Expression of p16(INK4A) induces dominant suppression of glioblastoma growth in situ through necrosis and cell cycle arrest

Recent advances in the detection of glioblastoma, from imaging-based methods to proteomics and biosensors: A narrative review

Glioblastoma (GBM) is an aggressive type of cancer that originates in the cells called astrocytes, which support the functioning of nerve cells. It can develop in either the brain or the spinal cord and is also known as glioblastoma multiform. GBM is a highly aggressive cancer that can occur in either the brain or spinal cord. The detection of GBM in biofluids offers potential advantages over current methods for diagnosing and treatment monitoring of glial tumors. Biofluid-based detection of GBM focuses on identifying tumor-specific biomarkers in blood and cerebrospinal fluid. To date, different methods have been used to detect biomarkers of GBM, ranging from various imaging techniques to molecular approaches. Each method has its own strengths and weaknesses. The present review aims to scrutinize multiple diagnostic methods for GBM, with a focus on proteomics methods and biosensors. In other words, this study aims to provide an overview of the most significant research findings based on proteomics and biosensors for the diagnosis of GBM.

Glioma-Targeted Therapeutics: Computer-Aided Drug Design Prospective

Amongst the several types of brain cancers known to humankind, glioma is one of the most severe and life-threatening types of cancer, comprising 40% of all primary brain tumors. Recent reports have shown the incident rate of gliomas to be 6 per 100,000 individuals per year globally. Despite the various therapeutics used in the treatment of glioma, patient survival rate remains at a median of 15 months after undergoing first-line treatment including surgery, radiation, and chemotherapy with Temozolomide. As such, the discovery of newer and more effective therapeutic agents is imperative for patient survival rate. The advent of computer-aided drug design in the development of drug discovery has emerged as a powerful means to ascertain potential hit compounds with distinctively high therapeutic effectiveness against glioma. This review encompasses the recent advances of bio-computational in-silico modeling that have elicited the discovery of small molecule inhibitors and/or drugs against various therapeutic targets in glioma. The relevant information provided in this report will assist researchers, especially in the drug design domains, to develop more effective therapeutics against this global disease.

Against the Resilience of High-Grade Gliomas: Gene Therapies (Part II)

Introduction: High-grade gliomas (HGGs) still have a high rate of recurrence and lethality. Gene therapies were projected to overcome the therapeutic resilience of HGGs, due to the intrinsic genetic heterogenicity and immune evasion pathways. The present literature review strives to provide an updated overview of the novel gene therapies for HGGs treatment, highlighting evidence from clinical trials, molecular mechanisms, and future perspectives. Methods: An extensive literature review was conducted through PubMed/Medline and ClinicalTrials.gov databases, using the keywords “high-grade glioma,” “glioblastoma,” and “malignant brain tumor”, combined with “gene therapy,” “oncolytic viruses,” “suicide gene therapies,” “tumor suppressor genes,” “immunomodulatory genes,” and “gene target therapies”. Only articles in English and published in the last 15 years were chosen, further screened based on best relevance. Data were analyzed and described according to the PRISMA guidelines. Results: Viruses were the most vehicles employed for their feasibility and transduction efficiency. Apart from liposomes, other viral vehicles remain largely still experimental. Oncolytic viruses and suicide gene therapies proved great results in phase I, II preclinical, and clinical trials. Tumor suppressor, immunomodulatory, and target genes were widely tested, showing encouraging results especially for recurrent HGGs. Conclusions: Oncolytic virotherapy and suicide genes strategies are valuable second-line treatment options for relapsing HGGs. Immunomodulatory approaches, tumor suppressor, and target genes therapies may implement and upgrade standard chemoradiotherapy. Future research aims to improve safety profile and prolonging therapeutic effectiveness. Further clinical trials are needed to assess the efficacy of gene-based therapies.

