Abstract
BACKGROUND: Esophageal squamous cell carcinoma (ESCC) is a malignant tumor with high morbidity and mortality, and easy to develop resistance to chemotherapeutic agents. Telomeres are DNA-protein complexes located at the termini of chromosomes in eukaryotic cells, which are unreplaceable in maintaining the stability and integrity of genome. Telomerase, an RNA-dependent DNA polymerase, play vital role in telomere length maintain, targeting telomerase is a promising therapeutic strategy for cancer. AIM: To investigate the efficacy and underlying mechanisms of BIBR1532, a telomerase inhibitor, in ESCC. METHODS: KYSE150 and KYSE410 cells were cultured and exposed to various concentrations of BIBR1532. Cell viability was assessed at 48 hours and 72 hours to determine the IC(50) values. The effects of BIBR1532 on ESCC cell proliferation, migration, and cellular senescence were evaluated using the cell counting kit-8 assay, plate colony formation assay, scratch assay, transwell assay, and β-galactosidase staining, respectively. Western blotting was performed to detect the expression of proteins in BIBR1532-treated ESCC cells, such as human telomerase reverse transcriptase (hTERT), key molecules involved in DNA damage response (DDR) or cellular senescence, as well as telomere-binding proteins. Additionally, a tumor-bearing nude mouse model was established to evaluate the anti-cancer effect of BIBR1532 in vivo. RESULTS: The IC(50) values for KYSE150 and KYSE410 cells after 48 hours of BIBR1532 exposure were 48.53 μM and 39.59 μM, respectively. These values decreased to 37.22 μM and 22.71 μM, respectively, following a longer exposure of 72 hours. BIBR1532 exhibited dose-dependent effects on KYSE150 and KYSE410 cells, including decreased hTERT expression, inhibition of proliferation and metastasis, and induction of cellular senescence. Mechanistically, BIBR1532 upregulated the expression of the DDR protein, γ-H2AX, and activated the ataxia telangiectasia and Rad3-related protein (ATR)/ check point kinase 1 (CHK-1) and ataxia-telangiectasia mutated gene (ATM)/CHK2 pathways. BIBR1532 downregulated the expression of telomere-binding proteins, including telomeric-repeat binding factor 1 (TRF1), TRF2, protection of telomeres 1, and TIN2-interacting protein 1. In a nude mouse xenograft model, BIBR1532 significantly suppressed tumor growth, reduced hTERT expression, and increased γ-H2AX protein levels. Hematoxylin and eosin staining of various organs, including the heart, liver, spleen, lungs, and kidneys, revealed no apparent adverse effects. CONCLUSION: BIBR1532 exerts anti-cancer effects on ESCC by inducing DDR through the ATR/CHK1 and ATM/CHK2 pathways and downregulating the expression of telomere-binding proteins.