A new nucleophilic ring opening of an activated cyclopropane and a formal synthesis of (+/-)-carbovir

The reaction of bicyclo[3.1.0]hexane 1, possessing a doubly activated cyclopropane ring, with acetic acid and potassium acetate in DMSO proceeded smoothly to give the adduct 2 in good yield. A formal total synthesis of the potent anti-HIV agent (+/-)-carbovir (9) was done by converting 2 into a known precursor 8 in 8 steps via allyl alcohol 7 including the regioselective introduction of a double bond (4 to 5) and attachment of the nucleobase using the Mitsunobu reaction (7 to 8).

[A new technique of esophagogastrostomy above the aortic arch--covering and suspending of the anastomotic area with mediastinal pleura flap]

The postoperative anastomotic leakage is the most severe complication and the principal cause of death after resection of esophageal carcinoma. Especially, anastomosis above the aortic arch is accompanied by high incidence of anastomotic leakage usually with fatal prognosis. The authors improved the conventional method of anastomosis by using a mediastinal pleura flap to cover and suspend the anastomotic area with excellent result. From January of 1990 to April of 1995, 210 patients with esophageal carcinoma were so treated. No anastomotic leakage or stricture developed. Only one patient died of extensive myocardial infarction with an overall mortality of 0.47%. The major merit of this procedure was that the mediastinal pleura flap could cover the area of anastomosis and sustain the dragging force acting on this area, providing a better condition for the anastomosis to heal and thus reducing the possibility of anastomotic leakage.

Clinical application of monoclonal antibody-drug conjugate to immunotargeting chemotherapy of bladder cancer

Monoclonal antibody-drug conjugate was applied in a clinical trial for patients with bladder cancer. Monoclonal antibody HB7A from a mouse splenocyte immunized against human bladder cancer was used as a drug carrier. The anti-cancer drug adriamycin (ADR) was bound to HB7A through a dextran (DEX) bridge to form the conjugate HB7A-DEX-ADR. The in vitro cytotoxic effect of the conjugate on BIU-87 bladder cancer cells was similar to that of free ADR and the mixture of HB7A and ADR. Seven patients with bladder cancer were given HB7A-DEX-ADR intravenously. The immunoperoxidase studies of the resected specimens showed that HB7A was localized specifically in cancer, and histological studies revealed degenerative and necrotic changes of the tumor cells. Patients receiving the conjugate did not experience serious side effects. This study suggests that immunotargeting chemotherapy with HB7A-DEX-ADR is well tolerated by patients and its cytotoxicity on tumor is substantial.

p53 mutations in benign breast tissue

PURPOSE

Patients with benign breast biopsies that exhibit atypical epithelial proliferation or fibroadenoma may be at increased risk for invasive breast cancer. We hypothesized that molecular markers might also be useful to evaluate the malignant potential of nonneoplastic breast tissue.

PATIENTS AND METHODS

Study subjects belonged to a cohort of 6,805 women who underwent biopsy for nonmalignant breast disease at the Mayo Clinic and Rochester-affiliated hospitals between 1967 and 1981. As part of a nested case-control study that compared subjects who developed invasive breast cancer with those who did not, we analyzed a sample of 60 benign breast biopsies for the following markers: HER-2/neu and p53 over-expression by immunohistochemistry, HER-2/neu and PRAD-1 amplification using differential polymerase chain reaction (PCR), and p53 mutation using single-strand conformation analysis (SSCA) and direct DNA sequencing by asymmetric PCR.

RESULTS

None of 60 biopsies showed amplification of HER-2/neu or PRAD-1. Five samples exhibited low-level immunoreactivity to the HER-2/neu protein product. Fourteen samples exhibited focal or diffuse immunoreactivity to the p53 protein. Point mutations in the p53 gene were found in five samples: three of these samples exhibited mutations that altered the amino acid sequence. Only two of five samples with p53 mutation exhibited p53 overexpression. Histologic diagnoses on three samples with nonconservative p53 mutation were, respectively, nonproliferative fibrocystic change, papillomatous hyperplasia, and fibroadenoma.

CONCLUSION

The clinical significance of p53 mutation, p53 overexpression, and low-level HER-2/neu expression in benign breast tissue remains to be determined. Further research will be necessary to evaluate whether these markers could serve as useful adjuncts to histology in evaluation of the malignant potential of benign breast tissue.

