Peptostreptococcus stomatis promotes colonic tumorigenesis and receptor tyrosine kinase inhibitor resistance by activating ERBB2-MAPK.

Peptostreptococcus stomatis (P. stomatis) is enriched in colorectal cancer (CRC), but its causality and translational implications in CRC are unknown. Here, we show that P. stomatis accelerates colonic tumorigenesis in ApcMin/+ and azoxymethane/dextran sodium sulfate (AOM-DSS) models by inducing cell proliferation, suppressing apoptosis, and impairing gut barrier function. P. stomatis adheres to CRC cells through its surface protein fructose-1,6-bisphosphate aldolase (FBA) that binds to the integrin α6/ß4 receptor on CRC cells, leading to the activation of ERBB2 and the downstream MEK-ERK-p90 cascade. Blockade of the FBA-integrin α6/ß4 abolishes ERBB2-mitogen-activated protein kinase (MAPK) activation and the protumorigenic effect of P. stomatis. P. stomatis-driven ERBB2 activation bypasses receptor tyrosine kinase (RTK) blockade by EGFR inhibitors (cetuximab, erlotinib), leading to drug resistance in xenograft and spontaneous CRC models of KRAS-wild-type CRC. P. stomatis also abrogates BRAF inhibitor (vemurafenib) efficacy in BRAFV600E-mutant CRC xenografts. Thus, we identify P. stomatis as an oncogenic bacterium and a contributory factor for non-responsiveness to RTK inhibitors in CRC.

Lactobacillus acidophilus suppresses non-alcoholic fatty liver disease-associated hepatocellular carcinoma through producing valeric acid.

BACKGROUND: Gut probiotic depletion is associated with non-alcoholic fatty liver disease-associated hepatocellular carcinoma (NAFLD-HCC). Here, we investigated the prophylactic potential of Lactobacillus acidophilus against NAFLD-HCC. METHODS: NAFLD-HCC conventional and germ-free mice were established by diethylnitrosamine (DEN) injection with feeding of high-fat high-cholesterol (HFHC) or choline-deficient high-fat (CDHF) diet. Orthotopic NAFLD-HCC allografts were established by intrahepatic injection of murine HCC cells with HFHC feeding. Metabolomic profiling was performed using liquid chromatography-mass spectrometry. Biological functions of L. acidophilus conditional medium (L.a CM) and metabolites were determined in NAFLD-HCC human cells and mouse organoids. FINDINGS: L. acidophilus supplementation suppressed NAFLD-HCC formation in HFHC-fed DEN-treated mice. This was confirmed in orthotopic allografts and germ-free tumourigenesis mice. L.a CM inhibited the growth of NAFLD-HCC human cells and mouse organoids. The protective function of L. acidophilus was attributed to its non-protein small molecules. By metabolomic profiling, valeric acid was the top enriched metabolite in L.a CM and its upregulation was verified in liver and portal vein of L. acidophilus-treated mice. The protective function of valeric acid was demonstrated in NAFLD-HCC human cells and mouse organoids. Valeric acid significantly suppressed NAFLD-HCC formation in HFHC-fed DEN-treated mice, accompanied by improved intestinal barrier integrity. This was confirmed in another NAFLD-HCC mouse model induced by CDHF diet and DEN. Mechanistically, valeric acid bound to hepatocytic surface receptor GPR41/43 to inhibit Rho-GTPase pathway, thereby ablating NAFLD-HCC. INTERPRETATION: L. acidophilus exhibits anti-tumourigenic effect in mice by secreting valeric acid. Probiotic supplementation is a potential prophylactic of NAFLD-HCC. FUNDING: Shown in Acknowledgments.

High Soluble Fiber Promotes Colorectal Tumorigenesis Through Modulating Gut Microbiota and Metabolites in Mice.

BACKGROUND & AIMS: Dietary fibers are mainly fermented by the gut microbiota, but their roles in colorectal cancer (CRC) are largely unclear. Here, we investigated the associations of different fibers with colorectal tumorigenesis in mice. METHODS: Apcmin/+ mice and C57BL/6 mice with azoxymethane (AOM) injection were used as CRC mouse models. Mice were fed with mixed high-fiber diet (20% soluble fiber and 20% insoluble fiber), high-inulin diet, high-guar gum diet, high-cellulose diet, or diets with different inulin dose. Germ-free mice were used for validation. Fecal microbiota and metabolites were profiled by shotgun metagenomic sequencing and liquid chromatography-mass spectrometry, respectively. RESULTS: Mixed high-fiber diet promoted colorectal tumorigenesis with increased tumor number and tumor load in AOM-treated and Apcmin/+ mice. Antibiotics use abolished the pro-tumorigenic effect of mixed high-fiber diet, while transplanting stools from mice fed with mixed high-fiber diet accelerated tumor growth in AOM-treated germ-free mice. We therefore characterized the contribution of soluble and insoluble fiber in CRC separately. Our results revealed that soluble fiber inulin or guar gum, but not insoluble fiber cellulose, promoted colorectal tumorigenesis in AOM-treated and Apcmin/+ mice. Soluble fiber induced gut dysbiosis with Bacteroides uniformis enrichment and Bifidobacterium pseudolongum depletion, accompanied by increased fecal butyrate and serum bile acids and decreased inosine. We also identified a positive correlation between inulin dosage and colorectal tumorigenesis. Moreover, transplanting stools from mice fed with high-inulin diet increased colonic cell proliferation and oncogene expressions in germ-free mice. CONCLUSION: High-dose soluble but not insoluble fiber potentiates colorectal tumorigenesis in a dose-dependent manner by dysregulating gut microbiota and metabolites in mice.

