Prognostic significance of proliferating cell nuclear antigen (PCNA) expression in gliomas

The Epigenetic Evolution of Glioma Is Determined by the IDH1 Mutation Status and Treatment Regimen

Tumor adaptation or selection is thought to underlie therapy resistance in glioma. To investigate longitudinal epigenetic evolution of gliomas in response to therapeutic pressure, we performed an epigenomic analysis of 132 matched initial and recurrent tumors from patients with IDH-wildtype (IDHwt) and IDH-mutant (IDHmut) glioma. IDHwt gliomas showed a stable epigenome over time with relatively low levels of global methylation. The epigenome of IDHmut gliomas showed initial high levels of genome-wide DNA methylation that was progressively reduced to levels similar to those of IDHwt tumors. Integration of epigenomics, gene expression, and functional genomics identified HOXD13 as a master regulator of IDHmut astrocytoma evolution. Furthermore, relapse of IDHmut tumors was accompanied by histologic progression that was associated with survival, as validated in an independent cohort. Finally, the initial cell composition of the tumor microenvironment varied between IDHwt and IDHmut tumors and changed differentially following treatment, suggesting increased neoangiogenesis and T-cell infiltration upon treatment of IDHmut gliomas. This study provides one of the largest cohorts of paired longitudinal glioma samples with epigenomic, transcriptomic, and genomic profiling and suggests that treatment of IDHmut glioma is associated with epigenomic evolution toward an IDHwt-like phenotype.

SIGNIFICANCE

Standard treatments are related to loss of DNA methylation in IDHmut glioma, resulting in epigenetic activation of genes associated with tumor progression and alterations in the microenvironment that resemble treatment-naïve IDHwt glioma.

Novel studies on Isolation, purification and characterization of dibenzonitro compound from Glycosmis pentaphylla (Retz.) DC. and effect in downregulating neuronal cancers

To isolate Letrozole from Glycosmis pentaphylla (Retz.) DC. and to determine its effect on regulating the proliferation, cell cycle distribution, apoptosis and key mechanisms in human neuroblastoma cell lines. Letrozole was isolated through column chromatographic technique and its effect was checked on human neuroblastoma cell lines, IMR 32. The effects of Letrozole on cell viability were measured by MTT assay, and the cell cycle distribution was determined by flow cytometry. The expression changes in mRNA of proliferating cell nuclear antigen (PCNA), cyclin D1 and Bcl-xL were taken from real-time PCR analysis and the protein levels were detected by Western blotting. The results of the present study showed that Letrozole, isolated from leaves of G. pentaphylla could cause significant inhibitory effect on proliferation of IMR 32 cells in a dose dependent manner. Cell arrest was obtained at S phase with the treatment of Letrozole. Apart from this, the expression of PCNA, cyclin D1 and Bcl-xL were decreased both at mRNA and protein levels for the same treatment. Letrozole can inhibit proliferation, induce cell arrest and cause apoptosis in IMR 32 cell lines. The decreased expression of PCNA, cyclin D1 and Bcl-xL induced by Letrozole contributes to the above effects in vitro. This is the first report on the isolation of Letrozole from G. pentaphylla.

Differential expression of the circadian clock network correlates with tumour progression in gliomas

BACKGROUND

Gliomas are tumours arising mostly from astrocytic or oligodendrocytic precursor cells. These tumours are classified according to the updated WHO classification from 2021 in 4 grades depending on molecular and histopathological criteria. Despite novel multimodal therapeutic approaches, the vast majority of gliomas (WHO grade III and IV) are not curable. The circadian clock is an important regulator of numerous cellular processes and its dysregulation had been found during the progression of many cancers, including gliomas.

RESULTS

In this study, we explore expression patterns of clock-controlled genes in low-grade glioma (LGG) and glioblastoma multiforme (GBM) and show that a set of 45 clock-controlled genes can be used to distinguish GBM from normal tissue. Subsequent analysis identified 17 clock-controlled genes with a significant association with survival. The results point to a loss of correlation strength within elements of the circadian clock network in GBM compared to LGG. We further explored the progression patterns of mutations in LGG and GBM, and showed that tumour suppressor APC is lost late both in LGG and GBM. Moreover, HIF1A, involved in cellular response to hypoxia, exhibits subclonal losses in LGG, and TERT, involved in the formation of telomerase, is lost late in the GBM progression. By examining multi-sample LGG data, we find that the clock-controlled driver genes APC, HIF1A, TERT and TP53 experience frequent subclonal gains and losses.

