Overview and recent advances in neuropathology. Part 1: Central nervous system tumours

Correlation between levels of clock protein expression and effects on temozolomide-resistant glioblastoma and tumor progression

Glioblastoma (GBM) is the most common malignant intracranial neoplasm. Treatment with surgical resection and concurrent chemoradiotherapy may not achieve satisfactory results in life expectancy. Temozolomide (TMZ) chemoresistance is one of the most common reasons for treatment failure, but the role of the circadian cycle and autophagic pathways in this phenomenon is unknown. This study investigated the relationship between the circadian cycle and autophagic pathways in GBM and its TMZ chemoresistance counterpart. The predictive potential of NR1D1 and MGMT was analyzed by using 631 glioma cases derived from the TCGA GBM dataset. Human GBM cell lines (U-87 MG, GBM 8401) and their TMZ chemoresistance counterparts were used for MGMT, circadian proteins (CLOCK, BMAL1, NR1D1), and LC3B analysis. In addition, immunohistochemical staining for NR1D1 was performed in 78 GBM samples, and the results were analyzed with patients' clinicopathological parameters. Results revealed a decrease in NR1D1 expression in GBM cells which could enhance TMZ chemosensitivity. Different expressions of autophagic markers were also noted in GBM cell lines with and without TMZ chemoresistance, indicating a significant role for NR1D1 in TMZ chemoresistance in the GBM cell line. In addition, higher expression of NR1D1 in tumor samples was correlated with poor prognosis and shorter survival. In conclusion, high levels of NR1D1 not only could predict poor prognosis but it could also be used as a chemosensitizer for TMZ in GBM patients.

Hsc70 Interacts with β4GalT5 to Regulate the Growth of Gliomas

Heat shock cognate protein 70 (Hsc70) is a key mediator for the maintenance of intracellular proteins and regulates cellular activities. And it is elevated in various tumor tissues including glioma, which is closely related to the malignancy and poor prognosis of the tumors. However, the effects of Hsc70 on gliomas and its regulatory mechanism have not yet been elucidated. In the present study, we found that Hsc70 was overexpressed in glioma tissues and cultured glioma cells. Furthermore, Hsc70 expression exhibited positive correlation with the grades of gliomas. Knockdown of Hsc70 could effectively inhibit cell proliferation and increase cell apoptosis. Furthermore, we identified that β4GalT5 was a critical target for Hsc70-mediated anti-glioma effects. Blocking β4GalT5 activity could effectively reverse the anti-tumor effect of Hsc70. Taken together, these data indicate that Hsc70 regulates β4GalT5 levels, and possibly plays a role in cell proliferation and apoptosis of glioma.

Knockdown of DIXDC1 Inhibits the Proliferation and Migration of Human Glioma Cells

DIX domain containing 1 (DIXDC1), the human homolog of coiled-coil-DIX1 (Ccd1), is a positive regulator of Wnt signaling pathway. Recently, it was found to act as a candidate oncogene in colon cancer, non-small-cell lung cancer, and gastric cancer. In this study, we aimed to investigate the clinical significance of DIXDC1 expression in human glioma and its biological function in glioma cells. Western blot and immunohistochemistry analysis showed that DIXDC1 was overexpressed in glioma tissues and glioma cell lines. The expression level of DIXDC1 was evidently linked to glioma pathological grade and Ki-67 expression. Kaplan-Meier curve showed that high expression of DIXDC1 may lead to poor outcome of glioma patients. Serum starvation and refeeding assay indicated that the expression of DIXDC1 was associated with cell cycle. To determine whether DIXDC1 could regulate the proliferation and migration of glioma cells, we transfected glioma cells with interfering RNA-targeting DIXDC1; investigated cell proliferation with Cell Counting Kit (CCK)-8, flow cytometry assays, and colony formation analyses; and investigated cell migration with wound healing assays and transwell assays. According to our data, knockdown of DIXDC1 significantly inhibited proliferation and migration of glioma cells. These data implied that DIXDC1 might participate in the development of glioma, suggesting that DIXDC1 can become a potential therapeutic strategy for glioma.

