Probing the PI3K/Akt/mTor pathway using 31P-NMR spectroscopy: routes to glycogen synthase kinase 3

Abstract

Akt is an intracellular signalling pathway that serves as an essential link between cell surface receptors and cellular processes including proliferation, development and survival. The pathway has many downstream targets including glycogen synthase kinase3 which is a major regulatory kinase for cell cycle transit as well as controlling glycogen synthase activity. The Akt pathway is frequently up-regulated in cancer due to overexpression of receptors such as the epidermal growth factor receptor, or mutation of signalling pathway kinases resulting in inappropriate survival and proliferation. Consequently anticancer drugs have been developed that target this pathway. MDA-MB-468 breast and HCT8 colorectal cancer cells were treated with inhibitors including LY294002, MK2206, rapamycin, AZD8055 targeting key kinases in/associated with Akt pathway and the consistency of changes in 31P-NMR-detecatable metabolite content of tumour cells was examined. Treatment with the Akt inhibitor MK2206 reduced phosphocholine levels in MDA-MB-468 cells. Treatment with either the phosphoinositide-3-kinase inhibitor, LY294002 and pan-mTOR inhibitor, AZD8055 but not pan-Akt inhibitor MK2206 increased uridine-5′-diphosphate-hexose cell content which was suppressed by co-treatment with glycogen synthase kinase 3 inhibitor SB216763. This suggests that there is an Akt-independent link between phosphoinositol-3-kinase and glycogen synthase kinase3 and demonstrates the potential of 31P-NMR to probe intracellular signalling pathways.

CENPH Inhibits Rapamycin Sensitivity by Regulating GOLPH3-dependent mTOR Signaling Pathway in Colorectal Cancer

“…PI3K/AKT signaling pathway plays critical roles in orchestrating multiple cellular functions 5 - 8 . Mammalian target of rapamycin (mTOR), as downstream effector of PI3K/AKT pathway, consists of two functionally distinct multi-protein complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2), which were involved in protein synthesis, cell growth, autophagy, metabolism, and survival 5 - 8 .…”

“…PI3K/AKT signaling pathway plays critical roles in orchestrating multiple cellular functions 5 - 8 . Mammalian target of rapamycin (mTOR), as downstream effector of PI3K/AKT pathway, consists of two functionally distinct multi-protein complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2), which were involved in protein synthesis, cell growth, autophagy, metabolism, and survival 5 - 8 . Since the PI3K/AKT/mTOR pathway is upregulated in almost all cancers, anticancer drugs including LY294002, MK2206, everolimus, rapamycin, and AZD8055 have been developed to target crucial kinases associated with this pathway 7 , 8 .…”

“…Mammalian target of rapamycin (mTOR), as downstream effector of PI3K/AKT pathway, consists of two functionally distinct multi-protein complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2), which were involved in protein synthesis, cell growth, autophagy, metabolism, and survival 5 - 8 . Since the PI3K/AKT/mTOR pathway is upregulated in almost all cancers, anticancer drugs including LY294002, MK2206, everolimus, rapamycin, and AZD8055 have been developed to target crucial kinases associated with this pathway 7 , 8 . Among them, rapamycin inhibits mTOR activity by binding to the protein raptor, resulting in decreased cell proliferation and prevention in intestinal tumorigenesis 9 - 10 .…”

Response Detection of Castrate-Resistant Prostate Cancer to Clinically Utilised and Novel Treatments by Monitoring Phospholipid Metabolism

“…PtdCho transfer protein (PC-TP) is involved in preserving steady-state membrane phospholipid content in cells in response to cellular lipid efflux. PC-TP is associated with the steroidal 31 P-NMR spectroscopy that can detect phospholipid metabolites in cells and cell extracts [ 15 , 16 ] and is clinically translatable [ 17 ]. Figure 4 (a) shows a 31 P-NMR spectrum acquired on an aqueous extract from untreated LNCaP cells.…”

Combination treatment of cancer cells with pan-Akt and pan-mTOR inhibitors: effects on cell cycle distribution, p-Akt expression level and radiolabelled-choline incorporation

“…Venkatesh et al [ 28 ] has also demonstrated that treatment with the PI3K inhibitor LY294002 and mTOR inhibitor everolimus decreased phosphocholine levels associated with decreased in choline kinase activity in glioblastoma cell lines. However other studies have shown that phosphocholine content of cancer cells isn’t consistently altered by treatment with PI3K/Akt/mTOR inhibitors [ 29 ].…”