Abstract 1044: GSK690693 enhances Celecoxib mediated apoptosis by an Akt mediated pathway in colon cancer.
Authors: Pal Ipsita , Mandal Mahitosh 
Published: August 2014

Background: Overexpression and activation of Akt are often associated with resistance of tumor towards chemotherapy. Celecoxib a selective Cox-2 inhibitor is found to prevent malignancies by inhibiting Cox-2 and in a lower extent PI3K-Akt signaling pathway. However, long-term administration of Celecoxib at high doses is associated with gastrointestinal and cardiovascular side effects. GSK690693 is a potent and selective, ATP-competitive, pan-Akt kinase inhibitor currently in clinical development for patients with various malignancies. The aim of our study is to investigate the combinatorial effects of Celecoxib and GSK690693 by means of increased chemo preventive measure by down regulation of Akt pathway with induction of apoptosis and to minimize toxicity for prevention of colorectal cancer.

Material and Methods: Cell viability and cell proliferation was measured by MTT assay and FACS respectively. The morphology analysis in combined or individual drug treated cells was assessed by DAPI staining and TUNEL Assay. Western blot experiments were done to check the expression profile of apoptotic proteins and degree of phosphorylation of Akt and downstream targets. Cells were transfected with Akt-SiRNA with Lipofectamine and FACS was performed on both single and combined drugs treated cells.

Results: Combination of Celecoxib and GSK690693 showed an enhanced cytotoxicity on HT29 and HCT116 cell lines after drug treatment. FACS analysis showed substantial sub G0/ G1 accumulation of cells indicating apoptosis which is supported by facts like characteristic morphological changes (cell shrinkage and nuclear fragmentation) and increase in TUNEL positive cells. The induction of apoptosis caused down regulation of anti apoptotic proteins Bcl-2 and Bcl-XL, increase in proapoptotic proteins BAX and Caspase-3 mediated poly (ADP-ribose) polymerase cleavage. Western blot analysis showed that the combined drug treatment augmented suppression of pAKT and its downstream targets. Down regulation of AKT with Akt SiRNA induced apoptosis and caused subG0/G1 peak in combined drug treated sample than vector treated sample.

Discussion: Here we demonstrated that the extent of celecoxib induced apoptosis can be enhanced by combinatorial approach involving GSK690693 which targets Akt. Besides it also reduces the high dose of celecoxib through an Akt mediated pathway and thereby decreases the side effects of celecoxib, thus potentially augmenting the therapeutic benefit of combining celecoxib and GSK690693 towards treatment of colon cancer.

Citation Format: Ipsita Pal, Mahitosh Mandal, Mandal et al. GSK690693 enhances Celecoxib mediated apoptosis by an Akt mediated pathway in colon cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1044. doi:10.1158/1538-7445.AM2013-1044

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.