Clinical benefit analysis of PD-1 inhibitors in patients with advanced, recurrent or metastatic cervical cancer: a meta-analysis and systematic review

Purpose

This study aims to comprehensively evaluate the efficacy and safety of programmed cell death protein-1 (PD-1) in patients with advanced, recurrent, or metastatic cervical cancer (ARMCC) and identify the population that may benefit the most.

Methods

We conducted a search of PubMed, EMBASE, and the Cochrane Collaboration Library from their inception to September 2023. We extracted and analyzed the results related to the efficacy and safety of PD-1 in patients with ARMCC. The primary endpoints included the overall objective response rate (ORR) and adverse events (AEs), while the secondary endpoints encompassed the 1-year overall survival (OS) rate, 1-year progression-free survival (PFS) rate, as well as OS and PFS. We used a random effects model to conduct a meta-analysis on single-group rates, and the Mantel-Haenszel method was utilized to compare the ORR and the incidence of AEs.

Results

Our study included a total of 21 trials involving 2,097 patients. The ORR of the combination of PD-1 inhibitors with chemotherapy was 56.36%, the combination of PD-1 inhibitors with anti-angiogenic agents was 38.72%, the combination of PD-1 inhibitors with Cytotoxic T-lymphocyte antigen 4 inhibitors was 25.60%, and PD-1 inhibitor monotherapy was 15.99%. The subgroup analysis showed that the group of patients with squamous cell carcinoma (SCC) exhibited a significantly higher ORR compared to the non-SCC group in patients who received PD-1 inhibitors combined with other anti-tumor drugs (Odds Ratio =2.43, P=0.002). Additionally, the group of patients with a programmed death-ligand 1 combined positive score (PD-L1 CPS) ≥1 exhibited a significantly higher ORR compared to the PD-L1 CPS <1 group in patients who received PD-1 inhibitor monotherapy (OR=4.14, P=0.02). PD-1 inhibitor monotherapy or PD-1 inhibitors combined with chemotherapy did not significantly increase the incidence of all grades of adverse events (Relative Risk=0.99, p=0.788) or the incidence of serious adverse events (RR=0.99, p=0.788) compared to chemotherapy alone.

Conclusion

PD-1 inhibitors demonstrate outstanding efficacy in the treatment of patients with ARMCC. Patients with SCC may benefit more from treatments including PD-1 inhibitors in combination with other anti-tumor drugs, and PD-L1 CPS ≥1 can be considered a favorable indicator of immune therapy response. Importantly, the use of PD-1 inhibitor monotherapy or PD-1 inhibitors in combination with chemotherapy did not lead to an increased incidence of AEs compared with chemotherapy alone, indicting safety during treatment.

Systematic Review Registration

PROSPERO (CRD42023457945).

Macrocyclic Engineering of Thermally Activated Delayed Fluorescent Emitters for High-Efficiency Organic Light-Emitting Diodes

Several thermally activated delayed fluorescence (TADF) materials have been studied and developed to realize high-performance organic light-emitting diodes (OLEDs). However, TADF macrocycles have not been sufficiently investigated owing to the synthetic challenges, resulting in limited exploration of their luminescent properties and the corresponding highly efficient OLEDs. In this study, a series of TADF macrocycles is synthesized using a modularly tunable strategy by introducing xanthones as acceptors and phenylamine derivatives as donors. A detailed analysis of their photophysical properties combined with fragment molecules reveals characteristics of high-performance macrocycles. The results indicate that: a) the ideal structure decreases the energy loss, which in turn reduces the non-radiative transitions; b) reasonable building blocks increase the oscillator strength providing a higher radiation transition rate; c) the horizontal dipole orientation (Θ) of the extended macrocyclic emitters is increased. Owing to the high photoluminescence quantum yields of ≈100% and 92% and excellent Θ of 80 and 79% for macrocycles MC-X and MC-XT in 5 wt% doped films, the corresponding devices exhibit record-high external quantum efficiencies of 31.6% and 26.9%, respectively, in the field of TADF macrocycles.

