Comparative Analysis of External and Internal Radiotherapy- Dependent Plans in Patients with Gynecological Cancer.

Background/Aim: Radiotherapy plays a key role in the treatment of gynecological cancer. Modern radiotherapy techniques with external beams (e-RT) are applied in a broad spectrum of gynecological cancer cases. However, high radiation doses, affecting normal tissue adjacent to cancer, represent the main disadvantage of e-RT regimens. For this reason, brachytherapy (BT), an internal beam-based technique (i-RT), is suggested following e-RT. Our purpose was to compare e-RT plans using volumetric-modulated arc therapy (VMAT) with those using 3D conformal techniques (3D-CRT) and compare BT plans guided by 3D or 2D imaging based on the potential corresponding toxicity levels. Materials and Methods: In this preliminary, non-randomized comparative retrospective study, 15 females suffering gynecological cancer were enrolled. Modern e-RT and i-RT (BT) techniques were applied. Results: Concerning e-RT, D95/D99/rectum 2cc/bladder 2cc and small intestine 2cc were measured and compared; in i-RT, rectum 2cc/bladder 2cc were measured and compared. The median dose to the planning target volume in VMAT was 97.4 Gy compared with 92.9 Gy in 3D-CRT. Τhe rectum received almost 5 Gy less in VMAT compared to 3D-CRT (median of 43.5 Gy vs. 48.6 Gy; p=0.001). In the bladder, dose differences were minimal, while the small intestine received 47.6 Gy in VMAT (p=0.001). Regarding 3D-BT, the rectum received 63.1 Gy compared with 49.9 Gy (p=0.009) in 2D-BT. Concerning the bladder, mean 2D-BT and 3D-BT doses were 71.9 and 65 Gy, respectively, differing non-significantly. Conclusion: VMAT was found to be superior to 3D-CRT, especially in dose distribution, volume coverage and protection of critical organs. Similarly, 3D-BT should be preferred over 2D-BT due to critical advantages.

Graphene oxide and oxidized carbon nanodiscs as biomedical scaffolds for the targeted delivery of quercetin to cancer cells.

Targeting cancer cells without affecting normal cells poses a particular challenge. Nevertheless, the utilization of innovative nanomaterials in targeted cancer therapy has witnessed significant growth in recent years. In this study, we examined two layered carbon nanomaterials, graphene and carbon nanodiscs (CNDs), both of which possess extraordinary physicochemical and structural properties alongside their nano-scale dimensions, and explored their potential as nanocarriers for quercetin, a bioactive flavonoid known for its potent anticancer properties. Within both graphitic allotropes, oxidation results in heightened hydrophilicity and the incorporation of oxygen functionalities. These factors are of great significance for drug delivery purposes. The successful oxidation and interaction of quercetin with both graphene (GO) and CNDs (oxCNDs) have been confirmed through a range of characterization techniques, including FTIR, Raman, and XPS spectroscopy, as well as XRD and AFM. In vitro anticancer tests were conducted on both normal (NIH/3T3) and glioblastoma (U87) cells. The results revealed that the bonding of quercetin with GO and oxCNDs enhances its cytotoxic effect on cancer cells. GO-Quercetin and oxCNDs-Quercetin induced G0/G1 cell cycle arrest in U87 cells, whereas oxCNDs caused G2/M arrest, indicating a distinct mode of action. In long-term survival studies, cancer cells exhibited significantly lower viability than normal cells at all corresponding doses of GO-Quercetin and oxCNDs-Quercetin. This work leads us to conclude that the conjugation of quercetin to GO and oxCNDs shows promising potential for targeted anticancer activity. However, further research at the molecular level is necessary to substantiate our preliminary findings.

Comparative Expression Analysis of TP53 Tumor Suppressor and MDM2 Oncogene in Colorectal Adenocarcinoma.

