Impact of obesity on adult spinal deformity (ASD) long-segment spinal fusion radiographic and clinical outcomes

STUDY DESIGN

Retrospective chart review of patients receiving long-segment fusion during a five-year period.

OBJECTIVE

To determine whether obese patients receive comparable benefits when receiving long-segment fusion compared to non-obese patients and to identify factors that may predict hardware failure and post-surgical complications among obese patients.

METHODS

Demographic, spinopelvic radiographic, patient-reported outcome measures (PROMs), and complications data was retrospectively collected from 120 patients who underwent long-segment fusion during a five-year period at one tertiary care medical center. Radiographic measurements were pelvic incidence, pelvic tilt (PT), lumbar lordosis, L4-S1 lordosis, thoracic kyphosis, sagittal vertical axis, PI-LL mismatch, and proximal junction cobb angle at upper instrumented vertebrae + 2 (UIV+2). PROMs were Oswestry disability index, numeric rating scale (NRS) Back Pain, NRS Leg Pain, RAND SF-36 pain, and RAND SF-36 physical functioning. Included patients were adults and had at least 2-years of postoperative follow-up. Descriptive and multivariate statistical analysis was performed with α = 0.05.

RESULTS

Patients with a BMI ≥ 30 (n=63) and patients with a BMI < 30 (n=57) demonstrated comparable improvements (P>0.05) for all spinopelvic radiographic measurements and PROMs. Each cohort demonstrated significant improvements from pre-assessment to post-assessment on nearly all spinopelvic radiographic measurements and PROMs (P<0.05), except PT and L4-S1 lordosis where neither group improved (p=0.95 and 0.58 for PT and P=0.23 and 0.11 for L4-S1 lordosis fornon-obese and obese cohorts respectively) and SF-36 physical functioning where the non-obese cohort not statistically improve (P=0.08). Patients with a BMI ≥ 30 demonstrated an increased incidence of cardiovascular complications (P=0.0293), acute kidney injury (P=0.0241), rod fractures (P=0.0293), and reoperations (P=0.0241) when compared to patients with a BMI < 30.

CONCLUSION

This study adds to a growing body of evidence linking demographic factors with risks of hardware failure. Further, this data challenges the assumption that obese patients may not receive sufficient benefit to be long-segment surgical candidates. However, given their elevated risk for post-operative and delayed hardware complications, obese patients should be appropriately counseling before undergoing surgery.

Novel experimental setup for megahertz X-ray diffraction in a diamond anvil cell at the High Energy Density (HED) instrument of the European X-ray Free-Electron Laser (EuXFEL)

The high-precision X-ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X-ray Free-Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump-probe X-ray diffraction experiments in the DAC are described and their implementation demonstrated during the First User Community Assisted Commissioning experiment. X-ray heating and diffraction of Bi under pressure, obtained using 20 fs X-ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in the DAC.

A resistively-heated dynamic diamond anvil cell (RHdDAC) for fast compression x-ray diffraction experiments at high temperatures

A resistively-heated dynamic diamond anvil cell (RHdDAC) setup is presented. The setup enables the dynamic compression of samples at high temperatures by employing a piezoelectric actuator for pressure control and internal heaters for high temperature. The RHdDAC facilitates the precise control of compression rates and was tested in compression experiments at temperatures up to 1400 K and pressures of ∼130 GPa. The mechanical stability of metallic glass gaskets composed of a FeSiB alloy was examined under simultaneous high-pressure/high-temperature conditions. High-temperature dynamic compression experiments on H₂O ice and (Mg, Fe)O ferropericlase were performed in combination with time-resolved x-ray diffraction measurements to characterize crystal structures and compression behaviors. The employment of high brilliance synchrotron radiation combined with two fast GaAs LAMBDA detectors available at the Extreme Conditions Beamline (P02.2) at PETRA III (DESY) facilitates the collection of data with excellent pressure resolution. The pressure-temperature conditions achievable with the RHdDAC combined with its ability to cover a wide range of compression rates and perform tailored compression paths offers perspectives for a variety of future experiments under extreme conditions.

An improved setup for radial diffraction experiments at high pressures and high temperatures in a resistive graphite-heated diamond anvil cell

We present an improved setup for the experimental study of deformation of solids at simultaneous high pressures and temperatures by radial x-ray diffraction. This technique employs a graphite resistive heated Mao-Bell type diamond anvil cell for radial x-ray diffraction in combination with a water-cooled vacuum chamber. The new chamber has been developed by the sample environment group at PETRA III and implemented at the Extreme Conditions Beamline P02.2 at PETRA III, DESY (Hamburg, Germany). We discuss applications of the new setup to study deformation of a variety of materials, including ferropericlase, calcium perovskite, bridgmanite, and tantalum carbide, at high-pressure/temperature.

New dynamic diamond anvil cells for tera-pascal per second fast compression x-ray diffraction experiments

Fast compression experiments performed using dynamic diamond anvil cells (dDACs) employing piezoactuators offer the opportunity to study compression-rate dependent phenomena. In this paper, we describe an experimental setup which allows us to perform time-resolved x-ray diffraction during the fast compression of materials using improved dDACs. The combination of the high flux available using a 25.6 keV x-ray beam focused with a linear array of compound refractive lenses and the two fast GaAs LAMBDA detectors available at the Extreme Conditions Beamline (P02.2) at PETRA III enables the collection of x-ray diffraction patterns at an effective repetition rate of up to 4 kHz. Compression rates of up to 160 TPa/s have been achieved during the compression of gold in a 2.5 ms fast compression using improved dDAC configurations with more powerful piezoactuators. The application of this setup to low-Z compounds at lower compression rates is described, and the high temporal resolution of the setup is demonstrated. The possibility of applying finely tuned pressure profiles opens opportunities for future research, such as using oscillations of the piezoactuator to mimic propagation of seismic waves in the Earth.

Author Correction: Evidence for a Fe3+-rich pyrolitic lower mantle from (Al,Fe)-bearing bridgmanite elasticity data

In Extended Data Table 1 of this Letter, some of the elastic constants were reported incorrectly. This occurred as a result of an error in the script used to generate the numbers. The values of the elastic constants at room pressure cited in the manuscript on page 544 were derived using the same erroneous script, and the correct values and 1σ-uncertainties in the last given digit are C11 = 461.3(17) GPa instead of 462.7(17) GPa; C22 = 509.7(26) GPa instead of 504.9(26) GPa; C33 = 425.7(5) GPa instead of 426.6(5) GPa; C44 = 188.8(6) GPa instead of 188.4(6) GPa; C55 = 166.5(4) GPa instead of 166.6(4) GPa; C66 = 127.2(17) GPa instead of 129.7(17) GPa; C12 = 141.7(14) GPa instead of 140.2(14) GPa; C13 = 130.0(11) GPa instead of 132.2(11) GPa; and C23 = 161.0(12) GPa instead of 159.3(12) GPa. These errors do not affect any of the conclusions and we apologize for any confusion this may have caused. Extended Data Table 1 and the room-pressure values in the text have been corrected online. The Supplementary Information of this Author Correction contains the original, incorrect Extended Data Table 1, for transparency.

Comparison of anthracycline-induced death of human leukemia cells: programmed cell death versus necrosis

We investigated the mode of cell death induced by the anthracyclines, aclarubicin, doxorubicin and daunorubicin in the human leukemia cell lines, HL60 and Jurkat. The cells were incubated with drug concentrations up to 500 nM for periods between 3 and 24 hours, followed by morphological and biochemical analyses. All three substances induced DNA fragmentation, evident as DNA laddering and appearance of cells with hypodiploid DNA content, externalization of phosphatidyl serine, activation of caspases and degradation of the apoptosis-specific endonuclease inhibitor DFF45. However, concentrations and times necessary for these effects to occur were different, aclarubicin being the quickest acting drug with a lag phase of 3 h, followed by daunorubicin with 6 h and doxorubicin with 24 h. More importantly, aclarubicin induced these effects while the cell membrane was intact, whereas doxorubicin and daunorubicin led to immediate loss of membrane integrity. Programmed cell death is characterised by preservation of membrane integrity in order to allow removal of apoptotic bodies, whereas cell rupture is an early event in necrosis. We therefore suggest that, in our experimental settings, doxorubicin- and daunorubicin-induced cell death occurs by necrosis, while aclarubicin induces programmed cell death.