CONCLUSIONS

Our results show a higher level of disrgulation at the gene expression level in GBM compared to LGG, and indicate an association between the differentially expressed clock-regulated genes and patient survival in both LGG and GBM. By reconstructing the patterns of progression in LGG and GBM, our data reveals the relatively late gains and losses of clock-regulated glioma drivers. Our analysis emphasizes the role of clock-regulated genes in glioma development and progression. Yet, further research is needed to asses their value in the development of new treatments.

In vivo research in astrocytoma cell proliferation with 1H-magnetic resonance spectroscopy: correlation with histopathology and immunohistochemistry

INTRODUCTION

Assessment of brain tumor proliferative potential provides important prognostic information that supplements standard histopathologic grading. Proton magnetic resonance spectroscopy ((1)H-MRS) gives completely different information, relating to cell membrane proliferation, neuronal damage, energy metabolism and necrotic transformation of brain or tumor tissues. The aim of this study was to investigate the relationship between (1)H-MRS and tumor proliferative potential in astrocytomas.

METHODS

We studied 34 patients with histologically verified astrocytomas using the (1)H-MRS protocol following routine MRI preoperatively. The tumor in 26 of these patients was classified as grade I/II (low grade), and the tumor in the remaining patients as grade III/IV (high grade) according to the World Health Organization classification criteria of nervous system tumors (2000). The tumor in 21 patients was homogeneous astrocytoma, and of these 17 were classified as low grade and 4 as high grade. Expression of proliferating cell nuclear antigen (PCNA) was determined immunohistochemically using streptavidin-biotin-peroxidase complex (SP) staining.

RESULTS

The ratios of choline (Cho) to N-acetylaspartate (NAA) and Cho to creatine (Cr) in those with high-grade astrocytomas (n=4) were significantly higher than in those with low-grade astrocytomas (n=17) (t=2.899, P=0.009; t=3.96, P=0.001, respectively), and were found to be significantly correlated with the expression of PCNA in 21 patients with homogeneous astrocytomas (r=0.455, P=0.038; r=0.633, P=0.002, respectively).

CONCLUSIONS

We conclude that (1)H-MRS may be a valuable method for predicting preoperatively the degree of malignancy of homogeneous astrocytomas by enabling the calculation of the Cho/NAA and Cho/Cr ratios in vivo, and indirect evaluation of the tumor proliferative potential and prognosis, which are not available using conventional magnetic resonance imaging (MRI).

Cell proliferation and tumors of the central nervous system, part II: radiolabeling, cytometric, and immunohistochemical techniques

A variety of techniques have been developed to evaluate cell proliferation. Many of these methods provide a more accurate means of assessing the true proliferation rate of a given neoplasm, as compared with the simple assessment of mitotic activity. Similar to the evaluation of mitotic activity, these methods are also subject to limitations associated with tumor heterogeneity and interobserver variability. This paper reviews a variety of methodologies including radiolabeling, flow cytometric, and immunohistochemical that have been used in recent years to evaluate cell proliferation in brain neoplasms. Factors that affect these methodologies and their practical application to routine practice of diagnostic neuropathology will be explored.

Mitosin and DNA topoisomerase IIalpha: two novel proliferation markers in the prognostication of diffuse astrocytoma patient survival

The expression of two novel proliferation-associated markers, mitosin and topoisomerase IIalpha (Topo IIalpha), was evaluated immunohistochemically in consecutive paraffin sections from 60 diffuse astrocytomas (grades 2 to 4) in relation to clinicopathologic parameters, proliferating cell nuclear antigen (PCNA) and Ki-67 (MIB-1) expression and survival. The percentage of mitosin and Topo IIalpha-positive cells (LI) increased with grade and Ki-67 LI, but could not discriminate between grade 3 on the one hand and grades 2 or 4 on the other hand. In 51% of cases, Ki-67 LI exceeded Topo IIalpha LI, especially within grade 4. Topo IIalpha and mitosin expression was adversely related to overall and disease-free survival in the entire cohort and in grades 2/3. However, only Topo IIalpha LI affected disease-free survival in grade 4 tumors. Multivariate analysis selected only mitosin LI along with the age of the patient, as the independent parameters predicting overall survival, whereas Topo IIalpha emerged as the single independent predictor of disease-free survival. It is concluded that the proliferative potential of astrocytomas, as measured by mitosin and Topo IIalpha immunostaining, conveys useful prognostic information, in addition to that obtained by standard clinicopathologic parameters.

