Jinqiang Zhang

MicroRNA-26a Promotes Cholangiocarcinoma Growth by Activating β-catenin

BACKGROUND & AIMS MicroRNAs (miRNAs) have been implicated in the development and progression of human cancers. We investigated the roles and mechanisms of miR-26a in human cholangiocarcinoma. METHODS We used in situ hybridization and quantitative reverse transcriptase polymerase chain reaction to measure expression of miR-26a in human cholangiocarcinoma tissues and cell lines (eg, CCLP1, SG231, HuCCT1, TFK1). Human cholangiocarcinoma cell lines were transduced with lentiviruses that expressed miR-26a1 or a scrambled sequence (control); proliferation and colony formation were analyzed. We analyzed growth of human cholangiocarcinoma cells that overexpress miR-26a or its inhibitor in severe combined immune-deficient mice. Immunoblot, immunoprecipitation, DNA pull-down, immunofluorescence, and luciferase reporter assays were used to measure expression and activity of glycogen synthase kinase (GSK)-3β, β-catenin, and related signaling molecules. RESULTS Human cholangiocarcinoma tissues and cell lines had increased levels of miR-26a compared with the noncancerous biliary epithelial cells. Overexpression of miR-26a increased proliferation of cholangiocarcinoma cells and colony formation in vitro, whereas miR-26 depletion reduced these parameters. In severe combined immune-deficient mice, overexpression of miR-26a by cholangiocarcinoma cells increased tumor growth and overexpression of the miR-26a inhibitor reduced it. GSK-3β messenger RNA was identified as a direct target of miR-26a by computational analysis and experimental assays. miR-26a-mediated reduction of GSK-3β resulted in activation of β-catenin and induction of several downstream genes including c-Myc, cyclinD1, and peroxisome proliferator-activated receptor δ. Depletion of β-catenin partially prevented miR-26a-induced tumor cell proliferation and colony formation. CONCLUSIONS miR-26a promotes cholangiocarcinoma growth by inhibition of GSK-3β and subsequent activation of β-catenin. These signaling molecules might be targets for prevention or treatment of cholangiocarcinoma.

Epigenetic regulation of MicroRNA‐122 by peroxisome proliferator activated receptor‐gamma and hepatitis b virus X protein in hepatocellular carcinoma cells

MicroRNA‐122 (miR‐122), a pivotal liver‐specific miRNA, has been implicated in several liver diseases including hepatocellular carcinoma (HCC) and hepatitis C and B viral infection. This study aimed to explore epigenetic regulation of miR‐122 in human HCC cells and to examine the effect of hepatitis C virus (HCV) and hepatitis B virus (HBV). We performed microRNA microarray analysis and identified miR‐122 as the most up‐regulated miRNA (6‐fold) in human HCC cells treated with 5′aza‐2′deoxycytidine (5‐Aza‐CdR, DNA methylation inhibitor) and 4‐phenylbutyric acid (PBA, histone deacetylation inhibitor). Real‐time polymerase chain reaction (PCR) analysis verified significant up‐regulation of miR‐122 by 5′aza and PBA in HCC cells, and to a lesser extent in primary hepatocytes. Peroxisome proliferator activated receptor‐gamma (PPARγ) and retinoid X receptor alpha (RXRα) complex was found to be associated with the DR1 and DR2 consensus site in the miR‐122 gene promoter which enhanced miR‐122 gene transcription. 5‐Aza‐CdR and PBA treatment increased the association of PPARγ/RXRα, but decreased the association of its corepressors (N‐CoR and SMRT), with the miR‐122 DR1 and DR2 motifs. The aforementioned DNA‐protein complex also contains SUV39H1, an H3K9 histone methyl transferase, which down‐regulates miR‐122 expression. Conclusions: These findings establish a novel role of the PPARγ binding complex for epigenetic regulation of miR‐122 in human HCC cells. Moreover, we show that hepatitis B virus X protein binds PPARγ and inhibits the transcription of miR‐122, whereas hepatitis C viral particles exhibited no significant effect; these findings provide mechanistic insight into reduction of miR‐122 in patients with HBV but not with HCV infection. (Hepatology 2013;58:1681–1692)

