Dose-response relationship between risk factors and incidence of COVID-19 in 325 hospitalized patients: A multicenter retrospective cohort study

BACKGROUND

The epidemiological and clinical characteristics of coronavirus disease 2019 (COVID-19) patients have been widely reported, but the assessment of dose-response relationships and risk factors for mortality and severe cases and clinical outcomes remain unclear.

AIM

To determine the dose-response relationship between risk factors and incidence of COVID-19.

METHODS

In this retrospective, multicenter cohort study, we included patients with confirmed COVID-19 infection who had been discharged or had died by February 6, 2020. We used multivariable logistic regression and Cox proportional hazard models to determine the dose-response relationship between risk factors and incidence of COVID-19.

RESULTS

It clarified that increasing risk of in-hospital death were associated with older age (HR: 1.04, 95%CI: 1.01-1.09), higher lactate dehydrogenase [HR: 1.04, 95% confidence interval (CI): 1.01-1.10], C-reactive protein (HR: 1.10, 95%CI: 1.01-1.23), and procalcitonin (natural log-transformed HR: 1.88, 95%CI: 1.22-2.88), and D-dimer greater than 1 μg/mL at admission (natural log transformed HR: 1.63, 95%CI: 1.03-2.58) by multivariable regression. D-dimer and procalcitonin were logarithmically correlated with COVID-19 mortality risk, while there was a linear dose-response correlation between age, lactate dehydrogenase, D-dimer and procalcitonin, independent of established risk factors.

CONCLUSION

Higher lactate dehydrogenase, D-dimer, and procalcitonin levels were independently associated with a dose-response increased risk of COVID-19 mortality.

Upregulated circZMIZ1 promotes the proliferation of prostate cancer cells and is a valuable marker in plasma

Increasing evidences have proved that circular RNAs (circRNAs), identified as a specific kind of non-coding RNAs, play a potential critical role in tumorigenesis including prostate cancer. However, the function of circRNAs in human prostate cancer remain largely unknown. In this study, we demonstrated that the expression of circZMIZ1 was higher in plasma of human prostate cancer than the paired benign prostatic hyperplasia (BPH) patients' plasma. Moreover, in cultured prostate cancer cells, knockdown of circZMIZ1 inhibited cell proliferation and caused cell cycle arrest at G1. Mechanistically, we also showed that circZMIZ1 could increase the expression of androgen receptor (AR) and androgen receptor splice variant 7 (AR-V7), which may be partly contributed to the occurrence and development of prostate cancer. In conclusion, these results revealed that circZMIZ1 might serve as a novel biomarker and a treatment target for prostate cancer treatment.

Comparative analysis of the male inflorescence transcriptome profiles of an ms22 mutant of maize

In modern agricultural production, maize is the most successful crop utilizing heterosis. 712C-ms22 is an important male sterile material in maize. In this study, we performed transcriptome sequencing analysis of the V10 stage of male inflorescence. Through this analysis, 27.63 million raw reads were obtained, and trimming of the raw data revealed 26.63 million clean reads, with an average match rate of 94.64%. Using Tophat software, we matched these clean reads to the maize reference genome. The abundance of 39,622 genes was measured, and 35,399 genes remained after filtering out the non-expressed genes across all the samples. These genes were classified into 19 categories by clusters of orthologous groups of protein annotation. Transcriptome sequencing analysis of the male sterile and fertile 712C-ms22 maize revealed some key DEGs that may be related to metabolic pathways. qRT-PCR analysis validated the gene expression patterns identified by RNA-seq. This analysis revealed some of the essential genes responsible for pollen development and for pollen tube elongation. Our findings provide useful markers of male sterility and new insights into the global mechanisms mediating male sterility in maize.

The single nucleotide polymorphism rs700518 is an independent risk factor for metabolic syndrome and benign prostatic hyperplasia (MetS-BPH)

