Long Noncoding RNA p53-Stabilizing and Activating RNA Promotes p53 Signaling by Inhibiting Heterogeneous Nuclear Ribonucleoprotein K deSUMOylation and Suppresses Hepatocellular Carcinoma.

To identify hepatocellular carcinoma (HCC)-implicated long noncoding RNAs (lncRNAs), we performed an integrative omics analysis by integrating mRNA and lncRNA expression profiles in HCC tissues. We identified a collection of candidate HCC-implicated lncRNAs. Among them, we demonstrated that an lncRNA, which is named as p53-stabilizing and activating RNA (PSTAR), inhibits HCC cell proliferation and tumorigenicity through inducing p53-mediated cell cycle arrest. We further revealed that PSTAR can bind to heterogeneous nuclear ribonucleoprotein K (hnRNP K) and enhance its SUMOylation and thereby strengthen the interaction between hnRNP K and p53, which ultimately leads to the accumulation and transactivation of p53. PSTAR is down-regulated in HCC tissues, and the low PSTAR expression predicts poor prognosis in patients with HCC, especially those with wild-type p53. Conclusion: This study sheds light on the tumor suppressor role of lncRNA PSTAR, a modulator of the p53 pathway, in HCC.

Germline Duplication of SNORA18L5 Increases Risk for HBV-related Hepatocellular Carcinoma by Altering Localization of Ribosomal Proteins and Decreasing Levels of p53.

BACKGROUND & AIMS: Single nucleotide polymorphisms could affect risk for hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). We performed a germline copy number variation (CNV)-based genome-wide association study (GWAS) in populations of Chinese ancestry to search for germline CNVs that increase risk of HCC. METHODS: We conducted a CNV-based GWAS of 1583 HCC cases (persons with chronic HBV infection and HCC) and 1540 controls (persons with chronic HBV infection without HCC) in Chinese populations. Identified candidates were expressed in L-02, HepG2, or TP53-/- or wild-type HCT116 cells, and knocked down with short hairpin RNAs in HepG2, Bel-7402, and SMMC-7721 cells; proliferation, colony formation, and apoptosis were measured. Formation of xenograft tumors from cell lines was monitored in nude mice. Subcellular localization of ribosome proteins and levels or activity of p53 were investigated by co-immunoprecipitation, immunofluorescence, and immunoblot analyses. Levels of small nucleolar RNA H/ACA box 18-like 5 (SNORA18L5) were quantified by quantitative reverse transcription polymerase chain reaction. RESULTS: We identified a low-frequency duplication at chromosome 15q13.3 strongly associated with risk of HBV-related HCC (overall P = 3.17 × 10-8; odds ratio, 12.02). Copy numbers of the 15q13.3 duplication correlated with the expression of SNORA18L5 in liver tissues. Overexpression of SNORA18L5 increased HCC cell proliferation and growth of xenograft tumors in mice; knockdown reduced HCC proliferation and tumor growth. SNORA18L5 overexpression in HepG2 and SMMC-7721 cells inhibited p53-dependent cell cycle arrest and apoptosis. Overexpression of SNORA18L5 led to hyperactive ribosome biogenesis, increasing levels of mature 18S and 28S ribosomal RNAs and causing the ribosomal proteins RPL5 and RPL11 to stay in the nucleolus, which kept them from binding to MDM2. This resulted in increased MDM2-mediated ubiquitination and degradation of p53. Levels of SNORA18L5 were increased in HCC tissues compared with nontumor liver tissues and associated with shorter survival times of patients. CONCLUSIONS: In a CNV-based GWAS, we associated duplication at 15q13.3 with increased risk of HBV-related HCC. We found SNORA18L5 at this location to promote HCC cell proliferation and tumor growth in mice. SNORA18L5 increases ribosome biogenesis, facilitates ribosomal RNA maturation, and alters localization of RPL5 and RPL11, allowing for increased MDM2-mediated proteolysis of p53 and cell cycle arrest.

