Estrogen Receptor Alpha Signaling Is Responsible for the Female Sex Bias in the Loss of Tolerance and Immune Cell Activation Induced by the Lupus Susceptibility Locus Sle1b

The dramatic female sex bias observed in human lupus is thought to be due, at least in part, to estrogens. Using mouse models, we have shown that estrogens, acting through estrogen receptor alpha (ERα) promote lupus development and contribute significantly to the female sex bias observed in this disease. C57Bl/6 (B6) mice carrying the lupus susceptibility locus Sle1 locus exhibit immune cell hyperactivation and loss of tolerance, and the action of Sle1 displays a strong female sex bias. Previously, we showed that disruption of ERα completely eliminates the female sex bias in the effects of Sle1. Here we report that ERα signaling selectively modulates the action of Sle1b, one of the three subloci that together constitute Sle1. We observed that disruption of ERα signaling attenuated T cell hyperactivation, formation of spontaneous germinal centers, loss of tolerance, and the development of anti-chromatin autoantibodies in B6.Sle1b female mice, but had no impact on these phenotypes in B6.Sle1b male mice. In fact, disruption of ERα completely abolished the female sex bias that is seen in each of these phenotypes in B6.Sle1b mice. Strikingly, Sle1b-induced B cell hyperactivation, a female sex-specific manifestation of Sle1b, was completely abrogated by disruption of ERα in B6.Sle1b females. Altogether, these results demonstrate that ERα signaling is responsible for the female sex bias in the actions of Sle1b, and is absolutely required for the female-specific B cell hyperactivation phenotype associated with this lupus susceptibility locus. By contrast, we found that ERα signaling had no impact on Sle1a, the other Sle1 sublocus that exerts effects that show a female sex bias.

Sequence determinants of DNA binding by the hematopoietic helix-loop-helix transcription factor TAL1: importance of sequences flanking the E-box core

TAL1 is a helix-loop-helix transcription factor that is essential for hematopoiesis. In vitro DNA binding site selection experiments have previously identified the preferred binding site for TAL1 heterodimers as AACAGATGGT. TAL1 homodimers do not bind DNA with significant affinity. A subset of other E-box sequences is also bound by TAL1 heterodimers. Here, we present an analysis of TAL1 heterodimer DNA binding specificity, using E-boxes derived from genomic clones, which were isolated by immunoadsorption of K562 erythroleukemia cell chromatin with a TAL1 antibody. We show that TAL1 heterodimer binding to a CAGATG E-box is strongly modulated by nucleotides flanking the E-box. A 10 base pair element consisting of the CAGATG E-box and two flanking nucleotides in both the 5' and 3' direction is sufficient for high-affinity binding. Certain mutations of nucleotides in either the 5' (-1 and -2) or 3' (+1 and +2) direction strongly inhibit binding. The importance of flanking nucleotides also exists in the context of nonpreferred E-boxes recognized by TAL1 heterodimers. Although there are no known target genes for TAL1, the regulatory regions of several genes involved in hematopoiesis contain the preferred E-box CAGATG. However, based on our results, the E-boxes in these potential target genes contain flanking sequences that would be expected to significantly reduce TAL1 heterodimer binding in vitro. Thus, additional stabilizing forces, such as protein-protein interactions between TAL1 heterodimers and accessory factors, may be required to confer high-affinity TAL1 heterodimer binding to such sequences.