[Long-term outcomes and failure patterns of definitive radiotherapy for cervical esophageal carcinoma]

Objective: To evaluate the long-term outcomes, failure patterns and prognostic factors of definitive radiotherapy in patients with cervical esophageal carcinoma (CEC). Methods: We retrospectively reviewed the clinical data of 148 CEC patients who treated with definitive radiotherapy in Cancer Hospital of Chinese Academy of Medical Sciences from January 2001 to December 2017. The median radiation dose was 66 Gy (59.4-70 Gy) and 33.1% of patients received concurrent chemotherapy. The Kaplan-Meier method was used to calculate survival rates. The log rank test was used for survival comparison and univariate prognostic analysis. The Cox model was used for multivariate prognostic analysis. Results: The median follow-up time was 102.6 months. The median survival time, 2- and 5-year overall survival (OS) were 22.7 months, 49.9% and 28.3%. The median, 2- and 5-year progression-free survival were 12.6 months, 35.8% and 25.8%. The 2- and 5-year locoregional recurrence-free survival were 59.1% and 50.8%. The 2- and 5-year distant metastases-free survival were 74.6% and 65.9%. Multivariate analysis showed that EQD(2)>66 Gy was the only independent prognostic indicator for OS (P=0.040). The median survival time and 5-year OS rate significantly improved in patients who received EQD(2)>66 Gy than those who received≤66 Gy (31.2 months vs. 19.2 months, 40.1% vs. 19.1%, P=0.027). A total of 87 patients (58.8%) developed tumor progression. There were 50 (33.8%), 23 (15.5%) and 39 (26.4%) patients developed local, regional recurrence and distant metastases, respectively. Eleven patients (7.4%) underwent salvage surgery, and the laryngeal preservation rate for entire group was 93.9%. Conclusions: Definitive radiotherapy is an effective treatment for cervical esophageal carcinoma with the advantage of larynx preservation. Local recurrence is the major failure pattern. EQD(2)>66 Gy is associated with the improved overall survival.

[Epidemiological characteristics of local COVID-19 epidemics and control experience in routine prevention and control phase in China]

The COVID-19 pandemic is still ongoing in the world, the risk of COVID-19 spread from other countries or in the country will exist for a long term in China. In the routine prevention and control phase, a number of local COVID-19 epidemics have occurred in China, most COVID-19 cases were sporadic ones, but a few case clusters or outbreaks were reported. Winter and spring were the seasons with high incidences of the epidemics; border and port cities had higher risk for outbreaks. Active surveillance in key populations was an effective way for the early detection of the epidemics. Through a series of comprehensive prevention and control measures, including mass nucleic acid screening, close contact tracing and isolation, classified management of areas and groups at risk, wider social distancing and strict travel management, the local COVID-19 epidemics have been quickly and effectively controlled. The experiences obtained in the control of the local epidemics would benefit the routine prevention and control of COVID-19 in China. The occurrence of a series of COVID-19 case clusters or outbreaks has revealed the weakness or deficiencies in the COVID-19 prevention and control in China, so this paper suggests some measures for the improvement of the future prevention and control of COVID-19.

[Course of disease and related epidemiological parameters of COVID-19: a prospective study based on contact tracing cohort]

Objective: To analyze the course of disease and epidemiological parameters of COVID-19 and provide evidence for making prevention and control strategies. Methods: To display the distribution of course of disease of the infectors who had close contacts with COVID-19 cases from January 1 to March 15, 2020 in Guangdong Provincial, the models of Lognormal, Weibull and gamma distribution were applied. A descriptive analysis was conducted on the basic characteristics and epidemiological parameters of course of disease. Results: In total, 515 of 11 580 close contacts were infected, with an attack rate about 4.4%, including 449 confirmed cases and 66 asymptomatic cases. Lognormal distribution was fitting best for latent period, incubation period, pre-symptomatic infection period of confirmed cases and infection period of asymptomatic cases; Gamma distribution was fitting best for infectious period and clinical symptom period of confirmed cases; Weibull distribution was fitting best for latent period of asymptomatic cases. The latent period, incubation period, pre-symptomatic infection period, infectious period and clinical symptoms period of confirmed cases were 4.50 (95%CI:3.86-5.13) days, 5.12 (95%CI:4.63-5.62) days, 0.87 (95%CI:0.67-1.07) days, 11.89 (95%CI:9.81-13.98) days and 22.00 (95%CI:21.24-22.77) days, respectively. The latent period and infectious period of asymptomatic cases were 8.88 (95%CI:6.89-10.86) days and 6.18 (95%CI:1.89-10.47) days, respectively. Conclusion: The estimated course of COVID-19 and related epidemiological parameters are similar to the existing data.

