Human astrocytoma cells were studied using whole cell patch-clamp recording
. An inward, amiloride-sensitive Na+ current was identified in four continu
ous cell lines originally derived from human glioblastoma cells (CH235, CRT
, SKMG-1, and U251-MG) and in three primary cultures of cells obtained from
glioblastoma multiforme tumors (up to 4 passages). In addition, cells fres
hly isolated from a resected medulloblastoma tumor displayed this same char
acteristic inward current. In contrast, amiloride-sensitive currents were n
ot observed in normal human astrocytes, low-grade astrocytomas, or juvenile
pilocytic astrocytomas. The only amiloride-sensitive Na+ channels thus far
molecularly identified in brain are the brain Na+ channels (BNaCs). RT-PCR
analyses demonstrated the presence of mRNA for either BNaC1 or BNaC2 in th
ese tumors and in normal astrocytes. These results indicate that the functi
onal expression of amiloride-sensitive Na+ currents is a characteristic fea
ture of malignant brain tumor cells and that this pathway may be a potentia
lly useful target for therapeutic intervention.