Evaluation of Rint1 as a modifier of intestinal tumorigenesis and cancer risk

The Rad50 Interacting Protein 1 (Rint1) influences cellular homeostasis through maintenance of endoplasmic reticulum, Golgi and centrosome integrity and regulation of vesicle transport, autophagy and the G₂/M checkpoint. Rint1 has been postulated to function as a tumor suppressor as well as an oncogene, with its role depending perhaps upon the precise cellular and/or experimental context. In humans, heterozygosity for germline missense variants in RINT1 have, in some studies, been associated with increased risk of both breast and Lynch syndrome type cancers. However, it is not known if these germline variants represent loss of function alleles or gain of function alleles. Based upon these findings, as well as our initial consideration of Rint1 as a potential candidate for Mom5, a genetic modifier of intestinal tumorigenesis in Apc^Min/+ mice, we sought to explicitly examine the impact of Rint1 on tumorigenesis in Apc^Min/+ mice. However, heterozygosity for a knockout of Rint1 had no impact on tumorigenesis in Rint1^+/-; Apc^Min/+ mice. Likewise, we found no evidence to suggest that the remaining Rint1 allele was lost somatically in intestinal tumors in Apc^Min/+ mice. Interestingly, in contrast to what has been observed in Rint1^+/- mice on a mixed genetic background, Rint1^+/- mice on a pure C57BL/6J background did not show spontaneous tumor development. We also evaluated colorectal cancer data available in the COSMIC and ONCOMINE databases and found that RINT1 overexpression, as well as the presence of somatic missense mutations in RINT1 were associated with colorectal cancer development. In vitro evaluation of two missense variants in RINT1 suggested that such variants do have the potential to impact RINT1 function.

An Lck-cre transgene accelerates autoantibody production and lupus development in (NZB × NZW)F1 mice

Lupus is an autoimmune disease characterized by the development of antinuclear autoantibodies and immune complex-mediated tissue damage. T cells in lupus patients appear to undergo apoptosis at an increased rate, and this enhanced T cell apoptosis has been postulated to contribute to lupus pathogenesis by increasing autoantigen load. However, there is no direct evidence to support this hypothesis. In this study, we show that an Lck-cre transgene, which increases T cell apoptosis as a result of T cell-specific expression of cre recombinase, accelerates the development of autoantibodies and nephritis in lupus-prone (NZB × NZW)F1 mice. Although the enhanced T cell apoptosis in Lck-cre transgenic mice resulted in an overall decrease in the relative abundance of splenic CD4(+) and CD8(+) T cells, the proportion of activated CD4(+) T cells was increased and no significant change was observed in the relative abundance of suppressive T cells. We postulate that the Lck-cre transgene promoted lupus by enhancing T cell apoptosis, which, in conjunction with the impaired clearance of apoptotic cells in lupus-prone mice, increased the nuclear antigen load and accelerated the development of anti-nuclear autoantibodies. Furthermore, our results also underscore the importance of including cre-only controls in studies using the cre-lox system.

Genetic dissection of the Mom5 modifier locus and evaluation of Mom5 candidate genes

Germline mutations in the adenomatous polyposis coli (APC) gene cause familial adenomatous polyposis (FAP), a hereditary colon cancer syndrome in which affected individuals may develop 100-1000s of colonic adenomas. In families affected by FAP, adenoma number can vary markedly between individuals, despite the fact that these individuals carry the same APC mutation. In at least some FAP pedigrees, evidence suggests that these phenotypic differences are caused by segregating modifier alleles that impact adenoma number. However, identifying these modifiers in the human population is difficult, therefore mouse models are essential. Using the Apc (Min/+) mouse colon cancer model, we previously mapped one such modifier, Mom5, to a 25 Mbp region of chromosome 5 that contains hundreds of genes. The purpose of the present study was to refine the Mom5 interval and evaluate candidate genes for the Mom5 modifier of intestinal neoplasia. Recombinant mice were used to narrow the Mom5 interval to 8.1 Mbp containing 70 genes. In silico and gene expression analyses were utilized to identify and evaluate potential candidate genes that reside within this interval. These analyses identified seven genes within the Mom5 interval that contain variants between the B6 and 129P2 strains. These genes represent the most likely candidates for the Mom5 modifier.