Codon bias in actin multigene families and effects on the reconstruction of phylogenetic relationships

Codon usage patterns and phylogenetic relationships in the actin multigene family have been analyzed for three dipteran species--Drosophila melanogaster, Bactrocera dorsalis, and Ceratitis capitata. In certain phylogenetic tree reconstructions, using synonymous distances, some gene relationships are altered due to a homogenization phenomenon. We present evidence to show that this homogenization phenomenon is due to codon usage bias. A survey of the pattern of synonymous codon preferences for 11 actin genes from these three species reveals that five out of the six Drosophila actin genes show high degrees of codon bias as indicated by scaled chi 2 values. In contrast to this, four out of the five actin genes from the other species have low codon bias values. A Monte Carlo contingency test indicates that for those Drosophila actin genes which exhibit codon bias, the patterns of codon usage are different compared to actin genes from the other species. In addition, the genes exhibiting codon bias also appear to have reduced rates of synonymous substitution. The homogenization phenomenon seen in terms of synonymous substitutions is not observed for nonsynonymous changes. Because of this homogenization phenomenon, "trees" constructed based on synonymous substitutions will be affected. These effects can be overt in the case of multigene families, but similar distortions may underlie reconstructions based on single-copy genes which exhibit codon usage bias.

Inhibition of (S)-warfarin metabolism by sulfinpyrazone and its metabolites

Sulfinpyrazone markedly potentiates the anticoagulant effect of warfarin. The increased clotting time is accompanied by a marked decrease in the clearance of (S)-warfarin by virtue of a decrease in the P4502C9-catalyzed formation clearance to its major and inactive metabolite (S)-7-hydroxywarfarin. These data suggested that the mechanism of the drug interaction might be mediated through the inhibition of the catalytic activity of P4502C9 by sulfinpyrazone. However, initial human liver microsomal studies indicated that the in vitro Ki, for inhibition of (S)-7-hydroxywarfarin formation by sulfinpyrazone is at least 25-fold higher than the therapeutic concentration of sulfinpyrazone in vivo. This result implied that other inhibitors probably contribute to the interaction. Kinetic studies conducted on sulfinpyrazone and two major metabolites, sulfinpyrazone sulfide and sulfinpyrazone sulfone, in microsomes prepared from three human livers give mean Ki's of 230 microM, 17 microM, and 73 microM respectively. Because sulfinpyrazone and its sulfide metabolite attain comparable plasma concentrations during the course of therapy, our inhibition results suggest that the sulfide metabolite is likely to be the primary species responsible for the inhibition of P4502C9-catalyzed formation of (S)-7-hydroxywarfarin and the decrease in (S)-warfarin clearance in vivo.

[PCNA expression and AgNORs image analysis as factors in judging the prognosis of lung cancer]

The expression of PCNA and AgNORs count or AgNORs' area in 86 cases of primary lung cancer and 10 cases of inflammatory pseudotumor were studied by S-P immunostaining of monoclonal antibody (PC-10) and image analysis system. The results showed that the proliferating index (PI) of PCNA positive cells was closely related to AgNORs count and AgNORs' area measured. Both were correlated with the histological type, and the TNM status, decreased with the increasing degree of histological differentiation. Survival analysis showed that the PI and the results of AgNORs image analysis in surgical patients who survived over 5 years were significantly lower than those who survived less than 3 years. The results suggest that immunostaining of PCNA and AgNORs image analysis are useful in judging the malignant degree and the prognosis of primary lung cancer.

Engineering a metal binding site within a polytopic membrane protein, the lactose permease of Escherichia coli

Site-directed excimer fluorescence indicates that Glu269 (helix VIII) and His322 (helix X) in the lactose permease of Escherichia coli lie in close proximity [Jung, K., Jung, H., Wu, J., Privé, G.G., & Kaback, H.R. (1993) Biochemistry 32, 12273]. In this study, Glu269 was replaced with His in wild-type permease, leading to the presence of bis-His residues between helices VIII and X. Wild-type and Glu269-->His permease containing a biotin acceptor domain were purified by monomeric avidin affinity chromatography, and binding of Mn2+ was studied by electron paramagnetic resonance (EPR) spectroscopy. The amplitude of the Mn2+ EPR spectrum is reduced by the Glu269-->His mutant, while no change is observed in the presence of wild-type permease. The Glu269-->His mutant contains a single binding site for Mn2+ with a KD of about 43 microM, and Mn2+ binding is pH dependent with no binding at pH 5.0, stoichiometric binding at pH 7.5, and a midpoint at about pH 6.3. The results confirm the conclusion that helices VIII and X are closely opposed in the tertiary structure of lac permease and provide a novel approach for studying helix proximity, as well as solvent accessibility, in polytopic membrane proteins.

