Doctor of Philosophy, University Of Hong Kong (2011)
Samuel So, Postdoctoral Faculty Sponsor
Mortalin is a stress chaperone belonging to the Hsp70 family of proteins. Frequently enriched in cancers, it is a multifunctional protein and regulates cell proliferation, apoptosis, mitochondrial functions, and the activity of tumor suppressor protein p53. In the present study, we investigated circulating mortalin and its autoantibody in normal, cirrhosis, and cancerous liver. We found that although mortalin is enriched in liver cancer cells and tumors, it is not detected in the serum of either the liver cirrhosis or cancer patients. In contrast, mortalin autoantibody was detected in patients' sera and showed significant correlation with the occurrence of cirrhosis. It is suggested as a potential noninvasive marker for liver cirrhosis.
View details for DOI 10.1007/s12192-015-0592-1
View details for Web of Science ID 000356040200015
View details for PubMedID 25905813
The N-myc downstream regulated gene 1 (NDRG1) is significantly associated with advanced tumor stages and poor survival of hepatocellular carcinoma (HCC), thereby implicating it as a potential target for HCC treatment. We aim to further understand its biological roles in hepatocarcinogenesis, as a means to exploit it for therapeutic purposes. By screening using the ProtoArray® Human Protein Microarrays, we identified glycogen synthase kinase 3β (GSK-3β) and the orphan nuclear receptor (Nur77) as potential interaction partners of NDRG1. These interactions were confirmed in HCC cell lines in vitro by co-immunoprecipitation; and co-localizations of NDRG1 with GSK-3β and Nur77 were observed by immunofluorescence staining. Additionally, high levels of NDRG1 competitively bind to GSK-3β and Nur77 to allow β-catenin to escape degradation, with consequent elevated levels of downstream oncogenic genes. In vivo, we consistently observed that NDRG1 suppression in HCC xenografts decreased β-catenin levels and its downstream target Cyclin D1, with concomitant tumor growth inhibition. Clinically, the over-expression of NDRG1 in HCC patient samples is positively correlated with GSK-3β-9ser (âRâ= 0.28, p = 0.01), Nur77 (âRâ= 0.42, p < 0.001), and β-catenin (âRâ= 0.32, p = 0.003) expressions. In conclusion, we identified GSK-3β and Nur77 as novel interaction partners of NDRG1. These protein-protein interactions regulate the turnover of β-catenin and subsequent downstream signaling mediated by β-catenin in HCC cells, and provides potential targets for future therapeutic interventions.
View details for PubMedID 26359353
Hepatocellular carcinoma (HCC) is the fifth most lethal malignancy worldwide with no curative therapies. To discover potentially novel therapeutic targets for HCC, we previously studied the gene expression profiles of HCC patients and identified that significant upregulation of N-Myc downstream regulated gene 1 (NDRG1) is associated with more aggressive phenotypes and poorer overall survival of HCC patients. In this study, we further used a loss-of-function approach (RNA interference) to understand the role of NDRG1 in hepatocarcinogenesis. We found that suppression of NDRG1 significantly impaired HCC cell growth through inducing extensive cellular senescence of HCC cells both in vitro and in vivo, accompanied by cell cycle arrest at the G1 phase. The observed antitumor effects of NDRG1 suppression were correlated with activation of major senescence-associated signaling pathways, such as upregulation of tumor suppressors p53, p21 and p16, and decreased phosphorylated Rb. To obtain further insights into the clinical significance of NDRG1-modulated senescence in HCC patients, immunohistochemistry staining of 92 cases of HCC patients was done. We found that high NDRG1 expression (n = 66) is associated with low p21 (n = 82; P < 0.001) and low p16 (n = 86; P < 0.001) levels. In conclusion, this study demonstrated that NDRG1 is a potential therapeutic target for HCC because its suppression triggers senescence of HCC cells through activating glycogen synthase kinase-3β-p53 pathway, thereby inhibiting tumor progression.
View details for DOI 10.1093/carcin/bgt401
View details for PubMedID 24302615
Stress protein mortalin (mtHSP70) is highly expressed in cancer cells. It was shown to contribute to carcinogenesis by sequestrating the wild type p53, a key tumor suppressor protein, in the cytoplasm resulting in an abrogation of its transcriptional activation function. We have found that the level of mortalin expression has significant correlation with human hepatocellular carcinoma (HCC) malignancy and therefore investigated whether it interacts with and influences the activities of mutant p53, frequently associated with HCC development. We have detected mortalin-p53 interactions in liver tumor and five HCC cell lines that harbored mutant p53. The data was in contrast to the normal liver and immortalized normal hepatocytes that lacked mortalin-p53 interaction. Furthermore, we have found that the shRNA-mediated mortalin silencing could induce mutant p53-mediated tumor-specific apoptosis in HCC. Such allotment of apoptotic function to mutant p53 by targeting mortalin-p53 interaction in cancer cells is a promising strategy for HCC therapy.
View details for DOI 10.1002/ijc.25857
View details for Web of Science ID 000294224300002
View details for PubMedID 21165951
Stress protein mortalin is a multifunctional protein and is highly expressed in cancers. It has been shown to interact with tumor suppressor protein-p53 (both wild and mutant types) and inactivates its transcriptional activation and apoptotic functions in cancer cells. In the present study, we found that, unlike most of the cancer cells, HepG2 hepatoma lacked mortalin-p53 interaction. We demonstrate that the mortalin-p53 interaction exists in cancer cells that are either physiologically stressed (frequently associated with p53 mutations) or treated with stress-inducing chemicals. Targeting mortalin-p53 interaction with either mortalin small hairpin RNA or a chemical or peptide inhibitor could induce p53-mediated tumor cell-specific apoptosis in hepatocellular carcinoma; p53-null hepatoma or normal hepatocytes remain unaffected.
