred drug resistance similar to that of P388/SPR cells. The data suggest that overexpression of bcl-X-L results in an unusual phenotype with broad cross-resistance to non-MDR-related cytotoxins in vitro, and provide an interesting example of spontaneous overexpression of another member of the bcl-2 gene family in cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Bcl-2 acts upstream of the PARP protease and prevents its activation.

Apoptosis has recently been extensively studied and multiple factors have been implicated in its regulation. It remains unclear how these factors are ordered in the cell death pathway. Here we investigate the relationship between the inhibitor of apoptosis, bcl-2, and the PARP protease, prlCE/CPP32, recently implicated in apoptosis. Using PARP proteolysis as an indicator of the activation of the PARP protease, we find that the chemotherapeutic agent, etoposide, induces apoptosis and PARP proteolysis in Molt4 cells as early as 4 h with cell death lagging behind this event. In contrast, Molt4 cells that over-express bcl-2 show no PARP proteolysis or cell death. In order to determine if bcl-2 inhibits the PARP protease or its activation, we developed a cell-free system. Using this system with extracts from etoposide-treated cells and purified bovine PARP, we demonstrate that extracts from bcl-2 over-expressing cells cause little or no PARP proteolysis. Whereas, extracts from control vector cells contain an active PARP protease. This protease is inhibited by the tetrapeptide ICE-like protease inhibitor, YVAD-chloromethylketone. Interestingly, this protease is not inhibited by the addition of purified bcl-2 protein. These results rule out that bcl-2 directly inhibits the active protease or that it has an effect downstream of prlCE/CPP32 such as preventing access to the PARP substrate. These results also demonstrate a role of bcl-2 in interfering with an upstream signal required to activate the PARP protease and allow us to begin to order the components in the apoptotic pathway.

Journal Article↗
PubMed1997

Modulation of the expression of Bcl-2 and related proteins in human leukemia cells by protein kinase C activators: relationship to effects on 1-[beta-D-arabinofuranosyl]cytosine-induced apoptosis.

We have previously reported that pretreatment of HL-60 human promyelocytic leukemia cells with the non-tumor-promoting protein kinase C (PKC) activator bryostatin 1 potentiates induction of apoptosis by the antimetabolite 1-[beta-D-arabinofuranosyl]cytosine (ara-C) (Biochem Pharmacol 47:839,1994). To determine whether this phenomenon results from altered expression of Bcl-2 or related proteins, Northern and Western analysis was employed to assess the effects of bryostatin 1 and other PKC activators on steady-state levels of Bcl-2, Bax, Bcl-x, and Mcl-1 mRNA and protein. Pretreatment of cells for 24 h with 10 nM bryostatin 1, or, to a lesser extent, the stage-1 tumor-promoter phorbol dibutyrate (PDB) significantly potentiated apoptosis induced by ara-C (100 microM; 6 h); in contrast, equivalent exposure to the stage-2 tumor promoter, mezerein (MZN), which, unlike bryostatin 1, is a potent inducer of differentiation in this cell line, failed to modify ara-C-related cell death. Neither bryostatin 1 nor PDB altered expression of bcl-2/Bcl-2 over this time frame. In contrast, MZN down-regulated bcl-2 mRNA levels, but this effect was not accompanied by altered expression of Bcl-2 protein. None of the PKC activators modified expression of Bax or Bcl-x(L) mRNA or protein; levels of Bcl-x(S) were undetectable in both treated and untreated cells. However, expression of Mcl-1 mRNA and protein increased modestly after treatment with either bryostatin 1 or PDB, and to a greater extent following exposure to MZN. Combined treatment of cells with bryostatin 1 and MZN resulted in undiminished potentiation of ara-C-mediated apoptosis and by antagonism of cellular maturation. These effects were accompanied by unaltered expression of Bcl-2, Bax, and Bcl-x(L), and by a further increase in Mcl-1 protein levels. When cells were co-incubated with bryostatin 1 and calcium ionophore (A23187), an identical pattern of expression of Bcl-2 family members was observed, despite the loss of bryostatin 1's capacity to potentiate apoptosis, and the restoration of its ability to induce differentiation. Finally, treatment of cells with bryostatin 1+/-ara-C (but not ara-C alone) resulted in a diffuse broadening of the Bcl-2 protein band, whereas exposure of cells to taxol (250 nM, 6 h) led to the appearance of a distinct Bcl-2 species with reduced mobility, phenomena compatible with protein phosphorylation. Together, these findings indicate that the ability of bryostatin 1 to facilitate drug-induced apoptosis in human myeloid leukemia cells involves factors other than quantitative changes in the expression of Bcl-2 family members, and raise the possibility that qualitative alterations in the Bcl-2 protein, such as phosphorylation status, may contribute to this capacity. They also suggest that increased expression of Mcl-1 occurs early in the pre-commitment stage of myeloid cell differentiation, and that this event does not protect cells from drug-induced apoptosis.

