Metastasis-Initiating Osteosarcoma Subpopulations Establish Paracrine Interactions with Lung and Tumor Cells to Create a Metastatic Niche.

Osteosarcoma is an aggressive and deadly bone tumor, primarily afflicting children, adolescents, and young adults. Poor outcomes for osteosarcoma patients are intricately linked with the development of lung metastasis, which is responsible for nearly all deaths caused by osteosarcoma. Identification of the underlying cellular and molecular mechanisms that govern metastatic colonization of circulating tumor cells to the lung are needed to develop biologically defined, metastasis-targeting therapies.

MyoD is essential in rhabdomyosarcoma by promoting survival through differentiation and CYLD.

Rhabdomyosarcoma (RMS) is the most common soft tissue cancer among children, characterized by a skeletal muscle lineage that is impaired from undergoing terminal differentiation. NF-κB is constitutively active in cancer cells and plays a critical role in cell survival. Although NF-κB is also activated in RMS, surprisingly, we find that these tumors are far less dependent on NF-κB for their survival.

Local Control and Toxicity Outcomes After Stereotactic Body Radiation Therapy for Metastatic Osteosarcoma in Pediatric Patients.

Background: Pediatric osteosarcoma is an aggressive bone malignancy that presents significant challenges due to high rates of metastatic disease and relapse. It is often treated with palliative radiotherapy for symptom control, but achieving definitive local control (LC) with radiotherapy alone is challenging given its radioresistance. LC may be potentially improved by utilizing stereotactic body radiation therapy (SBRT) to deliver high biologically equivalent doses (BED).

Optimizing Ewing Sarcoma and Osteosarcoma Biopsy Acquisition: A Children's Oncology Group Bone Tumor Committee Consensus Statement.

Trends in diagnostic biopsy sample collection approaches for primary bone sarcomas have shifted in the past 2 decades. Although open/incisional biopsies used to be the predominant approach to obtain diagnostic material for Ewing sarcoma and osteosarcoma, image-guided core needle biopsies have increased in frequency and are safe for patients. These procedures are less invasive and reduce recovery times but have potential limitations.

Employing splice-switching oligonucleotides and AAVrh74.U7 snRNA to target insulin receptor splicing and cancer hallmarks in osteosarcoma.

Patients with osteosarcoma (OS), a debilitating pediatric bone malignancy, have limited treatment options to combat aggressive disease. OS thrives on insulin growth factor (IGF)-mediated signaling that can facilitate cell proliferation. Previous efforts to target IGF-1R signaling were mostly unsuccessful, likely due to compensatory signaling through alternative splicing of the insulin receptor () to the proliferative isoform.

Aberrant Activation of Wound-Healing Programs within the Metastatic Niche Facilitates Lung Colonization by Osteosarcoma Cells.

Purpose: Lung metastasis is responsible for nearly all deaths caused by osteosarcoma, the most common pediatric bone tumor. How malignant bone cells coerce the lung microenvironment to support metastatic growth is unclear. The purpose of this study is to identify metastasis-specific therapeutic vulnerabilities by delineating the cellular and molecular mechanisms underlying osteosarcoma lung metastatic niche formation.

ReNeu: A Pivotal, Phase IIb Trial of Mirdametinib in Adults and Children With Symptomatic Neurofibromatosis Type 1-Associated Plexiform Neurofibroma.

Purpose: Pharmacologic therapies for neurofibromatosis type 1-associated plexiform neurofibromas (NF1-PNs) are limited; currently, none are US Food and Drug Administration-approved for adults.

Methods: ReNeu is an open-label, multicenter, pivotal, phase IIb trial of mirdametinib in 58 adults (≥18 years of age) and 56 children (2 to 17 years of age) with NF1-PN causing significant morbidities. Patients received mirdametinib capsules or tablets for oral suspension (2 mg/m twice daily, maximum 4 mg twice daily), regardless of food intake, in 3 weeks on/1 week off 28-day cycles.

Treatment with novel topoisomerase inhibitors in Ewing sarcoma models reveals heterogeneity of tumor response.

Introduction: The topoisomerase 1 (TOP1) inhibitor irinotecan is a standard-of-care agent for relapsed Ewing sarcoma (EWS), but its efficacy is limited by chemical instability, rapid clearance and reversibility, and dose-limiting toxicities, such as diarrhea. Indenoisoquinolines (IIQs) represent a new class of clinical TOP1 inhibitors designed to address these limitations.

Methods: In this study, we evaluated the preclinical efficacy of three IIQs (LMP400, LMP744, and LMP776) in relevant models of EWS.

Trabectedin promotes oncolytic virus antitumor efficacy, viral gene expression, and immune effector function in models of bone sarcoma.

We previously reported that the DNA alkylator and transcriptional-blocking chemotherapeutic agent trabectedin enhances oncolytic herpes simplex viroimmunotherapy in human sarcoma xenograft models, though the mechanism remained to be elucidated. Here we report trabectedin disrupts the intrinsic cellular antiviral response which increases viral transcript presence in the human tumor cells. We also extended our synergy findings to syngeneic murine sarcoma models, which are poorly susceptible to virus infection.

Disease Control and Toxicity Outcomes after Stereotactic Ablative Radiation Therapy for Recurrent and/or Metastatic Cancers in Young-Adult and Pediatric Patients.

Background: Pediatric patients with metastatic and/or recurrent solid tumors have poor survival outcomes despite standard-of-care systemic therapy. Stereotactic ablative radiation therapy (SABR) may improve tumor control. We report the outcomes with the use of SABR in our pediatric solid tumor population.

Trabectedin Enhances Oncolytic Virotherapy by Reducing Barriers to Virus Spread and Cytotoxic Immunity in Preclinical Pediatric Bone Sarcoma.