Parabacteroides distasonis uses dietary inulin to suppress NASH via its metabolite pentadecanoic acid.

Non-alcoholic steatohepatitis (NASH) is the severe form of non-alcoholic fatty liver disease, and is characterized by liver inflammation and fat accumulation. Dietary interventions, such as fibre, have been shown to alleviate this metabolic disorder in mice via the gut microbiota. Here, we investigated the mechanistic role of the gut microbiota in ameliorating NASH via dietary fibre in mice. Soluble fibre inulin was found to be more effective than insoluble fibre cellulose to suppress NASH progression in mice, as shown by reduced hepatic steatosis, necro-inflammation, ballooning and fibrosis. We employed stable isotope probing to trace the incorporation of 13C-inulin into gut bacterial genomes and metabolites during NASH progression. Shotgun metagenome sequencing revealed that the commensal Parabacteroides distasonis was enriched by 13C-inulin. Integration of 13C-inulin metagenomes and metabolomes suggested that P. distasonis used inulin to produce pentadecanoic acid, an odd-chain fatty acid, which was confirmed in vitro and in germ-free mice. P. distasonis or pentadecanoic acid was protective against NASH in mice. Mechanistically, inulin, P. distasonis or pentadecanoic acid restored gut barrier function in NASH models, which reduced serum lipopolysaccharide and liver pro-inflammatory cytokine expression. Overall this shows that gut microbiota members can use dietary fibre to generate beneficial metabolites to suppress metabolic disease.

Altered gut microbiome composition by appendectomy contributes to colorectal cancer.

Appendectomy impacts the homeostasis of gut microbiome in patients. We aimed to study the role of appendectomy in colorectal cancer (CRC) risk through causing gut microbial dysbiosis. Population-based longitudinal study (cohort 1, n = 129,155) showed a 73.0% increase in CRC risk among appendectomy cases throughout 20 years follow-up (Adjusted sub-distribution hazard ratio (SHR) 1.73, 95% CI 1.49-2.01, P < 0.001). Shotgun metagenomic sequencing was performed on fecal samples from cohort 2 (n = 314). Gut microbial dysbiosis in appendectomy subjects was observed with significant enrichment of 7 CRC-promoting bacteria (Bacteroides vulgatus, Bacteroides fragilis, Veillonella dispar, Prevotella ruminicola, Prevotella fucsa, Prevotella dentalis, Prevotella denticola) and depletion of 5 beneficial commensals (Blautia sp YL58, Enterococcus hirae, Lachnospiraceae bacterium Choco86, Collinsella aerofaciens, Blautia sp SC05B48). Microbial network analysis showed increased correlation strengths among enriched bacteria and their enriched oncogenic pathways in appendectomy subjects compared to controls. Of which, B. fragilis was the centrality in the network of the enriched bacteria. We further confirmed that appendectomy promoted colorectal tumorigenesis in mice by causing gut microbial dysbiosis and impaired intestinal barrier function. Collectively, this study revealed appendectomy-induced microbial dysbiosis characterized by enriched CRC-promoting bacteria and depleted beneficial commensals, signifying that the gut microbiome may play a crucial role in CRC development induced by appendectomy.

High Sensitivity of Shotgun Metagenomic Sequencing in Colon Tissue Biopsy by Host DNA Depletion.

The high host genetic background of tissue biopsies hinders the application of shotgun metagenomic sequencing in characterizing the tissue microbiota. We proposed an optimized method that removed host DNA from colon biopsies and examined the effect on metagenomic analysis. Human or mouse colon biopsies were divided into two groups, with one group undergoing host DNA depletion and the other serving as the control. Host DNAs were removed through differential lysis of mammalian and bacterial cells before sequencing. The impact of host DNA depletion on microbiota was compared based on phylogenetic diversity analyses and regression analyses. Removing host DNA enhanced bacterial sequencing depth and improved species discovery, increasing bacterial reads by 2.46 ± 0.20 fold while reducing host reads by 6.80% ± 1.06%. Moreover, 3.40 times more of bacterial species were detected after host DNA depletion. This was confirmed from mouse colon tissues, increasing bacterial reads by 5.46 ± 0.42 fold while decreasing host reads by 10.2% ± 0.83%. Similarly, significantly more species were detected in the mouse colon tissue upon host DNA depletion (P < 0.001). Furthermore, an increased microbial richness was evident in the host DNA-depleted samples compared with non-depleted controls in human colon biopsies and mouse colon tissues (P < 0.001). Our optimized method of host DNA depletion improved the sensitivity of shotgun metagenomic sequencing in bacterial detection in the biopsy, which may yield a more accurate taxonomic profile of the tissue microbiota and identify bacteria that are important for disease initiation or progression.

