Systematic analysis of DNA polymerases as therapeutic targets in pan-cancers

Introduction:DNA polymerases are crucial for maintaining genome stability and influencing tumorigenesis.However,the clinical implications of DNA polymerases in tumorigenesis and their potential as anti-cancer therapy targets are not well understood.Methods:We conducted a systematic analysis using TCGA Pan-Cancer Atlas data and Gene Set Cancer Analysis results to examine the expression profiles of 15 DNA polymerases(POLYs)and their clinical correlations.We also evaluated the prognostic value of POLYs by analyzing their expression levels in relation to overall survival time(OS)using Kaplan-Meier survival curves.Additionally,we investigated the correlations between POLY expression and immune cells,DNA damage repair(DDR)pathways,and ubiquitination.Drug sensitivity analysis was performed to assess the relationship between POLY expression and drug response.Results:Our analysis revealed that 14 out of 15 POLYs exhibited significantly distinct expression patterns between tumor and normal samples across most cancer types,except for DNA nucleotidylexotransferase(DNTT).Specifically,POLD1 and POLE showed elevated expression in almost all cancers,while POLQ exhibited high expression levels in all cancer types.Some POLYs showed heightened expression in specific cancer subtypes,while others exhibited low expression.Kaplan-Meier survival curves demonstrated significant prognostic value of POLYs in multiple cancers,including PAAD,KIRC,and ACC.Cox analysis further validated these findings.Alteration patterns of POLYs varied significantly among different cancer types and were associated with poorer survival outcomes.Significant correlations were observed between the expression of POLY members and immune cells,DDR pathways,and ubiquitination.Drug sensitivity analysis indicated an inverse relationship between POLY expression and drug response.Conclusion:Our comprehensive study highlights the significant role of POLYs in cancer development and identifies them as promising prognostic and immunological biomarkers for various cancer types.Additionally,targeting POLYs therapeutically holds promise for tumor immunotherapy.

Low testing rates and high BRCA prevalence: Poly (ADP-ribose) polymerase inhibitor use in Middle East BRCA/homologous recombination deficiency-positive cancer patients

BACKGROUND Poly(ADP-ribose)polymerase inhibitors(PARPis)are approved as first-line therapies for breast cancer gene(BRCA)-positive,human epidermal growth factor receptor 2-negative locally advanced or metastatic breast cancer.They are also effective for new and recurrent ovarian cancers that are BRCA-or homologous recombination deficiency(HRD)-positive.However,data on these mutations and PARPi use in the Middle East are limited.AIM To assess BRCA/HRD prevalence and PARPi use in patients in the Middle East with breast/ovarian cancer.METHODS This was a single-center retrospective study of 57 of 472 breast cancer patients tested for BRCA mutations,and 25 of 65 ovarian cancer patients tested for HRD.These adult patients participated in at least four visits to the oncology service at our center between August 2021 and May 2023.Data were summarized using descriptive statistics and compared using counts and percentages.Response to treatment was assessed using Response Evaluation Criteria in Solid Tumors criteria.RESULTS Among the 472 breast cancer patients,12.1%underwent BRCA testing,and 38.5%of 65 ovarian cancer patients received HRD testing.Pathogenic mutations were found in 25.6%of the tested patients:26.3%breast cancers had germline BRCA(gBRCA)mutations and 24.0%ovarian cancers showed HRD.Notably,40.0%of gBRCA-positive breast cancers and 66.0%of HRD-positive ovarian cancers were Middle Eastern and Asian patients,respectively.PARPi treatment was used in 5(33.3%)gBRCA-positive breast cancer patients as first-line therapy(n=1;7-months progression-free),for maintenance(n=2;>15-months progression-free),or at later stages due to compliance issues(n=2).Four patients(66.6%)with HRD-positive ovarian cancer received PARPi and all remained progression-free.CONCLUSION Lower testing rates but higher BRCA mutations in breast cancer were found.Ethnicity reflected United Arab Emirates demographics,with breast cancer in Middle Eastern and ovarian cancer in Asian patients.

