Induction of cell proliferation arrest and apoptosis in hepatoma cells through adenoviral-mediated transfer of p53 gene

Hepatitis B doubly spliced protein (HBDSP) promotes hepatocellular carcinoma cell apoptosis via ETS1/GATA2/YY1-mediated p53 transcription

IMPORTANCE

Hepatitis B virus (HBV) spliced variants are associated with viral persistence or pathogenicity. Hepatitis B doubly spliced protein (HBDSP), which has been previously reported as a pleiotropic transactivator protein, can potentially serve as an HBV virulence factor. However, the underlying mechanisms of HBDSP in HBV-associated liver diseases remain to be elucidated. In this study, we revealed that HBDSP promotes cellular apoptosis and induces wt-p53-dependent apoptotic signaling pathway in wt-p53 hepatocellular cells by transactivating p53 transcription, and increases the release of HBV progeny. Therefore, HBDSP may promote the HBV particles release through wt-p53-dependent hepatocellular apoptosis. Our findings suggest that blocking HBDSP-induced wt-p53-dependent apoptosis might have therapeutic values for chronic hepatitis B.

Influence of P53 on the radiotherapy response of hepatocellular carcinoma

Background/Aims

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and it has a poor prognosis and few therapeutic options. Radiotherapy is one of the most effective forms of cancer treatment, and P53 protein is one of the key molecules determining how a cell responds to radiotherapy. The aim of this study was to determine the therapeutic efficacy of iodine-131 in three human HCC cell lines.

Methods

Western blotting was used to measure P53 expression. The effects of radiotherapy with iodine-131 were assessed by using the clonogenic assay to evaluate cell survival. Flow cytometry was carried out to examine the effects of iodine-131 on cell death, oxidative stress, reduced intracellular glutathione expression, the mitochondrial membrane potential, and the cell cycle.

Results

The P53 protein was not expressed in Hep3B2.1-7 cells, was expressed at normal levels in HepG2 cells, and was overexpressed in HuH7 cells. P53 expression in the HuH7 and HepG2 cell lines increased after internal and external irradiation with iodine-131. Irradiation induced a decrease in cell survival and led to a decrease in cell viability in all of the cell lines studied, accompanied by cell death via late apoptosis/necrosis and necrosis. Irradiation with 131-iodine induced mostly cell-cycle arrest in the G0/G1 phase.

Conclusions

These results suggest that P53 plays a key role in the radiotherapy response of HCC.

New progress of non-surgical treatments for hepatocellular carcinoma

Many non-surgical treatments of hepatocellular carcinoma (HCC) have significantly improved in the last few decades and have shown survival benefits for selected patients with HCC. Today ablation can improve survival in individuals diagnosed in early HCC and even offer a curative treatment in selected candidates. Patients with intermediate-stage HCC benefit from transarterial chemoembolization (TACE). Drug-eluting bead transarterial chemoembolization (DEB-TACE) has shown a better combined ischemic and cytotoxic effect locally and less system toxicity when compared with conventional TACE. Those diagnosed at advanced stage benefit from sorafenib. In addition to TACE and sorafenib which could improve survival for selected patients, three-dimensional conformal radiotherapy treatment (3-DCRT), selection internal radiation therapy and systemic chemotherapy have also shown anti-tumor activity in the treatment of advanced HCC, but their survival benefit have not been proven. The limited effects of single therapy suggested that the combination would enhance the overall treatment effect. Other potential non-surgical therapies like gene therapy and immunotherapy are still in testing phases, except for some small-scale clinical trials which have been reported to show some beneficial effect. Here, we review the current non-surgical treatments in HCC and the new advances in this field.

Increased expression of p53 enhances transcription-coupled repair and global genomic repair of a UVC-damaged reporter gene in human cells

Ultraviolet (UV) light-induced DNA damage is repaired by nucleotide excision repair, which is divided into two sub-pathways: global genome repair (GGR) and transcription-coupled repair (TCR). While it is well established that the GGR pathway is dependent on the p53 tumour suppressor protein in human cells, both p53-dependent and p53-independent pathways have been reported for TCR. In the present work, we investigated the role of p53 in both GGR and TCR of a UVC-damaged reporter gene in human fibroblasts. We employed a non-replicating recombinant human adenovirus, AdCA17lacZ, that can efficiently infect human fibroblasts and express the beta-galactosidase (beta-gal) reporter gene under the control of the human cytomegalovirus promoter. We examined host cell reactivation (HCR) of beta-gal expression for the UVC-treated reporter construct in normal fibroblasts and in xeroderma pigmentosum (XP) and Cockayne syndrome (CS) fibroblasts deficient in GGR, TCR, or both. HCR was examined in fibroblasts that had been pre-infected with Ad5p53wt, which expresses wild-type p53, or a control adenovirus, AdCA18luc, which expresses the luciferase gene. We show that increased expression of p53 results in enhanced HCR of the UVC-damaged reporter gene in both untreated and UVC-treated cells for normal, CS-B (TCR-deficient), and XP-C (GGR-deficient), but not XP-A (TCR- and GGR-deficient) fibroblasts. These results indicate an involvement of p53 in both TCR and GGR of the UV-damaged reporter gene in human cells.