Lactobacillus gallinarum modulates the gut microbiota and produces anti-cancer metabolites to protect against colorectal tumourigenesis.

OBJECTIVE: Using faecal shotgun metagenomic sequencing, we identified the depletion of Lactobacillus gallinarum in patients with colorectal cancer (CRC). We aimed to determine the potential antitumourigenic role of L. gallinarum in colorectal tumourigenesis. DESIGN: The tumor-suppressive effect of L. gallinarum was assessed in murine models of CRC. CRC cell lines and organoids derived from patients with CRC were cultured with L. gallinarum or Escherichia coli MG1655 culture-supernatant to evaluate cell proliferation, apoptosis and cell cycle distribution. Gut microbiota was assessed by 16S ribosomal DNA sequencing. Antitumour molecule produced from L. gallinarum was identified by liquid chromatography mass spectrometry (LC-MS/MS) and targeted mass spectrometry. RESULTS: L. gallinarum significantly reduced intestinal tumour number and size compared with E. coli MG1655 and phosphate-buffered saline in both male and female murine intestinal tumourigenesis models. Faecal microbial profiling revealed enrichment of probiotics and depletion of pathogenic bacteria in L. gallinarum-treated mice. Culturing CRC cells with L. gallinarum culture-supernatant (5%, 10% and 20%) concentration-dependently suppressed cell proliferation and colony formation. L. gallinarum culture-supernatant significantly promoted apoptosis in CRC cells and patient-derived CRC organoids, but not in normal colon epithelial cells. Only L. gallinarum culture-supernatant with fraction size <3 kDa suppressed proliferation in CRC cells. Using LC-MS/MS, enrichments of indole-3-lactic acid (ILA) was identified in both L. gallinarum culture-supernatant and the gut of L. gallinarum-treated mice. ILA displayed anti-CRC growth in vitro and inhibited intestinal tumourigenesis in vivo. CONCLUSION: L. gallinarum protects against intestinal tumourigenesis by producing protective metabolites that can promote apoptosis of CRC cells.

O-GlcNAcylation inhibits hepatic stellate cell activation.

BACKGROUND AND AIM: Protein O-GlcNAcylation is a critical post-translational modification regulating gene expression and fundamental cell functions. O-GlcNAc transferase (OGT) emerged as a key regulator of liver pathophysiology and disease. In this study, we aimed to evaluate the role of OGT in hepatic stellate cells (HSCs) and its consequent role in liver fibrosis. METHODS: Primary HSCs were isolated from C57/B6 mice. Cell morphology and α-SMA immunofluorescence staining were observed under scanning confocal microscope. Transcriptomic profile was evaluated by RNAseq (Illumina). Promoter activity was examined by luciferase and ß--Galactosidase reporter assays. Liver fibrosis mouse models were induced either by intraperitoneal injection of CCl4 at 3 times/week for 4 weeks or by feeding with methionine and choline deficient (MCD) diet for 4 weeks. RESULTS: OGT protein expression and protein O-GlcNAcylation were significantly decreased in CCl4 - or MCD diet-induced liver fibrosis as compared with normal liver in mice. OGT expression and protein O-GlcNAcylation were also decreased in primary HSCs isolated from liver with CCl4 -induced fibrosis compared with those from normal liver. RNA-seq showed that OGT knockdown in HSCs modulated key signaling pathways involved in HSC activation. Promoter sequence analysis of the differentially expressed genes predicted serum response factor (SRF) as a key transcription factor regulated by OGT. Luciferase reporter assay confirmed that OGT repressed activity of SRF to induce α-SMA transcription. Mutations of specific O-GlcNAcylation sites on SRF increased its transcriptional activity, validating negative regulation of SRF by OGT-mediated O-GlcNAcylation. CONCLUSIONS: Our results suggest that OGT functions as a negative regulator of HSC activation by promoting SRF O-GlcNAcylation to protect against liver fibrosis.

Fecal microbial DNA markers serve for screening colorectal neoplasm in asymptomatic subjects.