[Treatment and prognosis analysis of perineural invasion on sinonasal adenoid cystic carcinoma]

Objective: To analyze the efficacy of sinonasal adenoid cystic carcinoma (ACC) with perineural invasion (PNI), and explore the prognostic value of PNI on sinonasal adenoid cystic carcinoma. Methods: The clinical data of 105 patients with sinonasal ACC admitted to Cancer Hospital, Chinese Academy of Medical Sciences from January 2000 to December 2016 were retrospectively reviewed. All patients were restaged according to American Joint Committee on Cancer 8th edition. Follow-up visits were conducted to obtain information of treatment failure and survival outcome. The Log rank test was used for univariate analysis of prognostic factors, and Cox regression model was used for multivariate prognostic analysis. Results: The maxillary sinus (n=59) was the most common primary site, followed by the nasal cavity (n=38). There were 93 patients with stage Ⅲ-Ⅳ. The treatment modalities included surgery alone (n=14), radiotherapy alone (n=13), preoperative radiotherapy plus surgery (n=10), and surgery plus postoperative radiotherapy (n=68). The median follow-up time was 91.8 months, the 5-year local control (LC), distant metastasis-free survival (DMFS), progression-free survival (PFS), and overall survival (OS) rates were 72.6%, 73.0%, 52.9% and 78.0%, respectively. There were 33 patients (31.4%) with PNI-positive. The 5-year DMFS, PFS, and OS rates of PNI-positive group were 53.7%, 29.4% and 56.5%, respectively, which were significantly inferior to those of PNI-negative group (80.8%, 63.0% and 86.8%, respectively, P<0.05), while there was no significant difference in the 5-year LC rate between both groups (64.5% vs 76.5%, P=0.273). The multivariate Cox regression analysis showed PNI was one of the poor prognostic factors of DMFS (HR=3.514, 95%CI: 1.557-7.932), PFS (HR=2.562, 95%CI: 1.349-4.866) and OS (HR=2.605, 95%CI: 1.169-5.806). Among patients with PNI-positive, the 5-year LC, PFS and OS rates of patients received surgery combined with radiotherapy were 84.9%, 41.3% and 72.7%, respectively, which were significantly higher than 23.3%, 10.0% and 26.7% of patients receiving surgery or radiotherapy alone (P<0.05). Conclusion: The presence of PNI increases the risk of distant metastasis in patients with sinonasal ACC. Compared with patients with PNI-negative, the prognosis of patients with PNI-positive is relatively poor, and surgery combined with radiotherapy for PNI-positive sinonasal ACC results in good clinical outcomes.

[A study on the identification of threshold for early warning on adverse weather events based on the association of apparent temperature and years of life lost]

Objective: To identify the threshold of a health warning system based on the association of apparent temperature and years of life lost (YLL). Methods: Daily mortality records and meteorological data were collected from 364 Chinese counties for 2006-2017. Distributed lag nonlinear model and multivariate Meta-analyses were applied to estimate the association between the apparent temperature and YLL rate. A regression tree model was employed to estimate the warning thresholds of the apparent temperature. Stratified analyses were further conducted by age and cause of death. Results: The daily YLL rate was 23.6/10⁵. The mean daily apparent temperature was 15.7 ℃. U-shaped nonlinear associations were observed between apparent temperature and YLL rate. The actual temperature-caused YLL rate for the elderly was higher than the young population. The daily excess deaths rate increased with the higher effect levels. Conclusions: Regression tree model was employed to define the warning threshold for meteorological health risk. The present study provides theoretical support for the weather-related health warning system.