ABCC4 copy number variation is associated with susceptibility to esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is the eighth most common cause of cancer-related death worldwide. However, previous genome-wide single nucleotide polymorphism association analyses have not explained the high heritability associated with ESCC. In this study, we performed genome-wide copy number variation (CNV) analysis on 128 discordant sibling pairs to identify novel genes that contribute to ESCC susceptibility. A total of 57 774 individual CNVs were identified, and an interactive network of common CNV-associated genes was constructed, which showed that several ABC transporter genes contain CNVs in ESCC patients. Independent validation of a CNV at 13q32.1 in 1048 northern Chinese Han subjects demonstrated that the amplification of ABCC4 significantly correlated with ESCC risk [odds ratio: 3.36 (1.65-7.93), P = 0.0013]. Immunohistochemistry staining suggested that high copy numbers correlated with increased protein levels. High expression of ABCC4 was an independent poor prognostic factor for ESCC [relative risk: 1.73 (1.10-2.73), P = 0.0181]. The CNV region showed strong enhancer activity. Furthermore, inhibition of ABCC4 protein in ESCC cells decreased cell proliferation and motility via the inhibition of COX-2, PGE2 receptors and c-Myc expression; AKT, extracellular signal-regulated kinase and cAMP response element-binding protein phosphorylation; and β-catenin nuclear translocation in ESCC cells. In conclusion, the CNV at 13q32.1 is associated with ESCC susceptibility, and a gene within this locus, ABCC4, activates the oncogenic pathways in ESCC and thus facilitates cancer cell development and progression. A direct genetic contribution of ESCC risk through CNV common variants was determined in this study, and ABCC4 might therefore have predictive and therapeutic potential for ESCC.

SELEX aptamer used as a probe to detect circulating tumor cells in peripheral blood of pancreatic cancer patients.

Many studies have shown that the quantity and dynamics of circulating tumor cells (CTCs) in peripheral blood of patients afflicted with solid tumours have great relevance in therapeutic efficacy and prognosis. Different methods based on various strategies have been developed to isolate and identify CTCs, but their efficacy needs to be improved because of the rarity and complexity of CTCs. This study was designed to examine the possibility of using a SELEX aptamer (BC-15) as a probe to identify rare CTCs out of background nucleated cells. Aptamer BC-15 was selected from a random oligonucleotide library screened against human breast cancer tissue. Fluorescence staining showed that BC-15 had a high affinity for nuclei of human cancer cell lines of various origins as well as CTCs isolated from pancreatic cancer patients, whereas its binding capacity for non-tumor breast epithelial cells and leukocytes was almost undetectable. BC-15+/CD45- cells in cancer patient blood were also found to be cytokeratins 18-positive and aneuploid by immunofluorescence staining and fluorescent in situ hybridization, respectively. Finally, the aptamer method was compared with the well-established anti-cytokeratin method using 15 pancreatic cancer patient blood samples, and enumeration indicated no difference between these two methods. Our study establishes a novel way to identify CTCs by using a synthetic aptamer probe. This new approach is comparable with the anti-cytokeratin-based CTC identification method.

Active glycolytic metabolism in CD133(+) hepatocellular cancer stem cells: regulation by MIR-122

Although altered metabolic pathway is an important diagnostic maker and therapeutic target in cancer, it is poorly understood in cancer stem cells (CSCs). Here we show that the CD133 (+) hepatocellular CSCs have distinct metabolic properties, characterized by more active glycolysis over oxidative phosphorylation, compared to the CD133 (−) cells. Inhibition of PDK4 and LDHA markedly suppresses CD133 (+) stemness characteristics and overcome resistance to sorafenib (current chemotherapeutic agent for hepatocellular cancer). Addition of glucose or lactate to CD133 (−) cells promotes CSC phenotypes, as evidenced by increased CD133 (+) cell population, elevated stemness gene expression and enhanced spheroid formation. Furthermore, the liver-specific miRNA, miR-122, inhibits CSC phenotypes by regulating glycolysis through targeting PDK4. Our findings suggest that enhanced glycolysis is associated with CD133 (+) stem-like characteristics and that metabolic reprogramming through miR-122 or PDK4 may represent a novel therapeutic approach for the treatment of hepatocellular cancer.

