Tumor cell proliferation and apoptosis in medulloblastoma

Prognostic Factors in Adult Medulloblastoma. A Clinico-Pathologic Study

Aims and background.

Medulloblastoma in adults is a rare tumor. The small number of cases in the reported series has not permitted a definite assessment of the prognostic role of clinical, pathologic and cell kinetics factors. The largest series of medulloblastoma in adults treated in a single institution is herein reported.

Methods.

The clinical, therapeutic, pathologic and proliferation features of medulloblastoma in 44 adult patients (> 18 years) were analyzed retrospectively with regard to postoperative survival. The proliferation potential of each tumor was evaluated by the immunohistochemical demonstration of proliferating cell nuclear antigen (PCNA) and Ki-67, clone MIB-1, in paraffin sections.

Results.

The overall 5- and 10-year survival rates were 40% and 35.6%, respectively. Significant factors in predicting a longer postoperative survival were: age < 37 years, decade of management (1977-1990), radiotherapy (50-55 Gy on the posterior fossa and 30-35 Gy on the spinal cord) and nuclear isomorphism. When corrected for adequacy of radiotreatment, desmoplastic type and differentiation were significantly correlated with a shorter survival. The PCNA-labelling index (LI) ranged from 34.5 to 82.2%, the MIB-1-LI ranged from 9.6 to 64.7%. No association was found between PCNA- or MIB-1-LI values and microscopic features, or between LI values and prognosis.

Conclusions.

Contrary to a general assumption, desmoplastic medulloblastoma and differentiated medulloblastoma are negative prognostic factors in adequately radiotreated adult patients. This may possibly be referred to lower radiosensitivity of these tumor variants. The LI with PCNA or Ki-67 is of no help in identifying aggressive tumors.

An essential role for p38 MAPK in cerebellar granule neuron precursor proliferation

Development of the cerebellum occurs postnatally and is marked by a rapid proliferation of cerebellar granule neuron precursors (CGNPs). CGNPs are the cells of origin for SHH-driven medulloblastoma, the most common malignant brain tumor in children. Here, we investigated the role of ERK, JNK, and p38 mitogen-activated protein kinases in CGNP proliferation. We found high levels of p38α in proliferating CGNPs. Concomitantly, members of the p38 pathway, such as ASK1, MKK3 and ATF-2, were also elevated. Inhibition of the Shh pathway or CGNP proliferation blunts p38α levels, irrespective of Shh treatment. Strikingly, p38α levels were high in vivo in the external granule layer of the postnatal cerebellum, Shh-dependent mouse medulloblastomas and human medulloblastomas of the SHH subtype. Finally, knocking down p38α by short hairpin RNA-carrying lentiviruses as well as the pharmacologically inhibiting of its kinase activity caused a marked decrease in CGNP proliferation, underscoring its requirement for Shh-dependent proliferation in CGNPs. The inhibition of p38α also caused a decrease in Gli1 and N-myc transcript levels, consistent with reduced proliferation. These findings suggest p38 inhibition as a potential way to increase the efficacy of treatments available for malignancies associated with deregulated SHH signaling, such as basal cell carcinoma and medulloblastoma.

Double high-dose chemotherapy followed by autologous peripheral blood stem cell transplantation for primary disseminated medulloblastoma: a report of 3 cases

We performed double high-dose chemotherapy followed by peripheral blood stem cell transplantation (PBSCT) in 3 children with medulloblastoma and primary leptomeningial dissemination, including spinal metastasis. After resection of the main tumor mass, 30.6 Gy whole craniospinal radiation therapy and 4 or 5 courses of conventional chemotherapy with vincristine (1.5 mg/m), carboplatin (560 mg/m), ifosfamide (9000 mg/m), and etoposide (500 mg/m), and 2 courses of high-dose thiotepa (680 mg/m) and melphalan (240 mg/m) therapy with PBSCT were administered. Two patients with low erythroblastic leukemia viral oncogene homolog 2 (ERBB2) gene expression achieved long-term survival (41 mo and 40 mo) but the patient with high ERBB2 expression relapsed 9 months after the second PBSCT.

Medulloblastomas: a correlative study of MIB-1 proliferation index along with expression of c-Myc, ERBB2, and anti-apoptotic proteins along with histological typing and clinical outcome

BACKGROUND

Medulloblastoma (MB) is the most common pediatric brain tumor. It is however rare in adults. The genetic and protein expression profile of medulloblastoma is complex, which is worthwhile in terms of prognostication and development or selection of targeted therapy.

AIMS AND OBJECTIVES

The aims and objectives to correlate the MIB-1 proliferation index and protein expression profiles of c-Myc, ERBB2, and anti-apoptotic proteins (Bcl2 and Bcl-xL) in tumor cells with histological subtypes and clinical outcome.

METHODS AND MATERIAL

In 50 cases, histopathological subtyping was done, and protein expression profiling by immunohistochemical technique was performed by stains for MIB-1, Bcl2, Bcl-xL, c-Myc, and ERBB2 in 30 cases. The findings were correlated with histological types and patient's average follow-up data.

RESULTS

Histological subtypes were similar to that described in literatures. The average expression of Bcl2, Bcl-xL, MIB-1, c-Myc, and ERBB2 were as follows: 50.38%, 38.18%, 59.03%, 46.16%, and 59.62%, respectively. Bcl2 expression showed statistically significant correlation with progress-free survival (PFS) [p = 0.046], while ERBB2 and MIB-1 showed a trend of higher expression in progressive disease. The protein expression pattern did not correlate with histological subtypes.

CONCLUSION

Though Bcl-2, ERBB2, and MIB-1 LI came out to be potential markers of aggressive behavior, c-Myc did not correlate with PFS in MB.

Medulloblastoma: clinicopathologic evaluation of 42 pediatric cases

PURPOSE

The aim of this study was to assess the prognostic value of MIB-1 and p53 in the pediatric medulloblastoma group.

MATERIALS AND METHOD

Forty-two pediatric medulloblastoma cases diagnosed in a single institution during the past 10 years were evaluated. Follow-up data were available for 35 patients.

RESULTS

The immunoreactivity of MIB-1 ranged from 10% to 95%; p53 immunoreactivity was found in five cases. Of the 35 patients with follow-up, 34 patients received a combination of chemotherapy and radiotherapy, while one received chemotherapy alone. The follow-up period ranged from 5 to 64 months. Of the 35 patients, 21 were alive without any evidence of recurrent disease, three were alive with evidence of recurrent disease and 11 died of disease during follow-up. The mean survival for these 11 patients was 21.9+/-10.4 months. Of the 35 cases, 16 had MIB-1 value of 25% or lower and 19 had a value of 26% or more. Of the 16 cases with low MIB-1 value, six died of disease; of the 19 cases with high MIB-1 value, five died of disease. The statistical difference between MIB-1 and prognosis was not significant. Three of the 35 (8.5%) cases were found to be positive with p53 protein; no correlation was observed between p53 immunoreactivity and prognosis.