ASTROCYTOMAS AND PROGNOSIS-FROM MORPHOLOGY TO TUMOR BIOLOGY

Twenty-seven cases of Astrocytoma were studied to assess the role of a newly introduced proliferation marker-Proliferating Cell Nuclear Antigen (PCNA) in improving prognostic accuracy in comparison to traditional histologic methods like grading. The study revealed a direct correlation between grading and PCNA expression as determined by labelling indices (LI). A 25% PCNA LI separated low and high grade tumors. The difference between PCNA LI's of patients who were alive and those who were dead at the end of the study was statistically significant. However, in this study with limited follow-up, statistically significant relation to survival and recurrence could not be established. The study introduces a new method of assessing tumor biology that enables objectivity in prediction of tumor behaviour.

Immunohistochemical analysis of cyclin A in astrocytic tumours

Cyclins are important regulators of the cell cycle; there is increasing evidence that some cyclins are positively involved in carcinogenesis. Amplification and translocation of the cyclin genes and overexpression of their mRNAs and proteins have been observed in a variety of tumours. We studied cyclin A protein in astrocytic tumours by immunohistochemical analysis. Immunohistochemistry with microwave antigen retrieval was carried out on formalin fixed, paraffin embedded material from 15 glioblastomas (WHO grade IV), 10 anaplastic astrocytomas (WHO grade III), seven diffuse low grade astrocytomas (WHO grade II) and nine pilocytic astrocytomas (WHO grade I) using antibodies against cyclin A and a proliferation marker MIB1. Staining for these antibodies was seen mainly in the tumour cell nuclei; 66% of all cases showing staining for cyclin A and 95% of all cases staining for MIB1. Mean labelling indices (LI) for cyclin a were higher in glioblastoma (mean LI-6.7) and anaplastic astrocytoma (mean LI-5.9) than low grade diffuse astrocytoma (mean LI-1.7) and pilocytic astrocytoma (mean LI-0.12), although there was no clear cut off point between the various tumour types. A good correlation was seen between labelling indices of cyclin A and MIB1 (Pearson correlation coefficient r = 0.59, P < 0.0001). Cyclin A is variably expressed in astrocytic tumours, either reflecting increased tumour proliferation (cyclin A being an integral component of the cell cycle), an alteration of its gene, protein upregulation or regulation of apoptosis. The genetic basis of expression of cyclin A in astrocytic tumours remains to be determined.

Insights about brain tumors gained through immunohistochemistry and in situ hybridization of nuclear and phenotypic markers

Immunohistochemistry (IHC) has provided major insights about the classification of brain tumors by identifying cellular markers of phenotype and about tumor growth potential with nuclear markers of proliferation. In situ hybridization (ISH) research shows promise for diagnostic applications in tumor classification. The avidin-biotin conjugate IHC procedure is highlighted for diagnostic use on routinely processed clinical specimens. The immunophenotypes of brain tumors are tabulated in reference to their common IHC markers. Tumors that have been correctly classified by their IHC phenotypes include the giant-cell glioblastoma, primary brain lymphoma, and central neurocytoma. Phenotypes that may be more definitively detected by ISH, such as pituitary hormone, immunoglobulin light chain, and collagen messages are described. IHC of nuclear proliferation markers correlates with grade of malignancy, predicts tumor growth potential, and is prognostic for patient survival. The incorporation of bromodeoxyuridine, the expression of proliferating cell nuclear antigen, and the expression of Ki-67 antigen detected by MIB-1 antibody are compared in regard to their cell cycle activity and labeling index determinations. Fluorescence in situ hybridization (FISH) of brain tumor interphase nuclei and chromosomes is described. Abnormal FISH signals of specific chromosomes are associated with different types of brain tumors, with different grades of malignancy, and with mesenchymal drift of glioma cells in culture.

