Immunohistochemical analysis of cyclin A in astrocytic tumours

Therapeutic potential of parkin as a tumor suppressor via transcriptional control of cyclins in glioblastoma cell and animal models

Parkin (PK) is an E3-ligase harboring tumor suppressor properties that has been associated to various cancer types including glioblastoma (GBM). However, PK is also a transcription factor (TF), the contribution of which to GBM etiology remains to be established.

Methods: The impact of PK on GBM cells proliferation was analyzed by real-time impedance measurement and flow cytometry. Cyclins A and B proteins, promoter activities and mRNA levels were measured by western blot, luciferase assay and quantitative real-time PCR. Protein-protein and protein-promoter interactions were performed by co-immunoprecipitation and by ChIP approaches. The contribution of endogenous PK to tumor progression in vivo was performed by allografts of GL261 GBM cells in wild-type and PK knockout mice.

Results: We show that overexpressed and endogenous PK control GBM cells proliferation by modulating the S and G2/M phases of the cell cycle via the trans-repression of cyclin A and cyclin B genes. We establish that cyclin B is regulated by both E3-ligase and TF PK functions while cyclin A is exclusively regulated by PK TF function. PK invalidation leads to enhanced tumor progression in immunocompetent mice suggesting an impact of PK-dependent tumor environment to tumor development. We show that PK is secreted by neuronal cells and recaptured by tumor cells. Recaptured PK lowered cyclins levels and decreased GBM cells proliferation. Further, PK expression is decreased in human GBM biopsies and its expression is inversely correlated to both cyclins A and B expressions.

Conclusion: Our work demonstrates that PK tumor suppressor function contributes to the control of tumor by its cellular environment. It also shows a key role of PK TF function in GBM development via the control of cyclins in vitro and in vivo. It suggests that therapeutic strategies aimed at controlling PK shuttling to the nucleus may prove useful to treat GBM.

Molecular neuro-oncology and the development of targeted therapeutic strategies for brain tumors. Part 5: apoptosis and cell cycle

Brain tumors are a diverse group of malignancies that remain refractory to conventional treatment approaches. Molecular neuro-oncology has now begun to clarify the transformed phenotype of brain tumors and identify oncogenic pathways that might be amenable to targeted therapy. Abnormalities of the apoptotic and cell cycle signaling pathways are key molecular features of many brain tumors and are currently under evaluation for potential therapeutic intervention. The apoptosis pathway has numerous targets for molecular therapeutic development, including p53, Bax, Bcl-2, cFLIP, effector caspases, growth factor receptors, phosphatidylinositol-3-kinase, Akt and apoptosis inhibitors. Current molecular treatment approaches include antisense techniques, gene therapy and small-molecule modulators and inhibitors. Potential targets of the cell cycle pathway include the cyclins, cyclin-dependent kinases, p53, retinoblastoma, E2F and the cyclin-dependent kinase inhibitors. Developmental molecular therapeutics for this pathway include adenoviral and gene therapy, small-peptide cyclin-dependent kinase modulators, proteasomal inhibitors and small-molecule cyclin-dependent kinase inhibitors. Several of these recently identified agents have begun evaluation in clinical trials. Further development of targeted therapies designed to modulate apoptosis and the cell cycle, and evaluation of these new agents in clinical trials, will be needed to improve survival and quality of life for patients with brain tumors.

Immunohistochemical estimation of cell cycle entry and phase distribution in astrocytomas: applications in diagnostic neuropathology

An immunohistochemical method for assessing cell cycle phase distribution in neurosurgical biopsies would enable such data to be incorporated into diagnostic algorithms for the estimation of prognosis and response to adjuvant chemotherapy in glial neoplasms, without the requirement for flow cytometric analysis. Paraffin-embedded sections of intracerebral gliomas (n = 48), consisting of diffuse astrocytoma (n = 9), anaplastic astrocytoma (n = 8) and glioblastoma (n = 31), were analysed by immunohistochemistry using markers of cell cycle entry, Mcm-2 and Ki67, and putative markers of cell cycle phase, cyclins D1 (G1-phase), cyclin A (S-phase), cyclin B1 (G2-phase) and phosphohistone H3 (Mitosis). Double labelling confocal microscopy confirmed that the phase markers were infrequently coexpressed. Cell cycle estimations by immunohistochemistry were corroborated by flow cytometric analysis. There was a significant increase in Mcm-2 (P < 0.0001), Ki67 (P < 0.0001), cyclin A (P < 0.0001) and cyclin B1 (P = 0.002) expression with increasing grade from diffuse astrocytoma through anaplastic astrocytoma to glioblastoma, suggesting that any of these four markers has potential as a marker of tumour grade. In a subset of glioblastomas (n = 16) for which accurate clinical follow-up data were available, there was a suggestion that the cyclin A:Mcm-2 labelling fraction might predict a relatively favourable response to radical radiotherapy. These provisional findings, however, require confirmation by a larger study. We conclude that it is feasible to obtain detailed cell cycle data by immunohistochemical analysis of tissue biopsies. Such information may facilitate tumour grading and may enable information of prognostic value to be obtained in the routine diagnostic laboratory.