Predictions in Clinical Efficiency of SARS-CoV-2 RNA-Dependent RNA Polymerase (RdRp) Inhibitors by Molecular Docking

This study utilizes the enzyme-substrate complex theory to predict the clinical efficacy of COVID-19 treatments at the biological systems level, using molecular docking stability indicators. Experimental data from the Protein Data Bank and molecular structures generated by AlphaFold 3 were used to create macromolecular complex templates. Six templates were developed, including the holo nsp7-nsp8-nsp12 (RNA-dependent RNA polymerase) complex with dsRNA primers (holo-RdRp-RNA). The study evaluated several ligands—Favipiravir-RTP, Remdesivir, Abacavir, Ribavirin, and Oseltamivir—as potential viral RNA polymerase inhibitors. Notably, the first four of these ligands have been clinically employed in the treatment of COVID-19, allowing for comparative analysis. Molecular docking simulations were performed using AutoDock 4, and statistical differences were assessed through t-tests and Mann-Whitney U tests. A review of the literature on COVID-19 treatment outcomes and inhibitors targeting RNA polymerase enzymes was conducted, and the inhibitors were ranked according to their clinical efficacy: Remdesivir > Favipiravir-RTP > Oseltamivir. Docking results obtained from the second and third templates aligned with clinical observations. Furthermore, Abacavir demonstrated a predicted efficacy comparable to Favipiravir-RTP, while Ribavirin exhibited a predicted efficacy similar to that of Remdesivir. This research, focused on inhibitors of SARS-CoV-2 RNA-dependent RNA polymerase, establishes a framework for screening AI-generated drug templates based on clinical outcomes. Additionally, it develops a drug screening platform based on molecular docking binding energy, enabling the evaluation of novel or repurposed drugs and potentially accelerating the drug development process.

Development of a multiplex polymerase chain reaction assay for detection of hepatitis C virus,hepatitis B virus,and human immunodeficiency virus 1

BACKGROUND Hepatitis C virus(HCV),hepatitis B virus(HBV),and human immunodeficiency virus 1(HIV-1)are the most epidemic blood-borne viruses,posing threats to human health and causing economic losses to nations for combating the infection transmission.The diagnostic methodologies that depend on the detection of viral nucleic acids are much more expensive,but they are more accurate than sero-logical testing.AIM To develop a rapid,cost-effective,and accurate diagnostic multiplex polymerase chain reaction(PCR)assay for simultaneous detection of HCV,HBV,and HIV-1.METHODS The design of the proposed PCR assay targets the amplification of a short conserved region featured with a distinguishable melting profile and electro-phoretic molecular weight inside each viral genome.Therefore,this diagnostic method will be appropriate for application in both conventional(combined with electrophoresis)and real-time PCR facilities.Confirmatory in silico investigations were conducted to prove the capability of the approached PCR assay to detect variants of each virus.Then,Egyptian isolates of each virus were subjected to the wet lab examination using the given diagnostic assay.RESULTS The in silico investigations confirmed that the PCR primers can match many viral variants in a multiplex PCR assay.The wet lab experiment proved the efficiency of the assay in distinguishing each viral type through high-resolution melting analysis.Compared to related published assays,the proposed assay in the current study is more sensitive and competitive with many expensive PCR assays.CONCLUSION This study provides a simple,cost-effective,and sensitive diagnostic PCR assay facilitating the detection of the most epidemic blood-borne viruses;this makes the proposed assay promising to be substitutive for the mistakable and cheap serological-based assays.

