[A comparative analysis of the distribution of the high-risk population of upper gastrointestinal cancer and endoscopic screening compliance in two urban areas and two rural areas in China].

Objective: To analyze and compare the distribution of the high-risk population of upper gastrointestinal (UGI) cancer and the factors influencing the compliance rate of endoscopic screening in urban China and rural China. Methods: From 2015 to 2017, an epidemiological survey was conducted on residents aged 40-69 in two rural areas (Luoshan county of Henan province, Sheyang county of Jiangsu province) and two urban areas (Changsha city of Hunan province, Harbin city of Heilongjiang province). As a result, high-risk individuals were recommended for endoscopic screening. Chi-square χ(2) test was used to compare the high-risk rate of UGI cancer between urban and rural residents. In addition, the multivariate logistic regression model was used to analyze the factors influencing the compliance rate of endoscopic screening. Results: A total of 48, 310 residents aged 40-69 were enrolled in this study, including 22 870 (47.34%) residents from rural areas and 25 440 (52.66%) residents from urban areas. A total of 23 532 individuals were assessed with a high risk of UGI cancer, with an overall risk rate of 48.71%. A higher proportion of participants with high risk was observed in rural China (56.17%, 12 845/22 870) than in urban China (42.01%, 10 687/25 440). A total of 10 971 high-risk individuals with UGI cancer participated in endoscopic screening, with an overall compliance rate of 46.62% (10 971/23 532), 45.15% (5 799/12 845) in rural China, and 48.40% (5 172/10 687) in urban China. In rural population, the compliance rate of endoscopic screening was higher in those of females, aged 50-69 years, primary school education or above, high income, a family history of UGI cancer, history of gastric and duodenal ulcer, history of reflux esophagitis, and history of superficial gastritis, but lower in smokers (P<0.05). Among the urban population, the compliance rate of endoscopic screening was higher in those aged 40-49 years, uneducated, low income, family history of UGI cancer, history of reflux esophagitis, history of superficial gastritis, but lower in smokers (P<0.05). Conclusions: The proportion of participants with high risk of UGI cancer in rural areas is higher than that of urban areas. The compliance rates of endoscopic screening in urban and rural areas are low, and influencing factors of endoscopic screening exhibit some differences in rural China and urban China.

Anti-viral therapy is associated with improved survival but is underutilised in patients with hepatitis B virus-related hepatocellular carcinoma: real-world east and west experience.

BACKGROUND: Hepatitis B virus (HBV) is the leading cause of hepatocellular carcinoma (HCC) worldwide. It remains incompletely understood in the real world how anti-viral therapy affects survival after HCC diagnosis. METHODS: This was an international multicentre cohort study of 2518 HBV-related HCC cases diagnosed between 2000 and 2015. Cox proportional hazards models were utilised to estimate hazard ratios (HR) with 95% (CI) for anti-viral therapy and cirrhosis on patients' risk of death. RESULTS: Approximately, 48% of patients received anti-viral therapy at any time, but only 17% were on therapy at HCC diagnosis (38% at US centres, 11% at Asian centres). Anti-viral therapy would have been indicated for >60% of the patients not on anti-viral therapy based on American criteria. Patients with cirrhosis had lower 5-year survival (34% vs 46%; P < 0.001) while patients receiving anti-viral therapy had increased 5-year survival compared to untreated patients (42% vs 25% with cirrhosis and 58% vs 36% without cirrhosis; P < 0.001 for both). Similar findings were seen for other patient subgroups by cancer stages and cancer treatment types. Anti-viral therapy was associated with a decrease in risk of death, whether started before or after HCC diagnosis (adjusted HR 0.62 and 0.79, respectively; P < 0.001). CONCLUSIONS: Anti-viral therapy improved overall survival in patients with HBV-related HCC across cancer stages and treatment types but was underutilised at both US and Asia centres. Expanded use of anti-viral therapy in HBV-related HCC and better linkage-to-care for HBV patients are needed.

Randomised clinical trial: comparison of two everolimus dosing schedules in patients with advanced hepatocellular carcinoma.