Estrogen receptor alpha signaling promotes Sle1-induced loss of tolerance and immune cell activation and is responsible for sex bias in B6.Sle1 congenic mice

Sex bias in lupus incidence is thought to be due, in part, to the ability of estrogens to promote loss of tolerance. Previously, we showed that estrogens promote lupus via estrogen receptor α (ERα). C57BL/6 (B6) mice carrying the Sle1 lupus susceptibility locus (B6.Sle1) display loss of tolerance and develop anti-nuclear antibodies and immune cell hyperactivation. The incidence of loss of tolerance in B6.Sle1 females is greater than in males. Here, we show that a deficiency of either estrogens or ERα attenuates loss of tolerance and autoantibody development in B6.Sle1 females. Furthermore, we demonstrate that immune cell activation in B6.Sle1 mice shows sex bias and that ERα deficiency diminishes this phenotype in B6.Sle1 females. Thus, estrogens, acting via ERα, control sex bias in the Sle1 phenotype. Furthermore, we show that ERα may impact the Sle1 phenotype by modulating the expression of Pbx1, one of genes that underlies the Sle1 locus.

Genome sequencing and characterization of an extensively drug-resistant sequence type 111 serotype O12 hospital outbreak strain of Pseudomonas aeruginosa

A series of extensively drug-resistant isolates of Pseudomonas aeruginosa from two outbreaks in UK hospitals were characterized by whole genome sequencing (WGS). Although these isolates were resistant to antibiotics other than colistin, we confirmed that they are still sensitive to disinfectants. The sequencing confirmed that isolates in the larger outbreak were serotype O12, and also revealed that they belonged to sequence type ST111, which is a major epidemic strain of P. aeruginosa throughout Europe. As this is the first reported sequence of an ST111 strain, the genome was examined in depth, focusing particularly on antibiotic resistance and potential virulence genes, and on the reported regions of genome plasticity. High degrees of sequence similarity were discovered between outbreak isolates collected from recently infected patients, isolates from sinks, an isolate from the sewer, and a historical isolate, suggesting that the ST111 strain has been endemic in the hospital for many years. The ability to translate easily from outbreak investigation to detailed genome biology by use of the same data demonstrates the flexibility of WGS application in a clinical setting.

A dexamethasone prodrug reduces the renal macrophage response and provides enhanced resolution of established murine lupus nephritis

We evaluated the ability of a macromolecular prodrug of dexamethasone (P-Dex) to treat lupus nephritis in (NZB × NZW)F1 mice. We also explored the mechanism underlying the anti-inflammatory effects of this prodrug. P-Dex eliminated albuminuria in most (NZB × NZW)F1 mice. Furthermore, P-Dex reduced the incidence of severe nephritis and extended lifespan in these mice. P-Dex treatment also prevented the development of lupus-associated hypertension and vasculitis. Although P-Dex did not reduce serum levels of anti-dsDNA antibodies or glomerular immune complexes, P-Dex reduced macrophage recruitment to the kidney and attenuated tubulointerstitial injury. In contrast to what was observed with free dexamethasone, P-Dex did not induce any deterioration of bone quality. However, P-Dex did lead to reduced peripheral white blood cell counts and adrenal gland atrophy. These results suggest that P-Dex is more effective and less toxic than free dexamethasone for the treatment of lupus nephritis in (NZB × NZW)F1 mice. Furthermore, the data suggest that P-Dex may treat nephritis by attenuating the renal inflammatory response to immune complexes, leading to decreased immune cell infiltration and diminished renal inflammation and injury.

