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

Immunohistochemical Expression of p27Kip1, p57Kip2, Cyclin D1, Nestin, and Ki-67 in Ependymoma

p27 and p57 are tumor suppressors that are dysregulated in many cancers. We investigated the immunohistochemical expression of p27 and p57 in ependymoma, with a secondary emphasis on cyclin D1, nestin, and Ki-67. Sixty-five patients diagnosed with ependymoma were included. Clinical and tumoral data were retrieved, and the expression of p27, p57, cyclin D1, nestin, and Ki-67 was measured. Pearson’s χ2 test was used to measure associations and the Kaplan–Meier method was used for survival analysis. p27 underexpression was significantly associated with pseudopalisading necrosis in tumors with foci of necrosis (p = 0.004). Cyclin D1 overexpression was associated with intracranial (p = 0.044), recurrent (p = 0.022) and grade 3 tumors (p = 0.016); nestin overexpression was associated with supratentorial (p = 0.025), mitotically active (p < 0.001), and grade 3 tumors (p = 0.004); Ki-67 overexpression was associated with supratentorial (p = 0.044) and grade 3 tumors (p < 0.001) and the 3 main features of anaplasia. None of the markers were intercorrelated or predictive of overall survival. In conclusion, p27 underexpression in tumors with foci of necrosis signals a pseudopalisading pattern. Cyclin D1, nestin, and Ki-67 are useful markers in ependymoma, but evidence-based cutoff values are required to standardize this interpretation.

Prognostic value and functional consequences of cell cycle inhibitor p27Kip1 loss in medulloblastoma

Background

The cyclin-dependent kinase inhibitor p27^Kip1 functions during normal cerebellar development and has demonstrated tumor suppressor functions in mouse models of medulloblastoma. Because P27 loss is associated with increased proliferation, we assessed whether P27 absence in surgical medulloblastoma specimens correlated with response to therapy in pediatric patients enrolled in two large studies. Additionally, we examined the functional consequence of p27^Kip1 loss in the SmoA1 medulloblastoma model to distinguish whether p27^Kip1 reduces tumor initiation or slows tumor progression.

Findings

Analysis of 87 well-characterized patient samples identified a threshold of P27 staining at which significant P27 loss correlated with poor patient outcome. The same criteria, applied to a second test set of tissues from 141 patients showed no difference in survival between patients with minimal P27 staining and others, suggesting that P27 levels alone are not a sufficient prognostic indicator for identifying standard-risk patients that may fail standard therapy. These findings were in contrast to prior experiments completed using a mouse medulloblastoma model. Analysis of cerebellar tumor incidence in compound mutant mice carrying the activated Smoothened (SmoA1) allele that were heterozygous or nullizygous for p27^Kip1 revealed that p27^Kip1 loss did not alter the frequency of tumor initiation. Tumors haploinsufficient or nullizygous for p27^Kip1 were, however, more invasive and displayed a higher proliferative index, suggesting p27^Kip1 loss may contribute to SmoA1 medulloblastoma progression.

Conclusions

These studies revealed P27 loss affects medulloblastoma progression rather than initiation and that this putative biomarker should not be used for stratifying children with medulloblastoma to risk-based therapeutic regimens.

Application of p27 gene therapy for human malignant glioma potentiated by using mutant p27

OBJECT

Malignant glioma could be an ideal candidate for local gene therapy because its invasion is local and it has little metastatic potential. A low expression level and high degradation activity of p27 are known to constitute an independent poor prognostic factor in patients with malignant glioma. In this study, the authors investigated the roles of wild-type p27 and mutant p27 on the treatment of malignant glioma.

METHODS

The authors used two adenoviruses: one expressed wild-type p27 (ad-p27wt) and the other, containing a mutation at the major metabolic site, expressed mutant p27 (ad-p27mt). The antitumor effects of the two adenoviruses were compared with respect to cell growth arrest, cell cycle alteration, apoptosis induction, and in vitro tumorigenicity in three glioblastoma mutiforme (GBM) cell lines and in a primary GBM cell line. Transduction with ad-p27wt or ad-p27mt induced the production of p27 and the dephosphorylation of pRB. The protein level of mutant p27 was significantly higher than that of wild-type p27. The ad-p27wt induced cell cycle arrest at the G1-S transition point, whereas the ad-p27mt induced arrest at the G2-M point. Both ad-p27wt and ad-p27mt induced a growth-inhibiting effect, apoptosis, and suppression of in vitro tumorigenicity; however, ad-p27mt displayed a stronger antitumor effect than ad-p27wt in brain tumor cell lines.

CONCLUSIONS

Gene therapy involving p27, especially mutant p27, has the potential to become a novel and powerful therapy for malignant glioma.

