Bone Tumor In Children Research Articles

Physeal distraction prior to excision of metaphyseal malignant bone tumors in children: Preserving joint function and limb growth

BackgroundImprovements in imaging methods and adjuvant chemotherapy have increased survival rates in children with bone sarcomas up to 80%, therefore long-lasting limb salvage procedures are needed. PurposeTo describe a case series of pediatric patients who have undergone physeal distraction prior to tumor resection for treatment of metaphyseal malignant bone tumors. MethodsBetween January 2007 to December 2020, 8 patients (5 boys and 3 girls) with a mean age of 7.2 years (2–13), underwent physeal distraction as the first stage of a tumor resection protocol. Six patients had Ewing's sarcoma and two had osteosarcoma. Tumor locations were: proximal tibia (4 cases), distal femur, proximal humerus, distal radius, and distal fibula (1 case each). The affected bones were replaced with cadaver allograft in 6 patients; there was also one fibula autograft and one vascularized fibula graft. Chemotherapy was administered pre- and post-surgery; one patient received adjuvant radiotherapy. Average follow-up was 62.6 months (8–152). ResultsPhyseal distraction lasted an average of 10.6 days (3–15); delay to definitive resection was 17 days (range 13–22). Mean length of resection was 10.7 ​cm (range 5–14) and all had negative margins. There were no local recurrences. Three patients suffered disease progression with metastasis and died. Surgical complications included: pin infection (1 patient), surgical site infection (2 patients), allograft fracture (1 patient), and nonunion of the diaphyseal junction (3 patients). Final lower limb length discrepancy was 1.5 ​cm (range 1–2 ​cm). Normal joint function was achieved in 6 patients. The mean MSTS score was 75% (53%–97%). ConclusionsPhyseal distraction technique is an oncologically safe limb salvage procedure with good functional results, and it should be considered in the treatment of metaphyseal pediatric malignant tumors.

Development and validation of a novel necroptosis-related gene signature for predicting prognosis and therapeutic response in Ewing sarcoma.

Ewing sarcoma (ES) is the second most common malignant bone tumor in children and has a poor prognosis due to early metastasis and easy recurrence. Necroptosis is a newly discovered cell death method, and its critical role in tumor immunity and therapy has attracted widespread attention. Thus, the emergence of necroptosis may provide bright prospects for the treatment of ES and deserves our further study. Here, based on the random forest algorithm, we identified 6 key necroptosis-related genes (NRGs) and used them to construct an NRG signature with excellent predictive performance. Subsequent analysis showed that NRGs were closely associated with ES tumor immunity, and the signature was also good at predicting immunotherapy and chemotherapy response. Next, a comprehensive analysis of key genes showed that RIPK1, JAK1, and CHMP7 were potential therapeutic targets. The Cancer Dependency Map (DepMap) results showed that CHMP7 is associated with ES cell growth, and the Gene Set Cancer Analysis (GSCALite) results revealed that the JAK1 mutation frequency was the highest. The expression of 3 genes was all negatively correlated with methylation and positively with copy number variation (CNV). Finally, an accurate nomogram was constructed with this signature and clinical traits. In short, this study constructed an accurate prognostic signature and identified 3 novel therapeutic targets against ES.

Cracking the code: Deciphering the role of the tumor microenvironment in osteosarcoma metastasis

Osteosarcoma (OS) is the most common malignant bone tumor in children and adolescents. It is characterized by a rapid progression, poor prognosis, and early pulmonary metastasis. Over the past 30 years, approximately 85% of patients with osteosarcoma have experienced metastasis. The five-year survival of patients with lung metastasis during the early stages of treatment is less than 20%. The tumor microenvironment (TME) not only provides conditions for tumor cell growth but also releases a variety of substances that can promote the metastasis of tumor cells to other tissues and organs. Currently, there is limited research on the role of the TME in osteosarcoma metastasis. Therefore, to explore methods for regulating osteosarcoma metastasis, further investigations must be conducted from the perspective of the TME. This will help to identify new potential biomarkers for predicting osteosarcoma metastasis and assist in the discovery of new drugs that target regulatory mechanisms for clinical diagnosis and treatment. This paper reviews the research progress on the mechanism of osteosarcoma metastasis based on TME theory, which will provide guidance for the clinical treatment of osteosarcoma.

MYC regulates CSF1 expression via microRNA 17/20a to modulate tumor-associated macrophages in osteosarcoma.

