Clinical impact of the methotrexate resistance-associated genes C-MYC and dihydrofolate reductase (DHFR) in high-grade osteosarcoma

Single nucleotide variants in nuclear pore complex disassembly pathway associated with poor survival in osteosarcoma

Introduction

The bone tumor, osteosarcoma, remains challenging to treat in children and young adults, especially when patients present with metastatic disease. Developing new therapies based on genomic data from sequencing projects has proven difficult given the lack of recurrent genetic lesions across tumors. MYC overexpression has been associated with poor outcomes in osteosarcoma. However, other genomic markers of disease severity are lacking.

Materials and Methods

We utilized whole genome sequencing of 106 tumors and matched normal controls in order to define genomic characteristics that correlate with overall survival. Single nucleotide variants were overlaid onto annotated molecular pathways in order to define aberrant pathway signatures specific to aggressive osteosarcoma. Additionally, we calculated differential gene expression in a subsample of 71 tumors. Differentially expressed genes were then queried for known MYC-responsive genes.

Results

Molecular pathways specific to nuclear pore complex disassembly (NPCD) show significant correlation with poor overall survival in osteosarcoma when mutations were present. Genes involved in immune response and immune regulation are enriched in the differential expression analysis of samples with and without NPCD pathway aberrations. Furthermore, neither MYC nor MYC-responsive genes show differential expression between NPCD-aberrant and non-aberrant groups. The NPCD pathway mutations are dominated by regulatory region variants rather than protein-altering mutations, suggesting that dysregulation of genetic regulatory networks may be the underlying mechanism for their relation to osteosarcoma phenotype.

Discussion

Overall survival is significantly worse in patients whose tumors show aberrations in the NPCD pathway. Moreover, this difference in survival is not driven by MYC-overexpression, suggesting a novel mechanism for some aggressive osteosarcomas. These findings add light to the evolving understanding of the drivers of osteosarcoma and may aid in the search for new treatments based on patient-specific genetic data.

In vivo therapy of osteosarcoma using anion transporters-based supramolecular drugs

BACKGROUND

Osteosarcoma represents a serious clinical challenge due to its widespread genomic alterations, tendency for drug resistance and distant metastasis. New treatment methods are urgently needed to address those treatment difficulties in osteosarcoma to improve patient prognoses. In recent years, small-molecule based anion transporter have emerged as innovative and promising therapeutic compound with various biomedical applications. However, due to a lack of efficient delivery methods, using ion transporters as therapeutic drugs in vivo remains a major challenge.

RESULT

Herein, we developed self-assembled supramolecular drugs based on small-molecule anion transporters, which exhibited potent therapeutic effect towards osteosarcoma both in vitro and in vivo. The anion transporters can disrupt intracellular ion homeostasis, inhibit proliferation, migration, epithelial-mesenchymal transition process, and lead to osteosarcoma cell death. RNA sequencing, western blot and flow cytometry indicated reprogramming of HOS cells and induced cell death through multiple pathways. These pathways included activation of endoplasmic reticulum stress, autophagy, apoptosis and cell cycle arrest, which avoided the development of drug resistance in osteosarcoma cells. Functionalized with osteosarcoma targeting peptide, the assembled supramolecular drug showed excellent targeted anticancer therapy against subcutaneous xenograft tumor and lung metastasis models. Besides good tumor targeting capability and anti-drug resistance, the efficacy of the assembly was also attributed to its ability to regulate the tumor immune microenvironment in vivo.

CONCLUSIONS

In summary, we have demonstrated for the first time that small-molecule anion transporters are capable of killing osteosarcoma cells through multiple pathways. The assemblies, OTP-BP-L, show excellent targeting and therapeutic effect towards osteosarcoma tumors. Furthermore, the supramolecular drug shows a strong ability to regulate the tumor immune microenvironment in vivo. This work not only demonstrated the biomedical value of small-molecule anion transporters in vivo, but also provided an innovative approach for the treatment of osteosarcoma.

Subclonal Somatic Copy-Number Alterations Emerge and Dominate in Recurrent Osteosarcoma

Multiple large-scale genomic profiling efforts have been undertaken in osteosarcoma to define the genomic drivers of tumorigenesis, therapeutic response, and disease recurrence. The spatial and temporal intratumor heterogeneity could also play a role in promoting tumor growth and treatment resistance. We conducted longitudinal whole-genome sequencing of 37 tumor samples from 8 patients with relapsed or refractory osteosarcoma. Each patient had at least one sample from a primary site and a metastatic or relapse site. Subclonal copy-number alterations were identified in all patients except one. In 5 patients, subclones from the primary tumor emerged and dominated at subsequent relapses. MYC gain/amplification was enriched in the treatment-resistant clones in 6 of 7 patients with multiple clones. Amplifications in other potential driver genes, such as CCNE1, RAD21, VEGFA, and IGF1R, were also observed in the resistant copy-number clones. A chromosomal duplication timing analysis revealed that complex genomic rearrangements typically occurred prior to diagnosis, supporting a macroevolutionary model of evolution, where a large number of genomic aberrations are acquired over a short period of time followed by clonal selection, as opposed to ongoing evolution. A mutational signature analysis of recurrent tumors revealed that homologous repair deficiency (HRD)-related SBS3 increases at each time point in patients with recurrent disease, suggesting that HRD continues to be an active mutagenic process after diagnosis. Overall, by examining the clonal relationships between temporally and spatially separated samples from patients with relapsed/refractory osteosarcoma, this study sheds light on the intratumor heterogeneity and potential drivers of treatment resistance in this disease.

SIGNIFICANCE

The chemoresistant population in recurrent osteosarcoma is subclonal at diagnosis, emerges at the time of primary resection due to selective pressure from neoadjuvant chemotherapy, and is characterized by unique oncogenic amplifications.

Subclonal somatic copy number alterations emerge and dominate in recurrent osteosarcoma

Multiple large-scale tumor genomic profiling efforts have been undertaken in osteosarcoma, however, little is known about the spatial and temporal intratumor heterogeneity and how it may drive treatment resistance. We performed whole-genome sequencing of 37 tumor samples from eight patients with relapsed or refractory osteosarcoma. Each patient had at least one sample from a primary site and a metastatic or relapse site. We identified subclonal copy number alterations in all but one patient. We observed that in five patients, a subclonal copy number clone from the primary tumor emerged and dominated at subsequent relapses. MYC gain/amplification was enriched in the treatment-resistant clone in 6 out of 7 patients with more than one clone. Amplifications in other potential driver genes, such as CCNE1, RAD21, VEGFA, and IGF1R, were also observed in the resistant copy number clones. Our study sheds light on intratumor heterogeneity and the potential drivers of treatment resistance in osteosarcoma.