Metabolomic Screening of Tumor Tissue and Serum in Glioma Patients Reveals Diagnostic and Prognostic Information

Glioma grading and classification, today based on histological features, is not always easy to interpret and diagnosis partly relies on the personal experience of the neuropathologists. The most important feature of the classification is the aimed correlation between tumor grade and prognosis. However, in the clinical reality, large variations exist in the survival of patients concerning both glioblastomas and low-grade gliomas. Thus, there is a need for biomarkers for a more reliable classification of glioma tumors as well as for prognosis. We analyzed relative metabolite concentrations in serum samples from 96 fasting glioma patients and 81 corresponding tumor samples with different diagnosis (glioblastoma, oligodendroglioma) and grade (World Health Organization (WHO) grade II, III and IV) using gas chromatography-time of flight mass spectrometry (GC-TOFMS). The acquired data was analyzed and evaluated by pattern recognition based on chemometric bioinformatics tools. We detected feature patterns in the metabolomics data in both tumor and serum that distinguished glioblastomas from oligodendrogliomas (p(tumor) = 2.46 × 10(-8), p(serum) = 1.3 × 10(-5)) and oligodendroglioma grade II from oligodendroglioma grade III (p(tumor) = 0.01, p(serum) = 0.0008). Interestingly, we also found patterns in both tumor and serum with individual metabolite features that were both elevated and decreased in patients that lived long after being diagnosed with glioblastoma compared to those who died shortly after diagnosis (p(tum)(o)(r) = 0.006, p(serum) = 0.004; AUROCC(tumor) = 0.846 (0.647-1.000), AUROCC(serum) = 0.958 (0.870-1.000)). Metabolic patterns could also distinguish long and short survival in patients diagnosed with oligodendroglioma (p(tumor) = 0.01, p(serum) = 0.001; AUROCC(tumor) = 1 (1.000-1.000), AUROCC(serum) = 1 (1.000-1.000)). In summary, we found different metabolic feature patterns in tumor tissue and serum for glioma diagnosis, grade and survival, which indicates that, following further verification, metabolomic profiling of glioma tissue as well as serum may be a valuable tool in the search for latent biomarkers for future characterization of malignant glioma.

Case comparison and literature review of glioblastoma: A tale of two tumors

Background:

Diagnosis of glioblastoma multiforme (GBM) includes a heterogeneous group of tumors. We describe two cases with histopathologically and molecularly similar tumors, but very different outcomes. We attempt to illustrate the need for improved prognostic markers for GBM.

Case Description:

Two patients with similar molecular profiles were retrospectively identified. The following markers were assessed: O⁶-methylguanine DNA methyltransferase (MGMT) methylation, isocitrate dehydrogenase (IDH) 1 and 2 status, epidermal growth factor receptor (EGFR) amplification, phosphatase and tensin homolog (PTEN) status, Ki-67, p53, and 1p/19q status. Each patient was assigned a Karnofsky performance score at presentation. Case 1 (62-year-old male) was a right temporal lobe glioblastoma with a molecular profile of amplified EGFR, normal PTEN, no IDH1/2 mutation, 28.7% MGMT promoter methylation, 5-20% Ki-67, 1p deletion, and 19q intact. The patient underwent resection followed by radiation therapy and 2 years of chemotherapy, and was asymptomatic and tumor free 5 years post diagnosis. Tumor eventually recurred and the patient expired 72 months after initial diagnosis. Case 2 (63-year-old male) was a right frontal white matter mass consistent with glioblastoma with a molecular profile of amplified EGFR, absent PTEN, no IDH1/2 mutation, 9.9% MGMT promoter methylation, 5-10% Ki-67, and 1p/19q status inconclusive. A radical subtotal resection was performed; however, 2 weeks later symptoms had returned. Subsequent imaging revealed a tumor larger than at diagnosis. The patient expired 3 months after initial diagnosis.

Conclusion:

The need for formulating more robust means to classify GBM tumor subtypes is paramount. Standard histopathologic and molecular analyses are costly and did not provide either of these patients with a realistic appraisal of their prognosis. Individualized whole genome testing similar to that being reported for medulloblastoma and other tumors may be preferable to the array of tests as currently utilized.

Addition of MR imaging features and genetic biomarkers strengthens glioblastoma survival prediction in TCGA patients

PURPOSE

The purpose of our study was to assess whether a model combining clinical factors, MR imaging features, and genomics would better predict overall survival of patients with glioblastoma (GBM) than either individual data type.