BACKGROUND: Deregulation of mammalian target of rapamycin (mTOR) signalling is common in human hepatocellular carcinoma (HCC). AIM: To determine the maximum tolerated dose (MTD) of the oral mTOR inhibitor everolimus in advanced HCC patients. METHODS: Patients with locally advanced or metastatic HCC (Child-Pugh class A or B) were enrolled in an open-label phase 1 study and randomly assigned to daily (2.5-10 mg) or weekly (20-70 mg) everolimus in a standard 3 + 3 dose-escalation design. MTD was based on the rate of dose-limiting toxicities (DLTs). Secondary endpoints included safety, pharmacokinetics and tumour response. In a post hoc analysis, serum hepatitis B virus (HBV) DNA levels were quantified. RESULTS: Thirty-nine patients were enrolled. DLTs occurred in five of 21 patients in the daily and two of 19 patients in the weekly cohort. Daily and weekly MTDs were 7.5 mg and 70 mg respectively. Grade 3/4 adverse events with a ≥10% incidence were thrombocytopenia, hypophosphataemia and alanine transaminase (ALT) elevation. In four hepatitis B surface antigen (HBsAg)-seropositive patients, grade 3/4 ALT elevations were accompanied by significant (>1 log) increases in serum HBV levels. The incidence of hepatitis flare (defined as ALT increase >100 IU/mL from baseline) in HBsAg-seropositive patients with and without detectable serum HBV DNA before treatment was 46.2% and 7.1% respectively (P < 0.01, Fisher exact test). Disease control rates in the daily and weekly cohorts were 71.4% and 44.4% respectively. CONCLUSIONS: The recommended everolimus dosing schedule for future hepatocellular carcinoma studies is 7.5 mg daily. Prophylactic anti-viral therapy should be mandatory for HBsAg-seropositive patients (ClinicalTrials.gov NCT00390195).

Antinuclear antibody is associated with a more advanced fibrosis and lower RNA levels of hepatitis C virus in patients with chronic hepatitis C.

AIMS: Positive serum antinuclear antibody (ANA) is present in a number of patients with chronic hepatitis C virus (HCV) infection. This study aimed to evaluate the prevalence of ANA in patients with chronic hepatitis C (CHC) and to elucidate its clinical implications in virological and histological characteristics of CHC infection. METHODS: A total of 614 CHC patients were enrolled in this prospective, hospital-based study. The serum levels of aspartate aminotransferase, alanine aminotransferase and ANA, and HCV genotype, HCV RNA level, and histological activity index scores for liver histopathology, were determined. RESULTS: The prevalence of positive ANA (titre >1:40) was 35.0%. Women had a significantly higher prevalence than men (41.2 vs 31.0%; p = 0.012). Patients positive for ANA were significantly older (mean (SD), 53.7 (10.5) vs 49.7 (11.3) years; p<0.001) and had higher mean (SD) alanine aminotransferase levels (186.9 (178.8) vs 155.50 (113.5) IU/l; p<0.001) and lower mean (SD) HCV RNA levels (5.2 (0.9) vs 5.4 (1.0) log IU/ml; p = 0.048) than those without ANA. Among 447 patients undergoing liver biopsy, those positive for ANA had a significantly higher mean (SD) fibrosis score (2.0 (1.3) vs 1.5 (1.1); p<0.001) and a higher frequency of F3-4 (69/187, 36.9% vs 50/260, 19.2%; p<0.001) than those negative for ANA. Multivariate logistic regression analyses showed that advanced fibrosis, lower HCV RNA levels and age were significant factors related to positive ANA. CONCLUSION: ANA is associated with a more advanced liver fibrosis and lower serum HCV RNA level in patients with CHC.

Sustained virological response to interferon reduces cirrhosis in chronic hepatitis C: a 1,386-patient study from Taiwan.

BACKGROUND: The long-term benefits of interferon-based therapy on preventing cirrhosis at non-cirrhotic stage in chronic hepatitis C patients are not fully clarified. AIM: To evaluate the effectiveness of interferon-based therapy regarding to cirrhosis prevention in non-cirrhotic chronic hepatitis C patients. METHODS: A total of 1386 biopsy-proven, non-cirrhotic chronic hepatitis C patients (892 received interferon-based therapy and 494 untreated) were enrolled. RESULTS: Fifty-six untreated and 51 treated (24 sustained virologic responders and 27 non-responders) patients developed cirrhosis during a mean follow-up period of 5.0 (1-16) and 5.1 (1-15.3) years, respectively. The annual incidences of cirrhosis in untreated and treated groups were 2.26 and 1.11% (non-responders: 1.99%, sustained responders: 0.74%), respectively. The 15-year cumulative incidence of cirrhosis was significantly lower in treated (9.9%) than untreated patients (39.8%, P = 0.0008, log-rank test). The 14.5-year cumulative incidence of cirrhosis was significantly lower in sustained responders (4.8%) compared with non-responders (21.6%, P = 0.0007) and untreated patients (36.6%, P < 0.0001). The difference was not significant between non-responders and untreated controls. Cox proportional hazards regression showed sustained virologic responders and younger age were independent negative factors for cirrhosis development. CONCLUSION: A sustained virologic response secondary to IFN-based therapy could reduce cirrhosis development in chronic hepatitis C patients.