The strategy and clinical relevance of in vitro models of MAP resistance in osteosarcoma: a systematic review

Over the last 40 years osteosarcoma (OS) survival has stagnated with patients commonly resistant to neoadjuvant MAP chemotherapy involving high dose methotrexate, adriamycin (doxorubicin) and platinum (cisplatin). Due to the rarity of OS, the generation of relevant cell models as tools for drug discovery is paramount to tackling this issue. Four literature databases were systematically searched using pre-determined search terms to identify MAP resistant OS cell lines and patients. Drug exposure strategies used to develop cell models of resistance and the impact of these on the differential expression of resistance associated genes, proteins and non-coding RNAs are reported. A comparison to clinical studies in relation to chemotherapy response, relapse and metastasis was then made. The search retrieved 1891 papers of which 52 were relevant. Commonly, cell lines were derived from Caucasian patients with epithelial or fibroblastic subtypes. The strategy for model development varied with most opting for continuous over pulsed chemotherapy exposure. A diverse resistance level was observed between models (2.2-338 fold) with 63% of models exceeding clinically reported resistance levels which may affect the expression of chemoresistance factors. In vitro p-glycoprotein overexpression is a key resistance mechanism; however, from the available literature to date this does not translate to innate resistance in patients. The selection of models with a lower fold resistance may better reflect the clinical situation. A comparison of standardised strategies in models and variants should be performed to determine their impact on resistance markers. Clinical studies are required to determine the impact of resistance markers identified in vitro in poor responders to MAP treatment, specifically with respect to innate and acquired resistance. A shift from seeking disputed and undruggable mechanisms to clinically relevant resistance mechanisms may identify key resistance markers that can be targeted for patient benefit after a 40-year wait.

Comprehensive genomic profiling of a unique liposarcoma arising in a patient with Li-Fraumeni syndrome and the novel detection of c-myc amplification: a case report

BACKGROUND

Germline TP53 mutations have been frequently reported in patients with Li-Fraumeni syndrome (LFS), resulting in a predisposition to various malignancies. Mutations other than germline TP53 mutations can also cause LFS-associated malignancies, but their details remain unclear. We describe a novel c-myc amplification in a unique liposarcoma in a patient with LFS.

CASE PRESENTATION

A female patient with LFS developed breast cancer twice at the age of thirty; both were invasive ductal carcinomas harboring HER2 amplifications. Computed tomography revealed an anterior mediastinal mass, which was surgically resected. Histological analysis revealed three different lesions corresponding to myxoid liposarcoma-, pleomorphic liposarcoma-, and well-differentiated liposarcoma-like lesions. Fluorescence in-situ hybridization (FISH) analysis did not detect MDM2 amplification, Rb1 deletion, break apart signals of EWS, FUS, DDIT3, or c-myc, or c-myc-IGH fusion signals, but it did detect more c-myc signals. Further FISH analysis and comprehensive genomic profiling revealed c-myc amplification. We considered two differential diagnoses, dedifferentiated liposarcoma lacking MDM2 amplification and myxoid pleomorphic liposarcoma (MPLPS), and determined that this case is most likely MPLPS. However, definite diagnosis could not be made because a clear-cut differentiation of the case from liposarcomas was not possible.

CONCLUSIONS

A previous study demonstrated that c-myc amplification could not be detected in various liposarcomas, but the present unique liposarcoma showed c-myc amplification, so the c-myc amplification may indicate that the present liposarcoma is an LFS-related tumor. The present case further clarifies the pathological features of MPLPS and LFS-related liposarcomas by broadening their histopathological and genetic diversities.

Methotrexate-Induced Liver Injury Is Associated with Oxidative Stress, Impaired Mitochondrial Respiration, and Endoplasmic Reticulum Stress In Vitro

Low-dose methotrexate (MTX) is a standard therapy for rheumatoid arthritis due to its low cost and efficacy. Despite these benefits, MTX has been reported to cause chronic drug-induced liver injury, namely liver fibrosis. The hallmark of liver fibrosis is excessive scarring of liver tissue, triggered by hepatocellular injury and subsequent activation of hepatic stellate cells (HSCs). However, little is known about the precise mechanisms through which MTX causes hepatocellular damage and activates HSCs. Here, we investigated the mechanisms leading to hepatocyte injury in HepaRG and used immortalized stellate cells (hTERT-HSC) to elucidate the mechanisms leading to HSC activation by exposing mono- and co-cultures of HepaRG and hTERT-HSC to MTX. The results showed that at least two mechanisms are involved in MTX-induced toxicity in HepaRG: (i) oxidative stress through depletion of glutathione (GSH) and (ii) impairment of cellular respiration in a GSH-independent manner. Furthermore, we measured increased levels of endoplasmic reticulum (ER) stress in activated HSC following MTX treatment. In conclusion, we established a human-relevant in vitro model to gain mechanistical insights into MTX-induced hepatotoxicity, linked oxidative stress in HepaRG to a GSH-dependent and -independent pathway, and hypothesize that not only oxidative stress in hepatocytes but also ER stress in HSCs contribute to MTX-induced activation of HSCs.

Integrated DNA Copy Number and Expression Profiling Identifies IGF1R as a Prognostic Biomarker in Pediatric Osteosarcoma

Osteosarcoma is a primary malignant bone tumor arising from bone-forming mesenchymal cells in children and adolescents. Despite efforts to understand the biology of the disease and identify novel therapeutics, the survival of osteosarcoma patients remains dismal. We have concurrently profiled the copy number and gene expression of 226 osteosarcoma samples as part of the Strategic Partnering to Evaluate Cancer Signatures (SPECS) initiative. Our results demonstrate the heterogeneous landscape of osteosarcoma in younger populations by showing the presence of genome-wide copy number abnormalities occurring both recurrently among samples and in a high frequency. Insulin growth factor receptor 1 (IGF1R) is a receptor tyrosine kinase which binds IGF1 and IGF2 to activate downstream pathways involved in cell apoptosis and proliferation. We identify prevalent amplification of IGF1R corresponding with increased gene expression in patients with poor survival outcomes. Our results substantiate previously tenuously associated copy number abnormalities identified in smaller datasets (13q34+, 20p13+, 4q35-, 20q13.33-), and indicate the significance of high fibroblast growth factor receptor 2 (FGFR2) expression in distinguishing patients with poor prognosis. FGFR2 is involved in cellular proliferation processes such as division, growth and angiogenesis. In summary, our findings demonstrate the prognostic significance of several genes associated with osteosarcoma pathogenesis.