Accelerated development of chronic lymphocytic leukemia in New Zealand Black mice expressing a low level of interferon regulatory factor 4

A recent genome-wide SNP association study identified IRF4 as a major susceptibility gene for chronic lymphocytic leukemia (CLL). Moreover, the SNPs located in the 3' UTR of the IRF4 gene have been linked to a down-regulation of IRF4. However, whether a low level of IRF4 is critical for CLL development remains unclear. New Zealand Black (NZB) mice are a naturally occurring, late-onset mouse model of CLL. To examine the role of a reduced level of IRF4 in CLL development, we generated, through breeding, IRF4 heterozygous mutant mice in the NZB background (NZB IRF4(+/-)). Our results show that CLL development is accelerated dramatically in the NZB IRF4(+/-) mice. The average onset of CLL in NZB mice is 12 months, but CLL cells can be detected in NZB IRF4(+/-) mice at 3 months of age. By 5 months of age, 80% of NZB IRF4(+/-) mice developed CLL. CLL cells are derived from B1 cells in mice. Interestingly, NZB IRF4(+/-) B1 cells exhibit prolonged survival, accelerated self-renewal, and defects in differentiation. Although NZB IRF4(+/-) CLL cells are resistant to apoptosis, high levels of IRF4 inhibit their survival. High levels of IRF4 also reduce the survival of MEC-1 human CLL cells. Our analysis further reveals that high levels of IRF4 suppress Akt activity and can do so without the IRF4 DNA binding domain. Thus, our findings reveal a causal relationship between a low level of IRF4 and the development of CLL and establish IRF4 as a novel regulator in the pathogenesis of CLL.

Dexamethasone prodrug treatment prevents nephritis in lupus-prone (NZB × NZW)F1 mice without causing systemic side effects

OBJECTIVE

To evaluate the potentially improved therapeutic efficacy and safety of nephrotropic macromolecular prodrugs of glucocorticoids (GCs) for the treatment of lupus nephritis.

METHODS

Lupus-prone female (NZB × NZW)F1 mice received monthly injections of N-(2-hydroxypropyl) methacrylamide copolymer-based dexamethasone prodrug (P-Dex) or daily injections of dexamethasone phosphate sodium (Dex; overall dose equivalent to that of P-Dex) for 2 months. During treatment, the mice were monitored for albuminuria, mean arterial pressure, and serum autoantibody levels. Nephritis, renal immune complex levels, and macrophage infiltration were evaluated histologically. Bone quality was analyzed using peripheral dual x-ray absorptiometry and micro-computed tomography. The in vivo distribution of P-Dex was investigated using optical imaging, immunohistochemistry, and fluorescence-activated cell sorting (FACS). The antiinflammatory effect of P-Dex was validated using lipopolysaccharide-activated human proximal tubule epithelial (HK-2) cells.

RESULTS

Monthly P-Dex injections completely abolished albuminuria in the (NZB × NZW)F1 mice; this approach was significantly more efficacious than daily Dex treatment. P-Dex treatment did not reduce serum levels of anti-double-stranded DNA antibodies or renal immune complexes but did decrease macrophage infiltration, which is a marker of chronic inflammation. Immunohistochemical and FACS analyses revealed that P-Dex was primarily sequestered by proximal tubule epithelial cells, and that it could attenuate the inflammatory response in HK-2 cell culture. In contrast to Dex treatment, P-Dex treatment did not lead to any significant deterioration of bone quality or reduction in the level of total serum IgG.

CONCLUSION

Macromolecularization of GCs renders them nephrotropic. Protracted retention, subcellular processing, and activation of GC prodrugs by kidney cells would potentiate nephritis resolution, with a reduced risk of systemic toxicities.

Impact of interactions of cigarette smoking with NAT2 polymorphisms on rheumatoid arthritis risk in African Americans

OBJECTIVE

To examine whether polymorphisms in genes coding for drug-metabolizing enzymes (DMEs) have an impact on rheumatoid arthritis (RA) risk due to cigarette smoking in African Americans.

METHODS

Smoking status was evaluated in African American patients with RA compared with non-RA controls, with smoking exposure categorized as heavy smoker (≥10 pack-years) versus never smoker/<10 pack-years. Individuals were genotyped for a homozygous deletion polymorphism in the M1 gene loci of glutathione S-transferase (GSTM1-null) in addition to tagging single-nucleotide polymorphisms (SNPs) in N-acetyltransferase 1 (NAT1), NAT2, and epoxide hydrolase 1 (EPXH1). Associations of these genotypes with RA risk were examined using logistic regression, and gene-smoking interactions were assessed.

