Osteosarcoma (OS) is the most frequent pediatric malignant bone tumor that has a high propensity for metastases. Through osteoblast-specific alteration of p53 status, we developed a genetically engineered mouse model of localized and metastatic OS to gain an understanding into the molecular pathogenesis of OS. Microarray analysis of both localized tumors and metastatic tumors identified the downregulation of the naked cuticle homolog 2 (NKD2) gene, a negative regulator of Wnt signaling. Overexpression of NKD2 in metastatic human and mouse OS cells significantly decreases cell proliferation, migration and invasion ability in vitro and drastically diminishes OS tumor growth and metastasis in vivo, whereas downregulation enhances migratory and invasive potential. Evaluation of NKD2-overexpressing tumors revealed upregulation of tumor-suppressor genes and downregulation of molecules involved in blood vessel formation and cell migration. Furthermore, assessment of primary human OS revealed downregulation of NKD2 in metastatic and recurrent OS. Finally, we provide biological evidence that use of small-molecule inhibitors targeting the Wnt pathway can have therapeutic efficacy in decreasing metastatic properties in OS. Our studies provide compelling evidence that downregulation of NKD2 expression and alterations in associated regulated pathways have a significant role in driving OS tumor growth and metastasis.

This clinical trial evaluated whether whole exome sequencing (WES) and RNA sequencing (RNAseq) of paired normal and tumor tissues could be incorporated into a personalized treatment plan for newly diagnosed patients (<25 years of age) with diffuse intrinsic pontine glioma (DIPG). Additionally, whole genome sequencing (WGS) was compared to WES to determine if WGS would further inform treatment decisions, and whether circulating tumor DNA (ctDNA) could detect the H3K27M mutation to allow assessment of therapy response. Patients were selected across three Pacific Pediatric Neuro‐Oncology Consortium member institutions between September 2014 and January 2016. WES and RNAseq were performed at diagnosis and recurrence when possible in a CLIA‐certified laboratory. Patient‐derived cell line development was attempted for each subject. Collection of blood for ctDNA was done prior to treatment and with each MRI. A specialized tumor board generated a treatment recommendation including up to four FDA‐approved agents based upon the genomic alterations detected. A treatment plan was successfully issued within 21 business days from tissue collection for all 15 subjects, with 14 of the 15 subjects fulfilling the feasibility criteria. WGS results did not significantly deviate from WES‐based therapy recommendations; however, WGS data provided further insight into tumor evolution and fidelity of patient‐derived cell models. Detection of the H3F3A or HIST1H3B K27M (H3K27M) mutation using ctDNA was successful in 92% of H3K27M mutant cases. A personalized treatment recommendation for DIPG can be rendered within a multicenter setting using comprehensive next‐generation sequencing technology in a clinically relevant timeframe.

Glioblastoma multiforme (GBM) is the most frequent primary brain tumor in adults with a 5-year survival rate of 5% despite intensive research efforts. The poor prognosis is due, in part, to aggressive invasion into the surrounding brain parenchyma. Invasion is a complex process mediated by cell-intrinsic pathways, extrinsic microenvironmental cues, and biophysical cues from the peritumoral stromal matrix. Recent data have attributed GBM invasion to the glioma stem-like cell (GSC) subpopulation. GSCs are slowly dividing, highly invasive, therapy resistant, and are considered to give rise to tumor recurrence. GSCs are localized in a heterogeneous cellular niche, and cross talk between stromal cells and GSCs cultivates a fertile environment that promotes GSC invasion. Pro-migratory soluble factors from endothelial cells, astrocytes, macrophages, microglia, and non-stem-like tumor cells can stimulate peritumoral invasion of GSCs. Therefore, therapeutic efforts designed to target the invasive GSCs may enhance patient survival. In this review, we summarize the current understanding of extrinsic pathways and major stromal and immune players facilitating GSC maintenance and survival.