Jianren Gu

CD133 positive hepatocellular carcinoma cells possess high capacity for tumorigenicity.

Recently increasing reported data have suggested that only a small subset of cancer cells possess capability to initiate malignancies including leukemia and solid tumors, which was based on investigation in these cells displaying a distinct surface marker pattern within the primary cancers. CD133 is a putative hematopoietic and neuronal stem‐cell marker, which was also considered as a tumorigenic marker in brain and prostate cancer. We hypothesized that CD133 was a marker closely correlated with tumorigenicity, since it was reported that CD133 expressed in human fetal liver and repairing liver tissues, which tightly associated with hepatocarcinogenesis. Our findings showed that a small population of CD133 positive cells indeed exists in human hepatocellular carcinoma (HCC) cell lines and primary HCC tissues. From SMMC‐7721 cell line, CD133+ cells isolated by MACS manifested high tumorigenecity and clonogenicity as compared with CD133− HCC cells. The implication that CD133 might be one of the markers for HCC cancer stem‐like cells needed further investigation.

Circular RNA profiling reveals an abundant circHIPK3 that regulates cell growth by sponging multiple miRNAs

Circular RNAs (circRNAs) represent a class of widespread and diverse endogenous RNAs that may regulate gene expression in eukaryotes. However, the regulation and function of human circRNAs remain largely unknown. Here we generate ribosomal-depleted RNA sequencing data from six normal tissues and seven cancers, and detect at least 27,000 circRNA candidates. Many of these circRNAs are differently expressed between the normal and cancerous tissues. We further characterize one abundant circRNA derived from Exon2 of the HIPK3 gene, termed circHIPK3. The silencing of circHIPK3 but not HIPK3 mRNA significantly inhibits human cell growth. Via a luciferase screening assay, circHIPK3 is observed to sponge to 9 miRNAs with 18 potential binding sites. Specifically, we show that circHIPK3 directly binds to miR-124 and inhibits miR-124 activity. Our results provide evidence that circular RNA produced from precursor mRNA may have a regulatory role in human cells.

Cancer stem/progenitor cells are highly enriched in CD133+CD44+ population in hepatocellular carcinoma

Both our previous study and other reports have suggested that CD133, originally classified as a hematopoietic stem cell marker, could be used for enrichment of cancer stem cells (CSCs) in human hepatocellular carcinoma (HCC). It was also noted that not all of CD133+ cells were representative of CSCs. Further identification and characterization of CSCs or tumor‐initiating cells in HCC are necessary to better understand hepatocarcinogenesis. In present study, we demonstrated that CSC phenotype could be precisely defined by co‐expression of CD133 and CD44 cell surface markers. CD133+CD44+ HCC cells showed stem cell properties, including extensive proliferation, self‐renewal, and differentiation into the bulk of cancer cells. In vivo xenograft experiments revealed that, actually, the highly tumorigenic capacity of CD133+ cells as previously described was primarily attributed to CD133+CD44+ cell subpopulation, instead of their CD133+CD44− counterparts. Moreover, cells double‐positive for CD133 and CD44 exhibited preferential expression of some stem cell‐associated genes and were more resistant to chemotherapeutic agents due to the upregulation of ATP‐binding cassette (ABC) superfamily transporters, including ABCB1, ABCC1, and ABCG2, further supporting these cells as HCC cell origin. Our findings suggest that CD133+CD44+ cells might represent true cancer stem/progenitor cells in HCC, which could allow a better understanding of HCC initiation and progression, as well as establish a precise target for the development of more effective therapies.

Circular RNA is enriched and stable in exosomes: a promising biomarker for cancer diagnosis

Circular RNA is enriched and stable in exosomes: a promising biomarker for cancer diagnosis

Diagnostic and prognostic implications of microRNAs in human hepatocellular carcinoma

MicroRNAs (miRNAs) are important gene regulators, which are often deregulated in cancers. In this study, the authors analyzed the microRNAs profiles of 78 matched cancer/noncanerous liver tissues from HCC patients and 10 normal liver tissues and found that 69 miRNAs were differentially expressed between hepatocellular carcinoma (HCC) and corresponding noncancerous liver tissues (N). Then the expressions of 8 differentially expressed miRNAs were validated by real time RT PCR. The set of differentially expressed miRNAs could distinctly classify HCC, N and normal liver tissues (NL). Moreover, some of these differentially expressed miRNAs were related to the clinical factors of HCC patients. Most importantly, Kaplan‐Meier estimates and the log‐rank test showed that high expression of hsa‐miR‐125b was correlated with good survival of HCC patients (hazard ratio, 1.787, 95% confidence interval, 1.020–3.133, p = 0.043). The transfection assay showed that overexpression of miR‐125b in HCC cell line could obviously suppress the cell growth and phosporylation of Akt. In conclusion, the authors have demonstrated the diagnostic miRNA profile for HCC, and for the first time, identified the miR‐125b with predictive significance for HCC prognosis.