Molecular profiling of osteosarcoma in children and adolescents from different age groups using a next-generation sequencing panel

Osteosarcoma (OS) is a malignant bone tumor, with a peak of incidence in the second decade of life and possibly associated with the presence of germline mutations. Besides, clinicians have pointed to a second, rarer group of patients that develops OS before 10 years old. Here we access, through next-generation sequencing (NGS) strategy, the genetic alterations present in OS and blood samples from patients diagnosed before and during the second decade of life. A custom NGS panel, designed for the main alterations described in childhood and adolescence neoplasms, named Oncomine Childhood Cancer Research Assay (OCCRA©), was used. Of all 84 OS samples investigated, 42 (50%) presented some somatic variant, with TP53, MYC, CDK4, RB1 and PDGFRA genes harboring the most observed genetic variants. MYC CNVs were more frequent in tumors from patients diagnosed before 10 years old (X²₁= 5.18, p = 0.023). Additionally, patients diagnosed during the second decade of life presented a higher percentage of somatic and germline variants. Germline variants in TP53 and RB1 were found in 5 of the 11 (45.5%) patients analyzed. Clinical variables and tumor histopathological characteristics were also collected and correlated with our molecular findings.

MYC amplifications are common events in childhood osteosarcoma

Osteosarcoma, the most common primary malignant tumour of bone, affects both children and adults. No fundamental biological differences between paediatric and adult osteosarcoma are known. Here, we apply multi-region whole-genome sequencing to an index case of a 4-year-old child whose aggressive tumour harboured high-level, focal amplifications of MYC and CCNE1 connected by translocations. We reanalysed copy number readouts of 258 cases of high-grade osteosarcoma from three different cohorts and identified a significant enrichment of focal MYC, but not CCNE1, amplifications in children. Furthermore, we identified four additional cases of MYC and CCNE1 coamplification, highlighting a rare driver event which warrants further investigation. Our findings indicate that amplification of the MYC oncogene is a major driver of childhood osteosarcoma, while CCNE1 appears recurrently amplified independent of age.

Recent Insights into Therapy Resistance in Osteosarcoma

Osteosarcoma, the most common bone malignancy of childhood, has been a challenge to treat and cure. Standard chemotherapy regimens work well for many patients, but there remain minimal options for patients with progressive or resistant disease, as clinical trials over recent decades have failed to significantly improve survival. A better understanding of therapy resistance is necessary to improve current treatments and design new strategies for future treatment options. In this review, we discuss known mechanisms and recent scientific advancements regarding osteosarcoma and its patterns of resistance against chemotherapy, radiation, and other newly-introduced therapeutics.

Osteosarcoma: A comprehensive review of management and treatment strategies

Osteosarcoma, a bone cancer usually seen in children and young adults, is generally a high-grade malignancy presented by extreme metastases to the lungs. Osteosarcoma has a tendency for appearing in bones with rapid growth rate. The etiology of osteosarcoma is multifaceted and poorly understood. A molecular consideration of this disease will lead to a directed tumor treatment. The present treatment for osteosarcoma comprises of an arrangement of systemic chemotherapy and wide surgical resection. Survival rate is increased by the progress of destructive systemic chemotherapies. So, the development of new treatment approaches for metastatic osteosarcoma is essential. Immunomodulation has been used in clinical settings. Through targeting surface antigens expressed on tumor cells, particular antibodies and exploitation of cellular immunotherapy against sarcomas have been confirmed to be effective as cancer therapeutics. In this article, we have reviewed epidemiology, etiology, pathogenesis, diagnosis, and treatment of osteosarcoma and we have focused on different methods of immunotherapy including vaccines, cell-based immunotherapy, cytokines, and monoclonal antibodies.

Prospects for the involvement of cancer stem cells in the pathogenesis of osteosarcoma

Osteosarcoma (OS) is one of the most common bone tumors in children and adolescents that cause a high rate of mortality in this age group and tends to be metastatic, in spite of chemotherapy and surgery. The main reason for this can be returned to a small group of malignant cells called cancer stem cells (CSCs). OS-CSCs play a key role in the resistance to treatment and relapse and metastasis through self-renewal and differentiation abilities. In this review, we intend to go through the different aspects of this malignant disease, including the cancer stem cell-phenotype, methods for isolating CSCs, signaling pathways, and molecular markers in this disease, and drugs showing resistance in treatment efforts of OS.

Aberrant Expression of Folate Metabolism Enzymes and Its Diagnosis and Survival Prediction in Ovarian Carcinoma

This study was to validate changes in the levels of folate receptor-α (FOLR1), dihydrofolate reductase (DHFR), and methionine synthase reductase (MTRR) in the tissue of OC patients. The expression of FOLR1, DHFR, and MTRR was evaluated in 80 cases of primary OC, 50 cases of benign ovarian tumors, and 30 normal ovarian tissues. Associations between protein expression and clinicopathological characters were assessed, and diagnostic and prognostic evaluation of FOLR1, DHFR, and MTRR was performed. Results showed that upregulated FOLR1 and MTRR and downregulated DHFR were detected in OC. Patients with abnormality of FOLR1, DHFR, and MTRR tend to have a higher percentage of platinum resistance. Moreover, the areas under receiver operating characteristic curves (AUCs-ROC) for FOLR1, DHFR, and MTRR were 0.723, 0.717, and 0.714, respectively. The combination of FOLR1, DHFR, and MTRR could produce an area of 0.864 under the receiver-operating characteristic curve in distinguishing platinum-resistant patients from platinum-sensitive patients (P < 0.0001). Correlations were present between the expression of FOLR1, DHFR, and MTRR. Furthermore, Kaplan-Meier curves indicated that the patients with overexpressed MTRR had a poorer overall survival time compared to those with low expression (P < 0.05). Thus, folate metabolic enzymes could provide a potential promising biomarker for diagnosis platinum-resistant in OC.