View details for DOI 10.1038/cdd.2010.177
View details for Web of Science ID 000290379300013
View details for PubMedID 21233847
The intermediate filament nestin is transiently expressed in neural stem/progenitor cells during the development of central nervous system. Recently, increasing evidence has shown that upregulation of nestin is related to malignancy of several cancers, especially glioblastoma. However, the function of nestin in carcinogenesis remains unclear. In this study, we investigated the role of nestin in glioblastoma carcinogenesis by comparing subclones of rat C6 glioblastoma cells that were either high or low for nestin expression. We found that while nestin expression did not influence the in vitro proliferation of glioblastoma cells, subclones characterized by high levels of nestin formed tumors in vivo at significantly faster rates than subclones with low expression. Importantly, C6 subclones that expressed nestin at low levels in vitro were also found to give rise to tumors highly positive for the protein, suggesting that induction of nestin plays an important role in glioblastoma carcinogenesis. Derivation of nestin positive tumors from nestin negative human U87 glioblastoma cells in immunodeficient mice further confirmed that a switch to positive expression of nestin is fundamental to the course of glioblastoma development. Blocking the expression of nestin in glioblastoma tumors via intratumor injection of shRNA significantly slowed tumor growth and volume. These results demonstrated that nestin plays a crucial role in development of glioblastoma and may potentially be targeted for treatment of the disease.
View details for DOI 10.1002/ijc.25586
View details for Web of Science ID 000285263100010
View details for PubMedID 20669222
Heat shock proteins (HSPs) consist of a large group of proteins with negligible expressions under physiological conditions. Their expressions are highly induced under stress conditions and they are ubiquitously expressed in various tissues and organs. HSPs possess chaperone functions, thus facilitating the correct folding of proteins or peptides. In hepatocellular carcinoma (HCC), high expressions of HSPs are demonstrated in liver cancer tissues and are correlated clinically with the severity of tumors and poor outcomes of HCC patients. This property enables them to be used as diagnostic markers for the onset of HCC. Since their expressions are highly expressed in liver cancer conditions, inhibitors or antisense oligonucleotides of HSPs are postulated to serve as potential therapeutics in treating this liver malignancy. In this review, we will first introduce the HSP family and discuss the major signaling pathways involved for the activities of HSPs. In addition, the clinical applications of HSPs in liver cancer in the aspects of diagnosis and therapy will be summarized and discussed.
View details for Web of Science ID 000265799400009
View details for PubMedID 19442230
MicroRNAs (miRNAs) belong to a group of small non-coding RNA with differential expression in tumors, including hepatocellular carcinoma (HCC).This study investigates the involvement of miR-125b in HCC.Clinical analysis of miR-125b was performed using data derived from miRNA profiling and qPCR. Phenotypic changes of liver cell lines were examined after ectopic miR-125b expression. Lastly, bioinformatics analysis coupled with luciferase reporter assay was used to reveal the cellular target of miR-125b.A down-regulation of miR-125b was found in HCC tumors and cultured cells. Patients having tumors with ≥twofold reduction in miR-125b compared to adjacent non-tumor tissues contributed to 23 out of 49 HCC cases (46.9 %), while this down-regulation was usually found in patients with tumor venous infiltration and recurrence. miR-125b expression was also negatively correlated with increased serum AFP level and poor overall survival of patients. Ectopic expression of miR-125b led to alleviated tumor phenotypes of HCC cells. Among the 110 bioinformatically predicated candidates, 31 of them negatively correlated with miR-125b in HCC tumors for which one of them named eukaryotic translation initiation factor 5A2 (eIF5A2), known also as a liver oncofetal molecule, was validated to be a direct target of miR-125b in HCC.This study has evidenced for the negative correlation of tumor miR-125b expression with poor prognosis of HCC patients. Expression of miR-125b can reverse the tumorigenic properties of cultured HCC cells via suppressing the tumorigenic molecule eIF5A2, thus postulating restoration of miR-125b level as a way to counteract liver tumorigenesis.
View details for DOI 10.1007/s10620-014-3184-5
View details for Web of Science ID 000342148900017
View details for PubMedID 24811246
Mortalin is a member of Hsp70 family of stress chaperones. It was first identified as a protein involved in the senescence of mouse cells. Genetic studies revealed that there are two mouse mortalin alleles coding for two proteins (mot-1 and mot-2) that differ in only two amino acids in the carboxy-terminus, but have contrasting activities. Whereas mot-1 accelerated senescence, mot-2 extended the lifespan of mouse cells in culture. In human cells, only one kind of mortalin protein has been identified so far and is shown to be functionally equivalent to mouse mot-2. Whereas mortalin is enriched in cancer cells and contributes to carcinogenesis, the old age brain disorders show its deficiency. As we demystify its deux de machina, accumulating evidence reveal that mortalin may be "druggable" bidirectionally to either treat cancer or neuro-degenerative disorders.
View details for Web of Science ID 000316446800008
View details for PubMedID 22920904
Hepatocyte growth factor (HGF) and its receptor c-Met are widely expressed in the developing and adult brain. However, little is known about the role of HGF during the development of the human dopaminergic neuronal system. We have established telomerase-immortalized dopaminergic progenitor cells isolated from the fetal striatum that express markers for neural progenitor cells and tyrosine hydroxylase. We show that the cells were able to differentiate into dopaminergic neurons and release dopamine. Exogenous HGF-induced proliferation was inhibited by U0126, whereas migration was completely blocked by LY294002. Study demonstrates that HGF regulates the proliferation and migration of dopaminergic progenitor cells. Modulating dopaminergic progenitor cells in the striatum may prove to be a new approach for treating Parkinson's disease.
View details for Web of Science ID 000255530600012
View details for PubMedID 18418254