Analysis of loss of heterozygosity on chromosome 10 in patients with malignant astrocytic tumors: correlation with patient age and survival

Pleomorphic xanthoastrocytoma: a brief review

Pleomorphic xanthoastrocytoma (PXA) is a rare primary CNS tumor. Recent advances in the molecular characterization are helping to define subtypes of tumor. The discovery of BRAF mutations within a substantial percentage of PXA fosters a clearer understanding of the pathophysiology of these tumors with clear prognostic and therapeutic implications. These findings are expected to provide insight into the spectrum of clinical behavior observed in PXA, ranging from cure with surgery to diffuse dissemination throughout the neuraxis. This review details the clinical presentation including radiographic appearance of PXA. Pathology, including molecular pathology is discussed. Therapeutic management including surgical resection, radiotherapy and systemic therapies are reviewed.

The protective role of DMBT1 in cervical squamous cell carcinoma

To explore the possible influence of deleted in malignant brain tumor 1 (DMBT1) in cervical squamous cell carcinoma (CSCC). DMBT1 expression was detected by Real-time reverse transcription PCR (qRT-PCR) and immunohistochemistry in CSCC and adjacent normal tissues from 167 CSCC patients, and its relationship with clinicopathological features and prognosis was analyzed. Besides, the in vitro experiments, including MTT, Cell-Light EdU, Wound-healing, Transwell invasion, Annexin V-FITC/PI staining, qRT-PCR, and Western blot, were performed in SiHa and CaSKi cells, which were both divided into Blank, Vector, and DMBT1 groups. The mRNA level and the positive expression rate of DMBT1 in CSCC tissues were lower than the adjacent normal tissues. Moreover, DMBT1 positive rate was linked to FIGO stage, tumor diameter, lymph node metastasis, and tumor differentiation of CSCC. Besides, patients with positive DMBT1 expression had higher 5-year survival rate than those negative ones. According to the in vitro experiments, SiHa and CaSKi cells with overexpressed DMBT1 showed the inhibition of proliferative ability and the enhancement of apoptosis with the upregulated pro-apoptosis proteins (Bax and Cleaved caspase-3) and down-regulated anti-apoptosis protein Bcl-2. Moreover, compared with Blank group, DMBT1 group presented decrease in the migration and invasion of SiHa and CaSKi cells with the down-expression of interstitial markers (N-cadherin and Vimentin) and the up-expression of epithelial marker E-cadherin. DMBT1 was decreased in CSCC, whereas its overexpression can not only inhibit the proliferation, migration, and invasion, but induce the apoptosis of human CSCC cells, being a novel strategy for CSCC treatment.

Loss of heterozygosity and uniparental disomy of chromosome region 10q23.3-26.3 in glioblastoma

Glioblastoma is the most frequent and aggressive brain tumor in the adult population. Loss of heterozygosity (LOH) at markers of the long arm of chromosome 10 is the most common genetic alteration in glioblastoma, being detectable in up to 80% of cases. We have tested 124 glioblastoma samples for LOH by microsatellite analysis of the 10q23.3-26.3 region which contains the cancer related genes PTEN, FGFR2, MKI67, and MGMT. Then, a real-time quantitative microsatellite analysis (QuMA) was used to qualitatively estimate the change in copy number of this region in the samples with LOH. LOH was detected in 62.1% of the glioblastoma samples. A total of 64 samples with LOH in this region were examined by QuMA. LOH was attributed to a deletion in 37.5% of cases, and uniparental disomy (UPD) in 25% of cases. In 37.5% of cases, deletion and UPD segments alternated within the region: deletions being more frequent than UPD in its proximal part (encompassing PTEN and FGFR2) and both deletions and UPD occurring at the same frequency in its distal part (MGMT). Thus, we have investigated mechanisms of structural alterations of the chromosome region 10q23.3-26.3 in glioblastoma. In addition to a structural deletion of this region, UPD was identified as a frequent cause of LOH. We resume that more detailed studies of glioblastoma at the molecular genetic level are essential in search for potential markers suitable for predicting the disease outcome and the response to treatment.

Importance of biomarkers in glioblastomas patients receiving local BCNU wafer chemotherapy

Background

To assess the influence of molecular markers with potential prognostic value to groups of patients with newly diagnosed glioblastoma patients were examined: group A with 36 patients (surgical resection plus standard combined chemoradiotherapy) and group B with 36 patients (surgical resection, standard combined chemoradiotherapy plus carmustine wafer implantation).

Our aim was to determine chromosomal alterations, methylation status of MGMT, p15, and p16 (CDKN2A) in order to analyse the influence on patient survival time as well as radio- and chemotherapy responses. Promoter hypermethylation of MGMT, p16, and p15 genes were determined by MS-PCR. Comparative genomic hybridisation (CGH) analyses were performed with isolated, labelled DNA of each tumor to detect genetic alterations.

Results

Age of onset of the disease showed a significant effect on overall survival (OS) (p < 0.0001). Additional treatment with carmustine wafer (group B) compared to the control group (group A) did not result in improved OS (p = 0.562). Patients with a methylated MGMT promotor showed a significant longer OS compared to those patients with unmethylated MGMT promotor (p = 0.041). Subgroup analyses revealed that patients with methylated p15 showed a significant shorter OS when administered to group B rather than in group A (p = 0.0332). In patients additionally treated with carmustine wafer an amplification of 4q12 showed a significant impact on a reduced OS (p = 0.00835). In group B, a loss of 13q was significantly associated with a longer OS (p = 0.0364). If a loss of chromosome 10 occurred, patients in group B showed a significantly longer OS (p = 0.0123).

Conclusion

A clinical benefit for the widespread use of additional carmustine wafer implantation could not be found. However, carmustine wafer implantation shows a significantly improved overall survival if parts of chromosome 10 or chromosome 13 are deleted. In cases of 4q12 amplification and in cases of a methylated p15 promotor, the use of carmustine wafers is especially not recommended.

The MGMT promoter methylation is a strong prognostic Biomarker for benefit from temozolomide and BCNU chemotherapy.

Temozolomide low-dose chemotherapy in newly diagnosed low-grade gliomas: activity, safety, and long-term follow-up

PURPOSE

To explore the efficacy and toxicity of an extended schedule of temozolomide (50 mg/mq 1 week on/1 week off) in a population of newly diagnosed low-grade gliomas (LGG).

METHODS

Primary endpoints were progression-free survival (PFS) at 12 and 24 months and response rate evaluated with Response Assessment in Neuro-Oncology Criteria. Secondary endpoints were clinical benefit (reduction of seizures frequency), reduction of steroid, and modifications of Karnofsky Performance Status.

RESULTS

From 2006 to 2009, we enrolled 14 consecutive patients with newly diagnosed LGG: 8 grade II astrocytomas, 2 oligodendroglioma, and 4 oligo-astrocytoma. Temozolomide was administered for 18 cycles (mean) per patient (range 3-24 cycles). In 57.5% (n = 8), we observed stable disease, 28.5% (n = 4) presented a minor response, and 14% (n = 2) showed progression. Five patients presented early progression during the first year of treatment and the study was stopped. A relevant clinical benefit was observed in 85% of patients (seizure control). After 6 years of follow-up, only 4 patients died. Prolonged PFS was associated with 1p-19q codeletion over 1p-19q intact (35 vs 4 months; p<0.04) and IDH1 mutation over IDH1 wild-type (36 vs 6 months; p<0.009).

