Osteosarcoma and chondrosarcoma: new signaling pathways as targets for novel therapeutic interventions

Comprehensive genomic analysis of primary bone sarcomas reveals different genetic patterns compared with soft tissue sarcomas

Introduction

Sarcomas are classified into two types, bone sarcoma and soft tissue sarcoma (STS), which account for approximately 1% of adult solid malignancies and 20% of pediatric solid malignancies. There exist more than 50 subtypes within the two types of sarcoma. Each subtype is highly diverse and characterized by significant variations in morphology and phenotypes. Understanding tumor molecular genetics is helpful in improving the diagnostic accuracy of tumors that have been difficult to classify based on morphology alone or that have overlapping morphological features. The different molecular characteristics of bone sarcoma and STS in China remain poorly understood. Therefore, this study aimed to analyze genomic landscapes and actionable genomic alterations (GAs) as well as tumor mutational burden (TMB), microsatellite instability (MSI), and programmed death ligand-1 (PD-L1) expression among Chinese individuals diagnosed with primary bone sarcomas and STS.

Methods

This retrospective study included 145 patients with primary bone sarcomas (n = 75) and STS (n = 70), who were categorized based on the 2020 World Health Organization classification system.

Results

Patients diagnosed with bone sarcomas were significantly younger than those diagnosed with STS (p < 0.01). The top 10 frequently altered genes in bone sarcoma and STS were TP53, CDKN2A, CDKN2B, MAP3K1, LRP1B, MDM2, RB1, PTEN, MYC, and CDK4.The EWSR1 fusions exhibited statistically significant differences (p < 0.01) between primary bone sarcoma and STS in terms of their altered genes. Based on the actionable genes defined by OncoKB, actionable GAs was found in 30.7% (23/75) of the patients with bone sarcomas and 35.7% (25/70) of those with STS. There were 4.0% (3/75) patients with bone sarcoma and 4.3% (3/70) patients with STS exhibited high tumor mutational burden (TMB-H) (TMB ≥ 10). There was only one patient with STS exhibited MSI-L, while the remaining cases were microsatellite stable. The positive rate of PD-L1 expression was slightly higher in STS (35.2%) than in bone sarcoma (33.3%), however, this difference did not reach statistical significance. The expression of PD-L1 in STS patients was associated with a poorer prognosis (p = 0.007). Patients with STS had a better prognosis than those with bone sarcoma, but the observed difference did not attain statistical significance (p = 0.21). Amplification of MET and MYC genes were negatively correlated with clinical prognosis in bone tumors (p<0.01).

Discussion

In conclusion, bone sarcoma and STS have significantly different clinical and molecular characteristics, suggesting that it is vital to diagnose accurately for clinical treatment. Additionally, comprehensive genetic landscape can provide novel treatment perspectives for primary bone sarcoma and STS. Taking TMB, MSI, PD-L1 expression, and OncoKB definition together into consideration, there are still many patients who have the potential to respond to targeted therapy or immunotherapy.

MicroRNA PC-3p-2869 Regulates Antler Growth and Inhibits Proliferation and Migration of Human Osteosarcoma and Chondrosarcoma Cells by Targeting CDK8, EEF1A1, and NTN1

MicroRNAs (miRNAs) play a crucial role in maintaining the balance between the rapid growth and suppression of tumorigenesis during antler regeneration. This study investigated the role of a novel miRNA, PC-3p-2869 (miR-PC-2869), in antler growth and its therapeutic potential in human osteosarcoma and chondrosarcoma. Stem-loop RT-qPCR showed that miR-PC-2869 was expressed extensively in diverse layers of antler tissues. Overexpression of miR-PC-2869 suppressed the proliferation and migration of antler cartilage cells. Similarly, heterologous expression of miR-PC-2869 reduced the proliferation, colony formation, and migration of osteosarcoma cell line MG63 and U2OS and chondrosarcoma cell line SW1353. Moreover, 18 functional target genes of miR-PC-2869 in humans were identified based on the screening of the reporter library. Among them, 15 target genes, including CDK8, EEF1A1, and NTN1, possess conserved miR-PC-2869-binding sites between humans and red deer (Cervus elaphus). In line with this, miR-PC-2869 overexpression decreased the expression levels of CDK8, EEF1A1, and NTN1 in MG63, SW1353, and antler cartilage cells. As expected, the knockdown of CDK8, EEF1A1, or NTN1 inhibited the proliferation and migration of MG63, SW1353, and antler cartilage cells, demonstrating similar suppressive effects as miR-PC-2869 overexpression. Furthermore, we observed that CDK8, EEF1A1, and NTN1 mediated the regulation of c-myc and cyclin D1 by miR-PC-2869 in MG63, SW1353, and antler cartilage cells. Overall, our work uncovered the cellular functions and underlying molecular mechanism of antler-derived miR-PC-2869, highlighting its potential as a therapeutic candidate for bone cancer.