Insulin/IGF-1R, SIRT1, and FOXOs Pathways-An Intriguing Interaction Platform for Bone and Osteosarcoma

Aging is a substantial risk factor for the development of osteoarthritis (OA) and, probably, an essential substrate for the development of neoplastic disease of the bone, such as osteosarcoma, which is the most common malignant mesenchymal primary bone tumor. Genetic studies have established that the insulin/insulin-like growth factor 1 (IGF-1)/phosphatidylinositol-3 kinase (PI3K)/AKT (Protein Kinase B) signal transduction pathway is involved across species, including nematodes, fruit flies, and mammals. SIRT1, a phylogenetically-conserved family of deacetylases, seems to play pleiotropic effects in epithelial malignancies of the liver and interact with the IGF-1/PI3K/AKT signal transduction pathway. Some of the most critical processes in degenerative conditions may indeed include the insulin/IGF1R and SIRT1 signaling pathways as well as some specific transcription factors. The Forkhead box O (FOXO) transcription factors (FOXOs) control diverse cellular functions, such as metabolism, longevity, and cell death. FOXOs play a critical role in the IGF-1/PI3K/AKT signal transduction pathway. FOXOs can indeed be modulated to reduce age-related diseases. FOXOs have advantageous inhibitory effects on fibroblast and myofibroblast activation, which are accompanied by a subsequent excessive production of extracellular matrix. FOXOs can block or decrease the fibrosis levels in numerous organs. Previously, we observed a correlation between nuclear FOXO3 and high caspase-8 expression, which induces cellular apoptosis in response to harmful external stimuli. In this perspective, we emphasize the current advances and interactions involving the insulin/IGF1R, SIRT1, and FOXOs pathways in the bone and osteosarcoma for a better understanding of the mechanisms potentially underpinning tissue degeneration and tumorigenesis.

Identification and analysis of key genes in osteosarcoma using bioinformatics

Osteosarcoma (OS) is an invasive malignant neoplasm of the bones. The present study identified and analyzed key genes associated with OS. Expression profiling of the dataset GSE49003, which included 6 metastatic and 6 non-metastatic OS cell lines and was obtained from the Gene Expression Omnibus, was performed. Following data preprocessing, the differentially expressed genes (DEGs) were selected using the limma package in R. Subsequently, bidirectional hierarchical clustering using the pheatmap package in R and an unpaired Students' t-test was performed for the DEGs. Based on the Search Tool for the Retrieval of Interacting Genes database and Cytoscape software, a protein-protein interaction (PPI) network for the DEGs was constructed. Using Database for Annotation, Visualization and Integrated Discovery software and the Kyoto Encyclopedia of Genes and Genomes Orthology Based Annotation System server, functional and pathway enrichment analyses were performed for the DEGs corresponding to the proteins of the network. In addition, the transcription factors (TFs) and CpG islands of the gene promoter were searched for using the TRANSFAC database and CpG Island Searcher software, respectively. A total of 323 DEGs were identified between the metastatic and non-metastatic samples. In the PPI network, upregulated epidermal growth factor receptor (EGFR) exhibits a high degree and was therefore highly interconnected with other proteins. Enrichment analysis revealed that EGFR was enriched in cytoskeleton organization, organic substance response and the signaling pathway of focal adhesion. The TFs early growth response 1, nuclear factor-κB complex subunits, peroxisome proliferator activated receptor α, signal transducer and activator of transcription 3 and MYC proto-oncogene were identified in the EGFR promoter region. Furthermore, multiple CpG islands, starting from the 400 bp of the EGFR promoter sequence, were predicted. Methylated modification of the CpG islands in the EGFR promoter may help to regulate EGFR expression. The TFs identified in the EGFR promoter may function in the progression of OS.

Pharmacogenomics of genes involved in antifolate drug response and toxicity in osteosarcoma

INTRODUCTION

Antifolates are structural analogs of folates, which have been used as antitumor drugs for more than 60 years. The antifolate drug most commonly used for treating human tumors is methotrexate (MTX), which is utilized widely in first-line treatment protocols of high-grade osteosarcoma (HGOS). In addition to MTX, two other antifolates, trimetrexate and pemetrexed, have been tested in clinical settings for second-line treatment of recurrent HGOS with patients unfortunately showing modest activity. Areas covered: There is clinical evidence which suggsest that, like other chemotherapeutic agents, not all HGOS patients are equally responsive to antifolates and do not have the same susceptibility to experience adverse drug-related toxicities. Here, we summarize the pharmacogenomic information reported so far for genes involved in antifolate metabolism and transport and in MTX-related toxicity in HGOS patients. Expert opinion: Identification and validation of genetic biomarkers that significantly impact clinical antifolate treatment response and related toxicity may provide the basis for a future treatment modulation based on the pharmacogenetic and pharmacogenomic features of HGOS patients.

Osteosarcoma: Cells-of-Origin, Cancer Stem Cells, and Targeted Therapies

Osteosarcoma (OS) is the most common type of primary solid tumor that develops in bone. Although standard chemotherapy has significantly improved long-term survival over the past few decades, the outcome for those patients with metastatic or recurrent OS remains dismally poor and, therefore, novel agents and treatment regimens are urgently required. A hypothesis to explain the resistance of OS to chemotherapy is the existence of drug resistant CSCs with progenitor properties that are responsible of tumor relapses and metastasis. These subpopulations of CSCs commonly emerge during tumor evolution from the cell-of-origin, which are the normal cells that acquire the first cancer-promoting mutations to initiate tumor formation. In OS, several cell types along the osteogenic lineage have been proposed as cell-of-origin. Both the cell-of-origin and their derived CSC subpopulations are highly influenced by environmental and epigenetic factors and, therefore, targeting the OS-CSC environment and niche is the rationale for many recently postulated therapies. Likewise, some strategies for targeting CSC-associated signaling pathways have already been tested in both preclinical and clinical settings. This review recapitulates current OS cell-of-origin models, the properties of the OS-CSC and its niche, and potential new therapies able to target OS-CSCs.

The pharmacogenomics of osteosarcoma

Osteosarcoma (OS), the most common malignant tumor of bone, is presently treated with multidrug neoadjuvant chemotherapy protocols, which allow to cure 60-65% of patients but also induce toxicity events that cannot be predicted or efficiently prevented. The identification and validation of pharmacogenomic biomarkers is, therefore, absolutely warranted to provide the bases for planning personalized treatments with the aim to increase the therapeutic benefits and to avoid or limit unnecessary toxicities. As several targeted therapies against molecular and immunological markers in OS are presently under clinical investigation, it may be speculated that some new agents for innovative treatments may emerge in the next years. However, the real improvement of therapeutic perspectives for OS is strictly connected to the identification of pharmacogenomic biomarkers that may stratify patients in responders or non-responders and identify those individuals with higher susceptibility to treatment-associated toxicity. This review provides an overview of the pharmacogenomic biomarkers identified so far in OS, which appear to be promising candidates for a translation to clinical practice, after further investigation and/or prospective validation.

