mTOR Signaling and Cancer Progression

All eukaryotic cells must regulate their growth depending on the cues from their environment.

Certain genes, such as the mechanistic target of rapamycin, or mTOR, respond to various factors to regulate fundamental cellular processes, including the availability of nutrients, growth factors, and cellular stress.

mTOR is a large protein kinase of mammalian cells that exists in two functionally distinct multiprotein complexes - mTOR complex 1 or mTORC1 and mTOR complex 2 or mTORC2.

Amongst an immensely complex mTOR signaling network, the PI(3)K/AKT/mTOR pathway plays a crucial role in cell growth control.

Upon stimulation by binding insulin or insulin-like growth factors, the receptor tyrosine kinases on the cell surface activate the downstream signaling molecule- phosphatidylinositol 3-kinase or PI(3)K.

Active PI(3)K generates phosphatidylinositol 3,4,5-trisphosphate or PIP3, which enables 3-phosphoinositide-dependent kinase 1 or PDK1 to phosphorylate and activate another protein called AKT.

Active AKT protein, in turn, phosphorylates and inhibits the activity of the growth-suppressing, tuberin-hamartin complex or TSC complex.

TSC complex has a GTPase-activating  activity. In its acti