Osteosarcoma (OS) is the most common primary bone tumor of childhood. Approximately 20%-30% of OSs carry amplification of chromosome 8q24, which harbors the oncogene c-MYC and correlates with a poor prognosis. To understand the mechanisms that underlie the ability of MYC to alter both the tumor and its surrounding tumor microenvironment (TME), we generated and molecularly characterized an osteoblast-specific Cre-Lox-Stop-Lox-c-MycT58A p53fl/+ knockin genetically engineered mouse model (GEMM). Phenotypically, the Myc-knockin GEMM had rapid tumor development with a high incidence of metastasis. MYC-dependent gene signatures in our murine model demonstrated significant homology to the human hyperactivated MYC OS. We established that hyperactivation of MYC led to an immune-depleted TME in OS demonstrated by the reduced number of leukocytes, particularly macrophages. MYC hyperactivation led to the downregulation of macrophage colony-stimulating factor 1, through increased microRNA 17/20a expression, causing a reduction of macrophage population in the TME of OS. Furthermore, we developed cell lines from the GEMM tumors, including a degradation tag-MYC model system, which validated our MYC-dependent findings both in vitro and in vivo. Our studies utilized innovative and clinically relevant models to identify a potentially novel molecular mechanism through which MYC regulates the profile and function of the OS immune landscape.

Rewiring innate and adaptive immunity with TLR9 agonist to treat osteosarcoma

BackgroundOsteosarcoma (OS) is the most common primary bone tumor in children and adolescent. Surgery and multidrug chemotherapy are the standard of treatment achieving 60–70% of event-free survival for localized disease at diagnosis. However, for metastatic disease, the prognosis is dismal. Exploiting immune system activation in the setting of such unfavorable mesenchymal tumors represents a new therapeutic challenge.MethodsIn immune competent OS mouse models bearing two contralateral lesions, we tested the efficacy of intralesional administration of a TLR9 agonist against the treated and not treated contralateral lesion evaluating abscopal effect. Multiparametric flow cytometry was used to evaluate changes of the tumor immune microenviroment. Experiments in immune-deficient mice allowed the investigation of the role of adaptive T cells in TLR9 agonist effects, while T cell receptor sequencing was used to assess the expansion of specific T cell clones.ResultsTLR9 agonist strongly impaired the growth of locally-treated tumors and its therapeutic effect also extended to the contralateral, untreated lesion. Multiparametric flow cytometry showed conspicuous changes in the immune landscape of the OS immune microenvironment upon TLR9 engagement, involving a reduction in M2-like macrophages, paralleled by increased infiltration of dendritic cells and activated CD8 T cells in both lesions. Remarkably, CD8 T cells were needed for the induction of the abscopal effect, whereas they were not strictly necessary for halting the growth of the treated lesion. T cell receptor (TCR) sequencing of tumor infiltrating CD8 T cells showed the expansion of specific TCR clones in the treated tumors and, remarkably, their selected representation in the contralateral untreated lesions, providing the first evidence of the rewiring of tumor-associated T cell clonal architectures.ConclusionsOverall these data indicate that the TLR9 agonist acts as an in situ anti-tumor vaccine, activating an innate immune response sufficient to suppress local tumor growth while inducing a systemic adaptive immunity with selective expansion of CD8 T cell clones, which are needed for the abscopal effect.Graphical

The Diagnosis and Treatment of Osteosarcoma and Ewing's Sarcoma in Children and Adolescents.

Osteosarcoma and Ewing's sarcoma in children and adolescents require age-specific interdisciplinary diagnosis and treatment to achieve optimal therapeutic outcomes. The diagnosis and treatment of malignant bone tumors in childhood and adolescence are presented in the light of publications retrieved by a selective search, pertinent guidelines, and the authors' extensive experience in an interdisciplinary cancer center. Bone sarcomas make up approximately 5% of all malignancies in children and adolescents; the most common types are Ewing's sarcoma and osteosarcoma. Patients are often not referred to a specialized center until long after the onset of symptoms, as they and their physicians rarely consider the possibility of a bone tumor, and the symptoms are often trivialized. Bone pain of unknown origin, swelling, and functional limitations should be investigated with conventional x-rays. Lesions of unclear origin should be biopsied after a meticulous clinical and radiologic evaluation. Multimodal treatment consists of neo - adjuvant chemotherapy, limb-preserving resection if possible, and radiotherapy where indicated. In multicenter studies, patients with osteosarcoma achieve event-free survival in 64% of cases if their disease is localized, and 28% if it is metastatic; the corresponding figures for patients with Ewing's sarcoma are 80% and 27%, respectively. With implementation of the current treatment recommendations, most children and adolescents with malignant bone tumors can be treated successfully with curative intent. These patients should be referred to a sarcoma center for diagnosis and treatment.