Polyetheretherketone--cytotoxicity and mutagenicity in vitro

The results of the incubation of polyetheretherketone (PEEK) fibre material with seven different genotype variants of salmonella bacterium showed with and without an external metabolic activation system (S9) with no mutagenic or cytotoxic activity of the test material. In the so-called "plate incorporation test" in which the PEEK raw material is finely cut and applied direct to the agar plate without the addition of solvent there was, as expected, no evidence of cytotoxic or mutagenic effects. In the HPRT test there was a significant increase in the number of mutants per dish, both after addition of N-acetylaminofluorene and N-methyl-N'-nitro-N-nitrosoguanidine (with and without an external metabolic activation system = +S9), but not after treatment of the cells with PEEK-DMSO-eluate. This means that the PEEK material under study did not release any substances that cause V79 cells to mutate. The investigation of the toxic reaction on the material under study revealed that the number of surviving colonies per 10(5) surviving cells lay within the range of or below the solvent control even in the presence of high PEEK concentrations (5.0 microg/ml). Therefore, in summary, the study produced no evidence of cell damage caused by PEEK.

Morphological transformation of C3H/M2 mouse fibroblasts by, and genotoxicity of, extracts of human milk

Breast cancer may be initiated by environmental/dietary agents and human milk may act as an ex vivo indicator of in vivo exposure of mammary epithelial cells to genotoxins. Extracts of human milk from UK-resident women (n=7) were tested for their abilities to morphologically transform C3H/M2 mouse fibroblasts. Genotoxicities were assessed in the Salmonella typhimurium reverse-mutation assay in the presence of S9 using strains TA1538 and YG1019, and in metabolically-competent human MCL-5 cells with the micronucleus and with the alkaline single cell gel electrophoresis (comet) assays. Two of the seven extracts were inactive in the transformation assay both in the presence or absence of S9, two appeared to be equally transforming either in the presence or absence of S9, and two other extracts induced increased transformation frequencies in the presence of S9. A seventh extract, tested only in the absence of S9, was inactive. Extracts were either active or inactive in at least three of the four tests applied. Four extracts were active or inactive in all four tests. The results suggest that human milk could be used as a resource for investigations of the as-yet-unidentified transforming agents previously detected in mammary lipid.

Cell transformation in vitro by food-derived heterocyclic amines Trp-P-1, Trp-P-2 and N(2)-OH-PhIP

Heterocyclic aromatic amines (HCA) are formed upon frying of poultry, fish or meat and have been shown to induce tumours in rodent bioassays. We investigated the transforming activity of HCA in an in vitro assay using the M2/C3H mouse fibroblast cell line. An external metabolic activation system (rat liver homogenate) was required in order to observe any HCA-induced cytotoxic effects or cell transforming activity. Trp-P-1 and Trp-P-2 are shown to be among the most potent transforming HCA that have been detected in food. Metabolic activation of HCA has been shown to proceed via N-hydroxylation of the exocyclic amino group. Therefore, we tested 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N(2)-OH-PhIP) the activated metabolite of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine. N(2)-OH-PhIP proved to be one of the most powerful compounds with transforming activity observable at a concentration as low as 30 nM. Since 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is the most abundant HCA formed in fried and grilled food and N-hydroxylation appears to be the predominant pathway of human metabolism, these data support the hypothesis that HCA are involved in the aetiology of human cancer.

Reduction in left ventricular messenger RNA for transforming growth factor beta(1) attenuates left ventricular fibrosis and improves survival without lowering blood pressure in the hypertensive TGR(mRen2)27 Rat

Angiotensin II recruits transforming growth factor beta(1) (TGFbeta(1)) and is related to left ventricular fibrosis. However, it is unclear whether chronic in vivo reduction in left ventricular TGFbeta(1) expression blunts fibrosis and improves outcome in angiotensin II-dependent hypertension. Four-week-old male hypertensive TGR(mRen2)27 (Ren2) rats received either normal food, low-dose losartan (0.5 mg. kg(-1). d(-1)), or tranilast (a nonspecific TGFbeta inhibitor; 400 mg. kg(-1). d(-1)) (n=10 for each group) for 12 weeks and were compared with Sprague-Dawley control rats. The effect of tranilast on survival was evaluated in 34 additional untreated homozygous Ren2 rats. Tranilast or low-dose losartan did not lower blood pressure. However, the increase in left ventricular weight (Ren2 versus SD 3.1+/-0.16 versus 2.1+/- 0.06 mg/g body wt; P<0.05) was significantly (P<0.05) blunted by both tranilast (2.7+/-0.05) and losartan (2.7+/-0.07). Both drugs prevented the increase in left ventricular TGFbeta(1) mRNA and fibronectin mRNA and blunted the increase in hydroxyproline content and the increase in perivascular fibrosis. The perivascular fibrosis score correlated significantly with the level of expression of TGFbeta(1) (r=0.62; P=0.019). In situ hybridization demonstrated increases in TGFbeta(1) mRNA, predominantly in perivascular and nonmyocyte areas. Both drugs did not prevent the decrease in systolic or diastolic dP/dt, but tranilast significantly improved the survival of untreated Ren2 rats (P=0.029). In conclusion, TGFbeta(1) mRNA expression is increased predominantly in nonmyocyte regions in the hypertrophied left ventricle in this angiotensin II-dependent model of hypertension. This increase is probably due to high angiotensin II levels rather than to hypertension. This is the first study to suggest that chronic inhibition of TGFbeta(1) expression attenuates left ventricular hypertrophy and fibrosis, even without lowering blood pressure.

Induction of cyclooxygenase expression and enhancement of malignant cell transformation by 2,3,7,8-tetrachlorodibenzo-p-dioxin

The potential role of arachidonic acid metabolism in the enhancement (promotion) of malignant transformation of C3H/M2 mouse fibroblasts by the tumor promoter 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was investigated using inhibitors of cyclooxygenase and lipoxygenase activities. The promoting effects of TCDD (1.5 pM) and of the reference tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA; 0.4 mM) on carcinogen (N-methyl-N'-nitro-N-nitrosoguanidine or 3-methylcholanthrene)-pre-treated fibroblasts was abolished by cotreatment with indomethacin, hydrocortisone, caffeic acid or nordihydroguaiaretic acid. A differential inhibition was found with N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide, a selective inhibitor of the cyclooxygenase isoenzyme COX-2: the promoting effect of TPA, but not that of TCDD, was abolished. Therefore, the role of the cyclooxygenase isoenzymes COX-1 and COX-2 during chronic exposure to TCDD was studied in more detail. Long-term treatment with TCDD (4-7 weeks) induced the expression of COX-1 and COX-2 mRNA in C3H/M2 fibroblasts (up to 2-fold). The enhanced expression of COX-2 protein in TCDD-treated fibroblasts was confirmed by western blot analysis. Concomitantly, the accumulation of the prostaglandins (PGs) PGE(2) and 6-keto-PGF(1alpha), which were identified as major metabolites of arachidonic acid in C3H/M2 cell cultures, was enhanced ( approximately 2-fold) following long-term treatment with TCDD (0.15 and 1.5 pM). The results suggest that the stimulation of arachidonic acid metabolism caused by a sustained cyclooxygenase induction is a critical event in the promoting action of TCDD in mouse fibroblasts in vitro. However, in contrast to TPA, the TCDD-mediated enhancement of malignant cell transformation may not specifically depend on the induction of COX-2 but, additionally, the induction of COX-1 activity may be necessary.

Cell transformation and genotoxicity induced by bis(2, 3-dichloro-1-propyl) ether

Bis(dichloropropyl) ether isomers have been identified in a petrochemical plant effluent through a toxicity identification evaluation study in the United States. They have also been observed in the microgram per liter range along one of the largest rivers in Europe, the Elbe River. In the present investigation, the genotoxic and transforming activity of a bis(dichloropropyl) ether isomer, bis(2,3-dichloro-1-propyl) ether, was assayed in vitro. The results demonstrate that bis(2,3-dichloro-1-propyl) ether is a potent mutagen in Salmonella typhimurium strains TA 100, TA 1535, and to a lesser extent in strain TA 98, but only when tested in the presence of a metabolic activation system (S9 mix). We have also investigated the induction of micronuclei by bis(2,3-dichloro-1-propyl) ether in the metabolically competent cell line, MCL-5. A linear, dose-dependent increase in micronuclei was observed following exposure to bis(2,3-dichloro-1-propyl) ether. The DNA strand-breaking capacity of this chemical was assessed in the alkaline single-cell gel electrophoresis ("comet") assay with MCL-5 cells. Bis(2,3-dichloro-1-propyl) ether clearly induced DNA strand breaks in the 4.5-45.5 microg/ml dose range. The ether also induced malignant transformation in C3H/M2 mouse fibroblasts after metabolic activation (S9 mix). Thus, it must be suspected that bis(2, 3-dichloro-1-propyl) ether may possess a carcinogenic potential. Since the compound along with its isomers is present in considerable concentrations in surface water, their elimination is a matter of significant public concern.