Background/Aim: The tumor protein 53 (TP53) tumor suppressor protein (17p13.1) acts as a significant regulator for the cell cycle normal function. The gene is frequently mutated in colorectal adenocarcinoma (CRC) patients and is associated to poor prognosis and low response rates to chemo-targeted therapy. Our purpose was to correlate TP53 expression with Mouse Double Minute 2 Homolog (MDM2), a proto-oncogene (12q14.3) and a major negative regulator in the TP53-MDM2 auto-regulatory pathway. Materials and Methods: A total of forty (n=40) colorectal adenocarcinoma (CRC) cases were included in this study. An immunohistochemistry-based assay was implemented by using anti-TP53 and anti-MDM2 antibodies in the corresponding tissue sections. Additionally, a digital image analysis assay was implemented for objectively measuring TP53/MDM2 immunostaining intensity levels. Results: TP53 protein overexpression was detected in 27/40 (67.5%), whereas MDM2 overexpression in 28/40 (70%) cases. Interestingly, in 21/40 (52.5%) cases, a combined TP53/MDM2 co-expression was detected, whereas in 6/40 (15%), a combined loss of expression was identified (overall co-expression: p=0.119). p53 overexpression was significantly correlated to grade of the examined cases (p=0.001), whereas MDM2 to stage and max diameter of the malignancies (p=0.001 and 0.024, respectively). Conclusion: TP53/MDM2 over expression is a frequent and significant genetic event in CRCs associated with an aggressive biological behavior, as a result of increased dedifferentiation grade and advanced stage/elevated tumor volume, respectively. MDM2 oncogene overactivation combined with mutated and overexpressed TP53 is observed in sub-groups of patients leading to specific gene/protein signatures - targets for personalized chemotherapeutic approaches.

Longitudinal Muscle Biopsies Reveal Inter- and Intra-Subject Variability in Cancer Cachexia: Paving the Way for Biopsy-Guided Tailored Treatment.

In the rapidly evolving landscape of cancer cachexia research, the development and refinement of diagnostic and predictive biomarkers constitute an ongoing challenge. This study aims to introduce longitudinal muscle biopsies as a potential framework for disease monitoring and treatment. The initial feasibility and safety assessment was performed for healthy mice and rats that received two consecutive muscle biopsies. The assessment was performed by utilizing three different tools. Subsequently, the protocol was also applied in leiomyosarcoma tumor-bearing rats. Longitudinal muscle biopsies proved to be a safe and feasible technique, especially in rat models. The application of this protocol to tumor-bearing rats further affirmed its tolerability and feasibility, while microscopic evaluation of the biopsies demonstrated varying levels of muscle atrophy with or without leukocyte infiltration. In this tumor model, sequential muscle biopsies confirmed the variability of the cancer cachexia evolution among subjects and at different time-points. Despite the abundance of promising cancer cachexia data during the past decade, the full potential of muscle biopsies is not being leveraged. Sequential muscle biopsies throughout the disease course represent a feasible and safe tool that can be utilized to guide precision treatment and monitor the response in cancer cachexia research.

Enhancement of the biological activity of hydroxytyrosol through its oxidation by laccase from Trametes versicolor.

The laccase-catalyzed oxidation of hydroxytyrosol (HT) towards the formation of its bioactive oligomer derivatives was investigated. The biocatalytic oligomerization was catalyzed by laccase from Trametes versicolor in aqueous or various water-miscible organic solvents and deep eutectic solvent (DES)-based media. Mass Spectroscopy and Nuclear Magnetic Resonance were used for the characterization of the products. The solvent system used significantly affects the degree of HT oligomerization. The use of 50 % v/v methanol favored the production of the HT dimer, while other organic solvents as well as DESs led to the formation of hydroxytyrosol trimer and other oligomers. In vitro studies showed that the HT dimer exhibits 3- to 4-fold enhanced antibacterial activity against Gram-positive and Gram-negative bacteria compared to the parent compound. Moreover, the ability of HT dimer to inhibit the activity of soybean lipoxygenase and Candida rugosa lipase was 1.5-fold higher than HT, while molecular docking supported these results. Furthermore, HT dimer showed reduced cytotoxicity against HEK293 cells and exhibited a strong ability to inhibit ROS formation. The enhanced bioactivity of HT dimer indicates that this compound could be considered for use in cosmetics, skin-care products, and nutraceuticals.

PTEN Deregulation Mechanisms in Salivary Gland Carcinomas.

Among the tumour suppressor genes that affect critically cell functions and homeostasis, phosphatase and tensin homolog deleted in chromosome 10 (PTEN- gene locus: 10q21) regulates the PI3K/Akt/mTOR signalling pathway. PTEN is deleted, mutated or epigenetically hyper-methylated in a variety of human solid malignancies. Salivary gland carcinomas (SGCs) belong to the head and neck carcinomas (HNCs) super category of solid malignancies. Histo-pathologically, they demonstrate a significant diversity due to a variety of distinct and mixed subtypes. Genetically, they are characterized by a broad spectrum of gene and chromosomal imbalances. Referring specifically to suppressor genes, PTEN deregulation plays a critical role in signaling transduction in the corresponding SGC pre- and malignant epithelia modifying the response rates to potential targeted therapeutic strategies. In the current review, we explored the role of PTEN deregulation mechanisms that are involved in the onset and progression of SGCs.

