Abstract. The polyphenol (-)-epigallocatechin-3-gallate (EGCG) is a green tea constituent, which has been shown to inhibit cancer cell growth in vitro, in vivo and in epidemiological studies. In this study, we investigated its effects in gastric cancer cell lines. Five gastric cancer cell lines, the MKN-1, MKN-28, MKN-45, NUGC-3 and TMK-1, were found to be sensitive to EGCG treatment. Of all the cell lines tested, NUGC-3 was the most sensitive. EGCG treatment of NUGC-3 cells induced apoptosis, which was confirmed by sub-G1 analysis, caspase-Glo assay and Western blotting against cleaved PARP and cleaved caspase-3. EGCG treatment lowered survivin and increased Bax and TRAIL expression. Furthermore, EGCG induced p73 activation in NUGC-3 cells. Small interfering RNA against p73 diminished EGCG effects on survivin expression and cell viability. These results show that EGCG induces cell death in gastric cancer cells by apoptosis via inhibition of survivin expression downstream of p73. This study provides a novel mechanism whereby EGCG potentially inhibits cancer cell growth, concluding that EGCG may be a potential candidate in anti-survivin cancer therapy.
Introduction: Highly sensitive reagents for detecting SARS-CoV-2 antigens have been developed for accurate and rapid diagnosis till date. In this study, we aim to clarify the frequency of false-positive reactions and reveal their details in SARS-CoV-2 quantitative antigen test using an automated laboratory device. Methods: Nasopharyngeal swab samples (n = 4992) and saliva samples (n = 5430) were collected. We measured their SARS-CoV-2 antigen using Lumipulse® Presto SARS-CoV-2 Ag and performed a nucleic acid amplification test (NAAT) using the Ampdirect™ 2019 Novel Coronavirus Detection Kit as needed. The results obtained from each detection test were compared accordingly. Results: There were 304 nasopharyngeal samples and 114 saliva samples were positive in the Lumipulse® Presto SARS-CoV-2 Ag test. All positive nasopharyngeal samples in the antigen test were also positive for NAAT. In contrast, only three (2.6%) of all the positive saliva samples in the antigen test were negative for NAAT. One showed no linearity with a dilute solution in the dilution test. Additionally, the quantitative antigen levels of all the three samples did not decrease after reaction with the anti-SARS-CoV-2 antibody. Conclusions: The judgment difference between the quantitative antigen test and NAAT seemed to be caused by non-specific reactions in the antigen test. Although the high positive and negative predictive value of this quantitative antigen test could be confirmed, we should consider the possibility of false-positives caused by nonspecific reactions and understand the characteristics of antigen testing. We recommend that repeating centrifugation before measurement, especially in saliva samples, should be performed appropriately.
Alterations in the mRNA expression or the mutation of previously reported tyrosine kinases have been detected only in a limited number of patients with acute leukemia. In this study, we examined whether the widely expressed serine threonine tyrosine kinase 1 (STYK1)/novel oncogene with kinase domain (NOK) acts as a drug resistance factor in acute leukemia. The transfection of leukemic HL-60 cells with an STYK1 expression vector resulted in the resistance to doxorubicin and etoposide and decreased drug-induced caspase-3/7 activity and sub-G1 population. To investigate the mechanism of STYK1-induced drug resistance, microarray analysis was performed using HL-60 cells transfected with control or STYK1 expression vectors. Three tyrosine kinases (EphA4, FLT4 and STK31), two NF-κB inducers (MAPK4 and TNF-RSF11A), and two genes essential for stem cell replication (SALL4 and NOV) were identified as novel STYK1-induced genes. In addition to the data using cell line, a comparison of the leukemic patients who did and did not respond to therapy revealed that STYK1 expression before therapy was significantly higher in the non-responder group compared with the group that responded completely. These results suggest that STYK1 is a novel drug resistance factor and could be a predictor of the therapeutic response in acute leukemia.
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