To test the functional effect of HRK expression on GBM cells, we first assessed cell viability and observed that HRK overexpression triggered cell death significantly in LN18, U87MG, and U373 but not in A172 cells as shown by cell viability assays and fluorescent images of cells displaying apoptotic morphologies (Fig. 1d, g). The gene discussed is HRK; the disease is glioblastoma.