Targeted therapy is a new cancer treatment approach, involving drugs that particularly target specifc proteins in cancer
cells, such as receptor tyrosine kinases (RTKs) which are involved in promoting growth and proliferation, Therefore inhibiting these proteins could impede cancer progression. An understanding of RTKs and the relevant signaling cascades, has
enabled the development of many targeted drug therapies employing RTK inhibitors (RTKIs) some of which have entered
clinical application. Here we discuss RTK structures, activation mechanisms and functions. Moreover, we cover the potential
efects of combination drug therapy (including chemotherapy or immunotherapy agents with one RTKI or multiple RTKIs)
especially for drug resistant cancers.