Jennifer Johnson

Tet3 Reads 5-Carboxylcytosine through Its CXXC Domain and Is a Potential Guardian against Neurodegeneration

We report that the mammalian 5-methylcytosine (5mC) oxidase Tet3 exists as three major isoforms and characterized the full-length isoform containing an N-terminal CXXC domain (Tet3FL). This CXXC domain binds to unmethylated CpGs, but, unexpectedly, its highest affinity is toward 5-carboxylcytosine (5caC). We determined the crystal structure of the CXXC domain-5caC-DNA complex, revealing the structural basis of the binding specificity of this domain as a reader of CcaCG sequences. Mapping of Tet3FL in neuronal cells shows that Tet3FL is localized precisely at the transcription start sites (TSSs) of genes involved in lysosome function, mRNA processing, and key genes of the base excision repair pathway. Therefore, Tet3FL may function as a regulator of 5caC removal by base excision repair. Active removal of accumulating 5mC from the TSSs of genes coding for lysosomal proteins by Tet3FL in postmitotic neurons of the brain may be important for preventing neurodegenerative diseases.

Metabotropic Glutamate Receptor-1 as a Novel Target for the Antiangiogenic Treatment of Breast Cancer

Metabotropic glutamate receptors (mGluRs) are normally expressed in the central nervous system, where they mediate neuronal excitability and neurotransmitter release. Certain cancers, including melanoma and gliomas, express various mGluR subtypes that have been implicated as playing a role in disease progression. Recently, we detected metabotropic glutamate receptor-1 (gene: GRM1; protein: mGluR1) in breast cancer and found that it plays a role in the regulation of cell proliferation and tumor growth. In addition to cancer cells, brain endothelial cells express mGluR1. In light of these studies, and because angiogenesis is both a prognostic indicator in cancer correlating with a poorer prognosis and a potential therapeutic target, we explored a potential role for mGluR1 in mediating endothelial cell (EC) proliferation and tumor-induced angiogenesis. GRM1 and mGluR1 were detected in various types of human ECs and, using mGluR1-specific inhibitors or shRNA silencing, we demonstrated that EC growth and Matrigel tube formation are dependent on mGluR1 signaling. In addition, loss of mGluR1 activity leads to reduced angiogenesis in a murine Matrigel sponge implant model as well as a murine tumor model. These results suggest a role for mGluR1 in breast cancer as a pro-angiogenic factor as well as a mediator of tumor progression. They also suggest mGluR1 as a potential new molecular target for the anti-angiogenic therapy of breast cancer.

Overexpression of HGF Promotes HBV- Induced Hepatocellular Carcinoma Progression and Is an Effective Indicator for Met-Targeting Therapy

Hepatitis B virus (HBV) is a well-known cause of hepatocellular carcinoma (HCC), but the regulators effectively driving virus production and HCC progression remain unclear. By using genetically engineered mouse models, we show that overexpression of hepatocyte growth factor (HGF) accelerated HCC progression, supporting the genomic analysis that an up-regulated HGF signature is associated with poor prognosis in HBV-positive HCC patients. We show that for both liver regeneration and spontaneous HCC development there is an inclusive requirement for MET expression, and when HGF induces autocrine activation the tumor displays sensitivity to a small-molecule Met inhibitor. Our results demonstrate that HGF is a driver of HBV-induced HCC progression and may serve as an effective biomarker for Met-targeted therapy. MET inhibitors are entering clinical trials against cancer, and our data provide a molecular basis for targeting the Met pathway in hepatitis B–induced HCC.

