STAT3 and cancer: The up-regulation of miRNA-21 results in the promotion of cancer growth, proliferation, invasion, angiogenesis, and metastasis via targeting of many genes involved in apoptosis and tumor suppression, including programmed cell death protein 4 (PDCD4), tropomyosin 1 (TPM1), RAS p21 protein activator (RASA1), phosphatase tensin and homolog (PTEN), MASPIN, P53, B cell lymphoma 2 (Bcl2), signal transducer and activator of transcription 3 (STAT3), and leucine zipper transcription factor-like 1 (LZTFL1).