RESULTS

There were no significant associations of any DME genotype with RA. After adjustment for multiple comparisons, there were significant additive interactions between heavy smoking and the NAT2 SNPs rs9987109 (P(additive) = 0.000003) and rs1208 (P(additive) = 0.00001); the attributable proportion due to interaction ranged from 0.61 to 0.67. None of the multiplicative gene-smoking interactions examined remained significant with regard to overall disease risk, after adjustment for multiple testing. There was no evidence of significant gene-smoking interactions in analyses of GSTM1-null, NAT1, or EPXH1. DME gene-smoking interactions were similar when cases were limited to those patients who were positive for anti-citrullinated protein antibodies.

CONCLUSION

Among African Americans, RA risk imposed by heavy smoking appears to be mediated in part by genetic variation in NAT2. While further studies are needed to elucidate the mechanisms underpinning these interactions, these SNPs appear to identify African American smokers at a much higher risk for RA, in whom the relative risk is at least 2-fold higher when compared to nonsmokers lacking these risk alleles.

Variation at the capsule locus, cps, of mistyped and non-typable Streptococcus pneumoniae isolates

The capsule polysaccharide locus (cps) is the site of the capsule biosynthesis gene cluster in encapsulated Streptococcus pneumoniae. A set of pneumococcal samples and non-pneumococcal streptococci from Denmark, the Gambia, the Netherlands, Thailand, the UK and the USA were sequenced at the cps locus to elucidate serologically mistyped or non-typable isolates. We identified a novel serotype 33B/33C mosaic capsule cluster and previously unseen serotype 22F capsule genes, disrupted and deleted cps clusters, the presence of aliB and nspA genes that are unrelated to capsule production, and similar genes in the non-pneumococcal samples. These data provide greater understanding of diversity at a locus which is crucial to the antigenic diversity of the pathogen and current vaccine strategies.

Associations of cigarette smoking with rheumatoid arthritis in African Americans

OBJECTIVE

To examine the associations of cigarette smoking with rheumatoid arthritis (RA) in African Americans, and to determine whether this association is impacted by the HLA-DRB1 shared epitope (SE).

METHODS

Smoking status, cumulative smoking exposure, and SE status were determined in African American patients with RA and African American healthy controls. Associations of smoking with RA were examined using age- and sex-adjusted logistic regression analyses. Additive and multiplicative SE-smoking interactions were examined.

RESULTS

After adjustment for age and sex, ever smoking (odds ratio [OR] 1.45, 95% confidence interval [95% CI] 1.07, 1.97) and current smoking (OR 1.56, 95% CI 1.07, 2.26), relative to never smoking, were more common in African American patients with RA (n = 605) than in controls (n = 255). The association of smoking with RA was limited to those with a cumulative exposure exceeding 10 pack-years, associations that were evident both in autoantibody-positive and in autoantibody-negative disease. There was evidence of a significant additive interaction between SE status and heavy smoking (≥10 pack-years) in relation to RA risk (attributable proportion [AP] due to interaction 0.58, P = 0.007), with similar results for the additive interaction between SE status and ever smoking (AP 0.47, P = 0.006). There was no evidence of multiplicative interactions.

CONCLUSION

Among African Americans, cigarette smoking is associated not only with the risk of autoantibody-positive RA but also with the risk of autoantibody-negative disease. The risk of RA attributable to smoking is limited to African Americans with more than 10 pack-years of exposure and is more pronounced among individuals positive for the HLA-DRB1 SE.