Current Approaches for Glioma Gene Therapy and Virotherapy

Glioblastoma (GBM) is the most common and aggressive primary brain tumor in the adult population and it carries a dismal prognosis. Inefficient drug delivery across the blood brain barrier (BBB), an immunosuppressive tumor microenvironment (TME) and development of drug resistance are key barriers to successful glioma treatment. Since gliomas occur through sequential acquisition of genetic alterations, gene therapy, which enables to modification of the genetic make-up of target cells, appears to be a promising approach to overcome the obstacles encountered by current therapeutic strategies. Gene therapy is a rapidly evolving field with the ultimate goal of achieving specific delivery of therapeutic molecules using either viral or non-viral delivery vehicles. Gene therapy can also be used to enhance immune responses to tumor antigens, reprogram the TME aiming at blocking glioma-mediated immunosuppression and normalize angiogenesis. Nano-particles-mediated gene therapy is currently being developed to overcome the BBB for glioma treatment. Another approach to enhance the anti-glioma efficacy is the implementation of viro-immunotherapy using oncolytic viruses, which are immunogenic. Oncolytic viruses kill tumor cells due to cancer cell-specific viral replication, and can also initiate an anti-tumor immunity. However, concerns still remain related to off target effects, and therapeutic and transduction efficiency. In this review, we describe the rationale and strategies as well as advantages and disadvantages of current gene therapy approaches against gliomas in clinical and preclinical studies. This includes different delivery systems comprising of viral, and non-viral delivery platforms along with suicide/prodrug, oncolytic, cytokine, and tumor suppressor-mediated gene therapy approaches. In addition, advances in glioma treatment through BBB-disruptive gene therapy and anti-EGFRvIII/VEGFR gene therapy are also discussed. Finally, we discuss the results of gene therapy-mediated human clinical trials for gliomas. In summary, we highlight the progress, prospects and remaining challenges of gene therapies aiming at broadening our understanding and highlighting the therapeutic arsenal for GBM.

Comparing the effects of different cell death programs in tumor progression and immunotherapy

Our conception of programmed cell death has expanded beyond apoptosis to encompass additional forms of cell suicide, including necroptosis and pyroptosis; these cell death modalities are notable for their diverse and emerging roles in engaging the immune system. Concurrently, treatments that activate the immune system to combat cancer have achieved remarkable success in the clinic. These two scientific narratives converge to provide new perspectives on the role of programmed cell death in cancer therapy. This review focuses on our current understanding of the relationship between apoptosis and antitumor immune responses and the emerging evidence that induction of alternate death pathways such as necroptosis could improve therapeutic outcomes.

Simultaneous miRNA and mRNA transcriptome profiling of glioblastoma samples reveals a novel set of OncomiR candidates and their target genes

Although glioblastomas are common, there remains a need to elucidate the underlying mechanisms behind their initiation and progression and identify molecular pathways for improving treatment. In this study, sixteen fresh-frozen glioblastoma samples and seven samples of healthy brain tissues were analyzed with miRNA and whole transcriptome microarray chips. Candidate miRNAs and mRNAs were selected to validate expression in fifty patient samples in total with the criteria of abundance, relevance and prediction scores. miRNA and target mRNA relationships were assessed by inhibiting selected miRNAs in glioblastoma cells. Functional tests have been conducted in order to see the effects of miRNAs on invasion, migration and apoptosis of GBM cells. Analyses were carried out to determine correlations between selected molecules and clinicopathological features. 1332 genes and 319 miRNAs were found to be dysregulated by the microarrays. The results were combined and analyzed with Transcriptome Analysis Console 3 software and the DAVID online database. Primary differential pathways included Ras, HIF-1, MAPK signaling and cell adhesion. OncomiR candidates 21-5p, 92b-3p, 182-5p and 339-5p for glioblastoma negatively correlated with notable mRNA targets both in tissues and in in vitro experiments. miR-21-5p and miR-339-5p significantly affected migration, invasion and apoptosis of GBM cells in vitro. Significant correlations with overall survival, tumor volume, recurrence and age at diagnosis were discovered. In this article we present valuable integrated microarray analysis of glioblastoma samples regarding miRNA and gene-expression levels. Notable biomarkers and miRNA-mRNA interactions have been identified, some of which correlated with clinicopathological features in our cohort.

Evaluation of the use of therapeutic peptides for cancer treatment

Cancer along with cardiovascular disease are the main causes of death in the industrialised countries around the World. Conventional cancer treatments are losing their therapeutic uses due to drug resistance, lack of tumour selectivity and solubility and as such there is a need to develop new therapeutic agents. Therapeutic peptides are a promising and a novel approach to treat many diseases including cancer. They have several advantages over proteins or antibodies: as they are (a) easy to synthesise, (b) have a high target specificity and selectivity and (c) have low toxicity. Therapeutic peptides do have some significant drawbacks related to their stability and short half-life. In this review, strategies used to overcome peptide limitations and to enhance their therapeutic effect will be compared. The use of short cell permeable peptides that interfere and inhibit protein-protein interactions will also be evaluated.

Amplified and homozygously deleted genes in glioblastoma: impact on gene expression levels

BACKGROUND

Glioblastoma multiforme (GBM) displays multiple amplicons and homozygous deletions that involve relevant pathogenic genes and other genes whose role remains unknown.