CONCLUSIONS

The study was interrupted for the high rate of progression observed in the first 14 patients enrolled. However, our results show that an extended low dose of temozolomide presents interesting activity with objective response and clinical benefit, but does not seem to prevent progression in patients presenting unfavorable molecular prognostic factors.

The MGMT promoter SNP rs16906252 is a risk factor for MGMT methylation in glioblastoma and is predictive of response to temozolomide

BACKGROUND

Promoter methylation of O(6)-methylguanine-DNA methyltransferase (MGMT) is an important predictive biomarker in glioblastoma. The T variant of the MGMT promoter-enhancer single nucleotide polymorphism (SNP; rs16906252) has been associated with the presence of MGMT promoter methylation in other cancers. We examined the association of the T allele of rs16906252 with glioblastoma development, tumor MGMT methylation, MGMT protein expression, and survival outcomes.

METHODS

Two independent temozolomide-treated glioblastoma cohorts-one Australian (Australian Genomics and Clinical Outcomes of Glioma, n = 163) and the other American (University of California Los Angeles/Kaiser Permanente Los Angeles, n = 159)-were studied. Allelic bisulphite sequencing was used to determine if methylation was specific to the T allele. Additionally, we compared the incidence of the T allele between glioblastoma cases and matched controls to assess whether it was a risk factor for developing MGMT methylated glioblastoma.

RESULTS

Carriage of the T allele of the rs16906252 SNP was associated with both MGMT methylation and low MGMT protein expression and predicted significantly longer survival in temozolomide-treated patients with both MGMT methylated and nonmethylated glioblastoma. Methylation was linked to the T allele, inferring that the T variant plays a key role in the acquisition of MGMT methylation. Carriage of the T allele was associated with a significantly elevated risk of developing glioblastoma (adjusted odds ratio, 1.96; P = .013), increasing further when glioblastoma was classified by the presence of MGMT methylation (adjusted odds ratio, 2.86; P = .001).

CONCLUSIONS

The T allele of the rs16906252 SNP is a key determinant in the acquisition of MGMT methylation in glioblastoma. Temozolomide-treated patients with the rs16906252 T genotype have better survival, irrespective of tumor methylation status.

Biomarkers for glioma immunotherapy: the next generation

The term "biomarker" historically refers to a single parameter, such as the expression level of a gene or a radiographic pattern, used to indicate a broader biological state. Molecular indicators have been applied to several aspects of cancer therapy: to describe the genotypic and phenotypic state of neoplastic tissue for prognosis, to predict susceptibility to anti-proliferative agents, to validate the presence of specific drug targets, and to evaluate responsiveness to therapy. For glioblastoma (GBM), immunohistochemical and radiographic biomarkers accessible to the clinical lab have informed traditional regimens, but while immunotherapies have emerged as potentially disruptive weapons against this diffusely infiltrating, heterogeneous tumor, biomarkers with strong predictive power have not been fully established. The cancer immunotherapy field, through the recently accelerated expansion of trials, is currently leveraging this wealth of clinical and biological data to define and revise the use of biomarkers for improving prognostic accuracy, personalization of therapy, and evaluation of responses across the wide variety of tumors. Technological advancements in DNA sequencing, cytometry, and microscopy have facilitated the exploration of more integrated, high-dimensional profiling of the disease system-incorporating both immune and tumor parameters-rather than single metrics, as biomarkers for therapeutic sensitivity. Here we discuss the utility of traditional GBM biomarkers in immunotherapy and how the impending transformation of the biomarker paradigm-from single markers to integrated profiles-may offer the key to bringing predictive, personalized immunotherapy to GBM patients.

Treatment of glioblastoma in elderly patients

Although glioblastoma occurs mostly in elderly patients, there is a paucity of trials addressing patients older than 70 years of age. Age, by itself, constitutes an unfavorable prognostic factor, which is probably due to unpropitious genetic features, but also due to iatrogenic defeatism. However, many retrospective studies report a survival benefit achieved by aggressive surgical resection seeking gross total removal of contrast-enhancing tumor according to preoperative MRI. Combined radiochemotherapy with concomitant and adjuvant temozolomide has not been investigated in prospective trials. Numerous retrospective studies and a meta-analysis suggest benefit from combined treatment. Prospective randomized trials only evaluated either temozolomide or radiotherapy. Single-treatment hypofractionated radiotherapy performed superior to conventional fractionation. In patients with methylated MGMT promoter, first-line dose-dense temozolomide facilitates prolonged survival. However, there is no comparison with combined radiochemotherapy as the standard-of-care in adult patients. Comorbidity is more frequent in elderly patients, but does not correlate with preterm termination of temozolomide treatment. This review article compiles data proposing a straightforward glioblastoma treatment, irrespective of age.

Cancer stem cells from a rare form of glioblastoma multiforme involving the neurogenic ventricular wall

Background

The cancer stem cell (CSC) hypothesis posits that deregulated neural stem cells (NSCs) form the basis of brain tumors such as glioblastoma multiforme (GBM). GBM, however, usually forms in the cerebral white matter while normal NSCs reside in subventricular and hippocampal regions. We attempted to characterize CSCs from a rare form of glioblastoma multiforme involving the neurogenic ventricular wall.

Methods

We described isolating CSCs from a GBM involving the lateral ventricles and characterized these cells with in vitro molecular biomarker profiling, cellular behavior, ex vivo and in vivo techniques.

Results

The patient’s MRI revealed a heterogeneous mass with associated edema, involving the left subventricular zone. Histological examination of the tumor established it as being a high-grade glial neoplasm, characterized by polygonal and fusiform cells with marked nuclear atypia, amphophilic cytoplasm, prominent nucleoli, frequent mitotic figures, irregular zones of necrosis and vascular hyperplasia. Recurrence of the tumor occurred shortly after the surgical resection. CD133-positive cells, isolated from the tumor, expressed stem cell markers including nestin, CD133, Ki67, Sox2, EFNB1, EFNB2, EFNB3, Cav-1, Musashi, Nucleostemin, Notch 2, Notch 4, and Pax6. Biomarkers expressed in differentiated cells included Cathepsin L, Cathepsin B, Mucin18, Mucin24, c-Myc, NSE, and TIMP1. Expression of unique cancer-related transcripts in these CD133-positive cells, such as caveolin-1 and −2, do not appear to have been previously reported in the literature. Ex vivo organotypic brain slice co-culture showed that the CD133+ cells behaved like tumor cells. The CD133-positive cells also induced tumor formation when they were stereotactically transplanted into the brains of the immune-deficient NOD/SCID mice.

Conclusions

This brain tumor involving the neurogenic lateral ventricular wall was comprised of tumor-forming, CD133-positive cancer stem cells, which are likely the driving force for the rapid recurrence of the tumor in the patient.