BACKGROUND AND AIM: We have previously shown that fecal microbial markers might be useful for non-invasive diagnosis of colorectal cancer (CRC) and adenoma. Here, we assessed the application of microbial DNA markers, as compared with and in combination with fecal immunochemical test (FIT), in detecting CRC and adenoma in symptomatic patients and asymptomatic subjects. METHODS: We recruited 676 subjects [210 CRC, 115 advanced adenoma (AA), 86 non-advanced adenoma, and 265 non-neoplastic controls], including 241 symptomatic and 435 asymptomatic subjects. Fecal abundances of Fusobacterium nucleatum, a Lachnoclostridium sp. m3, Bacteroides clarus, and Clostridium hathewayi were quantified by quantitative PCR. Combining score of the four microbial markers (4Bac) and diagnostic prediction were determined using our previously established scoring model and cutoff values and FIT with a cutoff of 100 ng Hb/mL. RESULTS: 4Bac detected similar percentages of CRC [85.3% (95%CI: 79.2-90.2%) vs 84.9% (68.1-94.9%)] and AA [35.7% (12.8-64.9%) vs 38.6% (29.1-48.8%)], while FIT detected more CRC [72.1% (63.7-79.4%) vs 66.7% (48.2-82.0%)] and AA [28.6% (8.4-58.1%) vs 16.8% (10.1-25.6%)], in symptomatic vs asymptomatic subjects, respectively. Focusing on the asymptomatic cohort, 4Bac was more sensitive for diagnosing CRC and AA than FIT (P < 0.001), with lower specificity [83.3% (77.6-88.0%) vs 98.6% (96.0-99.7%)]. FIT failed to detect any non-advanced adenoma [0% (0.0-4.2%)] compared with 4Bac [41.9% (31.3-53.0%), P < 0.0001]. Combining 4Bac with FIT improved sensitivities for CRC [90.9% (75.7-98.1%)] and AA [48.5% (38.4-58.7%)] detection. CONCLUSION: Quantitation of fecal microbial DNA markers may serve as a new test, stand alone, or in combination with FIT for screening colorectal neoplasm in asymptomatic subjects.

Dietary cholesterol drives fatty liver-associated liver cancer by modulating gut microbiota and metabolites.

OBJECTIVE: Non-alcoholic fatty liver disease (NAFLD)-associated hepatocellular carcinoma (HCC) is an increasing healthcare burden worldwide. We examined the role of dietary cholesterol in driving NAFLD-HCC through modulating gut microbiota and its metabolites. DESIGN: High-fat/high-cholesterol (HFHC), high-fat/low-cholesterol or normal chow diet was fed to C57BL/6 male littermates for 14 months. Cholesterol-lowering drug atorvastatin was administered to HFHC-fed mice. Germ-free mice were transplanted with stools from mice fed different diets to determine the direct role of cholesterol modulated-microbiota in NAFLD-HCC. Gut microbiota was analysed by 16S rRNA sequencing and serum metabolites by liquid chromatography-mass spectrometry (LC-MS) metabolomic analysis. Faecal microbial compositions were examined in 59 hypercholesterolemia patients and 39 healthy controls. RESULTS: High dietary cholesterol led to the sequential progression of steatosis, steatohepatitis, fibrosis and eventually HCC in mice, concomitant with insulin resistance. Cholesterol-induced NAFLD-HCC formation was associated with gut microbiota dysbiosis. The microbiota composition clustered distinctly along stages of steatosis, steatohepatitis and HCC. Mucispirillum, Desulfovibrio, Anaerotruncus and Desulfovibrionaceae increased sequentially; while Bifidobacterium and Bacteroides were depleted in HFHC-fed mice, which was corroborated in human hypercholesteremia patients. Dietary cholesterol induced gut bacterial metabolites alteration including increased taurocholic acid and decreased 3-indolepropionic acid. Germ-free mice gavaged with stools from mice fed HFHC manifested hepatic lipid accumulation, inflammation and cell proliferation. Moreover, atorvastatin restored cholesterol-induced gut microbiota dysbiosis and completely prevented NAFLD-HCC development. CONCLUSIONS: Dietary cholesterol drives NAFLD-HCC formation by inducing alteration of gut microbiota and metabolites in mice. Cholesterol inhibitory therapy and gut microbiota manipulation may be effective strategies for NAFLD-HCC prevention.

Gastric microbes associated with gastric inflammation, atrophy and intestinal metaplasia 1 year after Helicobacter pylori eradication.