[The association between apparent temperature and hand, foot, and mouth disease and its spatial heterogeneity in Guangdong, Anhui and Jilin provinces]

Objective: To study the association between apparent temperature (AT) and the incidence of hand,foot, and mouth disease (HFMD) and its spatial heterogeneity in 46 cities in Guangdong, Anhui and Jilin provinces, and provide scientific evidence for the early warning of HFMD. Methods: The data of HFMD incidence and meteorological factors from 2009 to 2018 in Guangdong province, 2009 to 2015 in Anhui province, and 2013 to 2018 in Jilin province were collected. Distributed lag non-linear models were constructed to investigate the association between AT and the incidence of HFMD in 46 cities from three provinces in China. Meta-analysis was used to pool the city-specific estimates, and Meta-regression was applied to analyze the factors that may cause spatial heterogeneity. Results: The relationship between daily AT and the incidence of HFMD in 46 cities appeared nonlinear. The association in Guangdong was similar to that in Jilin, and the risk of HFMD increased with the increase of AT. While the risk of HFMD in Anhui first increased with the increase of AT, and peaked at 18.1 ℃ and then went down. AT on different levels showed different lag impacts and the higher AT showed greater and longer lag impact. The spatial heterogeneity of associations may have been caused by latitude, longitude, average temperature, and average sunshine hours. Conclusions: AT is a comprehensive index to evaluate the association between temperature, relative humidity and wind speed and the incidence of HFMD. Higher AT may increase the risk of HFMD. The AT and HFMD relationship across spatial heterogeneity varies depending on geographic location and meteorological conditions.

Effects of Polybrominated Diphenyl Ethers on the Human Body Exposure in E-Waste Dismantling Region

Objective To discuss the effects of polybrominated diphenyl ethers （PBDEs） exposure in e-waste dismantling region on the human body and provide data support for the identification of environmental health damage to residents in the e-waste dismantling region. Methods Adults in an e-waste dismantling region （exposed group, 54 participants） and a control region （control group, 58 participants） were selected, questionnaires were carried out and blood and urine samples were collected. Blood PBDEs, blood lipids, blood routine, blood lead, urine cadmium, urine chromium and urine nickel were detected. T-test was utilized to compare the differences of PBDEs between the two groups. Multivariate analysis were utilized to compare the differences between the two groups in blood routine indexes. Linear regression was used to analyze the relationship between PBDEs and blood routine. Results Exposure levels of PBDEs were significantly higher in the exposed group （240.00 ng/g, adjusted mass fraction of blood lipids, thereafter） than in the control group （93.00 ng/g, P<0.05）. There was no statistical significance in the differences in most blood routine indexes of the two groups （ P>0.05）, and their reference values were all within normal ranges. Mean platelet volume, plateletcrit, basophils percentage, absolute value of basophils, and mean corpuscular hemoglobin concentration were higher in the exposed group than in the control group （P<0.05）. Platelet distribution widths were lower in the exposed group than in the control group and below the normal reference range （P<0.05）. Conclusion PBDEs exposure in e-waste dismantling region tend to change platelet morphology, the number of basophils, and mean corpuscular hemoglobin concentration, and may pose potential health hazards to local residents.

[Risk assessment of exported risk of COVID-19 from Hubei Province]

Objective: To evaluate the exported risk of COVID-19 from Hubei Province and the imported risk in various provinces across China. Methods: Data of reported COVID-19 cases and Baidu Migration Indexin all provinces of the country as of February 14, 2020 were collected. The correlation analysis between cumulative number of reported cases and the migration index from Hubei was performed, and the imported risks from Hubei to different provinces across China were further evaluated. Results: A total of 49 970 confirmed cases were reported nationwide, of which 37 884 were in Hubei Province. The average daily migration index from Hubei to other provinces was 312.09, Wuhan and other cities in Hubei were 117.95 and 194.16, respectively. The cumulative COVID-19 cases of provinces was positively correlated with the migration index derived from Hubei Province, also in Wuhan and other cities in Hubei, with correlation coefficients of 0.84, 0.84, and 0.81. In linear model, population migration from Hubei Province, Wuhan and other cities in Hubei account for 71.2%, 70.1%, and 66.3% of the variation, respectively. The period of high exported risk from Hubei occurred before January 27, of which the risks before January 23 mainly came from Wuhan, and then mainly from other cities in Hubei. Hunan Province, Henan Province and Guangdong Province ranked the top three in terms of cumulative imported risk (the cumulative risk indices were 58.61, 54.75 and 49.62 respectively). Conclusion: The epidemic in each province was mainly caused by the importation of Hubei Province. Taking measures such as restricting the migration of population in Hubei Province and strengthening quarantine measures for immigrants from Hubei Province may greatly reduce the risk of continued spread of the epidemic.