The hypermethylation of the O6-methylguanine-DNA methyltransferase gene promoter in gliomas--correlation with array comparative genome hybridization results and IDH1 mutation

The use of molecular markers in the diagnostics of gliomas aids histopathological diagnosis and allows their further classification into clinically significant subgroups. The aim of this study was to characterize the methylation pattern of the O(6) -methylguanine-DNA methyltransferase (MGMT) promoter, gene copy number aberrations, and isocitrate dehydrogenase I (IDH1) mutation in gliomas. We studied 51 gliomas (15 oligodendrogliomas, 18 oligoastrocytomas, 3 astrocytomas, and 15 glioblastomas) by pyrosequencing, array comparative genome hybridization (CGH), and immunohistochemistry. MGMT hypermethylation was observed in 100% of oligoastrocytomas, 93% of oligodendrogliomas, and 47% of glioblastomas. The most frequently altered chromosomal regions were deletions of 1p31.1/21.1-22.2 and 19q13.3qter in oligodendroglial tumors, and losses of 9p21.3, 10q25.3qter, and 10q26.13-26.2 in glioblastomas. Deletions on 9p and 10q, and gain of 7p were associated with the unmethylated MGMT phenotype, whereas deletion of 19q and oligodendroglial morphology was associated with MGMT hypermethylation. IDH1 mutation showed positive correlation with MGMT hypermethylation and loss of 1p/19q. Our results suggest that MGMT promoter methylation, analyzed by pyrosequencing, is a frequent event in oligodendroglial tumors, and it correlates with IDH1 mutation and 19q loss in gliomas. Pyrosequencing proved a good method for assessing the degree of MGMT methylation in formalin-fixed paraffin-embedded glioma samples. However, further studies are needed to confirm a clinically relevant cut-off point for MGMT methylation in gliomas.

LOH on 10p14-p15 targets the PFKFB3 gene locus in human glioblastomas

Loss of heterozygosity (LOH) on chromosome arm 10p is very common in high-grade gliomas and is, among others, concentrated on the region 10p14-p15. Presence of multiple tumor suppressor genes is assumed, but until now only Krüpple-like transcription factor 6 (KLF6) has been suggested as possible target of LOH in this region. On the basis of the fact that the splice variant 4 (UBI2K4) of the PFKFB3 gene, located in 10p15.1, inhibits the anchorage-independent growth of U87 glioblastoma cells, we hypothesized that PFKFB3 is a target gene of LOH in glioblastomas. In this study, we analyzed 40 glioblastomas for LOH in 10p15, including the PFKFB3 and KLF6 loci, by PCR-based microsatellite analysis. We detected LOH of PFKFB3 in 55% (22/40) of glioblastomas. LOH of KLF6, mapped 2.5 cM telomerically to the PFKFB3 locus, was not stringently correlated to the PFKFB3 LOH. The allelic deletion of PFKFB3 resulted in a decrease of PFKFB3 mRNA level accompanied by a lower PFKFB3 protein level. The expression of growth-inhibiting splice variant UBI2K4 was effectively reduced in glioblastomas with PFKFB3 LOH and a positive correlation with overall PFKFFB3 expression was observed. The PFKFB3 LOH as well as the resulting low UBI2K4 expression level was associated with a poor prognosis of glioblastoma patients. We conclude that LOH on 10p14-p15 in glioblastomas targets PFKFB3 and in particular splice variant UBI2K4, a putative tumor suppressor protein in glioblastomas.

Detailed characterization of alterations of chromosomes 7, 9, and 10 in glioblastomas as assessed by single-nucleotide polymorphism arrays

Glioblastomas are cytogenetically heterogeneous tumors that frequently display alterations of chromosomes 7, 9p, and 10q. We used high-density (500K) single-nucleotide polymorphism arrays to investigate genome-wide copy number alterations and loss of heterozygosity in 35 primary glioblastomas. We focused on the identification and detailed characterization of alterations involving the most frequently altered chromosomes (chromosomes 7, 9, and 10), the identification of distinct prognostic subgroups of glioblastomas based on the cytogenetic patterns of alteration for these chromosomes, and validation of their prognostic impact in a larger series of tumors from public databases. Gains of chromosome 7 (97%), with or without epidermal growth factor receptor (EGFR) amplification, and losses of chromosomes 9p (83%) and 10 (91%) were the most frequent alterations. Such alterations defined five different cytogenetic groups with a significant effect on patient survival; notably, EGFR amplification (29%) was associated with a better survival among older patients, as confirmed by multivariate analysis of a larger series of glioblastomas from the literature. In addition, our results provide further evidence about the relevance of other genes (eg, EGFR, CDKN2A/B, MTAP) in the pathogenesis of glioblastomas. Altogether, our results confirm the cytogenetic heterogeneity of glioblastomas and suggest that their stratification based on combined assessment of cytogenetic alterations involving chromosomes 7, 9, and 10 may contribute to the prognostic evaluation of glioblastomas.

Homozygous 10q23/PTEN deletion and its impact on outcome in glioblastoma: a prospective translational study on a uniformly treated cohort of adult patients

Tumors from a prospective cohort of adult patients with newly diagnosed glioblastoma (n=73), treated uniformly with radiochemotherapy, were examined for 10q23/PTEN deletion by fluorescence in situ hybridization (FISH). Statistical methods were employed to evaluate the degree of association between 10q23/PTEN deletion status and patient age. Survival analysis was performed using Kaplan-Meier log-rank test and multivariable Cox models to assess the prognostic value of 10q23/PTEN deletion. Interestingly, 10q23/PTEN homozygous deletion was frequent in patients >45 years of age (P=0.034) and the median age of patients harboring PTEN homozygous deletions was significantly higher than those with the retained status (P=0.019). 10q23/PTEN homozygous deletion was associated with shorter survival in the entire cohort as well in patients >45 years (P<0.05), indicating that loss of 10q23/PTEN showed clinical importance in elderly patients. Our study highlights the independent prognostic/predictive value of 10q23/PTEN deletion status as identified by FISH, particularly in glioblastoma patients aged >45 years.

Molecular pathogenesis of malignant glial tumors

Malignant glial tumors are the most aggressive and difficult to treat neoplasms arising in the brain. More than 22,000 people in the United States are diagnosed with a malignant glioma annually, and most will die within the first two years from diagnosis. Traditionally, gliomas have been categorized based solely on tumor histological features. However, expression studies have found that molecular signatures can be used to categorize these tumors into subclasses that more effectively predict patient outcome. The heterogeneity between tumors as well as within individual tumors makes understanding the molecular aspects of tumorigenesis extremely important. Several genetically engineered mouse models (GEMMs) of glioma have been developed that recapitulate the molecular alterations observed in the human disease. GEMMs of glioma have allowed researchers to more closely study the role of cancer stem cells (CSC) in gliomagenesis as well as the relevance of signaling within the CSC microenvironment. Knowledge of the underlying molecular signatures of malignant glial tumors coupled with the existence of a variety of human disease-relevant GEMMs of this tumor type provide researchers and clinicians with valuable resources for the discovery of new drug targets.