OBJECTIVE: Helicobacter pylori is associated with gastric inflammation, precancerous gastric atrophy (GA) and intestinal metaplasia (IM). We aimed to identify microbes that are associated with progressive inflammation, GA and IM 1 year after H. pylori eradication. DESIGN: A total of 587 H. pylori-positive patients were randomised to receive H. pylori eradication therapy (295 patients) or placebo (292 patients). Bacterial taxonomy was analysed on 404 gastric biopsy samples comprising 102 pairs before and after 1 year H. pylori eradication and 100 pairs before and after 1 year placebo by 16S rRNA sequencing. RESULTS: Analysis of microbial sequences confirmed the eradication of H. pylori in treated group after 1 year. Principal component analysis revealed distinct microbial clusters reflected by increase in bacterial diversity (p<0.00001) after H. pylori eradication. While microbial interactions remained largely unchanged after placebo treatment, microbial co-occurrence was less in treated group. Acinetobacter lwoffii, Streptococcus anginosus and Ralstonia were enriched while Roseburia and Sphingomonas were depleted in patients with persistent inflammation 1 year after H. pylori eradication. A distinct cluster of oral bacteria comprising Peptostreptococcus, Streptococcus, Parvimonas, Prevotella, Rothia and Granulicatella were associated with emergence and persistence of GA and IM. Probiotic Faecalibacterium praustznii was depleted in subjects who developed GA following H. pylori eradication. Functional pathways including amino acid metabolism and inositol phosphate metabolism were enriched while folate biosynthesis and NOD-like receptor signalling decreased in atrophy/IM-associated gastric microbiota. CONCLUSION: This study identified that gastric microbes contribute to the progression of gastric carcinogenesis after H. pylori eradication.

A novel faecal Lachnoclostridium marker for the non-invasive diagnosis of colorectal adenoma and cancer.

OBJECTIVE: There is a need for early detection of colorectal cancer (CRC) at precancerous-stage adenoma. Here, we identified novel faecal bacterial markers for diagnosing adenoma. DESIGN: This study included 1012 subjects (274 CRC, 353 adenoma and 385 controls) from two independent Asian groups. Candidate markers were identified by metagenomics and validated by targeted quantitative PCR. RESULTS: Metagenomic analysis identified 'm3' from a Lachnoclostridium sp., Fusobacterium nucleatum (Fn) and Clostridium hathewayi (Ch) to be significantly enriched in adenoma. Faecal m3 and Fn were significantly increased from normal to adenoma to CRC (p<0.0001, linear trend by one-way ANOVA) in group I (n=698), which was further confirmed in group II (n=313; p<0.0001). Faecal m3 may perform better than Fn in distinguishing adenoma from controls (areas under the receiver operating characteristic curve (AUROCs) m3=0.675 vs Fn=0.620, p=0.09), while Fn performed better in diagnosing CRC (AUROCs Fn=0.862 vs m3=0.741, p<0.0001). At 78.5% specificity, m3 and Fn showed sensitivities of 48.3% and 33.8% for adenoma, and 62.1% and 77.8% for CRC, respectively. In a subgroup tested with faecal immunochemical test (FIT; n=642), m3 performed better than FIT in detecting adenoma (sensitivities for non-advanced and advanced adenomas of 44.2% and 50.8% by m3 (specificity=79.6%) vs 0% and 16.1% by FIT (specificity=98.5%)). Combining with FIT improved sensitivity of m3 for advanced adenoma to 56.8%. The combination of m3 with Fn, Ch, Bacteroides clarus and FIT performed best for diagnosing CRC (specificity=81.2% and sensitivity=93.8%). CONCLUSION: This study identifies a novel bacterial marker m3 for the non-invasive diagnosis of colorectal adenoma.

Peptostreptococcus anaerobius promotes colorectal carcinogenesis and modulates tumour immunity.

Emerging evidence implicates a role of the gut microbiota in colorectal cancer (CRC). Peptostreptococcus anaerobius (P. anaerobius) is an anaerobic bacterium selectively enriched in the faecal and mucosal microbiota from patients with CRC, but its causative role and molecular mechanism in promoting tumorigenesis remain unestablished. We demonstrate that P. anaerobius adheres to the CRC mucosa and accelerates CRC development in ApcMin/+ mice. In vitro assays and transmission electron microscopy revealed that P. anaerobius selectively adheres to CRC cell lines (HT-29 and Caco-2) compared to normal colonic epithelial cells (NCM460). We identified a P. anaerobius surface protein, putative cell wall binding repeat 2 (PCWBR2), which directly interacts with colonic cell lines via α2/ß1 integrin, a receptor frequently overexpressed in human CRC tumours and cell lines. Interaction between PCWBR2 and integrin α2/ß1 induces the activation of the PI3K-Akt pathway in CRC cells via phospho-focal adhesion kinase, leading to increased cell proliferation and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation. NF-κB in turn triggers a pro-inflammatory response as indicated by increased levels of cytokines, such as interleukin-10 and interferon-γ in the tumours of P. anaerobius-treated ApcMin/+ mice. Analyses of tumour-infiltrating immune cell populations in P. anaerobius-treated ApcMin/+ mice revealed significant expansion of myeloid-derived suppressor cells, tumour-associated macrophages and granulocytic tumour-associated neutrophils, which are associated with chronic inflammation and tumour progression. Blockade of integrin α2/ß1 by RGDS peptide, small interfering RNA or antibodies all impair P. anaerobius attachment and abolish P. anaerobius-mediated oncogenic response in vitro and in vivo. Collectively, we show that P. anaerobius drives CRC via a PCWBR2-integrin α2/ß1-PI3K-Akt-NF-κB signalling axis and identify the PCWBR2-integrin α2/ß1 axis as a potential therapeutic target for CRC.