Studies have shown that 48.59% of benign prostate hyperplasia (BPH) is combined with metabolic syndrome (MetS). The mainstream view supports the correlation between MetS and BPH, but the pathogenesis of MetS‐BPH is not fully understood. Four hundred and seventy‐four men, aged 47 years or older, were recruited into this study by consecutive routine physical examination programs, and several parameters were obtained from each participant. Based on the diagnosis of BPH, MetS, and MetS‐BPH, the participants were divided into BPH and Non‐BPH groups, MetS and Non‐MetS groups, as well as MetS‐BPH and Non‐MetS‐BPH groups. The values of the obtained parameters were evaluated using Student's t‐test, chi‐square test, and logistic regression analysis. The value of estradiol (E2) was higher in the diseased groups (BPH, MetS, and MetS‐BPH groups) compared with the corresponding control groups (Non‐BPH, Non‐MetS, and Non‐MetS‐BPH groups), and the differences were statistically significant. Also, E2 had an independent association with BPH (OR = 2.286, 95% CI: 1.723–3.593, p < 0.001), MetS (OR = 1.406, 95% CI: 0.585–2.315, p < 0.001), and MetS‐BPH (OR = 1.249, 95% CI: 0.795–1.962, p < 0.001). Regarding SNPs of CYP19A1 gene, both the rs4646 genotypes (CC, CA, and AA) and the rs700518 genotypes (CC, CT, and TT) were present in every group, and all genotypes had statistically significant differences between the diseased and corresponding control groups. However, only the TT genotype of rs700518 was independently associated with BPH, MetS, and MetS‐BPH after adjusting for age. The TT genotype of rs700518 is an independent risk factor for the MetS‐BPH populations, and the CYP19A1 gene regulation of estrogen leads to MetS‐BPH.

Differences in expression of YKL-40 and TLR4 in nasal sinus mucosa of chronic sinusitis patients with and without nasal polyps

This work studies the expression differences of YKL-40 and TLR4 in nasal sinus mucosa of chronic sinusitis patients with and without nasal polyps and its clinical significances. Fifty chronic sinusitis patients with nasal polyps and 50 chronic sinusitis patients without, accepted by our hospital during February 2016-February 2017, were included and taken as group A and group B, respectively. In addition, another 50 patients with nasal deviation were taken as group C (control group). The ostiomeatal complex mucosa of group A and B and the inferior turbinate mucosa of group C were taken and the fluorescence quantitative PCR method was applied to detect the expression of YKL-40, TLR4 and NF- κB of the mucosa and explore and influence of YKL-40 and TLR4 on NF-κB. There was a negative correlation between YKL-40 and TLR4 in group A, and the difference was statistically significant (P less than 0.05) while there was no relationship between YKL-40 and TLR4 expression in group B. The level of YKL-40 protein in group A was higher than that in group B, which was statistically significant (P less than 0.05). YKL-40 and TLR4 were positively correlated in group A while there was no correlation between YKL- 40 and TLR4 expression in group B. The expression of YKL-40, TLR4 and NF-κB in chronic sinusitis patients with nasal polyps was high. In addition, there was a negative correlation between YKL-40 and TLR4 expression in chronic sinusitis patients with nasal polyps. YKL-40 and TLR4 interacted with each other to activate NF-κB and promote disease progression.

Fluoride content of tank water in Australia

BACKGROUND

The aims of this study were to: (1) analyse the fluoride content of tank water; (2) determine whether the method of water collection or storage influenced fluoride content; and (3) survey participant attitudes towards water fluoridation.

METHODS

Plastic tubes and a questionnaire were distributed through dentists to households with water tanks in Victoria. A midstream tank water sample was collected and fluoride analysed in triplicate using ion chromatography

RESULTS

All samples (n = 123) contained negligible amounts of fluoride, with a mean fluoride concentration of <0.01 ppm (range: <0.01-0.18 ppm). No statistically significant association was found between fluoride content and variables investigated such as tank material, tank age, roof material and gutter material. Most people did not know whether their tank water contained fluoride and 40.8% preferred to have access to fluoridated water. The majority thought fluoride was safe and more than half of the respondents supported fluoridation. Fluoride content of tank water was well below the optimal levels for caries prevention.

CONCLUSIONS

People who rely solely on tank water for drinking may require additional exposure to fluoride for optimal caries prevention.

Retroviral transduction of human dihydropyrimidine dehydrogenase cDNA confers resistance to 5-fluorouracil in murine hematopoietic progenitor cells and human CD34+-enriched peripheral blood progenitor cells

Severe 5-fluorouracil (5-FU) toxicity has been reported among patients lacking dihydropyrimidine dehydrogenase (DPD) enzymatic activity. DPD is the principal enzyme involved in the degradation of 5-FU to 5'-6'-dihydrofluorouracil, which is further metabolized to fluoro-beta-alanine. We demonstrate here that overexpression of human DPD confers resistance to 5-FU in NIH3T3 cells, mouse bone marrow cells, and in human CD34+-enriched hematopoietic progenitor cells. An SFG-based dicistronic retroviral vector containing human DPD cDNA, an internal ribosomal entry site (IRES), and the neomycin phosphotransferase (Neo) gene was constructed (SFG-DPD-IRES-Neo). Transduced NIH3T3 cells demonstrated a 2-fold (ED50) increase in resistance to a 4-hour exposure of 5-FU in comparison to nontransduced cells. Expression of DPD was confirmed by Northern and Western blot analyses, and DPD enzyme activity was detectable only in transduced cells. Infection of mouse bone marrow cells with this retroviral construct resulted in an increased number of 5-FU-resistant CFU-GM colonies, compared to mock-transduced bone marrow in both 4-hour and 12- to 14-day exposures. Infection of human CD34+-enriched cells with this construct and incubation with 5-FU (10(-6) M) for 14 days also resulted in an increased number of 5-FU-resistant colonies. Retroviral transduction of human hematopoietic progenitor cells with a cDNA-expressing human DPD conferred resistance to 5-FU in NIH3T3 cells, mouse bone marrow cells, and human CD34+-enriched cells. These results encourage the use of this gene as a method to protect patients from 5-FU myelotoxicity.

