KRAS and glioblastoma: Moreover, for the pre- and post-concurrent chemoradiotherapy (CCRT) treatment of GBM patients, the primary GBM patient tissue (pre-CCRT) showed a low expression of K-RAS and CD44, while a high expression of K-RAS and CD44 were observed in the recurrent GBM patient tissue (after-CCRT) using IHC and ICC staining analysis (Figure 5E).