Characterization of a progesterone-binding, three-domain antibody fragment (VH/K) expressed in Escherichia coli

The heavy chain variable region (VH) and the kappa light chain of the anti-progesterone monoclonal antibody (mAb) DB3, have been expressed as a single-chain three-domain polypeptide, designated VH/K, and secreted into the periplasmic space of Escherichia coli (E. coli). The linker sequence was derived from the VH-CH1 elbow region. The C kappa domain provides a sensitive detection tail for Western blotting and enzyme-linked immunosorbent assay (ELISA). Periplasmic extracts of transformed E. coli contained material that bound progesterone and related steroids with similar specificity and affinity to DB3, and displayed the DB3 idiotype and kappa chain epitopes. Reference to the crystal structure of DB3 suggests that all the characteristics of the combining site interaction with steroids are retained in the bacterially expressed material. Western blotting demonstrated material with a molecular weight equivalent to three domains after reduction, but six domains in the unreduced state, suggesting that the VH/K polypeptide is assembled in the periplasm as a disulphide-bridged dimer. The VH/K construct provides a novel route to expression of antibody combining sites in E. coli for antibody engineering.

The actin gene family in the oriental fruit fly Bactrocera dorsalis. Muscle specific actins

The actin protein is a critical protein in eukaryotic cells. Four actin genes, constituting what appear to be a set of muscle specific actin genes, have been isolated from the genome of the oriental fruit fly Bactrocera dorsalis. DNA sequences have been determined for the coding as well as 3' and 5' flanking regions for each of these genes. These genes have also been characterized in terms of RNA expression patterns, and comparisons have been made to actin genes from other species. Consistent with other actins, there is a high degree of amino acid sequence conservation in the coding regions of these genes. However, even within the coding regions codon usage patterns in the oriental fruit fly are quite different from some other well characterized species. In addition, the DNA sequences in the intermediate 3' and 5' flanking regions exhibit virtually no detectable sequence homology both within and between species. In terms of introns, three of the four actin genes from the oriental fruit fly described here have a single intervening sequence. Two of these genes share the same intron position with the two muscle specific actin genes act79B and act88F from Drosophila melanogaster and with one muscle specific actin gene CcA1 from the Mediterranean fruit fly, Ceratitis capitata. Another gene from the oriental fruit fly shares the same intron position as the muscle specific actin gene act57B from D. melanogaster. Such conservation of intron positioning between species is highly unusual among previously characterized actin genes. Using unique sequences found in the 3' untranslated regions, gene specific probes have also been constructed. These have been used to detect the expression patterns of individual genes in a temporal and spatial manner. Each of the four genes examined here show differential patterns of expression. The patterns indicate that all four genes are most likely to encode muscle specific actins.

Expression and export in Escherichia coli of fusion proteins containing carboxy-terminally located honeybee prepromelittin

The aim of this work was to express a eukaryotic pre-protein in Escherichia coli so that it could be obtained intact, without cleavage, by bacterial leader peptidase. To this end, cDNA coding for honeybee prepromelittin was ligated to the 3' end of genes coding for truncated forms of either Protein A or beta-galactosidase (beta-Gal) under the control of inducible promoters, with an oligonucleotide coding for the Factor Xa cleavage site at the junction between the two proteins. The Protein A fusion was expressed in good yield, and about 80% of it formed inclusion bodies. The prepromelittin section of the Protein A fusion caused some export of the intact fusion protein to the growth medium. The prepromelittin beta-Gal fusion was expressed in low yield and became associated with the E. coli cytoplasmic membrane. Its expression was toxic to E. coli. Thus, the synthesis of a full-length eukaryotic pre-protein in E. coli is best achieved when the fusion protein forms inclusion bodies.

