ABSTRACT
OPINION STATEMENT: Gliomas that affect the optic pathways are for the most part low-grade neoplasms that often, but not always, have good prognoses. Optimal treatment and management of optic pathway gliomas remains unclear and the decision hinges upon several factors including patient age, tumor location, and visual symptoms. We favor a treatment approach that is dependent on the location of tumor within anterior, chiasmal or posterior/hypothalamic visual pathways. In children who are minimally or not symptomatic, we recommend observation rather than early treatment intervention. Most of these patients will have neurofibromatosis type 1 (NF1) based on the natural history and their pilocytic astrocytoma histology. Serial magnetic resonance imaging studies and formal neuro-ophthalmology testing should enable close observation of these patients, with intervention being reserved for when tumor progression results in significant visual loss or proptosis. Chemotherapy is an accepted first line treatment, and a number of effective medications are available, although no agent has proven clearly superior. If progression is accompanied by the complete loss of vision, surgery can be utilized to help alleviate structural issues (ie, proptosis). Minimally symptomatic chiasmal or hypothalamic tumors that arise in the setting of NF1 can also be observed initially because of their favorable prognosis. Children with NF1 and chiasmal or posterior visual tumors who progress either on imaging or clinical grounds (ie, development of significant visual deficits) should be treated first with chemotherapy rather than radiation therapy to minimize the effects on the developing central nervous system. Individuals without NF1 presenting with a chiasmal or hypothalamic mass are candidates for biopsy to determine the underlying pathology of the lesion. Symptomatic patients with pilocytic astrocytoma should first receive chemotherapy. In contrast, other histologies including malignant optic pathway gliomas should be treated similar to other gliomas that occur in other locations with appropriate doses of radiation and chemotherapy.
ABSTRACT
The relationship between mutated proteins and the cancer stem-cell population is unclear. Glioblastoma tumors frequently express EGFRvIII, an EGF receptor (EGFR) variant that arises via gene rearrangement and amplification. However, expression of EGFRvIII is restricted despite the prevalence of the alteration. Here, we show that EGFRvIII is highly coexpressed with CD133 and that EGFRvIII(+)/CD133(+) defines the population of cancer stem cells (CSC) with the highest degree of self-renewal and tumor-initiating ability. EGFRvIII(+) cells are associated with other stem/progenitor markers, whereas markers of differentiation are found in EGFRvIII(-) cells. EGFRvIII expression is lost in standard cell culture, but its expression is maintained in tumor sphere culture, and cultured cells also retain the EGFRvIII(+)/CD133(+) coexpression, self-renewal, and tumor initiating abilities. Elimination of the EGFRvIII(+)/CD133(+) population using a bispecific antibody reduced tumorigenicity of implanted tumor cells better than any reagent directed against a single epitope. This work demonstrates that a mutated oncogene can have CSC-specific expression and be used to specifically target this population.