Regulation of p27 in the process of neuroblastoma N2A differentiation

Neuronal differentiation implies morphological and biochemical changes to generate a specialized neuron. N2A neuroblastoma cells can be promoted to undergo differentiation associated to neurites outgrowth, a process linked to the arrest of cell division. Using N2A cells as a model, we investigated the detailed molecular aspects on the involvement of p27 in dibutyryl cAMP-induced neuronal differentiation. In the undifferentiated N2A phenotype, an unusually high level of accumulated p27 protein mass was evidenced. Data suggest that in proliferating cells, p27 could be sequestered by direct interaction with cyclin D1, thus preventing its inhibitory action on cell cycle Cdks. Studies also indicate that p27 is functionally active and that its loss of action on Cdks in proliferating cells is due to its strong association with cyclin D1. Therefore, when cell differentiation is triggered, the action of p27 on Cdks seems to depend on both p27 and cyclin D1 degradation during the early steps of differentiation followed by late events of re-synthesis of active p27. In this context, an overexpression of p27 after N2A transfection with a mouse p27 clone induces the outgrowth of neurites associated with a decrease in cyclin D1 expression. On the other hand, treatment of N2A undifferentiated cells with c-myc antisense oligonucleotides led to a decrease in p27 and cyclin D1 levels, similar events as those in early stages of cell differentiation. Studies suggest that blockage in c-myc expression triggers early events in neuronal differentiation. These studies are of the utmost importance to elucidate regulatory mechanisms of molecules that play a critical role in the transition from a proliferating phenotype to differentiated cells.

Immunohistochemical markers for prognosis of ependymal neoplasms

Intracranial ependymomas are the third most common primary brain tumor in children. Although clinical and histological criteria for ependymoma prognosis are recognized, studies have reported contradictory results. Prognostic significance based on immunohistochemistry of ependymomas has been reported in a few studies. One-hundred and twelve patients with intracranial ependymomas were examined retrospectively for immunoexpression of various tumor-associated antigens and apoptosis. The results demonstrated significant preponderance of expression of the tenascin, vascular endothelial growth factor protein (VEGF), epidermal growth factor (EGFR) and p53 protein in high-grade tumors. Also high-grade ependymomas revealed more prominent labeling indices (LI) for proliferative marker Ki-S1 and apoptotic index (AI), and lower LI for cyclin-dependent kinase inhibitors p27/Kipl and pl4ARF. For low-grade ependymomas the progression-free survival time (PFS) was found to be significantly shorter for Ki-S1 LI > 5%, and for tenascin, VEGF and EGFR positivity. For high-grade ependymomas PFS was found to be significantly reduced for p27 LI < 20%, p14ARF LI < 10%, for p53 positivity, and for AI < 1%. The CART modeling process exhibited five final groups of ependymoma patients (1) low-grade and tenascin-negative; (2) low-grade and tenascin-positive; (3) high-grade and p53-negative with p14 LI > 0%; (4) high-grade with combination of either p53 positivity and p14 LI > 10% or p53 negativity and p14 LI < 10%; (5) high-grade and p53-positive with pl4 LI < 10%. In summary, some immunohistochemical variables were found to be the strong predictors of ependymoma recurrence and they seem to be useful for assessing individual tumor prognosis in routinely processed biopsy specimens together with tumor grade. For histologically benign ependymomas immunohistochemical study should be focused on Ki-S1, tenascin, EGFR and VEGF evaluation, whereas p53 expression and number of p27, p14 and ISEL-positive nuclei will be of value in determining PFS from high-grade ependymomas.

Immunohistochemical study of Ki-67 (MIB-1), p53 protein, p21WAF1, and p27KIP1 expression in benign, atypical, and anaplastic meningiomas

Histologic grading of meningiomas has prognostic and clinical therapeutic implications. Meningiomas were histologically classified into 3 different World Health Organization grades. Grade II, an atypical meningioma, was defined by major and various minor histologic criteria. However, these histologic criteria sometimes are not fulfilled, and other criteria are necessary. We studied and analyzed the immunohistochemical expression of MIB-1, p53, p21WAF1, p27KIP1 proteins in 146 cases of meningiomas, including 109 benign, 27 atypical, and 10 anaplastic meningiomas. Most of the benign meningiomas expressed low MIB-1 labeling index (mean, 1.5%), and fewer cases had p53 protein expression. In contrast, the anaplastic meningiomas had a high labeling index of MIB-1 (mean, 19.5%) and always expressed p53 protein, with a mean labeling index of 6.3%. The atypical meningiomas had MIB-1 and p53 labeling indexes in the range between benign and anaplastic meningiomas, with mean labeling indexes of 8.1% and 3.5%, respectively. These expressions were statistically significant among benign, atypical, and anaplastic meningiomas (P <.001). We conclude that the immunohistochemistry of MIB-1 and p53 protein will be valuable in discriminating atypical meningiomas from benign or anaplastic meningiomas, at least in histologically borderline cases. In addition, we also found direct correlation of p21 and inverse correlation of p27 expressions in meningiomas with increasing histologic grade and proliferative index.