Antitumor activity of cytotropic heterogeneous molecular lipids (CHML) on human breast cancer xenograft in nude mice

Cytotropic heterogeneous molecular lipid (CHML), which is a new anticancer agent with US patent number 5,260,067, has recently been shown to suppress tumor cell growth in multiple tumor lines and induce apoptosis in vitro (1). These results indicate that CHML may be an effective antitumor agent. In the present study, using both local injection and intravenous injection, we have investigated the suppressive effect of CHML on human breast caner cells MCF-7 xenograft in nude mice. In the local injection, CHML was introduced into nude mice implanted with human breast cancer xenograft at doses of 25 mg/tumor area (cm2), 35 mg/tumor area (cm2), or 50 mg/tumor area (cm2), once every two days, total 3 times. The inhibition of tumor growth was 81.3%, 93.8% and 100%, respectively. In the intravenous injection, the nude mice bearing MCF-7 xenografts were treated with CHML at 10 mg/kg/day, or 15 mg/kg/day, or 20 mg/kg/day, once a day, total 7 days, the growth inhibition of tumor area was 58.1%, 77.4%, and 83.9%, respectively. At the same time, the toxicity of CHML was determined through examining the number of the white blood cell (WBC) and the activity of the serum glutamic-pyruvic transaminase (SGPT). However, no evident alterations of WBC and SGPT were detected in all animals treated with CHML, suggesting that CHML has little toxicity on nude mice. Taken together, these results indicate that CHML is an effective agent that suppresses breast tumor growth and suggest the possibility of using CHML in the clinical trial in the near future.

Generation of dual resistance to 4-hydroperoxycyclophosphamide and methotrexate by retroviral transfer of the human aldehyde dehydrogenase class 1 gene and a mutated dihydrofolate reductase gene

The genetic transfer of drug resistance to hematopoietic cells is an attractive approach to overcoming myelosuppression caused by high-dose chemotherapy. Because cyclophosphamide (CTX) and methotrexate (MTX) are commonly used non-cross-resistant drugs, generation of dual drug resistance in hematopoietic cells that allows dose intensification may increase anti-tumor effects and circumvent the emergence of drug-resistant tumors. We constructed a retroviral vector containing both a human cytosolic ALDH-1 cDNA and a human doubly mutated DHFR cDNA (Phe22/Ser31; termed F/S in the description of constructs) to generate increased resistance to both CTX and MTX. Infection of NIH3T3 cells resulted in increased resistance to both 4-hydroperoxycyclophosphamide (4HC) (1.9 +/- 0.1-fold) and MTX (73 +/- 2.8-fold). Transduced human CD34(+) enriched hematopoietic progenitor cells were also resistant to both 4HC and MTX by CFU-GM readout. Lethally irradiated mice transplanted with SFG-ALDH-IRES-F/S or mock-transduced bone marrow cells were treated with high-dose pulse CTX or high-dose CTX/MTX. Animals receiving marrow not transduced with ALDH-1 or mutated DHFR cDNA died from CTX or CTX/MTX toxicity, whereas mice transduced with ALDH-1 and mutated DHFR cDNA-containing marrow were able to tolerate the same doses of CTX or CTX/MTX treatment posttransplant. These data taken together indicate that ALDH-1 overexpression and mutant DHFR increased both 4HC and MTX resistance in vitro and in the in vivo mouse model. This construct may be useful for protecting patients from high-dose CTX- and MTX-induced myelosuppression.

