Switching of pyruvate kinase isoform L to M2 promotes metabolic reprogramming in hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is an aggressive tumor, with a high mortality rate due to late symptom presentation and frequent tumor recurrences and metastasis. It is also a rapidly growing tumor supported by different metabolic mechanisms; nevertheless, the biological and molecular mechanisms involved in the metabolic reprogramming in HCC are unclear. In this study, we found that pyruvate kinase M2 (PKM2) was frequently over-expressed in human HCCs and its over-expression was associated with aggressive clinicopathological features and poor prognosis of HCC patients. Furthermore, knockdown of PKM2 suppressed aerobic glycolysis and cell proliferation in HCC cell lines in vitro. Importantly, knockdown of PKM2 hampered HCC growth in both subcutaneous injection and orthotopic liver implantation models, and reduced lung metastasis in vivo. Of significance, PKM2 over-expression in human HCCs was associated with a down-regulation of a liver-specific microRNA, miR-122. We further showed that miR-122 interacted with the 3UTR of the PKM2 gene. Re-expression of miR-122 in HCC cell lines reduced PKM2 expression, decreased glucose uptake in vitro, and suppressed HCC tumor growth in vivo. Our clinical data and functional studies have revealed a novel biological mechanism involved in HCC metabolic reprogramming.published_or_final_versio

MiR-200b/200c/429 subfamily negatively regulates Rho/ROCK signaling pathway to suppress hepatocellular carcinoma metastasis

MiR-200 family is an important regulator of epithelial-mesenchymal transition and has been implicated in human carcinogenesis. However, their expression and functions in human cancers remain controversial. In the work presented here, we showed that miR-200 family members were frequently down-regulated in hepatocellular carcinoma (HCC). Although all five members of miR-200 family inhibited ZEB1/2 expression in HCC cell lines, we showed that overexpression only of the miR-200b/200c/429 subfamily, but not the miR-200a/141 subfamily, resulted in impeded HCC cell migration. Further investigations led to the identification of RhoA and ROCK2 as specific down-stream targets of the miR-200b/200c/429 subfamily. We demonstrated that the miR-200b/200c/429 subfamily inhibited HCC cell migration through modulating Rho/ROCK mediated cell cytoskeletal reorganization and cell-substratum adhesion. Re-expression of miR-200b significantly suppressed lung metastasis of HCC cells in an orthotopic liver implantation model in vivo. In conclusion, our findings identified the miR-200b/200c/429 subfamily as metastasis suppressor microRNAs in human HCC and highlighted the functional discrepancy among miR-200 family members.published_or_final_versio

Finding Direction in the Search for Selection.

Tests for positive selection have mostly been developed to look for diversifying selection where change away from the current amino acid is often favorable. However, in many cases we are interested in directional selection where there is a shift toward specific amino acids, resulting in increased fitness in the species. Recently, a few methods have been developed to detect and characterize directional selection on a molecular level. Using the results of evolutionary simulations as well as HIV drug resistance data as models of directional selection, we compare two such methods with each other, as well as against a standard method for detecting diversifying selection. We find that the method to detect diversifying selection also detects directional selection under certain conditions. One method developed for detecting directional selection is powerful and accurate for a wide range of conditions, while the other can generate an excessive number of false positives

Enhancer of Zeste Homolog 2 (EZH2) was involved in Hepatocellular Carcinoma (HCC) Progression Through Gene Silencing

The 16th Hong Kong International Cancer Congress & 6th Annual Meeting, Hong Kong, 4-6 November 2009

Epigenetic Regulation of EZH2 and Its Targeted MicroRNAs

Polycomb group (PcG) proteins are transcriptional repressors which function to silence expressions of developmental and differentiation genes in eukaryotic cells. PcG proteins assemble into complexes termed Polycomb Repressive Complex (PRC) 1 and 2, and they elicit a cascade of epigenetic silencing events starting from trimethylation of the 27th lysine residue on histone H3 by the core PRC2 protein Enhancer of Zeste Homolog 2 (EZH2). In human cancers, PcG-mediated epigenetic silencing activity is increased as a result of upregulation of EZH2 and other PcG proteins. Consequentially, EZH2 is implicated in cancer development through epigenetic repression of tumor suppressor genes. MicroRNAs (miRNAs) are small, endogenously produced non-coding RNAs which function to negatively regulate the expression of their target mRNAs. MiRNA regulation is widespread and virtually over all cellular processes. In recent years, miRNAs have emerged as critical mediators in cancer pathogenesis. Remarkably, EZH2 can epigenetically silence miRNAs, while miRNAs also exert negative control over EZH2 expression, establishing a self-regulatory loop to reinforce their cancer specific roles. In this chapter, we review the current understanding of EZH2 and its regulated miRNAs in malignancies

RhoGTPases and Rho-effectors in hepatocellular carcinoma metastasis: ROCK N' Rho move it

