Inhibition of Phospho-S6 Kinase, a Protein Involved in the Compensatory Adaptive Response, Increases the Efficacy of Paclitaxel in Reducing the Viability of Matrix-Attached Ovarian Cancer Cells.


To identify the proteins involved the compensatory adaptive response to paclitaxel in ovarian cancer cells and to determine whether inhibition of the compensatory adaptive response increases the efficacy of paclitaxel in decreasing the viability of cancer cells.


We used a reverse-phase protein array and western blot analysis to identify the proteins involved in the compensatory mechanism induced by paclitaxel in HeyA8 and SKOV3 ovarian cancer cells. We used a cell viability assay to examine whether inhibition of the proteins involved in the compensatory adaptive response influenced the effects of paclitaxel on cancer cell viability. All experiments were performed in three-dimensional cell cultures.


Paclitaxel induced the upregulation of pS6 (S240/S244) and pS6 (S235/S236) in HeyA8 and SKOV3 cells, and pPRAS40 (T246) in HeyA8 cells. BX795 and CCT128930 were chosen as inhibitors of pS6 (S240/S244), pS6 (S235/S236), and pPRAS40 (T246). BX795 and CCT128930 decreased pS6 (S240/S244) and pS6 (S235/S236) expression in HeyA8 and SKOV3 cells. However, pPRAS40 (T246) expression was inhibited only by BX795 and not by CCT128930 in HeyA8 cells. Compared with paclitaxel alone, addition of BX795 or CCT128930 to paclitaxel was more effective in decreasing the viability of HeyA8 and SKOV3 cells.


Addition of BX795 or CCT128930 to inhibit pS6 (S240/S244) or pS6 (S235/S236) restricted the compensatory adaptive response to paclitaxel in HeyA8 and SKOV3 cells. These inhibitors increased the efficacy of paclitaxel in reducing cancer cell viability.

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Cat.No. Product Name Information
S1150 Paclitaxel (NSC 125973) Paclitaxel (NSC 125973, PTX, Taxol, Onxal, Abraxane) is a microtubule polymer stabilizer with IC50 of 0.1 pM in human endothelial cells.
S1274 BX-795 BX-795 is a potent and specific PDK1 inhibitor with IC50 of 6 nM, 140- and 1600-fold more selective for PDK1 than PKA and PKC in cell-free assays, respectively. Meanwhile, in comparison to GSK3β more than 100-fold selectivity observed for PDK1. BX-795 modulates autophagy via inhibiting ULK1. BX-795 also is a potent TBK1 inhibitor that blocks both TBK1 and IKKε with IC 50 values of 6 nM and 41 nM, respectively.
S2635 CCT128930 CCT128930 is a potent, ATP-competitive and selective inhibitor of Akt2 with IC50 of 6 nM in a cell-free assay, 28-fold greater selectivity for Akt2 than the closely related PKA kinase. CCT128930 induces cell cycle arrest, DNA damage, and autophagy independent of Akt inhibition. High dose of CCT128930 triggers cell apoptosis in HepG2 cells.
S1558 AT7867 AT7867 is a potent ATP-competitive inhibitor of Akt1/2/3 and p70S6K/PKA with IC50 of 32 nM/17 nM/47 nM and 85 nM/20 nM in cell-free assays, respectively; little activity outside the AGC kinase family.

Related Targets

PDK Autophagy IκB/IKK Microtubule Associated Akt S6 Kinase