Assessment of proliferating cell nuclear antigen expression and prognosis in patients with renal cell carcinoma with pulmonary metastases

BACKGROUND

The presence of proliferating cell nuclear antigen (PCNA) has been suggested as a more important prognostic marker than either grade or mitotic index in the prognosis of patients with renal cell carcinoma. We assessed the immunoreactivity of PCNA in primary lesions and pulmonary metastases from patients with renal cell carcinoma and correlated the results with various histopathologic features and prognostic factors.

METHODS

We studied the relationship between PCNA expression and clinical prognostic factors from resected primary lesions and pulmonary metastases from 10 patients and primary lesions from 32 patients with renal cell carcinoma without metastases. The cells were immunohistochemically stained with PCNA monoclonal antibody (PC-10) and 1000 nuclei were counted. The results were expressed as a ratio of stained to total cells (PCNA labeling index, LI %).

RESULTS

The PCNA LI of pulmonary metastatic nuclei was significantly higher than the PCNA LI of renal lesions either from patients with (P < 0.05) or without (P < 0.01) metastases. Also, the mean PCNA LI of the pulmonary lesions in patients dying within 3 years of diagnosis was higher than the mean PCNA LI of patients surviving greater than 3 years.

CONCLUSION

Our findings suggest that the PCNA LI, which was determined by immunohistochemical analysis, is an important marker reflecting the biologic behavior of renal cell carcinomas. The degree of PCNA expression in this study was of prognostic significance.

Analysis of proliferation markers and p53 expression in gliomas of astrocytic origin: relationships and prognostic value

Consecutive paraffin sections of 105 astrocytomas and 15 oligoastrocytomas were examined for expression of p53, MIB-1 (Ki-67), and proliferating cell nuclear antigen (PCNA). The tumors had been examined previously for genetic abnormalities and by flow cytometry. Regardless of the tumor's stage and grade and the patient's age and gender, p53 expression was found in 40% of tumors. Although p53 expression was associated with a loss on chromosome 17p and was more frequent in aneuploid tumors, it had no association with survival time. The MIB-1 and PCNA labeling indices increased with increasing tumor grade but showed no association with other clinicopathological parameters. In individual tumors, there was poor concordance between any of the variables (MIB-1, PCNA, and p53). Results for p53 and MIB-1 were similar for both astrocytomas and oligoastrocytomas. The MIB-1 and PCNA values appeared to have prognostic utility in univariate analysis but not after adjusting for patient age and tumor grade. The poor concordance between MIB-1 and PCNA in individual tumors indicates that any one means of assessing proliferative potential in gliomas may not be reliable.

MDM2 and p53 expression in gliomas: a multivariate survival analysis including proliferation markers and epidermal growth factor receptor

p53 and the murine double minute 2 (MDM2) oncoprotein expression was evaluated in paraffin-embedded tissue from 61 patients with central nervous system gliomas (53 astrocytomas and eight oligodendrogliomas) and related to proliferation-associated markers [i.e. proliferating cell nuclear antigen (PCNA), Ki-67 and nuclear organizer regions (NORs)] and epidermal growth factor receptor (EGFR). We used the monoclonal antibodies PC-10, MIB-1, DO-1, 1B1O and EGFR 113 and the colloid silver nitrate (AgNOR) technique. MDM2 and p53 were co-expressed in 28% of cases. A p53-positive/MDM2-negative phenotype was observed in 15% and a p53-negative/MDM2-positive phenotype in 20% of cases. There was a positive correlation of p53 and MDM2 expression with grade and proliferation indices. Univariate analysis in the group of diffuse astrocytomas showed that older age, high histological grade, high PCNA labelling index (LI) and high AgNOR score were associated with reduced overall survival (P < 0.05). p53 LI, Ki-67 LI, AgNOR score, tumour location and grade influenced disease-free survival (P < 0.05), whereas the only parameters affecting post-relapse survival were histological grade and Ki-67 LI (P < 0.1). Multivariate analysis revealed that age, radiotherapy, PCNA LI and p53 LI were the independent predictors of overall survival. p53 LI, Ki-67 LI, MDM2 LI, EGFR LI, grade and type of therapy were independent predictors of disease-free survival, and grade was the only independent predictor of post-relapse survival. Our results indicate that p53 LI and MDM2 LI, EGFR expression as well as proliferation markers (PCNA and Ki-67) are useful indicators of overall and disease-free survival in diffuse astrocytoma patients.