Decreased expression of germinal center-associated nuclear protein is involved in chromosomal instability in malignant gliomas

Malignant glioma (MG) is highly proliferative and invasive, with the malignant characteristics associated with aneuploidy and chromosomal instability (CIN). Here, we found that the level of germinal center-associated nuclear protein (GANP), a mammalian homologue of yeast Sac3, was markedly decreased in MGs with a poor prognosis; and thus we explored the effect of its decrease on cell-cycle progression of MG cell lines. Glioblastomas showed a significantly lower level of ganp mRNA than anaplastic astrocytomas, as measured by real-time reverse transcription-PCR, in 101 cases of adult MG. MGs of ganp(Low) expression displayed more malignant characteristics, with loss of heterozygosity on chromosome 10, epidermal growth factor receptor gene amplification, and significantly poorer prognosis than the ganp(High) group. Human diploid fibroblasts depleted of ganp mRNA by the RNA interference (RNAi) method showed a decreased percentage of S-phase cells and a cellular-senescence phenotype. MG cell lines harboring abnormalities of various cell-cycle checkpoint molecules displayed slippage of mitotic checkpoints and an increased proportion of hyperploid cells after ganp RNAi-treatment. These results suggest that GANP protects cells from cellular senescence caused by DNA damage and that a significant decrease in GANP expression leads to malignancy by generating hyperploidy and CIN.

PTEN in brain tumors

The tumor suppressor PTEN dephosphorylates phospholipids generated through the activity of PI3K. PTEN thus antagonizes PI3K activity and regulates a multitude of cellular processes such as angiogenesis, motility, invasiveness, survival and proliferation, all of which can initiate and sustain the malignant phenotype. Although PTEN's lipid phosphatase activity is key to its tumor suppressive functions, it also dephosphorylates protein substrates and interacts with other key regulatory molecules, salient among them the tumor suppressor p53. Given the critical roles of PTEN in cellular homeostasis, it is not surprising that both PTEN expression levels and PTEN protein activities are tightly controlled by a complex conglomeration of molecules that regulate post-translational modifications, subcellular localization, transcriptional activation and transcriptional repression. As one of the most commonly altered molecules in human disease, PTEN plays an important role in a myriad of signaling cascades, and plays a central role in normal brain development and brain tumor pathogenesis. As such it influences prognosis of human cancer, predicts response to therapy, constitutes the lynchpin of genetic syndromes, and may underlie neurocognitive abnormalities such as autism spectrum disorders and Alzheimer's disease. Thus, targeting PTEN and its signaling affiliates sows the seeds for combating not only cancer but also neurocognitive disorders.

Differential radiosensitizing potential of temozolomide in MGMT promoter methylated glioblastoma multiforme cell lines

PURPOSE

To investigate the radiosensitizing potential of temozolomide (TMZ) for human glioblastoma multiforme (GBM) cell lines using single-dose and fractionated gamma-irradiation.

METHODS AND MATERIALS

Three genetically characterized human GBM cell lines (AMC-3046, VU-109, and VU-122) were exposed to various single (0-6 Gy) and daily fractionated doses (2 Gy per fraction) of gamma-irradiation. Repeated TMZ doses were given before and concurrent with irradiation treatment. Immediately plated clonogenic cell-survival curves were determined for both the single-dose and the fractionated irradiation experiments. To establish the net effect of clonogenic cell survival and cell proliferation, growth curves were determined, expressed as the number of surviving cells.

RESULTS

All three cell lines showed MGMT promoter methylation, lacked MGMT protein expression, and were sensitive to TMZ. The isotoxic TMZ concentrations used were in a clinically feasible range of 10 micromol/L (AMC-3046), 3 micromol/L (VU-109), and 2.5 micromol/L (VU-122). Temozolomide was able to radiosensitize two cell lines (AMC 3046 and VU-122) using single-dose irradiation. A reduction in the number of surviving cells after treatment with the combination of TMZ and fractionated irradiation was seen in all three cell lines, but only AMC 3046 showed a radiosensitizing effect.

CONCLUSIONS

This study on TMZ-sensitive GBM cell lines shows that TMZ can act as a radiosensitizer and is at least additive to gamma-irradiation. Enhancement of the radiation response by TMZ seems to be independent of the epigenetically silenced MGMT gene.

Malignant glioma progression and nitric oxide

Glioblastoma multiforme, the most common of the malignant gliomas, carries a dismal prognosis in spite of the most aggressive therapy and recent advances in molecular pathways of glioma progression. Although it has received relatively little attention in the setting of malignant gliomas, nitric oxide metabolism may be intimately associated with the disease process. Interestingly, nitric oxide has both physiological roles (e.g., neurotransmitter-like activity, stimulation of cyclic GMP), and pathophysiological roles (e.g., neoplastic transformation, tumor neovascularization, induction of apoptosis, free radical damage). Moreover, whether nitric oxide is neuroprotective or neurotoxic in a given disease state, or whether it enhances or diminishes chemotherapeutic efficacy in malignant neoplasia, is unresolved. This review discusses the multifaceted activity of nitric oxide with particular reference to malignant gliomas.

High-grade glioma formation results from postnatal pten loss or mutant epidermal growth factor receptor expression in a transgenic mouse glioma model

High-grade gliomas are devastating brain tumors associated with a mean survival of <50 weeks. Two of the most common genetic changes observed in these tumors are overexpression/mutation of the epidermal growth factor receptor (EGFR) vIII and loss of PTEN/MMAC1 expression. To determine whether somatically acquired EGFRvIII expression or Pten loss accelerates high-grade glioma development, we used a previously characterized RasB8 glioma-prone mouse strain, in which these specific genetic changes were focally introduced at 4 weeks of age. We show that both postnatal EGFRvIII expression and Pten inactivation in RasB8 mice potentiate high-grade glioma development. Moreover, we observe a concordant loss of Pten and EGFR overexpression in nearly all high-grade gliomas induced by either EGFRvIII introduction or Pten inactivation. This novel preclinical model of high-grade glioma will be useful in evaluating brain tumor therapies targeted to the pathways specifically dysregulated by EGFR expression or Pten loss.

Delivery systems and molecular targets of mechanism-based therapies for GBM

Glioblastoma multiforme (GBM) is the most common malignant brain tumor of adults and is in great need of novel diagnostic and therapeutic approaches. Diagnosis is beginning to consider a tumor's genetic status and in the future may incorporate gene expression or proteomic profiles. Genetic alterations in gliomas that are being used in classification include TP53 and retinoblastoma pathway disruption, PTEN mutations, epidermal growth factor receptor amplification and 1p/19q losses. Molecular mechanisms are being exploited to treat glioblastoma multiforme. Tyrosine kinase inhibitors directed at epidermal growth factor receptor (ZD1839, OSI-774) are being explored. Farnesyltransferase inhibitors (R115777) block activation of the ras pathway and may be effective. Antagonists of the endothelin receptor (e.g., atrasentan) expressed on blood vessels may block the high degree of angiogenesis in gliomas. Tumors lacking methylthioadenosine phosphorylase are sensitive to inhibitors of de novo adenosine synthesis (SDX-102) since they lack a salvage pathway. Future goals are to tailor therapies to a tumor's molecular, proteomic or genomic status ,and manage glioblastoma multiformes as in chronic diseases in a multidisciplinary clinical setting.