Gain of miR-151 on chromosome 8q24.3 facilitates tumour cell migration and spreading through downregulating RhoGDIA

Recurrent chromosomal aberrations are often observed in hepatocellular carcinoma (HCC), but little is known about the functional non-coding sequences, particularly microRNAs (miRNAs), at the chromosomal breakpoints in HCC. Here we show that 22 miRNAs are often amplified or deleted in HCC. MicroRNA-151 (miR-151), a frequently amplified miRNA on 8q24.3, is correlated with intrahepatic metastasis of HCC. We further show that miR-151, which is often expressed together with its host gene FAK, encoding focal adhesion kinase, significantly increases HCC cell migration and invasion in vitro and in vivo, mainly through miR-151-5p, but not through miR-151-3p. Moreover, miR-151 exerts this function by directly targeting RhoGDIA, a putative metastasis suppressor in HCC, thus leading to the activation of Rac1, Cdc42 and Rho GTPases. In addition, miR-151 can function synergistically with FAK to enhance HCC cell motility and spreading. Thus, our findings indicate that chromosome gain of miR-151 is a crucial stimulus for tumour invasion and metastasis of HCC.

MicroRNA-30d promotes tumor invasion and metastasis by targeting Galphai2 in hepatocellular carcinoma†

The pathological relevance and significance of microRNAs (miRNAs) in hepatocarcinogenesis have attracted much attention in recent years; however, little is known about the underlying molecular mechanisms through which miRNAs are involved in the development and progression of hepatocellular carcinoma (HCC). In this study, we demonstrate that miR‐30d is frequently up‐regulated in HCC and that its expression is highly associated with the intrahepatic metastasis of HCC. Furthermore, the enhanced expression of miR‐30d could promote HCC cell migration and invasion in vitro and intrahepatic and distal pulmonary metastasis in vivo, while silencing its expression resulted in a reduced migration and invasion. Galphai2 (GNAI2) was identified as the direct and functional target of miR‐30d with integrated bioinformatics analysis and messenger RNA array assay. This regulation was further confirmed by luciferase reporter assays. In addition, our results, for the first time, showed that GNAI2 was frequently suppressed in HCC by way of quantitative reverse‐transcription polymerase chain reaction and immunohistochemical staining assays. The increase of the GNAI2 expression significantly inhibits, whereas knockdown of the GNAI2 expression remarkably enhances HCC cell migration and invasion, indicating that GNAI2 functions as a metastasis suppressor in HCC. The restoration of GNAI2 can inhibit miR‐30d–induced HCC cell invasion and metastasis. Conclusion: The newly identified miR‐30d/GNAI2 axis elucidates the molecular mechanism of HCC cell invasion and metastasis and represents a new potential therapeutic target for HCC treatment. (HEPATOLOGY 2010.)

Methylation profiling of twenty promoter-CpG islands of genes which may contribute to hepatocellular carcinogenesis

