Requirement of cyclin-dependent kinase function for hepatitis B virus cccDNA synthesis as measured by digital PCR

INTRODUCTION AND OBJECTIVES

HBV covalently closed circular (ccc) DNA is the key player in viral persistence and an important predictive biomarker for hepatitis relapse. Precise quantification of intracellular cccDNA is challenging because cccDNA is present in very low levels in hepatocytes, where it also co-exists with a large excess amount of relaxed circular (rc) DNA. We aimed to develop a highly sensitive cccDNA detection method for cccDNA quantification by digital PCR (dPCR).

PATIENTS OR MATERIALS AND METHODS

A standard plasmid containing the whole HBV genome in the closed circular conformation was employed to characterize the performance of dPCR. rcDNA in the growth medium of HBV-producing HepAD38 cells was used as a matrix for cccDNA detection. Intrahepatic cccDNA measurement by dPCR and qPCR was performed to determine the correlation of the analysis results for the two methods.

RESULTS

The limit of detection (LOD) of the cccDNA dPCR was 1.05copy/μl, and the linear range of detection was 1.02×10⁴copies/μl, achieving a dynamic detection range of 10⁴-fold. cccDNA measurement using excess rcDNA as the matrix did not reveal false-positive detection, indicating that dPCR was highly specific. In the HepAD38 cells, the cccDNA levels measured by dPCR were highly correlated with those measured by qPCR but had a higher sensitivity. The CDK inhibitor AZD-5438 was found to block intracellular cccDNA synthesis.

CONCLUSIONS

Dpcr greatly improved the sensitivity and specificity of cccDNA detection. Host CDK activities are likely required for cccDNA synthesis. dPCR can potentially be applied for drug screening for effective cccDNA inhibitors.

NEK2 Promotes Hepatoma Metastasis and Serves as Biomarker for High Recurrence Risk after Hepatic Resection

INTRODUCTION AND AIM

Developing reliable biomarkers for hepatocellular carcinoma (HCC) patients who are at a high risk of recurrence after curative hepatic resection is very important for determining subsequent therapeutic strategies. We investigated the role of the cell cycle factor NIMA-related kinase 2 (NEK2) in HCC progression in hepatoma cells and post-surgery patients.

MATERIAL AND METHODS

The effects of NEK2 on proliferation, invasion and migration of hepatoma HuH7 and SK-Hep1 cells were evaluated. In a post-surgery HCC cohort (N = 97), the Nek2 induction levels in the tumors were examined with real-time RT-PCR analysis, and the results were analyzed for their correlations with recurrence.

RESULTS

NEK2 promoted G1 to S phase cell cycle progression by causing increases in cyclin D1 and AKT phosphorylation and decreases in the cyclin-dependent kinase inhibitor p27, indicating that NEK2 plays an important role during interphase in addition to its previously identified role in M phase. NEK2 also enhanced the proliferation, migration and invasion of hepatoma cells and regulated the expression of E-cadherin and MMP9. The Nek2 mRNA levels in the tumors were highly correlated with recurrence rates in the post-surgery HCC patients. Combined evaluation of the tumor AJCC stage and the Nek2 level can serve as a reliable method for predicting the relative risk of HCC recurrence in these patients.

CONCLUSIONS

NEK2 plays a significant role in cell cycle progression in the inter- and M-phases. NEK2 enhances HCC metastasis and is correlated with recurrence and thus can potentially serve a promising high-risk biomarker for HCC.

Promotion of peri-implant bone healing by systemically administered parathyroid hormone (1-34) and zoledronic acid adsorbed onto the implant surface

The effect of human parathyroid hormone 1-34 (PTH) and zoledronic acid (ZA) alone or in combination on bone healing in osteoporotic settings was tested using implants inserted in tibiae of ovariectomized (OVX) rats. Combination therapy promoted bone healing more than each treatment alone 12 weeks after implant insertion.

INTRODUCTION

PTH and ZA have been demonstrated to be effective on implant fixation. However, reports about the combined use of PTH and ZA for promotion of bone healing around implant in osteoporotic settings are still limited. This study aims to investigate effects of PTH+ZA on implant stabilization in OVX rats.

METHODS

Twelve weeks after bilateral ovariectomy, OVX rats randomly received implants without or with ZA (by immersion in 1 mg/ml ZA solution for 24 h). Subsequently, half of the animals from each group also received subcutaneous injections of PTH (60 μg/kg, three times a week) for 12 weeks. Thus, there were four groups: control, PTH, ZA, and PTH+ZA.

RESULTS

All treatments promoted bone healing around implant compared to control, but PTH+ZA treatment showed significantly stronger effects than PTH or ZA alone in histological, micro-CT, and biomechanical tests.

CONCLUSION

The results indicated the additive effects of PTH and ZA on implant fixation in OVX rats; it was suggested that the anabolic effect of PTH was potent and not blunted by ZA during bone healing around implant when used concurrently.

