Real-time quantification of human telomerase reverse transcriptase mRNA in liver tissues from patients with hepatocellular cancer and chronic viral hepatitis

Adipose Tissue-Derived Extracellular Vesicles and the Tumor Microenvironment: Revisiting the Hallmarks of Cancer

Extracellular vesicles (EVs) are crucial elements that sustain the communication between tumor cells and their microenvironment, and have emerged as a widespread mechanism of tumor formation and metastasis. In obesity, the adipose tissue becomes hypertrophic and hyperplastic, triggering increased production of pro-inflammatory adipokines, such as tumor necrosis factor α, interleukin 6, interleukin 1, and leptin. Furthermore, obese adipose tissue undergoes dysregulation in the cargo content of the released EVs, resulting in an increased content of pro-inflammatory proteins, fatty acids, and oncogenic microRNAs. These alterations drive obesity-associated inflammatory responses both locally and systemically. After being ignored for a long time, adipose tissues have recently received considerable attention as a major player in tumor microenvironment-linked obesity and cancer. The role of adipose tissue in the establishment and progression of cancer is reinforced by its high plasticity and inflammatory content. Such a relationship may be established by direct contact between adipocytes and cancer cells within the microenvironment or systemically, via EV-mediated cell-to-cell communication. Here, we highlight cues evidencing the influence of adipose tissue-derived EVs on the hallmarks of cancer, which are critical for tumor malignancy.

JAK/STAT3 signaling regulates human telomerase reverse transcriptase via Leptin in hepatoma cells

AIM: To explore the influence of Leptin mediated JAK/STAT3 signaling on human telomerase reverse transcriptase (hTERT) in human liver cancer cells (HepG2) and elucidate the molecular mechanisms by which Leptin induces hTERT expression in hepatocellular carcinoma cells.

METHODS: The expression of ob-R in HepG2 cells was determined by Western blot. The expression of hTERT protein in cells after treatment with AG490 inhibitor was also detected by Western blot. Cell proliferation was detected by MTT method. The expression of hTERT mRNA was tested by RT-PCR, and the expression of hTERT protein was tested by Western blot.

RESULTS: HepG2 cells expressed ob-R. Western blot analysis showed that the hTERT protein expression in AG490 treatment group and AG490 plus Leptin treatment group was lower than that of Leptin treatment group. HepG2 cell proliferation was reduced after STAT3-siRNA transfection. The expression of hTERT protein and hTERT mRNA was reduced in STAT3-siRNA transfected HepG2 cells after treatment with STAT3 inhibitor.

CONCLUSION: HepG2 cells express ob-R. Leptin induced JAK-STAT3 signaling downregulates the hTERT mRNA and protein expression in hepatocellular carcinoma cells.

Promoter hypermethylation of TERT is associated with hepatocellular carcinoma in the Han Chinese population

BACKGROUND

Upstream of the transcription start site (UTSS), hypermethylation of the telomerase reverse transcriptase (TERT) gene has been shown to be associated with tumour progression and a poor prognosis in paediatric brain tumours (Castelo-Branco 2013). It has been inferred that the UTSS region of TERT is a potentially accessible biomarker for various cancers. In this study, we aimed to explore the role of TERT in hepatocellular carcinoma (HCC) and to investigate whether the UTSS region of the TERT promoter shows the same methylation pattern in HCC.

METHODS

We analysed the results of a methylation assay for TERT, including the UTSS region, from 125 paired HCC samples using Mass Array EpiTyper (Sequenom, San Diego, CA, USA). To determine the relationship between TERT promoter methylation status and the TERT expression level, we analysed a validation group of 12 paired HCC samples and acquired the FPKM values for the TERT gene.

RESULTS

Our results showed aberrant methylation of the UTSS region of the TERT promoter in HCC (mean=15.1) compared with the adjacent normal tissues (mean=6.1, P<0.00001). Furthermore, a nearly 56-fold increase in TERT expression from the hypermethylated promoter was found in HCC (P<0.05), indicating a positive relationship between TERT methylation and expression.

CONCLUSIONS

As hypermethylation was positively correlated with high expression of TERT in HCC, TERT is likely to be involved in the aetiology of HCC. Our findings indicate that future studies on TERT might be fruitful.