Heterocyclic aromatic amines induce DNA strand breaks and cell transformation

Heterocyclic aromatic amines (HAAs), formed during the cooking of foods, are known to induce tumours in rodent bioassays and may thus contribute to human cancer risk. We tested six HAAs in a morphological transformation assay and in three in vitro genotoxicity assays. The morphological transforming abilities of HAAs were tested, in the presence of rat-liver S9, in the C3H/M2 fibroblast cell line. Concentration levels of 50 microM 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (8-MeIQx), 100 microM 2-amino-3,4,8-trimethylimidazo-[4,5-f]quinoxaline (4,8-DiMeIQx), 50 microM 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 100 microM 2-amino-9H-pyrido[2,3-b]indole (AalphaC), 100 microM 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeAalphaC) and 15 microM 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) induced maximum transformation potencies of 5.5, 6.6, 6.3, 5.2, 7.3 and 9.2 transformed foci per 10(4) surviving cells, respectively. Bacterial mutagenic activity was determined in the presence of rat-liver S9 using the Salmonella typhimurium reverse-mutation assay employing strain YG1019. Mutagenic potencies of 3800 revertants (revs)/ng with 8-MeIQx, 2900 revs/ng with 4,8-DiMeIQx, 3480 revs/ng with IQ, 1.6 revs/ng with AalphaC, 2.9 revs/ng with MeAalphaC and 5 revs/ng with PhIP were observed. Clastogenic activity in vitro was analysed by the micronucleus assay in metabolically competent MCL-5 cells. Dose-dependent induction of micronuclei was observed for all HAAs tested with 1-5.4% of cells containing micronuclei at 10 ng/ml. Micronucleus induction was in the order 4,8-DiMeIQx > 8-MeIQx > IQ > MeAalphaC > PhIP > AalphaC. DNA strand-breaking activity in MCL-5 cells was measured by the alkaline single cell-gel (comet) assay. The lowest effect doses for significant increases (P < or = 0.0007, Mann-Whitney test) in comet tail length (microm) were 45.5 microg/ml (200 microM) for PhIP, 90.9 microg/ml (410-510 microM) for 4,8-DiMeIQx, IQ, MeAalphaC and AalphaC, and 454.5 microg/ml (2130 microM) for 8-MeIQx. It is not yet clear which of these assays most accurately reflects the genotoxic potential to humans of compounds of this class of environmental carcinogens.

Characterization of the heparan sulfate and chondroitin sulfate assembly sites in CD44

Isoforms of CD44 are differentially modified by the glycosaminoglycans (GAGs) chondroitin sulfate (CS), heparan sulfate (HS), and keratan sulfate. GAG assembly occurs at serines followed by glycines (SG), but not all SG are utilized. Seven SG motifs are distributed in five CD44 exons, and in this paper we identify the HS and CS assembly sites that are utilized in CD44. Not all the CD44 SG sites are modified. The SGSG motif in CD44 exon V3 is the only HS assembly site; this site is also modified with CS. HS and CS attachment at that site was eliminated by mutation of the serines in the V3 motif to alanine (AGAG). Exon E5 is the only other CD44 exon that supports GAG assembly and is modified with CS. Using a number of recombinant CD44 protein fragments we show herein that the eight amino acids located downstream of the SGSG site in V3 are responsible for the specific addition of HS to this site. If the eight amino acids located downstream from the first SG site in CD44 exon E5 are exchanged with those located downstream of the SGSG site in exon V3, the SG site in E5 becomes modified with HS and CS. Likewise if the eight amino acids found downstream from the first SG in E5 are placed downstream from the SGSG in V3, this site is modified with CS but not HS. We also show that these sequences cannot direct the modification of CD44 with HS from a distance. Constructs containing CD44 exon V3 in which the SGSG motif was mutated to AGAG were not modified with HS even though they contained other SG motifs. Thus, a number of sequence and structural requirements that dictate GAG synthesis on CD44 have been identified.

Identification of a binding site on Hsc70 for the immunosuppressant 15-deoxyspergualin

Hsc70, the constitutive form of the heat shock protein 70 family of proteins, is involved in a number of biological activities which include protein folding and molecular chaperoning. Previously, we had shown that the immunosuppressant 15-deoxyspergualin (DSG) specifically interacted with Hsc70, as well as the Hsp90 family of proteins. Although the exact binding site on Hsc70 for protein substrates is unknown, a recent study shows that the extreme C-terminal four amino acids 647EEVD650 play a role in regulating AT-Pase activity, substrate binding, and interaction with HDJ-1. These four amino acids are also found at the C-terminus of Hsp90 and may be involved in similar functions. In this study, we show that DSG binds specifically to this EEVD regulatory domain. Binding of DSG to Hsc70 did not affect its ability to bind peptides. These results suggest that in addition to the ATP binding domain, there are two additional substrate binding domains on Hsc70. DSG should provide a tool for understanding the role of the EEVD motif in biological processes.

Stimulation of the Ca2+-mediated egr-1 and c-fos expression in murine erythroleukaemia cells by cyclosporin A

The Ca2+-induced expression of the primary response genes egr-1 and c-fos was investigated in the murine erythroleukaemia cell line ELM-I-1. Exposure of the cells to the Ca2+-ionophore A23187 led to a rapid transient rise in egr-1 and c-fos mRNA production followed by an increase in Egr-1 and c-Fos protein levels as well as an increase in Egr-1 and activator protein 1 (AP-1) DNA-binding activity. Preincubation of the cells with KN-62, a specific inhibitor of Ca2+/calmodulin-dependent protein kinases, strongly decreased the Ca2+-mediated expression of egr-1 and c-fos. In contrast, treatment with cyclosporin A, which inhibits the Ca2+/calmodulin-dependent protein phosphatase 2B or calcineurin, increased both egr-1 and c-fos mRNA production and the DNA-binding activity of the Egr-1 and AP-1 transcription factors in response to the intracellular Ca+ concentration ([Ca2+]i)-increasing agents A23187 or cyclopiazonic acid. Enhancement of the Ca2+-induced c-fos and egr-1 expression by cyclosporin A was correlated with the capability of this agent to inhibit calcineurin phosphatase activity in ELM-I-1 cells. Studies on the phosphorylation state and DNA-binding activity of the cAMP response element-binding protein (CREB) did not demonstrate an early Ca2+-dependent activation of this transcription factor, suggesting that the regulation of c-fos and egr-1 expression by Ca2+ is not linked to CREB in the haematopoietic ELM-I-1 cells. The results indicate that calcineurin exerts negative regulatory effects on both egr-1 and c-fos expression in murine erythroleukaemia cells, in addition to the calcineurin-mediated down-regulation of c-myb expression observed previously in this cell system. This study therefore emphasizes the important role of calcineurin as a negative modulator of gene expression in certain cell types.

DNA adducts in human breast tissue: association with N-acetyltransferase-2 (NAT2) and NAT1 genotypes

The etiology of human breast cancer is poorly understood, but circumstantial evidence points toward exogenous genotoxins as causative agents; they are believed to exert their carcinogenic action by binding to DNA. Because this binding is often preceded by metabolic activation, it is dependent on the expression and activities of metabolic enzymes of the host. Human mammary tissue samples from 42 women undergoing surgery for breast cancer or reduction mammoplasty were analyzed for DNA adducts by 32P-postlabeling analysis. With the butanol extraction method of DNA adduct enrichment, adduct levels were determined to be 0-414.6 adducts per 10(9) nucleotides, with considerable interindividual variation. To characterize the DNA adducts, we reanalyzed the adduct spots by reversed-phase high-performance liquid chromatography. Of two major adduct spots detected on TLC that accounted for up to 70% of the DNA modification, one eluted as a single peak on high-performance liquid chromatography, whereas the other was resolved into two distinct peaks of radioactivity. These major adducts were highly lipophilic in character. The N-acetyltransferase-1 (NAT1) and NAT2 genes were analyzed for common mutations using random RFLP analysis. An association between NAT2 acetylator status and adduct levels was observed; significantly elevated adduct levels occurred in the mammary DNA from women who were designated slow acetylators for NAT2 [median adduct level = 83.0 adducts per 10(9) nucleotides (range, 9.0-414.6)], as compared with the levels in individuals designated rapid acetylators for NAT2 [median adduct level = 39.7 adducts per 10(9) nucleotides (range, 0-91.0; P = 0.0053)]. On the other hand, NAT1 genotypes were not significantly associated with adduct levels. Although the agents responsible for the DNA modifications in the human breast are not known, this pilot study supports the hypothesis that DNA adduct formation in the human breast may be influenced by the NAT2 genotype.