CONCLUSION

It appears that the MIB-1 value and p53 immunoreactivity have no relation with prognosis in pediatric medulloblastomas. However, it is convenient to support these findings with large series.

Primitive neuroectodermal tumors of the central nervous system

Controversial issues relating to the pathobiology and classification of central nervous system primitive neuroectodermal tumors (PNETs) have plagued neuropathologists for more than 70 years. Hypotheses advanced in the mid-1920's have remained as fixed concepts in contemporary literature, largely consequent to repetitious support by a small number of neuropathologists despite a growing body of information discrediting these ideas from neuroembryologists, oncologists, neuroscientists and pathologists. Attention has largely focused upon PNETs arising in the cerebellum (commonly known as medulloblastomas ([MBs]), because about 80% of central nervous system (CNS) PNETs originate in this site. It has been asserted that the 20% which do not are biologically different, although most individuals agree that the histological features of PNETs that occur in different sites throughout the CNS are indistinguishable from those growing in the cerebellum. The historical aspects of this controversy are examined in the face of evidence that there is, in fact, a unique class of CNS tumors which should appropriately be regarded as primitive neuroectodermal in nature. Specifically, a number of different approaches to the problem have yielded data supporting this hypothesis. These approaches include the identification of patterns of expression among a variety of cellular antigens (demonstrated by the use of immunopathological techniques), molecular analyses of cell lines derived from these tumors, experimental production of PNETs and molecular genetic analyses. Differences of opinion among surgeons, oncologists and radiotherapists are typically resolved by conducting cooperative studies of patients with these tumors who are diagnosed and treated at multiple centers.

Hedgehog signaling promotes medulloblastoma survival via Bc/II

Activation of the Hedgehog (Hh) pathway has been identified in several cancers, including medulloblastoma, but the mechanisms by which this pathway affects tumor survival and growth are incompletely understood. We investigated whether Hedgehog might promote survival of medulloblastoma cells via up-regulation of BclII. We found that mRNA levels of the Hedgehog pathway effector Gli1 were significantly associated with BclII expression in medulloblastoma and that Gli1 and BclII are both present in regions of decreased apoptosis in nodular medulloblastoma. Transient overexpression of Gli1 and Gli2 in medulloblastoma cultures induced a BclII transcriptional reporter and increased BclII protein levels, whereas stable overexpression of Gli1 was associated with increased BclII mRNA. The Hedgehog antagonist cyclopamine blocked expression of the Hh pathway targets PTCH1 and Gli1, lowered BclII levels, and increased apoptosis in DAOY and UW228 medulloblastoma cells. Apoptotic induction caused by cyclopamine could be rescued in part by enforced expression of Gli1 or BclII. Hh pathway blockade also sensitized medulloblastoma to the effects of the proapoptotic agent lovastatin. These data demonstrate that BclII is an important mediator of Hh activity in medulloblastoma and suggest new strategies for combined chemotherapeutic regimens.

Immunohistochemical analysis for histopathological subtypes in pediatric medulloblastomas

Medulloblastomas occurring in children represent a histological spectrum of varying anaplasia and nodularity. In order to determine whether immunohistochemical markers might be useful parameters in subclassifying these tumors, 17 pediatric medulloblastomas, including nine diffuse/non-anaplastic, four diffuse/anaplastic, three nodular/non-anaplastic and one nodular/anaplastic subtypes, were studied. In the present report, we investigate the expression of neural cell adhesion molecule (NCAM), nerve growth factor receptor (NGFR), neurofilament (NF), synaptophysin (SYN), glial fibrillary acidic protein (GFAP), S100, Bcl-2, and Ki-67 by using the immunohistochemistry against specific antibodies. This study showed that NGFR, NF, GFAP and S100 were not detected in anaplastic subtypes of medulloblastomas (0/5), while non-anaplastic subtypes were mainly expressed within the nodules. All 17 tumors were reactive for NCAM, SYN and Bcl-2. In addition, Ki-67 labeling indices for anaplastic subtypes (39.0 +/- 7.42%) were significantly higher than that of non-anaplastic medulloblastomas (11.4 +/- 8.04%; P < 0.0001). These results suggest that immunohistochemical markers are a useful adjunct in characterizing subtypes of pediatric medulloblastomas.

Molecular studies in pediatric medulloblastomas

Ten pediatric medulloblastoma patients were analyzed for DNA content, cell cycle, expression of drug resistance, apoptosis, cell proliferation, and N-myc genes to determine their prognostic significance. Medulloblastoma patients with progressive disease had fourth ventricle foraminal extension and larger tumors in the imaging studies. Patients with aneuploid tumors responded well to treatment regimens as compared with those with diploid tumors. Cell cycle analysis showed that the patients with progressive disease had a high S-phase fraction in the tumor cell population as compared with patients with favorable response to treatment. The correlation coefficients between Bcl-2 and MRP, Bcl-2 and Bax, p53 and p21, as well as Ki67 and PCNA were positive and significant, indicating their possible coregulated expression. The relationship between these markers indicates their relative and cumulative effect on cellular drug resistance, apoptosis, and/or cell proliferation in pediatric medulloblastomas.

Classifying the medulloblastoma: insights from morphology and molecular genetics

Significant advances in the treatment of the medulloblastoma (MB) have been made in the last 30 years, reducing mortality by 2-fold. Further improvements in the cure rate require an increased understanding of the biology of MBs, and this will translate into refinements in their classification. Scrutiny of the cytological variation found among MBs has recently led to the concept of the anaplastic MB, which overlaps the large-cell variant and appears to share its poor prognosis. In contrast, the MB with extensive nodularity, a distinctive nodular/desmoplastic variant occurring in infants, has a better outcome than most MBs in these young patients. Building on cytogenetic studies that have drawn attention to abnormalities on chromosome 17 in over a third of MBs, research shows non-random losses on chromosomes 8, 9, 10, 11 and 16, and gains on chromosomes 1, 7 and 9. Overexpression of ErbB2 receptors and losses on chromosome 17p have been proposed as independent indicators of aggressive behaviour, while high TrkC receptor expression indicates a favourable outcome. There is a strong association between anaplastic/large-cell tumours and MYC amplification, which has previously been linked with aggressive disease, but associations between abnormalities on chromosome 17 and anaplastic/large-cell MBs and between abnormalities in the shh/PTCH pathway and the desmoplastic variant are more controversial. Classification of the MB histopathologically and according to profiles of molecular abnormalities will help both to rationalize approaches to therapy, increasing the cure rate and reducing long-term side-effects, and to suggest novel treatments.

