STAT3 and melanoma: The anti-melanoma effect of natural drugs is also mediated through a number of other mechanisms, including stimulation of activity of caspase, angiogenesis inhibition, and tumor-promoting proteins inhibition including Pl3-K, B-cell lymphoma 2 (Bcl-2), signal transducer and activator of transcription 3 (STAT3) and Matrix metalloproteinases (MMPs) [39].