Groucho/TLE/R-esp proteins associate with the nuclear matrix and repress RUNX (CBF(alpha)/AML/PEBP2(alpha)) dependent activation of tissue-specific gene transcription

The Runt related transcription factors RUNX (AML/CBF(alpha)/PEBP2(alpha)) are key regulators of hematopoiesis and osteogenesis. Using co-transfection experiments with four natural promoters, including those of the osteocalcin (OC), multi drug resistance (MDR), Rous Sarcoma Virus long terminal repeat (LTR), and bone sialoprotein (BSP) genes, we show that each of these promoters responds differently to the forced expression of RUNX proteins. However, the three RUNX subtypes (i.e. AML1, AML2, and AML3) regulate each promoter in a similar manner. Although the OC promoter is activated in a C terminus dependent manner, the MDR, LTR and BSP promoters are repressed by three distinct mechanisms, either independent of or involving the AML C terminus, or requiring only the conserved C-terminal pentapeptide VWRPY. Using yeast two hybrid assays we find that the C terminus of AML1 interacts with a Groucho/TLE/R-esp repressor protein. Co-expression assays reveal that TLE proteins repress AML dependent activation of OC gene transcription. Western and northern blot analyses suggest that TLE expression is regulated reciprocally with the levels of OC gene expression during osteoblast differentiation. Digital immunofluorescence microscopy results show that TLE1 and TLE2 are both associated with the nuclear matrix, and that a significant subset of each colocalizes with AML transcription factors. This co-localization of TLE and AML proteins is lost upon removing the C terminus of AML family members. Our findings indicate that suppression of AML-dependent gene activation by TLE proteins involves functional interactions with the C terminus of AML at the nuclear matrix in situ. Our data are consistent with the concept that the C termini of AML proteins support activation or repression of cell-type specific genes depending on the regulatory organization of the target promoter and subnuclear localization.

Comparison of methotrexate resistance conferred by a mutated dihydrofolate reductase (DHFR) cDNA in two different retroviral vectors

We previously reported the protection of hematopoietic cells from methotrexate (MTX) toxicity using an N2-based double copy vector containing serine 31 (S31)-mutated dihydrofolate reductase (DHFR) (DC/SV6S31). To examine whether the use of SFG-based dicistronic vectors will lead to improvement in gene transfer over the DC/SV6 vector, we compared the protection provided by MTX to NIH3T3 cells and hematopoietic progenitor cells infected with these retroviral constructs containing the S31 variant DHFR cDNA. In NIH3T3 cells, the 50% effective dose values of MTX conferred by the SFG vector were 8-fold higher than those obtained with the DC/SV6 vector. DHFR mRNA levels were 22-fold and 38-fold higher than that seen for the DC/SV6 vector according to Northern blot and real-time polymerase chain reaction analysis, respectively. However, DHFR protein expression and DHFR enzyme activity were only 1.5-fold and 2-fold higher in the SFG vector, respectively, indicating that the mRNA from the SFG vector is translated less efficiently than the mRNA generated from the DC/SV6 vector. Furthermore, the degree of MTX protection conferred by each vector in both mouse and human hematopoietic cells was the same. These results indicate that the in vitro transduction efficiency and transgene expression of human DHFR in hematopoietic progenitor cells is equally conferred by both vectors.

Expression of a novel double-mutant dihydrofolate reductase-cytidine deaminase fusion gene confers resistance to both methotrexate and cytosine arabinoside

A novel fusion gene consisting of the open reading frame of a double-mutant (Phe22-Ser31) dihydrofolate reductase (dmDHFR) cDNA fused to the open reading frame of cytidine deaminase (CD) was constructed and characterized for the purpose of conferring simultaneous resistance to methotrexate (MTX) and cytosine arabinoside (ara-C). The kinetic properties of purified recombinant dmDHFR-CD fusion protein were compared with those of purified CD and dmDHFR. The fusion protein was found to retain enzymatic properties of both dmDHFR and CD, in that the Km and Kcat values of purified dmDHFR-CD protein were found to be virtually identical to those of CD and dmDHFR alone. Retrovirus-mediated expression of dmDHFR-CD in NIH 3T3 cells conferred significant resistance (10- to 12-fold) against MTX and ara-C, compared with mock- and single gene-infected cells and the level of resistance obtained was similar to that of cells expressing both CD and dmDHFR from a retroviral bicistronic vector. Infection of mouse bone marrow cells with the dmDHFR-CD construct also showed high levels of resistance to MTX and ara-C in a CFU-GM assay. This fusion protein confers resistance to two antineoplastic agents that differ in their mechanism of action, and may be useful in the design of gene transfer strategies for protection of target cells against multiple drugs. Since high-dose ara-C and MTX are used in the treatment of lymphomas, this vector may be of value in protecting human hematopoietic progenitor cells from the toxicity of these antimetabolites.

