Date of Award

10-31-2022

Degree Type

Thesis

Degree Name

MPhil in Biological and Biomedical Sciences

First Advisor

Dr. Kulsoom Ghias

Second Advisor

Dr. Azhar Hussain

Third Advisor

Dr. Mati Ur Rehman

Department

Biological and Biomedical Sciences

Abstract

Purpose: 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. In majority of cancers including CRCs, the phosphatidylinositol 3-kinase(PI3K)/AKT/mTOR pathway is frequently found to be constitutively activated and anti[1]apoptotic protein XIAP is also dysregulated. Targeting the PI3K/AKT/mTOR pathwaythrough specific inhibitors may overcome chemoresistance and altered cell proliferation. The current study examines the effect of oxaliplatin, and inhibitors of PI3K (LY294002), mTORC2 (Torin 2) and XIAP (Embelin) in an oxaliplatin-resistant colorectal cancer cell line.
Methods: 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 and XIAP proteins. Cell cycle and apoptosis assays were conducted to determine the fate of cells following different treatments.
Results: 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-116OXRcells underwent a G1 phase cell cycle arrest rather than apoptosis as measured by flow cytometry analysis.
Conclusion: 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.

First Page

1

Last Page

52

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