Are childhood and adult medulloblastomas different? A comparative study of clinicopathological features, proliferation index and apoptotic index

Childhood medulloblastomas have been suspected to be biologically different from adult tumors, though comparative studies are sparse in the literature. The present study aims to establish any differences or nexus in the biological characteristics between childhood and adult medulloblastomas. A total of 181 medulloblastomas were studied with respect to clinical and histological characteristics, MIB-1 labeling index (MIB-1 LI), apoptotic index (AI), ratio of apoptotic to LI, p53 and Bcl-2 protein expressions. Two-thirds (112) of the 181 medulloblastomas occurred in children (< or = 15 years) and 69 in adults (> 15 years). Childhood tumors were more commonly of classical histology and midline location while the desmoplastic variant and lateral location occurred more frequently in adults. Adult medulloblastomas were biologically less aggressive, having lower growth rate parameters (mean MIB-1 LI 19.1 +/- 15.7; AI 3.73 +/- 2.71 and AI:LI 0.207 +/- 0.162) as compared to childhood tumors (mean MIB-1 LI 28.3 +/- 20.4; AI 2.86 +/- 2.14 and AI:LI 0.108 +/- 0.111). p53 and Bcl-2 protein expressions were infrequent in all groups of tumors. No difference was noted in any of the parameters when classical and desmoplastic medulloblastomas were compared as a whole. But when compared between the age groups, an interesting observation (hitherto unreported in English literature) was that both classical and desmoplastic variants of childhood medulloblastomas had higher LI, lower AI and lower AI:LI ratio than their counterparts in adults, indicating that differences in growth rates cannot be attributed to differences in the frequency of occurrence of the histological variants in the two age groups. Thus, this study conclusively shows that there is a biological difference between childhood and adult medulloblastomas which is independent of standard histology and appeared to be associated more with age-related factors. This also warrants less-aggressive therapy for adult medulloblastoma.

Features of proliferation and in vitro drug resistance in central primitive neuro-ectodermal tumours

The features of proliferation in brain tumours are related with clinical prognosis for several types of brain tumours, especially gliomas. For childhood central primitive neuro-ectodermal tumours (cPNET), including medulloblastoma, this relation has previously been unclear. The aim of this study is to investigate the relationship between proliferative features of cPNET and in vitro resistance for cytostatic drugs measured with the 3-4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium-bromide (MTT) assay. Tumour material was obtained from 23 surgical specimens of cPNET. The expression of the proliferation markers Ki-67, proliferating cell nuclear antigen (PCNA) and cyclin D1 was determined with immunohistochemistry, while S-phase and DNA ploidy were analysed by flowcytometric analysis cell scan (FACS). The in vitro resistance for 10 cytostatic drugs was determined with the MTT assay. Drug resistance levels were available in 19 (83%) of the 23 samples with a complete profile of 10 cytostatic drugs tested in 14 samples. An excellent correlation in drug resistance scores was found between pharmacologically related drugs. The Ki-67 staining in 20 samples varied from 10 to 60% and from 30 to 100% for PCNA. Cyclin D1 staining was negative in 11 out of 18 samples. The S-phase in 16 samples ranged from 2 to 16%. Increased staining of Ki-67 was related with actinomycin D sensitivity (r -.603; P=0.022), while cells with a higher S-phase percentage were more resistant to ifosfamide (r.952; P<0.0001). In vitro drug resistance testing of central primitive neuro-ectodermal tumours (PNET) is feasible with the MTT assay. Ifosfamide resistance was related with increased Ki-67 and S-phase percentage of the tumour cells, while increased Ki-67 was also related with actinomycin D sensitivity. These findings suggest a cell cycle dependent activity of cytostatic drugs in vitro.

Cleaved caspase-3, caspase-7 and poly (ADP-ribose) polymerase are complementarily but differentially expressed in human medulloblastomas

Expression of cleaved caspase-3, cleaved caspase-7 and specific product of caspase-dependent Poly (ADP-Ribose) Polymerase (PARP) cleavage have been examined by immunohistochemistry in seven human medulloblastomas. Cleaved caspase-3 and cleaved PARP expression parallels apoptosis as revealed with classical morphological criteria and with the method of in situ end-labelling of nuclear DNA fragmentation. Cleaved PARP co-localizes cleaved caspase-3 in the majority of tumors and areas thus indicating that caspase-3 is a major effector caspase leading to apoptosis in these tumors. Yet cleaved caspase-7 was also expressed in a small number of cells in four of seven tumors, but was the predominant caspase associated with cleaved PARP in one medulloblastoma. These findings indicate that effector caspase-3 and -7 may act in association, although caspase-7 may be exceptionally dominant in selected tumors.

Aberrant localization of the neuronal class III beta-tubulin in astrocytomas

BACKGROUND

The class III beta-tubulin isotype (betaIII) is widely regarded as a neuronal marker in development and neoplasia. In previous work, we have shown that the expression of betaIII in neuronal/neuroblastic tumors is differentiation dependent. In contrast, the aberrant localization of this isotype in certain nonneuronal neoplasms, such as epithelial neuroendocrine lung tumors, is associated with anaplastic potential.

OBJECTIVE

To test the generality of this observation, we investigated the immunoreactivity profile of betaIII in astrocytomas.

DESIGN

Sixty archival, surgically excised astrocytomas (8 pilocytic astrocytomas, WHO grade 1; 18 diffuse fibrillary astrocytomas, WHO grade 2; 4 anaplastic astrocytomas, WHO grade 3; and 30 glioblastomas, WHO grade 4), were studied by immunohistochemistry using anti-betaIII monoclonal (TuJ1) and polyclonal antibodies. A monoclonal antibody to Ki-67 nuclear antigen (NC-MM1) was used as a marker for cell proliferation. Antibodies to glial fibrillary acidic protein (GFAP) and BM89 synaptic vesicle antigen/synaptophysin were used as glial and neuronal markers, respectively.

RESULTS

The betaIII immunoreactivity was significantly greater in high-grade astrocytomas (anaplastic astrocytomas and glioblastomas; median labeling index [MLI], 35%; interquartile range [IQR], 20%-47%) as compared with diffuse fibrillary astrocytomas (MLI, 4%; IQR, 0.2%-21%) (P <.0001) and was rarely detectable in pilocytic astrocytomas (MLI, 0%; IQR, 0%-0.5%) (P <.0001 vs high-grade astrocytomas; P <.01 vs diffuse fibrillary astrocytomas). A highly significant, grade-dependent relationship was observed between betaIII and Ki-67 labeling and malignancy, but this association was stronger for Ki-67 than for betaIII (betaIII, P <.006; Ki-67, P <.0001). There was co-localization of betaIII and GFAP in neoplastic astrocytes, but no BM89 synaptic vesicle antigen/synaptophysin staining was detected.

CONCLUSIONS

In the context of astrocytic gliomas, betaIII immunoreactivity is associated with an ascending gradient of malignancy and thus may be a useful ancillary diagnostic marker. However, the significance of betaIII-positive phenotypes in diffuse fibrillary astrocytomas with respect to prognostic and predictive value requires further evaluation. Under certain neoplastic conditions, betaIII expression is not neuron specific, calling for a cautious interpretation of betaIII-positive phenotypes in brain tumors.

