Cancer in the offspring of radiation workers: an investigation of employment timing and a reanalysis using updated dose information.

An earlier case-control study found no evidence of paternal preconceptional irradiation (PPI) as a cause of childhood leukaemia and non-Hodgkin's lymphoma (LNHL). Although fathers of children with LNHL were more likely to have been radiation workers, the risk was most marked in those with doses below the level of detection. The timing of paternal employment as a radiation worker has now been examined. The previously reported elevated risk of LNHL in the children of male radiation workers was limited to those whose fathers were still radiation workers at conception or whose employment also continued until diagnosis. Children whose fathers stopped radiation work prior to their conception were found to have no excess risk of LNHL. It was not possible to distinguish between the risks associated with paternal radiation work at conception and at the time of diagnosis. A reanalysis of the original study hypothesis incorporating updated dosimetric information gave similar results to those obtained previously. In particular, the risks of LNHL did not show an association with radiation doses received by the father before conception. It seems likely that the increased risk of LNHL among the children of male radiation workers is associated with an increased exposure to some infective agent consequent on high levels of population mixing.

Follow up of mortality and incidence of cancer 1952-98 in men from the UK who participated in the UK's atmospheric nuclear weapon tests and experimental programmes.

AIMS: To extend and analyse follow up of mortality and cancer incidence among men who took part in the UK's atmospheric nuclear weapon tests and experimental programmes 40-50 years ago, with particular reference to multiple myeloma and leukaemia. METHODS: A total of 21,357 servicemen and male civilians from the UK who participated in the tests and a control group of 22,333 male controls were followed over the period 1952-98. Analyses were conducted of mortality from various causes, and of mortality and incidence for 27 types of cancer. RESULTS: Rates of mortality from all causes continued to be similar among test participants and controls with the longer follow up, with standardised mortality ratios (SMRs) of 89 and 88 respectively over the full follow up period. For all cancers, the corresponding SMRs were 93 for participants and 92 for controls. Mortality from multiple myeloma was consistent with national rates both for participants and controls, and the relative risk (RR) of myeloma incidence among participants relative to controls was 1.14 (90% CI 0.74 to 1.74) over the full follow up period and 0.79 (90% CI 0.45 to 1.38) during the extended period of follow up (1991-98). Over the full follow up period, leukaemia mortality among participants was consistent with national rates, while rates among controls were significantly lower, and there was a suggestion of a raised risk among test participants relative to controls (RR 1.45, 90% CI 0.96 to 2.17); the corresponding RR for leukaemia incidence was 1.33 (90% CI 0.97 to 1.84). After excluding chronic lymphatic leukaemia (CLL), which is not thought to be radiation inducible, the RR of leukaemia mortality increased to 1.83 (90% CI 1.15 to 2.93), while that for incidence was little changed. Analysis of subgroups of participants with greater potential for exposure provided little evidence of increased risks, although the numbers of men involved were smaller and the statistical power was therefore less. Among other types of cancer, only for liver cancer incidence was there evidence of differences in rates between participants and controls in both the earlier and in the additional period of follow up. Mortality rates among test participants from causes other than cancer were generally similar to those among the controls. CONCLUSIONS: Overall levels of mortality and cancer incidence in UK nuclear weapons test participants have continued to be similar to those in a matched control group, and overall mortality has remained lower than expected from national rates. There was no evidence of an increased raised risk of multiple myeloma among test participants in recent years, and the suggestion in the first analysis of this study of a raised myeloma risk is likely to have been a chance finding. There was some evidence of a raised risk of leukaemia other than CLL among test participants relative to controls, particularly in the early years after the tests, although a small risk may have persisted more recently. This could be a chance finding, in view of low rates among the controls and the generally small radiation doses recorded for test participants. However, the possibility that test participation caused a small absolute risk of leukaemia other than CLL cannot be ruled out.

The HIV-1 transactivator protein Tat is a potent inducer of the human DNA repair enzyme beta-polymerase.

