Salinomycin has been shown to control breast cancer stem cells, although the mechanisms underlying its anticancer effects are not clear. Deregulation of cell cycle regulators play critical roles in tumorigenesis, and they have been considered as anticancer targets. In this study, we investigated salinomycin effect on cell cycle progression using OVCAR-8 ovarian cancer cell line and multidrug-resistant NCI/ADR-RES and DXR cell lines that are derived from OVCAR-8. Parental OVCAR-8 cells are sensitive to several anticancer drugs, but NCI/ADR-RES and DXR cells are resistant to several anticancer drugs. However, salinomycin caused cell growth inhibition and apoptosis via cell cycle arrest at G1 in all three cell lines. Salinomycin inhibited signal transducer and activator of transcription 3 (Stat3) activity and thus decreased expression of Stat3-target genes, including cyclin D1, Skp2, and survivin. Salinomycin induced degradation of Skp2 and thus accumulated p27Kip1. Knockdown of Skp2 further increased salinomycin-induced G1 arrest, but knockdown of p27Kip1 attenuated salinomycin effect on G1 arrest. Cdh1, an E3 ligase for Skp2, was shifted to nuclear fractions upon salinomycin treatment. Cdh1 knockdown by siRNA reversed salinomycin-induced Skp2 downregulation and p27Kip1 upregulation, indicating that salinomycin activates the APC^Cdh1–Skp2–p27Kip1 pathway. Concomitantly, si-Cdh1 inhibited salinomycin-induced G1 arrest. Taken together, our data indicate that salinomycin induces cell cycle arrest and apoptosis via downregulation or inactivation of cell cycle-associated oncogenes, such as Stat3, cyclin D1, and Skp2, regardless of multidrug resistance.

Summary: Background: Anti‐viral therapy is not indicated for patients with chronic hepatitis B (CHB) in the immune‐tolerant phase.Aims: To investigate the cumulative incidence of phase change and hepatocellular carcinoma (HCC) and independent predictors for phase change in patients with CHB in immune‐tolerant phase.Methods: In total, 946 patients in immune‐tolerant phase, defined as hepatitis B e antigen positivity, HBV‐DNA >20 000 IU/mL and alanine aminotransferase (ALT) ≤40 IU/L, between 1989 and 2017 were enrolled from eight institutes.Results: The mean age of study population (429 men and 517 women) was 36.7 years. The mean ALT and HBV‐DNA levels were 24.6 IU/L and 8.50 log₁₀ IU/mL, respectively. Of the study population, 476 (50.3%) patients remained in immune‐tolerant phase throughout the study period (median: 63.6 months). The cumulative incidence rates of phase change and HCC at 10 years were 70.7% and 1.7%, respectively. Multivariate analyses revealed that HBV‐DNA level >10⁷ IU/mL was associated independently with a reduced risk of phase change (hazard ratio [HR] = 0.734, P = 0.008), whereas a high ALT level, above the cut‐off recommended in the Korean Association for the Study of the Liver guidelines (34 IU/L for men and 30 IU/L for women), was associated independently with a greater risk of phase change (HR = 1.885, P < 0.001).Conclusions: The criterion of HBV‐DNA level > 10⁷ IU/mL may be useful to define immune‐tolerant phase. In addition, an extremely low risk of HCC development was observed in patients with CHB in immune‐tolerant phase.

The cellular response to DNA damage is emerging as a promising target for cancer therapy. In the present study, the authors exploited the relationship between the level of the phosphorylated form of histone H2AX (γH2AX) and the extent of DNA damage and developed a quantitative, cell-based, high-content screening system for measuring the DNA damage response (DDR). In this system, the authors quantified the level of γH2AX by measuring DNA damage–induced γH2AX nuclear foci using an automated cell imager. They found that the total area of γH2AX foci per cell exhibited a good correlation with the concentration of DNA damage–inducing agents, including etoposide. The effects of 2 well-known inhibitors of DNA damage could be quantified using this system, suggesting the suitability of the γH2AX-foci quantification method for large-scale screening applications. This was confirmed by using this method to screen a chemical library; the resulting “hits” included compounds that inhibited early signaling events in DDR, as well those that inhibited subsequent DNA damage repair processes. Overall, this γH2AX foci-measuring system may be an effective screening method for identifying DNA damage response inhibitors that could eventually be used to develop novel anticancer drugs.