Locked nucleic acid real-time polymerase chain reaction method identifying two polymorphisms of hepatitis B virus genotype C2 infections,rt269L and rt269I

BACKGROUND The presence of two distinct hepatitis B virus(HBV)Pol RT polymorphisms,rt269L and rt269I,could contribute to the unique clinical or virological phenotype of HBV genotype C2.Therefore,a simple and sensitive method capable of identifying both types in chronic hepatitis B(CHB)patients infected with genotype C2 should be developed.AIM To develop a novel simple and sensitive locked nucleic acid(LNA)-real timepolymerase chain reaction(RT-PCR)method capable of identifying two rt269 types in CHB genotype C2 patients.METHODS We designed proper primer and probe sets for LNA-RT-PCR for the separation of rt269 types.Using synthesized DNAs of the wild type and variant forms,melting temperature analysis,detection sensitivity,and endpoint genotyping for LNA-RT-PCR were performed.The developed LNA-RT-PCR method was applied to a total of 94 CHB patients of genotype C2 for the identification of two rt269 polymorphisms,and these results were compared with those obtained by a direct sequencing protocol.RESULTS The LNA-RT-PCR method could identify two rt269L and rt269I polymorphisms of three genotypes,two rt269L types[‘L1’(WT)and‘L2’]and one rt269I type(‘I’)in single(63 samples,72.4%)or mixed forms(24 samples,27.6%)in 87(92.6%sensitivity)of 94 samples from Korean CHB patients.When the results were compared with those obtained by the direct sequencing protocol,the LNA-RT-PCR method showed the same results in all but one of 87 positive detected samples(98.9%specificity).CONCLUSION The newly developed LNA-RT-PCR method could identify two rt269 polymorphisms,rt269L and rt269I,in CHB patients with genotype C2 infections.This method could be effectively used for the understanding of disease progression in genotype C2 endemic areas.

Small Amplicons Mutation Library for Vaccine Screening by Error-Prone Polymerase Chain Reaction

Library construction is a common method used to screen target genes in molecular biology.Most library constructions are not suitable for a small DNA library(<100 base pair(bp))and low RNA library output.To maximize the library’s complexity,error-prone polymerase chain reaction(PCR)was used to increase the base mutation rate.After introducing the DNA fragments into the competent cell,the library complexity could reach 109.Library mutation rate increased exponentially with the dilution and amplification of error-prone PCR.The error-prone PCR conditions were optimized including deoxyribonucleotide triphosphate(dNTP)concentration,Mn^(2+)concentration,Mg^(2+)concentration,PCR cycle number,and primer length.Then,a RNA library with high complexity can be obtained by in vitro transcription to meet most molecular biological screening requirements,and can also be used for mRNA vaccine screening.

Confusing finding of quantitative fluorescent polymerase chain reaction analysis in invasive prenatal genetic diagnosis:A case report

BACKGROUND Quantitative fluorescent polymerase chain reaction(QF-PCR)is a rapid prenatal diagnostic method for abnormalities on chromosomes 21,18,and 13 and sex chromosomal aneuploidy.However,the value of QF-PCR in diagnosing chromosomal structural abnormalities is limited.In this article,we report a confusing QF-PCR finding in a pregnant woman who underwent amniocentesis.CASE SUMMARY The short tandem repeat marker AMXY(Xp22.2/Yp11.2)located on the sex chromosome exhibited a trisomic biallelic pattern,indicating that the karyotype of the fetus might be 47,XYY.Chromosome analysis performed on cultured amniocytes showed a normal male karyotype of the fetus.Copy number variation sequencing confirmed a 500 kb duplication at Yp11.2-Yp11.2(chrY:6610001_7110000)and a 250 kb duplication at Yp11.2-Yp11.2(chrY:7110001_7360000).CONCLUSION In conclusion,the comprehensive application of different methods could achieve a higher detection rate and accuracy for the prenatal diagnosis of chromosomal disorders through chromosomal testing.