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Establishment of a doxycycline-regulated cell line with inducible, doubly-stable expression of the wild-type p53 gene from p53-deleted hepatocellular carcinoma cells

p53 is important in the development of hepatocellular carcinoma (HCC) and in therapeutic approaches, but the mechanism whereby it inhibits HCC growth is still unclear. The aim of the present study was to establish a HCC cell system in which p53 levels can be regulated. Full-length wild-type p53 cDNA obtained by PCR was cloned into a retroviral response vector controlled by the tetracycline responsive element (RevTRE-p53). The regulatory vectors RevTet-Off and RevTRE-p53 were transfected into a packaging cell line, PT67. Hep3B cells in which the p53 gene was deleted were infected with RevTet-Off viral particles from the PT67. Three G418-resistant cell clones with high luciferase expression and low background were infected with RevTRE-p53. By screening dozens of RevTRE-p53-infected clones with hygromycin we identified the one with the highest expression of p53 and the lowest background after doxycycline treatment. The results showed that p53 expression in this cell clone could be simply turned on or off by removing or adding doxycycline. Furthermore, it was found that the level of p53 protein was negatively and sensitively related to the doxycycline concentration. In conclusion, we have established a HCC cell line in which p53 expression can be switched on or off and regulated in a dose- and time-dependent manner.

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Adenoviral-mediated transfer of p53 or retinoblastoma protein blocks cell proliferation and induces apoptosis in culture-activated hepatic stellate cells

BACKGROUND/AIMS

The principal cellular effectors of fibrosis in liver are hepatic stellate cells (HSC). In response to liver injury these quiescent cells undergo a phenotypic change to a myofibroblastic cell type, proliferate and secrete matrix components. Thus, removal of activated HSC should be beneficial for the prognosis of hepatic fibrogenesis and preserve organ function.

METHODS

The purpose of this study was to investigate whether administration of adenoviruses constitutively expressing the p53 tumor suppressor or the retinoblastoma protein (pRb) is sufficient to induce cell arrest or apoptosis in culture-activated HSC. The expression of the transgenes was confirmed by Western blot analysis and immunohistochemistry.

RESULTS

Both proteins were expressed mainly in the nucleus and their expression was associated with a marked inhibition of cell proliferation and induction of apoptosis as determined by measurement of phosphatidylserine exposed at the surface, proliferation assay, induction of the p21 cyclin-dependent kinase inhibitor, and an increase of caspase-3 activity. Additionally, electron microscopic analysis confirmed that activation of the p53-mediated pathway in HSC results in chromatin and cytoplasmic condensation, typical features of ongoing apoptosis.

CONCLUSIONS

Our results indicate that transduction of p53 or pRb offers a feasible approach to induce apoptosis in activated HSC. Thus, targeted transfer of these proteins into HSC may be potentially useful for the treatment of hepatic fibrosis.

Intra-arterial delivery of a recombinant adenovirus does not increase gene transfer to tumor cells in a rat model of metastatic colorectal carcinoma

Hepatic artery infusion of adenoviral vectors has been shown to increase transduction of certain hepatocellular malignancies in preclinical studies. In addition, clinical trials have begun evaluating the efficacy of gene transfer of cytotoxic genes to metastatic colorectal tumors through hepatic artery infusion. Here we evaluate the extent of gene expression and therapeutic effect following various routes of administration of recombinant adenovirus in a rat model of metastatic colorectal carcinoma. We administered adenovirus (AdCMVlacZ) to rats with established colorectal metastases through infusion into the hepatic artery, intravenous infusion, or direct injection into a tumor. Intravenous administration resulted in transduction of hepatocytes, but not tumor cells. Hepatic arterial administration failed to substantially increase transduction of tumor cells. In addition, ligation of the hepatic artery following infusion of adenovirus or the addition of lipiodol infusion had no effect on the transduction of tumor cells. We administered AdCMVp53 by direct injection into tumors, intravenous administration, or hepatic artery infusion to evaluate the delivery of a therapeutic gene. Direct injection of AdCMVp53 into established hepatic colorectal metastases resulted in a therapeutic response in comparison with both hepatic arterial and intravenous infusion of vector. These preclinical studies fail to support a strategy of infusion through the hepatic artery of recombinant adenovirus targeting tumor cells in the treatment of colorectal cancer liver metastases.