Omega-3 Polyunsaturated Fatty Acids Upregulate 15-PGDH Expression in Cholangiocarcinoma Cells by Inhibiting miR-26a/b Expression

Prostaglandin E2 (PGE2) is a proinflammatory lipid mediator that promotes cancer growth. The 15-hydroxyprostaglandin dehydrogenase (15-PGDH) catalyzes oxidation of the 15(S)-hydroxyl group of PGE2, leading to its inactivation. Therefore, 15-PGDH induction may offer a strategy to treat cancers that are driven by PGE2, such as human cholangiocarcinoma. Here, we report that omega-3 polyunsaturated fatty acids (ω-3 PUFA) upregulate 15-PGDH expression by inhibiting miR-26a and miR-26b, thereby contributing to ω-3 PUFA-induced inhibition of human cholangiocarcinoma cell growth. Treatment of human cholangiocarcinoma cells (CCLP1 and TFK-1) with ω-3 PUFA (DHA) or transfection of these cells with the Fat-1 gene (encoding Caenorhabditis elegans desaturase, which converts ω-6 PUFA to ω-3 PUFA) significantly increased 15-PGDH enzymes levels, but with little effect on the activity of the 15-PGDH gene promoter. Mechanistic investigations revealed that this increase in 15-PGDH levels in cells was mediated by a reduction in the expression of miR-26a and miR-26b, which target 15-PGDH mRNA and inhibit 15-PGDH translation. These findings were extended by the demonstration that overexpressing miR-26a or miR-26b decreased 15-PGDH protein levels, reversed ω-3 PUFA-induced accumulation of 15-PGDH protein, and prevented ω-3 PUFA-induced inhibition of cholangiocarcinoma cell growth. We further observed that ω-3 PUFA suppressed miR-26a and miR-26b by inhibiting c-myc, a transcription factor that regulates miR-26a/b. Accordingly, c-myc overexpression enhanced expression of miR-26a/b and ablated the ability of ω-3 PUFA to inhibit cell growth. Taken together, our results reveal a novel mechanism for ω-3 PUFA-induced expression of 15-PGDH in human cholangiocarcinoma and provide a preclinical rationale for the evaluation of ω-3 PUFA in treatment of this malignancy.

Malignant characteristics of circulating tumor cells and corresponding primary tumor in a patient with esophageal squamous cell carcinoma before and after surgery

We report the malignant characteristics of circulating tumor cells (CTCs) and the corresponding molecular features of the primary tumor in a patient with esophageal squamous cell carcinoma (ESCC). A 70-year-old male patient was diagnosed with TNM stage T3N0M0 ESCC. Before surgery, seven intact CTCs and 12 CTCs with a fragmented membrane were detected in 7.5 mL of peripheral blood by immunofluorescence staining. One week after radical resection of the primary tumor, four CTCs were identified in 7.5ml peripheral blood. All CTCs were confirmed as having a malignant phenotype by chromosomal analysis and routine cell staining. Ninety percent of the CTCs were found to have polysomic chromosomes 8 and 20 by fluorescence in situ hybridization (FISH). Immunofluorescence analysis showed that all of the primary tumor cells detected were cytokeratin8/18/19 (CK8/18/19)-positive, but only 1% were CD133-positive. The serum CA19-9 and CEA level were normal in the process of diseases. The patient died 6 months after surgery as a result of lung metastases and other complications. The results of this study suggest that the dynamics and malignant characteristics of both CTCs and the corresponding primary tumor during the disease process may predict tumor burden and the risk of relapse and metastasis.

miR-150 Deficiency Protects against FAS-Induced Acute Liver Injury in Mice through Regulation of AKT