BackgroundHepatocellular carcinoma (HCC) presents one of the major health threats in China today. A better understanding of the molecular genetics underlying malignant transformation of hepatocytes is critical to success in the battle against this disease. The methylation state of C5 of the cytosine in the CpG di-nucleotide that is enriched within or near the promoter region of over 50 % of the polymerase II genes has a drastic effect on transcription of these genes. Changes in the methylation profile of the promoters represent an alternative to genetic lesions as causative factors for the tumor-specific aberrant expression of the genes.MethodsWe have used the methylation specific PCR method in conjunction with DNA sequencing to assess the methylation state of the promoter CpG islands of twenty genes. Aberrant expression of these genes have been attributed to the abnormal methylation profile of the corresponding promoter CpG islands in human tumors.ResultsWhile the following sixteen genes remained the unmethylated in all tumor and normal tissues: CDH1, APAF1, hMLH1, BRCA1, hTERC, VHL, RARβ, TIMP3, DAPK1, SURVIVIN, p14ARF, RB1, p15INK4b, APC, RASSF1c and PTEN, varying degrees of tumor specific hypermethylation were associated with the p16INK4a , RASSF1a, CASP8 and CDH13 genes. For instance, the p16INK4a was highly methylated in HCC (17/29, 58.6%) and less significantly methylated in non-cancerous tissue (4/29. 13.79%). The RASSF1a was fully methylated in all tumor tissues (29/29, 100%), and less frequently methylated in corresponding non-cancerous tissue (24/29, 82.75%).ConclusionsFurthermore, co-existence of methylated with unmethylated DNA in some cases suggested that both genetic and epigenetic (CpG methylation) mechanisms may act in concert to inactivate the p16INK4a and RASSF1a in HCC. Finally, we found a significant association of cirrhosis with hypermethylation of the p16INK4a and hypomethylation of the CDH13 genes. For the first time, the survey was carried out on such an extent that it would not only provide new insights into the molecular mechanisms underscoring the aberrant expression of the genes in this study in HCC, but also offer essential information required for a good methylation-based diagnosis of HCC.

The Growth and Metastasis of Human Hepatocellular Carcinoma Xenografts Are Inhibited by Small Interfering RNA Targeting to the Subunit ATP6L of Proton Pump

Extracellular pH is usually low in solid tumors, in contrast to the approximately neutral intracellular pH. V-ATPase, which overly functions in some cancers with metastatic potential, plays an important role in maintaining neutral cytosolic pH, very acidic luminal pH, and acidic extracellular pH. ATP6L, the 16 kDa subunit of proton pump V-ATPase, can provide proton hydrophilic transmembrane path. In this study, ATP6L in a human hepatocellular carcinoma cell line with highly metastatic potential (HCCLM3) was knocked down using DNA vector-based small interfering RNA (siRNA) to suppress the metastasis. The expression of ATP6L in stable siRNA transfectants, designated as si-HCCLM3 cells, was inhibited by approximately 60%. The proton secretion and the intracellular pH recovery from NH4Cl-prepulsed acidification were inhibited in si-HCCLM3 cells. The invasion of the si-HCCLM3 cells was suppressed in vitro; simultaneously, the expressions of matrix metalloproteinase-2 and gelatinase activity were reduced. In vivo, at 35th day after implantation of the si-HCCLM3 xenografts into the livers in BalB/c (nu+/nu+) mice, the size of liver tumor tissues was dramatically smaller in siRNA group than in the controlled group. The most impressing effect of ATP6L siRNA is its striking reduction of the metastatic potential of HCCLM3 cells. In control, all eight mice had the intrahepatic metastasis and six of eight the pulmonary metastasis, whereas in ATP6L siRNA-treated group, three of eight had the intrahepatic metastasis and only one of eight the pulmonary metastasis. The results suggest that the inhibition of V-ATPase function via knockdown of ATP6L expression using RNA interfering technology can effectively retard the cancer growth and suppress the cancer metastasis by the decrease of proton extrusion and the down-regulation of gelatinase activity.

Upregulation of miR-23a∼27a∼24 decreases transforming growth factor-beta-induced tumor-suppressive activities in human hepatocellular carcinoma cells

Transforming growth factor‐beta (TGF‐beta) plays a dual and complex role in human cancer. In this report, we observe a specific set of MicroRNAs (miRNAs) changed in response to TGF‐beta in human hepatocellular carcinoma (HCC) cells by miRNA microarray screening. A cluster of miRNA, miR‐23a∼27a∼24, is induced in an early stage by TGF‐beta in Huh‐7 cells. Knockdown of Smad4, Smad2 or Smad3 expression by RNA interference can attenuate the response of miR‐23a∼27a∼24 to TGF‐beta addition, indicating that this induction is dependent on Smad pathway. We also explore that miR‐23a∼27a∼24 can function as an antiapoptotic and proliferation‐promoting factor in liver cancer cells. In addition, expression of this miRNA cluster is found to be remarkably upregulated in HCC tissues versus normal liver tissues. These findings suggest a novel, alternative mechanism through which TGF‐beta could induce specific miRNA expression to escape from tumor‐suppressive response in HCC cells.