Bone marrow-derived macrophage contributes to fibrosing steatohepatitis through activating hepatic stellate cells.

The role of macrophages in fibrosing steatohepatitis is largely unclear. We characterized the origin and molecular mechanisms of macrophages and its targeted therapy of fibrosing steatohepatitis. Fibrosing steatohepatitis was established in Alms1 mutant (foz/foz) and C57BL/6J wildtype mice fed high-fat/high-cholesterol or methionine- and choline-deficient diet. Bone marrow transplantation was performed to track the macrophage origin in fibrosing steatohepatitis. Macrophages were depleted using liposomal clodronate. Primary macrophages were isolated from bone marrow for adoptive transfer into mice. We found that macrophage infiltration is induced in two mouse models of fibrosing steatohepatitis and human nonalcoholic steatohepatitis-fibrosis patients. Bone marrow-derived macrophages (BMMs) contribute to the hepatic macrophage accumulation in experimental fibrosing steatohepatitis. Depletion of hepatic BMMs by liposomal clodronate during liver injury attenuated fibrosing steatohepatitis, whilst BMMs depletion after liver injury delayed the regression of fibrosing steatohepatitis. The pro-fibrotic effect of macrophages was associated with reduced activation of hepatic stellate cells (HSCs), collagen deposition and hepatic expression of key pro-fibrotic factors (TIMP1, TIMP2, and TGFß1) and endoplasmic reticulum stress markers (GRP78, IRE1α, and PDI). Conversely, adoptive transfer of BMMs significantly aggravated fibrosing steatohepatitis. Moreover, macrophage-conditioned medium directly promoted the phenotypic transition of primary quiescent HSCs to activated HSCs; it enhanced activation and proliferation but decreased apoptosis of HSC cell lines (LX-2 and HSC-T6). The effect of BMMs in promoting fibrosing steatohepatitis was mediated by inducing key pro-fibrosis factors and signaling pathways including cytokine/chemokine, TGFß and complement cascade as assessed by cDNA expression array. Complement 3a receptor (C3ar1) was a predominant effector of macrophage mediated fibrosing steatohepatitis. Knockout of C3ar1 in mice blunted development of fibrosing steatohepatitis. In conclusion, BMMs promoted the progression of fibrosing steatohepatitis during injury, whereas macrophages reduced fibrosing steatohepatitis in the recovery phase of liver injury. Increasing anti-fibrotic macrophages and decreasing pro-fibrotic macrophages are promising approaches for fibrosing steatohepatitis. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Dietary cholesterol promotes steatohepatitis related hepatocellular carcinoma through dysregulated metabolism and calcium signaling.

The underlining mechanisms of dietary cholesterol and nonalcoholic steatohepatitis (NASH) in contributing to hepatocellular carcinoma (HCC) remain undefined. Here we demonstrated that high-fat-non-cholesterol-fed mice developed simple steatosis, whilst high-fat-high-cholesterol-fed mice developed NASH. Moreover, dietary cholesterol induced larger and more numerous NASH-HCCs than non-cholesterol-induced steatosis-HCCs in diethylnitrosamine-treated mice. NASH-HCCs displayed significantly more aberrant gene expression-enriched signaling pathways and more non-synonymous somatic mutations than steatosis-HCCs (335 ± 84/sample vs 43 ± 13/sample). Integrated genetic and expressional alterations in NASH-HCCs affected distinct genes pertinent to five pathways: calcium, insulin, cell adhesion, axon guidance and metabolism. Some of the novel aberrant gene expression, mutations and core oncogenic pathways identified in cholesterol-associated NASH-HCCs in mice were confirmed in human NASH-HCCs, which included metabolism-related genes (ALDH18A1, CAD, CHKA, POLD4, PSPH and SQLE) and recurrently mutated genes (RYR1, MTOR, SDK1, CACNA1H and RYR2). These findings add insights into the link of cholesterol to NASH and NASH-HCC and provide potential therapeutic targets.

Defective lysosomal clearance of autophagosomes and its clinical implications in nonalcoholic steatohepatitis.