Epigenetic Changes Associated with Osteosarcoma: A Comprehensive Review.

Osteosarcoma is the most common malignant primary bone tumor in children and adolescents. While clinical outcomes have improved, the 5-year survival rate is only around 60% if discovered early and can require debilitating treatments, such as amputations. A better understanding of the disease could lead to better clinical outcomes for patients with osteosarcoma. One promising avenue of osteosarcoma research is in the field of epigenetics. This research investigates changes in genetic expression that occur above the genome rather than in the genetic code itself. The epigenetics of osteosarcoma is an active area of research that is still not fully understood. In a narrative review, we examine recent advances in the epigenetics of osteosarcoma by reporting biomarkers of DNA methylation, histone modifications, and non-coding RNA associated with disease progression. We also show how cancer tumor epigenetic profiles are being used to predict and improve patient outcomes. The papers in this review cover a large range of epigenetic target genes and pathways that modulate many aspects of osteosarcoma, including but not limited to metastases and chemotherapy resistance. Ultimately, this review will shed light on the recent advances in the epigenetics of osteosarcoma and illustrate the clinical benefits of this field of research.

Effect of dual properties of regorafenib in osteosarcoma on tumor progression and bone parameters in mouse preclinical models.

e23501 Background: Osteosarcoma (OS) constitutes the most frequent malignant primary bone tumor in children and young adults. Actual treatments in OS are based in a multimodal therapy that combines pre- and post-surgery polychemotherapies including cisplatin, doxorubicin, ifosfamide and/or methotrexate. Regardless the use of this polychemotherapeutic approach, the five years overall survival for patients has not improved during the last four decades and there is a clinical need to identify new active drugs in OS. An interesting strategy implies the use of compounds that showed therapeutic benefits in other solid tumors. Regorafenib, a small molecule with multi-target tyrosine kinase inhibitory activity against FGFR-1 and -2, KIT, PDGFR, RAF, RET, TIE2 and VEGFR-1, -2 and -3, showed an anti-angiogenic/oncogenic properties in various solid tumors that includes metastatic colorectal cancer, hepatocarcinoma and breast cancer. In addition, regorafenib also inhibits in vitro the proliferation of several pediatric solid tumor cell lines such as rhabdomyosarcoma, Ewing sarcoma and OS. Methods: The present work aims to decipher the in vitro and in vivo effects of regorafenib in OS preclinical models. Results: The treatment of MNNG-HOS, KHOS and 143B osteosarcoma cell lines with Regorafenib resulted in the inhibition of cell proliferation in a dose dependent manner. The gene expression profiles of MNNG-HOS and 143B cells treated or not with regorafenib and analyzed by NanoString technology revealed a specific regulation of molecular pathways by regorafenib in both cell lines. The in vivo effect of regorafenib was then analyzed in immunocompetent (mouse MOS-J cells inoculated in C57Bl/6 mice) and immunodeficient (human MNNG-HOS and 143B OS cells injected in Nude mice) murine osteosarcoma models. In all the cases, a significant reduction of primary tumor growth was observed as well as a significant decrease of lung metastases compared to untreated mice. Interestingly, the cortical and trabecular bone mineral density were significantly increased in regorafenib treated mice compared to untreated groups as demonstrated by X ray microtomodensitometry in all models. Conclusions: Our results support the use of regorafenib as an alternative treatment in metastatic OS and demonstrated for the first time the its bone protective effect.

Identifying osteosarcoma signatures in cell free DNA using 5-hydroxymethylcytosine profiling.