Associations of tumour necrosis factor alpha promoter polymorphisms at position -308 and -238 with clinical characteristics of chronic hepatitis C.

The aim of this study was to investigate the association between G vs A transitions in the promoter region of the tumour necrosis factor (TNF) alpha at positions -308 (TNF308.2) and -238 (TNF238.2) and clinical features of chronic hepatitis C (CHC). These two promoter TNF-alpha variants were determined in 250 biopsy-proven CHC patients by polymerase chain reaction amplification, followed by the Restriction Fragment Length Polymorphism (RFLP) method. The distribution of -308 and -238 TNF-alpha promoter genotypes were TNF308.1/TNF308.1: 187 (74.8%), TNF308.1/TNF308.2: 57 (22.8%) and TNF308.2/TNF308.2: 6 (2.4%), respectively, and TNF238.1/TNF238.1: 247 (98.8%) and TNF238.1/TNF238.2: 3 (1.2%). The frequencies of the TNF308.2 and TNF238.2 promoter alleles were 13.8% and 0.6%. Increased TNF308.2 allele copy numbers were significantly associated with increased frequency of lower pretreatment hepatitis C virus (HCV) RNA levels (<800 000 IU/mL; P = 0.031) and severe fibrosis stage (F3-F4; P = 0.006) and higher mean fibrosis score (P = 0.007). The higher cytokine production (with one or two TNF308.2 alleles) was correlated significantly with lower pretreatment HCV RNA levels with a lower mean HCV RNA level (P = 0.024) and increased frequency of lower pretreatment HCV RNA levels (<800 000 IU/mL; P = 0.017). Stepwise logistic regression showed that higher fibrosis score and low HCV RNA levels were independently related to the TNF308.2 allele [odds ratio (95% CI): 1.385 (1.127-1.702) and 0.698 (0.488-0.990)]. We conclude that inheritance of the TNF-alpha promoter genotype at the position -308 appears to be associated with variability in severity of fibrosis and viral load in chronic HCV infection.

Serum insulin-like growth factor-II as a serologic marker of small hepatocellular carcinoma.

OBJECTIVE: Alpha-fetoprotein (AFP) is not a useful tumor marker for diagnosis of small hepatocellular carcinoma (HCC). There is over-expression of insulin-like growth factor (IGF)-II in HCC tissue. This study investigates the diagnostic application of IGF-II in small HCC. MATERIAL AND METHODS: Serum levels of IGF-II and AFP were determined in 41 patients with small cirrhotic HCC (< or = 3 cm), 41 sex- and age-matched patients with cirrhosis alone (LC), and 41 healthy adults. The optimal cut-off values for diagnosing HCC were determined with receiver operating characteristics (ROC) curve. RESULTS: Both IGF-II and AFP levels in HCC were higher than those in LC patients or controls (each p = 0.0001). The IGF-II levels in LC patients were lower than those in controls (p = 0.001). In HCC patients, multivariate analysis indicated that that both IGF-II (odds ratio, 4.54; 95% confidence interval, 2.15-9.55; p = 0.0001) and AFP (odds ratio, 1.05; 95% confidence interval, 1.01-1.08; p = 0.003) were found to be associated with an increased risk of presence of HCC. The optimal cut-off values of IGF-II (4.1 mg/g prealbumin) and AFP (50 ng/ml) were determined with ROC curves. The sensitivity, specificity, and diagnostic accuracy values for IGF-II were 63%, 90%, and 70%, respectively. Those for AFP were 44%, 95%, and 70%, respectively. Determination of both markers in parallel significantly increase the diagnostic accuracy (88%) and sensitivity (80%), with a high specificity (90%). CONCLUSIONS: Serum IGF-II level can be used as an independent serologic marker or a complementary tumor marker to AFP for diagnosis of small HCC.