Expression of cyclin A and topoisomerase IIalpha of oligodendrogliomas is correlated with tumour grade, MIB-1 labelling index and survival

AIMS

This study was designed to investigate immunoexpression of cyclin A and D1, and topoisomerase IIalpha in oligodendrogliomas and to evaluate the correlation with MIB-1 (Ki67), tumour grade, and survival of the patients.

METHODS AND RESULTS

Forty cases of oligodendrogliomas (20 high- and 20 low-grade) were studied immunohistochemically with the above-mentioned monoclonal antibodies.

RESULTS

Normal brain tissues included in tumour sections did not express any of cyclin A, MIB-1 and topoisomerase IIalpha except cyclin D1, which was shown in perineuronal and interfascicular normal oligodendroglial cells. In low-grade and high-grade oligodendrogliomas, the mean cyclin A labelling index (LI) was 1.18 +/- 0.98% versus 4.65 +/- 1.99%, respectively; the mean topoisomerase IIalpha LI was 1.32 +/- 1.04% versus 6.63 +/- 4.31%, respectively; and the mean MIB-1 LI was 1.69 +/- 1.55% versus 9.46 +/- 4.66%, respectively. Interestingly, cyclin D1 was not expressed in any oligodendrogliomas. Both cyclin A and topoisomerase IIalpha LI showed a significant positive correlation with MIB-1 LI and histological grade of oligodendrogliomas (P < 0.01) and an inverse correlation with overall survival (P < 0.01). Univariate analysis showed that cyclin A and topoisomerase IIalpha LIs with a cut-off point at 3% were a significant prognostic factor (P: cyclin A = 0.0040, topoisomerase IIalpha = 0.0033).

CONCLUSION

Cyclin A and topoisomerase IIalpha expression are closely correlated with anaplastic oligodendrogliomas and worse clinical outcomes. Cyclin D1 seems not to be involved in the tumorigenesis of oligodendrogliomas.

Genetic alterations of human brain tumors as molecular prognostic factors

Despite a number of basic and clinical studies, it is still very difficult to improve the prognosis of patients with high-grade astrocytoma. However, the recent success of procarbazine, N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea and vincristine (PCV) chemotherapy for oligodendrogliomas that have lost chromosomes 1p and 19q has encouraged the authors to evaluate the biological behavior of brain tumors by means of genetic analysis. Both the disorders of the p53/MDM2/p14(ARF) and the p16(INK4a)/RB signaling pathways have been found to play an essential role in tumorigenesis of various brain tumors. Herein, the authors summarize the genetic alterations of brain tumors by mainly focusing on two pathways that appear to affect significantly the patient prognosis.

Prognostic significance of cyclin a expression in meningiomas

Unconstrained cell proliferation is characteristic of tumors. It is caused by the functional disorders of proteins that constitute the cell cycle mechanism. The cell cycle is controlled by cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors. Many reports have proved, in cancers, that cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors are out of control. Cyclin A is a protein that regulates critical transition of the cell cycle. The expression of cyclin A in meningiomas by immunohistochemical method was investigated. Furthermore, the correlation among cyclin A expression, clinical course, and proliferative potential were also evaluated. Seventy-seven meningiomas were studied. The mean cyclin A labeling indices were as follows: benign meningiomas, 1.01% +/- 0.62%; atypical meningiomas, 4.23% +/- 1.82%; and anaplastic meningiomas, 7.72% +/- 0.88%. Analyses of variance showed that significant differences existed between tumor grades for cyclin A labeling indices. A linear positive correlation between the cyclin A labeling index and bromodeoxyuridine labeling index was observed. The multivariate analysis using Cox's hazards model showed a high cyclin A labeling index (>3%) was a significant risk factor for recurrence. A high Ki-67 labeling index (>5%) and high tumor grade (World Health Organization grade II, III) were also significant risk factors for recurrence. These results suggested that the evaluation of cyclin A expression in meningiomas provides significant clinical information, especially as an independent prognostic indicator.

DNA topoisomerase II-alpha and cyclin A immunoexpression in meningiomas and its prognostic significance: an analysis of 263 cases

CONTEXT

Routine pathologic examination cannot distinctively predict the clinical course of meningiomas because even histologically benign tumors may recur after gross total resection. Therefore, numerous efforts have been made to evaluate the meningioma growth fraction and its prognostic value. However, a universally applicable proliferative marker for meningioma outcome is not yet a reality.

OBJECTIVE

To investigate the prognostic utility of 3 proliferative markers, namely, Ki-67, DNA topoisomerase II-alpha (topoII), and cyclin A in a representative series of intracranial meningiomas.