10022 Background: Osteosarcoma is the most common primary bone tumor in children and adolescents. Prognostic biomarkers are limited, and post-treatment surveillance relies heavily on radiologic imaging. Capture and analysis of cell-free DNA (cfDNA) from the bloodstream is an emerging technique that could be used to provide additional prognostic information and track residual disease following treatment. 5-hydroxymethylcytosine (5-hmC) is an epigenetic marker of open chromatin and active gene expression, and tumor specific patterns of global 5-hmC deposition are identifiable in several cancers and vary according to disease burden. We profiled 5-hmC using plasma-derived cfDNA from osteosarcoma patients and healthy children to assess its utility as a biomarker of disease status. Methods: cfDNA was isolated from patients diagnosed with osteosarcoma and well child controls. Nano-hmC-Seal, a technique developed to isolate 5-hmC-modified DNA fragments, was used to generate sequencing libraries of cfDNA. Genomic DNA from osteosarcoma cell lines was serially diluted with healthy donor-derived cfDNA. DESeq2 was used to identify genes with high 5-hmC deposition in osteosarcoma cell line DNA relative to serial dilutions. In patient cfDNA samples, the relative abundance of 5-hmC deposition on these osteosarcoma genes was determined using gene set variation analysis (GSVA). GSVA returns a score ranging from -1 to 1, with positive values indicating a relative abundance of 5-hmC deposition on osteosarcoma genes. Results: The cohort consisted of 33 healthy children and 17 patients with osteosarcoma including 53 serially collected samples from these patients. 139 osteosarcoma genes were identified and used for GSVA analysis. Patients with osteosarcoma had significantly higher GSVA scores than well children (0.26 vs -0.38; p < 0.001). Hierarchal clustering identified two clusters of samples from children with osteosarcoma. Cluster 1 contained samples with scores correlating with osteosarcoma-derived DNA compared to Cluster 2 (0.14 vs -0.18; p < 0.001). Furthermore, Cluster 1 contained 17 of 23 samples from patients with active disease on clinical imaging (sensitivity = 74%, specificity = 57%). High 5-hmC deposition on MYC was readily identified in one sample obtained at diagnosis from the only patient with a MYC amplified tumor. Additional samples from this patient during treatment showed decreasing 5-hmC deposition on MYC, consistent with a treated tumor shedding less DNA into the blood. Additionally, decreased disease burden following surgical resection was identifiable in 5-hmC profiles (presurgical GSVA score 0.22 vs postsurgical -0.08; p = 0.004). Conclusions: Osteosarcoma 5-hmC signatures can identify patients with active disease. Monitoring cfDNA in osteosarcoma using 5-hmC profiling is a promising technique that warrants further investigation with larger patient cohorts.

Health disparities among patients with Ewing sarcoma in Florida.

e18549 Background: Ewing sarcoma (ES) is the second most common malignant bone tumor in children and young adults. Although usually localized, subclinical metastatic disease is often present. Treatment includes multi-agent chemotherapy with surgery or radiation for local control. Though overall survival (OS) has improved to 70% for localized disease, mortality from recurrent or metastatic disease remains high. Although, ES is most common among Non-Hispanic White adolescent males, prior population-based ES studies utilizing Surveillance, Epidemiology, and End Results (SEER) have shown increased mortality among White Hispanics, Blacks, and those of low socioeconomic status (SES). Florida is not part of SEER but is home to a unique population with high proportions of immigrants and Hispanics of distinct backgrounds including Cubans, Puerto Ricans, and South Americans that contrasts to the Mexican Hispanic majority in other US states. As there are no prior population-based studies examining ES in Florida, the role of racial/ethnic disparities on outcomes among this diverse patient population remains unknown. By utilizing the Florida Cancer Data System (FCDS) for ES patients, this study will assess overall racial/ethnic disparities, evaluate the impact of racial/ethnic disparities on OS, and compare ES incidence rates in Florida with national SEER-21 rates to assess risk. Methods: This retrospective secondary analysis examined all patients diagnosed with ES (2005-2018) in Florida (n = 411) and SEER-21 (n = 1,513). Age-adjusted incidence (AAI) with 95% confidence interval (95%CI) was analyzed for the entire group and OS was estimated using Kaplan-Meier survival analysis. Univariable and multivariable analyses using Cox regression models were performed for variables of interest—race/ethnicity, age, sex, year of diagnosis, site of disease, staging, SES, and insurance type. Adjusted hazard ratio (aHR) with 95%CI were calculated. Results: Per the FCDS, there was a higher incidence of ES in Hispanic males (AAI 2.6; 95%CI: 2.0-3.2 per 1,000,000; n = 84) as compared to the SEER (1.2; 1.1-1.4; n = 250). Among non-metastatic ES, Hispanics had an increased risk for cancer-related mortality compared to Non-Hispanic Whites (aHR 2.9; 95%CI: 1.46-5.74; p =0.002), after adjusting for all other variables. In the full model (all cases regardless of stage at diagnosis), older age and distant metastasis were statistically significant factors for poor OS while SES and insurance status were not. Conclusions: Hispanics in Florida are of interest for ES with a higher-than-expected incidence compared to the US and remarkably worse survival for non-metastatic disease compared to Non-Hispanic Whites. Further in-depth studies are needed to examine why this disparity exists, but it is potentially multifactorial. This is the first known study for ES health disparities in Florida and provides updated national data for comparison.