Journal Article↗
PubMed1997

Co-expression of several molecular mechanisms of multidrug resistance and their significance for paclitaxel cytotoxicity in human AML HL-60 cells.

Overexpression of P-glycoprotein (PGP), MRP or LRP has been characterized as the 'proximal', while overexpression of the anti-apoptosis Bcl-2 or Bcl-xL relative to the pro-apoptosis Bax protein has been recognized as the 'distal' mechanism of multidrug resistance in human AML cells. In the present studies, we examined whether these mechanisms can co-exist in human AML HL-60 cells. We also determined how these mechanisms would affect the accumulation and cytotoxicity of a PGP substrate, such as Taxol (paclitaxel). For this, immunoblot analyses were performed to determine the expression of PGP, MRP, Myc, Bcl-2, Bcl-xL and Bax on either the multidrug-resistant HL-60 sublines created under the selection pressure of doxorubicin (HL-60/AR), paclitaxel (HL-60/TAX1000) or vincristine (HL-60/VCR), or sublines created by transfection and overexpression of the bcl-2 (HL-60/Bcl-2) or bcl-xL gene (HL-60/Bcl-xL). As compared to the control HL-60, HL-60/AR cells possess high MRP while HL-60/TAX1000 and HL-60/VCR cells express high levels of the mdr-1 encoded PGP. In addition, these multidrug-resistant cells possess 1.5- to 2.5-fold higher Bcl-2, while their Bax and Myc levels are similar to those in the control HL-60 cells. HL-60/TAX1000 and HL-60/VCR cells also express three- and 2.5-fold higher Bcl-xL levels. PGP, but not MRP, overexpression significantly impaired paclitaxel accumulation and paclitaxel-induced apoptosis, as well as reduced its cytotoxic effects as determined by the MTT assay. In contrast, enforced and much higher expression of Bcl-2 in HL-60/Bcl-2 (five-fold) or Bcl-xL in HL-60/Bcl-xL cells (10-fold) significantly reduced paclitaxel-induced apoptosis and the loss of cell viability, without affecting its intracellular accumulation. These results confirm the possibility of co-expression of multiple mechanisms of multidrug resistance in human leukemic cells which had been selected by exposure to a single drug. The results also indicate that MRP overexpression does not confer resistance against paclitaxel. In addition, these findings suggest that, for Bcl-2 and Bcl-xL, enforced overexpression to high levels is necessary to induce paclitaxel resistance in HL-60 cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Cooperative interception of neuronal apoptosis by BCL-2 and BAG-1 expression: prevention of caspase activation and reduced production of reactive oxygen species.