Molecular subclasses of high-grade glioma predict prognosis, delineate a pattern of disease progression, and resemble stages in neurogenesis

Previously undescribed prognostic subclasses of high-grade astrocytoma are identified and discovered to resemble stages in neurogenesis. One tumor class displaying neuronal lineage markers shows longer survival, while two tumor classes enriched for neural stem cell markers display equally short survival. Poor prognosis subclasses exhibit markers either of proliferation or of angiogenesis and mesenchyme. Upon recurrence, tumors frequently shift toward the mesenchymal subclass. Chromosomal locations of genes distinguishing tumor subclass parallel DNA copy number differences between subclasses. Functional relevance of tumor subtype molecular signatures is suggested by the ability of cell line signatures to predict neurosphere growth. A robust two-gene prognostic model utilizing PTEN and DLL3 expression suggests that Akt and Notch signaling are hallmarks of poor prognosis versus better prognosis gliomas, respectively.

Patients with high-grade gliomas harboring deletions of chromosomes 9p and 10q benefit from temozolomide treatment

Surgical cure of glioblastomas is virtually impossible and their clinical course is mainly determined by the biologic behavior of the tumor cells and their response to radiation and chemotherapy. We investigated whether response to temozolomide (TMZ) chemotherapy differs in subsets of malignant glioblastomas defined by genetic lesions. Eighty patients with newly diagnosed glioblastoma were analyzed with comparative genomic hybridization and loss of heterozygosity. All patients underwent radical resection. Fifty patients received TMZ after radiotherapy (TMZ group) and 30 patients received radiotherapy alone (RT group). The most common aberrations detected were gains of parts of chromosome 7 and losses of 10q, 9p, or 13q. The spectrum of genetic aberrations did not differ between the TMZ and RT groups. Patients treated with TMZ showed significantly better survival than patients treated with radiotherapy alone (19.5 vs 9.3 months). Genomic deletions on chromosomes 9 and 10 are typical for glioblastoma and associated with poor prognosis. However, patients with these aberrations benefited significantly from TMZ in univariate analysis. In multivariate analysis, this effect was pronounced for 9p deletion and for elderly patients with 10q deletions, respectively. This study demonstrates that molecular genetic and cytogenetic analyses potentially predict responses to chemotherapy in patients with newly diagnosed glioblastomas.

Molecular genetics of oligodendrogliomas: a model for improved clinical management in the field of neurooncology

Over the last several years, oligodendroglial tumors have become a model for the positive role of molecular genetics in improved treatment of patients with brain tumors. Oligodendrogliomas, in contrast to astrocytic gliomas, frequently respond to chemotherapy and have a better overall prognosis. Combined loss of chromosomes 1p and 19q has proven to be a powerful predictor of chemotherapeutic response and survival in oligodendrogliomas. In contrast, other genetic alterations, such as TP53 and PTEN mutations, EGFR amplification, and homozygous deletion of CDKN2A have been correlated with worse outcome in these tumors. Furthermore, 1p/19q loss has been shown to correlate with unequivocal oligodendroglial tumor histology, location and growth pattern of tumors within the brain, and magnetic resonance imaging characteristics. Although much is also known about the molecular pathological characteristics of astrocytic gliomas, the significance of this information to clinical management in patients with these tumors has not been as striking as has been the case for oligodendrogliomas; possible reasons for this are discussed. In this paper the author will summarize these advances, thus attempting to highlight the molecular genetic study of oligodendrogliomas as a model for improved clinical management in the field of neurooncology.

Population-Based Studies on Incidence, Survival Rates, and Genetic Alterations in Astrocytic and Oligodendroglial Gliomas

Published data on prognostic and predictive factors in patients with gliomas are largely based on clinical trials and hospital-based studies. This review summarizes data on incidence rates, survival, and genetic alterations from population-based studies of astrocytic and oligodendrogliomas that were carried out in the Canton of Zurich, Switzerland (approximately 1.16 million inhabitants). A total of 987 cases were diagnosed between 1980 and 1994 and patients were followed up at least until 1999. While survival rates for pilocytic astrocytomas were excellent (96% at 10 years), the prognosis of diffusely infiltrating gliomas was poorer, with median survival times (MST) of 5.6 years for low-grade astrocytoma WHO grade II, 1.6 years for anaplastic astrocytoma grade III, and 0.4 years for glioblastoma. For oligodendrogliomas the MSTwas 11.6 years for grade II and 3.5 years for grade III. TP53 mutations were most frequent in gemistocytic astrocytomas (88%), followed by fibrillary astrocytomas (53%) and oligoastrocytomas (44%), but infrequent (13%) in oligodendrogliomas. LOH 1p/19q typically occurred in tumors without TP53 mutations and were most frequent in oligodendrogliomas (69%), followed by oligoastrocytomas (45%), but were rare in fibrillary astrocytomas (7%) and absent in gemistocytic astrocytomas. Glioblastomas were most frequent (3.55 cases per 100,000 persons per year) adjusted to the European Standard Population, amounting to 69% of total incident cases. Observed survival rates were 42.4% at 6 months, 17.7% at one year, and 3.3% at 2 years. For all age groups, survival was inversely correlated with age, ranging from an MST of 8.8 months (<50 years) to 1.6 months (>80 years). In glioblastomas, LOH 10q was the most frequent genetic alteration (69%), followed by EGFR amplification (34%), TP53 mutations (31%), p16INK4a deletion (31%), and PTEN mutations (24%). LOH 10q occurred in association with any of the other genetic alterations, and was the only alteration associated with shorter survival of glioblastoma patients. Primary (de novo) glioblastomas prevailed (95%), while secondary glioblastomas that progressed from low-grade or anaplastic gliomas were rare (5%). Secondary glioblastomas were characterized by frequent LOH 10q (63%) and TP53 mutations (65%). Of the TP53 mutations in secondary glioblastomas, 57% were in hot-spot codons 248 and 273, while in primary glioblastomas, mutations were more evenly distributed. G:C-->A:T mutations at CpG sites were more frequent in secondary than primary glioblastomas, suggesting that the acquisition of TP53 mutations in these glioblastoma subtypes may occur through different mechanisms.

Genetic pathways to glioblastomas

Glioblastomas, the most frequent and malignant human brain tumors, may develop de novo (primary glioblastoma) or by progression from low-grade or anaplastic astrocytoma (secondary glioblastoma). These glioblastoma subtypes constitute distinct disease entities that affect patients of different ages and develop through different genetic pathways. Our recent population-based study in the Canton of Zürich, Switzerland, shows that primary glioblastomas develop in older patients (mean age, 62 years) and typically show LOH on chromosome 10q (69%) and other genetic alterations (EGFR amplification, TP53 mutations, p16INK4a deletion, and PTEN mutations) at frequencies of 24-34%. Secondary glioblastomas develop in younger patients (mean, 45 years) and frequently show TP53 mutations (65%) and LOH 10q (63%). Common to both primary and secondary glioblastoma is LOH on 10q, distal to the PTEN locus; a putative suppressor gene at 10q25-qter may be responsible for the glioblastoma phenotype. Of the TP53 point mutations in secondary glioblastomas, 57% were located in hotspot codons 248 and 273, while in primary glioblastomas, mutations were more widely distributed. Furthermore, G:C-->A:T mutations at CpG sites were more frequent in secondary than in primary glioblastomas (56% vs 30%). These data suggest that the TP53 mutations in these glioblastoma subtypes arise through different mechanisms. There is evidence that G:C-->A:T transition mutations at CpG sites in the TP53 gene are significantly more frequent in low-grade astrocytomas with promoter methylation of the O6-methylguanine-DNA methyltransferase (MGMT) gene than in those without methylation. This suggests that, in addition to deamination of 5-methylcytosine (the best known mechanism of formation of G:C-->A:T transitions at CpG sites), involvement of alkylating agents that produce O6-methylguanine or related adducts recognized by MGMT cannot be excluded in the pathway leading to secondary glioblastomas.

