RT Journal Article
SR Electronic
T1 Enhanced TLR4 Expression on Colon Cancer Cells After Chemotherapy Promotes Cell Survival and Epithelial–Mesenchymal Transition Through Phosphorylation of GSK3β
JF Anticancer Research
JO Anticancer Res
FD International Institute of Anticancer Research
SP 3383
OP 3394
VO 36
IS 7
A1 YOON HEE CHUNG
A1 DAEJIN KIM
YR 2016
UL http://ar.iiarjournals.org/content/36/7/3383.abstract
AB Background: Phosphorylation of glycogen synthase kinase 3β (GSK3β) by phosphatidyl-inositide 3-kinase (PI3K)/protein kinase B (AKT) or inhibition of GSK3β with small-molecule inhibitor attenuates cell survival and proliferation and increases apoptosis in most cancer cell lines. In this study, we investigated the role of phosphorylated GSK3β activated by enhanced toll-like receptor 4 (TLR4) expression in drug-treated colon cancer cells as a model of post-chemotherapy cancer cells. Materials and Methods: The effect of TLR4 stimulation on metastasis and apoptosis in drug-exposed colon cancer cells was determined by real-time polymerase chain reaction (PCR) and immunoblotting. Results: Despite the induction of apoptosis after treatment with oxaliplatin and 5-fluorouracil, lipopolysaccharide (LPS) stimulation via increased TLR4 in drug-treated cancer cells effectively inhibited apoptosis through up-regulation of expression of anti-apoptosis-related B-cell lymphoma 2 (BCL2) family proteins [X-linked inhibitor of apoptosis protein (XIAP), BCL2, and survivin] and drug-resistance proteins [multidrug-resistance protein 1 (MDR1), multidrug resistance-associated protein (MRP)1/2/3]. LPS-mediated signaling in drug-treated cancer cells elevated the expression of phosphorylated GSK3β, extracellular signal–regulated kinase (ERK), and the p65 subunit of nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB). Pharmacological inhibition of GSK3β (using SB216763) reduced phosphorylation of GSK3β, re-activated caspase-dependent apoptosis, and blocked the expression of cancer stem cell markers and invasive characteristics in LPS-stimulated drug-treated cells. In addition, the ERK-specific inhibitor, PD98059, triggered the apoptosis of TLR4-activated drug-exposed colon cancer cells, whereas there was no effect on the expression of epithelial–mesenchymal transition markers or GSK3β phosphorylation. Conclusion: These results suggest that TLR4-induced GSK3β and ERK phosphorylation independently controls cancer cell survival and regulation of GSK3β and ERK after chemotherapy, making TLR4 a critical target for reducing drug resistance and metastasis in patients with colon cancer.