Neuronally differentiated PC12 cells undergo synchronous apoptosis when deprived of nerve growth factor (NGF). Here we show that NGF withdrawal induces actinomycin D- and cycloheximide-sensitive caspase (ICE-like) activity. The peptide inhibitor of caspase activity, N-acetyl-Asp-Glu-Val-Asp-aldehyde, was more potent than acetyl-Tyr-Val-Ala-Asp-chloromethyl ketone in preventing NGF withdrawal-induced apoptosis, suggesting an important role for caspase-3 (CPP32)-like proteases. We observed a peak of reactive oxygen species (ROS) 6 h after NGF withdrawal. ROS appear to be required for apoptosis, because cell death is prevented by the free radical spin trap, N-tert-butyl-alpha-phenylnitrone, and the antioxidant, N-acetylcysteine. ROS production was blocked by actinomycin D, cycloheximide, and caspase protease inhibitors, suggesting that ROS generation is downstream of new mRNA and protein synthesis and activation of caspases. Forced expression of either BCL-2 or the BCL-2-binding protein BAG-1 blocked NGF withdrawal-induced apoptosis, activation of caspases, and ROS generation, showing that they function upstream of caspases. Coexpression of BCL-2 and BAG-1 was more protective than expression of either protein alone.

Animals↗
PubMed1997

Bax- and Bak-induced cell death in the fission yeast Schizosaccharomyces pombe.

The effects of the expression of the human Bcl-2 family proteins Bax, Bak, Bcl-2, and Bcl-XL were examined in the fission yeast Schizosaccharomyces pombe and compared with Bax-induced cell death in mammalian cells. Expression of the proapoptotic proteins Bax and Bak conferred a lethal phenotype in this yeast, which was strongly suppressed by coexpression of the anti-apoptotic protein Bcl-XL. Bcl-2 also partially abrogated Bax-mediated cytotoxicity in S. pombe, whereas a mutant of Bcl-2 (Gly145Ala) that fails to heterodimerize with Bax or block apoptosis in mammalian cells was inactive. However, other features distinguished Bax- and Bak-induced death in S. pombe from animal cell apoptosis. Electron microscopic analysis of S. pombe cells dying in response to Bax or Bak expression demonstrated massive cytosolic vacuolization and multifocal nuclear chromatin condensation, thus distinguishing this form of cell death from the classical morphological features of apoptosis seen in animal cells. Unlike Bax-induced apoptosis in 293 cells that led to the induction of interleukin-1 beta-converting enzyme (ICE)/CED-3-like protease activity, Bax- and Bak-induced cell death in S. pombe was accompanied neither by internucleosomal DNA fragmentation nor by activation of proteases with specificities similar to the ICE/CED-3 family. In addition, the baculovirus protease inhibitor p35, which is a potent inhibitor of ICE/CED-3 family proteases and a blocker of apoptosis in animal cells, failed to prevent cell death induction by Bax or Bak in fission yeast, whereas p35 inhibited Bax-induced cell death in mammalian cells. Taken together, these findings suggest that Bcl-2 family proteins may retain an evolutionarily conserved ability to regulate cell survival and death but also indicate differences in the downstream events that are activated by overexpression of Bax or Bak in divergent cell types.

Apoptosis↗
PubMed1997

Role of antioxidants and intracellular free radicals in retinamide-induced cell death.

The cancer chemopreventive synthetic retinoid N-(4-hydroxyphenyl)retinamide (HPR) possesses antiproliferative and apoptotic activity at pharmacological doses. In this study we show that addition of antioxidants to HL-60 cells cultured in the presence of 3 microM HPR, markedly suppresses the apoptopic effect of the retinoid and significantly prolongs cell survival (48-96 h). We also show, by the use of the oxidation-sensitive probe 2',7'-dichlorofluorescin diacetate (DCF-DA) and in combination with flow cytometric and spectrofluorimetric analysis, that treatment of cells with 3 microM HPR results in an immediate and sustained production of intracellular free radicals, most likely hydroperoxides. Interestingly, the formation of these HPR-induced free radicals is effectively blocked by the water soluble antioxidants L-ascorbic acid and N-acetyl-L-cysteine. Neither 3-15 microM N-(4-methoxyphenyl) retinamide (MPR), the structurally similar but biologically inert analog of HPR, nor 3 microM doses of the retinoids all-trans retinoic acid, 9-cis-retinoic acid, TTNPB and SR11237 induce intracellular free radicals, thus indicating that the specificity of this phenomenon is restricted to HPR. Altogether, we provide the first direct evidence that HPR stimulates the generation of intracellular free radicals, which appear to have a causative role in the induction of apoptosis in vitro. Our findings raise the possibility that the therapeutic efficacy of HPR may, at least in part, depend on these apoptosis-inducing oxidative phenomena.