Chemotherapy induces stemness in osteosarcoma cells through activation of Wnt/β-catenin signaling

Development of resistance represents a major drawback in osteosarcoma treatment, despite improvements in overall survival. Treatment failure and tumor progression have been attributed to pre-existing drug-resistant clones commonly assigned to a cancer stem-like phenotype. Evidence suggests that non stem-like cells, when submitted to certain microenvironmental stimuli, can acquire a stemness phenotype thereby strengthening their capacity to handle with stressful conditions. Here, using osteosarcoma cell lines and a mouse xenograft model, we show that exposure to conventional chemotherapeutics induces a phenotypic cell transition toward a stem-like phenotype. This associates with activation of Wnt/β-catenin signaling, up-regulation of pluripotency factors and detoxification systems (ABC transporters and Aldefluor activity) that ultimately leads to chemotherapy failure. Wnt/β-catenin inhibition combined with doxorubicin, in the MNNG-HOS cells, prevented the up-regulation of factors linked to transition into a stem-like state and can be envisaged as a way to overcome adaptive resistance. Finally, the analysis of the public R2 database, containing microarray data information from diverse osteosarcoma tissues, revealed a correlation between expression of stemness markers and a worse response to chemotherapy, which provides evidence for drug-induced phenotypic stem cell state transitions in osteosarcoma.

Loss of Runx2 sensitises osteosarcoma to chemotherapy-induced apoptosis

Background:

Osteosarcoma (OS) is the most common bone malignancy in the paediatric population, principally affecting adolescents and young adults. Minimal advancements in patient prognosis have been made over the past two decades because of the poor understanding of disease biology. Runx2, a critical transcription factor in bone development, is frequently amplified and overexpressed in OS. However, the molecular and biological consequences of Runx2 overexpression remain unclear.

Methods:

si/shRNA and overexpression technology to alter Runx2 levels in OS cells. In vitro assessment of doxorubicin (doxo)-induced apoptosis and in vivo chemosensitivity studies. Small-molecule inhibitor of c-Myc transcriptional activity was used to assess its role.

Results:

Loss of Runx2 sensitises cells to doxo-induced apoptosis both in vitro and in vivo. Furthermore, in conjunction with chemotherapy, decreasing Runx2 protein levels activates both the intrinsic and extrinsic apoptotic pathways. Transplanted tumour studies demonstrated that loss of endogenous Runx2 protein expression enhances caspase-3 cleavage and tumour necrosis in response to chemotherapy. Finally, upon doxo-treated Runx2 knockdown OS cells there was evidence of enhanced c-Myc expression and transcriptional activity. Inhibition of c-Myc under these conditions resulted in decreased activation of apoptosis, therefore insinuating a role for c-Myc in dox-induced activation of apoptotic pathways.

Conclusions:

Therefore, we have established a novel molecular mechanism by which Runx2 provides a chemoprotective role in OS, indicating that in conjunction to standard chemotherapy, targeting Runx2 may be a new therapeutic strategy for patients with OS.

ABCG2 Transporter Expression Impacts Group 3 Medulloblastoma Response to Chemotherapy

While a small number of plasma membrane ABC transporters can export chemotherapeutic drugs and confer drug resistance, it is unknown whether these transporters are expressed or functional in less therapeutically tractable cancers such as Group 3 (G3) medulloblastoma. Herein we show that among this class of drug transporters, only ABCG2 was expressed at highly increased levels in human G3 medulloblastoma and a mouse model of this disease. In the mouse model, Abcg2 protein was expressed at the plasma membrane where it functioned as expected on the basis of export of prototypical substrates. By screening ABC substrates against mouse G3 medulloblastoma tumorspheres in vitro, we found that Abcg2 inhibition could potentiate responses to the clinically used drug topotecan, producing a more than 9-fold suppression of cell proliferation. Extended studies in vivo in this model confirmed that Abcg2 inhibition was sufficient to enhance antiproliferative responses to topotecan, producing a significant survival advantage compared with subjects treated with topotecan alone. Our findings offer a preclinical proof of concept for blockade of ABCG2 transporter activity as a strategy to empower chemotherapeutic responses in G3 medulloblastoma.

BET inhibitors induce apoptosis through a MYC independent mechanism and synergise with CDK inhibitors to kill osteosarcoma cells

Osteosarcoma (OS) survival rates have plateaued in part due to a lack of new therapeutic options. Here we demonstrate that bromodomain inhibitors (BETi), JQ1, I-BET151, I-BET762, exert potent anti-tumour activity against primary and established OS cell lines, mediated by inhibition of BRD4. Strikingly, unlike previous observations in long-term established human OS cell lines, the antiproliferative activity of JQ1 in primary OS cells was driven by the induction of apoptosis, not cell cycle arrest. In further contrast, JQ1 activity in OS was mediated independently of MYC downregulation. We identified that JQ1 suppresses the transcription factor FOSL1 by displacement of BRD4 from its locus. Loss of FOSL1 phenocopied the antiproliferative effects of JQ1, identifying FOSL1 suppression as a potential novel therapeutic approach for OS. As a monotherapy JQ1 demonstrated significant anti-tumour activity in vivo in an OS graft model. Further, combinatorial treatment approaches showed that JQ1 increased the sensitivity of OS cells to doxorubicin and induced potent synergistic activity when rationally combined with CDK inhibitors. The greater level of activity achieved with the combination of BETi with CDK inhibitors demonstrates the efficacy of this combination therapy. Taken together, our studies show that BET inhibitors are a promising new therapeutic for OS.