[The definition of heat-wave based on mortality risk assessment in different regions of China]

Objective: To identify the definition of heat wave based on mortality risk assessment in different regions of China. Methods: Daily mortality (from China Information System for Disease Control and Prevention) and meteorological data (from National Meteorological Information Center in China) from 66 counties with a population of over 200 000 were collected from 2006-2011. With the consideration of climate type and administrative division, China was classified as seven regions. Firstly, distributed lag non-linear model (DLNM) was used to estimate community-specific effects of temperature on non-accidental mortality. Secondly, a multivariate meta-analysis was applied to pool the estimates of community-specific effects to explore the region-specific temperature threshold and the duration for definition of heat wave. Results: We defined regional heat wave of Northeast, North, Northwest, East, Central and Southwest China as being two or more consecutive days with daily mean temperature higher than or equal to the P(64), P(71), P(85), P(67), P(75) and P(77) of warm season (May to October) temperature, respectively, while the thresholds of temperature were 21.6, 23.7, 24.3, 25.7, 28.0 and 25.3 ℃. The heat wave in South China was defined as five or more consecutive days with daily mean temperature higher than or equal to the P(93) (30.4 ℃) of warm season (May to October) temperature. Conclusion: The region-specific definition of heat wave developed in our study may provide local government with the guidance of establishment and implementation of early heat-health response systems to address the negative health outcomes due to heat wave.

[Lagged effects of diurnal temperature range on mortality in 66 cities in China: a time-series study]

Objective: To estimate the effect of daily diurnal temperature range (DTR) on mortality in different areas in China. Methods: A time series study using the data collected from 66 areas in China was conducted, and Meta-analysis was used to analyze the estimates of associations between DTR and daily mortality. Modifying effects of extremely low and high DTR-mortality relationship by season and socioeconomic status (SES) were also evaluated respectively. Cumulative excess risk (CER) was used as an index to evaluate the effects. Results: The information about 1 260 913 registered deaths were collected between 1 January 2006 and 31 December 2011, we found the relationship between extreme DTR and mortality was non-linear in all regions and the exposure-response curve was J-shaped. In central and south areas of China, the result indicated the obvious acute effect of extremely high DTR, and the mortality effect in central area (CER=5.1%, 95% CI: 2.4%-7.9%) was significant higher than that in south area (CER=4.5%, 95% CI: 1.7%-7.3%). Regarding to the modification of seasons, the cumulative mortality effect of DTR in cold season (CER=5.8%, 95%CI: 2.5%-9.2%) was higher than that in hot season (CER=3.1%, 95%CI: 1.1%-5.1%). Generally, deaths among the elderly (≥75 years) were associated more strongly with extremely high DTR. Conclusions: The mortality effects of extremely DTR in different areas and seasons showed different characteristics, that in central area and in cold season it was significantly stronger. After modified by season and SES, DTRs were the greatest threat to vulnerable population, especially to the elderly (≥75 years). Therefore, more attention should be paid to vulnerable groups and protection measures should be taken according to the local and seasonal conditions.

[Effectiveness of health education about heat wave hazard prevention in the elderly: a mixed effect model analysis]

Objective: To evaluate the effectiveness of health education about prevention of heat wave hazard in the elderly. Methods: A non-randomized controlled trial was conducted during the summer of 2015 among a sample of residents aged ≥60 years in Panyu district, Guangzhou. Eight intervention measures for heat wave hazard prevention were taken in intervention group for 3 months (from August to October) and in control group no intervention measures were taken. The comparison of intervention effects was conducted between the intervention group and control group with mixed effect model after the collection of related information with same questionnaire. Results: After adjusting of family per capita income, family air-condition availability, alcohol use, disease history and time, the average score of risk awareness in the intervention group increased by 1.62, while it was 0.51 in the control group, the difference was significant (t=2.76, P=0.006). A significant effect was observed in the intervention group on the reduction of hospitalizations due to chronic diseases. The hospitalization rate due to chronic diseases in resent 3 months in the intervention group decreased from 32.39% (46/142) before intervention to 28.87% (41/142) after intervention; while in the control group, it increased from 26.28% (41/156) before intervention to 36.53% (57/156) after intervention. There was no significant difference between the two groups in awareness of knowledge on heat wave hazard prevention and the score of adaptation to heat wave. Conclusion: Health education programs could improve the risk awareness on heat waves, and reduce the hospitalizations due to chronic diseases in the elderly.