Apoptosis, neuronal maturation, and neurotrophin expression within medulloblastoma nodules

Nodular/desmoplastic medulloblastomas are a well-established histopathological subtype containing reticulin-free nodules or "pale islands' that are comprised of cells with round "neurocytic" nuclei and abundant cytoplasm. Significant neuronal maturation occurs within nodules. We used immunohistochemistry to evaluate neuronal differentiation in the nodules of 6 of these tumors. The neuronal markers NeuN, synaptophysin, and MAP-2 were identified in the "pale islands" of all 6 nodular medulloblastomas examined, and high and medium molecular weight nonphosphorylated neurofilaments were detected in 2 of the 6 cases. We also observed collections of apoptotic cells within nodules. Given the known role of neurotrophin signaling in neuronal maturation and apoptosis, we analyzed immunohistochemically the distribution of neurotrophin receptors TrkA and TrkC and their primary ligands NGF and NT3 in 14 nodular medulloblastomas. TrkA and TrkC were detected in 13 and 10 cases, respectively, and were predominantly localized within nodules. NGF and NT3 were distributed diffusely with some nodular accentuation. The localized expression of Trk receptors within nodules of desmoplastic medulloblastomas suggests neurotrophin signaling is involved in the apoptosis and neuronal differentiation in medulloblastomas. We also examined expression of p53 and BCL-2 in these tumors; both were prominent in internodular regions but only weakly expressed within nodules. Trk receptors, p53, and BCL-2 are all expressed during development of the normal cerebellum. Interestingly, the immunohistochemical expression profile of these proteins in the differentiating nodules of medulloblastomas is in many ways similar to their expression in the developing cerebellum. Thus similar signaling pathways may be operational in cerebellar development and medulloblastoma tumor differentiation.

Prognostic significance of Ki-67 (MIB-1) proliferation index in childhood primitive neuroectodermal tumors of the central nervous system

BACKGROUND

Primitive neuroectodermal tumors (PNET) of the central nervous system, including medulloblastomas, are the most common malignant brain tumors of childhood. Whereas some patients experience prolonged disease control after surgery and adjuvant therapy, others with tumors that appear comparable will relapse and eventually die from progressive disease.

PROCEDURE

Because proliferative activity may provide a potential correlate of biologic aggressiveness, PNETs of 78 well-characterized patients were evaluated by Ki-67 (MIB-1) immunohistochemistry. Proliferation indices (PI) were determined by counting Ki-67 (MIB-1) positive tumor cells either in the highest staining region (hot spot PI), or in at least 15 randomly chosen fields (random PI).

RESULTS

Twenty-five of 78 PNETs showed amore than twofold higher value of hot spot PI (median 9.3%; range 0.6-56%), compared to random PI (median 5.6%; range 0.2-41.3%), Univariate Cox regression analysis revealed that PNETs with a high hot spot PI had a significantly greater risk of progression and death than PNETs with a low hot spot PI (hazard ratio 1.58, P = 0.04). The hazard ratio remained significant after adjusting for M-stage in multivariate analysis. In contrast to hot spot PI, random PI proved not to be a significant prognostic predictor.

CONCLUSIONS

Hot spot PI is a significant and independent prognostic factor in PNETs. Its assessment is uncomplicated, reliable, and may supplement routine histologic examination as a means for improving the accuracy of predicting the biologic behavior of childhood PNETs.

Abundance of apoptotic neoplastic cells in diagnostic biopsy samples is not a prognostic factor in childhood primitive neuroectodermal tumors of the central nervous system

PURPOSE

To assess if the abundance of apoptotic tumor cells is an independent prognostic factor in primitive neuroectodermal tumors (PNET) of the central nervous system.

PATIENTS AND METHODS

Formalin-fixed paraffin-embedded tumor tissue sections from 78 clinically well-characterized children with PNET were evaluated by terminal deoxytransferase-mediated deoxyuridinie-5'-triphosphate (dUTP) nick-end labeling (TUNEL). Apoptotic indices (AI) were determined by counting TUNEL-positive tumor cells either in the highest staining region (AI hot spot) or in at least 15 randomly chosen fields (AI random). The AI hot spot and AI random were then correlated with clinical variables and survival outcome.

RESULTS

AI hot spot (median 0.56%; range 0%-6.54%) and AI random (median 0.30%; range 0%-3.21%) showed considerable intertumor variability. Moreover, 53% of the evaluated PNET showed a more than two-fold difference between AI hot spot and AI random, showing important intratumoral variability of the abundance of apoptotic cells in a subset of the evaluated PNET. No significant associations were found between AI hot spot and AI random with clinical variables or survival outcome.

CONCLUSION

The apoptotic index does not predict survival outcome and is not specifically associated with clinical variables of prognostic significance in childhood PNET.

Pediatric medulloblastoma: prognostic value of p53, bcl-2, Mib-1, and microvessel density

The aim of this study was to retrospectively assess the prognostic value of p53 and bcl-2 protein expression, cell proliferation index (Mib-1 index), and tumor microvessel density (factor VIII-related antigen) in pediatric medulloblastoma patients. Tumor specimens of 55 patients (age 2-18 years) with medulloblastoma treated with a curative intent between 1972 and 1991 were studied. Slides of paraffin embedded tissue were stained with monoclonal antibodies (mAb) and examined under high power light microscopy for the presence of immunoreactivity. Microvessel density was scored both in the area of most intense staining ('Angio-max') and in 3 additional randomly selected areas. The sum of these 4 scores was termed 'Angio-total'. 'Angio-max' and 'Angio-total' were evaluated separately by two independent investigators to assess reproducibility. None of the parameters studied, i.e. p53 or bcl-2 expression, Mib-1 index or microvessel density scores were associated with patient survival. Microvessel scores between observers were significantly but weakly correlated, with correlation coefficients (r) < 0.5 for both 'Angio-max' and 'Angio-total'. Leptomeningeal spread at diagnosis was the only independent factor associated with a poor survival (p = 0.003). There was no association of leptomeningeal metastasis with any of the biological markers tested in this study.

[Medulloblastomas: clinical, epidemiological and pathological findings in 28 cases]

We report the clinical, epidemiological and pathological findings of 28 patients with medulloblastoma: 22 were male; age ranged from 1 to 50 years, with a mean of 15 years. The most frequent symptoms and signs were headache (64%) and vomiting (64%). Only one patient showed a desmoplastic medulloblastoma variant, the others showed classical medulloblastomas. Regarding treatment, most patients were submitted to total resection (n=10) or partial tumorectomy (n=7). A low rate of tumoral recurrence was observed, occurring in 21% of the patients (n=6) after 4 years of follow-up. Chemotherapy seemed to contribute to a lower recurrence rate amongst our patients. Our findings are similar to those reported in literature, thus helping to understand the biological behavior of this type of tumor.