Autophagic impairment is implicated in nonalcoholic fatty liver disease (NAFLD), but the molecular mechanism is unclear. We found that autophagic flux was significantly inhibited in 3 murine models of NAFLD. Interestingly, the number of acidic organelles and the level of mature cathepsin D were reduced, suggesting defective lysosome acidification. Asparagine synthetase (ASNS) was induced by endoplasmic reticulum stress, leading to the generation of asparagine, which inhibited lysosome acidification. Both steatotic- and asparagine-treated hepatocytes showed reduced lysosomal acidity and retention of lysosomal calcium. Knockdown of ASNS in steatotic hepatocytes restored autophagic flux. As a potential biomarker, increased serum p62/sequestosome 1 (SQSTM1) level was an independent risk factor for patients with steatosis and lobular inflammation. Impaired autophagy in NAFLD is elicited by defective lysosome acidification, which is caused by ASNS-induced asparagine synthesis under endoplasmic reticulum stress and subsequent retention of lysosomal calcium. p62/SQSTM1 could be used as a noninvasive biomarker in the diagnosis of NAFLD patients.-Wang, X., Zhang, X., Chu, E. S. H., Chen, X., Kang, W., Wu, F., To, K.-F., Wong, V. W. S., Chan, H. L. Y., Chan, M. T. V., Sung, J. J. Y., Wu, W. K. K., Yu, J. Defective lysosomal clearance of autophagosomes and its clinical implications in nonalcoholic steatohepatitis.

Pro-Inflammatory CXCR3 Impairs Mitochondrial Function in Experimental Non-Alcoholic Steatohepatitis.

Mitochondrial dysfunction plays a crucial role in the development of non-alcoholic steatohepatitis (NASH). However, the regulator of mitochondrial dysfunction in the pathogenesis of NASH is still largely unclear. CXCR3 is an essential pro-inflammatory factor in chronic liver diseases. We explored the significance of CXCR3 in regulating mitochondrial function during NASH development in animal models and cultured hepatocytes. METHODS: The effects of CXCR3 on mitochondrial function were evaluated by genetic knockout or pharmacological inhibition in mouse models and in vitro. The ultrastructural changes of mitochondria were assessed by transmission electron microscopy (TEM). Hepatic levels of mitochondrial reactive oxygen species (ROS), DNA damage, membrane potential and ATP were examined. RESULTS: CXCR3 ablation by genetic knockout or pharmacological inhibition in mice protected against NASH development by influencing mitochondrial function. Similarly, depletion of CXCR3 reduced steatohepatitis injury in cultured hepatocytes. TEM analysis revealed that liver mitochondrial integrity was much improved in CXCR3 knockout (CXCR3-/-) compared to wildtype (WT) mice. In agreement with this, impaired mitochondrial function was pronounced in WT mice compared to CXCR3-/- mice, evidenced by increased protein expression of dynamic-related protein-1 (DRP1) and fission-1 (FIS1) and decreased protein expression of mitofusin-1 (MFN1). Mitochondrial dysfunction was induced in AML-12 hepatocytes by methionine and choline deficient medium and in HepG2 cells by palmitic acid. The impaired mitochondrial function in both cell lines was evidenced by reduced membrane potential and ATP content, and by increased mitochondrial ROS accumulation and DNA damage. However, CXCR3 knockdown by siCXCR3 significantly diminished the mitochondrial dysfunction in both AML-12 and HepG2 hepatocytes. In addition, inhibition of CXCR3 by CXCR3 specific antagonists SCH546738 and AMG487 restored mitochondrial function and inhibited mitochondrial-dependent apoptosis in the liver of WT mice fed with methionine and choline deficient diet. CONCLUSION: CXCR3 induces mitochondrial dysfunction, which contributes to the pathogenesis of steatohepatitis. Pharmacologic blockade of CXCR3 prevents mitochondrial dysfunction and restores the severity of steatohepatitis, indicating a potential clinical impact for controlling the disease.

Sodium Channel Subunit SCNN1B Suppresses Gastric Cancer Growth and Metastasis via GRP78 Degradation.

There remains a paucity of functional biomarkers in gastric cancer. Here, we report the identification of the sodium channel subunit SCNN1B as a candidate biomarker in gastric cancer. SCNN1B mRNA expression was silenced commonly by promoter hypermethylation in gastric cancer cell lines and primary tumor tissues. Tissue microarray analysis revealed that high expression of SCNN1B was an independent prognostic factor for longer survival in gastric cancer patients, especially those with late-stage disease. Functional studies demonstrated that SCNN1B overexpression was sufficient to suppress multiple features of cancer cell pathophysiology in vitro and in vivo Mechanistic investigations revealed that SCNN1B interacted with the endoplasmic reticulum chaperone, GRP78, and induced its degradation via polyubiquitination, triggering the unfolded protein response (UPR) via activation of PERK, ATF4, XBP1s, and C/EBP homologous protein and leading in turn to caspase-dependent apoptosis. Accordingly, SCNN1B sensitized gastric cancer cells to the UPR-inducing drug tunicamycin. GRP78 overexpression abolished the inhibitory effect of SCNN1B on cell growth and migration, whereas GRP78 silencing aggravated growth inhibition by SCNN1B. In summary, our results identify SCNN1B as a tumor-suppressive function that triggers UPR in gastric cancer cells, with implications for its potential clinical applications as a survival biomarker in gastric cancer patients. Cancer Res; 77(8); 1968-82. ©2017 AACR.