Antioxidants↗
PubMed1997

Apoptosis in Xenopus tadpole tail muscles involves Bax-dependent pathways.

Apoptosis is a fundamental mechanism implicated in normal development. One of the most spectacular developmental events involving apoptosis is tail regression during amphibian metamorphosis. We analyzed how thyroid hormone (3, 5, 3'-triiodothyronine, T3), the orchestrator of metamorphosis, affects expression and function of the proapoptotic gene Bax in the tail muscle of free-living Xenopus tadpoles. During natural metamorphosis Bax mRNA was expressed in tail muscles and was spatially correlated with apoptosis. Precocious treatment of tadpoles with T3 induced Bax expression and apoptosis. To verify that Bax expression was causally related to apoptosis we used a naked DNA gene transfer method to express Bax in the dorsal tail muscle. This induced apoptosis, and the process was exacerbated by T3 treatment. To determine whether T3 effects on Bax expression involved transcriptional regulation, we injected a Bax promoter sequence into dorsal and caudal tail muscles. In the dorsal muscle, T3 treatment did not affect transcription from the Bax promoter. However, in the caudal muscle, T3 treatment significantly increased Bax transcription. We conclude that T3-induced apoptosis in Xenopus tadpole tail muscles involves Bax-activating and Bax-synergis tic mechanisms. These programs are induced in spatially and temporally distinct manners.

Animals↗
PubMed1997

Resistance to apoptosis and up regulation of Bcl-2 in benign prostatic hyperplasia after androgen deprivation.

PURPOSE: Benign prostatic hyperplasia (BPH) is related to advancing age and the presence of androgens and occurs in virtually all older men. BPH causes morbidity, most often by urinary obstruction, in a substantial fraction of men over sixty. Both finasteride and androgen ablation induce partial diminution in BPH that occurs over weeks to months. This is in contrast to the often rapid involution seen in both normal prostatic epithelium and prostatic carcinoma in response to androgen withdrawal. This study was performed to analyze the response of prostatic cells, and in particular BPH, to acute androgen ablation. MATERIALS AND METHODS: We subjected a cohort of 26 men to androgen ablation with goserelin, a gonadotrophin releasing hormone agonist, for 3-4 weeks prior to radical prostatectomy for prostate cancer. Preablation biopsy specimens and prostatectomy specimens were immunohistochemically stained for apoptotic cells and for expression of apoptosis regulatory proteins Bcl-2, Bax, Bcl-x, and Bak. RESULTS: Normal prostatic epithelial cells and prostate cancer responded to hormone deprivation by undergoing apoptosis, but in 19/26 specimens prostatic hyperplasia had a total absence of apoptosis. In all 26 specimens, benign prostatic hyperplasia demonstrated increased expression of the Bcl-2 protein, but no change in the expression of Bax, Bcl-x, and Bak. In contrast, adjacent normal and malignant prostatic epithelium showed positive staining for apoptosis and did not alter Bcl-2 expression in response to androgen ablation. CONCLUSIONS: BPH demonstrated increased staining for Bcl-2 after androgen deprivation that may render hyperplastic epithelium relatively resistant to apoptosis induced acutely by androgen withdrawal.

Apoptosis↗
PubMed1997

Up-regulation of Bax protein in degenerating retinal ganglion cells precedes apoptotic cell death after optic nerve lesion in the rat.