Hepatocellular carcinoma (HCC) is an intractable disease with an extremely high mortality rate. Metastasis is the major factor of liver failure, tumour recurrence and death in HCC patients. Unfortunately, no promising curative therapy for HCC metastasis is available as yet; therefore, treatment for advanced HCC still remains a formidable challenge. A large body of evidence has demonstrated that the RhoGTPases/Rho-effector pathway plays important roles in mediating HCC metastasis based on their foremost functions in orchestrating the cell cytoskeletal reorganization. This review will first discuss the general principles of cancer metastasis and cancer cell movement with a particular focus on HCC. We will then summarize the implications of various members in the RhoGTPases/Rho-effectors signalling cascade including the upstream RhoGTPase regulators RhoGTPases and Rho-effectors and their downstream targets in HCC metastasis. Finally, we will discuss the therapeutic insight of targeting the RhoGTPases/Rho-effector pathway in HCC. Taken together, the literature demonstrates the importance of the RhoGTPases/Rho-effector signalling pathway in HCC metastasis and marks the necessity to have a more thorough knowledge of this complicated signalling network in order to develop novel therapeutic strategies for HCC patients. © 2010 John Wiley & Sons A/S.link_to_subscribed_fulltex

Overexpression of the histone methyltransferase enhancer of zeste homolog 2 was involved in multistep hepatocarcinogenesis and metastasis of hepatocellular carcinoma

Background: Post-translational modifications on histone N-terminal tails are tightly associated with gene transcription regulation. Accumulating evidence has suggested that aberrant histone modifications are implicated in malignancy development. However, the roles and mechanisms of aberrant histone modifications in the development of hepatocellular carcinoma (HCC) are still warranted. In a pilot study, we observed that Enhancer of zeste homolog 2 (EZH2), a histone methyltransferase specific for H3K27, was frequently deregulated in human HCC. The purpose of this present study is to investigate the role of EZH2 in hepatocarcinogenesis. Experimental Design: The expression of EZH2 mRNA and protein in primary HCC and corresponding non-tumorous livers were determined by real-time quantitative RT-PCR and immunohistochemistry, respectively. Clinicopathological analysis was also done to correlate EZH2 overexpression with clinicopathological parameters of HCC patients. Ectopic overexpression and RNA interference knockdown approaches were employed to study the functional implication of EZH2 in HCC cell lines. Results: Real-time quantitative RT-PCR was performed in 59 pairs of primary HCC samples and overexpression of EZH2 mRNA was found in 70% of primary HCC. Immunohistochemistry study of tissue microarrays consisted of 108 pairs of primary HCC also revealed that both number of positive cells and the intensity of EZH2 nuclear staining were significantly higher in primary HCC than their corresponding non-tumorous livers. Ectopic overexpression of EZH2 significantly increased the H3K27 trimethylation level in HCC cell lines. We also found that the expression level of EZH2 exhibited a stepwise increase along the multistep hepatocarcinogenesis, suggesting that overexpression of EZH2 may contribute to HCC progression. Furthermore, overexpression of EZH2 in HCC was significantly associated with aggressive tumor behaviors in HCC patients including the presence of venous invasion (p=0.043) and liver invasion (p=0.014), and the absence of tumor encapsulation (p=0.043). Consistently, knockdown of EZH2 by small interfering RNA suppressed migration of HCC cell lines, suggesting that upregulated EZH2 may contribute to the HCC metastasis. Conclusions: Our findings indicated that EZH2 was frequently upregulated in human HCC and was associated with HCC progression as well as the metastatic phenotypes.The 100th Annual Meeting of the American Association for Cancer Research (AACR 2009), San Diego, CA., 18-22 April 2009. In Proceedings of AACR 2009, abstract no. 49

Overexpression of Enhancer of Zeste homolog 2 (EZH2) promotes HCC metastasis via epigenetic silencing of multiple anti-metastatic microRNAs

Among Top Scored PostersPosters - Session 28. Molecular pathogenesis, cell biology and translational research: no. P-001BACKGROUND: Epigenetic alterations and microRNA deregulation are common events in hepatocarcinogenesis. Analyzing the expression levels of 90 epigenetic modifiers, we found that Enhancer of Zeste homolog 2 ...link_to_OA_fulltex

SUV39H1 promotes HCC tumorigenesis and is targeted by tumor suppressive miRNA-125b

Poster Session 1 - Chromatin Regulators: abstract no. 1059Epigenetic alternation is a common dysregulated event in hepatocellular carcinoma (HCC) development. Through interrogating the expression of 90 major epigenetic regulating genes, we identified SUV39H1, the prototype histone methyltransferase as one of the most frequently up-regulated epigenetic regulators in human HCC (61%, 23/38). SUV39H1 is responsible for H3K9 trimethylation establishment and essentially involves in heterochromatin formation and transcriptional repression. We found that SUV39H1 up-regulation in human HCC was significantly associated with ...link_to_OA_fulltextThe Annual Meeting of the American Association for Cancer Research (AACR 2012), Chicago, IL., 31 March-4 April 2012