Establishment of a rapid detection method of Ureaplasma urealyticum based on recombinant polymerase amplification

Ureaplasma urealyticum(UU),is one of the most vital pathogens causing genitourinary tract infections of the body,and it can result in poor maternal and perinatal outcomes.The aim of this study was to establish a method to detect Ureaplasma urealyticum based on recombinant polymerase amplification(RPA)technique.Specific primers and probes were designed according to the 16sRNA gene sequence of Ureaplasma urealyticum.Six pathogens were detected for real-time fluorescence RPA specificity verification,including Mycoplasma hominis(MH),Chlamydia trachomatis(CT),Neisseria gonorrhoeae(NG),Staphylococcus aureus,Escherichia coli,and Lactobacillus vaginalis.The sensitivity of the method was performed by gradient dilution of the extracted template.A total of 60 clinical samples were detected by the established real-time fluorescence RPA.Detection of Ureaplasma urealyticum can be completed within 20 minutes at 39°C using established RPA method.The minimum detection limit of Ureaplasma urealyticum by real-time fluorescence RPA was 3 pg.The evaluation of 60 clinical samples proved that RPA method was feasible.A high specificity,sensitivity,simplicity and rapidity method for Ureaplasma urealyticum detection was successfully established based on the real-time fluorescence RPA method.

Deoxyribonucleic Acid-Polymerase Chain Reaction Status of HIV Exposed Infants in a Sub Regional Prevention of Mother-to-Child Transmission of HIV Programme during the Period 2009-2020

Introduction: Transitioning to more efficacious Antiretrovirals for HIV infected pregnant women and infant prophylaxis has reduced Mother to child transmission of HIV significantly. This study aimed to determine HIV infection status in HIVexposed infants who had their first DNA polymerase chain reaction test in our molecular Laboratory. Subjects, Materials and Methods: Dried Blood Spots for HIV DNA results from 5 states between 2009 and 2020 were analyzed in the PCR laboratory of the Federal Teaching Hospital, Gombe. Results: Nine thousand eight hundred and twenty-three Human Immunodeficiency Virus Deoxyribonucleic acid polymerase Chain Reaction results were analysed;4937 (50.2%) were males. During the study period, there was an overall declining trend in the mother-to-child transmission rate from 3.8% in 2009 to 1.0% in 2020. 6120 (62.3%) of HIV + mothers received Highly active antiretroviral therapy HAART before pregnancy. 7845 (76.2%) of the infants received Nevirapine prophylaxis. Dried blood spot samples were collected from 4077 (41.5%) at 6 - 8 weeks. 8438 (85.9%) received cotrimoxazole. 9469 (96.4%) were ever breastfed. Of the 9823 HIV DNA PCR results, 255 (2.6%) were positive while 69/4077 (1.7%) and 109/2662 (4.1%) were positive for HIV DNA at 6 - 8 weeks and > 12 weeks respectively. (p = 0.001). 86/747 (11.5%) of infants whose HIV-positive mothers received no ARVS were HIV DNA positive. (p = 0.001). 106/884 (12.0%) of infants who had no Antiretroviral prophylaxis had positive HIV DNA results;7/413 (1.7%) with Zidovudine/Nevirapine prophylaxis had positive results. (p = 0.001). 246/9469 (2.6%) of infants that were ever breastfed were positive for HIV DNA;11/354 (3.0%) that never breastfed had positive HIV DNA. Conclusion: Lack of maternal/infant ARVs and prolonged breastfeeding increased the risk of infant HIV infection.

Development and Clinical Application of a Single-tube Nested PCR Method to Amplify the DNA Polymerase Ⅰ Gene of Treponema Pallidum

Objective: To develop a sensitive, specific and simple method for detection of extremely low numbers of T. pallidum in clinical specimens, as a significant addition to the serologic tests for syphilis diagnosis. Methods: Double-tube nested PCR(DN-PCR) and single-tube nested PCR(SN-PCR) assays were performed to amplify specific fragments of the DNA poly-merase I gene(polA) of T. pallidum. Sensitivity and specificity of the two PCR assays were tested. Eighty-six whole blood specimens from persons with suspected syphilis were detected by the two nested PCR methods. The TPPA test was used as a comparison for detecting syphilis in sera from corresponding patients. Results: Only specific amplicons could be obtained during amplification of the T. pallidum polA gene and the detection limit was approximately 1 organism when analyzed on gel by the two PCR methods. Of 86 clinical specimens, 62 were positive by TPPA. Of these, 54 and 51 were positive by the DN-PCR and SN-PCR, respectively, which does not represent a statistically significant difference between the two PCR tests. Of 24 TPPA-negative specimens, 5 were positive by both DN-PCR assay and SN-PCR assay. Conclusion: The SN- polA PCR method is extremely sensitive, specific and easy to perform for detecting low numbers of T. pallidum in clinical blood specimens as a complementary to serology for syphilis diagnosis.