Probing the folate-binding site of human thymidylate synthase by site-directed mutagenesis. Generation of mutants that confer resistance to raltitrexed, Thymitaq, and BW1843U89

Human thymidylate synthase (TS) contains three highly conserved residues Ile-108, Leu-221, and Phe-225 that have been suggested to be important for cofactor and antifolate binding. To elucidate the role of these residues and generate drug-resistant human TS mutants, 14 variants with multiple substitutions of these three hydrophobic residues were created by site-directed mutagenesis and transfected into mouse TS-negative cells for complementation assays and cytotoxicity studies, and the mutant proteins expressed and characterized. The I108A mutant confers resistance to raltitrexed and Thymitaq with respective IC50 values 54- and 80-fold greater than wild-type but less resistance to BW1843U89 (6-fold). The F225W mutant displays resistance to BW1843U89 (17-fold increase in IC50 values), but no resistance to raltitrexed and Thymitaq. It also confers 8-fold resistance to fluorodeoxyuridine. Both the kinetic characterization of the altered enzymes and formation of antifolate-resistant colonies in mouse bone marrow cells that express mutant TS are in accord with the IC50 values for cytotoxicity noted above. The human TS mutants (I108A and F225W), by virtue of their desirable properties, including good catalytic function and resistance to antifolate TS inhibitors, confirm the importance of amino acid residues Ile-108 and Phe-225 in the binding of folate and its analogues. These novel mutants may be useful for gene transfer experiments to protect hematopoietic progenitor cells from the toxic effects of these drugs.

Role of E2F-1 in chemosensitivity

The E2F family of transcription factors, in partnership with DP proteins, is thought to regulate transcription of genes that encode protein products that are required for DNA synthesis, which include important cancer chemotherapeutic targets such as thymidylate synthase and dihydrofolate reductase. This study was conducted to investigate the effects of overexpression of human E2F-1 cDNA on chemosensitivity in a human fibrosarcoma cell line, HT-1080. The E2F-1-overexpressing HT-1080 cells had a shorter doubling time both in vitro and in vivo. Associated with an up-regulation of TS, E2F-1-transfected cells were more resistant to 5-fluorouracil than were untransfected cells. These E2F-1 transfectants, although resistant to fluoropyrimidines and serum deprivation, were more sensitive to etoposide, doxorubicin, and SN38 (the active metabolite of irinotecan) but not to Taxol.

Isolation and characterization of thymitaq (AG337) and 5-fluoro-2-deoxyuridylate-resistant mutants of human thymidylate synthase from ethyl methanesulfonate-exposed human sarcoma HT1080 cells

Thymidylate synthase plays an essential role in the synthesis of DNA. Recently, several new and specific thymidylate synthase inhibitors that occupy the folate binding site, including Tomudex(R), BW1843U89, and Thymitaq, have demonstrated therapeutic activity in patients with advanced cancer. In order to find drug-resistant forms of human thymidylate synthase for gene therapy applications, human sarcoma HT1080 cells were exposed to ethyl methanesulfonate and Thymitaq selection. Thymitaq-resistant clonal derived sublines were established, and analysis indicated that both gene amplification and point mutations contributed to drug resistance. Eight mutant cDNAs that were identified from Thymitaq-resistant sublines were generated by site-directed mutagenesis and transfected into thymidylate synthase-negative cells. Only K47E, D49G, or G52S mutants retain enzyme activity. Moreover, cytotoxicity studies demonstrated that D49G and G52S transfected cells, besides displaying resistance to Thymitaq with IC50 values 40- and 12-fold greater than wild-type enzyme transfected cells, respectively, also lead to fluorodeoxyuridine resistance (26- and 97-fold in IC50 values, respectively) but not to Tomudex or BW1843U89. Characterization of the purified altered enzymes obtained from expression in Escherichia coli is consistent with the cell growth inhibition results. We postulate that the D49G or G52S mutation leads to the structural perturbation of the highly conserved Arg50 loop, decreasing the binding of thymidylate synthase to the inhibitors, Thymitaq and fluorodeoxyuridylate.

Purine salvage rescue by xanthine-guanine phosphoribosyltransferase (XGPRT) potentiates methotrexate resistance conferred by transfer of a mutated dihydrofolate reductase gene

We have previously shown that successful gene transfer of a mutated dihydrofolate reductase (DHFR) cDNA confers resistance to methotrexate (MTX) upon infected cells. We constructed a retrovirus vector, DC/SV6S31GPT, which carries both the Escherichia coli xanthine-guanine phosphoribosyltransferase gene and the mutated Serine 31 DHFR gene. Mouse fibroblast NIH3T3 cells infected with DC/SV6S31 GPT are more resistant to MTX than cells infected with DC/SV6S31, which carries the Serine 31 DHFR and the neomycin resistance gene cDNA. The mechanism of this augmented resistance is the increased salvaging of purines due to expression of xanthine-guanine phosphoribosyltransferase, as the augmentation does not occur when dialyzed serum, containing little xanthine or guanine, is used for cytotoxicity assays. These results indicate that coexpression of a metabolically related gene can potentiate the resistance carried by a drug resistance gene. This vector may be useful in clinical gene therapy to protect bone marrow from the toxic effects of MTX.