Overall survival comparison between pediatric and adult Ewing sarcoma of bone and adult nomogram construction: a large population-based analysis.

Ewing sarcoma (ES) is a common primary bone tumor in children. Our study aimed to compare overall survival (OS) between pediatric and adult bone ES patients, identify independent prognostic factors and develop a nomogram for predicting OS in adult patients with ES of bone. We retrospectively analyzed data for the 2004-2015 period from the Surveillance, Epidemiology, and End Results (SEER) database. To guarantee well-balanced characteristics between the comparison groups, propensity score matching (PSM) was used. Kaplan-Meier (KM) curves were used to compare OS between pediatric and adult patients with ES of bone. Univariate and multivariate Cox regression analyses were used to screen independent prognostic factors for ES of bone, and a prognostic nomogram was constructed by using the factors identified. The prediction accuracy and clinical benefit were evaluated using receiver operating characteristic (ROC) curves, areas under the curves (AUCs), calibration curves, and decision curve analysis (DCA). Our results showed that adult ES patients had lower OS than younger ES patients. Age, surgery, chemotherapy, and TNM stage were independent risk factors for bone ES in adults and were used to develop a nomogram. AUCs for 3-, 5-, and 10-year OS were 76.4 (67.5, 85.3), 77.3 (68.6, 85.9) and 76.6 (68.6, 84.5), respectively. Calibration curves and DCA results indicated excellent performance for our nomogram. We found that ES pediatric patients have better OS than adult ES patients, and we constructed a practical nomogram to predict the 3-, 5- and 10-year OS of adult patients with ES of bone based on independent prognostic factors (age, surgery, chemotherapy, T stage, N stage and M stage).

Unusual peritoneal metastases of femoral osteosarcoma

Introduction: Osteosarcoma is the most common malignant bone tumor in children, most often occurring in the lower extremity of the femur, and is known to be particularly aggressive, with a high risk of metastasis. The most frequent secondary localizations are pulmonary and bone metastases; peritoneal metastases are extremely rare and have a poor prognosis. Case Report: We report the case of a 14-year-old child with a history of a treated right femoral osteosarcoma, which presented with peritoneal and pulmonary metastases. Conclusion: Imaging plays a very important role in the management of patients with osteosarcoma, it allows an early detection of metastases through a rigorous clinicoradiological surveillance, metastases usually have the same radiological appearance as the primary tumor and the diagnosis of certainty is essentially based on anatomopathological study.

Ewing sarcoma

Ewing sarcoma, according to the latest 2020 WHO classification of tumors of bone and soft tissue, belongs to the category of “undifferentiated small round cell sarcomas of bone and soft tissue.” After osteosarcoma, it is the second most common malignant bone tumor in children and young adults. Most Ewing sarcomas develop in the bone and about 30% of soft tissues. In this paper, all the epidemiological, clinical and imaging characteristics will be reviewed.

Abstract LB329: A potent and selective small molecule inhibitor of CSF-1R ABSK021 demonstrates strong efficacy in preclinical models of osteosarcoma

