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Multidisciplinary tumor boards (MTBs) facilitate decision-making among subspecialists in the care of oncology patients, but the mechanisms by which they enhance outcomes remain incompletely understood. Our aim was to measure the agreement between sarcoma MTBs and radiology reports’ disease assessment and management recommendations. This single-center IRB-approved retrospective study evaluated cases presented at a weekly sarcoma MTB from 1 August 2020 to 31 July 2021. Cases without clinical notes, imaging studies, or radiology reports were excluded. The data collected included the patient’s clinical status at the time of the MTB, the treatment response assessment by the MTB and radiologists (stable disease; partial response; complete response; progressive disease/recurrence), and the recommendations of the radiology reports and of the MTB. The agreement between the initial radiologist review and MTB on disease assessment and recommendations was analyzed using kappa statistics. In total, 283 cases met the inclusion criteria. Radiology reports provided recommendations in 34.3% of cases, which were adhered to by the ordering providers in 73.2% of cases. The agreement between MTBs and radiology reports was moderate in disease assessment (86.2% agreement; κ = 0.78; p < 0.0001) and negligible in recommendations (36% agreement; κ = 0.18; p < 0.0001). Radiologists were more likely to assign progressive disease/recurrence than MTBs (54.4% vs. 44.4%; p < 0.001) and to recommend short-term imaging follow-up more commonly than MTBs (46.4% vs. 21.7%; p < 0.001). At a tertiary care center, radiologists’ isolated interpretations of imaging findings and management recommendations frequently differ from the MTB’s consensus, reflecting the value of multidisciplinary discussions incorporating the patient’s clinical status and the available treatment options into the final radiographic assessment.

Osteosarcoma (OS) is a type of bone cancer that is derived from primitive mesenchymal cells typically affecting children and young adults. The current standard of treatment is a combination of neoadjuvant chemotherapy and surgical resection of the cancerous bone. Post-resection challenges in bone regeneration arise. To determine the appropriate amount of bone to be removed, preoperative imaging techniques such as bone and CT scans are employed. To prevent local recurrence, the current standard of care suggests maintaining bony and soft tissue margins from 3 to 7 cm beyond the tumor. The amount of bone removed in an OS patient leaves too large of a deficit for bone to form on its own and requires reconstruction with metal implants or allografts. Both methods require the bone to heal, either to the implant or across the allograft junction, often in the setting of marrow-killing chemotherapy. Therefore, the issue of bone regeneration within the surgically resected margins remains an important challenge for the patient, family, and treating providers. Mesenchymal stem/stromal cells (MSCs) are potential agents for enhancing bone regeneration post tumor resection. MSCs, used with scaffolds and growth factors, show promise in fostering bone regeneration in OS cases. We spotlight two MSC types—bone marrow-derived (BM-MSCs) and adipose tissue-derived (ASCs)—highlighting their bone regrowth facilitation and immunomodulatory effects on immune cells like macrophages and T cells, enhancing therapeutic outcomes. The objective of this review is two-fold: review work demonstrating any ability of MSCs to target the deranged immune system in the OS microenvironment, and synthesize the available literature on the use of MSCs as a therapeutic option for stimulating bone regrowth in OS patients post bone resection. When it comes to repairing bone defects, both MB-MSCs and ASCs hold great potential for stimulating bone regeneration. Research has showcased their effectiveness in reconstructing bone defects while maintaining a non-tumorigenic role following wide resection of bone tumors, underscoring their capability to enhance bone healing and regeneration following tumor excisions.

T‐lymphokine‐activated killer (T‐LAK) cell‐originated protein kinase (TOPK) is an emerging target with critical roles in various cancers; however, its expression and function in osteosarcoma remain unexplored. We evaluated TOPK expression using RNA sequencing and gene expression data from public databases (TARGET‐OS, CCLE, GTEx, and GENT2) and immunohistochemistry in an osteosarcoma tissue microarray (TMA). TOPK gene expression was significantly higher in osteosarcoma than normal tissues and directly correlated with shorter overall survival. TOPK was overexpressed in 83.3% of the osteosarcoma specimens within our TMA and all osteosarcoma cell lines, whereas normal osteoblast cells had no aberrant expression. High expression of TOPK associated with metastasis, disease status, and shorter overall survival. Silencing of TOPK with small interfering RNA (siRNA) decreased cell viability, and inhibition with the selective inhibitor OTS514 suppressed osteosarcoma cell proliferation, migration, colony‐forming ability, and spheroid growth. Enhanced chemotherapeutic sensitivity and a synergistic effect were also observed with the combination of OTS514 and either doxorubicin or cisplatin in osteosarcoma cell lines. Taken together, our study demonstrated that TOPK is a potential prognostic biomarker and therapeutic target for osteosarcoma treatment.

