Yujie Huang

Lysyl oxidase-like 2 (LOXL2) and E47 EMT factor: novel partners in E-cadherin repression and early metastasis colonization

Epithelial–mesenchymal transition (EMT) has been associated with increased aggressiveness and acquisition of migratory properties providing tumor cells with the ability to invade into adjacent tissues. Downregulation of E-cadherin, a hallmark of EMT, is mediated by several transcription factors (EMT-TFs) that act also as EMT inducers, among them, Snail1 and the bHLH transcription factor E47. We previously described lysyl oxidase-like 2 (LOXL2), a member of the lysyl oxidase family, as a Snail1 regulator and EMT inducer. Here we show that LOXL2 is also an E47-interacting partner and functionally collaborates in the repression of E-cadherin promoter. Loss and gain of function analyses combined with in vivo studies in syngeneic breast cancer models demonstrate the participation of LOXL2 and E47 in tumor growth and their requirement for lung metastasis. Furthermore, LOXL2 and E47 contribute to early steps of metastatic colonization by cell and noncell autonomous functions regulating the recruitment of bone marrow progenitor cells to the lungs and by direct transcriptional regulation of fibronectin and cytokines TNFα, ANG-1 and GM-CSF. Moreover, fibronectin and GM-CSF proved to be necessary for LOXL2/E47-mediated modulation of tumor growth and lung metastasis.

Oligodendrocyte Progenitor Cells Promote Neovascularization in Glioma by Disrupting the Blood-Brain Barrier

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.

Molecular diagnostics in paediatric glial tumours

Glial tumours in children have distinct patterns of epigenetic alteration, chromosomal structure, and gene and protein expression that differentiate them from their histological counterparts in adults. Understanding paediatric gliomas at the molecular level provides important prognostic and therapeutic insights, such as which genetic alterations confer a favourable response to adjuvant therapy, or which signalling pathways might be amenable to specific molecularly targeted agents. For clinicians, the ultimate goal is to individualise therapeutic regimens on the basis of the molecular fingerprint of a particular tumour and the prognosis conferred by this profile. In this Review, we examine a series of studies of molecular and genomic analysis of glial tumours in children, and discuss the many clinical insights that these molecular features provide.

Ependymoma in children: molecular considerations and therapeutic insights

A multi-modality approach that encompasses maximal surgical resection in combination with adjuvant therapy is critical for achieving optimal disease control in children with ependymoma. In view of its complex biology and variable response to therapy, ependymoma remains a challenge for clinicians involved in the care of these patients. Meanwhile, translation of molecular findings can characterize unique features of childhood ependymoma and their natural history. Furthermore, understanding the biology of pediatric ependymoma serves as a platform for development of future targeted therapies. In line with these goals, we review the molecular basis of pediatric ependymoma and its prognostic implications, as well as novel therapeutic advances in the management of ependymoma in children.

A proangiogenic signaling axis in myeloid cells promotes malignant progression of glioma

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-&bgr; 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.

Malignant astrocytic tumor progression potentiated by JAK-mediated recruitment of myeloid cells

Purpose: While the tumor microenvironment has been known to play an integral role in tumor progression, the function of nonresident bone marrow–derived cells (BMDC) remains to be determined in neurologic tumors. Here we identified the contribution of BMDC recruitment in mediating malignant transformation from low- to high-grade gliomas. Experimental Design: We analyzed human blood and tumor samples from patients with low- and high-grade gliomas. A spontaneous platelet-derived growth factor (PDGF) murine glioma model (RCAS) was utilized to recapitulate human disease progression. Levels of CD11b+/GR1+ BMDCs were analyzed at discrete stages of tumor progression. Using bone marrow transplantation, we determined the unique influence of BMDCs in the transition from low- to high-grade glioma. The functional role of these BMDCs was then examined using a JAK 1/2 inhibitor (AZD1480). Results: CD11b+ myeloid cells were significantly increased during tumor progression in peripheral blood and tumors of glioma patients. Increases in CD11b+/GR1+ cells were observed in murine peripheral blood, bone marrow, and tumors during low-grade to high-grade transformation. Transient blockade of CD11b+ cell expansion using a JAK 1/2 Inhibitor (AZD1480) impaired mobilization of these cells and was associated with a reduction in tumor volume, maintenance of a low-grade tumor phenotype, and prolongation in survival. Conclusions: We demonstrate that impaired recruitment of CD11b+ myeloid cells with a JAK1/2 inhibitor inhibits glioma progression in vivo and prolongs survival in a murine glioma model. Clin Cancer Res; 23(12); 3109–19. ©2016 AACR.