A single-cell atlas of the multicellular ecosystem of primary and metastatic hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) represents a paradigm of the relation between tumor microenvironment (TME) and tumor development. Here, we generate a single-cell atlas of the multicellular ecosystem of HCC from four tissue sites. We show the enrichment of central memory T cells (TCM) in the early tertiary lymphoid structures (E-TLSs) in HCC and assess the relationships between chronic HBV/HCV infection and T cell infiltration and exhaustion. We find the MMP9+ macrophages to be terminally differentiated tumor-associated macrophages (TAMs) and PPARγ to be the pivotal transcription factor driving their differentiation. We also characterize the heterogeneous subpopulations of malignant hepatocytes and their multifaceted functions in shaping the immune microenvironment of HCC. Finally, we identify seven microenvironment-based subtypes that can predict prognosis of HCC patients. Collectively, this large-scale atlas deepens our understanding of the HCC microenvironment, which might facilitate the development of new immune therapy strategies for this malignancy.

The A-to-I editing of KPC1 promotes intrahepatic cholangiocarcinoma by attenuating proteasomal processing of NF-κB1 p105 to p50.

BACKGROUND: Aberrant RNA editing of adenosine-to-inosine (A-to-I) has been linked to multiple human cancers, but its role in intrahepatic cholangiocarcinoma (iCCA) remains unknown. We conducted an exome-wide investigation to search for dysregulated RNA editing that drive iCCA pathogenesis. METHODS: An integrative whole-exome and transcriptome sequencing analysis was performed to elucidate the RNA editing landscape in iCCAs. Putative RNA editing sites were validated by Sanger sequencing. In vitro and in vivo experiments were used to assess the effects of an exemplary target gene Kip1 ubiquitination-promoting complex 1 (KPC1) and its editing on iCCA cells growth and metastasis. Crosstalk between KPC1 RNA editing and NF-κB signaling was analyzed by molecular methods. RESULTS: Through integrative omics analyses, we revealed an adenosine deaminases acting on RNA 1A (ADAR1)-mediated over-editing pattern in iCCAs. ADAR1 is frequently amplified and overexpressed in iCCAs and plays oncogenic roles. Notably, we identified a novel ADAR1-mediated A-to-I editing of KPC1 transcript, which results in substitution of methionine with valine at residue 8 (p.M8V). KPC1 p.M8V editing confers loss-of-function phenotypes through blunting the tumor-suppressive role of wild-type KPC1. Mechanistically, KPC1 p.M8V weakens the affinity of KPC1 to its substrate NF-κB1 p105, thereby reducing the ubiquitinating and proteasomal processing of p105 to p50, which in turn enhances the activity of oncogenic NF-κB signaling. CONCLUSIONS: Our findings established that amplification-driven ADAR1 overexpression results in overediting of KPC1 p.M8V in iCCAs, leading to progression via activation of the NF-κB signaling pathway, and suggested ADAR1-KPC1-NF-κB axis as a potential therapeutic target for iCCA.

Genome-wide association study identifies 8p21.3 associated with persistent hepatitis B virus infection among Chinese.

Hepatitis B virus (HBV) infection is a common infectious disease. Here we perform a genome-wide association study (GWAS) among Chinese populations to identify novel genetic loci involved in persistent HBV infection. GWAS scan is performed in 1,251 persistently HBV infected subjects (PIs, cases) and 1,057 spontaneously recovered subjects (SRs, controls), followed by replications in four independent populations totally consisting of 3,905 PIs and 3,356 SRs. We identify a novel locus at 8p21.3 (index rs7000921, odds ratio=0.78, P=3.2 × 10(-12)). Furthermore, we identify significant expression quantitative trait locus associations for INTS10 gene at 8p21.3. We demonstrate that INST10 suppresses HBV replication via IRF3 in liver cells. In clinical plasma samples, we confirm that INST10 levels are significantly decreased in PIs compared with SRs, and negatively correlated with the HBV load. These findings highlight a novel antiviral gene INTS10 at 8p21.3 in the clearance of HBV infection.