Morphological transformation of C3H/M2 mouse fibroblasts by extracts of human mammary lipid

Mammary lipid may act as a reservoir for genotoxins. Mammary lipid extracts (MLEs), obtained from eight UK women (21-41 years) undergoing reduction mammoplasty, were examined for their abilities to morphologically transform C3H/M2 mouse fibroblasts. Resultant transformation rates were 0.27, 0.33, 0.07, 0.29, 0.21, 0.00, 0.07, and 0.13 transformed foci/treated dish, respectively. Although the lipid-extraction procedure used was originally designed to extract heterocyclic aromatic amines (HAAs), liquid chromatography/mass spectroscopy (LC/MS) with selective ion monitoring has failed to detect HAAs in any of the lipid extracts so far examined. Genotoxicities were also assessed in S. typhimurium TA98 and in metabolically competent human (MCL-5) cells by the micronucleus and by the alkaline single-cell gel ("comet") assays. The MLEs induced bacterial mutagenicity rates ranging from 0 to 498 revertants/plate/g-lipid equivalent and micronucleus-formation rates from 0 to 20 micronuclei/500 binucleate cells/g-lipid. Median comet tail lengths (induced with MLEs of 8.0 g-lipid equivalent) ranged from 6.0 to 74.0 micrometer. The results demonstrate the presence of as-yet-unidentified transforming agents in mammary lipid.

HLA-E surface expression depends on binding of TAP-dependent peptides derived from certain HLA class I signal sequences

Previous studies showed that HLA-E was expressed in lymphoblastoid cell line (LCL) 721.221 cells, but surface expression was lacking. To determine the signals controlling surface expression, we constructed a series of hybrid genes using complementary portions derived from the HLA-E and HLA-A2 genes. In this manner, a hybrid of HLA-E was identified, designated AEH, which differed from HLA-E by having the HLA-A2 signal sequence substituting for the HLA-E leader peptide. Transfection of LCL 721.221 cells with AEH induced HLA-E surface expression. Analysis of peptides bound to HLA-E revealed that a nonamer peptide derived from the A2 signal sequence was the predominant peptide bound. LCL 721.221 cells transfected with certain class I genes, including HLA-G, were also sufficient to promote peptide binding and HLA-E surface expression without increasing the level of HLA-E heavy chain synthesis. Peptides bound to HLA-E consisted of nine amino acids, with methionine at position 2 and leucine in the carboxyl-terminal position, and were nearly identical to the leader sequence-derived peptide previously shown to be a predominant peptide bound to the murine Qa-1 Ag. Signal peptides derived from certain HLA-B proteins with threonine in position 2 only marginally up-regulated HLA-E surface expression in .221 cells. An examination of HLA-E peptide binding in the TAP negative cell line .134 indicated that peptide binding to HLA-E was dependent on a functional TAP heterodimer regardless of whether peptide was available in cis, as in the AEH construct, or in trans, as in the class I transfectants of .221 cells.

Cloning, overexpression, and purification of cytosine deaminase from Saccharomyces cerevisiae

Cytosine deaminase is an enzyme which has been investigated for cancer chemotherapy as a result of its ability to convert the relatively nontoxic prodrug 5-fluorocytosine into the anticancer drug 5-fluorouracil. To facilitate investigations of the utility of cytosine deaminase for cancer chemotherapy, we have cloned and expressed the enzyme from Saccharomyces cerevisiae. The DNA sequence translates into a protein of 158 amino acids in length, with a predicted molecular weight of 17,563 kilodaltons. Alignment of the cytosine deaminase protein sequence from yeast with a variety of proteins defines a novel sequence motif of cytosine or cytidine binding enzymes. Recombinant expression cassettes encoding cytosine deaminase were transfected into monkey kidney COS cells, which lack endogenous cytosine deaminase, to test for production of a functional protein. Cell extracts from these transfectants contained detectable levels of enzyme activity capable of converting 5-fluorocytosine to 5-fluorouracil. Cytosine deaminase was expressed in yeast from a cDNA cassette under the control of an inducible promoter, increasing expression 250- to 300-fold relative to wild-type strains. A purification protocol has been developed which permits recovery of 60% of cytosine deaminase in active form from induced cell lysates after two purification steps. This protocol will be useful for isolating large quantities of pure enzyme which are required for the preclinical evaluation of monoclonal antibody-cytosine deaminase conjugates in combination with 5-fluorocytosine.

Signalling mechanisms in erythropoiesis: the enigmatic role of calcium

The glycoprotein hormone, erythropoietin is the principal regulator of the production of circulating erythrocytes by controlling proliferation, differentiation and survival of its target erythroid progenitor cells. The receptor for erythropoietin is a type I cytokine receptor lacking intrinsic tyrosine kinase activity. It mediates tyrosine phosphorylation through its association with nonreceptor tyrosine kinases such as JAK2 and initiates a cascade of signalling events in response to erythropoietin. Significant progress has been made in identifying signalling pathways triggered by erythropoietin. However, the exact signalling mechanisms mediating the known physiological effects of erythropoietin in erythroid progenitor cells are poorly understood. There are many open questions including the role of Ca2+ in erythropoietin induced signal transduction. Although the results concerning the effect of erythropoietin on [Ca2+]i in various erythroid cells are conflicting, [Ca2+]i-increasing agents mimic the effect of erythropoietin on c-myb expression and activate the program of haemoglobin synthesis in murine erythroleukemia cells. An attempt is made in this review to survey recent data on the erythropoietin-induced signal transduction with respect to the different physiological effects of this hormone.

Pancreatic DNA adducts formed in vitro and in vivo by the food mutagens 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeA alphaC)

Genotoxic heterocyclic amines have been detected in grilled or fried meat and tobacco smoke. Among these, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeA alphaC) have been shown to induce tumours in rodents in several organs. Here we report on the DNA adduct formation by PhIP and MeA alphaC in vitro and in vivo, both in rat hepatic and rat pancreatic tissues or cells. Using 32P-postlabelling analysis both compounds were shown to induce a dose-dependent DNA modification in primary rat hepatocytes that was correlated with cytotoxicity in these cells. In explanted rat pancreas maintained in dynamic short-term organ culture MeA alphaC was shown to induce covalent DNA adducts. No DNA adducts were observed with PhIP in this assay. DNA adducts were observed in the liver and the pancreas of F344 rats treated with PhIP, with a 36-times higher level of adducts in the pancreas, confirming data reported earlier. DNA adduct levels induced by feeding 32, 160 or 800 ppm MeA alphaC in the diet were dose-dependent and higher in the liver compared with other organs including pancreas. While for PhIP the N2-(desoxyguanin-8-yl)-derivative was accounting for more than 90% of DNA adducts detected, in the case of MeA alphaC the N2-(desoxyguanin-8-yl) adduct was predominant in vitro and determined in vivo as one of up to 5 DNA adducts. MeA alphaC had been reported to induce preneoplastic foci and tumours in the liver and tumours and atrophy in the pancreas. In the case of MeA alphaC, the DNA adduct formation and cytotoxicity observed by us in vitro and in vivo correlate with the organ specificity of the reported pathological lesions. In the case of PhIP our in vitro data in pancreas and liver and the low adduct levels in liver in vivo also reflect the reported lack of pathological effects in these organs. In contrast, in pancreas, in vivo extraordinarily high adduct levels induced by PhIP were observed confirming studies published earlier, in spite of the fact that this compound does not cause pancreatic lesions. This enigmatic observation is discussed and the relevant literature is reviewed.

Characterization of the major DNA adduct formed by the food mutagen 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeAalphaC) in primary rat hepatocytes

Cooking of proteinous food results in the formation of heterocyclic amines. Among these, 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeAalphaC) has been identified as a mutagenic pyrolysis product of soya protein and has been detected in grilled or pan fried meat. It was subsequently proven to be carcinogenic in mice and, recently, in rats and to form covalent DNA adducts in vitro and in vivo. The corresponding nitro compound, 2-nitro-3-methyl-9H-pyrido[2,3-b]indole (MeNalphaC), was prepared and shown to be a direct acting mutagen in the Ames Salmonella reversion assay. When MeNalphaC was chemically reduced in the presence of DNA a major DNA adduct was detected using the 32P-postlabelling assay. This major adduct was characterized by UV spectroscopy and mass spectrometry as N-(deoxyguanosin-8-yl)-2-amino-3-methyl-9H-pyrido[2,3-b]indole. This structure was corroborated by identification of the modified base as a guanine moiety modified at the C8 position as judged by chromatographic and spectral comparison with a standard synthesized from acetylated guanine-N3-oxide and MeAalphaC was characterized by UV/Vis and 1H NMR spectroscopy and mass spectrometry. Treatment of primary rat hepatocytes with MeAalphaC (100 microM, 24 h) resulted in adduct levels of 9.8 fmol/microg DNA as determined by 32P-postlabelling analysis. Using HPLC analysis, two major 32P-labelled adducts were observed accounting for 80 and 13% of total binding respectively. The major adduct was chromatographically indistinguishable from the synthetic deoxyguanosine-C8 adduct using both ion-exchange thin layer or reversed-phase HPLC. Although MeAalphaC is formed only in low p.p.b. levels in cooked food, the contribution to the human carcinogenic risk that might be imposed by heterocyclic amines is not to be neglected.

