Growth inhibition of BEL-7404 human hepatoma cells by expression of mutant telomerase reverse transcriptase

Clinical implications of antitelomeric drugs with respect to the nontelomeric functions of telomerase in cancer

Telomerase is responsible for maintaining the length of telomeres at the ends of chromosomes. Although most somatic cells do not exhibit telomerase activity, it is reactivated in approximately 85% of cancers. This simple and attractive phenomenon steers the development of anticancer drugs targeting telomeres and telomerase. Recent studies have been revealing extratelomeric roles of telomerase in normal tissues, affecting processes that are critical for survival and aging of organisms. In this review, we will discuss the current therapeutic strategies targeting telomeres and telomerase and evaluate their potential advantages and risks with respect to nontelomeric functions.

Label-free electrochemical impedance spectroscopy biosensor for direct detection of cancer cells based on the interaction between carbohydrate and lectin

A novel label-free electrochemical impedance spectroscopy (EIS) biosensor for direct cancer cell detection based on the interaction between carbohydrate and lectin has been developed with good sensitivity and selectivity. In the present work, concanavalin A (Con A), a mannose specific lectin, was immobilized on a gold disk electrode to fabricate the Con A sensor. This sensor was incubated with the cancer cell sample, and the binding of cancer cells with Con A resulted in a change of charge transfer resistance (Rct). EIS measurement was employed to measure the impedance change which reveals the concentration of cancer cells. This method has been successfully applied in human liver cancer cell Bel-7404 for direct and sensitive detection with a detection limit of 234cells/mL. This method could be extended to carry out multi-component diagnosis applications, thus providing enormous potential for applications of cancer monitoring and therapy.

The Molecular Diagnosis of Hepatitis B Virus-Associated Hepatocellular Carcinoma

Hepatitis B virus (HBV) infection is the major cause of hepatocellular carcinoma (HCC) worldwide. The pathogenesis of HBV-associated HCC has been studied extensively, and molecular changes during malignant transformation have been identified. It has been proposed that the insertion of HBV DNA into the human genome results in chromosomal instability and inactivation of tumor suppressor genes. Transactivation of oncogenes, inactivation of tumor suppressor genes, and alteration of the cell cycle by HBV proteins are also involved in the progression of hepatocellular carcinogenesis. Traditional clinical examinations of HCC, such as biopsy, computer tomography, ultrasonic imaging, and detection of such biomarkers as a-fetoprotein, are currently the "gold standard" in diagnosis. These tests diagnose HCC only in the late stages of disease. This limitation has greatly reduced the chance of survival of HCC patients. To resolve this problem, new biomarkers that can diagnose HCC in earlier stages are necessary. Based on recent molecular studies of the effects of HBV on cellular transformation, differentially expressed biomarkers of HBV infection have been elucidated. With the analyses of the HBV replication profile, the viral load (HBV DNA levels) of patients, and the viral protein expression, the severity of hepatitis in the preneoplastic stages can be assessed. In the future, with the molecular profiles identified by genomic and proteomic approaches, stage-specific biomarkers should be identified to monitor the progression and prognosis of HCC.

Telomeres and telomerase: a dual role in hepatocarcinogenesis

Telomere shortening limits the proliferative capacity of primary human cells and restrains the regenerative capacity of organ systems during chronic diseases and aging. Telomere shortening apparently has a dual role in tumor development and progression. On the one hand, it induces chromosomal instability and the initiation of cancer; on the other hand, tumor progression requires stabilization of telomeres. The predominant mechanism of telomere stabilization in tumor cells is the activation of the telomere-synthesizing enzyme telomerase. The potential use of telomerase activators for the treatment of regenerative disorders will ultimately depend on their effects on tumorigenesis. This review focuses on the role of telomere shortening and telomerase in carcinogenesis with a special focus on hepatocellular carcinoma.

Antisense oligonucleotide targeting at the initiator of hTERT arrests growth of hepatoma cells

AIM: To evaluate the inhibitory effect of antisense phosphorothioate oligonucleotide (asON) complementary to the initiator of human telomerase catalytic subunit (hTERT) on the growth of hepatoma cells.