Abstract Introduction: Osteosarcoma is the most common primary malignant bone tumor in children and young adults. Surgery combined with multimodal chemotherapy remains as the standard treatment for osteosarcoma patients. However, patients with osteosarcoma metastasis have a five-year survival rate of less than 30%, and their long-term outcomes have not improved over the last 30 years. CSF-1/CSF-1R signaling is crucial for the survival, function, proliferation and differentiation of myeloid lineage cells, including osteoclasts and monocytes/macrophages. Targeting CSF-1R either on tumor cells or tumor-associated macrophages has been reported to limit osteosarcoma progression in preclinical models. ABSK021, an oral, highly potent and selective small molecule inhibitor of CSF-1R discovered by Abbisko, has entered into Phase I trial (NCT04192344) and showed significant anti-tumor activity and favorable safety profile in patients with advanced tenosynovial giant cell tumor. Here, we conducted a series of preclinical in vitro and in vivo experiments, as well as human osteosarcoma profiling, to investigate the treatment potential of ABSK021 for osteosarcoma patients. Methods: Cellular potency of ABSK021 was evaluated by Celltiter-Glo assay in osteosarcoma cell lines and CSF-1R expression was evaluated by western blot. In vivo efficacy studies were conducted in murine osteosarcoma models and pharmacodynamics changes were measured. CSF-1R IHC staining was conducted in tissue microarray samples from osteosarcoma patients. Results: ABSK021 potently inhibited the proliferation of K7M2, a murine osteosarcoma cell line with high expression of CSF-1R. In animal, ABSK021 showed strong anti-tumor activity on K7M2 syngeneic model and SA4094 osteosarcoma PDX model without causing significant body weight loss. Pharmacodynamics analysis displayed robust inhibition of macrophage infiltration and CSF-1R signaling by ABSK021, confirming its effective target engagement in vivo. Parallel IHC analysis of human tissue microarray samples revealed high prevalence of positive CSF-1R staining in osteosarcoma patients. Conclusion: Taken together, these results demonstrate that ABSK021 has strong inhibition of CSF-1R activity and corresponding anti-tumor activity in preclinical osteosarcoma models. High prevalence of CSF-1R expression was also found in osteosarcoma patients, suggesting great potential of utilizing ABSK021 as a novel therapy to treat osteosarcoma patients in clinic. Citation Format: Nannan Zhang, Cheng Dai, Jiacheng Zhang, Shuqun Yang, Jie Wang, Jie Zhang, Manqi Liu, Zhui Chen. A potent and selective small molecule inhibitor of CSF-1R ABSK021 demonstrates strong efficacy in preclinical models of osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB329.

Abstract 6713: Myc-regulated miR17, 20a modulate RANK expression in osteosarcoma

Abstract Osteosarcoma (OS) is the most common primary bone tumor in children and adolescents. Approximately 25-30% of these tumors carry amplification of chromosome 8q24, which harbors the oncogene c-Myc, and correlates with a poor prognosis in patients with OS. To understand the mechanisms that underlie the ability of Myc to alter both the tumor and its surrounding tumor immune microenvironment (TiME), we generated and molecularly characterized an osteoblast-specific Cre-Lox-Stop-Lox;(LSL)-c-MycT58A;p53f/+ knockin genetically engineered mouse model (GEMM). Phenotypically, the Myc knockin-GEMM had rapid tumor development with a high incidence of metastasis. Myc-dependent gene signature in our murine model demonstrated significant homology to the human Myc-amplified OS.Interestingly, we noticed a significant reduction in the osteoclast (OCL) cell population in the Myc knockin OS tumor compared to the p53-driven. We found the expression of RANK was significantly downregulated in the Myc knockin tumor compared to the Non-knockin p53 heterozygous tumors. The RANK/RANKL pathway is vital in OCL maturation and bone modeling/remodeling. To understand the involvement of Myc in RANK regulation, we used murine-derived OS cell lines and transiently knocked down of Myc expression using siRNA. We observed a significant upregulation in RANK expression after Myc knockdown. To decipher the molecular mechanism behind the Myc-dependent regulation of RANK expression in OS, we looked into the Myc-mediated microRNAs. Myc regulates the expression of several microRNAs, including the polycistronic miR-17-92 cluster. The expression of miR17-5p and Mir20a-5p was significantly higher in the GEMM tumor tissue samples isolated from the Myc knockin compared to the p53-driven. Further, we validated the Myc-dependent regulation of miR-17-5p/20a-5p expression using transient knockdown of Myc in mouse Myc knockin-derived cell lines. To examine the role of miR17-5p/20a-5p on the RANK regulation, we performed both gain and loss-of-function studies using microRNA-17/20a mimics and inhibitors. After the treatment with miR-17-5p/20a-5p inhibitors, the expression of RANK was significantly upregulated whereas in the case of miR17/20a mimics reversed these effects and led to a downregulation of RANK expression. We established that miR-17-5p/20a-5p is causally responsible for at least part of the mechanism by which Myc regulates the RANK expression in OS.We concluded that the Myc-regulated miR17/20a modulates the RANK expression that is involved in the OCL cell population regulation and function in the OS. Citation Format: Bikesh Kumar Nirala, Lyazat Kurenbekova, Tajhal Patel, Ryan Lane Shuck, Atreyi Dasgupta, Nino Carlo Rainusso, Jason T. Yustein. Myc-regulated miR17, 20a modulate RANK expression in osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6713.