Glioblastoma research on zebrafish xenograft models: a systematic review.

Glioblastoma (GBM) constitutes the most common primary brain tumor in adults. The challenges in GBM therapeutics have shed light on zebrafish used as a promising animal model for preclinical GBM xenograft studies without a standardized methodology. This systematic review aims to summarize the advances in zebrafish GBM xenografting, compare research protocols to pinpoint advantages and underlying limitations, and designate the predominant xenografting parameters. Based on the PRISMA checklist, we systematically searched PubMed, Scopus, and ZFIN using the keywords "glioblastoma," "xenotransplantation," and "zebrafish" for papers published from 2005 to 2022, available in English. 46 articles meeting the review criteria were examined for the zebrafish strain, cancer cell line, cell labeling technique, injected cell number, time and site of injection, and maintenance temperature. Our review designated that AB wild-type zebrafish, Casper transparent mutants, transgenic Tg(fli1:EGFP), or crossbreeding of these predominate among the zebrafish strains. Orthotopic transplantation is more commonly employed. A number of 50-100 cells injected at 48 h post-fertilization in high density and low infusion volume is considered as an effective xenografting approach. U87 cells are used for GBM angiogenesis studies, U251 for GBM proliferation studies, and patient-derived xenograft (PDX) to achieve clinical relevance. Gradual acclimatization to 32-33 °C can partly address the temperature differential between the zebrafish and the GBM cells. Zebrafish xenograft models constitute valuable tools for preclinical studies with clinical relevance regarding PDX. The GBM xenografting research requires modification based on the objective of each research team. Automation and further optimization of the protocol parameters could scale up the anticancer drug trials.

Cell replacement therapy with stem cells in multiple sclerosis, a systematic review.

Multiple sclerosis (MS) is a chronic inflammatory, autoimmune, and neurodegenerative disease of the central nervous system (CNS), characterized by demyelination and axonal loss. It is induced by attack of autoreactive lymphocytes on the myelin sheath and endogenous remyelination failure, eventually leading to accumulation of neurological disability. Disease-modifying agents can successfully address inflammatory relapses, but have low efficacy in progressive forms of MS, and cannot stop the progressive neurodegenerative process. Thus, the stem cell replacement therapy approach, which aims to overcome CNS cell loss and remyelination failure, is considered a promising alternative treatment. Although the mechanisms behind the beneficial effects of stem cell transplantation are not yet fully understood, neurotrophic support, immunomodulation, and cell replacement appear to play an important role, leading to a multifaceted fight against the pathology of the disease. The present systematic review is focusing on the efficacy of stem cells to migrate at the lesion sites of the CNS and develop functional oligodendrocytes remyelinating axons. While most studies confirm the improvement of neurological deficits after the administration of different stem cell types, many critical issues need to be clarified before they can be efficiently introduced into clinical practice.

Heat Shock Proteins' Expression Profiles in Odontogenic Ameloblastomas and Cysts.

Tumors and cysts with odontogenic origin represent a family of lesions with specific histo-genetic and clinical characteristics. Among them, ameloblastomas are common benign neoplasms, predominantly detected in the anatomic areas of the jaws and also in the mandible and maxilla. Although they are characterized by a slow and stable growing pattern, a subset of them shows a tendency for local tissue invasiveness and partially increased recurrence rates after surgical excision. Furthermore, heat shock proteins (HSPs) are potentially implicated in ameloblastoma onset and progression. HSPs regulate the folding and refolding of proteins and are induced in response to oxidative stress. They are crucial members of the chaperone intracellular system and are categorized based on their molecular weight (i.e., HSP27, HSP60, HSP70, HSP90). In the current review, we describe HSPs origin and function, focusing on their deregulation mechanisms and impact predominantly on ameloblastomas and also on inflammatory and developmental odontogenic cystic lesions.

Effect of Highly Hydrophilic Superparamagnetic Iron Oxide Nanoparticles on Macrophage Function and Survival.