Characterization of a CD43/leukosialin-mediated pathway for inducing apoptosis in human T-lymphoblastoid cells

The monoclonal antibody (mAb) J393 induces apoptosis in Jurkat T-cells. NH2-terminal amino acid sequence analysis identified the 140-kDa surface antigen for mAb J393 as CD43/leukosialin, the major sialoglycoprotein of leukocytes. While Jurkat cells co-expressed two discrete cell-surface isoforms of CD43, recognized by mAb J393 and mAb G10-2, respectively, only J393/CD43 signaled apoptosis. J393/CD43 was found to be hyposialylated, bearing predominantly O-linked monosaccharide glycans, whereas G10-2/CD43 bore complex sialylated tetra- and hexasaccharide chains. Treatment with soluble, bivalent mAb J393 killed 25-50% of the cell population, while concomitant engagement of either the CD3.TcR complex or the integrins CD18 and CD29 significantly potentiated this effect. Treatment of Jurkat cells with mAb J393 induced tyrosine phosphorylation of specific protein substrates that underwent hyperphosphorylation upon antigen receptor costimulation. Tyrosine kinase inhibition by herbimycin A diminished J393/CD43-mediated apoptosis, whereas inhibition of phosphotyrosine phosphatase activity by bis(maltolato)oxovanadium-IV enhanced cell death. Signal transduction through tyrosine kinase activation may lead to altered gene expression, as J393/CD43 ligation prompted decreases in the nuclear localization of the transcriptional regulatory protein NF-kappaB and proteins binding the interferon-inducible regulatory element. Since peripheral blood T-lymphocytes express cryptic epitopes for mAb J393, these findings demonstrate the existence of a tightly regulated CD43-mediated pathway for inducing apoptosis in human T-cell lineages.

The amino-terminal immunoglobulin-like domain of activated leukocyte cell adhesion molecule binds specifically to the membrane-proximal scavenger receptor cysteine-rich domain of CD6 with a 1:1 stoichiometry

Activated leukocyte cell adhesion molecule (ALCAM) was recently identified as a ligand for CD6, a signaling receptor expressed on T cells, a subset of B cells, and some cells in the brain. Receptor-ligand binding assays, antibody blocking experiments, and examination of the tissue distribution of these two cell surface proteins suggest that CD6-ALCAM interactions play an important role in mediating the binding of thymocytes to thymic epithelial cells and of T cells to activated leukocytes. Presently, the details of CD6-ALCAM interactions and of signaling through CD6 are unknown. A series of truncated human ALCAM and CD6 immunoglobulin fusion proteins were produced and tested in different binding assays to analyze ALCAM-CD6 interactions in more detail. In this study, we report that the amino-terminal Ig-like domain of human ALCAM specifically binds to the third membrane-proximal scavenger receptor cysteine-rich (SRCR) domain of human CD6. Using thrombin-cleaved Ig fusion proteins containing single or multiple ALCAM or CD6 domains, we were able to determine that the stoichiometry of the interaction between the amino-terminal ALCAM domains and the membrane-proximal CD6 SRCR domain is 1:1. These results provide the first example of an Ig-like domain mediating an interaction with an SRCR domain.

Use of combinatorial peptide libraries to construct functional mimics of tumor epitopes recognized by MHC class I-restricted cytolytic T lymphocytes

Identification of cytolytic T lymphocyte (CTL) epitopes presented by major histocompatibility complex (MHC) class I molecules on tumor cells is critical for the design of active immunotherapy. We describe the use of combinatorial peptide libraries with defined amino acids in two MHC anchor positions to search for epitopes that are recognized by H-2Db- and Kb-restricted CTL specific for the mouse lymphoma EL4. An iterative strategy was used for screening libraries in which 16 amino acids were divided into 3 groups and 3 subgroups: alpha (AL, VT, FY); beta (GS, P, DE); gamma (KR, H, NQ). The proportions of each group and subgroup at individual peptide positions were changed in the library synthesis, and the effect of these changes on CTL activity was measured in a sensitive RMA-S cell assay. A single H-2Db epitope mimic was deduced from the original library that contained > 2 x 10(8) potential peptides and was at least 9 logs more potent than the original library. Immunization of syngeneic mice with this peptide elicited CTL that lysed EL4 cells as well as RMA-S cells pulsed with peptides isolated from Db molecules of EL4 cells, indicating functional similarity between the mimicking peptide and the naturally processed CTL epitope. Furthermore, adoptive transfer of such a CTL line had a therapeutic effect in mice with EL4 established as an ascites tumor. Two H-2Kb-restricted epitope mimics of the same tumor were also identified. Our method represents a novel approach for the construction of MHC class I-restricted targets that can serve as immunogens for active immunotherapy of cancer.

Ca2+/calmodulin-dependent and -independent down-regulation of c-myb mRNA levels in erythropoietin-responsive murine erythroleukemia cells. The role of calcineurin

Down-regulation of c-myb mRNA levels by [Ca2+]i-increasing agents (A23187, thapsigargin, cyclopiazonic acid) and erythropoietin was comparatively studied in the erythropoietin-responsive murine erythroleukemia cell line, ELM-I-1. The Ca2+-induced suppression of c-myb mRNA could be inhibited by the calmodulin antagonists trifluoperazine and calmidazolium, as well as by cyclosporin A, an inhibitor of the Ca2+/calmodulin-dependent protein phosphatase 2B (calcineurin). KN-62, an inhibitor of Ca2+/calmodulin-dependent protein kinases, did not antagonize the Ca2+-mediated decrease in c-myb mRNA. In cyclosporin A-treated ELM-I-1 cells, a close correlation could be demonstrated between the antagonization of the Ca2+ effect on c-myb mRNA levels and inhibition of the calcineurin phophatase activity. On the other hand, FK506, which did not inhibit calcineurin activity in ELM-I-1 cells, failed to prevent the Ca2+-mediated decrease in c-myb mRNA. The erythropoietin-induced down-regulation of c-myb mRNA levels could be demonstrated also in the presence of EGTA and was resistant to calmodulin antagonists and cyclosporin A. In addition, no increase in [Ca2+]i was observed in ELM-I-1 cells in response to erythropoietin. Cyclosporin A inhibited the Ca2+-induced hemoglobin production, while the erythropoietin-mediated increase in hemoglobin synthesis was not affected. The results indicate that the Ca2+-induced decrease in c-myb mRNA and increase in hemoglobin synthesis is mediated by calcineurin, while these effects of erythropoietin occur independently of Ca2+ in ELM-I-1 cells. Calcineurin may be involved in the regulation of c-myb expression in erythroid precursor cells and Ca2+ signals via calcineurin may positively modulate the differentiation inducing action of erythropoietin.

Antioxidants inhibit the enhancement of malignant cell transformation induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin

The mechanisms of the tumor promoting activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were studied using as in vitro model the enhancement ('promotion') of malignant transformation of C3H/M2 mouse fibroblasts induced by N-methyl-N'-nitro-N-nitrosoguanidine or 3-methylcholanthrene. In this assay, the promoting effect of TCDD was maximal at a very low concentration of 1.5 pM and was comparable to the effect of the reference tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA, 0.25 microg/ml). The role of reactive oxygen species in the promoting action was investigated: mannitol, a scavenger of hydroxyl radicals, or antioxidants, i.e. ascorbic acid plus alpha-tocopherol, abolished the in vitro promoting effects of TPA and TCDD. Furthermore, the involvement of protein kinase C (PKC) activation was studied: the protein kinase inhibitor H-7 markedly reduced the in vitro promoting activity of TPA but did not affect the promotion by TCDD. In accord with these results, TPA, but not TCDD, enhanced the PKC activity in C3H/M2 fibroblasts. Since the TPA-mediated activation of PKC was not affected by ascorbate plus alpha-tocopherol, it is concluded that the antioxidants interfere with tumor promotion at a step beyond PKC activation. Thus, the results suggest that the enhancement of malignant cell transformation by TPA and TCDD is dependent on a common mechanism, possibly induced by oxygen radicals, and, in addition, on further mechanisms that may involve agent-specific signalling pathways (e.g. PKC activation by TPA).