Adenoviral delivery of VHL suppresses bone sarcoma cell growth through inhibition of Wnt/β-catenin signaling

The VHL tumor suppressor gene is frequently inactivated in several human tumors, including bone sarcomas. We previously identified that reduced expression of VHL protein is implicated in sarcomagenesis. However, the underlying biological functions of restored VHL protein expression have not been clearly elucidated in bone sarcomas. Here we initially constructed a recombinant adenovirus 5-VHL vector (Ad5-VHL) and evaluated its expression in bone sarcomas, and antitumor activity in vitro and in vivo. We found that the adenovirus-mediated increase of VHL significantly suppresses bone sarcoma cell growth, attributed to induction of apoptosis mediated by increased caspase-3 activity and modulated Bcl-2 protein family. This suppression effect involves inhibition of Wnt/β-catenin signaling and upregulation of GSK-3β. Moreover, Ad5-VHL showed a dramatic antitumor effect on a chondrosarcoma xenograft model. These findings establish that Ad5-VHL suppresses bone sarcoma cell growth by inhibiting Wnt/β-catenin signaling, and may be a novel target for gene-based therapy of bone sarcomas.

Deciphering signaling networks in osteosarcoma pathobiology

Osteosarcoma is the most frequent type of primary bone tumors among children and adolescents. During the past years, little progress has been made regarding prognosis of osteosarcoma patients, especially for those with metastatic disease. Genomic instability and gene alterations are common, but current data do not reveal a consistent and repeatable pattern of osteosarcoma development, thus paralleling the tumor's high heterogeneity. Critical signal transduction pathways have been implicated in osteosarcoma pathobiology and are being evaluated as therapeutic targets, including receptor activator for nuclear factor-κB (RANK), Wnt, Notch, phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin, and mechanotransduction pathways. Herein, we recapitulate and discuss recent advances in the context of molecular mechanisms and signaling networks that contribute to osteosarcoma progression and metastasis, towards patient-tailored and novel-targeted treatments.

Upregulated expression of microRNA-214 is linked to tumor progression and adverse prognosis in pediatric osteosarcoma

BACKGROUND

MicroRNA-214 (miR-214) expression has been demonstrated to be dysregulated in human malignancies and to play various roles in tumor progression. While previous study of miRNA expression profiling found that it was one of the most upregulated miRNAs in osteosarcoma signature, the potential role of miR-214 in osteosarcomas has been unclear. Therefore, the aim of this study was to investigate association of miR-214 expression with clinicopathologic features and prognosis in pediatric patients with osteosarcoma.

PROCEDURE

Quantitative real-time reverse transcriptase-polymerase chain reaction analysis was performed to detect expression levels of miR-214 in cancerous and noncancerous bone tissues from 92 children treated for primary osteosarcomas. Then, the clinical significance of miR-214 dysregulation in pediatric osteosarcomas was also determined.

RESULTS

Compared with noncancerous bone tissues, the expression levels of miR-214 were significantly upregulated in osteosarcoma tissues (P < 0.001). High miR-214 expression occurred more frequently in osteosarcoma tissues with large tumor size (P = 0.01), positive metastasis (P = 0.001) and poor response to pre-operative chemotherapy (P = 0.006). Moreover, high miR-214 expression was significantly associated with both shorter overall (P < 0.001) and progression-free survival (PFS; P = 0.001). Multivariate analysis by the Cox proportional hazard model further confirmed that high miR-214 expression was an independent prognostic factor of unfavorable survival in pediatric osteosarcoma (for overall survival: P = 0.008; for PFS: P = 0.01).

CONCLUSION

Our data offer evidence that upregulated expression of miR-214 may be linked to tumor progression and adverse prognosis in pediatric osteosarcoma. Further investigation in prospective studies would appear warranted.