Peptostreptococcus anaerobius Induces Intracellular Cholesterol Biosynthesis in Colon Cells to Induce Proliferation and Causes Dysplasia in Mice.

BACKGROUND & AIMS: Stool samples from patients with colorectal cancer (CRC) have a higher abundance of Peptostreptococcus anaerobius than stool from individuals without CRC, based on metagenome sequencing. We investigated whether P anaerobius contributes to colon tumor formation in mice and its possible mechanisms of carcinogenesis. METHODS: We performed quantitative polymerase chain reaction analyses to measure P anaerobius in 112 stool samples and 255 colon biopsies from patients with CRC or advanced adenoma and from healthy individuals (controls) undergoing colonoscopy examination at hospitals in Hong Kong and Beijing. C57BL/6 mice were given broad-spectrum antibiotics, followed by a single dose of azoxymethane, to induce colon tumor formation. Three days later, mice were given P anaerobius or Esherichia coli MG1655 (control bacteria), via gavage, for 6 weeks. Some mice were also given the nicotinamide adenine dinucleotide phosphate oxidase inhibitor apocynin. Intestine tissues were collected and analyzed histologically. The colon epithelial cell line NCM460 and colon cancer cell lines HT-29 and Caco-2 were exposed to P anaerobius or control bacteria; cells were analyzed by immunoblot, proliferation, and bacterial attachment analyses and compared in gene expression profiling studies. Gene expression was knocked down in these cell lines with small interfering RNAs. RESULTS: P anaerobius was significantly enriched in stool samples from patients with CRC and in biopsies from patients with colorectal adenoma or CRC compared with controls. Mice depleted of bacteria and exposed to azoxymethane and P anaerobius had a higher incidence of intestinal dysplasia (63%) compared with mice not given the bacteria (8.3%; P < .01). P anaerobius mainly colonized the colon compared with the rest of the intestine. Colon cells exposed to P anaerobius had significantly higher levels of proliferation than control cells. We found genes that regulate cholesterol biosynthesis, Toll-like receptor (TLR) signaling, and AMP-activated protein kinase signaling to be significantly up-regulated in cells exposed to P anaerobius. Total cholesterol levels were significantly increased in colon cell lines exposed to P anaerobius via activation of sterol regulatory element-binding protein 2. P anaerobius interacted with TLR2 and TLR4 to increase intracellular levels of reactive oxidative species, which promoted cholesterol synthesis and cell proliferation. Depletion of reactive oxidative species by knockdown of TLR2 or TLR4, or incubation of cells with an antioxidant, prevented P anaerobius from inducing cholesterol biosynthesis and proliferation. CONCLUSIONS: Levels of P anaerobius are increased in human colon tumor tissues and adenomas compared with non-tumor tissues; this bacteria increases colon dysplasia in a mouse model of CRC. P anaerobius interacts with TLR2 and TLR4 on colon cells to increase levels of reactive oxidative species, which promotes cholesterol synthesis and cell proliferation.

Black blood T1rho MR imaging may diagnose early stage liver fibrosis: a proof-of-principle study with rat biliary duct ligation model.

BACKGROUND: To explore black blood T1rho (T1ρ) liver imaging and investigate the earliest stage when biliary duct ligation (BDL) induced liver fibrosis can be diagnosed. METHODS: MR was performed at 3 Tesla. A T1ρ prepared 2D fast spin echo (FSE) sequence with acquisition of four spin lock times (TSLs: 1, 10, 30, and 50 msec) and spin-lock frequency of 500 Hz was applied. Inherent black blood effect of FSE and double inversion recovery (DIR) achieved blood signal suppression, and 3 axial sections per liver were obtained. Male Sprague-Dawley rats were scanned at baseline (n=32), and on day-3 (n=13), day-5 (n=11), day-7 (n=10), day-10 (n=4) respectively after BDL. Hematoxylin-eosin (HE) and picrosirius red staining liver histology was obtained at these time points. RESULTS: The physiological liver parenchyma T1ρ was 38.38±1.53 msec (range, 36.05-41.53 msec). Liver T1ρ value elevated progressively after BDL. On day-10 after BDL all experimental animals can be separated from normal liver based on T1ρ measurement with lowest value being 42.82 msec. Day-7 and day-10 liver resembled METAVIR stage-F1/F2 fibrosis, and fibrous area counted for 0.22%±0.13% and 0.38%±0.44% of liver parenchyma area, respectively. CONCLUSIONS: This study provides the first proof-of-principle that T1ρ might diagnose early stage liver fibrosis.