GPAT1 Deficiency in Mice Modulates NASH Progression in a Model-Dependent Manner.

BACKGROUND & AIMS: Nonalcoholic fatty liver disease (NAFLD), and its more severe form, nonalcoholic steatohepatitis (NASH), is the leading cause for liver failure and liver cancer. Although the etiology is likely multifactorial, genes involved in regulating lipid metabolism are enriched in human NAFLD genome-wide association studies (GWAS), pointing to dysregulated lipid metabolism as a major pathogenic factor. Glycerol-3-phosphate acyltransferase 1 (GPAT1), encoded by GPAM, converts acyl-CoAs and glycerol-3-phosphate into lysophosphatidic acid and has been shown to regulate lipid accumulation in the liver. However, its role in mediating the progression from NAFLD to NASH has not been explored. METHODS: GPAT1-deficient mice were generated and challenged with diets inducing hepatic steatosis and NASH. Effects of GPAT1 deficiency on lipid and systemic metabolic end points were evaluated. RESULTS: Ablating GPAT1 globally or specifically in mouse hepatocytes reduced hepatic steatosis in the context of diet-induced or genetic obesity. Interestingly, blunting of progression from NAFLD to NASH in global GPAT1 knockout (KO) mice was model dependent. GPAT1 KO mice were protected from choline deficient, amino acid defined high-fat diet-induced NASH development, but not from the high fat, high carbohydrate, and high cholesterol diet-induced NASH. CONCLUSIONS: Our preclinical data support the notion that lipid metabolism pathways regulated by GPAT1 in hepatocytes play an essential role in NASH progression, albeit in a model-dependent manner.

Inhibition of myeloid-derived suppressive cell function with all-trans retinoic acid enhanced anti-PD-L1 efficacy in cervical cancer.

PD-1/PD-L1 inhibitor treatments are relatively inefficacious in advanced cervical cancer patients. The presence of myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment may be one significant barrier to efficacy. It has been shown that all-trans retinoic acid (ATRA) can differentiate MDSCs into mature myeloid cells. However, whether ATRA suppression of MDSCs function could enhance PD-L1 blockade-mediated tumor immunotherapy remains unknown. Here, the frequency of tumor-infiltrating MDSCs in cervical cancer patients was measured. ATRA was used to target MDSCs both in vitro and in tumor-bearing mice. The impact of ATRA on the human cell line HeLa was also investigated. The frequency of MDSCs and T cells was determined by flow cytometry. The expression of immunosuppressive genes was measured with quantitative real time-PCR and infiltration of immune cells was assessed by immunohistochemical examination. We found that tumor-infiltrating PD-L1+ MDSCs were more prevalent in cervical cancer patients. Blockade of PD-L1 expression in MDSCs with anti-PD-L1 antibody cannot relieve the suppressive activity of MDSCs induced by HeLa cells, while ATRA efficiently abrogated the suppressive activity of MDSCs. Furthermore, ATRA had no effect on PD-L1 expression in HeLa cells in vitro. In in vivo treatment, ATRA decreased MDSCs accumulation and increased the frequency of CD8+ T cells in BALB/C mice with U14 cervical tumors. Importantly, a combination treatment of ATRA and anti-PD-L1 antibody further delayed U14 tumor growth and increased the proportion of CD62L-CD8+ T cells, CD62L-CD4+ T cells, CD107a+CD8+ T cells as well as IFN-γ and TNF-α levels in tumors. Our results provide a rationale for the use of ATRA to suppress MDSCs and enhance anti-PD-L1 cancer immunotherapy in cervical cancer.

miR-20a inhibits hypoxia-induced autophagy by targeting ATG5/FIP200 in colorectal cancer.

