Overcoming radio-resistance in esophageal squamous cell carcinoma via hypermethylation of PIK3C3 promoter region mediated by KDM5B loss.

Many patients with esophageal squamous cell carcinoma (ESCC) are inoperable because of old age or the advanced stage of the disease; thus radio- and chemotherapy are believed as the standard treatments for these patients. However, due to the radio-resistance of tumor cells that may develop during radiotherapy, results remain unsatisfactory. In this article, the possible relationship between the expression of lysine demethylase 5B (KDM5B) and ESCC radio-resistance is clarified, and the underlying mechanism is evaluated. Using the GSE75241 microarray, we identified KDM5B as a potential oncogene in ESCC. KDM5B was overexpressed in ESCC patients and cells. Inhibition of KDM5B enhanced the H3K4me3 methylation of phosphatidylinositol 3-kinase catalytic subunit type 3 (PIK3C3) promoter and induced the expression of PIK3C3. Knockdown of KDM5B or overexpression of PIK3C3 in KYSE-150 and TE-10 cells promoted apoptosis, cell cycle arrest, autophagy, and increased sensitivity to radiotherapy. Silencing of PIK3C3 attenuated the promoting effect of sh-KDM5B on the sensitivity of ESCC cells to radiotherapy. The inhibition of sh-KDM5B in radio-resistance of ESCC cells was also reproduced in vivo. Taken together, our findings provide evidence that reduced expression of KDM5B has a critical role in promoting ESCC radio-sensitivity by upregulating PIK3C3, suggesting KDM5B may function as an oncogene in ESCC.

Corynoxine B derivative CB6 prevents Parkinsonian toxicity in mice by inducing PIK3C3 complex-dependent autophagy.

Increasing evidence shows that autophagy impairment is involved in the pathogenesis and progression of neurodegenerative diseases including Parkinson's disease (PD). We previously identified a natural alkaloid named corynoxine B (Cory B) as a neuronal autophagy inducer. However, its brain permeability is relatively low, which hinders its potential use in treating PD. Thus we synthesized various derivatives of Cory B to find more potent autophagy inducers with improved brain bioavailability. In this study, we evaluated the autophagy-enhancing effect of CB6 derivative and its neuroprotective action against PD in vitro and in vivo. We showed that CB6 (5-40 µM) dose-dependently accelerated autophagy flux in cultured N2a neural cells through activating the PIK3C3 complex and promoting PI3P production. In MPP+-treated PC12 cells, CB6 inhibited cell apoptosis and increased cell viability by inducing autophagy. In MPTP-induced mouse model of PD, oral administration of CB6 (10, 20 mg· kg-1· d-1, for 21 days) significantly improved motor dysfunction and prevented the loss of dopaminergic neurons in the striatum and substantia nigra pars compacta. Collectively, compound CB6 is a brain-permeable autophagy enhancer via PIK3C3 complex activation, which may help the prevention or treatment of PD.

Ischemic preconditioning protects against liver ischemia/reperfusion injury via heme oxygenase-1-mediated autophagy.

OBJECTIVES: Ischemic preconditioning exerts a protective effect in hepatic ischemia/reperfusion injury. The exact mechanism of ischemic preconditioning action remains largely unknown. Recent studies suggest that autophagy plays an important role in protecting against ischemia/reperfusion injury. However, the role of autophagy in ischemic preconditioning-afforded protection and its regulatory mechanisms in liver ischemia/reperfusion injury remain poorly understood. This study was designed to determine whether ischemic preconditioning could protect against liver ischemia/reperfusion injury via heme oxygenase-1-mediated autophagy. DESIGN: Laboratory investigation. SETTING: University animal research laboratory. SUBJECTS: Male inbred Lewis rats and C57BL/6 mice. INTERVENTIONS: Ischemic preconditioning was produced by 10 minutes of ischemia followed by 10 minutes of reperfusion prior to 60 minutes of ischemia. In a rat model of hepatic ischemia/reperfusion injury, rats were pretreated with wortmannin or rapamycin to evaluate the contribution of autophagy to the protective effects of ischemic preconditioning. Heme oxygenase-1 was inhibited with tin protoporphyrin IX. In a mouse model of hepatic ischemia/reperfusion injury, autophagy or heme oxygenase-1 was inhibited with vacuolar protein sorting 34 small interfering RNA or heme oxygenase-1 small interfering RNA, respectively. MEASUREMENTS AND MAIN RESULTS: Ischemic preconditioning ameliorated liver ischemia/reperfusion injury, as indicated by lower serum aminotransferase levels, lower hepatic inflammatory cytokines, and less severe ischemia/reperfusion-associated histopathologic changes. Ischemic preconditioning treatment induced autophagy activation, as indicated by an increase of LC3-II, degradation of p62, and accumulation of autophagic vacuoles in response to ischemia/reperfusion injury. When ischemic preconditioning-induced autophagy was inhibited with wortmannin in rats or vacuolar protein sorting 34-specific small interfering RNA in mice, liver ischemia/reperfusion injury was worsened, whereas rapamycin treatment increased autophagy and mimicked the protective effects of ischemic preconditioning. Furthermore, ischemic preconditioning increased heme oxygenase-1 expression. The inhibition of heme oxygenase-1 with tin protoporphyrin IX in rats or heme oxygenase-1-specific small interfering RNA in mice decreased ischemic preconditioning-induced autophagy and diminished the protective effects of ischemic preconditioning against ischemia/reperfusion injury. CONCLUSIONS: Ischemic preconditioning protects against liver ischemia/reperfusion injury, at least in part, via heme oxygenase-1-mediated autophagy.

Autophagy inhibition switches low-dose camptothecin-induced premature senescence to apoptosis in human colorectal cancer cells.

Recently, several studies indicated that senescent tumor cells are resistant to apoptosis in chemotherapy. They may return to cell cycle, thus act as stumbling blocks in anticancer treatments. In the present study, we found that, in human colorectal cancer cells, low-dose camptothecin (CPT) simultaneously induced autophagy and premature senescence through AMPK-TSC2-mTOR pathway and ATM-Chk2-p53-p21 pathway respectively. What's important is the suppression of autophagy substantially increased apoptosis and greatly attenuated senescence possibly by blocking p53/p21 pathway, which suggests that autophagy plays an indispensable role in sustaining cell senescence caused by low-dose CPT. The combination of low-dose CPT and autophagy inhibitor, a way to lead senescent cells to die, would be potentially valuable in cancer therapy.