METHODOLOGY

Single-nucleotide polymorphism (SNP)-arrays were used to determine the frequency of recurrent amplicons and homozygous deletions in GBM (n = 46), and to evaluate the impact of copy number alterations (CNA) on mRNA levels of the genes involved.

PRINCIPAL FINDINGS

Recurrent amplicons were detected for chromosomes 7 (50%), 12 (22%), 1 (11%), 4 (9%), 11 (4%), and 17 (4%), whereas homozygous deletions involved chromosomes 9p21 (52%) and 10q (22%). Most genes that displayed a high correlation between DNA CNA and mRNA levels were coded in the amplified chromosomes. For some amplicons the impact of DNA CNA on mRNA expression was restricted to a single gene (e.g., EGFR at 7p11.2), while for others it involved multiple genes (e.g., 11 and 5 genes at 12q14.1-q15 and 4q12, respectively). Despite homozygous del(9p21) and del(10q23.31) included multiple genes, association between these DNA CNA and RNA expression was restricted to the MTAP gene.

CONCLUSIONS

Overall, our results showed a high frequency of amplicons and homozygous deletions in GBM with variable impact on the expression of the genes involved, and they contributed to the identification of other potentially relevant genes.

Correlation analysis between the expression of P21WAF1/CIP1, P16 proteins and human glioma

AIM

Glioma is the most common neoplasm of the brain. Unfortunately, surgical cure of it is practically impossible and clinical course is primarily determined by the biological behaviour of the tumour cells. The purpose of this study was to investigate the correlation between the expression levels of P21WAF1/CIP1, P16 proteins and the grading of glioma.

METHODS

T98G human glioma cell line, normal human astrocyte (HA) cell line, tumour tissue samples from 70 patients suffering from glioma and normal brain tissues from 20 cases with brain contusion were investigated. The expression levels of P21WAF1/CIP1 and P16 proteins were detected using SABC immunohistochemical staining and semi-quantitive reverse transcriptase polymerase chain reaction (RT-PCR) assay. Then, the correlation of the two markers' expression with glioma grading of patients was analysed.

RESULTS

The expression levels of P21WAF1/CIP1 and P16 proteins in the T98G cell line were much lower than that in the HA cell line. Their positive expression rates in glioma tissues were 55.71% and 42.86% respectively, and a significant increase was observed in normal brain tissues (p = 0.012, 0.008). Combined with the result of semi-quantitive RT-PCR, we could demonstrate that the expression intensity of P21WAF1/CIP1 and P16 decreased with the glioma grade increase. Co-expression of them was also found in glioma and normal brain tissues. Furthermore, there was a negative correlation between the two markers' expression and glioma grading of patients (rs = -0.68, -0.56).

CONCLUSIONS

The positive expression rate and co-expression rate of P21WAF1/CIP1 and P16 proteins could reflect the malignant grade of glioma to some extent, and they can be considered as a sensitive index for glioma grading.

P53 gene mutation and expression of MDM2, P53, P16 protein and their relationship in human glioma

To investigate the effect of P53 protein accumulation and p53 gene mutation in the pathogenesis of glioma and to study the role of MDM2, P53 and P16 protein in glioma formation and progression and their relationship with each other, LSAB immunohistochemical staining method and non-isotopic PCR-SSCP techniques were used to detect the expression of MDM2, P53 and P16 protein and p53 gene mutation in 48 cases of gliomas. The results showed that the positive expression rate of MDM2, P53 and the negative rate of P16 was 22.9%, 41.7% and 60.4%, respectively. The latter two in high grade (grade III, IV) gliomas had a significantly higher rate than in the low grade (grade II) gliomas. Moreover, the co-expression of MDM2 and P53 protein was confirmed in only 1 of 48 cases. No significant difference was found in the rate of the expression of MDM2 between high grade and low grade gliomas (P > 0.1). PCR-SSCP results showed that mutation of 5-8 exons of p53 gene was detected in 17 out of 48 cases (35.42%). Mutation was detected in 16 of 20 cases of positive p53 expression, and another one was detected in 28 cases of negative expression cases. The correlation between p53 mutation and p53 immunopositivity was observed in 89.6% of the cases. P53 gene mutation and the level of MDM2, P53 and P16 protein were not related to age, gender of the patients, tumor location and size. It is concluded that the mutation of p53 and deletion of p16 might play important roles in the tumorigenesis of gliomas and it was significantly associated with the grade of tumor differentiation. P53 protein accumulation can indirectly reflect p53 mutation. MDM2 amplification and overexpression might be an early event in the growth of human gliomas.

