Abstract 2549: Targeting PI3Kinase AKT pathway and anti-apoptotic protein XIAP in chemotherapy-resistant colorectal cancer cells
Authors: Akbar Rozmeen , Rehman Mati Ur , Khan Asra , Belgaumi Numair , Farooqui Iman M. , Arain Aafia S. , Rajabali Azhar Hussain , Ghias Kulsoom 
Published: April 2023

Abstract
Colorectal Cancer (CRC) ranks among the top three cancers worldwide in terms of incidence and mortality. Treatment of CRC with 5-fluorouracil and oxaliplatin has shown limited efficacy, with resistance often developing to this treatment. Therefore, there is an urgency to identify druggable molecular pathways/proteins that can be efficiently targeted either alone or in combination with chemotherapy to efficiently treat these cancers. In majority of cancers including CRCs, the phosphatidylinositol 3-kinase (PI3K)/AKT/mTOR pathway is frequently found to be constitutively activated leading to poor overall survival. In addition, over expression of the anti-apoptotic protein XIAP has also been shown to induce resistance to chemotherapeutic agents leading to poor prognosis in many epithelial cancers including CRC. Targeting the PI3K/AKT/mTOR pathway and expression of XIAP through specific inhibitors may overcome chemoresistance and altered cell proliferation. The current study examines the effect of oxaliplatin, and inhibitors of PI3K (LY294002) and XIAP (Embelin) in an transiently produced oxaliplatin-resistant colorectal cancer cell line. Transient resistance was induced in CRC cell line HCT116 by intermittent treatment with 25μM oxaliplatin. The anti-proliferative effects of oxaliplatin, Embelin, LY294002 and Torin 2 were determined using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Western blots were performed to determine the expression of phosphorylated AKT, XIAP and caspase-3 proteins. Cell cycle and apoptosis assays were performed by flow cytometry to determine the fate of cells following different treatments. Transient resistance was developed in HCT-116 cells (termed HCT-116OXR) after treatment with 25μM oxaliplatin as confirmed by cell viability assays and immunoblotting that showed activation of phospho-AKT and upregulation of XIAP in the transiently resistant cells. HCT116OXR cells responded to treatment with LY294002 and Embelin as compared to parental HCT-116 cells (termed HCT-116WT). Following treatment with LY294002 or Embelin alone or in combination for 48hrs, HCT-116OXR cells underwent a G1 phase cell cycle arrest rather than apoptosis as measured by flow cytometry analysis. The data suggests that PI3K/AKT pathway and XIAP inhibitors cause cell cycle arrest and decreased cell viability in oxaliplatin resistant colorectal cancer cells, which may have implications for treatment of chemotherapy resistant CRC.
Citation Format: Rozmeen Akbar, Mati Ur Rehman, Asra Khan, Numair Belgaumi, Iman M. Farooqui, Aafia S. Arain, Azhar Hussain Rajabali, Kulsoom Ghias. Targeting PI3Kinase AKT pathway and anti-apoptotic protein XIAP in chemotherapy-resistant colorectal cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2549.