Genetic Pathways to Glioblastoma

We conducted a population-based study on glioblastomas in the Canton of Zurich, Switzerland (population, 1.16 million) to determine the frequency of major genetic alterations and their effect on patient survival. Between 1980 and 1994, 715 glioblastomas were diagnosed. The incidence rate per 100,000 population/year, adjusted to the World Standard Population, was 3.32 in males and 2.24 in females. Observed survival rates were 42.4% at 6 months, 17.7% at 1 year, and 3.3% at 2 years. For all of the age groups, younger patients survived significantly longer, ranging from a median of 8.8 months (<50 years) to 1.6 months (>80 years). Loss of heterozygosity (LOH) 10q was the most frequent genetic alteration (69%), followed by EGFR amplification (34%), TP53 mutations (31%), p16(INK4a) deletion (31%), and PTEN mutations (24%). LOH 10q occurred in association with any of the other genetic alterations and was predictive of shorter survival. Primary (de novo) glioblastomas prevailed (95%), whereas secondary glioblastomas that progressed from low-grade or anaplastic gliomas were rare (5%). Secondary glioblastomas were characterized by frequent LOH 10q (63%) and TP53 mutations (65%). Of the TP53 mutations in secondary glioblastomas, 57% were in hotspot codons 248 and 273, whereas in primary glioblastomas, mutations were more equally distributed. G:C-->A:T mutations at CpG sites were more frequent in secondary than primary glioblastomas (56% versus 30%; P = 0.0208). This suggests that the acquisition of TP53 mutations in these glioblastoma subtypes occurs through different mechanisms.

Role of PTEN and MMP-7 expression in growth, invasion, metastasis and angiogenesis of gastric carcinoma

To investigate the role of PTEN and matrix metalloproteinase-7 (MMP-7) expression in tumorigenesis and progression of gastric carcinoma, their expression in 113 gastric carcinomas was studied by immunohistochemistry. Microvessel density (MVD) was counted using the anti-CD34 antibody. The expressions of PTEN and MMP-7, and MVD were compared with the clinicopathological parameters of tumors, and the relationship between PTEN and MMP-7 expression and MVD was analyzed. It was found that PTEN was expressed less frequently in primary gastric carcinoma cells than in adjacent epithelial cells (P < 0.05), whereas this was reversed for MMP-7 (P < 0.05). PTEN expression was negatively correlated with invasion, metastasis, growth pattern, Lauren's classification and histological classification (P < 0.05). Matrix metalloproteinase-7 expression was positively associated with tumor size, Borrmann's classification, invasive depth, metastasis and TNM staging (P < 0.05), but negative with PTEN expression (P < 0.05). A positive correlation of MVD with tumor size, invasive depth, metastasis and TNM staging was found (P < 0.05). Microvessel density depended on decreased PTEN expression and increased MMP-7 expression (P < 0.05). The results of the present study suggested that down-regulated PTEN expression and up-regulated MMP-7 expression were greatly implicated in tumorigenesis and progression of gastric carcinoma. Close correlation between PTEN on MMP-7 expression provided a novel insight into the regulatory effects of PTEN on MMP-7 expression in gastric carcinoma.

Analysis of 1p, 19q, 9p, and 10q as prognostic markers for high-grade astrocytomas using fluorescence in situ hybridization on tissue microarrays from Radiation Therapy Oncology Group trials

Survival periods vary considerably for patients with high-grade astrocytomas, and reliable prognostic markers are not currently available. We therefore investigated whether genetic losses from chromosomes 1p, 19q, 9p, or 10q were associated with survival in 89 high-grade astrocytomas using tissue microarrays (TMAs) derived from Radiation Therapy Oncology Group clinical trials. Cases included 15 anaplastic astrocytomas (AAs) and 74 glioblastomas (GBMs) selected on the basis of survival times significantly shorter or longer than the expected median. Genetic analysis was performed by TMA-fluorescence in situ hybridization (FISH) on array sections using 8 DNA probes, including those directed at 1p32, 19q13.4, 9p21 (p16/CDKN2A), and 10q (PTEN and DMBT1). Genetic status for each locus was correlated with patient survival group, and data were analyzed by using Fisher's exact test of association (adjusted P = 0.025). Losses of chromosome 1p, either alone or in combination with 19q, were encountered in only 2 cases, both AAs. This contrasts with oligodendrogliomas, in which combined 1p and 19q losses are frequent and predictive of prolonged survival. Solitary 19q loss was noted in 3/15 AAs and in 7/70 GBMs and was more frequent in the long-term survival group (P = 0.041, AA and GBM combined). Chromosome 9p loss was seen in 5/8 AAs and 39/57 GBMs, whereas chromosome 10q loss was detected in 4/15 AAs and 48/68 GBMs. The 9p and 10q deletions were slightly more frequent in short-term survivors, though none of the comparisons achieved statistical significance. Long-term and short-term survival groups of high-grade astrocytomas appear to have dissimilar frequencies of 19q, 9p, and 10q deletions. TMA-FISH is a rapid and efficient way of evaluating genetic alterations in such tumors.

Recent progress in predictive biomarkers for metastatic recurrence of human hepatocellular carcinoma: a review of the literature

Molecular markers (biomarkers) for hepatocellular carcinoma (HCC) metastasis and recurrence could provide additional information to that gained from traditional histopathological features. A large number of biomarkers have been shown to have potential predictive significance. One important aspect of this is to detect the transcripts of tumor-associated antigens (such as AFP, MAGEs, and CK19), which are proposed as predictive markers of HCC cells disseminated into the circulation and for metastatic recurrence. Another important aspect is to analyze the molecular markers for cellular malignancy phenotype, including DNA ploidy, cellular proliferation index, cell cycle regulators, oncogenes, and tumor suppressors (especially p53 gene), as well as telomerase activity. Molecular factors involved in the process of HCC invasion and metastasis, including adhesion molecules (E-cadherin, catenins, ICAM-1, laminin-5, CD44 variants, osteopontin), proteinases responsible for the degradation of extracellular matrix (MMPs, uPA system), as well as angiogenesis regulators (such as VEGF, intratumor MVD), have also been shown to be potential predictors for HCC metastatic recurrence and clinical outcomes. One important new trend is to widely delineate biomarkers with genomic and proteomic expression with reference to predicting metastatic recurrence, molecular diagnosis, and classification, which has been drawing more attention recently. Body fluid (particularly blood and urine) testing for biomarkers is easily accessible and more useful in clinical patients. The prognostic significance of circulating DNA in plasma or serum and its genetic alterations is another important direction. More attention should be paid to these areas in the future. As understanding of tumor biology deepens, more and more new biomarkers with high sensitivity and specificity for HCC metastatic recurrence could be found and routinely used in clinical assays. However, the combination of the pathological features and some of the biomarkers mentioned above seems to be more practical up to now.