Abstract EVs have emerged as an important component in tumour initiation, progression and metastasis. Although notable progresses have been made, the detection of EV cargoes remain significantly challenging for researchers to practically use; faster and more convenient methods are required to validate the EV cargoes, especially as biomarkers. Here we show, the possibility of examining embedded EVs as substrates to be used for detecting DNA amplification through ultrasensitive in situ hybridization (ISH). This methodology allows the visualization of DNA targets in a more direct manner, without time consuming optimization steps or particular expertise. Additionally, formalin‐fixed paraffin‐embedded (FFPE) blocks of EVs allows long‐term preservation of samples, permitting future studies. We report here: (i) the successful isolation of EVs from liposarcoma tissues; (ii) the EV embedding in FFPE blocks (iii) the successful selective, specific ultrasensitive ISH examination of EVs derived from tissues, cell line, and sera; (iv) and the detection of MDM2 DNA amplification in EVs from liposarcoma tissues, cell lines and sera. Ultrasensitive ISH on EVs would enable cargo study while the application of ISH to serum EVs, could represent a possible novel methodology for diagnostic confirmation. Modification of probes may enable researchers to detect targets and specific DNA alterations directly in tumour EVs, thereby facilitating detection, diagnosis, and improved understanding of tumour biology relevant to many cancer types.

Synovial sarcoma is typical aggressive malignant without satisfactory treatment outcome in adult series. Cyclin-dependent kinases (CDKs) in transcription have been considered promising molecular targets in cancer. Among these, CDK7 has been shown to play important roles in the pathogenesis of malignancies. However, the modulation mechanism of CDK7-regulated transcription in synovial sarcoma is unknown. In the present study, we aim to determine the expression and function of CDK7 in the transcription cycle of RNA polymerase II (RNAP II), and evaluate its prognostic and therapeutic significance in synovial sarcoma. Results showed that overexpression of CDK7 correlates with higher clinical stage and grade, and worse outcomes in clinic. High CDK7 expression was confirmed in all tested human synovial sarcoma cell lines and CDK7 was largely localized to the cell nucleus. Downregulation through siRNA or inhibition with the CDK7-targeting agent BS-181 exhibited dose-dependent cytotoxicity and prevented cell colony formation. Western blots demonstrated that inhibition of CDK7 paused transcription by a reduction of RNAP II phosphorylation. Blocking CDK7-dependent transcriptional addiction was accompanied by promotion of apoptosis. Furthermore, the CDK7-specific inhibitor reduced 3D spheroid formation and migration of synovial sarcoma. Collectively, our findings highlight the role of CDK7-dependent transcriptional addiction in human synovial sarcoma. CDK7-specific cytotoxic agents are therefore promising novel treatment options for synovial sarcoma.

Abstract Osteosarcoma (OS) is the most common primary bone malignancy and responsible for considerable morbidity and mortality due to its high rates of pulmonary metastasis. Although neoadjuvant chemotherapy has improved 5-year survival rates for patients with localized OS from 20% to over 65%, outcomes for those with metastasis remain dismal. In addition, therapeutic regimens have not significantly improved patient outcomes over the past four decades, and metastases remains a primary cause of death and obstacle in curative therapy. These limitations in care have given rise to numerous works focused on mechanisms and novel targets of OS pathogenesis, including tumor niche factors. OS is notable for its hallmark production of rich extracellular matrix (ECM) of osteoid that goes beyond simple physiological growth support. The aberrant signaling and structural components of the ECM are rich promoters of OS development, and very recent works have shown the specific pathogenic phenotypes induced by these macromolecules. Here we summarize the current developments outlining how the ECM contributes to OS progression and metastasis with supporting mechanisms. We also illustrate the potential of tumorigenic ECM elements as prognostic biomarkers and therapeutic targets in the evolving clinical management of OS.