Combined microRNA-340 and ROCK1 mRNA profiling predicts tumor progression and prognosis in pediatric osteosarcoma

To investigate the association of combined microRNA-340 (miR-340) and ROCK1 mRNA profiling with clinicopathologic features and prognosis in pediatric patients with osteosarcoma. Quantitative real-time reverse transcriptase-polymerase chain reaction analysis was performed to detect expression levels of miR-340 and ROCK1 mRNA in cancerous and noncancerous bone tissues from 92 children treated for primary osteosarcomas. Compared with noncancerous bone tissues, the expression levels of miR-340 and ROCK1 mRNA were, respectively, downregulated and upregulated in osteosarcoma tissues (both p < 0.001), which was consistent with the results of in situ hybridization and immunohistochemistry analysis. The downregulation of miR-340 was negatively correlated with the upregulation of ROCK1 mRNA in osteosarcoma tissues (r = −0.78, p = 0.001). In addition, the combined miR-340 downregulation and ROCK1 upregulation (miR-340-low/ROCK1-high) occurred more frequently in osteosarcoma tissues with positive metastasis (p < 0.001) and poor response to pre-operative chemotherapy (p = 0.002). Moreover, miR-340-low/ROCK1-high expression was significantly associated with both shortest overall survival (p < 0.001) and progression-free survival (p < 0.001). Multivariate analysis further confirmed that miR-340-low/ROCK1-high expression was an independent prognostic factor of unfavorable survival in pediatric osteosarcoma (for overall survival: p = 0.006, for progression-free survival: p = 0.008). Our data offer convincing evidence, for the first time, that the combined miR-340 downregulation and ROCK1 upregulation may be linked to tumor progression and adverse prognosis in pediatric osteosarcoma.

rAAV Vectors as Safe and Efficient Tools for the Stable Delivery of Genes to Primary Human Chondrosarcoma Cells In Vitro and In Situ

Treatment of chondrosarcoma remains a major challenge in orthopaedic oncology. Gene transfer strategies based on recombinant adenoassociated viral (rAAV) vectors may provide powerful tools to develop new, efficient therapeutic options against these tumors. In the present study, we tested the hypothesis that rAAV is adapted for a stable and safe delivery of foreign sequences in human chondrosarcoma tissue by transducing primary human chondrosarcoma cells in vitro and in situ with different reporter genes (E. coli lacZ, firefly luc, Discosoma sp. RFP). The effects of rAAV administration upon cell survival and metabolic activities were also evaluated to monitor possibly detrimental effects of the gene transfer method. Remarkably, we provide evidence that efficient and prolonged expression of transgene sequences via rAAV can be safely achieved in all the systems investigated, demonstrating the potential of the approach of direct application of therapeutic gene vectors as a means to treat chondrosarcoma.

Osteosarcoma: Differential Diagnostic Considerations

Accurate diagnosis of bone-forming tumors, including correct subclassification of osteogenic sarcoma is critical for determination of appropriate clinical management and prediction of patient outcome. The morphologic spectrum of osteogenic sarcoma is extensive, however, and its histologic mimics are numerous. This review focuses on the major differential diagnoses of the specific subtypes of osteosarcoma, presents summaries of various diagnoses, and provides tips to overcoming pitfalls in diagnosis.

Reduced expression of von Hippel-Lindau protein correlates with decreased apoptosis and high chondrosarcoma grade

BACKGROUND

Mutations and loss of the von Hippel-Lindau (VHL) tumor suppressor gene are associated with most renal cancers as well as several other types of human tumors, but the potential role of the VHL protein (pVHL) in patients with chondrosarcoma has not been characterized. The purpose of the present study was to investigate the expression profiles of pVHL in chondrosarcoma and its association with clinicopathologic parameters, Bax expression, the apoptosis index, and overall survival of patients with chondrosarcoma.

METHODS

The messenger RNA (mRNA) and protein levels of VHL in fresh specimens from eight chondrosarcomas were studied with use of real-time polymerase chain reaction and Western blot, respectively. The protein expression of VHL and Bax was investigated by means of immunohistochemical analysis of paraffin-embedded clinical specimens from seventeen benign cartilage tumors and thirty-four chondrosarcomas. The apoptosis index in chondrosarcoma was examined by means of the TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) assay. Curves for overall survival were drawn according to the Kaplan-Meier method, and differences were analyzed with the log-rank test. The association of pVHL expression with the clinicopathologic parameters, Bax expression, apoptosis index, and overall survival for patients with chondrosarcoma was also analyzed.

