To explore this scenario further, we used siRNAs to specifically knock down Cx43 in astrocytes (rather than in glioma cells, as above), to block glioma-astrocyte and astrocyte-astrocyte gap junctions (Figure 2F and Supplementary Figure S2E), but leave glioma-glioma gap junctions unaltered. This evidence concerns the gene GJA1 and central nervous system cancer.