Background The dedifferentiated variant of chondrosarcoma is highly aggressive and carries an especially grim prognosis. While chemotherapeutics has failed to benefit patients with dedifferentiated chondrosarcoma significantly, preclinical chemosensitivity studies have been limited by a scarcity of available cell lines. There is, therefore, an urgent need to expand the pool of available cell lines. Methods We report the establishment of a novel dedifferentiated chondrosarcoma cell line DDCS2, which we isolated from the primary tumor specimen of a 60-year-old male patient. We characterized its short tandem repeat (STR) DNA profile, growth potential, antigenic markers, chemosensitivity, and oncogenic spheroid and colony-forming capacity. Results DDCS2 showed a spindle to polygonal shape and an approximate 60-hour doubling time. STR DNA profiling revealed a unique genomic identity not matching any existing cancer cell lines within the ATCC, JCRB, or DSMZ databases. There was no detectable contamination with another cell type. Western blot and immunofluorescence assays were consistent with a mesenchymal origin, and our MTT assay revealed relative resistance to conventional chemotherapeutics, which is typical of a dedifferentiated chondrosarcoma. Under ex vivo three-dimensional (3D) culture conditions, the DDCS2 cells produced spheroid patterns similar to the well-established CS-1 and SW1353 chondrosarcoma cell lines. Conclusion Our findings confirm DDCS2 is a novel model for dedifferentiated chondrosarcoma and therefore adds to the limited pool of current cell lines urgently needed to investigate the chemoresistance within this deadly cancer.

Abstract Ovarian cancer is one of the most common gynecological malignancies. Upon initial diagnosis, the majority of patients present with widespread metastatic growth within the peritoneal cavity. This metastatic growth occurs in stages, with the formation of a pre-metastatic niche occurring prior to macroscopic tumor cell invasion. Exosomes released by the primary ovarian tumor are small extracellular vesicles which prepare the distant tumor microenvironment for accelerated metastatic invasion. They regulate intercellular communication between tumor cells and normal stroma, cancer-associated fibroblasts, and local immune cells within the tumor microenvironment. In this review, we highlight the emerging roles of ovarian cancer exosomes as coordinators of pre-metastatic niche formation, biomarkers amenable to liquid biopsy, and targets of chemotherapy.

Background: Cyclin-dependent protein kinase 9 (CDK9) has been shown to play an important role in the pathogenesis of malignant tumors. However, the expression and function of CDK9 remain unknown in osteosarcomas. The purpose of this study is to assess the expression, function and clinical prognostic relationship of CDK9 in osteosarcomas. Methods: A tissue microarray of 70 patient specimens was analyzed by immunohistochemistry to measure CDK9 expression, which was further investigated for correlation with patient clinical characteristics. CDK9 expression in osteosarcoma cell lines and patient tissues was also evaluated by Western blotting. CDK9-specific siRNA and the CDK9 inhibitor were applied to determine the effect of CDK9 inhibition on osteosarcoma cell proliferation and anti-apoptotic activity. The clonogenicity and migration activity were also examined using clonogenic and wound healing assays. A 3D cell culture model was performed to mimic the in vivo osteosarcoma environment to further validate the effect of CDK9 inhibition on osteosarcoma cells. Findings: We demonstrated that higher CDK9-expression is associated with significantly shortened patient survival by immunohistochemistry. Expression of CDK9 is inversely correlated to the percent of tumor necrosis post-neoadjuvant chemotherapy, which is the most important predictive factor of disease outcome for osteosarcoma patients. Knockdown of CDK9 with siRNA and inhibition of CDK9 activity with inhibitor decreased cell proliferation and induced apoptosis in osteosarcoma. Interpretation: High expression of CDK9 is an independent predictor of poor prognosis in osteosarcoma patients. Our results suggest that CDK9 is a novel prognostic marker and a promising therapeutic target for osteosarcomas. Keywords: CDK9, Osteosarcoma, Prognostic marker, Therapeutic target, Apoptosis

Background: Although ataxia-telangiectasia and Rad3 related (ATR) has an established role in the DNA damage response of various cancers, its clinical and prognostic significance in ovarian cancer remains largely unknown. The aims of this study were to assess the expression, function, and clinical prognostic relationship of ATR and phospho-ATR ser428 (p-ATR) in ovarian cancer. Methods: We confirmed ATR and p-ATR expression by immunohistochemistry (IHC) in a unique ovarian cancer tissue microarray constructed of paired primary, recurrent, and metastatic tumor tissues from 26 individual patients. ATR-specific small interfering RNA (siRNA) and ATR inhibitor VE-822 were applied to determine the effects of ATR inhibition on ovarian cancer cell proliferation, apoptosis, and DNA damage. ATR expression and the associated proteins of the ATR/Chk1 pathway in ovarian cancer cell lines were evaluated by Western blotting. The clonogenicity was also examined using clonogenic assays. A three dimensional (3D) cell culture model was performed to mimic the in vivo ovarian cancer environment to further validate the effects of ATR inhibition on ovarian cancer cells. Results: We show recurrent ovarian cancer tissues express higher levels of ATR and p-ATR than their patient-matched primary tumor counterparts. Additionally, higher expression of p-ATR correlates with decreased survival in ovarian cancer patients. Treatment of ovarian cancer cells with ATR specific siRNA or ATR inhibitor VE-822 led to significant apoptosis and inhibition of cellular proliferation, with reduced phosphorylation of Chk1 (p-Chk1), Cdc25c (p-Cdc25c), Cdc2 (p-Cdc2), and increased expression of cleaved PARP and γH2AX. Inhibition of ATR also suppressed clonogenicity and spheroid growth of ovarian cancer cells. Conclusion: Our results support the ATR and p-ATR pathway as a prognostic biomarker, and targeting the ATR machinery is an emerging therapeutic approach in the treatment of ovarian cancer.

