The Functional Roles Of TIGAR In The Progression Of Esophageal Squamous Cell Carcinoma

Background&Aims:Our previous whole-genome sequencing in esophageal squamous-cell carcinoma(ESCC)has identified 23 focal regions with recurrent gain of copy number that contain 1591 genes.Further integrative analysis of copy number alterations and mRNA expression levels showed 149 copy-number amplified genes that had higher mRNA levels,suggesting an important role of these genes in ESCC.This study was to investigate the functional roles of these genes and their potential as biomarkers and therapeutic targets for ESCC.Methods:A siRNA library was used to knock down all these 149 genes in ESCC cells and the changes of malignant phenotypes of these cancer cells were examined by using a high-throughput imaging method and in vitro proliferation and colony formation assays.The acting mechanisms of the interest genes on malignant phenotypes of cells were explored using biochemical and molecular biological assays.Effect of the amplified genes on sensitivity of cancer cells to anticancer agents were examined in vitro and in vivo in mice.Results:We found that among the 149 examined genes,TIGAR was the top one influencing ESCC cell proliferation in vitro and in vivo in xenografts.We confirmed that TIGAR can inhibit glycolysis and divert the carbon flux into the pentose phosphate pathway(PPP)to produce ribose-5-phosphate(R5P)for nuclear synthesis and NADPH to maintain cellular redox status.Overexpression of TIGAR activated p-AMPK that regulated mRNA translation and glutamine-dependent mitochondrial metabolism to maintain energy balance in cells with a reduced glycolysis ability,which was responsible for energy production under normal conditions.We found that ESCC cells overexpressing TIGAR had an addiction to glutamine metabolism and were sensitive to glutaminase inhibitors.Glutamine restriction or glutaminase inhibitor had a synergistic effect with 5-Fluorouracil on killing of ESCC cells,suggesting that glutaminase inhibitors may be used as adjuvant agents for treatment of ESCC with TIGAR amplification.Conclusion:These results suggest that amplification or overexpression of TIGAR may prevent ESCC cells from killing by anticancer drugs and thus may represent a therapeutic target for ESCC.