Serum insulin-like growth factor-II and alpha-fetoprotein as tumor markers of hepatocellular carcinoma.

To evaluate the diagnostic application of serum insulin-like growth factor-II (IGF-II) and alpha-fetoprotein (AFP) levels in hepatocellular carcinoma (HCC), IGF-II and AFP were determined in 100 cirrhotic patients with HCC, 100 sex- and age-matched patients with cirrhosis alone and 50 healthy controls. The results indicated that IGF-II and AFP levels in patients with HCC were higher than in those with cirrhosis alone (p = 0.0001). There is an inverse correlation between IGF-II and (log)AFP (r = -0.410, p = 0.0001) in patients with HCC. Multivariate analysis indicated that IGF-II and AFP were closely associated, in a dose-related fashion, with the presence of HCC. Receiver operating characteristic curves were used to determine the optimal cutoff values of IGF-II (4.5 mg/g prealbumin) and AFP (100 ng/ml), respectively. Both IGF-II and AFP show a high specificity and positive likelihood ratio. The sensitivity was 42.0% for IGF-II and 73.0% for AFP. Determination of both markers in parallel significantly increased the diagnostic accuracy (96.5%) and sensitivity (97.9%), with a high specificity (95.1%) and positive likelihood ratio (19.9). In conclusion, IGF-II and AFP may be used as complementary tumor markers to discriminate HCC from cirrhosis.

The prevalence of TT virus and GB virus C/hepatitis G virus infection in individuals with raised liver enzymes but without HBV or HCV infection in Taiwan.

The prevalence of TT virus (TTV) and GB virus-C/hepatitis G virus (GBV-C/HGV) infection and the association with raised liver function tests in 546 Taiwanese with negative HBsAg, anti-HCV and HCV RNA was elucidated. They were tested for serum alanine aminotransferase (ALT), GBV-C/HGV RNA, anti-envelope protein 2 antibody (anti-E2) and TTV DNA. Direct sequencing and phylogenetic analyses were performed on 58 isolates for TTV genotype determination. The prevalence of TTV DNA, GBV-C/HGV RNA, anti-E2 and over all GBV-C/HGV exposure was 24.9, 3.4, 8.2 and 11.1%, respectively. Using uni- and multi-variate analyses, male gender and TTV viremia were associated significantly with raised ALT values. Sixty-nine percent of TTV isolates were deduced to be TTV genotype 1 and they had significantly lower mean age than genotype non-1 isolates. In the population, raised ALT may be related to male gender and be attributable to TTV infection but not to GBV-C/HGV among individuals with no evidence of current HBV and HCV infection. TTV genotype 1 is the most prevalent genotype and associated with younger age.

Changing prevalence of hepatitis C virus genotypes: molecular epidemiology and clinical implications in the hepatitis C virus hyperendemic areas and a tertiary referral center in Taiwan.

To determine the hepatitis C virus (HCV) genotype distribution in Taiwan and to clarify the relationship between genotype and the pathogenesis of HCV infection, 1,164 subjects positive for serum HCV antibodies and HCV RNA from three HCV hyperendemic areas (Masago, Tzukuan, and Taoyuan) and a tertiary referral center in Taiwan were studied during 1995-1997. HCV genotypes and viral loads were determined using Okamoto's method and branched DNA assay, respectively. Genotype 1b was the most prevalent in Tzukuan (61.9%), Taoyuan (76.9%), and the referral center (47.0%). By contrast, genotype 2a was the major HCV type in Masago (63.5%). Prevalence of genotype 1b positively and that of genotype 2a negatively correlated to age, regardless of study populations (P < 0.01). Based on multivariate analysis, the significant factors associated with the presence of cirrhosis, with or without hepatocellular carcinoma, in chronic hepatitis C patients were genotype 1b and age. In conclusion, these results underline that independent HCV outbreaks continue in HCV hyperendemic areas in Taiwan, concomitant with a changing relative prevalence of HCV genotypes in relation to age. Both the correlation of genotype 1b with age (cohort effect) and intrinsic properties of HCV genotypes are probably responsible for the association between genotype and the pathogenesis of HCV infection.

The molecular epidemiology and clinical significance of TT virus (TTV) infection in healthy blood donors from southern Taiwan.

To evaluate the molecular epidemiology and clinical significance of th

Influence of hepatitis C virus on the profiles of patients with chronic hepatitis B virus infection.