PurposeChordomas are rare, slow-growing sarcomas without any accepted prognostic biomarkers. Owing to their proximity to critical neurovascular structures, discovering predictive biomarkers in chordoma has been a significant research effort because it may potentially reduce risky therapies in patients with less aggressive tumors. In response, because cyclin E1 overexpression correlates with patient prognosis in several malignancies, we investigated its expression in chordoma and whether it informs patient prognosis.MethodsSeventy-five chordoma patient specimens were enrolled in a tissue microarray (TMA) to evaluate cyclin E1 expression via immunohistochemical staining. Western blot was used to assess cyclin E1 expression in chordoma cell lines and fresh tissues. We then correlated cyclin E1 staining intensity in the TMA to clinicopathological features and chordoma patient outcomes.ResultsSixty-three percent of the chordoma patient specimens in the TMA, fifty-six percent of the fresh chordoma tissues, and all chordoma cell lines showed high cyclin E1 expression. In TMA analysis, cyclin E1 expression positively correlated to chordoma patient disease status. By survival analysis, high cyclin E1 expression was an independent prognostic risk factor for chordoma patients along with advanced disease status and positive surgical margin.ConclusionCyclin E1 is a promising biomarker predicting chordoma patient prognosis.

Background: Ataxia-telangiectasia and Rad3 related protein kinase (ATR) is an essential regulator of the DNA damage response in various cancers; however, its expression and roles in osteosarcoma are unclear. We therefore chose to evaluate the significance and mechanism of ATR in metastatic osteosarcoma, as well as its potential to be a therapeutic target. Methods: The osteosarcoma tissue microarrays constructed from 70 patient specimens underwent immunohistochemistry to quantify ATR and activated phospho-ATR (pATR) expression and their correlation with clinical outcomes. ATR sublocalization within the metastatic osteosarcoma cells was confirmed by immunofluorescence assay. Cell proliferation, apoptosis, and migration were evaluated following treatment with ATR siRNA or the selective inhibitor Berzosertib. Antitumor effects were determined with ex vivo three-dimensional (3D) culture models, and the impacts on the DNA damage repair pathways were measured with Western blotting. Results: Elevated ATR and activated pATR expression correlated with shorter patient survival and less necrosis following neoadjuvant chemotherapy. Intranuclear sublocalization of ATR and pATR suggested a mechanism related to DNA replication. ATR knockdown with siRNA or inhibition with Berzosertib suppressed cell proliferation in a time- and dose-dependent manner and induced apoptosis. In addition, ATR inhibition decreased Chk1 phosphorylation while increasing γH 2 AX expression and PARP cleavage, consistent with the interference of DNA damage repair. The ATR inhibitor Berzosertib also produced the characteristic cytoplasmic vacuolization preceding cell death, and suppressed ex vivo 3D spheroid formation and cell motility. Conclusion: The faithful dependence of cells on ATR signaling for survival and progression makes it an emerging therapeutic target in metastatic osteosarcoma.