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

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

Simvastatin Induces Death of Multiple Myeloma Cell Lines

Background

Accumulating reports indicate that statins widely prescribed for hypercholesteromia have antineoplastic activity. We hypothesized that because statins inhibit farnesylation of Ras that is often mutated in multiple myeloma (MM), as well as the production of interleukin (IL)-6, a key cytokine in MM, they may have antiproliferative and/or proapoptotic effects in this malignancy.

Methods

U266, RPMI 8226, and ARH77 were treated with simvastatin (0–30 μM) for 5 days. The following aspects were evaluated: viability (IC50), cell cycle, cell death, cytoplasmic calcium ion levels, supernatant IL-6 levels, and tyrosine kinase activity.

Results

Exposure of all cell lines to simvastatin resulted in reduced viability with IC50s of 4.5 μM for ARH77, 8 μM for RPMI 8226, and 13 μM for U266. The decreased viability is attributed to cell-cycle arrest (U266, G1; RPMI 8226, G2M) and cell death. ARH77 underwent apoptosis, whereas U266 and RPMI 8226 displayed a more necrotic form of death. Cytoplasmic calcium levels decreased significantly in all treated cell lines. IL-6 secretion from U266 cells was abrogated on treatment with simvastatin, whereas total tyrosine phosphorylation was unaffected. Conclusions: Simvastatin displays significant antimyeloma activity in vitro. Further research is warranted for elucidation of the modulated molecular pathways and clinical relevance.

Differential effects of two growth inhibitory K vitamin analogs on cell cycle regulating proteins in human hepatoma cells

A comparison was made between two K vitamin analogs. Growth in vitro of Hep G2 hepatoma cells was inhibited both by Compound 5 (Cpd 5), a recently synthesized thioalkyl analog of vitamin K or 2-(2-mercaptoethanol)-3-methyl-1, 4-naphthoquinone, as well as by synthetic vitamin K3 (menadione). Using synchronized Hep G2 hepatoma cells, the actions of both Cpd 5 and vitamin K3 on cell cycle regulating proteins were examined. Cpd 5 decreased the levels of cyclin D1, Cdk4, p16, p21 and cyclin B1. By contrast, VK3 only decreased the level of cyclin D1, but had no effect on the levels of Cdk4, p16 or p21. Interestingly, both VK3 and VK2 increased the levels of p21. The naturally occurring K vitamins had little effect on cell growth and none on the cyclins or Cdks. Amounts and activity of the G1/S phase controlling Cdc25A were measured. We found that Cpd 5 directly inhibited both Cdc25A activity and its protein expression, whereas VK3 did not. Thus, the main effects of Cpd 5 were on G1 and S phase proteins, especially Cdk4 and Cdc25A amounts in contrast to VK3. Computer docking studies of Cpd 5 and VK3 to Cdc25A phosphatase showed three binding sites. In the best conformation, Cpd 5 was found to be closer to the enzyme active site than VK3. These findings show that Cpd 5 represents a new class of anticancer agent, being a protein tyrosine phosphatase (PTP) antagonist, that binds to Cdc25A with suppression of its activity. Tumors expressing high levels of oncogenic Cdc25A phosphatase may thus be susceptible to the growth inhibitory activities of this class of compound.

Conditional expression of the tumor suppressor p16 in a heterotopic glioblastoma model results in loss of pRB expression

We have expressed the tumor suppressor p16 under the control of a tetracycline-sensitive promoter in two human glioblastoma cell lines which do not contain endogenous p16. Ectopic p16 expression led to a stable but reversible G1 phase cell cycle arrest, reduced the growth of both cell lines in cell culture, and almost abolished their in vitro tumorigenicity. U-87MG-tTA-p16 glioblastoma cells consistently formed tumors after subcutaneous injection into the flanks of nude mice. p16 expression in these tumors was strictly dependent on the presence or absence of tetracycline in the drinking water. Ectopic p16 reduced the tumor take rate (in vivo tumorigenicity) of U-87MG-tTA-p16 cells from 18/20 (90%) to 5 tumors/12 (42%) tumor cell injections. p16 positive and negative tumors differed with respect to their Ki67 labeling indices (34 +/- 4% vs. 52 +/- 6% , P < 0.001, student's t-test). These data are consistent with an in vitro and in vivo glioma suppressor role for p16. Interestingly, we observed a secondary reduction of pRB expression in tumors (and cell cultures) exposed to p16 for > or = 10 (6) days. pRB is p16's major downstream target. Hence, this finding might explain, why p16 expression neither significantly affected the morphology nor led to a reduction of size or growth rate of the tumors. Loss of pRB following p16 expression might severely limit the potential benefit of p16 gene therapy for glioblastoma.