OBJECTIVE: This study examines the effects of the HIV-1 regulatory proteins, Tat and Rev, on the expression of the DNA polymerase beta (beta-pol) gene, which encodes a key protein in the DNA base-excision repair pathway. The rationale for these experiments is to examine the potential involvement of base-excision repair protein deregulation in HIV-1-related lymphomas. DESIGN: Expression of beta-pol mRNA was examined in AIDS-related lymphomas and non-AIDS-related lymphomas and as a function of HIV-1 infection of B cells in culture. The effect of Tat or Rev over-expression on beta-pol promoter expression was tested by transient co-transfection assays with a beta-pol promoter reporter plasmid and a Tat or Rev over-expression plasmid. METHODS: Northern blot analysis was used to quantitate beta-pol expression in lymphoma and cells. Raji cells were co-transfected with a chloramphenicol acetyltransferase (CAT) reporter plasmid and a plasmid over-expressing Tat or Rev. CAT activity was measured in transfected cells. RESULTS: beta-Pol mRNA was > 10-fold higher in AIDS-related than in non-AIDS B-lineage lymphomas. beta-Pol expression was up-regulated in a B-cell line upon infection with HIV-1, and increased in Raji cells upon recombinant expression of the Tat gene. The beta-pol promoter was transactivated (fourfold induction) by Tat, but not by Rev. Tat-dependent transactivation required a binding site for the transcription factor Sp1 in the beta-pol promoter. CONCLUSION: These results suggest that HIV-1 Tat can interact with cellular transcription factors to increase the steady-state level of beta-pol in B cells. Tat-mediated induction of beta-pol may alter DNA stability in AIDS-related lymphomas.

Estrogen metabolism and malignancy: analysis of the expression and function of 17beta-hydroxysteroid dehydrogenases in colonic cancer.

Age and sex differences in the incidence of gastrointestinal cancers suggest the involvement of sex steroids. Post-menopausal loss of estrogen in women appears to be associated with a lower risk of colonic cancer, and studies in vitro have shown that estradiol (E2) stimulates the growth of colonic cancer cell lines. Paradoxically more recent epidemiological data have shown that hormone replacement therapy (HRT) is associated with a lower risk of colonic cancer, although this may reflect differences in the composition and route of administration of HRT regimes. The precise mechanism by which estrogens influence colonic cancer in vivo remains unclear, although E2-induced growth of colonic cancer cells in vitro appears to be dependent on estrogen receptor (ER) expression. We have previously demonstrated differential responses to E2 in pre-malignant and malignant colonic cancer cell lines, without any apparent difference in ER expression. Analogous to well documented studies in breast cancer, we have postulated that local steroid metabolism in the colon may play a key role in modulating the effects of oestrogens by determining the tissue availability of active E2. Using biopsy material we have shown that the normal colonic mucosa has a high level of 17beta-hydroxysteroid dehydrogenase (17beta-HSD)-mediated E2 metabolism. Furthermore, the predominant enzyme activity, inactivation of E2 to estrone (E1), was significantly decreased in paired tumor biopsies. The presence of 17beta-HSD activity in the colon appears to be due to expression of the type 2 and 4 isozymes of 17beta-HSD (17beta-HSD2 and 4), and expression of mRNA for the latter was shown to be significantly decreased in tumours compared to normal mucosa. Further studies have characterised the expression of 17beta-HSD2 and 4 in colonic epithelial cells and in colonic cancer cell lines, and have suggested a link between estrogen metabolism and colonic cell proliferation. Data reviewed here provide evidence for the importance of 17beta-HSD isozymes as attenuators of E2 bioavailability in the colon, and emphasise a possible role for 17beta-HSD2 and 4 in the pathogenesis of colon cancer.

Oestrogen inactivation in the colon: analysis of the expression and regulation of 17beta-hydroxysteroid dehydrogenase isozymes in normal colon and colonic cancer.

Epidemiological data suggest that oestrogen contributes to the aetiology of colonic cancer. Furthermore, recent studies have suggested that local hormone metabolism may play a key role in determining colonic responsiveness to oestrogen. To further clarify this mechanism we have characterized the expression and regulation of isozymes of 17beta-hydroxysteroid dehydrogenase (17beta-HSD) in vitro and in situ. Immunohistochemistry was used to confirm expression of the type 2 and 4 isozymes of 17beta-HSD (17beta-HSD2 and 4) in normal colonic epithelial cells. Parallel studies suggested that both isozymes were abnormally expressed in colonic tumours and this was confirmed by Western blot analyses. Abnormal expression of 17beta-HSD2 and 4 proteins was also observed in Caco-2, HT-29 and SW620 colonic cancer cell lines, although the overall pattern of oestrogen metabolism in these cells was similar to that seen in primary colonic mucosal tissue. The predominant activity (conversion of oestradiol to oestrone) was highest in Caco-2>SW620>HT-29, which correlated inversely with the rate of proliferation of the cell lines. Regulatory studies using SW620 cells indicated that the most potent stimulator of oestradiol to oestrone inactivation was the antiproliferative agent 1,25-dihydroxyvitamin D3 (1,25D3), whilst oestradiol itself inhibited 17beta-HSD activity. Both oestradiol and 1,25D3 decreased mRNA for 17beta-HSD2 and 4. Data indicate that the high capacity for inactivation of oestrogens in the colon is associated with the presence of 17beta-HSD2 and 4 in epithelial cells. Abnormal expression of both isozymes in colonic cancer cells and the stimulation of oestrogen inactivation by the antiproliferative agent 1,25D3 highlights a possible role for 17beta-HSD isozymes as modulators of colonic cell proliferation.