The tumor-suppressive microRNA-135b targets c-myc in osteoscarcoma

Osteosarcoma is the most common primary tumor of the bone. It leads to many deaths because of its rapid proliferation and metastasis. Recent studies have shown that microRNAs are important gene regulators that are involved in various cancer-related processes. In this study, we found that miR-135b was down-regulated in both osteoscarcoma patient tumor tissues and osteoscarcoma cell lines in comparison to paired adjacent non-tumor bone tissue. We observed that a lower level of miR-135b was associated with metastasis. The ectopic expression of miR-135b markedly suppressed osteoscarcoma cell proliferation, migration, and invasion. Conversely, the inhibition of miR-135b expression dramatically accelerated cell proliferation, migration, and invasion. The forced expression of miR-135b in osteosarcoma cells resulted in a significant reduction in the protein level of c-Myc and repressed the activity of a luciferase reporter that contained the 3′-untranslated region of the c-Myc mRNA. These effects were abolished by the mutation of the predicted miR-135b-binding site, which indicates that c-Myc may be a miR-135b target gene. Moreover, the ectopic expression of c-Myc partially reversed the inhibition of cell proliferation and invasion that was caused by miR-135b. These data therefore suggest that miR-135b may function as a tumor suppressor to regulate osteosarcoma cell proliferation and invasion through a mechanism that targets the c-Myc oncogene. These findings indicate that miR-135b may play a role in the pathogenesis of osteosarcoma.

c-MYC-induced genomic instability

MYC dysregulation initiates a dynamic process of genomic instability that is linked to tumor initiation. Early studies using MYC-carrying retroviruses showed that these viruses were potent transforming agents. Cell culture models followed that addressed the role of MYC in transformation. With the advent of MYC transgenic mice, it became obvious that MYC deregulation alone was sufficient to initiate B-cell neoplasia in mice. More than 70% of all tumors have some form of c-MYC gene dysregulation, which affects gene regulation, microRNA expression profiles, large genomic amplifications, and the overall organization of the nucleus. These changes set the stage for the dynamic genomic rearrangements that are associated with cellular transformation.

Effects of combined c-myc and Bmi-1 siRNAs on the growth and chemosensitivity of MG-63 osteosarcoma cells

Osteosarcoma is the most common form of primary malignant bone tumor. Patients who are insensitive to chemotherapy treatment often have a poor prognosis. According to our previous study, recombinant adenovirus (Myc-AS) in combination with caffeine enhances the induction of apoptosis and the chemotherapeutic effects of cisplatin (CDDP) in MG-63 osteosarcoma cells. The present study aimed to investigate the combinational effects of the small interfering RNAs (siRNAs) c-myc and Bmi-1 on the growth and chemosensitivity of MG-63 osteosarcoma cells. The results indicated that the cell growth inhibition rates of MG-63 cells gradually increased with increasing concentrations of CDDP (P<0.05). This observation was consistent in the single and combined siRNA groups. At a concentration of 5.0 µg/ml CDDP, the growth inhibition rates were 53.3±5.2, 42.7±6.3 and 40.9±4.7% in the combined, c-myc and Bmi-1 siRNA groups, respectively. The cell growth inhibition rate in the combined siRNA group was higher than that observed in the two single siRNA groups (P<0.05). The cell apoptotic rate was 37.3±4.9% in the combined siRNA group, which was significantly higher than that observed in the c-myc (24.8±5.6%) and Bmi-1 siRNA groups (22.7±6.1%; P<0.05). These results suggest that the chemosensitivity of MG-63 cells to CDDP may be markedly enhanced in the siRNA combination group. A decrease in cell proliferation and increased cell apoptosis were also observed in the siRNA combination group. The present study may provide novel insights to further elucidate the pathogenesis and drug resistance mechanisms involved in osteosarcoma. It may also improve our understanding of the underlying mechanisms involved in chemotherapeutic sensitivity, and thus aid the development of future therapeutic strategies for the treatment of osteosarcoma.

Genetically engineered mouse models and human osteosarcoma

Osteosarcoma is the most common form of bone cancer. Pivotal insight into the genes involved in human osteosarcoma has been provided by the study of rare familial cancer predisposition syndromes. Three kindreds stand out as predisposing to the development of osteosarcoma: Li-Fraumeni syndrome, familial retinoblastoma and RecQ helicase disorders, which include Rothmund-Thomson Syndrome in particular. These disorders have highlighted the important roles of P53 and RB respectively, in the development of osteosarcoma. The association of OS with RECQL4 mutations is apparent but the relevance of this to OS is uncertain as mutations in RECQL4 are not found in sporadic OS. Application of the knowledge or mutations of P53 and RB in familial and sporadic OS has enabled the development of tractable, highly penetrant murine models of OS. These models share many of the cardinal features associated with human osteosarcoma including, importantly, a high incidence of spontaneous metastasis. The recent development of these models has been a significant advance for efforts to improve our understanding of the genetics of human OS and, more critically, to provide a high-throughput genetically modifiable platform for preclinical evaluation of new therapeutics.

Expression and significance of Kruppel-like factor 6 gene in osteosarcoma

PURPOSE

Osteosarcoma is primary malignant tumour of bone. Kruppel-like factor 6 (KLF6) is a tumor suppressor gene frequently inactivated in a number of human cancers and a ubiquitously expressed zinc-finger transcription factor. The present study aimed to first explore the relationship between the expression level of the KLF6 gene in osteosarcoma and the occurrence of bone tumours.

METHODS

KLF6 mRNA and protein expression levels in osteosarcoma and normal bone tissue were assayed by real-time quantitative PCR and immunohistochemistry. KLF6 mRNA and protein expression levels in osteosarcoma cells and normal osteoblasts were detected by semi-quantitative reverse transcription PCR and Western blotting, respectively.

RESULTS

Both the expression of KLF6 mRNA and protein in osteosarcoma cells and tissues were significantly lower than that in normal cells and tumour-adjacent tissues.

CONCLUSIONS

KLF6 is a putative tumor suppressor gene involved in osteosarcoma which can be used as a new therapeutic target and an important marker for early diagnosis and postoperative monitoring.

Orthopaedic research in italy: state of the art

The most significant results in experimental and clinical orthopaedic research in Italy within the last three years have been primarily in major congenital diseases, bone tumors, regenerative medicine, joint replacements, spine, tendons and ligaments. The data presented in the following discussion is comparable with leading international results, highlighting Italian orthopaedic research excellemce as well as its shortcomings.

How genetic variation affects patient response and outcome to therapy for psoriasis

Psoriasis is a prevalent chronic inflammatory condition that affects the skin. There are many treatments available for psoriasis but they are not universally effective and some have associated toxicities. Pharmacogenetics and pharmacogenomics explore the relationship between individual genetic variation and drug effect to allow targeted 'personalized' therapy for patients. There has been very limited pharmacogenetic research regarding psoriasis, with most limited to small retrospective case-control studies looking at single-nucleotide polymorphisms in candidate genes involved in drug pharmacokinetics. We review the pharmacogenetic investigation of treatments for psoriasis to date, including emerging pharmacogenomic studies. In addition, we discuss how such genetic data could be incorporated into routine clinical practice and future areas for development in this field.