BACKGROUND: Hepatitis B virus (HBV) and hepatitis C virus (HCV) are the most common causes of chronic liver disease, cirrhosis and hepatocellular carcinoma. The influence of HCV infection on the clinicopathological and virological profiles of chronic HBV infection was investigated. METHODS: A total of 100 chronic HBV carriers with histopathological diagnoses by liver biopsy were studied. Hepatitis B e antigen (HBeAg) and anti-HCV antibody were tested. Serum HCV-RNA was detected by using a nested reverse transcription-PCR assay. A branched DNA (bDNA) assay was used to detect HBV-DNA and quantitate the serum levels. RESULTS: Eighteen (18%) of 100 patients were positive for anti-HCV and HCV-RNA. Patients with concurrent HCV and HBV infection were significantly older than those without HCV infection (P < 0.05). The positive rates of HBeAg and HBV-DNA as well as the serum levels of HBV-DNA in patients with concurrent HCV and HBV infection were significantly lower than those without concurrent HCV and HBV infection (P < 0.01, P < 0.05, and P < 0.001, respectively). By using multivariate analysis, the factors of seroconversion of HBeAg and decreasing level of HBV-DNA were significantly correlated to concurrent HCV and HBV infection in chronic HBV carriers. The factors of increasing age and concurrent HCV and HBV infection were significantly correlated to seroconversion of HBeAg. CONCLUSIONS: The concurrent HCV and HBV infection in chronic HBV carriers might result in a suppression of HBV replication that presented with a lower level of serum HBV-DNA and HBeAg seroconversion. Nevertheless, neither more obvious increase in biochemical parameters nor histopathological progression to more advanced liver diseases was observed.

A family of tissue-specific resistin-like molecules.

We have identified a family of resistin-like molecules (RELMs) in rodents and humans. Resistin is a hormone produced by fat cells. RELMalpha is a secreted protein that has a restricted tissue distribution with highest levels in adipose tissue. Another family member, RELMbeta, is a secreted protein expressed only in the gastrointestinal tract, particularly the colon, in both mouse and human. RELMbeta gene expression is highest in proliferative epithelial cells and is markedly increased in tumors, suggesting a role in intestinal proliferation. Resistin and the RELMs share a cysteine composition and other signature features. Thus, the RELMs together with resistin comprise a class of tissue-specific signaling molecules.

Hepatitis C virus infection among teenagers in an endemic township in Taiwan: epidemiological and clinical follow-up studies.

The aim of the study was to elucidate the epidemiological features of Hepatitis C virus (HCV) infection among teenagers in an endemic area by conducting a mass screening study. We also investigated the clinical outcome of the anti-HCV-positive subjects by conducting subsequent short-term and long-term follow-up studies. All 2837 students of two junior middle schools in Tzukuan, aged 13-16 years, were invited to be screened for anti-HCV, HBsAg, AST and ALT in October 1995. A total of 2726 (96%) students responded. Anti-HCV, HCV RNA and aminotransferase levels were evaluated among anti-HCV-positive students 1 month and 30 months later, respectively. A total of 38 (1.4%; M/F = 22/16) participants were anti-HCV-positive. The anti-HCV-positive students had higher rates of exposures to transfusion, anti-HCV-positive families and surgery. The prevalence (2.8%) of the 7 maritime villages was markedly higher than that (0.7%) of the other 8 villages (P < 0.001). Subsequent follow-up studies demonstrated that there might be 5 cases of acute or recent HCV infection, and 6 cases who had recovered from chronic HCV infection.

p16(INK4a) expression begins early in human colon neoplasia and correlates inversely with markers of cell proliferation.

BACKGROUND & AIMS: p16(INK4a) is a cell cycle inhibitor and a major tumor-suppressor protein, but the regulation of p16(INK4a) is poorly understood and the physiologic settings in which it exerts its antiproliferative effects are unknown. A role for p16(INK4a) in intestinal neoplasia is suggested by the observation that the promoter region is methylated in a subset of human colon tumors. We examined the expression of the protein in specimens representing the full spectrum of neoplastic progression in the human colon and determined whether expressing cells showed evidence of cell cycle inhibition. METHODS: We studied p16(INK4a) expression by immunoprecipitation, immunoblotting, reverse-transcription polymerase chain reaction (RT-PCR), immunohistochemistry, and immunofluorescence in matched normal and neoplastic colonic tissue from 70 patients. RESULTS: p16(INK4a) expression was very low in normal mucosa, with staining observed in rare epithelial cells at the base of crypts. A distinctly higher expression was found in 4 of 7 aberrant crypt foci, 32 of 36 adenomas, 18 of 28 primary carcinomas, and 5 of 5 metastatic carcinomas. Within each neoplasm p16(INK4a) staining was heterogeneous, with higher expression commonly seen in areas bordering normal tissue. p16(INK4a) staining correlated inversely with that of Ki67, cyclin A, and the retinoblastoma protein, suggesting that cell cycle progression was inhibited. CONCLUSIONS: These results suggest that p16(INK4a) expression begins in the earliest detectable stages of neoplastic progression in the human colon and exerts a continuous, piecemeal constraint on tumor growth.