Multicenter study of autoverification methods of hematology analysis

This study was designed to establish and validate a set of autoverification methods for hematology analysis. One thousand and twenty-four samples were selected from Shanghai Ruijin Hospital and 999 from Beijing Hospital, China. False positive, false negative and autoverification pass rates were verified and the rules were then adjusted and confirmed according to the verification results. After confirmation, at least 10,000 sample cases were selected from Shanghai Ruijin Hospital, Beijing Hospital and China Armed Police General Hospital and checked automatically. The differences in the autoverification pass rate and average report delivery time before and after the application of the autoverification methods were compared between the three hospitals. Preliminary validation results showed that the false negative rates of the Shanghai Ruijin Hospital and Beijing Hospital were less than 2%. The false positive rates of these two hospitals were high, close to 18%. After rule adjustment, the false negative rate was basically the same as before adjustment, but the false positive rate declined obviously while the pass rate of autoverification improved significantly. The autoverification pass rates of the three hospitals were 76.4%, 85.1% and 84.2%, respectively. The turnover time (TAT, time from receipt of sample to report of the result) of the three hospitals decreased by 4.1 min, 8.8 min and 10.2 min, respectively. Autoverification systems using a Mindray BC-6800 auto hematology analyzer and labXpert were confirmed as being effective in reducing TAT and enhancing working efficiency on the premise of ensuring low false negative rate.

Oxygen vacancy diffusion in bare ZnO nanowires

Oxygen vacancies (VO) are known to be common native defects in zinc oxide (ZnO) and to play important roles in many applications. Based on density functional theory, we present a study for the migration of oxygen vacancies in ultra-thin ZnO nanowires (NWs). We find that under equilibrium growth conditions VO has a higher formation energy (Ef) inside the wire than that at shallow sites and surface sites, with different geometric relaxations and structural reconstructions. The migration of VO has lower barriers in the NW than in the bulk and is found to be energetically favorable in the direction from the bulk to the surface. These results imply a higher concentration of VO at surface sites and also a relative ease of diffusion in the NW structure. Our results support the previous experimental observations and are important for the development of ZnO-based devices in photocatalysis and optoelectronics.

Combination of B-lynch and modified Cho sutures for postpartum hemorrhage caused by low-lying placenta and placenta accreta

Many types of uterine packing are attempted to control PPH, including B-Lynch suture, Cho's suture, and so on. A female PPH caused by a low-lying placenta and placenta accreta did not respond to bimanual compression massage, administration of oxytocin and prostaglandins. A combination of B-Lynch with a modified Cho suture were tried to manage the PPH and succeeded. Combining sutures of B-Lynch with a modified Cho suture not only effectively manage PPH but also conserve the uterus, and avoid infection or adhesions of the endometria and empyema in the cavity of uterus.

Cloning, expression, and purification of a thermostable nonhomodimeric restriction enzyme, BslI

BslI is a thermostable type II restriction endonuclease with interrupted recognition sequence CCNNNNN/NNGG (/, cleavage position). The BslI restriction-modification system from Bacillus species was cloned and expressed in Escherichia coli. The system is encoded by three genes: the 2,739-bp BslI methylase gene (bslIM), the bslIRalpha gene, and the bslIRbeta gene. The alpha and beta subunits of BslI can be expressed independently in E. coli in the absence of BslI methylase (M.BslI) protection. BslI endonuclease activity can be reconstituted in vitro by mixing the two subunits together. Gel filtration chromatography and native polyacrylamide gel electrophoresis indicated that BslI forms heterodimers (alphabeta), heterotetramers (alpha(2)beta(2)), and possibly oligomers in solution. Two beta subunits can be cross-linked by a chemical cross-linking agent, indicating formation of heterotetramer BslI complex (alpha(2)beta(2)). In DNA mobility shift assays, neither subunit alone can bind DNA. DNA mobility shift activity was detected after mixing the two subunits together. Because of the symmetric recognition sequence of the BslI endonuclease, we propose that its active form is alpha(2)beta(2). M.BslI contains nine conserved motifs of N-4 cytosine DNA methylases within the beta group of aminomethyltransferase. Synthetic duplex deoxyoligonucleotides containing cytosine hemimethylated or fully methylated at N-4 in BslI sites in the first or second cytosine are resistant to BslI digestion. C-5 methylation of the second cytosine on both strands within the recognition sequence also renders the site refractory to BslI digestion. Two putative zinc fingers are found in the alpha subunit of BslI endonuclease.