RESULTS

Levels of VHL protein (p = 0.005) and mRNA (p = 0.008) were significantly reduced in chondrosarcoma tissues as compared with the paired adjacent normal tissues. Immunohistochemical analysis showed decreased pVHL in a significantly higher proportion of chondrosarcomas (64.7%) than benign cartilage tumors (29.4%). pVHL expression was positively correlated with Bax expression and the apoptosis index in chondrosarcoma. Longitudinal studies of a cohort of patients with chondrosarcomas showed that decreased pVHL expression significantly correlated with increased tumor grade (p = 0.026) but was not independently predictive of overall survival.

CONCLUSIONS

Reduced pVHL expression was associated with decreased apoptosis and increasing chondrosarcoma grade, but the relationship between these findings and chondrosarcoma pathogenesis requires further study.

Characterization of canine osteosarcoma by array comparative genomic hybridization and RT-qPCR: signatures of genomic imbalance in canine osteosarcoma parallel the human counterpart

Osteosarcoma (OS) is the most commonly diagnosed malignant bone tumor in humans and dogs, characterized in both species by extremely complex karyotypes exhibiting high frequencies of genomic imbalance. Evaluation of genomic signatures in human OS using array comparative genomic hybridization (aCGH) has assisted in uncovering genetic mechanisms that result in disease phenotype. Previous low-resolution (10-20 Mb) aCGH analysis of canine OS identified a wide range of recurrent DNA copy number aberrations, indicating extensive genomic instability. In this study, we profiled 123 canine OS tumors by 1 Mb-resolution aCGH to generate a dataset for direct comparison with current data for human OS, concluding that several high frequency aberrations in canine and human OS are orthologous. To ensure complete coverage of gene annotation, we identified the human refseq genes that map to these orthologous aberrant dog regions and found several candidate genes warranting evaluation for OS involvement. Specifically, subsequenct FISH and qRT-PCR analysis of RUNX2, TUSC3, and PTEN indicated that expression levels correlated with genomic copy number status, showcasing RUNX2 as an OS associated gene and TUSC3 as a possible tumor suppressor candidate. Together these data demonstrate the ability of genomic comparative oncology to identify genetic abberations which may be important for OS progression. Large scale screening of genomic imbalance in canine OS further validates the use of the dog as a suitable model for human cancers, supporting the idea that dysregulation discovered in canine cancers will provide an avenue for complementary study in human counterparts.

Imaging pediatric bone sarcomas

Primary malignant bone tumors are rare and account for about 6% of all new pediatric cancer cases per year in the United States. Identification of the lesion not uncommonly occurs as a result of imaging performed for trauma. Clinical and standard imaging characteristics of the various tumor types are evolving in concert with treatment advancements and clinical trial regimens. This article reviews the 3 most common pediatric bone sarcomas-osteosarcoma, Ewing sarcoma, and chondrosarcoma-and their imaging as applicable to contemporary disease staging and monitoring, and explores the roles of evolving imaging techniques.

Recombinant human PDCD5 sensitizes chondrosarcomas to cisplatin chemotherapy in vitro and in vivo

Clinical management of chondrosarcoma remains a challenging problem, largely due to the toxicity and resistance of this tumor to conventional chemotherapy. Programmed Cell Death 5 (PDCD5) is a protein that accelerates apoptosis in different cell types in response to various stimuli, and has been shown to be down-regulated in many cancer tissues. In this study, mRNA and protein levels of PDCD5 were found to be up-regulated in cisplatin-treated SW1353 chondrosarcoma cells compared with untreated cells. Recombinant human PDCD5 (rhPDCD5) was also shown to sensitize chondrosarcoma cells to cisplatin-based chemotherapy, with inhibition of cell growth and apoptosis detected both in vitro and in vivo. Increased expression of Bax and decreased expression of Bcl-2 were also observed, along with release of cytochrome c from mitochondria into the cytosol. Additionally, cleavage of caspase-9 and caspase-3, as well as the cleavage of poly (ADP-ribose) polymerase (PARP), were detected, suggesting that sensitization of chondrosarcoma cells involves the intrinsic mitochondrial apoptosis pathway. In vivo, the treatment of a xenograft model of chondrosarcoma with rhPDCD5 and cisplatin significantly inhibited tumor cell proliferation and induced apoptosis compared to treatment with cisplatin alone. Overall, these data provide a theoretical basis for the administration of rhPDCD5 and cisplatin for the treatment of patients with chondrosarcoma.