Pharmacological and toxicological aspects of new imidazoacridinone antitumor agents

Imidazoacridinones represent a new group of antitumor compounds developed by J. Konopa and coworkers in Gdansk, Poland (W.M. Cholody, J. Med. Chem., 33: 49-52, 1990). The compounds exert activity against a broad spectrum of human tumors in the National Cancer Institute in vitro screening scheme. In this work, the in vitro cytotoxicity, cellular pharmacology, and genotoxic/transforming potential of five selected imidazoacridinones were studied. The compounds were highly cytotoxic (0.01-0.40 microM) to dividing cells, such as Friend erythroleukemia cells (line F4-6), V79 Chinese hamster cells, and exponentially growing C3H/M2 mouse fibroblasts. In contrast, nondividing primary rat hepatocytes and C3H/M2 cells in confluency were less sensitive to the toxicity of the imidazoacridinones. Multidrug-resistant-overexpressing F4-6 cells, 200-fold resistant to doxorubicin, showed only partial resistance (4-10 fold) to the imidazoacridinones. The cellular transport of the fluorescent imidazoacridinones occurred rapidly, and most of the drug fluorescence was localized in the nucleus. Cellular accumulation and retention of two selected imidazoacridinones (C-1310 and C-1311) in sensitive as well as in resistant F4-6 cells were determined with laser-excited flow cytometry. After an incubation with C-1311 and C-1310 for 60 min at 37 degrees C, the cellular accumulation of the less cytotoxic compound C-1310 was greater than that of C-1311, and for both compounds, the fluorescence in the resistant F4-6 cells was one-half of that in the sensitive F4-6 cells. Lowered temperature (4 degrees C) reduced the cellular accumulation for both compounds in the sensitive and in the resistant F4-6 cells and was comparable to the uptake in resistant F4-6 cells. The treatment of the resistant F4-6 cells with the multidrug-resistant modulator verapamil led to an enhanced accumulation of C-1310 and C-1311 by the cells. All five compounds produced a dose-dependent inhibition of [3H]uridine and [14C]thymidine incorporation and, except for C-1336, preferentially inhibited DNA synthesis. The affinity of the imidazoacridinones to DNA is also indicated by an increase of the DNA melting point by 9-11 degrees C. The mutagenic potential of the imidazoacridinones was investigated in the hypoxanthine guanine phosphoribosyl transferase test; the compounds C-1310 and C-1311 were additionally tested in the Salmonella typhimurium-microsome assay. Limited mutagenicity was detected in the hypoxanthine guanine phosphoribosyl transferase test, and in Salmonella typhimurium, mutagenicity was observed only in the strain TA1537. Furthermore, no induction of DNA repair synthesis was observed after treatment of primary hepatocytes with the five imidazoacridinones. The compounds did not transform C3H/M2 fibroblasts. One derivative, C-1336, led to a significant induction of cell differentiation in Friend erythroleukemia cells. The results of this study show that the imidazoacridinones display a strong cytotoxic effect in rapidly dividing cells and only a partial resistance toward multidrug resistant cells; in addition, they showed a limited mutagenic potential in V79 fibroblasts and Salmonella typhimurium and no transforming potential in C3H/M2 cells. The imidazoacridinones are, therefore, an interesting group of new antitumor agents, and further in vivo studies are warranted to explore the usefulness of these compounds for the treatment of human cancer.

The role of rat serum carboxylesterase in the activation of paclitaxel and camptothecin prodrugs

Paclitaxel-2-ethylcarbonate (PC) is a prototype for a family of paclitaxel prodrugs that have significant levels of antitumor activities in rodent models for human cancer. In this study, an enzyme responsible for the conversion of PC to paclitaxel was purified from rat serum. N-terminal amino acid sequence analysis indicated that the isolated enzyme was rat serum carboxylesterase. This enzyme was shown to significantly enhance the cytotoxic activities of both PC and 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11), a water-soluble analogue of camptothecin, on lung carcinoma and melanoma cell lines. Rat serum carboxylesterase may have applications for the site-specific delivery of anticancer drugs to tumor masses.

B7-CD28 costimulation unveils the hierarchy of tumor epitopes recognized by major histocompatibility complex class I-restricted CD8+ cytolytic T lymphocytes

Immunization of mice with tumors genetically engineered to express the B7 costimulatory molecules amplifies the antitumor immune response mediated by CD8+ cytolytic T lymphocytes (CTL). In this report, we examined the effect of B7-CD28 costimulation on the hierarchy of tumor epitopes. Using a combination of affinity chromatography/reversed-phase high performance liquid chromatography and CTL cloning, we show that major histocompatibility complex (MHC) class I molecules from EL4 lymphoma cells can present at least six distinct CTL epitopes presented by MHC class I molecules. Nevertheless, mice immunized with wild-type B7-negative EL4 cells develop CTL only to one immunodominant epitope. In contrast, immunization with B7-transduced EL4 cells led to not only the amplification of the CTL response to this immunodominant epitope, but also to the recognition of five otherwise silent subdominant epitopes. The adoptive transfer of a CTL clone against such a subdominant epitope cured mice bearing EL4 lymphoma growing as an ascites tumor. The fact that CTL response can be spread to normally silent epitopes as a result of B7-CD28 costimulation suggests a novel approach to manipulate the hierarchy of CTL epitopes and offers an opportunity to explore novel targets for T cell-mediated cancer therapy.

Rapid and reliable cloning of antibody variable regions and generation of recombinant single chain antibody fragments

Single chain antibody variable region fragments (sFv), by virtue of their size and method of construction are potentially useful as therapeutic reagents and as tools for exploring cell surface receptor function. sFv offer several advantages over the intact immunoglobulin molecule. For instance, they are expressed from a single transcript and can be molecularly linked to other proteins to generate bispecific sFv molecules or single-chain immunotoxins. The relatively small size of sFv is an advantage in allowing for easier penetrance into tissue spaces, and their clearance rate is exceedingly rapid. sFv are useful for gene therapy since they can be directed to a specific cellular localization and can be fused to retroviral env genes to control viral host range. To prepare sFv to murine and human leukocyte CD antigens, we devised a method for rapid cloning and expression that can yield functional protein within 2-3 weeks of RNA isolation from hybridoma cells. The variable regions were cloned by poly-G tailing the first strand cDNA followed by anchor PCR with a forward poly-C anchor primer and a reverse primer specific for constant region sequence. Both primers contain flanking restriction sites for insertion into PUC19. Sets of PCR primers for isolation of murine, hamster and rat VL and VH genes were generated. Following determination of consensus sequences for a specific VL and VH pair, the VL and VH genes were linked by DNA encoding an intervening peptide linker [usually (Gly4Ser)3] and the VL-link-VH gene cassettes were transferred into the pCDM8 mammalian expression vector. The constructs were transfected into COS cells and sFvs were recovered from spent culture supernatant. We have used this method to generate functional sFv to human CD2, CD3, CD4, CD8, CD28, CD40, CD45 and to murine CD3 and gp39, from hybridomas producing murine, rat, or hamster antibodies. Initially, the sFvs were expressed as fusion proteins with the hinge-CH2-CH3 domains of human IgG1 to facilitate rapid characterization and purification using goat anti-human IgG reagents or protein A. We also found that active sFv could be expressed with a small peptide > or = tag > or = or in a tail-less form. Expression of CD3 (G19-4) sFv tail-less or Ig tailed forms demonstrated increased cellular signalling activity and suggested that sFv have potential for activating receptors.

The membrane-bound and soluble forms of HLA-G bind identical sets of endogenous peptides but differ with respect to TAP association

The class Ib antigen HLA-G is expressed as a membrane-bound protein like classical class Ia molecules (M.HLA-G) but, unlike typical class I, is also expressed as a soluble protein (S.HLA-G) with a unique C terminus. Our results show that, similar to classical class I proteins, the membrane-bound form of HLA-G associated with TAP, as evidenced by the ability to immunoprecipitate HLA-G class I heavy chain with TAP antisera. In contrast, the soluble G protein did not appear to associate with TAP in the same manner, since similar immunoprecipitation experiments failed to detect soluble G complex. A detailed analysis of peptides bound to the soluble and membrane HLA-G proteins expressed in the B lymphoblastoid cell line 721.221 showed that, like class Ia complexes, both HLA-G proteins consist of heavy and light chains complexed with nonameric peptides in a 1:1:1 ratio. The two proteins bind essentially the same set of peptides, which are derived from a variety of intracellular proteins and define a peptide motif for HLA-G. The peptides contain Leu at the C terminus and Pro or small hydrophobic amino acids in position 3 followed by Pro or Gly in position 4. The complexity of the bound peptides is lower than that found for some class Ia complexes, but is more similar to class Ia than to the limited repertoire of some murine class Ib molecules.