Methotrexate for high-grade osteosarcoma in children and young adults

BACKGROUND

The majority of the currently used treatment protocols for osteosarcoma are based on a combination of doxorubicin, cisplatin, methotrexate (MTX) and/or ifosfamide, of which MTX seems to be one of the most active drugs. However, in the literature, this has not been unambiguously proven.

OBJECTIVES

To compare the effectiveness of treatment including MTX with treatment without MTX for children and young adults (up to 21 years) with primary high-grade osteosarcoma.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library, issue 4, 2010), MEDLINE (1966 to January 2011) and EMBASE (1980 to January 2011). In addition, we searched reference lists of relevant articles, conference proceedings and ongoing trials databases.

SELECTION CRITERIA

Randomised controlled trials (RCTs) or controlled clinical trials (CCTs) comparing the effectiveness of treatment including MTX with treatment without MTX in the treatment of paediatric high-grade osteosarcoma.

DATA COLLECTION AND ANALYSIS

Two reviewers independently performed the study selection. One reviewer performed the data extraction and quality assessment, which was checked by another reviewer.

MAIN RESULTS

We could not identify any studies in which the only difference between the treatment groups was the use of MTX.We did identify a RCT comparing MTX with cisplatin (n=30 children). The risk of bias in this study was difficult to assess due to a lack of reporting. Survival could not be evaluated, but no evidence of a significant difference in response rate between the treatment groups was identified (RR=0.44; 95% CI 0.17 to 1.13; P=0.09). A significant difference in the occurrence of toxicities in favour of MTX was identified, but with regard to quality of life treatment with cisplatin seemed to give better results.For other combinations of treatment including and not including MTX no studies were identified.

AUTHORS' CONCLUSIONS

Since no RCTs or CCTs in which only the use of MTX differed between the treatment groups were identified, no definitive conclusions can be made about the effects on antitumour efficacy, toxicities and quality of life of the addition of MTX to treatment of children and young adults with primary high-grade osteosarcoma. The same is true for combinations of treatment including and not including MTX other than treatment with MTX versus treatment with cisplatin. Only 1 RCT comparing MTX with cisplatin treatment was available and therefore, no definitive conclusions can be made about the effectiveness of these agents in children and young adults with primary high-grade osteosarcoma. Furthermore, this study was performed in a different treatment era. Nowadays single agent treatment of osteosarcoma is considered inadequate. Based on the currently available evidence, we are not able to give recommendations for the use of MTX in clinical practice. More high quality research is needed.

The molecular pathogenesis of osteosarcoma: a review

Osteosarcoma is the most common primary malignancy of bone. It arises in bone during periods of rapid growth and primarily affects adolescents and young adults. The 5-year survival rate for osteosarcoma is 60%-70%, with no significant improvements in prognosis since the advent of multiagent chemotherapy. Diagnosis, staging, and surgical management of osteosarcoma remain focused on our anatomical understanding of the disease. As our knowledge of the molecular pathogenesis of osteosarcoma expands, potential therapeutic targets are being identified. A comprehensive understanding of these mechanisms is essential if we are to improve the prognosis of patients with osteosarcoma through tumour-targeted therapies. This paper will outline the pathogenic mechanisms of osteosarcoma oncogenesis and progression and will discuss some of the more frontline translational studies performed to date in search of novel, safer, and more targeted drugs for disease management.

Influence of reduced folate carrier and dihydrofolate reductase genes on methotrexate-induced cytotoxicity

PURPOSE

The aim of this study is to investigate the effect of genetic variations and the expression of the reduced folate carrier (RFC) and dihydrofolate reductase (DHFR) on the drug sensitivity to methotrexate (MTX) in different cancer cell lines.

MATERIALS AND METHODS

We examined the six human cancer cell lines (MCF-7, AGS, A549, NCI-H23, HCT-116 and Saos-2). The cytotoxicity of MTX was measured by sulforhodamine B (SRB) assay. The expressions of the DHFR and RFC were evaluated by real-time PCR and western blotting. Four single nucleotide polymorphisms (SNPs) of the DHFR and two SNPs of the RFC were genotyped.

RESULTS

The IC₅₀s of MTX was in an extensively broad range from 6.05±0.81 nM to>1,000 nM in the cell lines. The Saos-2 (>1,000 nM) and MCF-7 (114.31±5.34 nM) cells were most resistant to MTX; in contrast, the AGS and HCT-116 cells were highly sensitive to MTX with an IC(50) of 6.05±0.81 nM and 13.56±3.76 nM, respectively. A reciprocal change of the RFC and DHFR mRNA expression was found between the MTX-sensitive AGS and MTX-resistant Saos-2 cells. There was no significant difference in the expression levels of RFC protein in both the AGS and Saos-2 cells, whereas DHFR protein was more increased in the MTX-resistant Saos-2 cells treated with MTX. The genotype of the MTX-sensitive AGS cells were mutant variants of the DHFR; in contrast, the Saos-2 cells had the wild-type of the DHFR.

CONCLUSION

In conclusion, this study showed that inverse change of the RFC and DHFR mRNA and protein expression was associated with RFC and DHFR polymorphisms and it is postulated that this phenomenon might play an important role in sensitivity of certain cancers to MTX.

Emerging drugs for high-grade osteosarcoma

IMPORTANCE OF THE FIELD

Osteosarcoma (OS) is the most common primary malignant bone tumour in children and adolescents. This review focuses on the most promising therapeutic markers and drugs which may potentially be considered for innovative high-grade OS treatments.

AREAS COVERED IN THIS REVIEW

The list of drugs and compounds reviewed has been generated by taking into account those which target markers of potential clinical interest for high-grade OS and have been included in Phase I, II or III clinical trials. The literature search covers the last 40 years, starting from the first OS chemotherapy reports of the early 1970s. Particular relevance was given to reports and reviews on new targeted therapies of possible clinical usefulness for high-grade OS.

WHAT THE READER WILL GAIN

This review gives an updated overview of novel therapeutic approaches which have been or are going to be evaluated in Phase I/II/III clinical studies for high-grade OS.