E-cadherin is a WT1 target gene.

The WT1 tumor suppressor gene encodes a transcription factor that can activate and repress gene expression. Transcriptional targets relevant for the growth suppression functions of WT1 are poorly understood. We found that mesenchymal NIH 3T3 fibroblasts stably expressing WT1 exhibit growth suppression and features of epithelial differentiation including up-regulation of E-cadherin mRNA. Acute expression of WT1 in NIH 3T3 fibroblasts after retroviral infection induced murine E-cadherin expression. In transient transfection experiments, the human and murine E-cadherin promoters were activated by co-expression of WT1. E-cadherin promoter activity was increased in cells overexpressing WT1 and was blocked by a dominant negative form of WT1. WT1 activated the murine E-cadherin promoter through a conserved GC-rich sequence similar to an EGR-1 binding site as well as through a CAAT box sequence. WT1 produced in vitro or derived from nuclear extracts bound to the WT1-response element within the murine E-cadherin promoter, but not the CAAT box. E-cadherin, a gene important in epithelial differentiation and neoplastic transformation, represents a downstream target gene that links the roles of the WT1 in differentiation and growth control.

Loss of estrogen inactivation in colonic cancer.

Age and sex differences in the incidence of colonic cancer, together with epidemiological data on patients taking hormone replacement therapy, suggest the involvement of estrogens. Analogous to the role of aromatase in breast cancer, we postulated that steroid metabolism within the colon itself may be a crucial mechanism in regulating tissue exposure to estrogens. We have characterized expression of aromatase (responsible for converting C19 androgens to C18 estrogens) and 17beta-hydroxysteroid dehydrogenase (17beta-HSD) [responsible for interconversion of active estradiol (E2) to less potent estrone (E1)] in normal and neoplastic human colon from 24 patients undergoing tumor resection. Aromatase activity was similar in homogenates from normal mucosa, tissue adjacent to tumors, and the tumors themselves. Analysis of 17beta-HSD activity indicated that the predominant activity was oxidative (E2 to E1), and this conversion was significantly lower in colonic tumors [444 (90-1735); median (95% confidence interval) pmol/mg protein x h], compared with normal mucosa [1709 (415-13828), P < 0.001]. Northern blot analyses indicated expression of messenger RNAs (mRNAs) for the type 2 and 4 isozymes of 17beta-HSD in normal colon; messenger RNA for 17beta-HSD 4 was significantly lower in tumor tissue [0.75 +/- 0.22 (mean +/- SD) arbitrary U vs. 0.43 +/- 0.17, P < 0.01]. Studies in vitro, using three colonic cancer cell lines, indicated that there was an inverse correlation between 17beta-HSD oxidative activity and the rate of cell proliferation. In addition, E1, but not E2, was shown to significantly decrease proliferation when added exogenously to the colonic epithelial cell line, SW620 cells. Colonic mucosa can regulate estrogen hormone action in an intracrine fashion. The loss of estrogen inactivation may be an important mechanism in the pathogenesis of colonic cancer.

Tumor-associated WT1 missense mutants indicate that transcriptional activation by WT1 is critical for growth control.

The WT1 gene encodes a zinc finger DNA binding transcription factor and is mutated in up to 15% of Wilms tumor cases. The WT1 protein binds to the promoters of many genes through GC- or TC-rich sequences and can function both as a transcriptional repressor and an activator in co-transfection assays depending on the cell type, the structure of the test promoter, and even the expression vectors used. Engineered expression of WT1 can lead to growth suppression by both cell cycle arrest and induction of apoptosis. However, the transcriptional activity of WT1 that is required for growth control was not defined. We found that three N-terminal tumor-associated missense mutations of WT1 were defective for activation of both a synthetic reporter containing WT1-binding sites as well as the promoter of a WT1 responsive gene, p21. These mutants failed to inhibit cell growth but still retain their ability to repress several putative WT1 target promoters. These results indicate that activation and not repression by WT1 is the critical transcriptional activity of the protein responsible for its growth suppressing properties.

