Rapamycin treatment did not affect phosphorylation of AKT or GSK3B but inhibited phosphorylation of p70S6K and S6 ribosomal protein at 2 hours and, more potently, at 8 hours, an activity in line with inhibition of mTORC1. 1E show virtually identical 2 and 8 hour IC50 values for PI 103, PI 540, PI met inhibitor 620, and GDC 0941 against each of the biomarkers of phosphatidylinositide 3 kinase pathway action studied. The four phosphatidylinositide 3 kinase inhibitors were strongest against phosphorylation of AKT on both sites, with IC50 values in the range 10 to 40 nmol/L. Effectiveness decreased by 7 to 12-fold regarding phosphorylation of proteins further downstream of phosphatidylinositide 3 kinase. For instance, PI 540 was 10 fold less effective in inhibiting phosphorylation of GSK3B Ser9 in comparison with phosphorylation of AKT. Consistent with their relatively weaker impact on mTOR kinase activity, the 8-hour IC50 values of the four synthetic inhibitors on phosphorylation Latin extispicium of ribosomal S6 protein on Ser235 was significantly less than that of rapamycin. Given that the phosphatidylinositide 3 kinase inhibitors, especially GDC 0941, exhibited livlier anti-proliferative activity against IGROV 1 ovarian cancer cells compared with U87MG glioblastoma cells, we examined the results of PI 103 and GDC 0941 on the phosphorylation of AKT Ser473 like a sensitive biomarker of phosphatidylinositide 3 kinase inhibition in IGROV 1 cells and compared the with those described above for U87MG cells. The IC50 values for the inhibition of phosphorylation of Ser473 on AKT in IGROV 1 cells following 2 or 8-hour publicity were 18 _ 2 and 17 _ 4 nmol/L, respectively, for PI supplier Oprozomib 103 and 18 _ 1 and 38 _ 13 nmol/L, respectively, for GDC 0941. These values for the ovarian cancer line were remarkably similar to the values in the U87MG glioblastoma cells despite the lower antiproliferative potency of the inhibitors in the glioblastoma line. Finally, we compared the values for inhibition of Ser473 phosphorylation on AKT in three human colon cancer cell lines. Even though the anti-proliferative GI50 values for PI 103 ranged 37 fold from 22 nmol/L to 827 nmol/L, the IC50 values for the inhibition of phosphorylation of Ser473 on AKT after 2 hour exposure ranged just 2 fold from 18 nmol/L to 38 nmol/L for. In case of GDC 0941, the anti-proliferative GI50 values ranged 9 fold from 180 nmol/L to 1,627 nmol/L, whereas the IC50 values for inhibition of AKT phosphorylation on Ser473 following 2 hour treatment again ranged only 2 fold from 14 nmol/L to 33 nmol/L. When these for your colon cancer lines are considered alongside the ovarian cancer and glioblastoma cell data, it is obvious that the degree of phosphatidylinositide 3 kinase inhibition is remarkably similar across all cancer cell lines, whereas the consequences in terms of antiproliferative potency are completely different, indicating a differential antiproliferative reaction to certain degree of phosphatidylinositide 3 kinase blockade.