Frequent attenuation of the WWOX tumor suppressor in osteosarcoma is associated with increased tumorigenicity and aberrant RUNX2 expression

The WW domain-containing oxidoreductase (WWOX) is a tumor suppressor that is deleted or attenuated in most human tumors. Wwox-deficient mice develop osteosarcoma (OS), an aggressive bone tumor with poor prognosis that often metastasizes to lung. On the basis of these observations, we examined the status of WWOX in human OS specimens and cell lines. In human OS clinical samples, WWOX expression was absent or reduced in 58% of tumors examined (P < 0.0001). Compared with the primary tumors, WWOX levels frequently increased in tumors resected following chemotherapy. In contrast, tumor metastases to lung often exhibited reduced WWOX levels relative to the primary tumor. In human OS cell lines having reduced WWOX expression, ectopic expression of WWOX inhibited proliferation and attenuated invasion in vitro, and suppressed tumorigenicity in nude mice. Expression of WWOX was associated with reduced RUNX2 expression in OS cell lines, whereas RUNX2 levels were elevated in femurs of Wwox-deficient mice. Furthermore, WWOX reconstitution in HOS cells was associated with downregulation of RUNX2 levels and RUNX2 target genes, consistent with the ability of WWOX to suppress RUNX2 transactivation activity. In clinical samples, RUNX2 was expressed in the majority of primary tumors and undetectable in most tumors resected following chemotherapy, whereas most metastases were RUNX2 positive. Our results deepen the evidence of a tumor suppressor role for WWOX in OS, furthering its prognostic and therapeutic significance in this disease.

WWOX gene and gene product: tumor suppression through specific protein interactions

The WWOX gene, an archetypal fragile gene, encompasses a chromosomal fragile site at 16q23.2, and encodes the approximately 46-kDa Wwox protein, with WW domains that interact with a growing list of interesting proteins. If the function of a protein is defined by the company it keeps, then Wwox is involved in numerous important signal pathways for bone and germ-cell development, cellular and animal growth and death, transcriptional control and suppression of cancer development. Because alterations to genes at fragile sites are exquisitely sensitive to replication stress-induced DNA damage, there has been an ongoing scientific discussion questioning whether such gene expression alterations provide a selective advantage for clonal expansion of neoplastic cells, and a parallel discussion on why important genes would be present at sites that are susceptible to inactivation. We offer some answers through a description of known WWOX functions.

WWOX: its genomics, partners, and functions

The WW domain-containing oxidoreductase (WWOX) spans one of the most active common fragile sites (CFSs) involved in cancer, FRA16D. WWOX encodes a 46-kDa protein that contains two N-terminal WW domains and a central short-chain dehydrogenase/reductase (SDR) domain. Through its WW domain, Wwox interacts with its partners and modulates their functions. Our data indicate that Wwox suppresses the transactivation function of several transcription factors implied in neoplasia by sequestering them in the cytoplasm. Work from our laboratory and other research groups have demonstrated that Wwox participates in a number of cellular processes including growth, differentiation, apoptosis, and tumor suppression. Targeted deletion of the Wwox gene in mice causes increased spontaneous and chemically induced tumor incidence supporting bona fide tumor suppressor function of WWOX. Moreover, generation of the Wwox-deficient mice uncovers, at least in part, some of the physiological in vivo functions of the WWOX gene. This review focuses on recent progress that elucidates Wwox functions in biology and pathology.

Development of chondrosarcoma animal models for assessment of adjuvant therapy

Chondrosarcoma is a primary cancer of bone causing significant morbidity due to local recurrence and limited treatment options. Relatively few chondrosarcoma animal models have been developed, and the only orthotopic model is technically demanding and has limited clinical relevance. The aim of this review is to assess the features of current animal chondrosarcoma models for the purpose of developing new models in which to test adjuvant chondrosarcoma therapy. The available literature on this topic was identified using the PubMed database, and then analysed for relevance to the human chondrosarcoma disease and feasibility in testing new therapeutic agents. Animal-derived chondrosarcoma models comprise predominantly allograft tumour transplanted into the rat (Swarm rat chondrosarcoma) or the hamster. These types of models are less relevant to the human disease and have been more useful for evaluation of chondrosarcoma growth and histology than in developing novel therapeutic agents. The athymic nude mouse has enabled reliable human xenograft transplantation. A number of human chondrosarcoma cell lines have been successfully used to generate tumours in this species, including OUMS-27 and HCS-2/A. Although effective in demonstrating anti-tumour effects of a number of agents, the lack of a representative orthotopic model diminishes overall clinical relevance. More clinically relevant models of human chondrosarcoma progression are required either through transgenic mice or orthotopic human xenograft models.

