Mengchao Wu

Wnt/β-Catenin Signaling Contributes to Activation of Normal and Tumorigenic Liver Progenitor Cells

Adult hepatic progenitor (oval) cells are facultative stem cells in liver, which participate in a range of human liver diseases, including hepatocellular carcinoma (HCC). However, the molecular pathways regulating the expansion and differentiation of these cells are poorly understood. We show that active Wnt/beta-catenin signaling occurs preferentially within the oval cell population, and forced expression of constitutively active beta-catenin mutant promotes expansion of the oval cell population in the regenerated liver. More importantly, we identify a subpopulation of less differentiated progenitor-like cells in HCC cell lines and primary HCC tissues, which are defined by expression of the hepatic progenitor marker OV6 and endowed with endogenously active Wnt/beta-catenin signaling. These OV6(+) HCC cells possess a greater ability to form tumor in vivo and show a substantial resistance to standard chemotherapy compared with OV6(-) tumor cells. The fraction of tumor cells expressing OV6 is enriched after Wnt pathway activation, whereas inhibition of beta-catenin signaling leads to a decrease in the proportion of OV6(+) cells. In addition, the chemoresistance of OV6(+) HCC progenitor-like cells can be reversed by lentivirus-delivered stable expression of microRNA targeting beta-catenin. These results highlight the importance of the Wnt/beta-catenin pathway in activation and expansion of oval cells in normal rodent models and human HCCs. OV6(+) tumor cells may represent the cellular population that confers HCC chemoresistance, and therapies targeted to the Wnt/beta-catenin signaling may provide a specific method to disrupt this resistance mechanism to improve overall tumor control with chemotherapy.

Prognostic Nomogram for Intrahepatic Cholangiocarcinoma After Partial Hepatectomy

PURPOSE This study aimed to establish an effective prognostic nomogram for intrahepatic cholangiocarcinoma (ICC) after partial hepatectomy. PATIENTS AND METHODS The nomogram was based on a retrospectively study on 367 patients who underwent partial hepatectomy for ICC at the Eastern Hepatobiliary Surgery Hospital from 2002 to 2007. The predictive accuracy and discriminative ability of the nomogram were determined by concordance index (C-index) and calibration curve and compared with five currently used staging systems on ICC. The results were validated using bootstrap resampling and a prospective study on 82 patients operated on from 2007 to 2008 at the same institution. RESULTS On multivariate analysis of the primary cohort, independent factors for survival were serum carcinoembryonic antigen, CA 19-9, tumor diameter and number, vascular invasion, lymph node metastasis, direct invasion, and local extrahepatic metastasis, which were all selected into the nomogram. The calibration curve for probability of survival showed good agreement between prediction by nomogram and actual observation. The C-index of the nomogram for predicting survival was 0.74 (95% CI, 0.71 to 0.77), which was statistically higher than the C-index values of the following systems: American Joint Committee on Cancer (AJCC) seventh edition (0.65), AJCC sixth edition (0.65), Nathan (0.64), Liver Cancer Study Group of Japan (0.64), and Okabayashi (0.67; P < .001 for all). It was also higher (0.74) in predicting survival for the mass-forming type of ICC (P < .001). In the validation cohort, the nomogram discrimination was superior to the five other staging systems (C-index: 0.75 v 0.60 to 0.63; P < .001 for all). CONCLUSION The proposed nomogram resulted in more-accurate prognostic prediction for patients with ICC after partial hepatectomy.

The role of microRNA expression pattern in human intrahepatic cholangiocarcinoma

BACKGROUND/AIMS MicroRNAs are a small non-coding family of genes involved in the regulation of gene expression in a post-transcriptional manner and contribute to cell proliferation, differentiation and apoptosis. Our aims were to identify statistically unique miRNA profiles in human intrahepatic cholangiocarcinoma for diagnosis and investigate their specific involvement in various cell biological processes in cholangiocarcinoma. METHODS Laser capture microdissection techniques and TaqMan miRNA assays for mature miRNAs were performed to assess the genomewide expression of miRNAs in 27 human ICCs, 10 normal cholangiocyte cells and 8 normal liver tissues precisely and quantitatively. Two selected miRNAs, mir-204 and mir-320, were introduced into cholangiocarcinoma cell lines to examine their effects on potential target genes, Bcl-2 and Mcl-1, respectively. RESULTS A cluster of 38 miRNAs was markedly distinguishable between tumor and normal tissues. At least two distinct clusters of tumor samples could be identified that were associated with the higher or lower expression levels of carbohydrate antigen 19-9. Moreover, the exogenous expression of mir-320 or mir-204 could negatively regulate Mcl-1 or Bcl-2 expression and facilitate chemotherapeutic drug-triggered apoptosis. CONCLUSIONS miRNA expression profiles are closely associated with the biological and clinical behavior of ICC. The modulation of aberrantly expressed miRNAs might prove a promising therapeutic strategy.

