Ahmed Mohyeldin

Oxygen in Stem Cell Biology: A Critical Component of the Stem Cell Niche

The defining hallmark of stem cells is their ability to self-renew and maintain multipotency. This capacity depends on the balance of complex signals in their microenvironment. Low oxygen tensions (hypoxia) maintain undifferentiated states of embryonic, hematopoietic, mesenchymal, and neural stem cell phenotypes and also influence proliferation and cell-fate commitment. Recent evidence has identified a broader spectrum of stem cells influenced by hypoxia that includes cancer stem cells and induced pluripotent stem cells. These findings have important implications on our understanding of development, disease, and tissue-engineering practices and furthermore elucidate an added dimension of stem cell control within the niche.

Mesenchymal stem cells: new approaches for the treatment of neurological diseases.

Cellular therapies represent a new frontier in the treatment of neurological disease. Mesenchymal stem cells (MSCs), which can be harvested from bone marrow, adipose tissue, and umbilical cord blood, among many other sources, possess several qualities which may be used to treat diseases of the central nervous system. MSCs migrate to sites of malignancy, a property which may be used for the treatment of brain cancer. MSCs possess immunosuppressive properties, which may be used for the treatment of neurological disorders with an inflammatory etiology. Finally, MSCs restore injured neural tissue, a property which may be used for the treatment of neural injury. Approximately 23 clinical trials have been completed to date, with many more ongoing, and all have been listed in this review. The long-term safety of MSC-based therapies is not well established, and continues to be one major limitation to clinical translation. More broadly, only a small minority of clinical trials have employed rigorous designs that include prospective randomization, patients from multiple centers, clinically-relevant and reproducible endpoints, and adequate long-term follow-up. These limitations must be addressed before MSCs can enter widespread clinical use. Nevertheless, MSCs represent a promising new approach to treating diseases of the central nervous system that are traditionally associated with morbid outcomes. With additional pre-clinical and clinical studies that focus on their potential benefits as well as dangers, MSCs may one day find translation to clinical use in the setting of neurological disease.

Generation of chordoma cell line JHC7 and the identification of Brachyury as a novel molecular target: Laboratory investigation

OBJECT Chordoma is a malignant bone neoplasm hypothesized to arise from notochordal remnants along the length of the neuraxis. Recent genomic investigation of chordomas has identified T (Brachyury) gene duplication as a major susceptibility mutation in familial chordomas. Brachyury plays a vital role during embryonic development of the notochord and has recently been shown to regulate epithelial-to-mesenchymal transition in epithelial-derived cancers. However, current understanding of the role of this transcription factor in chordoma is limited due to the lack of availability of a fully characterized chordoma cell line expressing Brachyury. Thus, the objective of this study was to establish the first fully characterized primary chordoma cell line expressing gain of the T gene locus that readily recapitulates the original parental tumor phenotype in vitro and in vivo. METHODS Using an intraoperatively obtained tumor sample from a 61-year-old woman with primary sacral chordoma, a chordoma cell line (JHC7, or Johns Hopkins Chordoma Line 7) was established. Molecular characterization of the primary tumor and cell line was conducted using standard immunostaining and Western blotting. Chromosomal aberrations and genomic amplification of the T gene in this cell line were determined. Using this cell line, a xenograft model was established and the histopathological analysis of the tumor was performed. Silencing of Brachyury and changes in gene expression were assessed. RESULTS The authors report, for the first time, the successful establishment of a chordoma cell line (JHC7) from a patient with pathologically confirmed sacral chordoma. This cell line readily forms tumors in immunodeficient mice that recapitulate the parental tumor phenotype with conserved histological features consistent with the parental tumor. Furthermore, it is demonstrated for the first time that silencing of Brachyury using short hairpin RNA renders the morphology of chordoma cells to a more differentiated-like state and leads to complete growth arrest and senescence with an inability to be passaged serially in vitro. CONCLUSIONS This report represents the first xenograft model of a sacral chordoma line described in the literature and the first cell line established with stable Brachyury expression. The authors propose that Brachyury is an attractive therapeutic target in chordoma and that JHC7 will serve as a clinically relevant model for the study of this disease.