Abstract 1867: Near infrared fluorescent imaging of brain tumor with IR780 dye incorporated phospholipid nanoparticles

Background: Near-IR fluorescence (NIRF) imaging is becoming a promising approach in preclinical tumor detection and clinical image-guided oncological surgery. While heptamethine cyanine dye IR780 has excellent tumor targeting and imaging potential, its hydrophobic properties limit its clinical use. In this study, we developed nanoparticle formulations to facilitate the use of IR780 for fluorescent imaging of malignant brain tumor. Methods: Self-assembled IR780-liposomes and IR780-phospholipid micelles were prepared and their NIRF properties were characterized. The intracellular accumulation of IR780-nanoparticles in glioma cells were determined using confocal microscopy. The in vivo brain tumor targeting and NIRF imaging capacity of IR780-nanoparticles were evaluated using U87MG glioma ectopic and orthotopic xenograft models and a spontaneous glioma mouse model driven by RAS/RTK activation. Results: The loading of IR780 into liposomes or phospholipid micelles was efficient. The particle diameter of IR780-liposomes and IR780-phospholipid micelles were 95 nm and 26 nm, respectively. While stock solutions of each preparation were maintained at ready-to-use condition, the IR780-phospholipid micelles were more stable. In tissue culture cells, IR780-nanoparticles prepared by either method accumulated in mitochondria, however, in animals the IR780-phospholipid micelles showed enhanced intra-tumoral accumulation in U87MG ectopic tumors. Moreover, IR780-phospholipid micelles also showed preferred intracranial tumor accumulation and potent NIRF signal intensity in glioma orthotopic models at a real-time, non-invasive manner. Conclusion: The IR780-phospholipid micelles demonstrated tumor-specific NIRF imaging capacity in glioma preclinical mouse models, providing great potential for clinical imaging and image-guided surgery of brain tumors. Citation Format: Shihong Li, Jennifer Johnson, Anderson Peck, Qian Xie. Near infrared fluorescent imaging of brain tumor with IR780 dye incorporated phospholipid nanoparticles [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1867. doi:10.1158/1538-7445.AM2017-1867

Abstract 2896: Genomic determinants and signature of MET-targeted therapy in glioblastoma.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Glioblastoma (GBM) is one of the most devastating cancers, because the intrinsic capability of single tumor cells to invade normal brain impedes surgical eradication, predictably resulting in early local recurrence and death. The goal of this study is to develop therapeutic strategies for treating GBM patients by identifying and targeting the molecular mechanisms of GBM invasiveness through inhibiting MET signaling pathway. Overexpression of hepatocyte growth factor (HGF) and its receptor MET are associated with poor prognosis of GBM. Genomic analysis of primary GBM tumors indicates that MET is overexpressed in tumors of the mesenchymal phenotype, which is more invasive and results in short patient survival. More recently, MET activation was found to contribute to recurrence in GBM patients after bevacizumab treatment, further highlighting the utility of blocking the MET pathway in this disease. With MET inhibitors’ entering clinical trials, there is increased need to find the molecular determinants of MET sensitivity. Because GBM is a heterogeneous disease in which drug response in the individual patient can be regulated by different mechanisms, approaches for understanding and predicting treatment outcomes based on the molecular features of individual tumor will be of a high value. Based on our previous finding that HGF-autocrine activation predicts sensitivity to MET inhibition, we have developed a two-step methodology using microarray technology and bioinformatics analysis to identify and test genomic determinants in order to effectively deploy MET-targeted therapy in GBM patients. By analyzing the data sets from The Cancer Genome Atlas Network (TCGA) and those from GBM xenograft models sensitive and insensitive to MET inhibitors, a 25-gene signature highly associated with HGF-autocrine activation is identified. When performing validation analysis, the signature scored 40 human GBM xenograft models by HGF expression level, providing a good rationale for further testing its predictive value in identifying tumors sensitive to MET inhibitors. We conclude that HGF-autocrine activation can result in oncogene addiction to MET signaling in GBM. Via a unique panel of signature genes we may be able to identify a subset of patients vulnerable to anti-MET drugs. Citation Format: Qian Xie, Jennifer Johnson, Maria Libera Ascierto, Liang Kang, Robert Bradley, Sandeep Mittal, Kyle Furge, Michael Briggs, Kirk Tanner, Michael E. Berens, Francesco M. Marincola, George F. Vande Woude. Genomic determinants and signature of MET-targeted therapy in glioblastoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2896. doi:10.1158/1538-7445.AM2013-2896