Knockdown of miR-21 by miR-21-miRNase resulted in specific elevation of the level of the direct mRNA target of miR-21, tumor-suppressor programmed cell death 4 (PDCD4) (Patutina et al., 2017a), and so may also turn down the malignant behavior of tumor cells through induction of apoptosis and inhibition of invasion and metastasis. Here, PDCD4 is linked to neoplasm.