Cloning, mapping, and characterization of activated leukocyte-cell adhesion molecule (ALCAM), a CD6 ligand

Antibody-blocking studies have demonstrated the role of CD6 in thymocyte-thymic epithelial (TE) cell adhesion. Here we report that CD6 expressed by COS cells mediates adhesion to TE cells and that this interaction is specifically blocked with an anti-CD6 monoclonal antibody (mAb) or with a mAb (J4-81) that recognized a TE cell antigen. We isolated and expressed a cDNA clone encoding this antigen and show that COS cells transfected with this cDNA bind a CD6 immunoglobulin fusion protein (CD6-Rg). This antigen, which we named ALCAM (activated leukocyte-cell adhesion molecule) because of its expression on activated leukocytes, appears to be the human homologue of the chicken neural adhesion molecule BEN/SC-1/DM-GRASP. The gene was mapped to human chromosome 3q13.1-q13.2 by fluorescence in situ hybridization of cDNA probes to metaphase chromosomes. We prepared an ALCAM-Rg fusion protein and showed that it binds to COS cell transfectants expressing CD6, demonstrating that ALCAM is a CD6 ligand. The observations that ALCAM is also expressed by activated leukocytes and that both ALCAM and CD6 are expressed in the brain suggest that ALCAM-CD6 interactions may play a role in the binding of T and B cells to activated leukocytes, as well as in interactions between cells of the nervous system.

Cytotoxicity and mutagenicity of Kevlar: an in vitro evaluation

Toxicity and mutagenicity of Kevlar 49 (PPPT; poly-para-phenylene-terephthalamide) was tested in six strains of Salmonella typhimurium (Ames test; TA97, TA98, TA100, TA102, TA1535, TA1537) with and without an external metabolic activation system (S9), as well as in a mammalian cell mutagenesis assay using V79 Chinese hamster cells. For the Ames test, liquid preincubation, which is considered particularly sensitive, was used. The cells were incubated for 24 h at a temperature of 37 degrees C either directly with Kevlar49 or with ethanol- or chloroform-extracted Kevlar49. The experiments were performed at least twice. The Ames test with six different Salmonella typhimurium strains featuring either base pair substitution or frameshift mutations revealed no cytotoxic or mutagenic activity of Kevlar49. In the mammalian cell mutagenesis assay, using 8-azaguanine (AG) as a selective agent, Kevlar49 was also devoid of cytotoxic or mutagenic activity. Both tests have to be regarded as an initial exploratory screening due to the chosen testing conditions and should be supplemented by tests at different temperatures.

DMSO-like rapid decrease in c-myc and c-myb mRNA levels and induction of differentiation in HL-60 cells by the anthracycline antitumor antibiotic aclarubicin

The anthracycline antitumor antibiotic aclarubicin is known to induce granulocytic differentiation in the human myeloid leukemia cell line HL-60. We investigated whether this effect is accompanied by changes in the expression of the protooncogenes c-myc and c-myb. Treatment of HL-60 cells with aclarubicin, 50 nM, caused a rapid decrease in c-myc and c-myb mRNA levels within 1 h and 2 h, respectively. In parallel, we demonstrated a strong induction of superoxide-anion production on day 8 of treatment. The kinetics of the effect of aclarubicin on c-myc and c-myb expression were comparable to those associated with the dimethylsulfoxide-induced granulocytic differentiation in this cell line, or to those observed following a chase with actinomycin D, 4 microM. Since aclarubicin partially inhibited total- and poly(A)(+)-RNA synthesis, this macromolecular synthesis inhibition may be causally related to the decrease in c-myc and c-myb mRNA levels. In contrast, the conventional anthracycline doxorubicin, which did not initiate differentiation, failed to affect c-myc or c-myb mRNA levels even in high cytotoxic concentrations, indicating that the suppression of c-myc and c-myb mRNA levels may be an early differentiation-related effect of aclarubicin. On the other hand, actinomycin D, 12.5 nM, and novobiocin, 300 microM, two other known inducers of granulocytic differentiation in HL-60 cells, did not induce an early decrease in c-myb or c-myc expression. Therefore, the immediate suppression of c-myc and c-myb mRNA levels, apparently, is not an obligatory step in chemically induced myeloid differentiation in HL-60 cells, but the common phenomenon in DMSO- and aclarubicin-induced differentiation.

Characterization of ribosome-inactivating proteins isolated from Bryonia dioica and their utility as carcinoma-reactive immunoconjugates

Two ribosome-inactivating proteins (RIPs) were isolated and characterized from the roots of Bryonia dioica. One of these was a novel 27-kDa protein termed bryodin 2 (BD2), while the second was a previously reported RIP, referred to here as bryodin 1 (BD1). The amino-terminal sequence obtained for BD2 was similar, but distinct from BD1, ricin A chain, trichosanthin, and momorcharin. BD2-specific monoclonal antibodies were generated and found not to react with BD1 or ricin A chain. Purified BD1 and BD2 RIP inhibited protein synthesis in a cell-free in vitro translation assay at EC50 values of 7 and 9 pM, respectively. Intravenous administration of BD1 was less toxic to mice than BD2, with LD50 values of > 40 for BD1 and 10-12 mg/kg for BD2. Primary human endothelial cells were 5-8-fold less sensitive to BD1 and BD2 than compared to ricin A chain. BD1 and BD2 were constructed as immunoconjugates with the chimeric form of BR96 (chiBR96), a carcinoma-reactive, internalizing antibody. ChiBR96-BD1 and chiBR96-BD2 were found to bind to and kill BR96 antigen-positive carcinoma cells while not killing antigen-negative carcinoma cells. Bryodins represent RIPs that may be useful in constructing immunotoxin conjugates with reduced toxicity and vascular sensitivity, as compared to ricin A chain immunotoxins.

beta ig-h3: a transforming growth factor-beta-responsive gene encoding a secreted protein that inhibits cell attachment in vitro and suppresses the growth of CHO cells in nude mice

beta ig-h3 is a novel gene first discovered by differential screening of a cDNA library made from A549 human lung adenocarcinoma cells treated with transforming growth factor-beta 1 (TGF-beta 1). It encodes a 683-amino-acid protein containing a secretory signal sequence and four homologous internal domains. Here we show that treatment of several types of cells, including human melanoma cells, human mammary epithelial cells, human keratinocytes, and human fibroblasts, with TGF-beta resulted in a significant increase in beta ig-h3 RNA. A portion of the beta ig-h3 coding sequence was expressed in bacteria, and antisera against the bacterially produced protein was raised in rabbits. This antisera was used to demonstrate that several cell lines secreted a 68-kD beta IG-H3 protein after treatment with TGF-beta. Transfection of beta IG-H3 expression plasmids into Chinese hamster ovary (CHO) cells led to a marked decrease in the ability of these cells to form tumors in nude mice. The beta IG-H3 protein was purified from media conditioned by recombinant CHO cells, characterized by immunoblotting and protein sequencing and shown to function in an anti-adhesion assay in that it inhibited the attachment of A549, HeLa, and WI-38 cells to plastic in serum-free media. Sequencing of cDNA clones encoding murine beta ig-H3 indicated 90.6% conservation at the amino acid level between the murine and human proteins. Finally, the beta ig-h3 gene was localized to human chromosome 5q31, a region frequently deleted in preleukemic myelodysplasia and leukemia. The corresponding mouse beta ig-h3 gene was mapped to mouse chromosome 13 region B to C1, which confirms a region of conservation on human chromosome 5 and mouse chromosome 13. We suggest that this protein be named p68 beta ig-h3.

Differential processing and secretion of the melanoma-associated ME20 antigen

A murine monoclonal antibody, ME20, with high selectivity for melanomas, has been utilized to isolate a unique membrane-bound (designated ME20-M) and secreted (designated ME20-S) antigen from H3606 human melanoma cells. ME20-M was purified from the cell lysate and ME20-S from the conditioned medium of H3606 cells by immunoaffinity chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The apparent molecular weights were 105,000 and 76,000, respectively. Analyses of ME20-M and ME20-S by amino acid sequencing identified the processing sites. Signal peptide cleavage occurs at Thr-24 of pro-ME20 antigen, yielding ME20-M (25 to 661). In addition, proteolytic processing of the precursor at Val-467 yields ME20-S (25 to 467). We report the characterization of Asn-linked glycosylation sites in ME20-M and ME20-S to determine the involvement of oligosaccharides in the proteolytic processing of pro-ME20 antigen. Tryptic peptide maps of ME20-M and ME20-S were prepared and the glycosylation sites identified by sequence analyses. Oligosaccharides were enzymatically released and characterized by high-performance anion-exchange chromatography. We found high-mannose-type structures at Asn-57, Asn-82, and Asn-87 of ME20-M, whereas ME20-S contained 73% complex-type and 27% high-mannose-type oligosaccharides at the same sites. To assess the role of oligosaccharides in the processing of the ME20 antigen, we tested the effect of the oligosaccharide processing modifier deoxymannojirimycin, a compound that inhibits synthesis of hybrid- and complex-type oligosaccharides. Deoxymannojirimycin had no effect on the synthesis and relative rate of synthesis of ME20-M, but markedly reduced the synthesis of ME20-S without affecting the rate of secretion. The reported results suggest that carbohydrate maturation of the ME20 antigen may be important for processing and secretion.