Co-expression of the herpes simplex virus thymidine kinase gene potentiates methotrexate resistance conferred by transfer of a mutated dihydrofolate reductase gene

We have previously shown that transfer of a mutated dihydrofolate reductase (DHFR) confers resistance to methotrexate (MTX) to infected cells. We report herein the construction of a retrovirus vector, DC/SV6S31tk, which carries the herpes simplex virus thymidine kinase gene (HSVtk) as well as the mutated Serine 31 DHFR (S31) cDNA. 3T3 cells infected with DC/SV6S31tk are more resistant to MTX than cells infected with DC/SV6S31, which carries the S31 and Neo gene. In DC/SV6S31tk-infected cells, a fraction of cells (20-40%) were more resistant to MTX compared with DC/SV6S31-infected cells, and these cells survived a 5-day exposure to 200 microM of MTX. The mechanism of this augmented resistance is attributed to the salvage of thymidine by HSVtk, as the augmentation is reversed when dialyzed serum is used for cytotoxicity assays. The cells that survive high-dose MTX selection have high levels of expression of S31 DHFR and HSVtk, although copy numbers of the proviral sequences do not increase significantly. Transduction of cells with the DC/SV6S31tk vector also sensitizes cells to ganciclovir (GCV). Co-expression of a metabolically related gene in a retroviral vector to potentiate the resistance imparted by a drug resistance gene may be useful for gene therapy for cancer patients.

Post-transplant methotrexate administration leads to improved curability of mice bearing a mammary tumor transplanted with marrow transduced with a mutant human dihydrofolate reductase cDNA

To test the concept that protection of bone marrow progenitor cells via introduction of a drug resistance gene would allow larger and curative doses of chemotherapy to be administered, we used mice bearing a transplanted breast cancer as a model system. Mice bearing the E0771 tumor were treated with lethal doses of cyclophosphamide (CPA) and rescued from toxicity by administration of bone marrow transduced with a mutant dihydrofolate reductase (DHFR) cDNA (Ser-31) in a retroviral construct. Animals receiving marrow not transduced with mutant DHFR cDNA died from methotrexate (MTX) toxicity, whereas mice transduced with mutant DHFR cDNA containing marrow were able to tolerate MTX treatment post-transplant; 44% of the mice had no demonstrable tumor when sacrificed on day 52. Another control group of mice treated with CPA and transplanted but not treated with MTX post-transplant succumbed to tumor regrowth. These data provide a strong rationale for the use of drug resistance genes to protect marrow from drug toxicity because the increase in dose tolerated may result in an improved cure rate of chemosensitive tumors.

Transfection of a nonactive site mutant murine DHFR cDNA (the tryptophan 15 mutant) into Chinese hamster ovary and mouse marrow progenitor cells imparts MTX resistance in vitro

Chinese hamster ovary (CHO) DHFR-cells were converted to the DHFR+ (dihydrofolate reductase) phenotype when transfected with a mammalian expression vector containing the murine mutant Trp15 DHFR cDNA. Transfection of the Trp15 DHFR cDNA into wild-type CHO cells resulted in resistance to high levels of methotrexate (MTX) in vitro indicating that this mutant DHFR cDNA can act as a dominant marker. Southern and Northern blot analyses of transfected cells indicated that the transfected mutant DHFR cDNA was integrated and expressed. Gene copy number analysis showed that the Trp15 cDNA was amplifiable in increasing concentrations of MTX. Transfection of murine bone marrow progenitor cells with the Trp15 mutant DHFR cDNA resulted in MTX resistant colony forming units-granulocyte macrophage.

Gene therapy utilizing drug resistance genes: a review

The generation of drug resistant bone marrow may facilitate the development of aggressive chemotherapeutic regimens that might otherwise be lethal due to marrow toxicity. With the availability of technology that permits in vitro manipulation of human marrow and peripheral blood stem cells, it is now possible to introduce genes that confer drug resistance to these hematopoietic progenitors. Animal models and in vitro work with human progenitors using drug resistance genes are reviewed.

Development of a retroviral construct containing a human mutated dihydrofolate reductase cDNA for hematopoietic stem cell transduction

A double-copy Moloney leukemia virus-based retroviral construct containing both the NeoR gene and a mutant human dihydrofolate reductase (DHFR) cDNA (Ser31 mutant) was used to transduce NIH 3T3 and mouse bone marrow (BM) progenitor cells. This resulted in increased resistance of these cells to methotrexate (MTX). The transduced BM progenitor cells were returned to lethally irradiated mice. The recipients transplanted with marrow cells infected with the recombinant virus showed protection from lethal MTX toxicity as compared with mock-infected animals. Evidence for integration of the proviral DNA was obtained by amplification of proviral DNA by polymerase chain reaction (PCR) and Southern analysis. Sequencing a portion of the PCR-amplified human DHFR cDNA showed the presence of the mutation. These studies with the human Ser31 mutant DHFR cDNA gave results comparable with those obtained with the mutant murine DHFR cDNA (Leu to Arg22) in developing MTX-resistant BM. The Ser31 mutant human DHFR cDNA is currently being tested for infection of human CD34+ human BM and peripheral blood stem cells in vitro.