CDKN2A/p16 in ependymomas

Sixteen cases of ependymoma were studied for CDKN2A/p16 inactivation by immunohistochemistry using a p16 monoclonal antibody, by homozygous deletion (HD) assay and 5'CpG promoter methylation assay (methylation-specific PCR). Three out of 16 cases were p16 immuno-negative: two corresponded to grade II ependymomas and one to grade III. The latter ependymoma, characterized by a high Ki-67/MIB-1 LI, was the only one of the whole series to show CDKN2A HD. No promoter methylation was found in the two immuno-negative cases without CDKN2A HD. Alternative mechanisms, such as point mutations or alterations in p16 post-translational regulation, may be responsible for p16 inactivation. Since in our series just one out of eight anaplastic cases showed negative immunostaining and CDKN2A HD, p16/CDKN2A inactivation may not play an important role in the malignant transformation of ependymomas. Amplification of CCNDI and CDK4, p27/Kipl degradation and TP53 mutations were previously studied by other authors and were demonstrated not to correlate with anaplasia. Up to date, molecular genetic studies have not been useful in recognizing the anaplastic variant in ependymomas.

The Hedgehog and Wnt signalling pathways in cancer

The Wnt and Hedgehog (Hh) signalling pathways have long been known to direct growth and patterning during embryonic development. Recent evidence also implicates these pathways in the postembryonic regulation of stem-cell number in epithelia such as those of the skin and intestine, which undergo constant renewal. A pathological role for the Wnt and Hh pathways has emerged from studies showing a high frequency of specific human cancers associated with mutations that constitutively activate the transcriptional response of these pathways. This article focuses on Hh and Wnt signal transduction and reviews evidence suggesting that tumorigenesis associated with pathway activation may result from mis-specification of cells towards stem-cell or stem cell-like fates.

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.

Immunohistochemical markers for intracranial ependymoma recurrence. An analysis of 88 cases

Intracranial ependymomas are the third most common primary brain tumor in children. Although clinical and histological criteria for ependymoma prognosis are recognized, studies have reported contradictory results. Prognostic significance based on immunohistochemistry of ependymomas has been reported in a few studies. Eighty-eight patients with intracranial ependymomas were examined retrospectively for immunoexpression of various tumor-associated antigens and apoptosis. The results demonstrated significant preponderance of expression of the tenascin, vascular endothelial growth factor protein (VEGF), epidermal growth factor (EGFR), and p53 protein in high-grade tumors. Also high-grade ependymomas revealed more prominent labeling indices (LI) for proliferative marker Ki-S1 and lower LI for cyclin-dependent kinase inhibitor p27/Kip1. For low-grade ependymomas the progression free survival time (PFS) was found to be significantly shorter for Ki-S1 LI>/=5%, and for tenascin, VEGF, and EGFR positivity. For high-grade ependymomas PFS was found to be significantly reduced for age <16 years, subtotal tumor removal, p27 LI <20%, p53 positivity, and for apoptotic index (AI) <1%. The classification regression tree analysis exhibited four groups of ependymomas; (1) low-grade tenascin negative (32 cases, recurrence rate=0), (2) high-grade with AI >/=1% (21 cases, recurrence rate=57%), (3) low-grade tenascin-positive (10 cases, recurrence rate=89%), and (4) high-grade with AI <1% (25 cases, recurrence rate=100%). So, the immunohistochemical variables were found to be strongest predictors of ependymoma recurrence and they seem to be useful for assessing individual tumor prognosis in routinely processed biopsy specimen.

p27Kip1 expression by contact inhibition as a prognostic index of human glioma

The clinical manifestations of human glioma are known to be diverse, ranging from aggressive growth and invasion to apparent dormancy; however, the molecular mechanism underlying this diversity has been largely unexplored. In the present study, we characterized four human glioma cell lines, T98G, A172, U251, and NAC6, each of which has distinct growth properties. A172 and U251 cells continue to grow after confluency, whereas the growth of T98G and NAC6 cells is contact inhibited. Northern and western blot analyses revealed that at high cell density, the expression of p27Kip1 cyclin-dependent kinase inhibitor was dramatically enhanced at both the RNA and the protein levels in T98G and NAC6 cells but not in A172 or U251. These facts together with the finding that overexpression of p27Kip1 caused G1 arrest in A172 and T98G cells suggest that the induction of p27Kip1 represents an important determinant of growth at high cell density. Immunohistochemical analyses of 42 primary gliomas revealed an inverse correlation between the level of p27 protein and the Ki-67 proliferative index. Kaplan-Meier plots demonstrated that a low level of p27 in tumors is associated with decreased overall survival. Thus, disrupted regulation of p27 expression at high cell density may play an important role in determining the clinical behavior of human gliomas as well as the prognosis for glioma patients.