Bone morphogenetic proteins-2 and -4 attenuate apoptosis in a cerebellar primitive neuroectodermal tumor cell line

Similarities between primitive neuroectodermal tumors and central nervous system (CNS) progenitor cells have evoked interest in the response of these tumors to endogenous growth factors. The bone morphogenetic proteins (BMPs) have recently been found to regulate survival and differentiation of CNS progenitor cell populations. In this study, we investigated the effects of BMP-2, BMP-4, and BMP-6 on the undifferentiated cerebellar primitive neuroectodermal tumor or medulloblastoma cell line DAOY. Analysis by reverse transcriptase-polymerase chain reaction showed that mRNAs for type IA and type II BMP receptors were present in control cultures. In cultures treated with BMP-2, mRNAs for BMP receptor type IB and the activin R-I receptor became evident. Cultures were analyzed for total cell counts, proliferating cell nuclear antigen (PCNA), and apoptotic DNA fragmentation. There was a significant increase in total cell number in the BMP-2 and BMP-4 treatment groups, without any change in PCNA reactivity, and a dramatic decrease in the proportion of apoptotic nuclei at concentrations of BMP-2 and BMP-4 above 5 ng/ml (P<0.001). These effects were not observed with BMP-6, TGF-beta1 or GDNF. These results suggest that the increase in total cell number is due to the attenuation of apoptosis by BMP-2 and BMP-4. The anti-apoptotic effect of BMP-2 and BMP-4 on this neuroectodermal cell line has potential clinical implications for neuroectodermal tumors.

Cell-cycle inhibitor p27/Kip-1 expression in non-astrocytic and non-oligodendrocytic human nervous system tumors

p27/kip-1 is a 'universal inhibitor' which inhibits cyclin complexes with cyclin-dependent kinases (CDKs), preventing cell cycle from the G1-S progression. It is expressed in normal oligodendrocytes and in differentiated glial tumors, decreasing with anaplasia and malignancy. In non-astrocytic and non-oligodendrocytic tumors of the nervous system, such as meningiomas, schwannomas, medulloblastomas, neuroblastomas and malignant lymphomas, p27/kip-1 is inconstantly and sometimes poorly expressed. This can be due to the lacking of p27 expression in the normal counterpart of tumor cells. In some tumors, p27/kip-1 expression can be attributed to a differentiation process, as in the pale islands of desmoplastic medulloblastoma and in neuroblastomas. A correlation of p27/kip-1 expression with histology was not found, with the exception of apoptosis in medulloblastomas. p27/kip-1 is in feed-back with cyclins and CDKs for the control of cell proliferation and its expression may occur where requested by the interplay with cyclins and other inhibitors.

Diagnostic markers in paediatric medulloblastoma: a Paediatric Oncology Group Study

AIMS

We have reviewed immunohistochemically 17 paediatric medulloblastomas in order to determine if correlations exist that might be useful in subclassifying these tumours.

METHODS AND RESULTS

The patient group included 11 children who had died (mean survival 13 months) and six still alive (followed for up to 10 years). Ten tumours were diffuse and six were nodular (one biopsy had only perivascular tumour). Of the 10 diffuse tumours, three were desmoplastic: of the six nodular tumours, all six were desmoplastic. All 17 tumours were synaptophysin-reactive: three nodular tumours were glial fibrillary acidic protein (GFAP)-reactive in the nodules (two of three S 100-reactive tumours were also GFAP-reactive). MIB-1 labelling indices (LI) ranged from 5 to 80%. Six tumours exhibited at least 1% LI against Tp53 (Mab D07 and/or Mab 1801). Eight cases were 100% bcl2-reactive with nine cases having an LI <80% ('low labelling'). All nine 'low labelling' bcl2 cases were TP53 non-reactive; all six Tp53-reactive cases were bcl2 100% reactive. Six of 10 patients with diffuse medulloblastomas survived 18 months or less while four of 10 are alive up to 10 years. In contrast, five of six patients with nodular neoplasms died within 48 months of diagnosis with one patient followed up for less than 1 year.

CONCLUSIONS

Immunohistochemistry is a useful adjunct in characterizing subsets of paediatric medulloblastomas and confirms that larger co-operative studies may be fruitful in identifying a prognostic utility of a combined histochemical/immunohistochemical analysis on these tumours.

Ki-67 immunolabelling index is a prognostic indicator in childhood posterior fossa ependymomas

Conventional histological evaluation and subclassification of childhood ependymomas poorly predict their biological behaviour. The Ki-67 labelling index (Ki-67 LI), a measure of growth fraction, correlates with the biological behaviour of several neoplasms, and this retrospective study tested the hypothesis that Ki-67 LI is a prognostic indicator in childhood posterior fossa ependymomas. Immunocytochemistry using an antibody to Ki-67 was undertaken on 5 microns sections of formalin-fixed, paraffin-embedded tissue from 74 cases of childhood (age < 16 years.) posterior fossa ependymoma. A Ki-67 LI was established by counting the proportion of labelled nuclei in more than 1000 cells from several histological fields. Several clinical and histological variables (including Ki-67 LI) potentially associated with survival were entered into univariate and multivariate analyses using a Cox proportional hazards model. Variables that showed a significant and independent association with survival were Ki-67 LI (P < 0.002), whether total surgical resection had been achieved according to operation records (P < 0.03), and whether no adjuvant therapy had been given (P < 0.01). Age, sex, and the presence of necrosis or microvascular proliferation did not correlate with survival. In our defined population of patients with ependymomas, Ki-67 LI is a strong prognostic indicator. We recommend that Ki-67 LI is used in the histological evaluation of childhood posterior fossa ependymomas during trials of novel adjunctive therapies.

Apoptosis is associated with atypical or malignant change in meningiomas. An in situ labelling and immunohistochemical study

AIMS

Although necrosis is an important phenomenon with implications for grading and prognostication in meningiomas, the alternate form of cell death, apoptosis, has not been extensively studied. In this series, we aimed to determine whether apoptosis in meningiomas correlated with histological types and grading. We also looked for a relationship between expression of apoptosis-related genes bcl-2, p53, c-myc and apoptosis meningiomas.

METHODS AND RESULTS

Fifty-one meningiomas of diverse histological subtypes and grades were investigated with in situ end-labelling of DNA fragments as well as immunohistochemical analysis of three apoptosis-related genes: p53, bcl-2 and c-myc. Our results showed that the apoptosis index was significantly higher in high-grade meningiomas (0.12%, n = 12) in than the benign meningiomas (0.023%, n = 39) P = 0.001) but there was no difference among the different histological subtypes of the benign meningiomas (P = 0.125). There is no obvious relationship between p53, bcl-2 and c-myc staining and apoptosis index in this group of meningiomas.

CONCLUSION

We conclude that apoptosis is an important phenomenon in meningiomas and that it is associated with atypical or malignant changes in meningiomas. Apoptosis in meningiomas has no clearcut relationship with expression of p53, bcl-2 and c-myc.