The effect of surface composition of titanium films on bacterial adhesion

We show that bacterial adhesion on titanium (Ti) films could be radically minimized by tailoring the surface chemical stoichiometry of the films. Using a dc magnetron sputtering system, Ti films with various surface compositions, such as oxide and nitride combinations, were prepared by controlling processing parameters such as cathode power, sputtering pressure and base vacuum. The surface topography of the films was observed to be smooth and similar in all the films prepared under different conditions. The order of adhesion of the oral bacterial Porphyromonas gingivalis varied with the surface chemical stoichiometry of the Ti films. Few surface stoichiometries of typical oxide nitride combination resulted in nearly nil bacterial adhesion.

Molecular analysis of hypoxanthine phosphoribosyltransferase gene deletions induced by alpha- and X-radiation in human lymphoblastoid cells

Mutations caused by exposure to X-radiation and to radon and its decay products were compared in the hprt gene of a human lymphoblastoid cell line. Thirty-one X-radiation-induced, 29 radon-induced, and 24 spontaneous mutants were recovered from cell cultures under identical conditions except for the exposure to radiation. Seven spontaneous point mutations were recovered and DNA sequenced. These mutations included three C:G-->T:A transitions. These spontaneous point mutations were located in the exon or splice donor regions of five of the nine hprt exons. Four X-radiation-induced and three radon-induced point mutations were also analyzed by DNA sequencing. The frequency of induced mutants at the D0 doses for radon and X-radiation respectively were 5 x 10(-6) and 4.5 x 10(-6). Deletions were the predominant mutations recovered from both radon- and X-irradiated cells. Eighty-one percent of the mutants from X-radiation-treated cultures, 86% of the radon-treated cultures, and 63% of the spontaneous mutants involved deletions. Deletions involving exon and intron DNA, as well as intron DNA alone, were found to inactivate the hprt gene and result in a selectable HPRT- phenotype. Among the deletion mutants, however, only 21% of the spontaneous mutants versus 55% of both the X-radiation- and radon-induced mutants exhibited loss of the entire hprt gene. More X-radiation-induced deletions than radon-induced deletions extended further than 800 bp in the telomeric direction from the hprt gene (six of 17 versus two of 17). The results show that at the human hprt locus of TK-6 cells the predominant kind of mutation indicative of exposure to both high LET alpha-radiation and low LET X-radiation is a large deletion, spanning the entire hemizygous hprt gene and extending into flanking sequences.

Sequencing of double-stranded polymerase chain reaction products for mutation analysis

This report describes a reproducible, straightforward approach to sequencing double-stranded DNA products from the polymerase chain reaction (PCR) for analysis of mutations. The sequencing protocol is a modification of that published by Kretz (Kretz et al., 1989) and has been successful in the hands of a number of investigators working on diverse projects. Following this procedure, PCR DNA products generated from bacterial sources (including pBR322 and F' derivatives), as well as cDNA and genomic DNA from both hamster and human cell lines, have been sequenced with equal success. Close attention to the molar ratio of nucleotides to double-stranded DNA template present during the labeling reaction ensures best results.

[Interceptive activity of epostane in pregnant rats and rhesus monkeys]

A complete interceptive action on pregnancy was shown after ig epostane (Epo) 48 and 96 mg/kg on d 10 of pregnancy in rats. ED50 (95% fiducial limits) of Epo was 20.7 (16.3-26.3) mg/kg. Epo 48 mg/kg ig on d12, 14 and 16 of pregnancy lowered rat plasma progesterone concentrations (P less than 0.05) and plasma corticosterone on d 16 of pregnancy (P less than 0.05). Epo 35 mg/(kg.d) was given ig on d 50-54 of pregnancy in rhesus monkeys. Vaginal bleeding was seen in all of the 6 treated monkeys. Complete expulsions of fetal and placental materials occurred in 5 of the treated monkeys, among which 2 aborted on d 53 and the other 3 on d 54 of pregnancy. Plasma progesterone concentrations of the treated monkeys were lowered on d 52, 53 and 54 of pregnancy (P less than 0.05) and plasma estradiol on d 51, 52, 53, 54 and 55 (P less than 0.05), while there were no significant differences in plasma hydrocortisone. Epo may be a valuable supplement to the existing methods of female contraception.

Effects of forelimb amputation and denervation on protein synthesis in spinal cord ganglia of the newt

Analysis of the effects of forelimb amputation and denervation on [35S]methionine incorporation into the protein of newt brachial plexus nerve ganglia showed that amputation increases the level of protein synthesis about 4-fold as compared with that of control (nonamputated) animals. Denervation without amputation nearly doubles the level of protein synthesis as compared with controls. Analysis of labeled protein by means of two-dimensional gel electrophoresis and radioautogram revealed incorporation patterns that are similar to controls; this observation suggests that amputation affects nerve cells quantitatively rather than qualitatively, in influencing the production of putative neurotrophic agents. A group of basic proteins ranging in Mr from 15,000 to 31,000 are prominently expressed in these radioautograms from experimental ganglia and may be important in promoting forelimb regeneration in the newt.