Subsequently, these same authors have shown, in a human glioma cell line, U-251, that UA, in addition to triggering similar mechanisms of cytotoxicity, apoptosis, and survival, was capable of increasing caspase-3 activity and, at the same time, significantly repressing the expression of microRNA-21 (miR-21), which facilitates the expression of PDCD4 (programmed cell death protein 4), which is a pro-apoptotic protein encoded by the corresponding gene, suggesting that UA induces apoptosis in U251 cells via the TGF-b1/miR-21/PDCD4 pathway activated by UA [129]. Here, PDCD4 is linked to glioma.