Leptin as a critical regulator of hepatocellular carcinoma development through modulation of human telomerase reverse transcriptase

Background

Numerous epidemiological studies have documented that obesity is associated with hepatocellular carcinoma (HCC). The aim of this study was to investigate the biological actions regulated by leptin, the obesity biomarker molecule, and its receptors in HCC and the correlation between leptin and human telomerase reverse transcriptase (hTERT), a known mediator of cellular immortalization.

Methods

We investigated the relationship between leptin, leptin receptors and hTERT mRNA expression in HCC and healthy liver tissue samples. In HepG2 cells, chromatin immunoprecipitation assay was used to study signal transducer and activator of transcription-3 (STAT3) and myc/mad/max transcription factors downstream of leptin which could be responsible for hTERT regulation. Flow cytometry was used for evaluation of cell cycle modifications and MMP1, 9 and 13 expression after treatment of HepG2 cells with leptin. Blocking of leptin's expression was achieved using siRNA against leptin and transfection with liposomes.

Results

We showed, for the first time, that leptin's expression is highly correlated with hTERT expression levels in HCC liver tissues. We also demonstrated in HepG2 cells that leptin-induced up-regulation of hTERT and TA was mediated through binding of STAT3 and Myc/Max/Mad network proteins on hTERT promoter. We also found that leptin could affect hepatocellular carcinoma progression and invasion through its interaction with cytokines and matrix mettaloproteinases (MMPs) in the tumorigenic microenvironment. Furthermore, we showed that histone modification contributes to leptin's gene regulation in HCC.

Conclusions

We propose that leptin is a key regulator of the malignant properties of hepatocellular carcinoma cells through modulation of hTERT, a critical player of oncogenesis.

Hepatocellular carcinoma: prevalence and molecular pathogenesis of Helicobacter spp

Helicobacter pylori infection is one of the most common chronic bacterial infections in humans. The association of other Helicobacter spp. with extragastric diseases in animals is well established, and a role of these bacteria in human liver disease is becoming clearer. Several case-control studies have reported possible associations of Helicobacter spp. with various liver diseases, including hepatocellular carcinoma, which is the fifth most common type of carcinoma among men worldwide, and the eighth most common among women. Thus, it is important to understand molecular mechanisms that may lead to hepatotoxicity or hepatocellular dysfunction in which Helicobacter spp. may play a role in inducing malignant transformation of liver cells.

Expression alteration of tankyrase and telomerase in HCC development in rats

AIM: To explore the dynamic states of and relationship between tankyrase and telomerase reverse transcriptase (TERT) in hepatocellular carcinoma (HCC) development in rats.

METHODS: SD rats were assigned randomly to control group (n = 42) and model group (n = 42). HCC model was induced by diethyl nitrosoamine (DENA). Twelve rats from both groups were randomly executed at 3, 6, 9, 12, 15, 18, 21 wk for further test. The expression of tankyrase and TERT was detected using Western blot and immunofluorescence analysis, whereas telomerase activity and the expression of Ki-67 were assayed using TRAP and immunohistochemical methods, respectively.

RESULTS: Compared with the low expression level of telomerase and TERT in normal tissue and precancerous lesions, the expression level of tankyrase was significantly increased in inflammatory stage, as well as in hepatocirrhotic stage, especially in HCC stage, in which stage peak values of all these factors were obtained . The expression of tankyrase was positively correlated with telomerase and TERT (r = 0.898, P = 0.038; r = 0.943, P = 0.016), but no relationship was found between tankyrase and Ki-67. However, Ki-67 was positively correlated with telomerase and TERT (r = 0.986, P = 0.002; r = 0.93, P = 0.022).

CONCLUSION: Over-expression of tankyrase might be one of the factors that regulates telomerase function as telomere elongation. Tankyrase, TERT, telomerase and Ki-67 are closely related to HCC progression.

Experimental models of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common and deadly cancer whose pathogenesis is incompletely understood. Comparative genomic studies from human HCC samples have classified HCCs into different molecular subgroups; yet, the unifying feature of this tumor is its propensity to arise upon a background of inflammation and fibrosis. This review seeks to analyze the available experimental models in HCC research and to correlate data from human populations with them in order to consolidate our efforts to date, as it is increasingly clear that different models will be required to mimic different subclasses of the neoplasm. These models will be instrumental in the evaluation of compounds targeting specific molecular pathways in future preclinical studies.