Oligodendroglial signal transduction systems are developmentally regulated

Studies from several laboratories indicate that oligodendroglia exhibit signal transduction systems that can be activated by classical neurotransmitters. Previous studies from this laboratory indicate that oligodendroglia express neuroligand receptors linked to the regulation of Ca(2+)i. Experiments presented in this article were designed to determine if developmental processes that influence the ability of oligodendroglia to respond to neuroligands with an increase in Ca2+i proceed either in vitro or in vivo. Findings support the view that developmental processes markedly affected the sensitivity of these cells to both purinergic and cholinergic receptor agonists, whereas their responsiveness to either histamine or bradykinin appeared relatively stable over time. Approximately 90 and 75% of oligodendroglia responded to ATP or carbachol, respectively, after 4 days in vitro, whereas < 10% of these cells responded to either of these neuroligands after 8 days in vitro. The decrease in the percentage of oligodendroglia responding to ATP, but not carbachol, could be prevented by including dibutyryl cyclic AMP in the culture medium during the final 4 days in vitro. However, once the loss in responsiveness to ATP had occurred, it could not be reversed by exposure to dibutyryl cyclic AMP. Developmental changes in the ATP sensitivity of oligodendroglia occurred in cells expressing galactocerebroside and myelin basic protein. The neuroligand sensitivity of oligodendroglia isolated from either neonatal, 2-, 3-, or 5-week-old spinal cord was examined to determine if developmental changes in oligodendroglial Ca2+ regulation occurred in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Two novel human serine/threonine kinases with homologies to the cell cycle regulating Xenopus MO15, and NIMA kinases: cloning and characterization of their expression pattern

Using polymerase chain reaction (PCR)-based methods, we have isolated cDNA clones of two new members of serine/threonine kinases, STK1 and STK2, from a cDNA library constructed from the BT-20 human breast cancer cell line. STK1 is transcribed as a 1.4 kilobase (kb) mRNA encoding for a protein of 346 amino acids. Based on amino acid sequence analysis, STK1 is 86% identical to the Xenopus p40mo15, a cdc2-related serine/threonine kinase recently found to be the activating kinase for p34cdc2 and p33cdk2. Thus, STK1 is most likely the human homologue of MO15. An alternatively spliced STK1 message expressed variably in cell lines and in primary carcinomas generates a predicted 58 amino acid protein that lacks the kinase domain. STK2 is transcribed into a 4.0 kb mRNA encoding for an 841 residue protein which exhibits 50% identity in the kinase domain with the mouse nek1 gene product, the relative of the fungal G2-M regulator, nimA. STK1 and STK2 display a variable pattern of expression among a series of primary carcinomas as well as cancer cell lines. Both STK1 and STK2 were expressed at the highest levels in the heart but were also detected in all other organs tested. In embryonal tissues, lower levels of expression were noted. Using cell cycle inhibitors, we have shown that both STK1 and STK2 mRNA levels remain relatively invariant through the cell cycle. Chromosomal assignment has localized STK1 on chromosome 2pcen-2p15, a region implicated in hereditary non-polyposis colorectal carcinoma, and STK2 on chromosome 3p21.1, a region frequently showing chromosomal alterations in renal cells carcinomas.

Genetic alterations in the p53 gene in the blast crisis of chronic myelogenous leukemia: analysis by polymerase chain reaction based techniques

Rearrangements of the c-abl protooncogene and the bcr-gene are found in > 90% of patients in chronic phase of chronic myelogenous leukemia (CML). The molecular events leading to blast crisis, however, have not been well characterized. Gross alterations of the p53 gene have been detected in 30% of patients with blast crisis. Since point mutations in the p53 gene appear to be important in the process of transformation in many epithelial tumors, we looked for these mutations in the critical regions of the p53 gene (exons 4, 5, 6, 7, and 8). We used the polymerase chain reaction (PCR), direct sequencing, differential PCR, and single strand conformation polymorphism (SSCP) analysis to detect mutations of the p53 gene in samples from 21 patients with CML blast crisis. Two of 21 patients exhibited an intragenic deletion or rearrangement in p53. In addition, these patients were homozygous for the mutant p53 allele. No mutations were found in the p53 gene of the remaining 19 patients. However, sequencing of the CML blast crisis cell line, K562, revealed an insertion of a C at base position 956 within the fifth exon, causing a frame shift mutation and an early translational stop at codon 148. We conclude that, in contrast to solid tumors, mutations in exons 4-8 of p53 are not frequently seen in primary samples from CML blast crisis. However, deletions and/or rearrangements within the p53 gene do occur and may contribute to the progression from chronic phase to blast crisis in a limited number of patients with CML.

Specificity of factor Xa in the cleavage of fusion proteins

The precursor protein honey bee prepromelittin has been expressed as a fusion protein in Escherichia coli joined to the C-terminus of a truncated form of the bacteriophage gene 10 protein via an engineered recognition sequence for Factor Xa. Factor Xa was found to cleave poorly at the engineered site, giving a low yield of the required prepromelittin. In contrast, cleavage on the C-terminal side of the sequence VLGR at residue 67 in the gene 10 sequence proceeded in high yield. Factor Xa may be inhibited by adjacent hydrophobic sequences on the C-terminal side of a potential cleavage site.