Background/Aims: Metastasis is the major cause of death in patients with osteosarcoma. There is an urgent need to identify molecular markers that promote metastasis. Cluster of differentiation 44 is a receptor for hyaluronic acid (HA) and HA-binding has been proven to participate in various biological tumor activities, including tumor progression and metastasis. Methods: We performed a meta-analysis to investigate the relationship between CD44 expression, survival, and metastasis in patients with osteosarcoma. We then utilized the CRISPR-Cas9 system to specifically silence CD44 in highly metastatic human osteosarcoma cells (MNNG/HOS and 143B) and further determined the functional effects of CD44 knockout in these cells. Results: The meta-analysis demonstrated that a high level of CD44 may predict poor survival and higher potential of metastasis in patients with osteosarcoma. The expression of CD44 in highly metastatic human osteosarcoma cell lines was efficiently blocked by CRISPR-Cas9. When CD44 was silenced, the proliferation and spheroid formation of these osteosarcoma cells was inhibited under 3-D culture conditions. Furthermore, the migratory and invasive functions were also impaired in these highly metastatic osteosarcoma cells. Conclusion: These results suggest that developing new strategies to target CD44 in osteosarcoma may prevent metastasis and improve the clinical outcome of osteosarcoma patients.

Abstract Chondrosarcoma (CS) is a rare cancer, but it is the second most common primary malignant bone tumor and highly resistant to conventional chemotherapy and radiotherapy. Aberrant DNA methylation in the promoter CpG island of Wnt inhibitory factor 1 (WIF1) has been observed in different cancers. However, no studies have shown the relationship between WIF1 methylation and CS. In this study, we found promoter methylated WIF1 in both CS cell lines (CS-1 and SW1353) and tumor tissues. Western blot analysis confirmed loss WIF1 expression and activation of Wnt pathway proteins (Wnt5a/b, LRP6, and Dvl2). We subsequently examined the correlation between levels of WIF1 methylation and overall survival (OS) and progression-free survival (PFS) in CS patient samples with a follow-up spanning 234 months (mean: 57.6 months). Kaplan-Meier survival curves and log-rank tests revealed that high levels of WIF1 methylation were associated with lower OS and PFS rates (p

Bone sarcomas are a collection of sporadic malignancies of mesenchymal origin. The most common subtypes include osteosarcoma, Ewing sarcoma, chondrosarcoma, and chordoma. Despite the use of aggressive treatment protocols consisting of extensive surgical resection, chemotherapy, and radiotherapy, outcomes have not significantly improved over the past few decades for osteosarcoma or Ewing sarcoma patients. In addition, chondrosarcoma and chordoma are resistant to both chemotherapy and radiation therapy. There is, therefore, an urgent need to elucidate which novel new therapies may affect bone sarcomas. Emerging checkpoint inhibitors have generated considerable attention for their clinical success in a variety of human cancers, which has led to works assessing their potential in bone sarcoma management. Here, we review the recent advances of anti-PD-1/PD-L1 and anti-CTLA-4 blockade as well as other promising new immune checkpoint targets for their use in bone sarcoma therapy. Keywords: Immune checkpoint, Immunotherapy, Bone sarcoma, Anti-PD-1/PD-L1, Anti-CTLA-4

Background. Dedifferentiated chondrosarcomas (DDCSs) are highly malignant tumors with a dismal prognosis and present a significant challenge in clinical management. Methods. In an IRB approved retrospective protocol, we identified 72 patients with DDCS treated at our institution between 1993 and 2017 and reviewed clinicopathological characteristics, treatment modalities, and outcomes to analyze prognostic factors. Results. Femur (44.4%), pelvis (22.2%), and humerus (12.5%) were most commonly involved sites. Twenty-three patients (31.9%) presented with distant metastasis, and 3 (4.2%) of them also had regional lymph node involvement. The median overall survival (OS) was 13.9 months. On multivariate analysis, pathological fracture, larger tumor size, lymph node involvement, metastasis at diagnosis, extraosseous extension, and undifferentiated pleomorphic sarcoma component correlated with worse OS, whereas surgical resection and chemotherapy were associated with improved OS. For progression-free survival (PFS), pathological fracture and metastasis at diagnosis showed increased risk, while chemotherapy was associated with decreased risk. Among patients who received chemotherapy, doxorubicin and cisplatin were significantly associated with improved PFS but not OS. Among patients without metastasis at diagnosis, 17 (34.7%) developed local recurrence. Thirty-one (63.3%) developed distant metastases at a median interval of 18.1 months. On multivariate analysis, R1/R2 resection was related with local recurrence, while macroscopic dedifferentiated component was associated with distant metastasis. Conclusions. The prognosis of DDCS is poor. Complete resection remains a significant prognostic factor for local control. Chemotherapy with doxorubicin and cisplatin seems to have better PFS. More prognostic, multicenter trials are warranted to further explore the effectiveness of chemotherapy in selected DDCS patients.