Histological indicators of prognosis in glioblastomas: retinoblastoma protein expression and oligodendroglial differentiation indicate improved survival

AIM

To assess the potential prognostic significance of a range of molecular and morphological parameters in glioblastomas that can be applied in the setting of a routine diagnostic neuropathology laboratory.

METHODS AND RESULTS

A consecutive series of 107 adult glioblastomas were studied. Retinoblastoma and deleted-in-colon cancer (DCC) protein expression were assessed using immunocytochemistry and chromosome 10 loss by in-situ hybridization. Loss of retinoblastoma expression was associated with a worse outcome, which appeared to be independent of age. There was no significant association between chromosome 10 loss or DCC protein expression and survival. Survival was significantly increased in the 5% of patients whose tumours had focal morphological features suggesting oligodendroglial differentiation.

CONCLUSIONS

Glioblastomas containing areas of oligodendroglial differentiation or showing widespread immunocytochemical expression of retinoblastoma protein have a better prognosis than those without these features.

Temozolomide chemotherapy for progressive low-grade glioma: clinical benefits and radiological response

BACKGROUND

The optimal treatment for low-grade glioma (LGG) is still controversial. Recent data indicate a potential influence of chemotherapy on the natural evolution of these tumors, allowing for the deferral of more aggressive therapies.

PATIENTS AND METHODS

Forty-three patients affected with LGG (29 astrocytoma, four oligodendroglioma and 10 mixed oligo-astrocytoma) were treated with temozolomide (TMZ) at the time of documented clinical and radiological progression. McDonald's response criteria were utilized to evaluate TMZ activity. Thirty patients (69.7%) had previously received radiotherapy; 16 (37.2%) had received prior chemotherapy. Clinical benefit was evaluated measuring seizure control, reduction in steroid dose and modification of Karnofsky performance status and Barthel index. Quality of life was assessed with the QLQ-C30 questionnaire.

RESULTS

We observed a complete response in four patients, 16 partial responses, 17 stable disease (with four minor response) and six progressive disease. Median duration of response was 10 months [95% confidence interval (CI) 8-12], with a 76% rate of progression free survival (PFS) at 6 months, and a 39% rate of PFS at 12 months. A relevant clinical benefit was observed particularly in patients presenting epilepsy.

CONCLUSIONS

The high response rate of 47% (95% CI 31% to 61%) confirms that TMZ chemotherapy is a valid option in the treatment of progressive LGG. The present preliminary results seem interesting and warrant further evaluation of TMZ clinical activity in a larger series of progressive LGG.

PTEN protein expression correlates with PTEN gene molecular changes but not with VEGF expression in astrocytomas

PTEN gene (10q23) is a relevant tumor suppressor gene whose protein is a phosphatase involved in the control of angiogenesis of some tumors including astrocytomas. There are no studies correlating molecular changes of PTEN and the immunohistochemical expression of its protein (pPTEN) with the expression of vascular endothelial growth factor (VEGF) in astrocytomas. Fifty-six surgically resected brain gliomas, 10 grade 2, 16 grade 3, and 30 grade 4, were studied by a combined approach, consisting of (1) PCR analysis using four microsatellite markers against the PTEN gene region (10q23), (2) the FISH technique to test chromosome 10 using a pericentromeric probe, and (3) immunohistochemical evaluation of pPTEN and VEGF. Loss of heterozygosity (LOH) of PTEN was observed in 10% of fibrillary grade 2 astrocytomas and all gemistocytic ones. In high-grade tumors, LOH was more frequent in grade 4 than in grade 3 (> or =2 loci deleted, 83% and 56%, respectively). Monosomy for chromosome 10 was observed especially in high-grade tumors (6% of grade 3 and 50% of grade 4) and in 20% of grade 2 tumors, corresponding to gemistocytic astrocytomas. Results with both antibodies against PTEN were concordant: loss of cytoplasmic immunoreactivity was frequently observed according to homogeneous or heterogeneous patterns in 70% and 50% of grades 4 and 3, respectively, but not in grade 2. Immunonegativity of pPTEN was associated with PTEN gene deletion (> or =2 loci deleted) (P = 0.04) but not with monosomy. Cytoplasmic immunoreactivity against VEGF was observed in high-grade and in gemistocytic astrocytomas, but not in conventional grade 2 tumors. Tumor expression of pPTEN was not associated with immunoreactivity against VEGF when the same areas were considered. In conclusion, loss of PTEN expression is frequent in high-grade astrocytomas, but not in grade 2 tumors, and correlates with PTEN deletion and loss of chromosome 10. PTEN immunoreactivity does not correlate with VEGF expression in astrocytomas when similar areas are considered.

Growth, invasion, metastasis, differentiation, angiogenesis and apoptosis of gastric cancer regulated by expression of PTEN encoding products

AIM: To investigate expression of PTEN in gastric cancer and to explore its roles in tumorigenesis and progression of gastric cancer.

METHODS: Formalin-fixed and paraffin-embedded tissues of adjacent non-tumor mucosa and primary foci from 113 cases of gastric cancers were studied for the expression of PTEN and Caspase-3 and microvessel density (MVD) by streptavidin-peroxidase (S-P) immunohistochemistry with antibodies against PTEN, Caspase-3, and CD34. The relationship between PTEN and Caspase 3 expression and clinicopathological parameters of tumors was compared.

RESULTS: Primary gastric cancer cells expressed PTEN less frequently than adjacent epithelial cells of primary foci (54.9% vs 89.4%; P = 0.000, χ² = 33.474). PTEN expression was significantly associated with invasive depth (P = 0.003, rs = 0.274), metastasis (P = 0.036, rs = 0.197), growth pattern (P=0.008, rs = 0.282), Lauren’s classification (P = 0.000, rs = 0.345), and histological classification (P = 0.005, rs = 0.262) of tumors, but not with tumor size (P = 0.639, rs = 0.045), Borrmann’s classification (P = 0.544, rs = 0.070) or TNM staging (P = 0.172, rs = 0.129). PTEN expression was negatively correlated with MDV in primary gastric cancer (P = 0.020, F = 5.558). Primary gastric cancer cells showed less frequent immunoreactivity to Caspase-3 than adjacent epithelial cells of primary foci (32.7% vs 50.4%; P = 0.007, χ² = 7.286). Caspase-3 expression was dependent of PTEN expression in primary gastric cancer cells (P = 0.000, χ² = 15.266).

CONCLUSION: Down-regulated expression of PTEN plays an important role in tumorigenesis, progression, growth, differentiation and angiogenesis of gastric cancer. Low expression of PTEN can decrease expression of Caspase-3 to disorder apoptosis of tumor cells, which might explain the molecular mechanisms of PTEN contributions to tumorigenesis and progression of gastric cancer.