Apoptosis in neurological disease

Enormous interest in cell death in the past several years has moved apoptosis to the forefront of scientific research. Apoptosis has been found to mediate cell deletion in tissue homeostasis, embryological development, and immunological functioning. It also occurs in pathological conditions, including cancer and acquired immunodeficiency syndrome, and is implicated in neurodegenerative diseases. Claims of neuronal apoptosis induced by various agents and conditions are published regularly, but in many instances the data are questionable because they are incomplete. This review presents a brief history of apoptosis and describes the evidence required before claims of apoptosis are made. Summaries and critiques of important investigations concerning the genetic and biochemical regulation of neuronal apoptosis are presented, as are other studies describing connections between apoptosis and neuronal cell death in physiological and pathological situations. There is a realization that apoptosis can be programmed and is distinguishable from necrotic cell death. Combining apoptosis with programmed cell death produces misleading terminology and confusion over these two forms of cell degeneration. Further investigations into neuronal apoptosis should focus on all of the criteria that the original investigators outlined 25 years ago, to clarify whether apoptosis and/or another form of cell death mediates neuronal degeneration in physiological settings and in neurological diseases such as Alzheimer's disease, Parkinson's disease, epilepsy, and ischemia/stroke.

Current therapy and new perspectives in the treatment of medulloblastoma

Medulloblastoma, a malignant tumor arising from the medullary velum, is the most common malignant brain tumor of childhood. Local extension into the cerebellar hemisphere, infiltration of the floor of the fourth ventricle, and seeding into the subarachnoid space are common. Early diagnosis and improved treatment consisting of surgery followed by radiation and chemotherapy for selected high-risk patients has contributed to a dramatic change in survival. This article reviews current treatment strategies and describes new therapies that have the potential to improve the outlook of children with medulloblastoma.

Proliferation and DNA fragmentation in meningioma subtypes

Atypical meningioma has been introduced as tumour subtype of intermediate biological behaviour between classical and malignant meningiomas. To substantiate this three-step scale of malignancy, we assessed the proliferative activity reflected by Ki-67 (MIB1) labelling index (LI) in a series of 89 meningiomas, including 15 classical, 29 atypical, 35 anaplastic tumours, and 10 haemangiopericytomas and papillary meningiomas. The possible correlation of proliferation with the frequency of apoptosis and their relations to BCL-2 immunoexpression was investigated in seven classical, 10 atypical and 10 malignant meningiomas. Apoptosis was demonstrated by evaluation of the frequency of apoptotic figures, by the enzymatic technique of in situ tailing (IST) which stains apoptotic DNA fragments, and by DNA preparation and gel electrophoresis demonstrating DNA laddering in frozen tissues of five meningiomas. MIB1 LI revealed a highly significant increase from classical through atypical to anaplastic meningiomas (P < 0.0001); haemangiopericytomas and papillary meningiomas were well within the range of atypical meningiomas. IST indices rose with increasing malignancy and correlated with MIB1 LI (P < 0.0001): they showed a weak inverse correlation with BCL-2 immunoexpression (P = 0.05). BCL-2 expression tended to decrease with malignancy grade and was unrelated to MIB1 LI or frequency of apoptosis. Our data show that (i) apoptosis is a feature of meningiomas, significantly correlated with the malignancy scale. (ii) DNA fragmentation shows significant correlation with proliferation and inversely with BCL-2 expression; (iii) proliferation indices and frequencies of apoptosis/DNA fragmentation within meningioma subgroups corroborate the intermediate biological position of the atypical meningioma between classical and malignant meningiomas.

Nerve growth factor induces apoptosis in human medulloblastoma cell lines that express TrkA receptors

Neurotrophins act through their cognate receptors to promote the differentiation and/or survival of neuronal progenitor cells, immature neurons, and other cells. Here, we examined the effects of nerve growth factor (NGF) and its cognate receptor (Trk or TrkA) on the survival of a common childhood brain tumor, i.e., medulloblastoma, a tumor that resembles CNS neuroepithelial progenitor cells. To do this, we engineered two human medulloblastoma cell lines (i.e., D283MED and DAOY cells) to express human TrkA using a retroviral expression vector. Surprisingly, NGF-treated medulloblastoma cells expressing the TrkA receptor (D283trk and DAOYtrk cells) grown in the presence or absence of serum underwent massive apoptosis, but similar treatment did not induce apoptosis in wild-type uninfected cells, cells expressing an empty vector, or cells expressing the TrkC receptor. Furthermore, D283MED cells engineered to express the human p75 NGF receptor (D283p75) also did not undergo apoptosis. Significantly, NGF-induced apoptosis in D283trk and DAOYtrk cells can be inhibited by anti-NGF antibodies and by K-252a, an inhibitor of TrkA tyrosine phosphorylation and mimicked by high concentrations of NT3. Because NGF treatment primarily eliminated D283trk cells from the S phase of the cell cycle, this form of NGF-mediated apoptosis is cell cycle-dependent. These findings suggest that a NGF/TrkA signal transduction pathway could activate apoptotic cell death programs in CNS neuroepithelial progenitor cells and in childhood brain tumors.

Apoptosis in astrocytic neoplasms

Apoptosis is a form of programmed cell death characterized by specific morphologic and biochemical properties. Tumorgenesis is the consequence not only of cell proliferation but also the loss of the ability to undergo apoptosis [2]. Bcl-2 is a protooncogene which has the ability to block apoptosis in many cell types. Astrocytic neoplasms are very aggressive tumors which many times fail to respond to surgery, radiation or chemotherapy. They frequently overexpress wild-type p53 which is associated with the expression of bcl-2, and thus they may have evolved a mechanism to subvert apoptosis and allow continued growth. We examined the apoptotic index in fifty-nine astrocytic tumors of various histological grades (Oncor ApopTag Plus In Situ Detection Kit) and compared this with the level of bcl-2 expression. Low grade astrocytomas (0.21 +/- 0.05; range 0.0-0.9) and anaplastic astrocytomas (0.27 +/- 0.13; range 0.0-2.6) had significantly less apoptosis than glioblastomas (0.70 +/- 0.13; range 0.0-2.1; Kruskal-Wallis test, P < or = 0.01). In contrast, bcl-2 expression was similar in all grades of astrocytic tumors and did not correlate with the apoptotic index. Cells of low grade and anaplastic astrocytomas are less likely to undergo apoptosis; however, this does not seem to be a direct consequence of the regulation of bcl-2 expression. The difference in growth potential despite differences in apoptotic index is likely to be attributed to differences in mitotic not apoptotic activity.

Is medulloblastoma the same tumor in children and adults?

The appearance of medulloblastoma in adult age and the uncertain overlapping of prognostic factors in pediatric and adult populations stimulate the question of whether medulloblastoma is different in adults and in children. The pathologic features, proliferation potential and glial/neuronal differentiation have been investigated in 42 adult medulloblastomas and 42 medulloblastomas of children; the quantitative data have been compared between the two groups of age. Homer-Wright rosettes, nuclear polymorphism and histologic signs of neuronal differentiation were more frequent in children cases; GFAP-positive tumor cells and desmoplastic type were more frequent in adult cases. The mean, median and rage of Lis, with PCNA and MIB-1 were significantly (p < 0.05) higher in adults than in children. All cases, independently from age of the patients were immunoreactive with markers of neuronal commitment (class III beta tubulin isotype, MAP-2, neurofilaments). The immunoreactivity pattern suggested a more mature neuronal character in desmoplastic cases of adults than of children and in classic cases of children than of adults. In conclusion, some phenotypic differences between childhood and adult medulloblastoma exist, but do not support a substantially different course of the disease. The higher proliferation potential in adult than in childhood cases is unexpected in a tumor of embryonal origin, and reduces the applicability of Collin's law to medulloblastoma.