A Molecular Approach to Identification of the Chinese Drug“pu Gong Ying”(Herba Taraxaci)and Six Adulterants byDNA Fingerprinting Using Random Primed PolymeraseChain Resaction(PCR)

DNA fingerprinting among members of the Chinese drug Pu Gong Ying(Taraxacum mongolicum Hand,-Mazz.)and six adulterants of Tu Gong Ying were demonstrated with random-primed polymerase chain reaction(PCR)including arbitrarily primed polymerase chain reaction(AP-PCR)and random amplified polymorphic DNA(RAPD).Distinctive,reproducible genomic fingerprints from DNA from 7 species belonged to Compositae were generated with two long(20 and 24 mer)and one short(10 mer)randomly chosen primers.The Pu Gong Ying can be differentiated from six species of Tu Gong Ying according to the banding pattems of their amplified DNA on agarose gels.The results showed that AP-PCR and RAPD methods can be used for identifying Chinese drugs.Moreover,the Similarity Indexes of the genomic DNA fingerprints showed that Pu Gong Ying and its adulterants are unrelated.Therefore,AP-PCR and RAPD methods can be used for identifying Chinese drugs.

Hepatitis C virus in human B lymphocytes transformed by Epstein-Barr virus in vitro by in situ reverse transcriptase-polymerase chain reaction

AIM: To study persistence and replication of hepatitis C virus (HCV) in patients' peripheral blood mononuclear cells (PBMC) cultured in vitro. METHODS: Epstein Barr virus (EBV) was used to transform the hepatitis C virus from a HCV positive patient to permanent lymphoblastoid cell lines (LCL). Positive and negative HCV RNA strands of the cultured cells and growth media were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) each month. Core and NS5 proteins of HCV were further tested using immunohistochemical SP method and in situ RT-PCR. RESULTS: HCV RNA positive strands were consistently detected the cultured cells for one year. The negative-strand RNA in LCL cells and the positive-strand RNA in supernatants were observed intermittently. Immunohistochemical results medicated expression of HCV NS3 and C proteins in LCL cytoplasm mostly. The positive signal of PCR product was dark blue and mainly localized to the LCL cytoplasm. The RT-PCR signal was eliminated by overnight RNase digestion but not DNase digestion. CONCLUSION: HCV may exist and remain functional in a cultured cell line for a long period.

Recombinase polymerase amplification as a promising tool in hepatitis C virus diagnosis

Hepatitis C virus(HCV)infection represents a significant health problem and represents a heavy load on some countries like Egypt in which about 20%of the total population are infected.Initial infection is usually asymptomatic and result in chronic hepatitis that give rise to complications including cirrhosis and hepatocellular carcinoma.The management of HCV infection should not only be focus on therapy,but also to screen carrier individuals in order to prevent transmission.In the present,molecular detection and quantification of HCV genome by real time polymerase chain reaction(PCR)represent the gold standard in HCV diagnosis and plays a crucial role in the management of therapeutic regimens.However,real time PCR is a complicated approach and of limited distribution.On the other hand,isothermal DNA amplification techniques have been developed and offer molecular diagnosis of infectious dieses at point-of-care.In this review we discuss recombinase polymerase amplification technique and illustrate its diagnostic value over both PCR and other isothermal amplification techniques.