Abstract B2: Oligodendritic precursor mediates vascular remodeling within glioma microenvironment in PDGF-C dependent manner

The platelet derived growth factor (PDGF) signaling pathway is upregulated in many glioma subtypes, plays a role in gliomagenesis and promotes brain tumor progression. In this study, we demonstrate a role for PDGF signaling in the maintenance of brain tumor microenvironment homeostasis. We detected PDGFRa-expressing stromal cells potentially derived from oligodendritic precursor cells in both human and mouse high-grade gliomas. PDGFRa+ cells are predominately located at the invasive front of gliomas, and have a unique perivascular distribution. We suggest that these stromal cells play an important role in both initiating angiogenesis and supporting tumor progression. In an orthotopic model of glioma in PDGFRa deficient mice, tumor growth was significantly inhibited and gadolinium enhancement was decreased shown by bioluminescence and MRI, respectively. Glioma-associated blood vessels in PDGFRa knockout mice have smaller lumens and relatively normal vascular morphology. Glioma-associated oligodendritic precursor cells promoted endothelial sprouting and tubule formation by abrogating the inhibitory effect of astrocytes. We also demonstrated stromal-derived PDGF-CC as a key factor in the recruitment and activation of PDGFRa+ stromal cells. Utilizing PDGF-CC deficient mice, we recapitulate the glioma phenotype demonstrated in PDGFRa; knockout mice, suggesting their joint contribution to this pathway9s integrity. In conclusion, the PDGF-CC/PDGFRa signaling axis in glioma stroma appears to contribute to the remodeling of the vascular architecture in the brain and influences subsequent angiogenesis. Citation Format: Yujie Huang, David Lyden, Jeffrey Greenfield. Oligodendritic precursor mediates vascular remodeling within glioma microenvironment in PDGF-C dependent manner. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr B2.

Bone Marrow-Derived Cells Support Malignant Transformation of Low-Grade Glioma

Gliomas, the most common primary brain tumors, exist as a continuum between low-grade and high-grade states. Low grade gliomas are generally found in children and young adults. These tumors are characterized by well-differentiated cellularity which is mildly pleomorphic. These tumors lack mitotic figures and neovascularization and do not enhance on MRI. The average survival of patients after diagnosis is 7-10 years; the morbidity associated with these lesions is largely dependent on progression of these lesions to a higher grade state. High-grade gliomas, conversely, which exist on the other end of the glial neoplasm spectrum, are extremely malignant with poorly differentiated cells that are highly pleomorphic and display numerous mitotic figures. These tumors contain significant vascular proliferation, hemorrhage and necrosis. High grade gliomas enhance brightly on contrast MRI and often exhibit widespread invasion throughout the brain. Prognosis is poor for high grade gliomas, with a median survival of 18 months even with aggressive therapies. One of the key events in the transition from the low-grade to high-grade state has been referred to as the angiogenic switch. This is defined as the period during which the tumor undergoes a transition to an environment capable of rapid blood vessel formation supporting subsequent exponential tumor growth. It is theorized that in the low-grade state, tumor growth may be limited, at least in part, by a lack of blood supply limiting the tumor to linear growth. Once the tumor acquires the ability to recruit or form new blood vessels through this angiogenic switch, exponential growth may occur, which results in rapid clinical progression. It has been well-described in the literature that bone marrow-derived cells (BMDC) participate in the progression of cancer. BMDCs in the local tumor microenvironment have been proposed to be capable of breaking down normal structures thereby promoting vasculogenesis and invasiveness. This, in turn, provides an environment capable of sustaining and promoting tumor growth. The role of BMDC in metastatic disease has been well-documented and recent data suggests that BMDC participate in the growth and progression of brain tumors as well. This chapter will explore the role of BMDC in the transition from low-grade to high-grade gliomas particularly with respect to the angiogenic