Effects of fenretinide (4-HPR) on prostate LNCaP cell growth, apoptosis, and prostate-specific gene expression

BACKGROUND

Although fenretinide (4-HPR) is currently being evaluated in a phase II clinical study for the chemoprevention of prostate cancer [Greenwald et al.: CA 45:31-49, 1995], the mechanism underlying its antineoplastic activity has not been elucidated.

METHODS

Androgen-dependent human prostatic LNCaP cells cultured with fetal bovine serum (FBS) were treated with 4-HPR and evaluated for effects on cell growth and cell cycle phase distribution, induction of apoptosis, and changes in proliferating cell nuclear antigen (PCNA), prostate-specific antigen (PSA), and androgen receptor (AR) levels.

RESULTS

LNCaP cells treated with 4-HPR for 6 days showed 82-95% suppression of cell growth, with accompanying time- and dose-dependent downregulation of PCNA, a partial arrest in G1 phase of the cell cycle, and a marked increase in the percentage of apoptotic cells. Apoptosis was demonstrated by the characteristic DNA fragmentation pattern seen on agarose gels, and by flow cytometric analysis. 4-HPR-induced prostate-specific phenotype changes included significant downregulated expression of both intracellular and secreted forms of PSA, which were preceded by a reduction of AR expression.

CONCLUSIONS

These data suggest that 4-HPR acts as a pleiotropic effector of prostate cell growth and specific gene expression.

Pale islands in medulloblastoma consist of differentiated cells with low growth potential

Cerebellar medulloblastomas are the most common embryonal neoplasms occurring in the pediatric age group. Thirty-five specimens from 28 cases of medulloblastoma and variant neoplasms were examined to elucidate the histopathologic significance of the reticulin-free pale islands. In 10 specimens, there were light-looking areas corresponding to pale islands: three specimens from desmoplastic and seven from classic medulloblastoma. The difference in cell population, 1.73-fold more cells in dark areas than in light areas (P < 0.001), seemed to be a major factor in the formation of the biphasic architecture. Immunohistochemically, occasional tumor cells in both areas were found to express neuronal phenotypes. In addition, positive immunoreactivity for glial markers was exceptional. There was significant difference in the staining indices (SI) for cell proliferation markers. The light areas consistently showed low SI values (mean MIB-1 SI, 5.75; mean PCNA SI, 11.8) compared with the dark areas (mean MIB-1 SI, 22.7; mean PCNA SI, 44.9). It is suggested that light areas (pale islands) consist of more differentiated cells of neuronal lineage with relatively low proliferation potential. These tumor cells might proliferate in a group, and then expand, thereby compressing the surrounding tissue to form pale islands.

Cellular and molecular pathology of medulloblastoma

Medulloblastoma is a malignant embryonal tumor predominantly of childhood. It occurs principally in the midline cerebellar region but is prone to invade the meninges and cerebrospinal fluid spaces. It is the principal posterior fossa tumor in children and represents 20% of all brain tumors in this age group. Considerable advances have been made in characterizing the morphologic subtypes, immunophenotypes, and in vitro behavior of cell lines. However, the cell of origin and its relationship to other related primitive neuroectodermal tumors remains uncertain. Although recent advances in the application of proliferation markers and the use of apoptosis in situ labelling have been applied, a prognostically relevant marker applicable to surgical neuropathology remains to be developed. The fundamental molecular pathogenesis of tumor development remains unknown, although recent exciting advances have shown alterations in some members of the PAX family of genes as well as increased expression of neurotrophin receptors. These may prove to be of prognostic significance.

Medullocytoma (lipidized medulloblastoma). A cerebellar neoplasm of adults with favorable prognosis

This study describes three cases of neuroectodermal cerebellar neoplasms occurring in adults, characterized by a monomorphic population of round cells with scanty cytoplasm and focal areas of lipid accumulation. Astrocytic and neuronal differentiation was confirmed in these cells by glial fibrillary acidic protein and synaptophysin immunoreactivity. Electron microscopy performed in two cases showed neuritic processes, synapses, and dense-core granules. Patients included two men and one woman, and the age at diagnosis was 36, 37, and 57 years, respectively. Two patients refused any postoperative treatment. One of these had two surgically removed recurrences after 10 and 11 years and died postoperatively from intracranial hemorrhage. The second had two recurrences after 10 and 15 years and is alive and in good health at the last follow-up. The third patient received postoperative radiotherapy and is alive and well after 2 years. Review of the literature revealed seven cases of cerebellar neoplasms with histological features similar to those observed in our series. These lesions have been considered a variant of medulloblastomas. The age of patients ranged from 42 to 77 years (mean age, 51 years); four were women, 3 men. Follow-up information available in two cases indicates a 5-year survival with surgery alone. These data indicate that these cerebellar neuroectodermal neoplasms have morphologically unique features and indolent biologic behavior that distinguish them from the highly aggressive medulloblastoma; the term medullocytoma for this form is suggested.

Apoptosis of colon cancer: comparison with Ki-67 proliferative activity and expression of p53

The role of apoptosis in colon cancer was investigated in terms of control of growth and expression on p53, using the nick-ended-DNA labelling method and immunohistochemistry. The apoptotic labeling index was highest in the T1 stage (24 cases), as was the proliferative activity, assessed in terms of the Ki-67 labeling index. Both labeling indices demonstrated similar overall incidence curves for the total 95 colon cancer cases, and examination of individual cases revealed a statistically significant correlation (P=0.01). However, neither index had any relation to p53. The results thus suggest that apoptosis in colon cancers has a linkage with proliferative activity that can be assessed by Ki-67 labeling, but is not regulated by the p53 system. This might contribute to the diversity of colon cancer growth.

Prognostic significance of Ki-67 labeling indices obtained using MIB-1 monoclonal antibody in patients with supratentorial astrocytomas

BACKGROUND

Identification of the prognosis of patients with gliomas is important for selecting and evaluating the effectiveness of treatment. The aim of this study was to evaluate the Ki-67 labeling index (LI) using the newly generated MIB-1 monoclonal antibody (MoAb) as a prognostic indicator for patients with astrocytomas.

METHODS

Ki-67 immunohistochemistry was performed on paraffin sections to estimate the growth potential of 72 supratentorial astrocytomas using the MIB-1 MoAb after hydrated autoclaving treatment. Multivariate analysis using the Cox proportional hazard stepwise model was used to evaluate the influence of Ki-67 LI, as well as other prognostic factors, on the duration of survival of patients with supratentorial astrocytomas.