Although miR-150 is implicated in the regulation of immune cell differentiation and activation, it remains unknown whether miR-150 is involved in liver biology and disease. This study was performed to explore the potential role of miR-150 in LPS/D-GalN and Fas-induced liver injuries by using wild type and miR-150 knockout (KO) mice. Whereas knockout of miR-150 did not significantly alter LPS/D-GalN-induced animal death and liver injury, it protected against Fas-induced liver injury and mortality. The Jo2-induced increase in serum transaminases, apoptotic hepatocytes, PARP cleavage, as well as caspase-3/7, caspase-8, and caspase-9 activities were significantly attenuated in miR-150 KO mice. The liver tissues from Jo2-treated miR-150 KO mice expressed higher levels of Akt1, Akt2, total Akt, as well as p-Akt(Ser473) compared to the wild type livers. Pretreatment with the Akt inhibitor V reversed Jo2-induced liver injury in miR-150 KO mice. The primary hepatocytes isolated from miR-150 KO mice also showed protection against Fas-induced apoptosis in vitro (characterized by less prominent PARP cleavage, less nuclear fragmentation and less caspase activation) in comparison to hepatocytes from wild type mice. Luciferase reporter assays in hepatocytes transfected with the Akt1 or Akt2 3’-UTR reporter constructs (with or without mutation of miR-150 binding site) established Akt1 and Akt2 as direct targets of miR-150. Tail vein injection of lentiviral particles containing pre-miR-150 enhanced Jo2-induced liver injury in miR-150 KO mice. These findings demonstrate that miR-150 deficiency prevents Fas-induced hepatocyte apoptosis and liver injury through regulation of the Akt pathway.

TGFβ signaling confers sorafenib resistance via induction of multiple RTKs in hepatocellular carcinoma cells

Transforming growth factor β (TGFβ) is a multifunctional cytokine which is importantly implicated in hepatocarcinogenesis. The current study provides novel evidence that TGFβ upregulates the expression of multiple receptor tyrosine kinases (RTKs), including IGF1R, EGFR, PDGFβR, and FGFR1 in human hepatocellular carcinoma (HCC) cells. This, in turn, sensitized HCC cells to individual cognate RTK ligands, leading to cell survival. Our data showed that the TGFβ‐mediated increase in growth factor sensitivity led to evasion of apoptosis induced by the mutikinase inhibitor, sorafenib. Conversely, we observed that inhibition of the TGFβ signaling pathway by LY2157299, a TGFβRI kinase inhibitor, enhanced sorafenib‐induced apoptosis, in vitro. Our findings disclose an important interplay between TGFβ and RTK signaling pathways, which is critical for hepatocellular cancer cell survival and resistance to therapy.

A novel TGF-β and H19 signaling axis in tumor-initiating hepatocytes that regulates hepatic carcinogenesis.

Functions of transforming growth factor‐β (TGF‐β) in the liver vary depending on specific cell types and their temporal response to TGF‐β during different stages of hepatocarcinogenesis (HCG). Through analysis of tumor tissues from hepatocellular carcinoma (HCC) patients, we were able to cluster hepatic epithelial cell‐derived TGF‐β gene signatures in association with distinct clinical prognoses. To delineate the role of hepatic epithelial TGF‐β signaling in HCC development, we used an experimental system in which tumor‐initiating hepatocytes (TICs) were isolated from TGF‐β receptor II floxed mice (Tgfbr2fl/fl) and transplanted into syngeneic C57BL/6J mice by splenic injection. Recipient mice were then administered Cre‐expressing adenovirus (Ad‐Cre) to inactivate Tgfbr2 in transplanted TICs. After latency, Tgfbr2‐inactivated TICs formed larger and more tumor nodules in recipient livers compared to TICs without Tgfbr2 inactivation. In vitro analyses revealed that treatment of cultured TICs with TGF‐β inhibited expression of progenitor cell factors (including SRY (sex determining region Y)‐box 2 [Sox2]). RNA sequencing (RNA‐seq) analysis identified H19 as one of the most up‐regulated long noncoding RNA (lncRNA) in association with Tgfbr2 inactivation in TICs. Tgfbr2 inactivation by Ad‐Cre led to a 5‐fold increase of H19 expression in TICs. Accordingly, TGF‐β treatment reduced H19 expression. We observed that forced overexpression of Sox2 in TICs increased transcription of H19, whereas knockdown of Sox2 decreased it. Furthermore, depletion of H19 reduced the progenitor property of TICs in vitro and decreased their tumorigenic potential in vivo. Finally, we observed a low level of H19 mRNA expression in human HCC tissues from patients with the epithelial TGF‐β gene signature in association with favorable prognosis. Conclusion: Our findings describe a TGF‐β and H19 signaling axis by Sox2 in TICs that importantly regulates HCG.