Retrograde degeneration of retinal ganglion cells as a consequence of optic nerve lesion has been shown to fulfil the criteria of apoptosis. In the present study, we investigated the time course of ganglion cell apoptosis following intraorbital crushing of the optic nerve in adult rats using morphological criteria and applying a terminal transferase technique (TUNEL) for in situ detection of DNA strand breaks. In addition, we examined expression patterns of the anti-apoptotic proteins Bcl-2 and Bcl-X and the cell death-promoting protein Bax in retinae after crushing the optic nerve. Apoptotic nuclei were detected in the ganglion cell layer in the first 3 weeks after optic nerve crush, with a peak after 6 days. Bcl-2 and Bcl-X proteins were expressed in ganglion cells at low levels. Expression of Bcl-2 decreased further during the days following crush. Bcl-X expression was initially increased, followed by a decline over the following days. In contrast, Bax protein, which was expressed in most ganglion cells at moderate baseline levels, was sharply increased as early as 30 min after crush, reached peak levels after 3 days, and remained up-regulated for at least 1 week thereafter. Double labelling for Bax and TUNEL in retinal sections, however, did not reveal colocalization of the two signals in individual retinal ganglion cells, consistent with the idea that increases in Bax precede apoptosis after optic nerve lesion. Thus, retinal ganglion cell death might be prevented by ablation of Bax protein in these cells, or by up-regulation of Bax-antagonists such as Bcl-2 or Bcl-X.

Animals↗
PubMed1997

Differential expression of members of the bcl-2 gene family in proliferative and secretory human endometrium: glandular epithelial cell apoptosis is associated with increased expression of bax.

Glandular epithelial cells of the human endometrium initiate apoptosis in the secretory phase of the cycle. To better understand the regulation of apoptosis in this paradigm of endocrine-regulated cell turnover, we studied the expression of the cell death regulatory genes, bax, bcl-2, and bcl-x, in human proliferative and secretory endometria relative to the absence or presence of apoptosis. As assessed by immunohistochemistry, levels of BAX protein were modest in proliferative endometrium and increased dramatically in the secretory phase when apoptosis was most prevalent. Expression of BAX was predominantly localized to epithelial cells of the functionalis layer of the secretory endometrium. In contrast, BCL-2 immunoreactivity was maximal during the proliferative phase and decreased in the secretory phase. Moreover, BCL-2 was topographically concentrated in the basalis layer. Immunoreactive BCL-X protein was observed mostly in glandular epithelial cells of the human endometrium. Compared with proliferative endometrium, secretory endometrium showed stronger BCL-X staining, especially in the functionalis layer. By Western blotting we confirmed that both proliferative and secretory endometrium expressed the long or antiapoptosis form as well as the short or proapoptosis form of the BCL-X protein. Taken together, our results demonstrate a coordinated pattern of expression of bcl-2 gene family members in human endometrium during the menstrual cycle, with a shift toward greater levels of the proapoptosis protein, BAX, occurring in glandular epithelial cells during the secretory phase of the cycle. Therefore, we conclude that cyclic changes in endometrial growth and regression may be precisely regulated by shifts in the ratio or balance of BCL-2 and related proteins in glandular epithelial cells.

Apoptosis↗
PubMed1997

Role of Bag-1 in the survival and proliferation of the cytokine-dependent lymphocyte lines, Ba/F3 and Nb2.

The expression and function of the newly identified Bcl-2- and Raf-1- binding protein, Bag-1, during the cytokine-regulated growth of B and T cell lines was examined. Immunoblot analysis of lysates from the interleukin-3 (IL-3)-dependent B cell line Ba/F3, and the PRL-dependent T cell line Nb2, revealed that variations in Bag-1 levels paralleled alterations in cellular proliferation, viability, and apoptosis induced by the presence or absence of growth factor. To test whether up-regulation of Bag-1 levels altered cellular survival and proliferation, Ba/F3 cells were transfected with a Bag-1 expression construct. The overexpression of Bag-1 in transfected Ba/F3 cells induced an IL-3-independent state. Such transfectants demonstrated sustained viability and proliferation, with minimal apoptosis, in the complete absence of exogenous IL-3. Bag-1 expression was also compared in glucocorticoid-sensitive Nb2 cells and a PRL-independent, glucocorticoid-resistant subline, SFJCD1, during culture of these lines in dexamethasone (Dex). Bag-1 levels were profoundly decreased by the addition of Dex to Nb2 cells, precedent to the onset of apoptotic cell death. In contrast, Dex treatment or PRL withdrawal had no effect on levels of Bag-1 within the SFJCD1 line. These findings establish that the overexpression of Bag-1 in the appropriate cellular context promotes cellular survival and growth, events that may result from the juxtaposition of this protein with mitogenic and antiapoptotic signaling pathways.

