STAT3 and cancer: As a consequence, PKA can phosphorylate several proteins including cAMP response element-binding protein (CREB), Activating transcription factors (ATF), (Signal transducer and activator of transcription-3) STAT-3, globin transcription factor-1 (GATA-1) and Src family kinases all known to trigger pro-tumorigenic pathways that sustain cellular proliferation, escape from apoptosis, migration and invasion, epithelial–mesenchymal transition (EMT) and pre-metastatic niche formation in different types of cancer [3–5].