Cell kinetic analysis in recurrent neuro-epithelial tumours

The biological behaviour of brain tumours is variable. In the majority of cases, recurrence of the tumour is the decisive factor determining the prognosis and individual survival of patients suffering from a neuro-epithelial neoplasm. The time course of recurrences varies significantly according to differences in tumour cell proliferation. In this study, predictive factors concerning the expected prognosis following the resection of neuro-epithelial tumours were investigated with the aim of improving the histological diagnosis. A retrospective analysis of 22 recurrent neuro-epithelial tumours (recurrent tumour group) and 12 neuro-epithelial tumours with a minimum survival rate of 5 years following radical excision (cured tumour group) was performed by means of flow cytometry and immunohistochemistry using the MIB 1 antibody. Histological samples of the subgroups of the recurrent tumour group, i. e., the primary tumours and their recurrences were compared with each other, and the subgroups were compared with the cured tumour group. A multivariate analysis of the data was performed with the BMPD Hotteling T square test. A statistically significant difference was found between the recurrent tumour group (primary tumours + recurrences) and the cured group from every investigated aspect. On the other hand, no difference could be found between the sub-groups primary tumours and their recurrences. All tumours in the recurrent group had an accelerated, active cell cycle, which was expressed in a high proliferation activity. The following conclusion was drawn: an increased risk of recurrence is to be expected in neuro-epithelial tumours characterized by: an S-phase fraction higher than 6-9%, an MIB 1-labelled cell number higher than 2-3/high-power fields, and a number of mitoses higher than 1/10 high-power fields.

Functional characterization of brain tumors: an overview of the potential clinical value

Early detection and characterization are still challenging issues in the diagnostic approach to brain tumors. Among functional imaging techniques, a clinical role for positron emission tomography studies with [18F]-fluorodeoxyglucose and for single photon emission computed tomography studies with [201Tl]-thallium-chloride has emerged. The clinical role of magnetic resonance spectroscopy is still being defined, whereas functional magnetic resonance imaging seems able to provide useful data for presurgical localization of critical cortical areas. Integration of morphostructural information provided by computed tomography and magnetic resonance imaging, with functional characterization and cyto-histologic evaluation of biologic markers, may assist in answering the open diagnostic questions concerning brain tumors.

Cyclin D1 in astrocytic tumours: an immunohistochemical study

Forty-eight astrocytic tumours were stained immunohistochemically with antibodies to the cell cycle-regulating protein, cyclin D1, and to the proliferation marker MIB1 (Ki-67) using formalin fixed paraffin embedded tissue and a microwave antigen retrieval system. Cases were classified by the WHO system (1993). The labelling indices (LI) for both antibodies were compared with each other and with the tumour type. The mean labelling indices for both antibodies increased with the degree of malignancy, and a significant difference was seen between the pilocytic astrocytoma and diffuse astrocytoma together vs anaplastic astrocytoma and glioblastoma together. However, within each tumour type there was considerable variation in the labelling indices and a clear cut off value could not be demonstrated. There was a strong positive correlation between labelling indices for cyclin D1 and MIB1 in diffuse astrocytoma, but this correlation broke down increasingly in anaplastic astrocytoma and glioblastoma. There was poor correlation between cyclin D1 and MIB1 in pilocytic astrocytoma, a feature which appeared to separate them from the diffuse astrocytoma. Average labelling indices for cyclin D1 were higher than those of MIB1, which suggests that cyclin D1 positive cells represent a pool of cells from which proliferation and hence MIB1 expression can take place. In conclusion, cyclin D1 is overexpressed in astrocytic tumours, more so with increasing grade of malignancy and in a way which approximately correlates with MIB1 expression.