Flexibility in the order of action and in the enzymology of the nuclease, polymerases, and ligase of vertebrate non-homologous DNA end joining： relevance to cancer, aging, and the immune system

Nonhomologous DNA end joining （NHEJ） is the primary pathway for repair of double-strand DNA breaks in human cells and in multicellular eukaryotes. The causes of double-strand breaks often fragment the DNA at the site of damage, resulting in the loss of information there. NHEJ does not restore the lost information and may resect additional nucleotides during the repair process. The ability to repair a wide range of overhang and damage configurations reflects the flexibility of the nuclease, polymerases, and ligase of NHEJ. The flexibility of the individual components also explains the large number of ways in which NHEJ can repair any given pair of DNA ends. The loss of information locally at sites of NHEJ repair may contribute to cancer and aging, but the action by NHEJ ensures that entire segments of chromosomes are not lost.

The fidelity of DNA synthesis by eukaryotic replicative and translesion synthesis polymerases

In their seminal publication describing the structure of the DNA double helix , Watson and Crick wrote what may be one of the greatest understatements in the scientific literature, namely that ＂It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.＂ Half a century later, we more fully appreciate what a huge challenge it is to replicate six billion nucleotides with the accuracy needed to stably maintain the human genome over many generations. This challenge is perhaps greater than was realized 50 years ago, because subsequent studies have revealed that the genome can be destabilized not only by environmental stresses that generate a large number and variety of potentially cytotoxic and mutagenic lesions in DNA but also by various sequence motifs of normal DNA that present challenges to replication. Towards a better understanding of the many determinants of genome stability, this chapter reviews the fidelity with which undamaged and damaged DNA is copied, with a focus on the eukaryotic B- and Y-family DNA polymerases, and considers how this fidelity is achieved.

Sequencing of hepatitis C virus cDNA with polymerase chain reaction directed sequencing *

AIM To explore a rapid and easy sequencing method for hepatitis C virus (HCV) genome, and establish a new sequencing method in China. METHODS Polymerase Chain Reaction (PCR) was combined with DNA sequencing technique. PCR products were purified by agarose gel electrophoresis, polyacrylamide gel electrophoresis (PAGE), Polyethylene glycol (PEG) respectively. Then in the presence of a 5′ labeling PCR primer, purified PCR products were directly sequenced. By this method, HCV NS5b cDNA from two HCV infected individuals (HC 42 and HC 49) were sequenced.

Rapid quantification of semen hepatitis B virus DNA by real-time polymerase chain reaction

AIM： To examine the sensitivity and accuracy of real-time polymerase chain reaction （PCR） for the quantification of hepatitis B virus （HBV） DNA in semen. METHODS： Hepatitis B viral DNA was isolated from HBV carriers＇ semen and sera using phenol extraction method and QIAamp DNA blood mini kit （Qiagen, Germany）. HBV DNA was detected by conventional PCR and quantified by TaqMan technology-based real-time PCR （quantitative polymerase chain reaction （qPCR））. The detection threshold was 200 copies of HBV DNA for conventional PCR and 10 copies of HBV DNA for real time PCR per reaction. RESULTS： Both methods of phenol extraction and QIAamp DNA blood mini kit were suitable for isolating HBV DNA from semen. The value of the detection thresholds was 500 copies of HBV DNA per mL in the semen. The viral loads were 7.5×10^7 and 1.67×10^7 copies of HBV DNA per mL in two HBV infected patients＇ sera, while 2.14×10^5 and 3.02×10^5 copies of HBV DNA per mL in the semen. CONCLUSION： Real-time PCR is a more sensitive and accurate method to detect and quantify HBV DNA in the semen.

XRCC1 and DNA polymerase β in cellular protection against cytotoxic DNA single-strand breaks