Background. The Musculoskeletal Tumor Society (MSTS) scoring system measures function and is commonly used but criticized because it was developed to be completed by the clinician and not by the patient. We therefore evaluated if there is a difference between patient and clinician reported function using the MSTS score. Methods. 128 patients with bone metastasis of the lower (n=100) and upper (n=28) extremity completed the MSTS score. The MSTS score consists of six domains, scored on a 0 to 5 scale and transformed into an overall score ranging from 0 to 100% with a higher score indicating better function. The MSTS score was also derived from clinicians’ reports in the medical record. Results. The median age was 63 years (interquartile range [IQR]: 55–71) and the study included 74 (58%) women. We found that the clinicians’ MSTS score (median: 65, IQR: 49–83) overestimated the function as compared to the patient perceived score (median: 57, IQR: 40–70) by 8 points (p

Chordoma is a rare, slow-growing malignant tumor arising from notochordal remnants. A retrospective review of patient records at two major referral centers was undertaken to assess the incidence, location, and prognostic factors of metastatic disease from chordoma. 219 patients with chordoma (1962–2009) were identified. 39 patients (17.8%) developed metastatic disease, most frequently to lung (>50%). Median survival from the time of initial diagnosis was 130.4 months for patients who developed metastatic disease and 159.3 months for those who did not (P=0.05). Metastatic disease was most common in the youngest patients (P=0.07), and it was 2.5 times more frequent among patients with local recurrence (26.3%) than in those without (10.8%) (P=0.003). Patient survival with metastatic disease was highly variable, and it was dependent on both the location of the tumor primary and the site of metastasis. Metastasis to distal bone was the most rapid to develop and had the worst prognosis.

Rhabdomyosarcoma (RMS) is the most common soft tissue malignancy in childhood and adolescence. The two major histological subtypes of RMS are alveolar RMS, driven by the fusion protein PAX3-FKHR or PAX7-FKHR, and embryonic RMS, which is usually genetically heterogeneous. The prognosis of RMS has improved in the past several decades due to multidisciplinary care. However, in recent years, the treatment of patients with metastatic or refractory RMS has reached a plateau. Thus, to improve the survival rate of RMS patients and their overall well-being, further understanding of the molecular and cellular biology of RMS and identification of novel therapeutic targets are imperative. In this review, we describe the most recent discoveries in the molecular and cellular biology of RMS, including alterations in oncogenic pathways, miRNA (miR), in vivo models, stem cells, and important signal transduction cascades implicated in the development and progression of RMS. Furthermore, we discuss novel potential targeted therapies that may improve the current treatment of RMS.

Background and Objectives. Atypical lipomas are uncommon, slow-growing benign tumors. While surgery has been the primary treatment modality, we have managed some patients with radiation (RT) as a component of the treatment and have reported their outcomes in this study. Methods. A retrospective review of all cases of extremity and trunk atypical lipomas in The Sarcoma Database at the study institution was conducted. Results. Thirteen patients were identified. All patients underwent surgical resection at initial presentation and received pre- or postoperative radiation for subtotal resection (n=2), local recurrence (n=8), or progressive disease (n=3). The median total radiation dose was 50 Gy. Median followup was 65.1 months. All patients treated with RT remained free of disease at the last followup. No grade 3 or higher late toxicity from radiation was observed. No cases of tumor dedifferentiation occurred. Conclusion. For recurrent or residual atypical lipomas, a combination of reexcision and RT can provide long-term local control with acceptable morbidity. For recurrent tumors, pre-op RT of 50 Gy appears to be an effective and well-tolerated management approach.

Osteosarcoma (OS) is the most common primary malignant bone tumor, usually arising in the long bones of adolescents and young adults. While our knowledge of the molecular pathogenesis of OS has increased in recent years, we are still far from a comprehensive understanding of the molecular mechanisms of the disease, such as its tumorigenesis, specific mediators of disease progression, occurrence of chemoresistance, and development of metastasis. After the recent discovery of microRNAs (miRNAs), their critical roles in molecular biological processes have been of great interest in the cancer research field, including research on sarcomas. MiRNAs are highly conserved noncoding RNAs which play important roles as oncogenic or suppressive genes to simultaneously regulate multiple targets. Recent genome-wide screening using miRNA expression profiles has identified specific miRNA expression patterns that are associated with the biological and clinical properties of cancers. Additionally, miRNAs and their target genes or proteins can be potential novel biomarkers or therapeutic targets for cancer. However, there are several challenges that must be addressed in order to translate miRNA-based therapeutics to the clinical setting. In this review, we summarize the current understanding of the roles that miRNAs play in OS, and highlight their potential as biomarkers or therapeutic targets.