Superparamagnetic iron oxide nanoparticles (SPIONs) have garnered significant attention in the medical sector due to their exceptional superparamagnetic properties and reliable tracking capabilities. In this study, we investigated the immunotoxicity of SPIONs with a modified surface to enhance hydrophilicity and prevent aggregate formation. The synthesized SPIONs exhibited a remarkably small size (~4 nm) and underwent surface modification using a novel "haircut" reaction strategy. Experiments were conducted in vitro using a human monocytic cell line (THP-1). SPIONs induced dose-dependent toxicity to THP-1 cells, potentially by generating ROS and initiating the apoptotic pathway in the cells. Concentrations up to 10 µg/mL did not affect the expression of Nrf2, HO-1, NF-κB, or TLR-4 proteins. The results of the present study demonstrated that highly hydrophilic SPIONs were highly toxic to immune cells; however, they did not activate pathways of inflammation and immune response. Further investigation into the mechanisms of cytotoxicity is warranted to develop a synthetic approach for producing effective, highly hydrophilic SPIONs with little to no side effects.

Impact of Amplified Oncogenes on Salivary Gland Carcinomas.

In normal epithelia, proto-oncogenes regulate critical intra- or intercellular functions, including cell growth and proliferation, apoptosis, and signaling transduction from the cell periphery (extracellular space) to the nucleus mediated by different pathways. Oncogenes are the mutated or amplified forms of the corresponding proto-oncogenes that are crucially involved in cell neoplastic and malignant transformation during carcinogenesis. Salivary gland carcinomas (SGCs) demonstrate a variety of histogenetic types. They are characterized by a broad spectrum of chromosomal and gene alterations. In particular, amplifications in specific genes [human epidermal growth factor receptor 2 (HER2), human epidermal growth factor receptor 4 (HER4), epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), Mouse double minute 2 homolog (MDM2), androgen receptor (AR), programmed death (ligand 1 (PD-L1), neurogenic differentiation factor 2 (NEUROD2), phosphatidylinositol 3,4,5-trisphosphate-dependent RAC exchanger 1 protein (PREX1), cyclin-dependent kinase4/6 (CDK4/6), proline-rich acidic protein 1 (PRAP1), kell antigen system (KEL), glutamate receptor subunit epsilon 2 (GRIN2D), Ewing sarcoma RNA-binding protein 1 (EWSR1), MYC proto-oncogene (MYC)] combined or not with chromosomal numerical imbalances (aneuploidy/ polysomy/monosomy) form different genetic signatures affecting the response to monoclonal antibody-based, oncologicaly targeted regimens. Different SGC histotypes demonstrate specific combinations of mutated/amplified genes that modify their clinicohistological features. In the current molecular review, we present the most important amplified oncogenes and their impact on the biological behavior of SGCS.

Mutational Signatures in Salivary Gland Carcinomas.

Salivary gland carcinomas belong to the head and neck carcinoma super category of malignancies. They are characterized by histopathological diversity and comprise a variety of entities and subtypes. Mucoepidermoid, adenoid cystic and salivary duct carcinomas represent the most prominent malignancies. Concerning their corresponding genetic background, a broad spectrum of gene and chromosomal imbalances has been detected. Point mutations and deletions, amplifications and translocations, combined or not with chromosomal aneuploidy/polysomy/monosomy, create a landscape of specific genetic signatures that affect the biological behavior of these tumors and modify response rates to potential targeted therapeutic strategies. In the current molecular review, we focused on the categorization and description of the most important mutational signatures in salivary gland carcinomas.

Calpain-mediated Mechanoptosis in Breast Adenocarcinoma.

Calpains belong to a family of important calcium-dependent cysteine proteases. They are involved in intracellular processes including cytoskeleton disorganization and substrate proteolysis. They also enhance apoptosis and cell to cell adhesion. Calpains demonstrate also a mechanosensory function in neoplastic and malignant cells due to their implication in mechanoptosis. This is a specific type of apoptotic death induced by strong external mechanical stimuli. Anti-cytoskeleton rigidity inhibition strategies based on calpain induction lead to increased apoptosis of tumor transformed cells. Elevated intracellular calcium concentration mediated by specific receptors and channels activates calpains. In the current molecular review, we explored the role of calpains in calcium-dependent signa transduction pathways in breast adenocarcinoma in conjunction with novel agents that activate their important anti-tumor functions.