Sequence-specific DNA binding and transcriptional regulation by the promyelocytic leukemia zinc finger protein.

Chromosomal translocation t(11;17)(q23;21) is associated with a retinoic acid-resistant form of acute promyelocytic leukemia. The translocation fuses the RARalpha gene to the PLZF gene, resulting in the formation of reciprocal fusion proteins, hypothesized to play prominent roles in leukemogenesis. Promyelocytic leukemia zinc finger (PLZF) encodes a transcription factor with nine Krüppel-like zinc fingers, seven of which are retained in the t(11;17) fusion protein RARalpha-PLZF. We identified a specific DNA-binding site for the PLZF protein and showed that PLZF binds to this site through its most carboxyl seven zinc fingers. In co-transfection experiments, PLZF repressed transcription through its cognate binding site. This repression function of PLZF was mapped to two regions on the protein, including the evolutionarily conserved POZ domain. In contrast, the RARalpha-PLZF protein activated transcription of a promoter containing a PLZF response element. These results suggest that RARalpha-PLZF, generated in acute promyelocytic leukemia, is an aberrant transcription factor that can deregulate the expression of PLZF target genes and contribute to leukemogenesis.

Reduced and altered DNA-binding and transcriptional properties of the PLZF-retinoic acid receptor-alpha chimera generated in t(11;17)-associated acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) associated with chromosomal rearrangement t(11;17) is a distinct syndrome which, unlike typical t(15;17) APL, fails to respond to all-trans retinoic acid (ATRA) therapy. In t(11;17) the PLZF gene, encoding a Krüppel-like zinc finger protein, is fused to the retinoic acid receptor-alpha (RAR alpha) gene, yielding two classes of chimeric proteins. PLZF protein was found in the nucleus in a punctate speckled pattern that differed from the nuclear body expression pattern of the PML protein affected in t(15;17) APL. The reciprocal PLZF-RAR alpha and RAR alpha-PLZF fusion proteins were localized to the nucleus both in the presence and absence of ATRA. PLZF-RAR alpha, in combination with the retinoid X receptor (RXR) bound to a retinoic acid-responsive element (RARE) less efficiently than RAR alpha and formed multimeric DNA-protein complexes. PLZF-RAR alpha stimulated ATRA-dependent transcription of RARE-containing reporter genes with diminished activity compared to wild-type RAR alpha. In addition, PLZF-RAR alpha antagonized the function of coexpressed wild-type RAR alpha, an effect relieved by over-expression of RXR. Leukemogenesis in t(11;17) APL may be related to interference with ATRA-mediated differentiation due to sequestration of RXR by the PLZF-RAR alpha chimera. However, disruption of the function of the myeloid-specific PLZF protein may also play an important role.

Ablation and chemistry of meteoric materials in the atmosphere of Titan.

We compute the input of meteoric materials expected on Titan, and integrate this dust model with an ablation model and a comprehensive chemical model, investigating the effects on the atmosphere and surface. We find that a water deposition of approximately 10-100 times the expected interplanetary dust flux, or a recent large impact, is required to produce the observed CO2 abundance. Ionisation due to meteoric activity is not likely to be higher than that due to other sources.

Congestive heart failure: public and private burden.

Chronic congestive heart failure (CHF) is a common yet devastating syndrome. CHF is a leading cause of morbidity and mortality in the United States and other industrialized countries. The incidence and prevalence of CHF is increasing, placing a growing burden on the health care system. Patients suffering from CHF report a poor quality of life because of physical symptoms, functional disability, emotional and economic burdens, frequent hospitalizations, and poor prognosis. Nurses play a key role in the identification of strategies for effective management of CHF.

Dynamic cardiomyoplasty.

Dynamic cardiomyoplasty, which uses transformed fatigue-resistant skeletal muscle to augment ventricular function, is an experimental surgical technique that shows promise as a treatment for patients suffering from heart failure. Successful management of this challenging patient population requires knowledge of (1) skeletal muscle physiology and management of muscle training, (2) details of the surgical procedure, and (3) patient management priorities.

WT1-mediated transcriptional activation is inhibited by dominant negative mutant proteins.

