Combinations of genetic mutations in the adult neural stem cell compartment determine brain tumour phenotypes

Brain tumor stem cells: the cancer stem cell hypothesis writ large

Brain tumors, which are typically very heterogeneous at the cellular level, appear to have a stem cell foundation. Recently, investigations from multiple groups have found that human as well as experimental mouse brain tumors contain subpopulations of cells that functionally behave as tumor stem cells, driving tumor growth and generating tumor cell progeny that form the tumor bulk, but which then lose tumorigenic ability. In human glioblastomas, these tumor stem cells express neural precursor markers and are capable of differentiating into tumor cells that express more mature neural lineage markers. In addition, modeling brain tumors in mice suggests that neural precursor cells more readily give rise to full blown tumors, narrowing potential cells of origin to those rarer brain cells that have a proliferative potential. Applying stem cell concepts and methodologies is giving fresh insight into brain tumor biology, cell of origin and mechanisms of growth, and is offering new opportunities for development of more effective treatments. The field of brain tumor stem cells remains very young and there is much to be learned before these new insights are translated into new patient treatments.

Balloon cells in human cortical dysplasia and tuberous sclerosis: isolation of a pathological progenitor-like cell

Neural stem cells are present in the human post-natal brain and are important in the development of brain tumours. However, their contribution to non-neoplastic human disease is less clear. We have tested the hypothesis that malformations of cortical development contain abnormal (pathological) stem cells. Such malformations are a major cause of epilepsy. Two of the most common malformations [focal cortical dysplasia (FCD) and cortical tubers] are characterised by the presence of a population of abnormal cells known as balloon cells. The identity of these cells is unknown but one hypothesis is that they are an abnormal stem cell that contributes to the pathogenesis of the malformation. We have characterised in tissue, and isolated in culture, an undifferentiated population of balloon cells from surgical resections of FCD and cortical tubers. We show that beta1-integrin labels a sub-population of balloon cells with a stem cell phenotype and show for the first time that these cells can be isolated in vitro. We have characterised the immunohistochemical, morphological and ultrastructural features of these cells. This is the first isolation of an abnormal cell with features of a progenitor/stem cell from a non-neoplastic disease of the brain.

Cancer as a reprogramming-like disease: implications in tumor development and treatment

Cancer is a clonal malignant disease originated in a single cell and characterized by the accumulation of partially differentiated cells that are phenotypically reminiscent of normal stages of differentiation. Given the fact that human cancer is diagnosed at later stages and cannot be monitored during its natural evolution, the origin of tumors has been a subject of continuing discussion. Animal models provide a means to determine the identity of the cell-of-origin leading to malignancy and to develop new treatments. Recent findings in mice have shown that cancer stem cells could arise through a reprogramming-like mechanism, suggesting that genetic lesions that initiate the cancer process might be dispensable for tumor progression and maintenance. This review addresses the impact of these results toward a better understanding of carcinogenesis and proposes research avenues for tackling these issues in the future.

Cell cycle control of mammalian neural stem cells: putting a speed limit on G1

The potential to increase unlimitedly in number and to generate differentiated cell types is a key feature of somatic stem cells. Within the nervous system, cellular and environmental determinants tightly control the expansion and differentiation of neural stem cells. Importantly, a number of studies have indicated that changes in cell cycle length can influence development and physiopathology of the nervous system, and might have played a role during evolution of the mammalian brain. Specifically, it has been suggested that the length of G1 can directly influence the differentiation of neural precursors. This has prompted the proposal of a model to explain how manipulation of G1 length can be used to expand neural stem cells. If validated in non-neural systems, this model might provide the means to control the proliferation vs. differentiation of somatic stem cells, which will represent a significant advance in the field.

Optic pathway gliomas in neurofibromatosis-1: controversies and recommendations

Optic pathway glioma (OPG), seen in 15% to 20% of individuals with neurofibromatosis type 1 (NF1), account for significant morbidity in young children with NF1. Overwhelmingly a tumor of children younger than 7 years, OPG may present in individuals with NF1 at any age. Although many OPG may remain indolent and never cause signs or symptoms, others lead to vision loss, proptosis, or precocious puberty. Because the natural history and treatment of NF1-associated OPG is different from that of sporadic OPG in individuals without NF1, a task force composed of basic scientists and clinical researchers was assembled in 1997 to propose a set of guidelines for the diagnosis and management of NF1-associated OPG. This new review highlights advances in our understanding of the pathophysiology and clinical behavior of these tumors made over the last 10 years. Controversies in both the diagnosis and management of these tumors are examined. Finally, specific evidence-based recommendations are proposed for clinicians caring for children with NF1.