32P-post-labelling analysis of DNA adducts formed by food-derived heterocyclic amines: evidence for incomplete hydrolysis and a procedure for adduct pattern simplification

Food-derived aminoimidazoazarenes have been shown to be mutagenic and carcinogenic and to form covalent DNA adducts. 32P-Post-labelling analysis of DNA modified with these heterocyclic amines (HA), including 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,4-dimethylimidazo [4,5-f]quinoline (MeIQ), 2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline (7,8-DiMeIQx) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) has resulted in considerable interlaboratory variation in the characteristic patterns of DNA adduct spots, with up to six being detected for each compound. Similar complex patterns were observed when azido-derivatives of HA were photoreacted with calf thymus DNA. When deoxyguanosine 3'-monophosphate was modified with the azido derivatives and analysed using the 32P-post-labelling procedure, one major spot was observed for IQ, 4,8-DiMeIQx, 7,8-DiMeIQx or PhIP and two major spots for MeIQ or MeIQx. In each case, these adducts were chromatographically indistinguishable from the major adducts formed with DNA. No major adduct spots were observed when 3'-phosphate derivatives of deoxyadenosine, deoxycytidine or thymidine were reacted with the azido-derivatives of HA. In an attempt to identify the additional spots, azido derivatives of PhIP or IQ were reacted with the synthetic homopolymer poly(dG).poly(dC), the alternating copolymer poly(dC-dG) or a synthetic oligonucleotide (TTT-GTTTTTTCTTTCCCT): in each case a reduced number of adduct spots were detected. The introduction of an additional nuclease P1 hydrolysis step following the labelling reaction further reduced the number of adduct spots to only one or two major spots. Reversed-phase HPLC analysis showed that the number of peaks of radioactivity was also reduced to one or two, presumably corresponding to the [32P]-5'-monophosphate deoxyguanosine adducts. We suggest that many of the additional spots commonly observed in conventional 32P-post-labelling analysis of HA-modified DNA are adducted oligonucleotides that are partly resistant to hydrolysis by micrococcal nuclease and spleen phosphodiesterase but are susceptible to hydrolysis by nuclease P1.

Early transient suppression of c-myb mRNA levels and induction of differentiation in Friend erythroleukemia cells by the [Ca2+]i-increasing agents cyclopiazonic acid and thapsigargin

Cyclopiazonic acid and thapsigargin, inhibitors of the endoplasmic reticulum Ca2+ pump were shown to elevate [Ca2+]i in Friend erythroleukemia cells, line F4-6, at concentrations of 1-5 microM and 0.5-2 nM, respectively. At the same concentrations, these agents induced a strong suppression of c-myb mRNA levels within 3 h, whereas c-myc expression remained unaffected. The c-myb expression recovered and approached pretreatment levels at 9-12 h of incubation. The decrease in c-myb mRNA was prevented in Ca(2+)-free medium. Treatment of F4-6 cells with EGTA led to a transient increase in c-myb mRNA with the same kinetics as the Ca2+ pump inhibitor-induced suppression, indicating that c-myb expression is bidirectionally regulated by changes in [Ca2+]i. Studies on the differentiation status of F4-6 cells following cyclopiazonic acid or thapsigargin exposure demonstrated a marked increase in beta-globin mRNA synthesis at 60h and in hemoglobin production at 96 h. These results provide further evidence that a rise in the cytosolic Ca2+ concentration is capable, in Friend erythroleukemia cells, of inducing an early transient suppression of c-myb mRNA levels, which is followed by terminal erythroid differentiation.

Cloning and expression of the gene for the melanoma-associated ME20 antigen

Human melanoma cells, but not tumor cells of other histological origin, express a unique membrane-associated glycoprotein, designated ME20-M, and secrete a soluble glycoprotein, designated ME20-S, defined by monoclonal antibody ME20. Here we report the isolation and characterization of a cDNA clone that when transfected into COS cells directs the expression of ME20-M and ME20-S. This cDNA contains an open reading frame which encodes a 661-amino-acid-long precursor that contains a 23-amino-acid signal peptide and a 26-amino-acid transmembrane domain, separated by a hydrophilic region containing 5 potential Asn-linked and 14 predicted Pro-associated, Thr-linked glycosylation sites. The transmembrane domain is followed by a carboxy-terminal 45-amino-acid putative intracellular domain rich in Ser residues. Analysis of ME20-M by amino acid sequencing identified the proteolytic processing site. Signal peptide cleavage occurs at the Thr-24-Lys-25 peptide bond of the precursor and results in the 637-amino-acid ME20-M with a calculated molecular weight of 67,782. ME20-M is derived from a single 3.3- to 3.4-kb mRNA transcript that is expressed at varying levels in melanoma cell lines, correlating with immunofluorescence determination of protein expression. The amino acid sequence of the ME20 antigen deduced from the cDNA differs from the human neonatal melanocyte-specific Pmel 17 gene product by a single amino acid substitution and deletion of 7 amino acid residues, and it is 80% homologous with the bovine retinal pigment RPE1 cDNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on protein kinase C and inositol phosphate metabolism in primary cultures of rat hepatocytes

Adult rat hepatocytes, after maintenance for 24 h in serum-free culture, were treated with the tumor promoters, 12-O-tetradecanoylphorbol-13-acetate (TPA) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Short-term treatment (15 min) with TPA, 1 microM, increased protein kinase C (PKC) activity in the particulate fraction of hepatocytes and, concomitantly, decreased the vasopressin (100 nM)-stimulated synthesis of inositol phosphates. The latter effect of TPA could be prevented by prior addition of the PKC inhibitor, H7 (100 microM). After short-term treatment (15 min) with TCDD, 1 pM, no effects on PKC or inositol phosphate metabolism were observed. However, after prolonged exposure to TCDD (3-48 h), the particulate PKC was significantly activated (1.5-fold). In contrast to the effect of TPA (24 h), no down-regulation was found. Moreover, long-term treatment with TCDD significantly enhanced vasopressin-stimulated inositol 1,3,4,5-tetrakisphosphate synthesis, while TPA treatment (24 h) stimulated the synthesis of inositol trisphosphates and inositol 1,3,4,5-tetrakisphosphate. The results suggest that the tumor promoters, TPA and TCDD, act differently on the signal transduction pathways in hepatocytes. Thus, the effects of TCDD on PKC and inositol phosphate metabolism might be mediated by a yet unknown mechanism rather than by direct activation of PKC as seen with TPA.

Calcium ionophore-induced transient down-regulation of c-myb mRNA levels in Friend erythroleukemia cells

The effects of calcium ionophores A23187 and ionomycin on the c-myb and c-myc mRNA levels have been investigated in the Friend erythroleukemia cell line F4-6 using Northern blot analysis. Treatment of the cells with 0.5-4 microM A23187 or 1-4 microM ionomycin induced a concentration-dependent decrease in c-myb mRNA; this decrease was abolished by EGTA. c-myc mRNA levels were only moderately affected. After 12-24 h of calcium ionophore exposure, c-myb mRNA returned to pretreatment levels. No similar decrease in c-myb mRNA was seen with the sodium ionophore monensin (up to 16 microM). The dimethyl sulfoxide-induced suppression of c-myb and also of c-myc mRNA levels was not prevented in Ca(2+)-free medium and thus appeared Ca(2+)-independent. A23187 and ionomycin were capable of inducing beta-globin mRNA synthesis in F4-6 cells. Prolonged calcium ionophore exposure, however, strongly reduced cell viability and resulted only in a slight hemoglobin increase at lower concentrations. These results suggest that a rise in [Ca2+]i may be a signal leading to a transient decrease in c-myb mRNA and the initiation of erythroid differentiation in Friend cells. The transient suppression of c-myb mRNA levels represents a common feature of the action of dimethyl sulfoxide and calcium ionophores.