STAT3 and cancer: The mechanisms may include cancer stem cells [8–11], hypoxia [e.g., Hypoxia-inducible factor 1α; (HIF-1α)] [12], human papillomavirus (HPV) [13], and signal transduction pathways [e.g., the signal transducer and activator of transcription 3 (STAT3), phosphoinositide-3 kinase (PI3K)/Akt].