Tumor-derived exosomes are emerging mediators of tumorigenesis with tissue-specific addresses and messages. We explored the function of melanoma-derived exosomes in the formation of primary tumor and metastases in mouse and human subjects. Exosomes from highly metastatic melanoma increased the metastatic behavior of primary tumors by permanently “educating” bone marrow (BM) progenitors via the MET receptor. Melanoma-derived exosomes also induced vascular leakiness at pre-metastatic sites, and reprogrammed BM progenitors towards a c-Kit+Tie2+Met+ pro-vasculogenic phenotype. Reducing Met expression in exosomes diminished the pro-metastatic behavior of BM cells. Importantly, MET expression was elevated in circulating CD45−C-KITlow/+TIE2+ BM progenitors from metastatic melanoma subjects. RAB1a, RAB5b, RAB7, and RAB27a were highly expressed in melanoma cells and Rab27a RNA interference decreased exosome production, preventing BM education, tumor growth and metastasis. Finally, we identified an exosome-specific “melanoma signature” with prognostic and therapeutic potential, comprised of TYRP2, VLA-4, HSP70, an HSP90 isoform and the MET oncoprotein.

The development of targeted anti-cancer therapies through the study of cancer genomes is intended to increase survival rates and decrease treatment-related toxicity. We treated a transposon–driven, functional genomic mouse model of medulloblastoma with ‘humanized’ in vivo therapy (microneurosurgical tumour resection followed by multi-fractionated, image-guided radiotherapy). Genetic events in recurrent murine medulloblastoma exhibit a very poor overlap with those in matched murine diagnostic samples (<5%). Whole-genome sequencing of 33 pairs of human diagnostic and post-therapy medulloblastomas demonstrated substantial genetic divergence of the dominant clone after therapy (<12% diagnostic events were retained at recurrence). In both mice and humans, the dominant clone at recurrence arose through clonal selection of a pre-existing minor clone present at diagnosis. Targeted therapy is unlikely to be effective in the absence of the target, therefore our results offer a simple, proximal, and remediable explanation for the failure of prior clinical trials of targeted therapy.

Medulloblastoma comprises four distinct molecular variants with distinct genetics, transcriptomes, and outcomes. Subgroup affiliation has been previously shown to remain stable at the time of recurrence, which likely reflects their distinct cells of origin. However, a therapeutically relevant question that remains unanswered is subgroup stability in the metastatic compartment. We assembled a cohort of 12-paired primary-metastatic tumors collected in the MAGIC consortium, and established their molecular subgroup affiliation by performing integrative gene expression and DNA methylation analysis. Frozen tissues were collected and profiled using Affymetrix gene expression arrays and Illumina methylation arrays. Class prediction and hierarchical clustering were performed using existing published datasets. Our molecular analysis, using consensus integrative genomic data, establishes the unequivocal maintenance of molecular subgroup affiliation in metastatic medulloblastoma. We further validated these findings by interrogating a non-overlapping cohort of 19-pairs of primary-metastatic tumors from the Burdenko Neurosurgical Institute using an orthogonal technique of immunohistochemical staining. This investigation represents the largest reported primary-metastatic paired cohort profiled to date and provides a unique opportunity to evaluate subgroup-specific molecular aberrations within the metastatic compartment. Our findings further support the hypothesis that medulloblastoma subgroups arise from distinct cells of origin, which are carried forward from ontogeny to oncology.

Enhanced platelet-derived growth factor (PDGF) signaling in glioma drives its development and progression. In this study, we define a unique role for stroma-derived PDGF signaling in maintaining tumor homeostasis within the glioma microenvironment. Large numbers of PDGF receptor-α (PDGFRα)-expressing stromal cells derived from oligodendrocytes progenitor cells (OPC) were discovered at the invasive front of high-grade gliomas, in which they exhibited a unique perivascular distribution. In PDGFRα-deficient host mice, in which orthotopic Gl261 tumors displayed reduced outgrowth, we found that tumor-associated blood vessels displayed smaller lumens and normalized vascular morphology, with tumors in host animals injected with the vascular imaging agent gadolinium also being enhanced less avidly by MRI. Notably, glioma-associated OPC promoted endothelial sprouting and tubule formation, in part by abrogating the inhibitory effect that perivascular astrocytes exert on vascular endothelial conjunctions. Stromal-derived PDGF-CC was crucial for the recruitment and activation of OPC, insofar as mice genetically deficient in PDGF-CC phenocopied the glioma/vascular defects observed in PDGFRα-deficient mice. Clinically, we showed that higher levels of PDGF-CC in glioma specimens were associated with more rapid disease recurrence and poorer overall survival. Our findings define a PDGFRα/PDGF-CC signaling axis within the glioma stromal microenvironment that contributes to vascular remodeling and aberrant tumor angiogenesis in the brain.