Modulation of the E2F1-driven cancer cell fate by the DNA damage response machinery and potential novel E2F1 targets in osteosarcomas

Osteosarcoma is the most common primary bone cancer. Mutations of the RB gene represent the most frequent molecular defect in this malignancy. A major consequence of this alteration is that the activity of the key cell cycle regulator E2F1 is unleashed from the inhibitory effects of pRb. Studies in animal models and in human cancers have shown that deregulated E2F1 overexpression possesses either "oncogenic" or "oncosuppressor" properties, depending on the cellular context. To address this issue in osteosarcomas, we examined the status of E2F1 relative to cell proliferation and apoptosis in a clinical setting of human primary osteosarcomas and in E2F1-inducible osteosarcoma cell line models that are wild-type and deficient for p53. Collectively, our data demonstrated that high E2F1 levels exerted a growth-suppressing effect that relied on the integrity of the DNA damage response network. Surprisingly, induction of p73, an established E2F1 target, was also DNA damage response-dependent. Furthermore, a global proteome analysis associated with bioinformatics revealed novel E2F1-regulated genes and potential E2F1-driven signaling networks that could provide useful targets in challenging this aggressive neoplasm by innovative therapies.

Cause and consequences of genetic and epigenetic alterations in human cancer

Both genetic and epigenetic changes contribute to development of human cancer. Oncogenomics has primarily focused on understanding the genetic basis of neoplasia, with less emphasis being placed on the role of epigenetics in tumourigenesis. Genomic alterations in cancer vary between the different types and stages, tissues and individuals. Moreover, genomic change ranges from single nucleotide mutations to gross chromosomal aneuploidy; which may or may not be associated with underlying genomic instability. Collectively, genomic alterations result in widespread deregulation of gene expression profiles and the disruption of signalling networks that control proliferation and cellular functions. In addition to changes in DNA and chromosomes, it has become evident that oncogenomic processes can be profoundly influenced by epigenetic mechanisms. DNA methylation is one of the key epigenetic factors involved in regulation of gene expression and genomic stability, and is biologically necessary for the maintenance of many cellular functions. While there has been considerable progress in understanding the impact of genetic and epigenetic mechanisms in tumourigenesis, there has been little consideration of the importance of the interplay between these two processes. In this review we summarize current understanding of the role of genetic and epigenetic alterations in human cancer. In addition we consider the associated interactions of genetic and epigenetic processes in tumour onset and progression. Furthermore, we provide a model of tumourigenesis that addresses the combined impact of both epigenetic and genetic alterations in cancer cells.

A review of clinical and molecular prognostic factors in osteosarcoma

Traditional prognostic determinants in osteosarcoma have included demographics (age, sex), tumour size, site, stage, and the response to chemotherapy. Many of these are determined using varying techniques and units of measurement, which can make comparison between studies difficult. The absence of survival difference between limb sparing surgery and amputation has been repeatedly demonstrated in primary disease, and even in the setting of pathological fracture. On the other hand, there is still some controversy over the existence of increased local recurrence for limb-sparing surgery, and the implications of this. Commonly used prognostic determinants such as metastases, and response to chemotherapy enable a high degree of prognostic accuracy but usually at a late stage in the course of disease. Leading on from this, there is a need to uncover molecular pathways with specific influence over osteosarcoma progression to facilitate earlier treatment changes. Some important pathways are already being defined, for example the association of CXCR4 with metastases on presentation, the likelihood of doxorubicin resistance with positive P-glycoprotein, and the reduced survival prediction of over expressed survivin. It is anticipated that the future of osteosarcoma treatment will involve treatment tailored to the molecular profile of tumours at diagnosis, adjuvant therapy directed towards dysfunctional molecular pathways rather than the use of cytotoxics, and a more standardised approach to the measurement of clinical prognostic factors.