STAT3 and cancer: JAK1 is a member of the JAK family, which plays an essential and non-redundant role in the proliferation, differentiation, and metastasis of cancer cells by mediating the expression of interleukin-6 (IL-6)/JAK1/signal transducer and activator of transcription-3 (STAT3) or JAK1/phosphatidylinositol-3-kinase (PI3K) signaling pathway [12, 13].