The WT1 tumor suppressor gene encodes four isoforms of a zinc finger transcription factor with both activation and repression functions which are dependent upon promoter architecture. Using a simple HSV-tk promoter containing 5'-Egr-1/WT1-binding sites, we found that WT1 isoforms (A) and (B) strongly activated transcription. WT1(A) and (B) bound equally well to the Egr-1/WT1-binding site, but WT1(B), which contains a 17 amino acid insertion compared to WT1(A), was a consistently stronger activator of transcription than WT1(A). Transcriptional activation by wild-type WT1 was inhibited by coexpression of WT(PM) or WT(AR), genetically defined dominant negative alleles of WT1. In vitro, as well as in the yeast two-hybrid system, WT1 protein associated with itself and with dominant negative mutant proteins. The major domain required for self-association and inhibition of transcriptional activation mapped to the first 182 amino acids of WT1. Dominant negative WT1 alleles may play a role in tumorigenesis by associating with wild-type WT1 proteins and decreasing their transcriptional activity.

Mapping and mutagenesis of the amino-terminal transcriptional repression domain of the Drosophila Krüppel protein.

We previously demonstrated that the Drosophila Krüppel protein is a transcriptional repressor with separable DNA-binding and transcriptional repression activities. In this study, the minimal amino (N)-terminal repression region of the Krüppel protein was defined by transferring regions of the Krüppel protein to a heterologous DNA-binding protein, the lacI protein. Fusion of a predicted alpha-helical region from amino acids 62 to 92 in the N terminus of the Krüppel protein was sufficient to transfer repression activity. This putative alpha-helix has several hydrophobic surfaces, as well as a glutamine-rich surface. Mutants containing multiple amino acid substitutions of the glutamine residues demonstrated that this putative alpha-helical region is essential for repression activity of a Krüppel protein containing the entire N-terminal and DNA-binding regions. Furthermore, one point mutant with only a single glutamine on this surface altered to lysine abolished the ability of the Krüppel protein to repress, indicating the importance of the amino acid at residue 86 for repression. The N terminus also contained an adjacent activation region localized between amino acids 86 and 117. Finally, in accordance with predictions from primary amino acid sequence similarity, a repression region from the Drosophila even-skipped protein, which was six times more potent than that of the Krüppel protein in the mammalian cells, was characterized. This segment included a hydrophobic stretch of 11 consecutive alanine residues and a proline-rich region.

Selective repression of transcriptional activators at a distance by the Drosophila Krüppel protein.

The Krüppel (Kr) protein, bound at kilobase distances from the start site of transcription, represses transcription by RNA polymerase II in mammalian cells. Repression is monotonically dependent on the dose of Kr protein and the presence of Kr binding site(s) on the DNA. These data suggest an inhibitory protein-protein interaction between the Kr protein and proximal transcription factors. Repression by Kr depends on the specific activator protein driving transcription. In particular, Kr protein selectively represses transcription mediated by the Sp1 glutamine-rich activation domain, tethered to the promoter by a GAL4 DNA-binding domain, but does not repress transcription stimulated by the acidic GAL4 activator. We believe this represents repression by a quenching interaction between DNA-bound Kr protein and the activation region of Sp1, rather than competition between Sp1 and Kr for a limiting transcriptional component. Selective, context-related repression affords an added layer of combinatorial control of gene expression by sequence-specific transcription factors.

NGFIA (EGR1) contains transcription activating domains in both the amino terminal and carboxyl terminal regions of the protein.

We constructed and tested a number of lac repressor fusion proteins containing various portions of the zinc-finger containing protein NGFIA for their ability to stimulate transcription of a reporter gene containing lac operators. NGFIA contains two transcription activation regions, found in two distinct regions of the protein. The carboxyl (C) terminal portion of the molecule contains a weak activation domain, including five tandem copies of an eight amino acid repeat (T/S,T/S,F/Y,P,S,P,X,X). These five tandem copies of the repeated sequence activated reporter gene transcription 4-7 fold. Amino acids 1 through 293 in the amino (N) terminus of NGFIA function as a strong transcription activation domain stimulating transcription up to 80-fold. Fusions including amino acids 1-393 failed to activate transcription, indicating the presence of a domain capable of suppressing the N-terminal transcriptional activation function.

Preventing complications of ventricular assist devices.

Ventricular assist devices can provide temporary circulatory support to the failing heart. The critical care nurse prevents complications during both treatment and weaning of patients who are on ventricular assist devices.