Stress-induced reversible cell-cycle arrest requires PRC2/PRC1-mediated control of mitophagy in Drosophila germline stem cells and human iPSCs.

Following acute genotoxic stress, both normal and tumorous stem cells can undergo cell-cycle arrest to avoid apoptosis and later re-enter the cell cycle to regenerate daughter cells. However, the mechanism of protective, reversible proliferative arrest, "quiescence," remains unresolved. Here, we show that mitophagy is a prerequisite for reversible quiescence in both irradiated Drosophila germline stem cells (GSCs) and human induced pluripotent stem cells (hiPSCs). In GSCs, mitofission (Drp1) or mitophagy (Pink1/Parkin) genes are essential to enter quiescence, whereas mitochondrial biogenesis (PGC1α) or fusion (Mfn2) genes are crucial for exiting quiescence. Furthermore, mitophagy-dependent quiescence lies downstream of mTOR- and PRC2-mediated repression and relies on the mitochondrial pool of cyclin E. Mitophagy-dependent reduction of cyclin E in GSCs and in hiPSCs during mTOR inhibition prevents the usual G1/S transition, pushing the cells toward reversible quiescence (G0). This alternative method of G1/S control may present new opportunities for therapeutic purposes.

Prospective validation of the Chinese University Prognostic Index and comparison with other staging systems for hepatocellular carcinoma in an Asian population.

BACKGROUND AND AIM: Hepatitis B viral (HBV) infection is the predominant etiology of hepatocellular carcinoma (HCC) in Asia. Our group previously reported a staging system known as the Chinese University Prognostic Index (CUPI) for HCC populations of which HBV infection is the predominant etiology. This study aims to validate CUPI and compare with other published staging systems. METHODS: We analyzed a prospective cohort of patients with newly diagnosed HCC from 2003 to 2005. All patients were staged with CUPI, Barcelona Clinic Liver Cancer Classification (BCLC), Cancer of the Liver Italian Program score (CLIP), tumor-node-metastasis (TNM) and Okuda systems at diagnosis. They were followed with survival data and the performance of each staging system (in terms of homogeneity, discriminatory ability and monotonicity of gradient) were analyzed and compared. RESULTS: A total of 595 patients (80.2% with chronic HBV infection) were analyzed. The median follow-up was 41.4 months and the median survival was 6.6 months. Multivariate analyses identified symptomatic disease, ascites, vascular involvement, Child-Pugh-stage, alpha-fetoprotein and treatment to be the independent prognostic factors. CUPI could identify three groups with statistically significant survival difference (P < 0.0001). Both CUPI and CLIP had the most favorable performance in terms of discriminatory ability, homogeneity and monotonicity. CUPI performed the best in predicting 3-month survival while CLIP performed better in predicting the outcome of 6- and 12-month survival rate. BCLC was inferior to CLIP and CUPI in the overall performance. CONCLUSION: We have validated CUPI in a population composed of predominant HBV-related HCC. CUPI is an appropriate staging system for HBV-related HCC. In patients with advanced HCC, both CUPI and CLIP offer good risk stratification.

Hepatitis B virus reactivation in lymphoma patients with prior resolved hepatitis B undergoing anticancer therapy with or without rituximab.

PURPOSE: Reactivation of hepatitis B virus (HBV) infection is a well-recognized complication in cancer patients with chronic HBV (hepatitis B surface antigen [HBsAg] positive) undergoing cytotoxic chemotherapy. In patients who have resolved HBV (HBsAg negative and antibody to hepatitis B core antigen [anti-HBc] +/- antibody to hepatitis B surface antigen [anti-HBs] positive), such incidence has been much less common until recent use of rituximab. In this study on HBsAg-negative/anti-HBc-positive lymphoma patients, the objectives were to determine the HBV reactivation rate in patients treated with rituximab-containing chemotherapy and to compare it with the rate in patients treated without rituximab. PATIENTS AND METHODS: Between January 2003 and December 2006, all patients diagnosed with CD20(+) diffuse large B-cell lymphoma (DLBCL) had HBsAg determined before anticancer therapy. They were treated with either cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) alone or rituximab plus CHOP (R-CHOP). HBsAg-negative patients had anti-HBc determined; serum was stored for anti-HBs and HBV DNA. All patients were observed for HBV reactivation, which was defined as detectable HBV DNA with ALT elevation during and for 6 months after anticancer therapy. RESULTS: Among 104 CD20(+) DLBCL patients, 80 were HBsAg negative. Of the latter, 46 patients (44.2%) were HBsAg negative/anti-HBc positive; 25 of these patients were treated with CHOP, and none had HBV reactivation. In contrast, among the 21 patients treated with R-CHOP, five developed HBV reactivation, including one patient who died of hepatic failure (P = .0148). Exploratory analysis identified male sex, absence of anti-HBs, and use of rituximab to be predictive of HBV reactivation. CONCLUSION: Among HBsAg-negative/anti-HBc-positive DLBCL patients treated with R-CHOP, 25% developed HBV reactivation. Close monitoring until at least 6 months after anticancer therapy is required, with an alternative approach of prophylactic antiviral therapy to prevent this potentially fatal condition.