Animals↗
PubMed1997

Immunohistochemical analysis of Bcl-2, Bcl-X, Mcl-1, and Bax in tumors of central and peripheral nervous system origin.

The expression of Bcl-2, Bcl-X, Mcl-1, and Bax was examined by immunohistochemical methods in 93 tumors of nervous system origin, including 49 gliomas (30 astrocytomas and 19 glioblastoma multiforme (GMs)), 16 medulloblastomas (MBs), 19 neuroblastomas (NBs; 9 undifferentiated and 10 differentiated), and 9 miscellaneous neuroectodermal neoplasms. Among the 49 gliomas, immunopositivity (defined as > or = 10%) was observed for Bcl-2 in 45 (92%), Bcl-X in 48 (98%), Mcl-1 in 49 (100%), and Bax in 48 (98%) of 49 specimens. In 11 (37%) of 30 astrocytomas (WHO grades I to III), the tumor specimens were composed predominantly of malignant cells with strong-intensity Bcl-2 immunostaining, whereas none of the 19 GMs (WHO grade IV) exhibited strong-intensity Bcl-2 immunoreactivity (P = 0.001). Similarly, Mcl-1 immunointensity was strong in 15 (50%) of 30 astrocytomas, compared with only 2 (11%) of 19 GMs (P = 0.005). The percentage of Mcl-1-immunopositive tumor cells was also higher in astrocytomas than GMs (P < 0.002). Thus, contrary to a priori expectations, the expression of the anti-apoptotic proteins Bcl-2 and Mcl-1 was significantly higher in astrocytomas than in GMs. Of the 16 MBs, immunopositivity was found for Bcl-2 in 4 (25%), Bcl-X in 9 (56%), Mcl-1 in 8 (50%), and Bax in 16 (100%) of the cases. The intensity of immunostaining was strong for Bcl-2 in only 1 (6%) specimen, for Bcl-X in 3 (19%), and for Mcl-1 in 2 (12.5%), in contrast to Bax immunostaining, which was strong in 12 (75%) tumors. Significantly higher percentages of Bax-immunopositive tumor cells were also found in MBs, compared with Bcl-2, Bcl-X, and Mcl-1 (P < 0.0001). All 19 NBs were immunopositive for Bcl-2, Bcl-X, Mcl-1, and Bax. Higher percentages of Bcl-X- and Mcl-1-immunopositive tumor cells were observed in well differentiated tumors (P = 0.04 and 0.004, respectively). The intensity of Mcl-1 immunostaining was also generally higher in differentiated than undifferentiated NBs (strong immunointensity in 7 of 10 versus 0 of 9; P = 0.002). Conversely, strong-intensity Bax immunostaining was associated with undifferentiated histology (5 of 9 (56%) versus 1 of 10 (10%); P = 0.03). Taken together, these findings begin to delineate trends in the regulation of the relative levels of the Bcl-2 family proteins, Bcl-2, Bcl-X, Mcl-1, and Bax in gliomas, MBs, NBs, and some of their histological subtypes. The suggestion that expression of some of these Bcl-2 family genes may be differentially regulated in association with tumor progression and differentiation provides insights into the diverse biology and clinical behavior of these tumors of nervous system origin.

Central Nervous System Neoplasms↗