Single-strand breaks （SSBs） can occur in cells either directly, or indirectly following initiation of base excision repair （BER）. SSBs generally have blocked termini lacking the conventional 5＇-phosphate and 3＇-hydroxyl groups and require further processing prior to DNA synthesis and ligation. XRCC1 is devoid of any known enzymatic activity, but it can physically interact with other proteins involved in all stages of the overlapping SSB repair and BER pathways, including those that conduct the rate-limiting end-tailoring, and in many cases can stimulate their enzymatic activities. XRCC1^-/- mouse fibroblasts are most hypersensitive to agents that produce DNA lesions repaired by monofunctional glycosylase-initiated BER and that result in formation of indirect SSBs. A requirement for the deoxyribose phosphate lyase activity of DNA polymerase β （pol β） is specific to this pathway, whereas pol β is implicated in gap-filling during repair of many types of SSBs. Elevated levels of strand breaks, and diminished repair, have been demonstrated in MMS- treated XRCC1^-/-, and to a lesser extent in pol β^-/- cell lines, compared with wild-type cells. Thus a strong correlation is observed between cellular sensitivity to MMS and the ability of cells to repair MMS-induced damage. Exposure of wild-type and polβ^-/- cells to an inhibitor of PARP activity dramatically potentiates MMS-induced cytotoxicity. XRCC1^-/- cells are also sensitized by PARP inhibition demonstrating that PARP-mediated poly（ADP-ribosyl）ation plays a role in modulation of cytotoxicity beyond recruitment of XRCC 1 to sites of DNA damage.

Detection of PERV by polymerase chain reaction and its safety in bioartificial liver support system

AIM： To establish a method detecting porcine endogenous retrovirus （PERV） in China experimental minipigs and to evaluate the safety of PERV in three individuals treated with bioartificial liver support systems based on porcine hepatocytes. METHODS： Porcine hepatocytes were isolated with two-stage perfusion method, then cultured in the bioreactor, which is separated by a semipermeable membrane （0.2μm） from the lumen through which the patients＇ blood plasma was circulated. After posthemoperfusion, patients＇ blood was obtained for screening. Additionally, samples of medium collected from both intraluminal and extraluminal compartments of the laboratory bioreactor and culture supernate in vitro was analyzed. The presence of viral sequences was estimated by polymerase chain reaction （PCR） and reverse transcriptase-polymerase chain reaction （RTPCR）. Finally, the infection of virus in the supernate of common culture was ascertained by exposure to the fetal liver cells. RESULTS： PERV-specific gag sequences were found in the porcine hepatocytes using RT-PCR. and were detected in all samples from the intraluminal, extraluminal samples and culture supernate. However, culture supernatant from primary porcine hepatocytes （cleared of cellular debris） failed to infect human fetal liver cells. Finally, RT-PCR detected no PERV infection was found in the blood samples obtained from three patients at various times post-hemoperfusion. CONCLUSION： The assays used are specific and sensitive, identified by second PCR. PERVs could be released from hepatocytes cultured in bioreactor without the stimulation of mitogen and could not be prevented by the hollow fiber semipermeable membrane, indicating the existence of PERV safety in extracorporeal bioartificial liver support system （EBLSS）.

Study of differential polymerase chain reaction of C-erbB-2 oncogene amplification in gastric cancer

AIM To study the significance of C-erbB-2 oncogene amplification in gastric cancer.METHODS C-erbB-2 oncogene amplification was examined by using differential polymerase chain reaction (dPCR) in surgical and endoscopic specimens of 83 cases of gastric cancer and 101 metastatic lymph nodes.RESULTS C-erbB-2 amplification was found in 28.9% (24/ 83) surgical specimens and 20.5% (17/ 83) endoscopic ones of gastric cancer patients. The amplification was significant in both types of specimens of advanced cancer cases (P＜0.05) and surgical specimens with lymph node metastasis (P＜0.01). The incidence of C-erbB-2 amplification in lymph nodes with metastasis was higher than in primary sites (surgical specimens, P＜0.05). The patients with amplification tumors had poorer 5-year survival rates than those with unamplification ones in the early cancers and well to moderately differentiated adenocarcinomas (P＜0.05). The same surgical samples were tested again by Southern blot hybridization to ascertain C-erbB-2 amplification, and the positive rate of C-erbB-2 amplification (15.7%) was lower than that of dPCR (28.9%, P＜0.05).CONCLUSION Examining C-erbB-2 amplification by dPCR is a quick, simple, reliable and independent method, and is helpful in predicting prognosis and metastatic potential of gastric cancer.