Loss and gain of function studies in different types of cancer types have established a role for miR-21 in cell proliferation, inhibition of apoptosis, migration, invasion and distant metastasis [20], [21], [35], [36], [37], and a number of cancer-relevant miR-21 target genes in addition to Pdcd4 and PTEN have been identified [38], [39], [40]. Here, PDCD4 is linked to cancer.