A prospective, randomized, controlled trial of preoperative transarterial chemoembolization for resectable large hepatocellular carcinoma.

Objective:To evaluate the effect of preoperative transarterial chemoembolization (TACE) for resectable large hepatocellular carcinoma (HCC). Summary Background Data:Resection of HCC is potentially curative, but local recurrence is very common. There is currently no effective neoadjuvant or adjuvant therapy. Methods:From July 2001 to December 2003, 108 patients (hepatitis B carrier = 98.1%) with resectable HCC (≥5 cm) was randomly assigned to preoperative TACE treatment (n = 52) or no preoperative treatment (control group) (n = 56). Results:Five patients (9.6%) in the preoperative TACE group did not receive surgical therapy because of extrahepatic metastasis or liver failure. The preoperative TACE group had a lower resection rate (n = 47, 90.4% vs. n = 56, 100%; P= 0.017), and longer operative time (mean, 176.5 minutes vs. 149.3 minutes; P= 0.042). No significant difference was found between the 2 groups in operative blood loss, surgical morbidity, and hospital mortality. At a median follow-up of 57 months, 41 (78.8%) of 52 patients in the preoperative TACE group and 51 (91.1%) of 56 patients in the control group had recurrent disease (P= 0.087). The 1-, 3-, and 5-year disease-free survival rates were 48.9%, 25.5%, and 12.8%, respectively, for the preoperative TACE group and 39.2%, 21.4%, and 8.9%, respectively, for the control group (P= 0.372). The 1-, 3-, and 5-year overall survival rates were 73.1%, 40.4%, and 30.7%, respectively, for the preoperative TACE group and 69.6%, 32.1%, and 21.1%, respectively, for the control group (P= 0.679). Conclusions:Preoperative TACE did not improve surgical outcome. It resulted in drop-out from definitive surgery because of progression of disease and liver failure.

Endotoxin accumulation prevents carcinogen‐induced apoptosis and promotes liver tumorigenesis in rodents

Increasing evidence suggests that the presence of endotoxemia is of substantial clinical relevance to patients with cirrhosis, but it is unclear whether and how gut‐derived LPS amplifies the tumorigenic response of the liver. We found that the circulating levels of LPS were elevated in animal models of carcinogen‐induced hepatocarcinogenesis. Reduction of LPS using antibiotics regimen in rats or genetic ablation of its receptor Toll‐like receptor 4 (TLR4) in mice prevented excessive tumor growth and multiplicity. Additional investigation revealed that TLR4 ablation sensitizes the liver to carcinogen‐induced toxicity via blocking NF‐κB activation and sensitizing the liver to reactive oxygen species (ROS)‐induced toxicity, but lessens inflammation‐mediated compensatory proliferation. Reconstitution of TLR4‐expressing myeloid cells in TLR4‐deficient mice restored diethylnitrosamine (DEN)‐induced hepatic inflammation and proliferation, indicating a paracrine mechanism of LPS in tumor promotion. Meanwhile, deletion of gut‐derived endotoxin suppressed DEN‐induced cytokine production and compensatory proliferation, whereas in vivo LPS pre‐challenge promotes hepatocyte proliferation. Conclusion: Our data indicate that sustained LPS accumulation represents a pathological mediator of inflammation‐associated hepatocellular carcinoma (HCC) and manipulation of the gut flora to prevent pathogenic bacterial translocation and endotoxin absorption may favorably influence liver function in patients with cirrhosis who are at risk of developing HCC. (Hepatology 2010.)

