TWIST1 and glioma: The results showed that the mRNA expression levels of Twist1, Twist2, Zeb1, Zeb2 and Slug2 maintained significantly negative correlations with the mRNA expression levels of Presenilin1 in gliomas of all WHO grades (Fig. 2A–D, Additional file 3: Figure S2A), but the relationships were not significant between Presenilin1 and Slug1 (Additional file 3: Figure S2B).