A distinct phenotypic change in gliomas at the time of magnetic resonance imaging detection.

OBJECT: Although gliomas remain refractory to treatment, it is not clear whether this characteristic is fixed at the time of its origin or develops later. The authors have been using a model of neurocarcinogenesis to determine whether a time exists during a glioma's evolution during which it is detectable but still curable, thus providing a justification for exploring the clinical merits of an early detection and treatment strategy. The authors recently reported the presence of 2 distinct cellular subsets, 1 expressing nestin and the other both glial fibrillary acidic protein (GFAP) and osteopontin (OPN), within all examined gliomas that developed after in utero exposure to ethylnitrosourea.
METHODS: In this study, the authors used magnetic resonance (MR) imaging to assess when these 2 subpopulations appeared during glioma evolution.
RESULTS: Using T2-weighted and diffusion-weighted MR imaging, the authors observed that gliomas grew exponentially once detected at rates that were location-dependent. Despite large differences in growth rates, however, they determined by correlating histochemistry with imaging in a second series of animals, that all lesions initially detected on T2-weighted images contained both subsets of cells. In contrast, lesions containing only nestin-positive cells, which appeared on average 40 days before detection on MR images, were not detected.
CONCLUSIONS: The sequential appearance of first the nestin-positive cells followed several weeks later by those expressing GFAP/OPN suggests that all gliomas arise through common early steps in this model. Furthermore, the authors hypothesize that the expression of OPN, a molecule associated with cancer aggressiveness, at the time of T2-weighted detection signals a time during glioma development when the lesion becomes refractory to treatment.