Yingjun Zhao

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.

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.

Upregulation of miR-23a approximately 27a approximately 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.

Genome‐wide screening reveals that miR‐195 targets the TNF‐α/NF‐κB pathway by down‐regulating IκB kinase alpha and TAB3 in hepatocellular carcinoma

Nuclear factor kappa B (NF‐κB) is an important factor linking inflammation and tumorigenesis. In this study we experimentally demonstrated through a high‐throughput luciferase reporter screen that NF‐κB signaling can be directly targeted by nearly 29 microRNAs (miRNAs). Many of these miRNAs can directly target NF‐κB signaling nodes by binding to their 3′ untranslated region (UTR). miR‐195, a member of the miR‐15 family, is frequently down‐regulated in gastrointestinal cancers, especially in hepatocellular carcinoma (HCC). The expression level of miR‐195 is inversely correlated with HCC tumor size. We further show that miR‐195 suppresses cancer cell proliferation and migration in vitro and reduces tumorigenicity and metastasis in vivo. Additionally, miR‐195 may exert its tumor suppressive function by decreasing the expression of multiple NF‐κB downstream effectors by way of the direct targeting of IKKα and TAB3. Conclusion: Multiple miRNAs are involved in the NF‐κB signaling pathway and miR‐195 plays important inhibitory roles in cancer progression and may be a potential therapeutic target. (Hepatology 2013;58:654–666)

Genome-wide copy number analyses identified novel cancer genes in hepatocellular carcinoma†‡

A powerful way to identify driver genes with causal roles in carcinogenesis is to detect genomic regions that undergo frequent alterations in cancers. Here we identified 1,241 regions of somatic copy number alterations in 58 paired hepatocellular carcinoma (HCC) tumors and adjacent nontumor tissues using genome‐wide single nucleotide polymorphism (SNP) 6.0 arrays. Subsequently, by integrating copy number profiles with gene expression signatures derived from the same HCC patients, we identified 362 differentially expressed genes within the aberrant regions. Among these, 20 candidate genes were chosen for further functional assessments. One novel tumor suppressor (tripartite motif‐containing 35 [TRIM35]) and two putative oncogenes (hairy/enhancer‐of‐split related with YRPW motif 1 [HEY1] and small nuclear ribonucleoprotein polypeptide E [SNRPE]) were discovered by various in vitro and in vivo tumorigenicity experiments. Importantly, it was demonstrated that decreases of TRIM35 expression are a frequent event in HCC and the expression level of TRIM35 was negatively correlated with tumor size, histological grade, and serum alpha‐fetoprotein concentration. Conclusion: These results showed that integration of genomic and transcriptional data offers powerful potential for identifying novel cancer genes in HCC pathogenesis. (HEPATOLOGY 2011;)

Sphingosine kinase 1 promotes tumour cell migration and invasion via the S1P/EDG1 axis in hepatocellular carcinoma

Sphingosine kinase 1 (SphK1), which phosphorylates sphingosine to sphingosine‐1‐phosphate (S1P), is overexpressed in various types of cancers, and may act as an oncogene in tumorigenesis. However, little is known about the precise role of the SphK1/S1P pathway in human liver cancer, especially regarding the metastasis of hepatocellular carcinoma (HCC).

MicroRNA-26a acts as a tumor suppressor inhibiting gallbladder cancer cell proliferation by directly targeting HMGA2

MicroRNAs (miRNAs) are a class of small, single-stranded, non-coding RNA molecules which can act as oncogenes or tumor suppressor genes in human cancer. However, the possible functions and mechanisms of miRNA action in gallbladder cancer (GBC) have not been elucidated. In the present study, it was found that miR-26a was often downregulated in GBC and the expression of miR-26a was associated with neoplasm histological grade. miR-26a significantly inhibited the proliferation of GBC cells based on the gain-of-function assays. Furthermore, we demonstrated that high mobility group AT-hook 2 (HMGA2) was a direct target of miR-26a. The results showed that HMGA2 mRNA levels and miR-26a levels were negatively correlated. In addition, we confirmed that reintroduction of HMGA2 antagonized the inhibition of miR-26a to GBC cell proliferation and all these effects were achieved through the cell cycle. Together, all these results suggest that miR-26a expression contributes to GBC proliferation by targeting HMGA2. miR-26a shows promise as a prognosis factor and therapeutic target of GBC patients.

Disruption of xCT inhibits cell growth via the ROS/autophagy pathway in hepatocellular carcinoma.

xCT, the functional subunit of the system x(c)(-) which plays an important role in maintaining intracellular glutathione (GSH) levels, is expressed in various malignant tumors. Here, we demonstrated that xCT expression is often elevated in HCC and is associated with poor prognosis in HCC patients; moreover, disruption of xCT suppressed HCC cell growth both in vitro and in vivo. xCT dysfunction has also been shown to increase intracellular reactive oxygen species (ROS) levels, thus in turn led to autophagic cell death of HCC cells. Taken together, these findings suggest that xCT may be a promising therapeutic target for human HCC.

MicroRNA-135a acts as a putative tumor suppressor by directly targeting very low density lipoprotein receptor in human gallbladder cancer

The precise functions and mechanisms of microRNAs (miR) in gallbladder cancer (GBC) remain elusive. In this study, we found that miR‐135a‐5p expression is often dampened and correlated with neoplasm histologic grade in GBC. MicroRNA‐135a‐5p introduction clearly inhibited GBC cell proliferation in vitro and in vivo. Moreover, very low density lipoprotein receptor (VLDLR), which is often upregulated in GBC tissues, was identified as a direct functional target of miR‐135a‐5p. Furthermore, the p38 MAPK pathway was proven to be involved in miR‐135a‐VLDLR downstream signaling. Together, these results suggested that the miR‐135a–VLDLR–p38 axis may contribute to GBC cell proliferation.

MiR-525-3p enhances the migration and invasion of liver cancer cells by downregulating ZNF395.

Liver cancer is one of leading causes of cancer-related deaths. A deeper mechanistic understanding of liver cancer could lead to the development of more effective therapeutic strategies. In our previous work, we screened 646 miRNAs and identified 11 that regulate liver cancer cell migration. The current study shows that miR-525-3p is frequently up-regulated in liver cancer tissues, and enhanced expression of miR-525-3p can promote liver cancer cell migration and invasion. Zinc finger protein 395 (ZNF395) is the direct functional target gene for miR-525-3p, and it is frequently down-regulated in liver cancer tissues. High expression of ZNF395 can significantly inhibit while knockdown of ZNF395 expression can markedly enhance the migration and invasion of liver cancer cells, suggesting that ZNF395 suppresses metastasis in liver cancer. Down-regulation of ZNF395 can mediate miR-525-3p induced liver cancer cell migration and invasion. In conclusion, miR-525-3p promotes liver cancer cell migration and invasion by directly targeting ZNF395, and the fact that miR-525-3p and ZNF395 both play important roles in liver cancer progression makes them potential therapeutic targets.