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Hepatocellular carcinoma (HCC) exhibits cellular heterogeneity and embryonic stem‐cell–related genes are preferentially overexpressed in a fraction of cancer cells of poorly differentiated tumors. However, it is not known whether or how these cancer cells contribute to tumor initiation and progression. Here, our data showed that increased expression of pluripotency transcription factor Nanog in cancer cells correlates with a worse clinical outcome in HCC. Using the Nanog promoter as a reporter system, we could successfully isolate a small subpopulation of Nanog‐positive cells. We demonstrate that Nanog‐positive cells exhibited enhanced ability of self‐renewal, clonogenicity, and initiation of tumors, which are consistent with crucial hallmarks in the definition of cancer stem cells (CSCs). NanogPos CSCs could differentiate into mature cancer cells in in vitro and in vivo conditions. In addition, we found that NanogPos CSCs exhibited resistance to therapeutic agents (e.g., sorafenib and cisplatin) and have a high capacity for tumor invasion and metastasis. Knock‐down expression of Nanog in NanogPos CSCs could decrease self‐renewal accompanied with decreased expression of stem‐cell–related genes and increased expression of mature hepatocyte‐related genes. Overexpression of Nanog in NanogNeg cells could restore self‐renewal. Furthermore, we found that insulin‐like growth factor (IGF)2 and IGF receptor (IGF1R) were up‐regulated in NanogPos CSCs. Knock‐down expression of Nanog in NanogPos CSCs inhibited the expression of IGF1R, and overexpression of Nanog in NanogNeg cells increased the expression of IGF1R. A specific inhibitor of IGF1R signaling could significantly inhibit self‐renewal and Nanog expression, indicating that IGF1R signaling participated in Nanog‐mediated self‐renewal. Conclusion: These data indicate that Nanog could be a novel biomarker for CSCs in HCC, and that Nanog could play a crucial role in maintaining the self‐renewal of CSCs through the IGF1R‐signaling pathway. (HEPATOLOGY 2012;56:1004–1014)

Summary Background: To date, large amounts of epidemiological and case study data have been available for the Coronavirus Disease 2019 (COVID-19), which suggested that the mortality was related to not just respiratory complications. Here, we specifically analyzed kidney functions in COVID-19 patients and their relations to mortality. Methods: In this multi-centered, retrospective, observational study, we included 193 adult patients with laboratory-confirmed COVID-19 from 2 hospitals in Wuhan, 1 hospital in Huangshi (Hubei province, 83 km from Wuhan) and 1 hospital in Chongqing (754 km from Wuhan). Demographic data, symptoms, laboratory values, comorbidities, treatments, and clinical outcomes were all collected, including data regarding to kidney functions. Data were compared among three groups: non-severe COVID-19 patients (128), severe COVID-19 patients (65) and a control group of other pneumonia (28). For the data from computed tomographic (CT) scans, we also included a control group of healthy subjects (110 cases, without abnormalities in the lung and without kidney diseases). The primary outcome was a common presence of kidney dysfunctions in COVID-19 patients and the occurrence of acute kidney injury (AKI) in a fraction of COVID-19 patients. Secondary outcomes included a survival analysis of COVID-19 patients in conditions of AKI or comorbid chronic illnesses. Findings: We included 193 COVID-19 patients (128 non-severe, 65 severe (including 32 non-survivors), between January 6th and February 21th,2020; the final date of follow-up was March 4th, 2020) and 28 patients of other pneumonia (15 of viral pneumonia, 13 of mycoplasma pneumonia) before the COVID-19 outbreak. On hospital admission, a remarkable fraction of patients had signs of kidney dysfunctions, including 59% with proteinuria, 44% with hematuria, 14% with increased levels of blood urea nitrogen, and 10% with increased levels of serum creatinine, although mild but worse than that in cases with other pneumonia. While these kidney dysfunctions might not be readily diagnosed as AKI at admission, over the progress during hospitalization they could be gradually worsened and diagnosed as AKI. A univariate Cox regression analysis showed that proteinuria, hematuria, and elevated levels of blood urea nitrogen, serum creatinine, uric acid as well as D-dimer were significantly associated with the death of COVID-19 patients respectively. Importantly, the Cox regression analysis also suggested that COVID-19 patients that developed AKI had a ~5.3-times mortality risk of those without AKI, much higher than that of comorbid chronic illnesses (~1.5 times risk of those without comorbid chronic illnesses). Interpretation: To prevent fatality in such conditions, we suggested a high degree of caution in monitoring the kidney functions of severe COVID-19 patients regardless of the past disease history. In addition, upon day-by-day monitoring, clinicians should consider any potential interventions to protect kidney functions at the early stage of the disease and renal replacement therapies in severely ill patients, particularly for those with strong inflammatory reactions or a cytokine storm. Funding: None.

Hepatocellular carcinoma (HCC) is a highly aggressive liver tumor containing cancer stem cells (CSCs), which participate in tumor invasion, therapeutic resistance, and tumor relapse leading to poor outcome and limited therapeutic options. Histone deacetylatase sirtuin 1 (SIRT1) has been shown to be up-regulated in human cancers; however, its role in liver CSCs is unknown. In this study, we explored the biological functions of SIRT1 in liver CSCs. Our data show that SIRT1 is highly expressed in liver CSCs and decreases during differentiation. In addition, high levels of SIRT1 predict a decreased probability of survival in patients with HCC. SIRT1 is responsible for the maintenance of self-renewal and tumorigenicity of liver CSCs, and overexpression of exogenous SIRT1 can restore self-renewal of non-CSCs. We demonstrated that SOX2 is a main downstream regulator of SIRT1-mediated self-renewal and tumorigenicity potential of liver CSCs. Mechanistically, SIRT1 regulates transcription of the SOX2 gene by way of chromatin-based epigenetic changes, which are dependent on DNA methylation. This effect is achieved by alternation of histone modification and interaction with DNA methyltransferase 3A, resulting in hypermethylation of SOX2 promoter. Furthermore, we demonstrated that insulin growth factor signaling plays an important role in maintaining SIRT1 expression through increased SIRT1 protein stability. Conclusions: These findings highlight the importance of SIRT1 in the biology of liver CSCs and suggest that SIRT1 may serve as a molecular target for HCC therapy. (HEPATOLOGY 2016;64:814-827)