Cloning and expression of the ApaLI, NspI, NspHI, SacI, ScaI, and SapI restriction-modification systems in Escherichia coli

The genes encoding the ApaLI (5'-GTGCAC-3'), NspI (5'-RCATGY-3'), NspHI (5'-RCATGY-3'), SacI (5'-GAGCTC-3'), SapI (5'-GCTCTTCN1-3', 5'-N4GAAGAGC-3') and ScaI (5'-AGTACT-3') restriction-modification systems have been cloned in E. coli. Amino acid sequence comparison of M.ApaLI, M.NspI, M.NspHI, and M.SacI with known methylases indicated that they contain the ten conserved motifs characteristic of C5 cytosine methylases. NspI and NspHI restriction-modification systems are highly homologous in amino acid sequence. The C-termini of the NspI and NlaIII (5'-CATG-3') restriction endonucleases share significant similarity. 5mC modification of the internal C in a SacI site renders it resistant to SacI digestion. External 5mC modification of a SacI site has no effect on SacI digestion. N4mC modification of the second base in the sequence 5'-GCTCTTC-3' blocks SapI digestion. N4mC modification of the other cytosines in the SapI site does not affect SapI digestion. N4mC modification of ScaI site blocks ScaI digetion. A DNA invertase homolog was found adjacent to the ApaLI restriction-modification system. A DNA transposase subunit homolog was found upstream of the SapI restriction endonuclease gene.

Nucleotide sequence of a small plasmid isolated from Acetobacter pasteurianus

A 1440-bp plasmid named pAP12875 was isolated from Acetobacter pasteurianus and its nucleotide sequence determined. An open reading frame was found capable of coding for a protein that has similarity with the replication protein of pVT736-1 from Actinobacillus actinomycetemcomitans and the 32-kDa protein of phage Pf3 from Pseudomonas aeruginosa.

The 'endo-blue method' for direct cloning of restriction endonuclease genes in E. coli

A new E. coli strain has been constructed that contains the dinD1::LacZ+ fusion and is deficient in methylation-dependent restriction systems (McrA-, McrBC-, Mrr-). This strain has been used to clone restriction endonuclease genes directly into E. coli. When E. coli cells are not fully protected by the cognate methylase, the restriction enzyme damages the DNA in vivo and induces the SOS response. The SOS-induced cells form blue colonies on indicator plates containing X-gal. Using this method the genes coding for the thermostable restriction enzymes Taql (5'TCGA3') and Tth111l (5'GACNNNGTC3') have been successfully cloned in E. coli. The new strain will be useful to clone other genes involved in DNA metabolism.

Suppression of tumorigenicity of a Wilms' tumor cell line is associated with a decrease in synthesis of two proteins

Wilms' tumor has been associated with deletions in two loci on chromosome 11, and the introduction of a translocated human chromosome [t(X;11)] into a Wilms' tumor cell line (G401.6TG.6) by microcell hybridization suppresses tumor formation in nude mice. The tumorigenic phenotype is restored in segregants of these microcell hybrids, in which the introduced chromosome is lost. We have used ultrahigh-resolution 'giant' two-dimensional gel electrophoresis of metabolically labeled cellular proteins and in vitro translation products of isolated mRNA to identify changes in cellular gene expression that occur in these cell lines. The changes in gene expression associated with these chromosomal manipulations per se are quite minimal. However, we have identified two proteins (p16 and p28) whose synthesis is consistently decreased in three non-tumorigenic (suppressed) microcell hybrid clones relative to parental and segregant tumorigenic lines. They are also decreased at the level of mRNA in at least two of the non-tumorigenic clones. The decrease of these proteins represents markers of the suppressed phenotype, and their down-regulation may conceivably mediate the suppression of tumorigenicity.