METHODS

The study was conducted leveraging The Cancer Genome Atlas (TCGA) effort supported by the National Institutes of Health. Six neuroradiologists reviewed MRI images from The Cancer Imaging Archive (http://cancerimagingarchive.net) of 102 GBM patients using the VASARI scoring system. The patients' clinical and genetic data were obtained from the TCGA website (http://www.cancergenome.nih.gov/). Patient outcome was measured in terms of overall survival time. The association between different categories of biomarkers and survival was evaluated using Cox analysis.

RESULTS

The features that were significantly associated with survival were: (1) clinical factors: chemotherapy; (2) imaging: proportion of tumor contrast enhancement on MRI; and (3) genomics: HRAS copy number variation. The combination of these three biomarkers resulted in an incremental increase in the strength of prediction of survival, with the model that included clinical, imaging, and genetic variables having the highest predictive accuracy (area under the curve 0.679±0.068, Akaike's information criterion 566.7, P<0.001).

CONCLUSION

A combination of clinical factors, imaging features, and HRAS copy number variation best predicts survival of patients with GBM.

Serine/threonine kinase 17A is a novel candidate for therapeutic targeting in glioblastoma

STK17A is a relatively uncharacterized member of the death-associated protein family of serine/threonine kinases which have previously been associated with cell death and apoptosis. Our prior work established that STK17A is a novel p53 target gene that is induced by a variety of DNA damaging agents in a p53-dependent manner. In this study we have uncovered an additional, unanticipated role for STK17A as a candidate promoter of cell proliferation and survival in glioblastoma (GBM). Unexpectedly, it was found that STK17A is highly overexpressed in a grade-dependent manner in gliomas compared to normal brain and other cancer cell types with the highest level of expression in GBM. Knockdown of STK17A in GBM cells results in a dramatic alteration in cell shape that is associated with decreased proliferation, clonogenicity, migration, invasion and anchorage independent colony formation. STK17A knockdown also sensitizes GBM cells to genotoxic stress. STK17A overexpression is associated with a significant survival disadvantage among patients with glioma which is independent of age, molecular phenotype, IDH1 mutation, PTEN loss, and alterations in the p53 pathway and partially independent of grade. In summary, we demonstrate that STK17A provides a proliferative and survival advantage to GBM cells and is a potential target to be exploited therapeutically in patients with glioma.

TP53 mutations in astrocytic gliomas: an association with histological grade, TP53 codon 72 polymorphism and p53 expression

TP53 mutations and polymorphisms have been widely related to many cancers as long as these alterations may impair its capacity to induce cell cycle arrest, DNA repair mechanisms, and apoptosis. Although TP53 alterations have been studied in astrocytic tumors, there is a lack of analysis considering specific TP53 mutations and their associations with p53 immunostainning, polymorphisms and their significance among the histological grades. Thus, we analyzed TP53 alterations in exons 2-11, including the codon 72 polymorphism, using DNA sequencing in 96 astrocytic gliomas (18 grade I, 20 grade II, 14 grade III, and 44 grade IV). Also, immunohistochemistry was assessed to evaluate the p53 protein expression. In this study, we found that the higher histological grades were statistically associated with TP53 mutations. Some of these mutations, such as TP53 P98T and TP53 G244S, seemed to be a specific marker for the higher grades, and the TP53 E286K mutation appears to be a World Health Organization grade III-IV progression marker. Also, the TP53 P98T mutation, in exon 4, is very likely to be important on the stabilization of the p53 protein, leading to its immunopositivity and it is potentially associated with the TP53 72Pro/Pro genotype.

PDGF and PDGF receptors in glioma

The family of platelet-derived growth factors (PDGFs) plays a number of critical roles in normal embryonic development, cellular differentiation, and response to tissue damage. Not surprisingly, as it is a multi-faceted regulatory system, numerous pathological conditions are associated with aberrant activity of the PDGFs and their receptors. As we and others have shown, human gliomas, especially glioblastoma, express all PDGF ligands and both the two cell surface receptors, PDGFR-α and -β. The cellular distribution of these proteins in tumors indicates that glial tumor cells are stimulated via PDGF/PDGFR-α autocrine and paracrine loops, while tumor vessels are stimulated via the PDGFR-β. Here we summarize the initial discoveries on the role of PDGF and PDGF receptors in gliomas and provide a brief overview of what is known in this field.