PDCD4 and central nervous system cancer: miR-21 expression in high-grade (III-IV) gliomas was higher than that observed in low-grade (I-II) gliomas (P < 0.001).9 In the T98G glioma cell line, the level of expression of the PDCD4 gene showed an inverse relationship with the expression of miR-21, and its reduction led to the inhibition of apoptosis.