Role of cancer stem cells in spine tumors: Review of current literature

The management of spinal column tumors continues to be a challenge for clinicians. The mechanisms of tumor recurrence after surgical intervention as well as resistance to radiation and chemotherapy continue to be elucidated. Furthermore, the pathophysiology of metastatic spread remains an area of active investigation. There is a growing body of evidence pointing to the existence of a subset of tumor cells with high tumorigenic potential in many spine cancers that exhibit characteristics similar to those of stem cells. The ability to self-renew and differentiate into multiple lineages is the hallmark of stem cells, and tumor cells that exhibit these characteristics have been described as cancer stem cells (CSCs). The mechanisms that allow nonmalignant stem cells to promote normal developmental programming by way of enhanced proliferation, promotion of angiogenesis, and increased motility may be used by CSCs to fuel carcinogenesis. The purpose of this review is to discuss what is known about the role of CSCs in tumors of the osseous spine. First, this article reviews the fundamental concepts critical to understanding the role of CSCs with respect to chemoresistance, radioresistance, and metastatic disease. This discussion is followed by a review of what is known about the role of CSCs in the most common primary tumors of the osseous spine.

217 YAP Is Ready to Rac and Rho: Elucidation of a Novel YAP-Driven Network That Potentiates Brain Cancer Cell Dispersal and Confers Poor Survival in Patients.

INTRODUCTION Molecular pathways linking cell polarization and migration to extracellular cues regulate many pathological processes, including progression of aggressive and infiltrative cancers. Glioblastoma (GBM), the most common and lethal form of primary brain cancer, is characterized by its pronounced ability to disseminate into the intricate microenvironment of the human brain, confounding surgical excision and radiotherapy, leading to a median patient survival of 14 months. Progression results from defects in molecular pathways linking cell migration and invasion into surrounding tissue. However, the molecular engines are not known. METHODS Using patient-derived GBM tissues and cells, we profiled the expression of network moieties via Western blotting, quantitative real-time polymerase chain reaction and performed live cell time-lapse microscopy, bioinformatics analyses, in vivo intracranial GBM experiments using genetic and pharmacological inhibitors to delineate a prodispersal mechanism for management and treatment of GBMs. RESULTS Yes-associated protein (YAP), a transcriptional coactivator, is overexpressed and hyperactive in 78% of GBMs and 50% of metastatic tumors to the brain (P < .05). Our studies demonstrate that YAP activates a Rho-GTPase switch to potentiate migratory speed by interacting with canonical pathways through direct transcriptional control. In addition, YAP mediates a proinvasive genetic network by direct posttranslational regulation. By coupling the regulation of migration and invasion, YAP drives tumor cell dispersal in vitro and in vivo (P < .05). Hyperactivation of this YAP-driven network in GBM confers poor patient outcome in clinical biopsies and The Cancer Genome Atlas (P < .05), suggesting a new signature in clinical prognosis of this aggressive and infiltrative cancer. Targeting this network using a proprietary pharmacological inhibitor attenuates tumor dispersal and growth (P < .05). CONCLUSION YAP can critically control cellular locomotion through direct interaction with canonical molecular pathways controlling invasion and migration. Understanding the molecular underpinnings of this network is vital to the development of imperative prognostic and treatment approaches for cancer such as the new proprietary pharmacological inhibitor presented in this study.INTRODUCTION: Molecular pathways linking cell polarization and migration to extracellular cues regulate many pathological processes, including progression of aggressive and infiltrative cancers. Glioblastoma (GBM), the most common and lethal form of primary brain cancer, is characterized by its pronounced ability to disseminate into the intricate microenvironment of the human brain, confounding surgical excision and radiotherapy, leading to a median patient survival of 14 months. Progression results from defects in molecular pathways linking cell migration and invasion into surrounding tissue. However, the molecular engines are not known.