RESULTS

The mean Ki-67 LI was 3.8% (+/- 2.7%; standard deviation [SD]) in Grade 2 gliomas (n = 19), 18.4% (+/- 9.7% SD) in Grade 3 gliomas (n = 25), and 31.6% (+/- 12.9% SD) in Grade 4 gliomas (n = 28). Multivariate survival analysis showed that histologic grade, Ki-67 LI, and Karnofsky performance status (KPS) score before and after treatment were independent, statistically significant prognostic factors for patients with all grades of astrocytomas. In high grade lesions, Ki-67 LI, tumor location (superficial vs. deep), and KPS score after treatment were significant prognostic variables, whereas histologic grade did not meet the significance level for entry into the stepwise model.

CONCLUSIONS

These results indicate that the Ki-67 LI obtained using MIB-1 MoAb is an important and practical tool for estimating biologic behavior of gliomas, as well as for predicting survival.

In situ end-labelling, light microscopic assessment and ultrastructure of apoptosis in lung carcinoma

AIMS

To compare in situ end-labelling (ISEL) of apoptosis in lung carcinoma with quantitative and semiquantitative light microscopic assessment and ultrastructural observations.

METHODS

ISEL of apoptosis was evaluated in 42 lung carcinomas (24 squamous cell carcinomas, 12 adenocarcinomas and six small cell carcinomas). Results were correlated semiquantitatively with the extent of apoptosis in haematoxylin and eosin stained sections, with apoptotic indices and with ultrastructural observations (nine cases).

RESULTS

In each tumour type the extent of apoptosis identified by ISEL correlated with that observed on light and electron microscopy. Tumour cells undergoing apoptosis showed either uniform nuclear staining with a surrounding "halo" or peripheral nuclear membrane staining. The latter pattern was more prominent in small cell carcinoma and correlated ultrastructurally with early apoptosis. A variable proportion of apoptotic cells and apoptotic bodies were unlabelled. Necrotic tumour cells were weakly stained but were distinguishable from apoptotic cells.

CONCLUSIONS

ISEL, if used in conjunction with standard methods for investigating apoptosis, is a useful adjunct to the investigation of apoptosis in human tumour tissue.

Apoptosis and cell proliferation in human neuroepithelial tumors

Apoptosis and cell proliferation were studied in 180 human neuroepithelial tumors (30 medulloblastomas, 30 intracranial ependymomas, 30 oligodendrogliomas and 90 astrocytic tumors, including 30 astrocytomas, 30 anaplastic astrocytomas and 30 glioblastomas). Apoptotic nuclei were detected by morphology and in situ end-labeling (ISEL) of DNA breaks. The frequency of apoptotic nuclei varied from oncotype to oncotype and their distribution in each oncotype was uneven. An apoptotic index (AI) was calculated; this was high in malignant tumors and in tumors of embryonal origin and lower in tumors of the glial series. The AI/mitotic index (MI) ratio was lower in malignant tumors and higher in benign tumors, suggesting a relationship between apoptosis and cell proliferation. There was no significant correlation of either AI or AI/MI ratio with either labeling index (LI) of Ki-67 clone MIB-1 or with survival. A trends towards low AI/MI ratio in tumors with high LI and short survival was observed. Apoptosis expresses cell loss in tumors, but it did not appear to be a prognostic factor.

Apoptosis in cerebral astrocytic tumours and its relationship to expression of the bcl-2 and p53 proteins

Apoptosis is an important determinant of tumour growth which can be regulated by the bcl-2 and p53 genes. This study examines the relationship between apoptosis, growth fraction (Ki-67 immunolabelling index), and accumulation of the bcl-2 and p53 proteins in a spectrum of cerebral astrocytic tumours (n = 81), including fibrillary astrocytomas (n = 16), anaplastic astrocytomas (n = 19), and glioblastomas (n = 46). Median apoptosis indices (AIs) increased across this spectrum of tumours, and a significant (P < 0.0001) correlation was demonstrated between AI and Ki-67 labelling index (LI). Immunolabelling with the bcl-2 antibody was found in 44% of fibrillary astrocytomas, 42% of anaplastic astrocytomas, and 28% of glioblastomas. It was also found in the vascular endothelial proliferation typically seen in glioblastomas, and in the giant, multinucleated cells of some glioblastomas. No clear relationship between AI and bcl-2 accumulation was evident. Immunolabelling with the p53 antibody was found in 56% of fibrillary astrocytomas, 79% of anaplastic astrocytomas, and 50% of glioblastomas. No clear relationship between AI and patterns of p53 immunolabelling was evident. Equal proportions of p53-positive tumours were bcl-2 positive and bcl-2 negative, but a small proportion of p53-negative tumours was bcl-2 positive. The correlation between AI and Ki-67 LI is in line with findings in other malignant tumours. We suggest that the regulation of apoptosis in astrocytic tumours is too complex for a clear association between AI and bcl-2 and p53 protein expression to be demonstrated.

Deregulated expression of PAX5 in medulloblastoma

Medulloblatoma is a pediatric brain tumor originating in the human cerebellum. A collection of 23 medulloblastomas was analyzed for expression of the developmental control genes of the PAX and EN gene families by RNase protection and in situ hybridization. Of all nine PAX genes investigated, only PAX5 and PAX6 were consistently expressed in most medulloblastomas (70 and 78% of all cases, respectively), as were the genes EN1 (57%) and EN2 (78%). EN1, EN2, and PAX6 genes were also expressed in normal cerebellar tissue, and their expression in medulloblastoma is consistent with the hypothesis that this tumor originates in the external granular layer of the developing cerebellum. PAX5 transcripts were, however, not detected in the neonatal cerebellum, indicating that this gene is deregulated in medulloblastoma. In the desmoplastic variant of medulloblastoma, PAX5 expression was restricted to the reticulin-producing proliferating tumor areas containing undifferentiated cells; PAX5 was not expressed in the reticulin-free nonproliferating islands undergoing neuronal differentiation. These data suggest that deregulated expression of PAX5 correlates positively with cell proliferation and inversely with neuronal differentiation in desmoplastic medulloblastoma.

Ultrastructural detection of DNA strand breaks in apoptotic neural cells by in situ end-labelling techniques

Recently developed techniques based on 'in situ end-labelling' (ISEL) of DNA strand breaks may help to identify apoptotic cells in tissue sections. We have applied ISEL techniques at the electron microscopic (EM) level, in order to verify if ultrastructural features of apoptosis are indeed associated with evidence of DNA fragmentation, and whether cells committed to, but which have not yet entered the stage of cell death are also labelled. Terminal transferase and DNA polymerase assays were applied to thin sections of Araldite and LR Gold-embedded medulloblastomas and embryonic mouse dorsal root ganglia. Digoxigenin-labelled nucleotides were used; incorporation was demonstrated by immunogold staining. Apoptotic cells in various stages of the death process were easily labelled in both tissues. In addition, DNA fragmentation was demonstrated in cells with initial chromatin condensation, but otherwise indistinguishable from adjacent unstained cells. Our results show that EM-ISEL techniques effectively demonstrate the occurrence of DNA strand breaks in apoptotic and possibly 'pre-apoptotic' cells in neural tissues. Since the labelling is easily obtained on tissue that is routinely processed for electron microscopy, this technique may allow retrospective studies on archival material.