DESIGN

Two hundred sixty-three adult patients with intracranial meningiomas (208 benign, 42 atypical, and 13 anaplastic) were studied retrospectively. Tumor specimens were immunohistochemically examined with antibodies to Ki-67 (MM-1), topoII, and cyclin A. A computerized color image analyzer was used to count immunostained nuclei.

RESULTS

The topoII and cyclin A scores exhibited a close correlation with Ki-67 immunostaining. Significant differences between the indices for all 3 markers were noted among the 3 grades of meningiomas. The scores for all 3 markers were significantly different between recurrent and nonrecurrent meningiomas, including benign tumors that were treated with gross total resection. Recurrence-free survival was significantly reduced for cases with a Ki-67 labeling index (LI) of 4.4% or greater, a topoII LI of 3.2% or greater, and a cyclin A LI of 3.1% or greater. Multivariate analysis revealed that the risk of recurrence for the entire meningioma cohort was significantly associated with tumor grade (hazard ratio = 2.7; P =.004), topoII LI of 3.2% or greater (hazard ratio = 5.5; P <.001), and a cyclin A LI of 3.1% or greater (hazard ratio = 2.4; P =.01).

CONCLUSIONS

There is a close correlation in the expression of these 3 proliferative markers in meningiomas, and all of the markers showed a significant association with tumor grade, recurrence rate, and recurrence-free survival. Consequently, in addition to Ki-67, immunoexpression of topoII and cyclin A is available for predicting meningioma recurrence. Moreover, the topoII and cyclin A staining scores were found to be more sensitive predictors for meningioma progression than Ki-67 and, therefore, either of these 2 markers may prove to be clinically informative and useful.

Immunohistochemical markers for prognosis of anaplastic astrocytomas

Among the entire spectrum of astrocytic neoplasms, just anaplastic astrocytoma (or grade III astrocytoma) appears to be a more enigmatic tumor entity with vague criteria for pathological diagnosis, unclear biological behavior and diverse clinical outcome. Attempts have been made to identify biological markers that would be useful in prediction of prognosis of anaplastic astrocytomas but the results obtained are controversial. In the present study, survival data on 63 patients with anaplastic astrocytoma were studied to evaluate a possible association between clinical outcome and expression of some immunohistochemical variables. Both the progression-free (PFS) and overall (OS) survival times were significantly reduced for patients older than 45 years, for anaplastic astrocytomas containing multiple mitoses, for Ki-67 LI > 5%, for cyclin A LI > 4% and for PTEN-negative tumors. We found no differences in survival times in patients with or without p53 immunoreactivity and also in cases with different values of p16 and p27 immunostaining. Multivariate analysis revealed that risk of tumor progression and death is independently associated with tumors containing multiple mitoses and for PTEN-negative tumors. According to the data from the CART modeling, tumors were subdivided based on the three following subsets: (1) Anaplastic astrocytomas with solitary mitosis. (2) Anaplastic astrocytomas with multiple mitoses and PTEN positivity. (3) Anaplastic astrocytomas with multiple mitoses and PTEN negativity. Thus, the results obtained reveal the advantage of combined approach including evaluation of routine histological parameters and immunohistochemical variables for further clinical subdivision of anaplastic astrocytomas.

Overexpression of cyclin A and cyclin B1 proteins in astrocytomas

BACKGROUND

Cyclins are proteins that are expressed during the progression of a normal cell through the cell cycle. In a number of cancers, overexpression of cyclin A and cyclin B1 proteins has been reported, and in some instances the levels of expression correlated well with the grades of malignancy. The expression of cyclin A and cyclin B1 proteins in astrocytoma may be linked to the histologic grade or proliferative activities.

OBJECTIVE

To study the expression of cyclin A and cyclin B1 proteins in astrocytomas and correlate the labeling indices (LIs) of cyclin A and cyclin B1 with histologic grade and Ki-67 LI.

DESIGN

The surgical biopsy specimens from 65 adults with astrocytomas were reviewed and divided into grades based on the World Health Organization system. The paraffin sections were immunostained using primary antibodies against Ki-67, cyclin A, and cyclin B1. The LIs of these astrocytomas for the 3 different antibodies were determined by computerized image analysis.

RESULTS

The cyclin A LI showed good correlation with astrocytoma grade and Ki-67 LI. Both the nuclear and cytoplasmic cyclin B LIs correlated well with the tumor grade but showed poor correlation with Ki-67 LI.

CONCLUSIONS

This study suggests that although both cyclin A and B protein expression are related to the grade of malignancy in astrocytomas, cyclin A levels more generally reflect the proliferative state of these tumors. We also provide indirect evidence that cyclin B1 is associated with the aberrant progression through the G2-M phase checkpoint in astrocytomas.