For instance, miR-21 that can be detected in exosomes derived from various cancers such as hepatocellular carcinoma [4] and colon adenocarcinoma [5], was revealed to promote hepatocellular carcinoma growth through Tet methylcytosine dioxygenases/PTEN pseudogene 1/Phosphatase and tensin homolog (TETs/PTENp1/PTEN) pathway [4], and facilitate colon adenocarcinoma proliferation and invasion by targeting programmed cell death 4 (PDCD4) [5]. The gene discussed is PDCD4; the disease is cancer.