Nuclear factor high‐mobility group box1 mediating the activation of toll‐like receptor 4 signaling in hepatocytes in the early stage of nonalcoholic fatty liver disease in mice

One of the challenges surrounding nonalcoholic fatty liver disease (NAFLD) is to discover the mechanisms that underlie the initiation of it. The aim of the present study was to elucidate the effects of Toll‐like receptor 4 (TLR4) signaling in liver parenchymal cells during the early stage of NAFLD. Male TLR4‐wildtype, TLR4‐knockout, TLR2‐knockout, MyD88‐knockout, and TRIF‐knockout mice were fed a normal diet or high‐fat diet (HFD). Liver steatosis, alanine aminotransferase levels, nuclear translocation of nuclear factor kappa B (NF‐κB) (p65), macrophage accumulation, and neutrophil infiltration were assessed. Using Kupffer cell depletion or bone marrow transplantation, we examined the potential role of Kupffer cells and myeloid infiltrating cells during the initiation of NAFLD. Immunohistochemistry and western blotting were implemented to determine the release of high‐mobility group box1 (HMGB1). The neutral‐antibody against HMGB1 was used to block the activity of free HMGB1. Here we report that the activation of TLR4 signaling in hepatocytes, accompanied with the relocation of P65 in nucleus, was proven to play an important role during the initiation of NAFLD. Importantly, HMGB1 releasing from hepatocytes in response to free fatty acid (FFA) infusion was first reported as the key molecule for the TLR4/MyD88 activation and cytokines expression in vitro and in vivo. Treatment with neutralizing antibody to HMGB1 protects against FFA‐induced tumor necrosis factor alpha and interleukin‐6 production. Conclusion: Our study supports the notion that TLR4/MyD88 signaling in liver parenchymal cells plays a pivotal role during the early progression of HFD‐induced NAFLD, in which free HMGB1 served as a positive component mediating TLR4 activation. (HEPATOLOGY 2011;)

Hepatic transforming growth factor beta gives rise to tumor‐initiating cells and promotes liver cancer development

Liver cirrhosis is a predominant risk factor for hepatocellular carcinoma (HCC). However, the mechanism underlying the progression from cirrhosis to HCC remains unclear. Herein we report the concurrent increase of liver progenitor cells (LPCs) and transforming growth factor‐β (TGF‐β) in diethylnitrosamine (DEN)‐induced rat hepatocarcinogenesis and cirrhotic livers of HCC patients. Using several experimental approaches, including 2‐acetylaminofluorene/partial hepatectomy (2‐AAF/PHx) and 3,5‐diethoxycarbonyl‐1,4‐dihydrocollidine (DDC)‐elicited murine liver regeneration, we found that activation of LPCs in the absence of TGF‐β induction was insufficient to trigger hepatocarcinogenesis. Moreover, a small fraction of LPCs was detected to coexpress tumor initiating cell (T‐IC) markers during rat hepatocarcinogenesis and in human HCCs, and TGF‐β levels were positively correlated with T‐IC marker expression, which indicates a role of TGF‐β in T‐IC generation. Rat pluripotent LPC‐like WB‐F344 cells were exposed to low doses of TGF‐β for 18 weeks imitating the enhanced TGF‐β expression in cirrhotic liver. Interestingly, long‐term treatment of TGF‐β on WB‐F344 cells impaired their LPC potential but granted them T‐IC properties including expression of T‐IC markers, increased self‐renewal capacity, stronger chemoresistance, and tumorigenicity in NOD‐SCID mice. Hyperactivation of Akt but not Notch, signal transducer and activator of transcription 3 (STAT3), or mammalian target of rapamycin (mTOR) was detected in TGF‐β‐treated WB‐F344 cells. Introduction of the dominant‐negative mutant of Akt significantly attenuated T‐IC properties of those transformed WB‐F344 cells, indicating Akt was required in TGF‐β‐mediated‐generation of hepatic T‐ICs. We further demonstrate that TGF‐β‐induced Akt activation and LPC transformation was mediated by microRNA‐216a‐modulated phosphatase and tensin homolog deleted on chromosome 10 (PTEN) suppression. Conclusion: Hepatoma‐initiating cells may derive from hepatic progenitor cells exposed to chronic and constant TGF‐β stimulation in cirrhotic liver, and pharmaceutical inhibition of microRNA‐216a/PTEN/Akt signaling could be a novel strategy for HCC prevention and therapy targeting hepatic T‐ICs. (HEPATOLOGY 2012;56:2255–2267)

