NHERF-1: modulator of glioblastoma cell migration and invasion

The invasive nature of malignant gliomas is a clinical problem rendering tumors incurable by conventional treatment modalities such as surgery, ionizing radiation, and temozolomide. Na(+)/H(+) exchanger regulatory factor 1 (NHERF-1) is a multifunctional adaptor protein, recruiting cytoplasmic signaling proteins and membrane receptors/transporters into functional complexes. This study revealed that NHERF-1 expression is increased in highly invasive cells that reside in the rim of glioblastoma multiforme (GBM) tumors and that NHERF-1 sustains glioma migration and invasion. Gene expression profiles were evaluated from laser capture-microdissected human GBM cells isolated from patient tumor cores and corresponding invaded white matter regions. The role of NHERF-1 in the migration and dispersion of GBM cell lines was examined by reducing its expression with small-interfering RNA followed by radial migration, three-dimensional collagen dispersion, immunofluorescence, and survival assays. The in situ expression of NHERF-1 protein was restricted to glioma cells and the vascular endothelium, with minimal to no detection in adjacent normal brain tissue. Depletion of NHERF-1 arrested migration and dispersion of glioma cell lines and caused an increase in cell-cell cohesiveness. Glioblastoma multiforme cells with depleted NHERF-1 evidenced a marked decrease in stress fibers, a larger cell size, and a more rounded shape with fewer cellular processes. When NHERF-1 expression was reduced, glioma cells became sensitized to temozolomide treatment resulting in increased apoptosis. Taken together, these results provide the first evidence for NHERF-1 as a participant in the highly invasive phenotype of malignant gliomas and implicate NHERF-1 as a possible therapeutic target for treatment of GBM.