Retroviral transfer of the p16INK4a cDNA inhibits C6 glioma formation in Wistar rats

BACKGROUND: The p16INK4A gene product halts cell proliferation by preventing phosphorylation of the Rb protein. The p16INK4a gene is often deleted in human glioblastoma multiforme, contributing to unchecked Rb phosphorylation and rapid cell division. We show here that transduction of the human p16INK4a cDNA using the pCL retroviral system is an efficient means of stopping the proliferation of the rat-derrived glioma cell line, C6, both in tissue culture and in an animal model. C6 cells were transduced with pCL retrovirus encoding the p16INK4a, p53, or Rb genes. These cells were analyzed by a colony formation assay. Expression of p16INK4a was confirmed by immunohistochemistry and Western blot analysis. The altered morphology of the p16-expressing cells was further characterized by the senescence-associated beta-galactosidase assay. C6 cells infected ex vivo were implanted by stereotaxic injection in order to assess tumor formation. RESULTS: The p16INK4a gene arrested C6 cells more efficiently than either p53 or Rb. Continued studies with the p16INK4a gene revealed that a large portion of infected cells expressed the p16INK4a protein and the morphology of these cells was altered. The enlarged, flat, and bi-polar shape indicated a senescence-like state, confirmed by the senescence-associated beta-galactosidase assay. The animal model revealed that cells infected with the pCLp16 virus did not form tumors. CONCLUSION: Our results show that retrovirus mediated transfer of p16INK4a halts glioma formation in a rat model. These results corroborate the idea that retrovirus-mediated transfer of the p16INK4a gene may be an effective means to arrest human glioma and glioblastoma.

Comparisons of tumor suppressor p53, p21, and p16 gene therapy effects on glioblastoma tumorigenicity in situ

The mutation and/or deletion of tumor suppressor genes have been postulated to play a major role in the genesis and the progression of gliomas. In this study, the functional expression and efficacy in tumor suppression of 3 tumor suppressor genes (p53, p21, and p16) were tested and compared in a rat GBM cell line (RT-2) after retrovirus mediated gene delivery in vitro and in vivo. Significant reductions in tumor cell growth rate were found in p16 and p21 infected cells (60 +/- 12% vs 66 +/- 15%) compared to p53 (35 +/- 9%). In vitro colony formation assay also showed significant reductions after p16 and p21 gene delivery (98 +/- 5% vs 91 +/- 10%) compared to p53 (50 +/- 18%). In addition, the tumor suppression efficacy were investigated and compared in vivo. Retroviral mediated p16 and p21 gene deliveries in glioblastomas resulted in more than 90% reductions in tumor growth (92 +/- 26% vs 90 +/- 22%) compared to p53 (62 +/- 18%). Tumor suppressor gene insertions in situ further prolonged animal survival. Overall p16 and p21 genes showed more powerful tumor suppressor effects than p53. The results were not surprising, as p16 and p21 are more downstream in the cell cycle regulatory pathway compared to p53. Moreover, the mechanism involved in each of their suppressor effects is different. This study demonstrates the feasibility of using tumor suppressor genes in regulating the growth of glioma in vitro and in situ.

Norcantharidin-induced post-G(2)/M apoptosis is dependent on wild-type p53 gene

Norcantharidin (NCTD), a synthetic analogue of phosphatase type 2A inhibitors, cantharidin, was shown to have limited effects in treating human and animal tumors. The tumor cell killing mechanisms by norcantharidin, however, remain unclear. In this report, we wished to investigate the mechanisms of norcantharidin-mediated cytotoxicity. Effort was made to investigate whether norcantharidin exerted its cytotoxicity through a p53-dependent or -independent mechanism. RT-2 (wtp53) and U251 (mutant p53) glioblastoma cell lines were exposed to norcantharidin at different dosages. Time-course fluorescent-activated cell sorting (FACS) analysis showed that high doses of norcantharidin arrested the cells at the G(2)/M phase and subsequent post-G(2)/M apoptosis in RT-2 cell line. In comparison, the U251 cell line was found resistant to norcantharidin-induced cytotoxicity. Restoring wild-type p53 gene function in the U251 cell line after adenoviral infections induced tumor cell cytotoxicity after exposure to norcantharidin. These results showed that norcantharidin kills tumor cells efficiently corresponding to their endogenous p53 gene status. The results also showed the feasibility of using adenoviral p53 gene therapy to enhance chemosensitivity of tumor cells to norcantharidin.