Radiation sensitization of human cancer cells in vivo by inhibiting the activity of PI3K using LY294002

Multiple genetic alterations such as in Ras or EGFR can result in sustained signaling through PI3K. Our previous experiments have shown that resistance to radiation results from PI3K activity in cells in culture. Here we examined whether inhibition of PI3K in vivo would sensitize tumors to radiation. The human bladder cancer cell line T24 has amplified and mutated H-Ras resulting in sustained PI3K activity and phosphorylation of the downstream target of PI3K, Akt. Nude mice bearing T24 tumor cell xenografts were randomly assigned to one of four groups: control, radiation alone, the PI3K inhibitor LY294002 alone, or combined LY294002 and radiation. The LY294002 was delivered intraperitoneally to the mice. Downregulation of Akt was documented by Western blot analysis of tumor lysates. In vivo sensitization was measured using clonogenic assays or regrowth assays.A dose of 100 mg/kg of LY294002, but not 50 mg/kg, consistently eliminated the phosphorylation of Akt. This inhibition was transient, and Akt activity returned after 30 min. This dose resulted in severe respiratory depression and lethargy resolving without lethality. It is not possible to tell whether these side effects of LY294002 were mechanism-based or idiosyncratic. The PI3K inhibitor LY294002 by itself had minimal antitumor effect. The combination of LY294002 and radiation resulted in significant and synergistic reduction in clonogenicity and growth delay. Inhibition of PI3K by LY294002 can synergistically enhance radiation efficacy. This acts as a proof of principle that inhibition of the Ras to PI3K pathway could be useful clinically.

Molecular genetic analysis of anaplastic pleomorphic xanthoastrocytoma

A case of pleomorphic xanthoastrocytoma in a 10-year-old Malay boy is reported. The patient presented with headache and epilepsy. On computed tomography, a ring-enhancing low-density lesion was observed in the left fronto-temporal area. During surgery, a cystic tumour containing serous fluid was found and almost totally removed. Histologically, the tumour exhibited marked pleomorphism of oval and spindle-shaped cells intermixed with uni- and multinucleated giant cells, and xanthomatous cells with foamy cytoplasm. The tumour displayed pericellular reticulin and periodic acid-Schiff positive granules. Focally, six mitotic characters per 10 high-power fields were seen, and necrosis was confined only to the inner lining of the cyst. Mutational analysis showed that a frameshift mutation (a 4-bp deletion) in the p53 gene had occurred in codons 273 and 274 of exon 8. No mutation was detected in the p16 gene. No allelic loss and/or loss of heterozygosity were observed on chromosome 10 using microsatellite marker D105532. The patient was treated with postoperative radiotherapy because of histological anaplasia and the presence of residual tumour. The patient showed marked neurological recovery after a follow-up period of 2 years.

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.

PTEN encoding product: A marker for tumorigenesis and progression of gastric carcinoma

AIM: To detect the expression of PTEN encoding product in normal mucosa, intestinal metaplasia (IM), dysplasia and carcinoma of the stomach, and to investigate its clinical implication in tumorigenesis and progression of gastric carcinoma.

METHODS: Formalin-fixed paraffin embedded specimens from 184 cases of gastric carcinoma, their adjacent normal mucosa, IM and dysplasia were evaluated for PTEN protein expression by SABC immunohistochemistry. PTEN expression was compared with tumor stage, lymph node metastasis, Lauren’s and WHO’s histological classification of gastric carcinoma. Expression of VEGF was also detected in 60 cases of gastric carcinoma and its correlation with PTEN was concerned.

RESULTS: The positive rates of PTEN protein were 100% (102/102), 98.5% (65/66), 66.7% (4/6) and 47.8% (88/184) in normal mucosa, IM, dysplasia and carcinoma of the stomach, respectively. The positive rates in dysplasia and carcinoma were lower than in normal mucosa and IM (P < 0.01). Advanced gastric cancers expressed less frequent PTEN than early gastric cancer (42.9% vs 67.6%, P < 0.01). The positive rate of PTEN protein was lower in gastric cancer with than without lymph node metastasis (40.3% vs 63.3%, P < 0.01). PTEN was less expressed in diffuse-type than in intestinal-type gastric cancer (41.5% vs 57.8%, P < 0.05). Signet ring cell carcinoma showed the expression of PTEN at the lowest level (25.0%, 7/28); less than well and moderately differentiated ones (P < 0.01). Expression of PTEN was not correlated with expression of VEGF (P > 0.05).

CONCLUSION: Loss or reduced expression of PTEN protein occures commonly in tumorigenesis and progression of gastric carcinoma. It is suggested that PTEN can be an objective marker for pathologically biological behaviors of gastric carcinoma.

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.

The prognostic molecular markers in hepatocellular carcinoma

The prognosis of hepatocellular carcinoma (HCC) still remains dismal, although many advances in its clinical study have been made. It is important for tumor control to identify the factors that predispose patients to death. With new discoveries in cancer biology, the pathological and biological prognostic factors of HCC have been studied quite extensively. Analyzing molecular markers (biomarkers) with prognostic significance is a complementary method. A large number of molecular factors have been shown to associate with the invasiveness of HCC, and have potential prognostic significance. One important aspect is the analysis of molecular markers for the cellular malignancy phenotype. These include alterations in DNA ploidy, cellular proliferation markers (PCNA, Ki-67, Mcm2, MIB1, MIA, and CSE1L/CAS protein), nuclear morphology, the p53 gene and its related molecule MD M2, other cell cycle regulators (cyclin A, cyclin D, cyclin E, cdc2, p27, p73), oncogenes and their receptors (such as ras, c-myc, c-fms, HGF, c-met, and erb-B receptor family members), apoptosis related factors (Fas and FasL), as well as telomerase activity. Another important aspect is the analysis of molecular markers involved in the process of cancer invasion and metastasis. Adhesion molecules (E-cadherin, catenins, serum intercellular adhesion molecule-1, CD44 variants), proteinases involved in the degradation of extracellular matrix (MMP-2, MMP-9, uPA, uPAR, PAI), as well as other molecules have been regarded as biomarkers for the malignant phenotype of HCC, and are related to prognosis and therapeutic outcomes. Tumor angiogenesis is critical to both the growth and metastasis of cancers including HCC, and has drawn much attention in recent years. Many angiogenesis-related markers, such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), platelet-derived endothelial cell growth factor (PD-ECGF), thrombospondin (TSP), angiogenin, pleiotrophin, and endostatin (ES) levels, as well as intratumor microvessel density (MVD) have been evaluated and found to be of prognostic significance. Body fluid (particularly blood and urinary) testing for biomarkers is easily accessible and useful in clinical patients. The prognostic significance of circulating DNA in plasma or serum, and its genetic alterations in HCC are other important trends. More attention should be paid to these two areas in future. As the progress of the human genome project advances, so does a clearer understanding of tumor biology, and more and more new prognostic markers with high sensitivity and specificity will be found and used in clinical assays. However, the combination of some items, i.e., the pathological features and some biomarkers mentioned above, seems to be more practical for now.