Abstract 1307: The effect of circulating CXCL10 on osteosarcoma metastasis using orthotopic xenograft mouse models

Abstract Osteosarcoma is the most common malignant bone tumor in children. Despite the use of chemotherapy and surgery, the survival of patients with metastasis is still dismal. We have previously reported that a high serum level of CXCL10 is associated with a poor prognosis and metastasis in osteosarcoma, suggesting that the chemokine may affect the development of metastasis. Nonetheless, the effect of endocrine signaling of CXCL10 is largely unknown. It is unclear if the prognostic effect of circulating CXCL10 is due to its metastasis-promoting effect or if CXCL10 is merely a biomarker. In this study, we employed orthotopic xenograft mouse models to examine the effect of circulating CXCL10 with respect to metastasis. We first injected luciferase-labeled 143B osteosarcoma cells into the tibia of NOD/SCID mice to generate an orthotopic xenograft mouse model. When the tumor was detectable by bioluminescence, we injected 1.5ug of CXCL10 protein or saline intravenously via the tail vein every day for two weeks. The development of pulmonary metastasis was monitored by bioluminescence. The mice were sacrificed at the endpoint when bioluminescence was detected in the lungs. The mouse lungs were then resected and examined by H&E staining for the detection of metastatic nodules. The mice in the experimental and control groups that developed lung metastases were compared. The results showed that no significant difference was observed between the two groups. The experiment was repeated one more time and similar results were observed. To investigate the influence of the cell line background, we analyzed another osteosarcoma cell line, MG63.3. No significant difference in metastasis development was observed between the mice injected with CXCL10 and the mice injected with saline. The results indicate that a higher level of circulating CXCL10 alone was not sufficient to promote pulmonary metastases in the orthotopic xenograft mouse models. We also showed that AKT phosphorylation was upregulated in the osteosarcoma cell lines incubated with CXCL10, ruling out that the CXCL10 protein used was biologically inactive. In summary, our results suggest that although an increased circulating level of CXCL10 is associated with a poor prognosis in osteosarcoma patients, it does not promote the development of pulmonary metastasis in xenograft mouse models. Circulating CXCL10 may only act as a prognostic biomarker, but not a metastatic driver. Alternatively, the CXCL10-CXCR3 axis may be necessary, but not sufficient, to cause metastasis. Citation Format: Xiang Chen, Margaret Clement, John Hicks, Tsz Kwong Man. The effect of circulating CXCL10 on osteosarcoma metastasis using orthotopic xenograft mouse models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1307.

Hereditary multiple exostosis: a case report and brief review regarding the risk of malignancy

Osteocartilaginous exostoses is the most common benign bone tumor of childhood whose predominant growth on cartilage with potential impact on bone development and architecture, with potential risk of fractures and installation of malignant neoplasms. We present a case of an 11 -year -old female child, admitted to the unit complained of pain in the proximal region of the left ulna and distal third of the ipsilateral tibia with evolution of one year and suspected hereditary multiple exostosis whose histopathological result was positive for osteochondroma. The conduct for this case consisted of surgical extraction of the bone mass and outpatient follow -up for the case of relevant angular deviation of limbs, fractures or emergence of neoplasia suspected of malignancy.

Pharmacogenetics of the Primary and Metastatic Osteosarcoma: Gene Expression Profile Associated with Outcome.

