Overexpression of protein tyrosine kinases (PTKs), such as EGFR, HER2, and IGFR activate different cell signaling pathways that include PI3/AKT, NIFκB, STAT3, and ERK1/2, which also lead to aberrant expression apoptosis related proteins in cancer cells that are the major causes of cancer cells resistance to chemotherapies. Here, STAT3 is linked to cancer.