p16 INK4a can initiate an autonomous senescence program.

The tumor suppressor p16INK4a is a potent mediator of cell cycle arrest in transient expression studies, is induced in senescing cells, and can impose morphological features of senescence. Nonetheless, it is unclear whether p16INK4a can block cell proliferation irreversibly. We explored this issue using osteogenic sarcoma cell clones with inducible p16INK4a expression. Induction of p16INK4a for 1 day arrested most cells in G1 phase. If the induction was then interrupted, p16INK4a levels returned to baseline and robust growth resumed within 3-5 days. When p16INK4a was induced for 6 days DNA synthesis remained strongly inhibited and the cells acquired morphological features of senescence. Moreover, if p16INK4a induction was interrupted at this point and the cells were followed for 12 more days, most cells retained these morphologic features and either failed to divide or died. This occurred despite the prompt return of p16INK4a expression and retinoblastoma protein phosphorylation toward baseline levels. In fact, some senescing cells appeared to enter S phase. These results demonstrate that a sustained period of p16INK4a expression is sufficient in this setting to impose a durable block to cell proliferation and that this state becomes independent of p16INK4a expression, hypophosphorylation of pRB, or a strict G1 arrest.

Induction of p21(WAF1/CIP1) and inhibition of Cdk2 mediated by the tumor suppressor p16(INK4a).

The tumor suppressor p16(INK4a) inhibits cyclin-dependent kinases 4 and 6. This activates the retinoblastoma protein (pRB) and, through incompletely understood events, arrests the cell division cycle. To permit biochemical analysis of the arrest, we generated U2-OS osteogenic sarcoma cell clones in which p16 transcription could be induced. In these clones, binding of p16 to cdk4 and cdk6 abrogated binding of cyclin D1, p27(KIP1), and p21(WAF1/CIP1). Concomitantly, the total cellular level of p21 increased severalfold via a posttranscriptional mechanism. Most cyclin E-cdk2 complexes associated with p21 and became inactive, expression of cyclin A was curtailed, and DNA synthesis was strongly inhibited. Induction of p21 alone, in a sibling clone, to the level observed during p16 induction substantially reproduced these effects. Overexpression of either cyclin E or A prevented p16 from mediating arrest. We then extended these studies to HCT 116 colorectal carcinoma cells and a p21-null clone derived by homologous recombination. In the parental cells, p16 expression also augmented total cellular and cdk2-bound p21. Moreover, p16 strongly inhibited DNA synthesis in the parental cells but not in the p21-null derivative. These findings indicate that p21-mediated inhibition of cdk2 contributes to the cell cycle arrest imposed by p16 and is a potential point of cooperation between the p16/pRB and p14(ARF)/p53 tumor suppressor pathways.

Cloning and functional analysis of Kaposi's sarcoma-associated herpesvirus DNA polymerase and its processivity factor.

Kaposi's sarcoma-associated herpesvirus (KSHV), or human herpesvirus 8, is a newly identified virus with tumorigenic potential. Here, we cloned and expressed the DNA polymerase (Pol-8) of KSHV and its processivity factor (PF-8). Pol-8 bound specifically to PF-8 in vitro. Moreover, the DNA synthesis activity of Pol-8 was shown in vitro to be strongly dependent on PF-8. Addition of PF-8 to Pol-8 allowed efficient synthesis of fully extended DNA products corresponding to the full-length M13 template (7,249 nucleotides), whereas Pol-8 alone could incorporate only several nucleotides. The specificity of PF-8 and Pol-8 for each other was demonstrated by their inability to be functionally replaced by the DNA polymerases and processivity factors of herpes simplex virus 1 and human herpesvirus 6.