Impact of CD34-dependent Micro Vessel Density on Periapical Odontogenic Cysts.

BACKGROUND/AIM: Odontogenic cysts belong to a type of lesions with endodontic origin that in some cases mimic even aggressive odontogenic tumors sharing with them similar radiographic features. Periapical cysts (PCs) belong to the inflammatory odontogenic cysts sub-category and rarely squamous cell carcinoma arises from their hyperplastic/ dysplastic epithelia. This study aimed to explore the impact of cluster differentiation 34 (CD34) protein expression combined with micro vessel density (MVD) on PCs. MATERIALS AND METHODS: Forty-eight (n=48) archival, formalin-fixed, and paraffin-embedded PC tissue specimens were included in the study. Immunohistochemistry (IHC) was performed in the corresponding tissue sections using an anti- CD34 antibody. CD34 expression levels and also MVD in the examined cases were measured by implementing a digital image analysis protocol. RESULTS: CD34 over-expression (moderate to high staining intensity levels) were detected in 29/48 (60.4%) cases, whereas the rest of them (19/48-39.6%) were characterized by low levels of expression. Extended MVD was identified in 26/48 (50.1%) cases correlated with CD34 over-expression, epithelial hyperplasia (p-value=0.001), and marginally with inflammatory infiltration level in the examined lesions (p-value=0.056). CONCLUSION: CD34 over-expression combined with increased MVD is associated with a neoplastic-like (hyperplastic) phenotype in PCs as a result of increased neo-angiogenic activity. These histopathological characteristics rarely form an eligible substrate for squamous cell carcinoma onset in untended cases.

DNA Mismatch Repair System Imbalances in Breast Adenocarcinoma.

DNA mismatch repair system (MMR) is considered a leading genetic mechanism in stabilizing DNA structure and maintaining its function. DNA MMR is a highly conserved system in bacteria, prokaryotic, and eukaryotic cells, and provides the highest protection to DNA by repairing micro-structural alterations. DNA MMR proteins are involved in the detection and repair of intra-nucleotide base-to-base errors inside the complementary DNA strand recognizing the recently synthesized strand from the parental template. During DNA replication, a spectrum of errors including base insertion, deletion, and miss-incorporation negatively affect the molecule's structure and its functional stability. A broad spectrum of genomic alterations such as promoter hyper methylation, mutation, and loss of heterozygosity (LOH) in MMR genes including predominantly hMLH1, hMSH2, hMSH3, hMSH6, hPMS1, and hPMS2 lead to their loss of base-to-base error repairing procedure. Microsatellite instability (MSI) refers to the DNA MMR gene alterations that are observed in a variety of malignancies of different histological origins. In the current review, we present the role of DNA MMR deficiency in breast adenocarcinoma, a leading cancer-based cause of death in females worldwide.

Anti-EGFR/BRAF-Tyrosine Kinase Inhibitors in Thyroid Carcinoma.

Alterations in significant genes located on chromosome 7 - including epidermal growth factor receptor (EGFR) and also v-Raf murine sarcoma viral oncogene homolog B (BRAF) as a mitogen-activated protein kinase (MAPK)  - combined or not with numerical imbalances of the whole chromosome (aneuploidy-polysomy) are crucial genetic events involved in the development and progression of malignancies. Identification of EGFR/BRAF-dependent specific somatic mutations and other mechanisms of deregulation (i.e., amplification) is critical for applying targeted therapeutic approaches [tyrosine kinase inhibitors (TKIs] or monoclonal antibodies (mAbs). Thyroid carcinoma is a specific pathological entity characterized by a variety of histological sub-types. Follicular thyroid carcinoma (FTC), papillary thyroid carcinoma (PTC), medullary thyroid carcinoma (MTC), and anaplastic thyroid carcinoma (ATC) represent its main sub-types. In the current review, we explore the role of EGFR/BRAF alterations in thyroid carcinoma in conjunction with the corresponding anti-EGFR/BRAF TKI-based novel therapeutic strategies for patients with specific genetic signatures.

The Landscape of Single Nucleotide Polymorphisms in Papillary Thyroid Carcinoma.