Long-term protection of recipient mice from lethal doses of methotrexate by marrow infected with a double-copy vector retrovirus containing a mutant dihydrofolate reductase

A double-copy Moloney murine leukemia virus-based retroviral construct containing both the NEOr gene and a mutated dihydrofolate reductase cDNA (Leu 22-->Arg) was used to infect mouse bone marrow cells. The infected mouse marrow was returned to lethally irradiated mice. Primary, secondary, and even tertiary recipients transplanted with bone marrow cells infected with the recombinant virus showed protection from lethal methotrexate toxicity. The viral construct containing a SV-40 promoter in the U3 region of the 3' long terminal repeat appeared to be more effective than a similar construct containing the adenosine deaminase promoter, although both afforded protection. Evidence for integration into blood cells of both the NEOr gene and the mutated dihydrofolate reductase gene was obtained by polymerase chain reaction; sequencing of the amplified dihydrofolate reductase cDNA showed the presence of the point mutation. These results indicate that early hematopoietic progenitor cells in the mouse can be successfully transduced with a drug resistance gene.

Transfection with a cDNA encoding a Ser31 or Ser34 mutant human dihydrofolate reductase into Chinese hamster ovary and mouse marrow progenitor cells confers methotrexate resistance

Chinese hamster ovary (CHO) DHFR- cells were converted into the DHFR+ phenotype when they were transfected with a mammalian expression vector carrying human dihydrofolate reductase-encoding cDNAs (DHFR) containing a Ser31 or a Ser34 mutation. Furthermore, transfection of these mutants into wild-type CHO cells resulted in resistance to high levels of methotrexate (MTX), indicating that these human variants can act as dominant selectable markers. Southern blot analysis and polymerase chain reaction amplifications confirmed that the transfected plasmids were integrated into the CHO DNA. Gene copy number analysis revealed that both the Ser3 1 and the Ser3.4 mutants amplifiable when grown in increasing concentrations of MTX. Retrovirus-mediated gene transfer of the Ser31 mutant into mouse marrow progenitor cells also resulted in MTX-resistant CFU-GM (colony-forming unit-granulocyte macrophage) cells.

[The relation between the levels of serum lipid peroxide, superoxide dismutase and atrial natriuretic peptide in placenta, umbilical cord vein and intrauterine growth retardation in pregnancy induced hypertension]

This paper was written on the following base: 31 women with severe pregnancy induced hypertension (PIH) were chosen randomly as an observation group, 32 healthy and gestational age matched pregnant women with uneventful delivery were served as control group. Blood samples were collected from intervillous space of placenta and umbilical cord vein after delivery. The levels of LPO, SOD and atrial natriuretic peptide (ANP) were measured separately. From the placenta point of view, the pathogenic mechanism of PIH and the relation to the occurrence of intrauterine growth retardation (IUGR) were discussed. The results showed: the concentrations of LPO, SOD and ANP of placenta and umbilical cord vein were higher in the PIH group than that in the control group. The difference between 2 groups was statistically significant. A positive correlation between LPO and ANP was found both in PIH group and in control group (r = 0.641, P < 0.02). The birth weight of newborn was 2,174 +/- 142 g in PIH group and 3,460 +/- 187 g in control group. The difference between them was significant (P < 0.01). It suggested that the pathogenesis of PIH and the occurrence of IUGR might be closely related to the high concentration of LPO in placenta and umbilical cord vein.

Curative effects of highly active atrial natriuretic peptide on severe pregnancy-induced hypertension

A new highly active atrial natriuretic peptide (haANP), synthesized by a solid phase technique, was given by intravenous infusion to 20 patients with severe pregnancy-induced hypertension (PIH) and the curative result of haANP was observed. Compared with basal values, supine systolic and diastolic BP was lowered significantly (P < 0.01), which may be related to the specific receptor of hANP and inhibition of renin-angiotensin-aldosterone system (RAAS). The haANP was found to possess significant effects of antispasm, detumescence and reducing proteinuria, probably by repairing mildly injured glomerulae, strong effects of diuresis and improving heart function with no side effects. Auto-antibody of hANP was found in patients with severe PIH, which affected the function of target cells of highly concentrated endogenous hANP. This auto-antibody might be one of the causes for PIH.