TAKE HOME MESSAGE

On the basis of the information that has emerged so far, it can be predicted that in the next 5 - 10 years, new agents to be included in innovative treatment strategies for selected subgroups of high-grade OS patients may become available.

MYC in oncogenesis and as a target for cancer therapies

MYC proteins (c-MYC, MYCN, and MYCL) regulate processes involved in many if not all aspects of cell fate. Therefore, it is not surprising that the MYC genes are deregulated in several human neoplasias as a result from genetic and epigenetic alterations. The near "omnipotency" together with the many levels of regulation makes MYC an attractive target for tumor intervention therapy. Here, we summarize some of the current understanding of MYC function and provide an overview of different cancer forms with MYC deregulation. We also describe available treatments and highlight novel approaches in the pursuit for MYC-targeting therapies. These efforts, at different stages of development, constitute a promising platform for novel, more specific treatments with fewer side effects. If successful a MYC-targeting therapy has the potential for tailored treatment of a large number of different tumors.

MYC high level gene amplification is a distinctive feature of angiosarcomas after irradiation or chronic lymphedema

Angiosarcomas (AS) are rare vascular malignancies that arise either de novo as primary tumors or secondary to irradiation or chronic lymphedema. The cytogenetics of angiosarcomas are poorly characterized. We applied array-comparative genomic hybridization as a screening method to identify recurrent alterations in 22 cases. Recurrent genetic alterations were identified only in secondary but not in primary AS. The most frequent recurrent alterations were high level amplifications on chromosome 8q24.21 (50%), followed by 10p12.33 (33%) and 5q35.3 (11%). Fluorescence in situ hybridization analysis in 28 primary and 33 secondary angiosarcomas (31 tumors secondary to irradiation, 2 tumors secondary to chronic lymphedema) confirmed high level amplification of MYC on chromosome 8q24.21 as a recurrent genetic alteration found exclusively in 55% of AS secondary to irradiation or chronic lymphedema, but not in primary AS. Amplification of MYC did not predispose to high grade morphology or increased cell turnover. In conclusion, despite their identical morphology, secondary AS are genetically different from primary AS and are characterized by a high frequency of high level amplifications of MYC. This finding may have implications both for the diagnosis and treatment of these tumors.

Prognostic significance of c-Myc expression in soft tissue leiomyosarcoma

The biological potential of soft tissue leiomyosarcoma is difficult to predict using current standard prognostic parameters, and control of systemic disease is challenging with current chemotherapeutic protocols. Additional prognostic markers and alternative treatment options are very much required. Previous studies implicate upregulation of the oncogenic nuclear transcription factor c-Myc with aggressive behavior of many solid tumors. Therefore, this oncoprotein was evaluated as a prognostic marker for overall and metastasis-free survival in leiomyosarcoma. Immunohistochemical stains for c-Myc were performed on 28 cases of leiomyosarcoma occurring in the deep somatic soft tissues. Comparisons of Kaplan-Meier survival curves stratified by c-Myc status and conventional prognostic factors (histological grade, tumor size, and tumor stage) were evaluated using standard univariate statistical methods. A subsequent multivariate survival analysis was carried out according to the Cox proportional hazards regression model adjusting for potential confounding prognostic factors. A total of 15 cases (54%) were positive for nuclear c-Myc expression. Patients with c-Myc-positive tumors had significantly shorter metastasis-free survival intervals compared with those with c-Myc-negative tumors (median, 9 months vs. >94 months; P=0.014). c-Myc positivity also correlated with decreased overall survival (median, 23 months vs. >94 months; P=0.017). Histological grade was the only other prognostic marker predictive of poor outcome in the univariate analyses. In the multivariate survival analysis, only c-Myc status reached statistical significance, suggesting that it is an important and independent predictor of prognosis in leiomyosarcoma. Detection of nuclear c-Myc in leiomyosarcoma predicts decreased overall and metastasis-free survival, independent of standard prognostic variables, tumor size, histological grade, and TNM stage. The expression of this oncoprotein may represent a useful prognostic marker and potential therapeutic target in leiomyosarcoma.

Mechanisms of gene amplification and evidence of coamplification in drug-resistant human osteosarcoma cell lines

Gene amplification and copy number changes play a pivotal role in malignant transformation and progression of human tumor cells by mediating the activation of genes and oncogenes, which are involved in many different cellular processes including development of drug resistance. Since doxorubicin (DX) and methotrexate (MTX) are the two most important drugs for high-grade osteosarcoma (OS) treatment, the aim of this study was to identify genes gained or amplified in six DX- and eight MTX-resistant variants of the human OS cell lines U-2OS and Saos-2, and to get insights into the mechanisms underlying the amplification processes. Comparative genomic hybridization techniques identified amplification of MDR1 in all six DX-resistant and of DHFR in three MTX-resistant U-2OS variants. In addition, progressive gain of MLL was detected in the four U-2OS variants with higher resistance levels either to DX or MTX, whereas gain of MYC was found in all Saos-2 MTX-resistant variants and the U-2OS variant with the highest resistance level to DX. Fluorescent in situ hybridization revealed that MDR1 was amplified in U-2OS and Saos-2/DX-resistant variants manifested as homogeneously staining regions and double minutes, respectively. In U-2OS/MTX-resistant variants, DHFR was amplified in homogeneously staining regions, and was coamplified with MLL in relation to the increase of resistance to MTX. Gene amplification was associated with gene overexpression, whereas gene gain resulted in up-regulated gene expression. These results indicate that resistance to DX and MTX in human OS cell lines is a multigenic process involving gene copy number and expression changes.

Over-expression of c-Myc oncoprotein in oral squamous cell carcinoma in the South Indian population

Oral neoplasm constitutes a predominant class of cancer that is encountered in South India. This is in large part due to the elevated risk of oncogenesis as a result of the habit of chewing of quids containing betel leaves, areca nut and smokeless tobacco. An array of molecular events are induced during the transformation of the buccal epithelium, among them the over-expression of oncogene products plays a key role. The c-Myc protein, a regulator of a number of key cellular signalling pathways, plays a pivotal role in a number of malignancies. The present study was undertaken to evaluate expression of the c-Myc protein in tumours of the oral cavity from the South Indian population, predominantly oral squamous cell carcinoma (OSCC). The c-Myc protein was over-expressed in 80% of the cases studied. Taking into account the pivotal role demonstrated for c-Myc in tumourigenesis, our observations suggest a key role for Myc oncoprotein in the genesis of OSCC as well as its potential as a therapeutic target in this population.