Background:The pattern of cranial venous drainage in syndromic craniosynostosis is unpredictable and not adequately understood. Collateral channels substitute for stenotic venous sinuses and pose potential risk for surgical intervention. The purpose of this study was to analyze the patterns of venous drainage in patients with syndromic craniosynostosis and their influence on operative planning and morbidity.Methods:A retrospective study of patients with syndromic craniosynostosis from 2000 to 2013 was performed. Demographic data were collected including phenotype and associated pathologies. Pre- and/or postoperative venous imaging was reviewed for venous sinus stenosis, collateral emissaries, and persistent fetal sinuses. Categorization of anomalous venous drainage was performed, and the relationship with surgical morbidity was assessed.Results:Forty-one patients were identified. Anomalies were present in 31 patients (76%) consisting of dural sinus stenosis in 28 (68%), dilated emissaries in 26 (63%), and fetal sinuses in 7 (17%). Pfeiffer syndrome was most commonly associated with anomalous drainage (100%). Venous anomalies were associated with elevated intracranial pressure (ICP), shunted hydrocephalus, Chiari malformations, and sleep apnea. In 5 cases, the surgical plan was adjusted based on anomalous anatomy. No mortalities occurred. Intraoperative complication rate was 7.3%, all with anomalous drainage. Median estimated blood loss was 1,100 cc for patients with anomalies versus 400 cc without anomalies (P = 0.181).Conclusion:Cranial venous anomalies are commonly detected in patients with syndromic craniosynostosis and may affect surgical morbidity and outcome with a higher estimated blood loss, alteration of procedure, and postoperative morbidity. Detailed preoperative imaging of the venous drainage is therefore recommended in cases of syndromic synostosis.

The cerebrospinal fluid-related morbidity associated with autologous duraplasty for CM-I in a uniformly treated population is negligible. These results challenge the current rationale for a less aggressive surgical approach to CM-I.

Object The authors' aim in this study was to determine if standardizing the evaluation of intraoperative findings during endoscopic third ventriculostomy (ETV) could predict patients with hydrocephalus in whom endoscopic treatment will fail and require ventriculoperitoneal shunt treatment. The creation of a uniform scale with predictive outcomes may reduce returns to the operating room for shunt treatment and reliance on postoperative externalized ventricular monitoring and MR imaging. Methods The authors evaluated the preoperative history, intraoperative findings, and postoperative monitoring and imaging findings in 109 consecutive patients undergoing 112 consecutive attempted ETVs for obstructive hydrocephalus. A 5-grade scale was developed to assess preoperative risk factors and intraoperative evaluation to unify criteria that have been suspected to influence outcome independently. A grade of 0 was assigned to patients with no negative predictors, whereas increasing scores were assigned to patients who had multiple preoperative and intraoperative risks identified. Patients' grades were compared with outcome of the procedure, utility of externalized ventricular monitoring, and results of postoperative MR imaging. Results Of 112 ETVs, 77 were successful and 35 were unsuccessful. Fifty-nine patients received a grade of 0, 27 received a grade of 1, 11 received a grade of 2, and 15 received a grade of ≥ 3. In all 15 patients receiving a grade ≥ 3 attempted ETV procedures failed, and the patients required a ventriculoperitoneal shunt. Postoperative monitoring with externalized ventricular drains and MR images demonstrating radiographic evidence of flow was independently less reliable than intraoperative grading in predicting success. Patients with a grade of 0 almost uniformly had successful surgery, independent of MR imaging findings. Patients with a grade of 1 or 2 who had successful surgery almost always lacked negative intraoperative predictive findings. Conclusions Despite reliance in recent years on post-ETV MR images and externalized ventricular monitoring, these modalities, although often useful adjuncts, appear less reliable as predictive tests than a simple assessment at the time of endoscopic fenestration. By using a uniform grading scale, the authors have introduced a novel means through which intraoperative and postoperative decision making can be aided, with the goal of reducing unnecessary procedures and tests and preventing unnecessary returns to the operating room.

Tumors are capable of coopting hematopoietic cells to create a suitable microenvironment to support malignant growth. Here, we have demonstrated that upregulation of kinase insert domain receptor (KDR), also known as VEGFR2, in a myeloid cell sublineage is necessary for malignant progression of gliomas in transgenic murine models and is associated with high-grade tumors in patients. KDR expression increased in myeloid cells as myeloid-derived suppressor cells (MDSCs) accumulated, which was associated with the transformation and progression of low-grade fibrillary astrocytoma to high-grade anaplastic gliomas. KDR deficiency in murine BM-derived cells (BMDCs) suppressed the differentiation of myeloid lineages and reduced granulocytic/monocytic populations. The depletion of myeloid-derived KDR compromised its proangiogenic function, which inhibited the angiogenic switch necessary for malignant progression of low-grade to high-grade tumors. We also identified inhibitor of DNA binding protein 2 (ID2) as a key upstream regulator of KDR activation during myeloid differentiation. Deficiency of ID2 in BMDCs led to downregulation of KDR, suppression of proangiogenic myeloid cells, and prevention of low-grade to high-grade transition. Tumor-secreted TGF-β and granulocyte-macrophage CSF (GM-CSF) enhanced the KDR/ID2 signaling axis in BMDCs. Our results suggest that modulation of KDR/ID2 signaling may restrict tumor-associated myeloid cells and could potentially be a therapeutic strategy for preventing transformation of premalignant gliomas.