Intravasal injection of formed-in-place silicone rubber as a method of vas occlusion

This report describes the procedure for percutaneous injection of silicone to form plugs in the vas deferens. The injection of 0.1-0.16 ml Chinese-made silicone into 14 men achieved occlusion of a 1-cm length of the vas. Sperm concentrations declined within 1 month of the operation and azoospermia was achieved in all men by 9 months.

Recovery of fertility after removal of polyurethane plugs from the human vas deferens occluded for up to 5 years

The present study reports the outcome of operations to remove MPU plugs from 130 men who had had occlusions of the vas deferens for between 0.5 and 5 years. The female partners of all the men achieved a pregnancy over a period of 0.5-4 years after the reversal operation.

Comparison of the expression of a mutant dihydrofolate reductase under control of different internal promoters in retroviral vectors

To determine the effect of different promoters on the expression of an altered dihydrofolate reductase (DHFR) gene conferring methotrexate (MTX) resistance in different cell types, double-copy retroviral vectors were constructed carrying a murine mutant DHFR under the control of five different promoters, i.e., human adenosine deaminase (ADA), simian virus 40 (SV40), thymidine kinase (TK), human beta-actin, and cytomegalovirus (CMV). Their expression was compared in NIH-3T3 cells, three human leukemia cell lines, and mouse bone marrow. The variant DHFR is readily expressed from these various promoters in retroviral vectors at a selectable level. In 3T3 cells, the DHFR constructs containing the SV40 promoter conferred the highest levels of resistance to MTX. In K562 and Raji cells, the construct with the TK promoter produced the highest level of resistance. However granulocyte-macrophage colony-forming unit (CFU-GM) colonies from mouse marrow were more resistant to MTX when infected with vectors containing the SV40 promoter and ADA promoter as compared to the other promoter constructs. These studies show that mouse fibroblast cell lines such as NIH-3T3 do not predict the effectiveness of retroviral-mediated gene transfer for marrow progenitor cells, and that the activity of retroviral vector-encoded promoters vary in an unpredictable manner from cell type to cell type. Possible implications for basic gene transfer studies and clinical applications are discussed.

Vas deferens occlusion by percutaneous injection of polyurethane elastomer plugs: clinical experience and reversibility

A non-incision method of vas occlusion based on the percutaneous injection of polyurethane elastomer solution to form plugs is described. The results are based on clinical experience in 12,000 men in which only 56 cases of minor complications were recorded. Follow-up of 500 men for up to 3 years demonstrated an azoospermia rate of 98%. Plugs have been removed from 86 men and, to date, 51 have made their wives pregnant. In those from which the plugs have been removed for more than 1 year (n = 31), the pregnancy rate is 100%.

Comparison of autoradiography and DNA histograms in assessing S-phase cells from patients with myeloid leukemias

The studies reported here were designed to determine whether DNA histogram analysis provided the same estimate for the percentage of cells in S-phase as does 3H-TdR labeling index (LI). For DNA histogram analysis high resolution flow cytometry was employed together with 3 different computer based methods for histogram analysis. When tissue culture cells were employed there was a good correlation (r = 0.89) between the estimates for the percentage of cells in S-phase by the LI and DNA histogram techniques. In contrast, when 1138 bone marrow or peripheral blood specimens obtained from leukemic patients were studied the correlation was poor. For example when 243 pretherapy bone marrow aspirate cells were studied by both methods the correlation was only 0.46. A direct comparison of the clinical relevance of the two methods for measuring S-phase cells when high dose cytosine arabinoside therapy was used to treat patients demonstrated that only LI measurements provided clinically useful information. In conclusion, DNA histogram analysis provides an inaccurate estimate of the percentage of cells in S-phase.

Improved rapid autoradiography with elimination of background

A method has been developed to improve the quality of autoradiography. In addition to using high specific activity thymidine (3HTdr), low temperature exposure and scintillation fluid, FdUR was added to the cell suspension during incubation. It led to an increased amount of 3HTdr incorporation by the cells. By this method, the grain density over positive cells was increased and the background was minimal.

Effects of cytosine arabinoside on DNA synthesis and mitotic activity of HL-60 cells

HL-60 cells were exposed to tritiated thymidine (3HTdR) alone (control group), to cytosine arabinoside followed by 3HTdR or to tritium labelled cytosine arabinoside (3H-AraC) for one hour followed by incubation with colcemide to arrest them during metaphase. Autoradiographic slides were prepared and cell counts were at 1, 24, 48 and 72 h. The studies demonstrated that HL-60 cells exposed to high concentrations of AraC (10 micrograms ml-1) can pass through the S-phase as the G2-phase of the cell cycle and enter mitosis. Despite completing the S-phase, the cells exposed to AraC were severely damaged and had already begun to die.