METHODS: The as-hTERT was synthesized by using a DNA synthesizer. HepG2.2.15 cells were treated with as-hTERT at the concentration of 10 μmol/L. After 72 h, these cells were obtained for detecting growth inhibition, telomerase activity using the methods of MTT, TRAP-PCR-ELISA, respectively. BALB/c(nu/nu) mice were injected HepG2.2.15 cells and a human-nude mice model was obtained. There were three groups for anti-tumor activity study. Once tumors were established, these animals in the first group were administered as-hTERT and saline. Apoptosis of tumor cells was detected by FCM. In the 2nd group, the animals were injected HepG2.2.15 cells together with as-hTERT. In the third group, the animals were given as-hTERT 24 hours postinjection of HepG2.2.15 cells. The anti-HBV effects were assayed with ELISA in vitro and in vivo.

RESULTS: Growth inhibition was observed in cells treated with as-hTERT in vitro. A significant different in the value of A₅₇₀ - A₆₃₀ was found between cells treated with as-hTERT and control (P < 0.01) by MTT method. The telomerase activity of tumor cells treated with as-hTERT was reduced, the value of A₄₅₀ nm was 0.42 compared to control (1.49) with TRAP-PCR-ELISA. The peak of apoptosis in tumor cells given as-hTERT was 21.12%, but not seen in saline-treated control. A prolonged period of carcinogenesis was observed in the second and third group animals. There was inhibitory effect on the expression of HBsAg and HBeAg in vivo and in vitro.

CONCLUSION: As-hTERT has an anti-tumor activity, which may be useful for gene therapy of tumors.

Telomerase inhibition and telomere loss in BEL-7404 human hepatoma cells treated with doxorubicin

AIM: To study the effects of doxorubicin on telomerase activity and telomere length in hepatocellular carcinoma.

METHODS: Telomerase activity was assayed with a non-radioisotopic quantitative telomerase repeat amplification protocal-based method. The effect of doxorubicin (DOX) on the growth of BEL-7404 human hepatoma cells was determined by microculture tetrazolium assay. Mean telomere length (terminal restriction fragment) was detected by Southern blot method. The expression of telomerase subunits genes was investigated by RT-PCR. Cell apoptosis and cell cycle distribution were evaluated by flow cytometry.

RESULTS: Telomerase activity was inhibited in a dose and time-dependent manner in BEL-7404 human hepatoma cells treated with DOX for 24, 48 or 72 h in concentrations from 0.156 to 2.5 μM which was crrelated with the inhibition of cell growth. No changes were found in the mRNA expression of three telomerase subunits (hTERT, hTR and TP1) after drug exposure for 72 h with indicated concentrations. The cells treated with DOX showed shortened mean telomere length and accumulated at the G₂/M phase. However, there was almost no effects on cell apoptosis by DOX.

CONCLUSION: The telomerase inhibition and the telomere shortening by DOX may contribute to its efficiency in the treatment in hepatocellular carcinoma.

Study of apoptosis in human liver cancers

AIM: To investigate the action of apoptosis in occurrence of liver cacinomas in vivo and the biological effect of Solanum lyratum Thumb on BEL-7404 cell line inducing apoptosis in vitro.

METHODS: The apoptosis in the liver carcinoma was detected with terminal deoxynucl neotidyl transferase mediated dUTP nick end labelling (TUNEL); the cancer cells cultured in DMED medium were treated with extract of Solanum lyratum Thumb and observed under microscope, and their DNA was assayed by gel electrophoresis.

RESULTS: In vivo apoptotic cells in the cancer adjacent tissues inceased; in vitro treatment of liver cancers with extract of Solanum lyratum Thumb could induce the cells to manifest a typical apoptotic morphology. Their DNA was fractured and a characteristic ladder pattern could be found using electrophoresis.

CONCLUSION: In vivo the apoptosis of carcinomas was lower; maybe the cells divided quickly and then the cancers occurred. In the cancer adjacent tissues, the apoptosis pricked up, and in vitro Solanum lyratum Thumb could induce the apoptosis of BEL-7404 cells.

Effects of cisplatin on telomerase activity and telomere length in BEL-7404 human hepatoma cells

Telomerase activity was inhibited in a dose and time-dependent manner with the treatment of cisplatin for 24, 48, or 72 h in a concentration ranged from 0.8 to 50 microM in BEL-7404 human hepatoma cells. There were no changes in expression pattern of three telomerase subunits, its catalytic reverse transcriptase subunit (hTERT), its RNA component (hTR) or the associated protein subunit (TP1), after cisplatin treated for 72 h with indicated concentrations. Mean telomere lengths were decreased by the cisplatin treatment. Cell growth inhibition and cell cycle accumulation in G2/M phase were found to be correlated with telomerase inhibition in the present study, but percentages of cell apoptosis did not change markedly during the process.