Downregulation of LKB1 mRNA and protein expression in glioma tissues. LKB1 expression was markedly decreased at (A) mRNA (tumor vs. normal, 1.96±0.59 vs. 3.66±0.92; P<0.001), and (B) protein (tumor vs. normal, 1.89±0.54 vs. 3.71±0.87; P<0.001) levels in 30 freshly prepared glioma tissues, compared with that in non-neoplastic brain tissues. (C) Spearman's rank correlation analysis revealed that the expression levels of LKB1 mRNA in glioma tissues were closely correlated with those of LKB1 protein in gliomas (r=0.32; P=0.02). (D) Relatively lower expression levels of LKB1 mRNA and protein were observed in freshly prepared high-grade glioma tissue samples (WHO grades III–IV) compared with those in low-grade glioma samples (WHO grades I–II). *P<0.05. LKB1, liver kinase B1; WHO, World Health Organization; mRNA, messenger RNA.