CDK4 and breast carcinoma: Aromatase is the enzyme that catalyzes the conversion of androgens to estrogens, whereestrogens are known important in the growth of breast cancer in both pre- and postmenopausal women [19].Research has usually shown that activated mTOR signaling leads to an increase in tumor progression [20].CDK4/6 is serine/threonine kinases that contain a 300-amino acid catalytic domain generally inactive.