Osteosarcoma (OS) is the most common malignant bone tumor in children and adolescents. In recent decades, OS treatment has reached a plateau and drug resistance is still a major challenge. Therefore, the present study aimed to analyze the expression of the genes related to pharmacogenetics in OS. The expression of 32 target genes in 80 paired specimens (pre-chemotherapeutic primary tumor, post-chemotherapeutic primary tumor and pulmonary metastasis) obtained from 33 patients diagnosed with OS were analyzed by the real-time PCR methodology. As the calibrators (control), five normal bone specimens were used. The present study identified associations between the OS outcome and the expression of the genes TOP2A, DHFR, MTHFR, BCL2L1, CASP3, FASLG, GSTM3, SOD1, ABCC1, ABCC2, ABCC3, ABCC5, ABCC6, ABCC10, ABCC11, ABCG2, RALBP1, SLC19A1, SLC22A1, ERCC1 and MSH2. In addition, the expression of the ABCC10, GGH, GSTM3 and SLC22A1 genes were associated with the disease event, and the metastasis specimens showed a high expression profile of ABCC1, ABCC3 and ABCC4 genes and a low expression of SLC22A1 and ABCC10 genes, which is possibly an important factor for resistance in OS metastasis. Therefore, our findings may, in the future, contribute to clinical management as prognostic factors as well as possible therapeutic targets.

Follow-up of biological reconstruction of epiphysis preserving osteosarcoma around the knee in children: A retrospective cohort study.

Limb salvage treatment for malignant bone tumors in children includes prosthetic and biological reconstruction. Early function following prosthesis reconstruction is satisfactory; however, there are several complications. Biological reconstruction is another way to treat bone defects. We evaluated the effectiveness of reconstruction of bone defects by liquid nitrogen inactivation of autologous bone with preserving epiphysis in 5 cases of periarticular osteosarcoma of the knee. We retrospectively selected 5 patients with articular osteosarcoma of the knee who underwent epiphyseal-preserving biological reconstruction in our department between January 2019 and January 2020. Femur involvement occurred in 2 cases and tibia involvement occurred in 3 cases, with an average defect of 18 cm (12-30 cm). The 2 patients with femur involvement were treated with inactivated autologous bone by liquid nitrogen with vascularized fibula transplantation. Among the patients with tibia involvement, 2 were treated with inactivated autologous bone with ipsilateral vascularized fibula transplantation and 1 was treated with autologous inactivated bone with contralateral vascularized fibula transplantation. Bone healing was evaluated by regular X-ray examination. At the end of the follow-up, lower limb length, knee flexion, and extension function were evaluated. Patients were followed up for 24 to 36 months. Average bone-healing time was 5.2 months (3-8 months). All patients achieved bone healing with no tumor recurrence and no distant metastasis and all patients survived. The lengths of both lower limbs were equal in 2 cases, with shortening by ≤1 cm in 1 case and shortening by 2 cm in 1 case. Knee flexion was >90° in 4 cases and between 50 and 60° in 1 case. The Muscle and Skeletal Tumor Society score was 24.2 (range 20-26). Inactivation of autogenous bone with the epiphysis preserved by liquid nitrogen combined with vascularized fibula reconstruction for periarticular osteosarcoma of the knee in children is safe and effective. This technique supports bone healing. Postoperative limb length and function, and short-term effects were satisfactory.

Transfer of exosomal microRNAs confers doxorubicin resistance in osteosarcoma cells.

Osteosarcoma (OS) is the commonest primary malignant bone tumor in children and adolescents. However, chemotherapy resistance is a major challenge for the treatment of OS. Exosomes have been reported to serve an increasingly important role in different stages of tumor progression and chemotherapy resistance. The present study investigated whether exosomes derived from doxorubicin‑resistant OS cells (MG63/DXR) could be taken up in doxorubicin‑sensitive OS cells (MG63) and induce a doxorubicin‑resistant phenotype. MDR‑1, as the specific mRNA of chemoresistance, can be transferred by exosomes from MG63/DXR cells to MG63 cells. In addition, the present study identified 2,864 differentially expressed miRNAs (456 upregulated and 98 downregulated with fold‑change >2.0, P<5x10‑2, and FDR<0.05) in all three sets of exosomes from MG63/DXR cells and MG63 cells. The related miRNAs and pathways of exosomes involved in the doxorubicin resistance were identified by bioinformatic analysis. A total of 10 randomly selected exosomal miRNAs were dysregulated in exosomes from MG63/DXR cells relative to MG63 cells by reverse transcription‑quantitative PCR detection. As a result, miR‑143‑3p was found high expressed in exosomes from doxorubicin‑resistant OS cells compared with doxorubicin‑sensitive OS cells and upregulation of exosomal miR‑143‑3p abundance associated with the poor chemotherapeutic response to OS cells. Briefly, transfer of exosomal miR‑143‑3p confers doxorubicin resistance in osteosarcoma cells.