We previously reported that the DNA alkylator and transcriptional-blocking chemotherapeutic agent trabectedin enhances oncolytic herpes simplex viroimmunotherapy in human sarcoma xenograft models, though the mechanism remained to be elucidated. Here we report trabectedin disrupts the intrinsic cellular anti-viral response which increases viral transcript spread throughout the human tumor cells. We also extended our synergy findings to syngeneic murine sarcoma models, which are poorly susceptible to virus infection.

Aberrant activation of wound healing programs within the metastatic niche facilitates lung colonization by osteosarcoma cells.

Purpose: Lung metastasis is responsible for nearly all deaths caused by osteosarcoma, the most common pediatric bone tumor. How malignant bone cells coerce the lung microenvironment to support metastatic growth is unclear. The purpose of this study is to identify metastasis-specific therapeutic vulnerabilities by delineating the cellular and molecular mechanisms underlying osteosarcoma lung metastatic niche formation.

Osteosarcoma Multi-Omics Landscape and Subtypes.

Osteosarcoma (OS) is the most common primary bone malignancy that exhibits remarkable histologic diversity and genetic heterogeneity. The complex nature of osteosarcoma has confounded precise molecular categorization, prognosis, and prediction for this disease. In this study, we performed a comprehensive multiplatform analysis on 86 osteosarcoma tumors, including somatic copy-number alteration, gene expression and methylation, and identified three molecularly distinct and clinically relevant subtypes of osteosarcoma.

Host-derived growth factors drive ERK phosphorylation and MCL1 expression to promote osteosarcoma cell survival during metastatic lung colonization.

Purpose: For patients with osteosarcoma, disease-related mortality most often results from lung metastasis-a phenomenon shared with many solid tumors. While established metastatic lesions behave aggressively, very few of the tumor cells that reach the lung will survive. By identifying mechanisms that facilitate survival of disseminated tumor cells, we can develop therapeutic strategies that prevent and treat metastasis.

Oncolytic virus-driven immune remodeling revealed in mouse medulloblastomas at single cell resolution.

Oncolytic viruses, modified for tumor-restricted infection, are a promising cancer immunotherapeutic, yet much remains to be understood about factors driving their activity and outcome in the tumor microenvironment. Here, we report that oncolytic herpes simplex virus C134, previously found to exert T cell-dependent efficacy in mouse models of glioblastoma, exerts T cell-independent efficacy in mouse models of medulloblastoma, indicating this oncolytic virus uses different mechanisms in different tumors. We investigated C134's behavior in mouse medulloblastomas, using single cell RNA sequencing to map C134-induced gene expression changes across cell types, timepoints, and medulloblastoma subgroup models at whole-transcriptome resolution.

Osteosarcoma tumors maintain intra-tumoral transcriptional heterogeneity during bone and lung colonization.

Background: Tumors are complex tissues containing collections of phenotypically diverse malignant and nonmalignant cells. We know little of the mechanisms that govern heterogeneity of tumor cells nor of the role heterogeneity plays in overcoming stresses, such as adaptation to different microenvironments. Osteosarcoma is an ideal model for studying these mechanisms-it exhibits widespread inter- and intra-tumoral heterogeneity, predictable patterns of metastasis, and a lack of clear targetable driver mutations.

Structurally Complex Osteosarcoma Genomes Exhibit Limited Heterogeneity within Individual Tumors and across Evolutionary Time.

Unlabelled: Osteosarcoma is an aggressive malignancy characterized by high genomic complexity. Identification of few recurrent mutations in protein coding genes suggests that somatic copy-number aberrations (SCNA) are the genetic drivers of disease. Models around genomic instability conflict-it is unclear whether osteosarcomas result from pervasive ongoing clonal evolution with continuous optimization of the fitness landscape or an early catastrophic event followed by stable maintenance of an abnormal genome.

Redundant Signaling as the Predominant Mechanism for Resistance to Antibodies Targeting the Type-I Insulin-Like Growth Factor Receptor in Cells Derived from Childhood Sarcoma.

Antibodies targeting insulin-like growth factor 1 receptor (IGF-1R) induce objective responses in only 5% to 15% of children with sarcoma. Understanding the mechanisms of resistance may identify combination therapies that optimize efficacy of IGF-1R-targeted antibodies. Sensitivity to the IGF-1R-targeting antibody TZ-1 was determined in rhabdomyosarcoma and Ewing sarcoma cell lines.

Osteosarcoma.

Osteosarcoma is the most common primary malignant tumour of the bone. Osteosarcoma incidence is bimodal, peaking at 18 and 60 years of age, and is slightly more common in males. The key pathophysiological mechanism involves several possible genetic drivers of disease linked to bone formation, causing malignant progression and metastasis.

An international working group consensus report for the prioritization of molecular biomarkers for Ewing sarcoma.

The advent of dose intensified interval compressed therapy has improved event-free survival for patients with localized Ewing sarcoma (EwS) to 78% at 5 years. However, nearly a quarter of patients with localized tumors and 60-80% of patients with metastatic tumors suffer relapse and die of disease. In addition, those who survive are often left with debilitating late effects.

Lurbinectedin Inhibits the EWS-WT1 Transcription Factor in Desmoplastic Small Round Cell Tumor.

Desmoplastic small round cell tumor (DSRCT) is a rare pediatric sarcoma with poor overall survival. This tumor is absolutely dependent on the continued expression and activity of its defining molecular lesion, the EWS-WT1 transcription factor. Unfortunately, the therapeutic targeting of transcription factors is challenging, and there is a critical need to identify compounds that inhibit EWS-WT1.