Effects of Inflammatory Factors on Mesenchymal Stem Cells and Their Role in the Promotion of Tumor Angiogenesis in Colon Cancer

Mesenchymal stem cells (MSCs), which are modulated by cytokines present in the tumor microenvironment, play an important role in tumor progression. It is well documented that inflammation is an important part of the tumor microenvironment, so we investigated whether stimulation of MSCs by inflammatory cytokines would contribute to their ability to promote tumor growth. We first showed that MSCs could increase C26 colon cancer growth in mice. This growth-promoting effect was further accelerated when the MSCs were pre-stimulated by inflammatory factors IFN-γ and TNF-α. At the same time, we demonstrated that MSCs pre-stimulated by both inflammatory factors could promote tumor angiogenesis in vivo to a greater degree than untreated MSCs or MSCs pre-stimulated by either IFN-γ or TNF-α alone. A hen egg test-chorioallantoic membrane (HET-CAM) assay showed that treatment of MSC-conditioned medium can promote chorioallantoic membrane angiogenesis in vitro, especially treatment with conditioned medium of MSCs pretreated with IFN-γ and TNF-α together. This mechanism of promoting angiogenesis appears to take place via an increase in the expression of vascular endothelial growth factor (VEGF), which itself takes place through an increase in signaling in the hypoxia-inducible factor 1α (HIF-1α)-dependent pathway. Inhibition of HIF-1α in MSCs by siRNA was found to effectively reduce the ability of MSC to affect the growth of colon cancer in vivo in the inflammatory microenviroment. These results indicate that MSCs stimulated by inflammatory cytokines such as IFN-γ and TNF-α in the tumor microenvironment express higher levels of VEGF via the HIF-1α signaling pathway and that these MSCs then enhance tumor angiogenesis, finally leading to colon cancer growth in mice.

GWAS Identifies Novel Susceptibility Loci on 6p21.32 and 21q21.3 for Hepatocellular Carcinoma in Chronic Hepatitis B Virus Carriers

Genome-wide association studies (GWAS) have recently identified KIF1B as susceptibility locus for hepatitis B virus (HBV)–related hepatocellular carcinoma (HCC). To further identify novel susceptibility loci associated with HBV–related HCC and replicate the previously reported association, we performed a large three-stage GWAS in the Han Chinese population. 523,663 autosomal SNPs in 1,538 HBV–positive HCC patients and 1,465 chronic HBV carriers were genotyped for the discovery stage. Top candidate SNPs were genotyped in the initial validation samples of 2,112 HBV–positive HCC cases and 2,208 HBV carriers and then in the second validation samples of 1,021 cases and 1,491 HBV carriers. We discovered two novel associations at rs9272105 (HLA-DQA1/DRB1) on 6p21.32 (OR = 1.30, P = 1.13×10−19) and rs455804 (GRIK1) on 21q21.3 (OR = 0.84, P = 1.86×10−8), which were further replicated in the fourth independent sample of 1,298 cases and 1,026 controls (rs9272105: OR = 1.25, P = 1.71×10−4; rs455804: OR = 0.84, P = 6.92×10−3). We also revealed the associations of HLA-DRB1*0405 and 0901*0602, which could partially account for the association at rs9272105. The association at rs455804 implicates GRIK1 as a novel susceptibility gene for HBV–related HCC, suggesting the involvement of glutamate signaling in the development of HBV–related HCC.

Hypoxia-induced autophagy contributes to the chemoresistance of hepatocellular carcinoma cells.

Hypoxia commonly exists in solid tumors. In this adverse condition, adaptive responses including autophagy are usually provoked to promote cell survival. In our study, autophagy, a lysosomal-mediated degradation pathway, is demonstrated a protective way to make hepatocellular carcinoma cells be resistant to chemotherapy under hypoxia. Compared with normoxia, chemotherapeutic agents-induced cell death under hypoxia was significantly decreased, as a result of the reduced apoptosis. However, when autophagy was inhibited by 3-MA or siRNA targeted Beclin 1, this reduction was reversed i.e. chemoresistance was attenuated, which means autophagy mediates the chemoresistance under hypoxia. In conclusion, autophagy decreases hepatoma cells sensitization to chemotherapeutic agents by affecting their apoptotic potential.