Thyroid carcinoma represents a leading malignancy among those derived from human endocrine systems. It comprises a variety of different histological subtypes, including mainly papillary carcinoma, follicular carcinoma, anaplastic carcinoma, and medullar carcinoma. A broad spectrum of genetic imbalances, comprising gross chromosomal (polysomy/aneuploidy) and specific gene (mutations, amplifications, deletions) alterations, has been reported. Interestingly, the role of isolated, specific gene polymorphisms, especially of the single nucleotide polymorphism (SNP) type, in thyroid carcinoma is under investigation. SNPs are the most common genetic variations in the genome. The current molecular review focuses on the impact of specific SNPs on the biological behavior of papillary thyroid carcinoma in their carriers.

Epigenetic Mechanisms in Breast Adenocarcinoma: Novel DNA Methylation Patterns.

Breast adenocarcinoma is a leading cause of death in females worldwide. A broad spectrum of genetic and epigenetic alterations has been already identified and reported in millions of examined cancerous substrates, evidence of a high-level genomic heterogeneity that characterizes these malignancies. Concerning epigenetic changes and imbalances that critically affect progression and prognosis in the corresponding patients, DNA methylation, histone modifications (acetylation), micro-RNAs (miRs) alterations and chromatin re-organization represent the main mechanisms. Referring to DNA methylation, promoter hyper-hypo methylation in critical tumour suppressor and oncogenes is implicated in normal epithelia transformation to their neoplastic and finally malignant cyto-phenotypes. The current review is focused on the different methylation patterns and mechanisms detected in breast adenocarcinoma and their impact on the corresponding groups of patient response to specific chemotherapeutic regimens and life span prognosis.

c-FOS Expression Analysis in Pterygia Cell Spot Arrays.

BACKGROUND/AIM: Mechanisms of c-FOS activation in the onset and progression of pterygia remain under investigation. This study aimed to comparatively analyze c-FOS proto-oncogene expression levels in neoplastic pterygia and normal epithelia. MATERIALS AND METHODS: We used a liquid-based cytology assay on thirty (n=30) pterygia cell populations and normal epithelia (n=10) extracted by a smooth scraping of conjunctiva epithelia. Applying a cell spot-based technique, we constructed five (n=5) slides, each containing eight (n=8) cell spots. A modified immune-cytochemistry (ICC) assay for c-FOS protein was used. Additionally, digital image analysis was implemented to calculate c-FOS immunostaining intensity levels. RESULTS: High staining intensity levels of c-FOS were detected in 12/30 (40%), whereas the rest 18/30 (60%) demonstrated moderate expression. c-FOS levels were statistically significantly higher in the pterygia compared to control tissues (p=0.001). c-FOS levels in the pterygia were not associated with the sex of patients (p=0.678), the presence of recurrent lesion (p=0.390) or the location of the lesion (p=0.158). The levels of c-FOS, however, were marginally significantly affected by the morphology of the pterygia (p=0.005). More precisely, the c-FOS levels were significantly higher in pterygia with a fleshy morphology. CONCLUSION: c-FOS over-expression is observed frequently in pterygia. It seems to be critically involved in the molecular mechanism of the lesion by its over-expression affecting partially their morphological features. Cell spot liquid - based array analysis is an innovative, easy to implement technique for simultaneously evaluating a broad spectrum of molecules in multiple specimens on the same slide.

P53 Suppressor Gene Tissue Microarray-based Protein Expression Analysis in Meningiomas.

BACKGROUND/AIM: Meningiomas represent the main intracranial primary central nervous system (CNS) tumour in adults worldwide. Oncogenes' over-activation combined with suppressor genes' silencing affect negatively the biological behavior of these neoplasms. This study aimed to explore the impact of p53 suppressor gene expression in meningiomas' clinic-pathological features based on a combination of sophisticated techniques. MATERIALS AND METHODS: Fifty (n=50) meningiomas were included in the study, comprising a broad spectrum of histopathological subtypes. An immunohistochemistry assay was applied on tissue microarray cores followed by digital image analysis. RESULTS: p53 protein over-expression (high staining intensity levels) was observed in 27/50 (54%) cases, whereas the rest (23/50-/46%) demonstrated moderate to low levels of the protein. p53 over-expression was statistically significantly correlated to the mitotic index of the examined cases (p-value=0.001). Interestingly, the atypical/anaplastic group of histotypes demonstrated the strongest p53 expression rates compared to the others (p-value=0.001). CONCLUSION: p53 overexpression is observed in a broad spectrum of meningiomas. High expression levels lead to an aggressive biological behavior of the malignancy (combined with increased mitotic rates), especially in atypical and anaplastic sub-types that also have a high recurrence rate.