GSK2126458 (Synonyms: GSK212; GSK-2126458; GSK 2126458; GSK-212; GSK 212)

GSK2126458 is an inhibitor of PI3K/mTOR with Ki value of 19 pM for PI3K [1].
PI3K (phosphoinositide 3-kinase) plays an important role in regulating cell growth and transformation, and mTOR (mammalian target of rapamycin) which works as a class IV PI3K protein kinase, is also a crucial regulator of cell growth [2]. It has been shown that up-regulation of PI3K/mTOR (phosphatidylinositol-3' kinase/mammalian target of rapamycin) signaling is widespread in carcinoma which may be worked as a biomarker used in clinic [3].
GSK2126458 is a highly potent inhibitor of PI3K/mTOR. When subjected to colorectal cancer cell lines, GSK2126458 could potentiate the cells antiproliferative activity via combining with DDR1-IN-1[4]. In BT474 breast cancer lines, treated with GSK2126458 could be the arrest of G1 cell cycle and thus inhibit cell proliferation [5]. GSK2126458 also could improve the sensitivity of NPC cells to radiation and suppress tumor progression [1].  
In a 5-8F xenograft model with NPC, treated the mouse with GSK2126458 combining of IR significantly inhibited the tumor growth [1]. In mice injected with cancer cells from melanoma patient resisted to the combination of divergent and trametinib, GSK2126458 combined with dabrafenib, trametinib treatment resulted in sustained inhibition of tumor growth[3].
GSK2126458 may play a significant role in regulating autophagy [6].
References:
1.Liu, T., et al., Dual PI3K/mTOR inhibitors, GSK2126458 and PKI-587, suppress tumor progression and increase radiosensitivity in nasopharyngeal carcinoma. Mol Cancer Ther, 2014. 12.
2.Simpson, D.R., L.K. Mell, and E.E. Cohen, Targeting the PI3K/AKT/mTOR pathway in squamous cell carcinoma of the head and neck: Oral Oncol. 2014 Dec 17. pii: S1368-8375(14)00351-0. doi: 10.1016/j.oraloncology.2014.11.012.
3.Villanueva, J., et al., Concurrent MEK2 mutation and BRAF amplification confer resistance to BRAF and MEK inhibitors in melanoma. Cell Rep, 2013. 4(6): p. 1090-9.
4.Kim, H.G., et al., Discovery of a potent and selective DDR1 receptor tyrosine kinase inhibitor. ACS Chem Biol, 2013. 8(10): p. 2145-50.
5.Knight, S.D., et al., Discovery of GSK2126458, a Highly Potent Inhibitor of PI3K and the Mammalian Target of Rapamycin. ACS Med Chem Lett, 2010. 1(1): p. 39-43.
6.Zhang, Y., et al., Screening of kinase inhibitors targeting BRAF for regulating autophagy based on kinase pathways. Mol Med Rep, 2014. 9(1): p. 83-90.