Autophagy is a highly conserved lysosome-mediated protective cellular process in which cytosolic components, including damaged organelles and long-lived proteins, are cleared. Many studies have shown that autophagy was upregulated in hypoxic regions. However, the precise molecular mechanism of hypoxia-induced autophagy in colorectal cancer (CRC) is still elusive. In this study, we found that miR-20a was significantly downregulated under hypoxia in colon cancer cells, and overexpression of miR-20a alleviated hypoxia-induced autophagy. Moreover, miR-20a inhibits the hypoxia-induced autophagic flux by targeting multiple key regulators of autophagy, including ATG5 and FIP200. Furthermore, by dual-luciferase assay we demonstrated that miR-20a directly targeted the 3'-untranslated region of ATG5 and FIP200, regulating their messenger RNA and protein levels. In addition, reintroduction of exogenous ATG5 or FIP200 partially reversed miR-20a-mediated autophagy inhibition under hypoxia. A negative correlation between miR-20a and its target genes is observed in the hypoxic region of colon cancer tissues. Taken together, our findings suggest that hypoxia-mediated autophagy was regulated by miR-20a/ATG5/FI200 signaling pathway in CRC. miR-20a-mediated autophagy defect that might play an important role in hypoxia-induced autophagy during colorectal tumorigenesis.

[Changes of Leukemia Stem Cells in Acute Myeloid Leukemia before and after Treatment].

OBJECTIVE: To investigate the presence of leukemia stem cells (LSC) in acute myeloid leukemia (AML) and find out the relative position of leukemia cells in the figures of flow cytometry, and to analyze the relationship between minimal residual diseases (MRD) and the level of LSC, so as to explore the correlation of LSC changes with the curative effect and the prognosis during chemical therapy. METHODS: A total of 85 samples were collected from 50 AML (except M3) patients, including 50 samples from the newly diagnosed patients, 7 samples of AML patients with non-remission and 28 samples of AML patients with complete remission. All samples were used for detection of LSC from immune phenotype of CD34+/CD38-/CD123+ by flow cytometry. The detection of immune phenotypic of leukemia cells was performed in the newly diagnosed patients. The detection of leukemia- associated immune phenotypes (LAIP) was implemented in the non-newly diagnosed patients. RESULTS: The LSC was identified in the CD34+/ CD38-/ CD123+ in AML and consistent with the relative position of the leukemia cell in flow cytometry figures. Statistical analysis showed significant difference in LSC content between the newly diagnosed AML group and the post-chemotherapy complete remission group(P<0.01),but did not between the newly diagnosed AML group and the post-chemotherapy non-remission group(P>0.05).There was significant positive correlation between the LSC content and MRD level in 28 AML patients with complete remission (r=0.680,P<0.01). CONCLUSION: LSC exist in AML and the relative position are consistent with the leukemia cells in flow cytometry figures, the size characteristics and weak expression of CD45 are also similar to leukemia cells. The proportion of LSC decreases after chemotherapy. Detecting and tracking the LSC changes in bone marrow and combination with detecting minimal resident disease(MRD) may contribute to evaluate the theraputic efficacy and prognosis of leukemia patients.

Cidea promotes hepatic steatosis by sensing dietary fatty acids.

UNLABELLED: High levels of dietary saturated fat have been closely associated with the development of hepatic steatosis, but the factors that mediate this process remain elusive. Here, we observed that the level of cell death-inducing DNA fragmentation factor-alpha-like effector a (Cidea) expression was highly correlated with the severity of hepatic steatosis in humans. Overexpression of Cidea in mouse liver resulted in increased hepatic lipid accumulation and the formation of large lipid droplets (LDs). In contrast, mice with a Cidea deficiency had decreased lipid accumulation and alleviated hepatic steatosis when they received a high-fat-diet feeding or in ob/ob mice. Furthermore, the knockdown of Cidea in livers of ob/ob mice resulted in significantly reduced hepatic lipid accumulation and smaller LDs. Importantly, we observed that Cidea expression in hepatocytes was specifically induced by saturated fatty acids (FAs), and such induction was reduced when sterol response element-binding protein (SREBP)1c was knocked down. In contrast, the overexpression of SREBP1c restored the saturated FA-induced expression of Cidea. In addition, we observed that the stability of Cidea protein in hepatocytes increased significantly in response to treatment with FAs. CONCLUSION: Cidea plays critical roles in promoting hepatic lipid accumulation and in the development of hepatic steatosis by acting as a sensor that responds to diets that contain FAs.