Gender-dependent expression of murine Irf5 gene: implications for sex bias in autoimmunity

Molecular mechanisms that contribute to sex bias in the development of systemic lupus erythematosus (SLE), an autoimmune disease, remain unknown. We found that the expression levels of interferon regulatory factor 5 (IRF5), a lupus susceptibility factor, depend on gender of mice. We found that steady-state levels of the Irf5 mRNA were relatively higher in splenic cells from certain autoimmune-prone mice (for example, NZB and NZB/W F(1)) than in non-autoimmune C57BL/6 mice. Additionally, levels of Irf5 mRNA and protein were higher in females than in strain and age-matched males. Accordingly, splenic cells from estrogen receptor-alpha (ERα) knockout, when compared with the wild-type (ERα(+/+)), female mice expressed relatively lower levels of Irf5 mRNA and the treatment of splenic cells with 17β-estradiol increased the levels. Furthermore, splenic B cells from the female mice had relatively more IRF5 protein in the nucleus than the male mice. Collectively, our observations demonstrate a gender bias in the expression and sub-cellular localization of the murine IRF5.

Female and male sex hormones differentially regulate expression of Ifi202, an interferon-inducible lupus susceptibility gene within the Nba2 interval

Increased expression of IFN-inducible Ifi202 gene in certain strains of female mice is associated with susceptibility to systemic lupus erythematosus (SLE). Although, the development of SLE is known to have a strong sex bias, the molecular mechanisms remain unknown. Here we report that in vivo treatment of orchiectomized (NZB x NZW)F(1) male mice with the female sex hormone 17beta-estradiol significantly increased steady-state levels of Ifi202 mRNA in splenic cells, whereas treatment with the male hormone dihydrotestosterone decreased the levels. Moreover, increased expression of Ifi202 in B6.Nba2 B cells and reduced expression in T cells were associated with increased levels of estrogen receptor-alpha (ERalpha) and androgen receptor, respectively. Furthermore, the steady-state levels of Ifi202 mRNA were higher in splenic cells from C57BL/6, B6.Nba2, NZB, and (NZB x NZW)F(1) female mice as compared with males. 17beta-estradiol treatment of B cells and WT276 cells increased Ifi202 mRNA levels, whereas treatment with dihydrotestosterone decreased the levels. Interestingly, overexpression of ERalpha in WT276 cells increased the expression of Ifi202 and stimulated the activity of the 202-luc-reporter through the c-Jun/AP-1 DNA-binding site. Accordingly, ERalpha preferentially associated with the regulatory region of the Ifi202 gene in female B6.Nba2 B cells than in males. Furthermore, Ifi202 mRNA levels were detectable in splenic cells of wild-type (Esr1(+/+)), but not null (Esr1(-/-)), (NZB x NZW)F(1) female mice. Collectively, our observations demonstrate that the female and male sex hormones differentially regulate the expression of Ifi202, thus providing support for the role of Ifi202 in sex bias in SLE.

Genetic diversity in CC398 methicillin-resistant Staphylococcus aureus isolates of different geographical origin

Staphylococcus aureus of sequence type 398 has emerged in Europe, North America and Asia, and has typically been associated with livestock and their human contacts. We analysed two Panton-Valentine leukocidin (PVL)-negative t034-ST398 isolates from humans in contact with pigs and two t034-ST398 PVL-positive isolates from two unrelated, adopted Chinese children, using multistrain microarrays to determine genomic variability between the two sets of isolates. The ST398 isolates clearly belong to the same lineage when compared to other clonal lineages. However, the four isolates cluster into two distinct groups corresponding to differences in epidemiology based on mobile genetic elements and resistance patterns, suggesting that the two groups are epidemiologically distinct.

Genetic mapping of Mom5, a novel modifier of Apc(Min)-induced intestinal tumorigenesis

The initial purpose of this study was to assess the role of estrogen receptor beta (ERbeta) in intestinal tumorigenesis by examining the effects of an ERbeta knockout (ERbeta(-/-)) on Apc(Min) mice. In order to accomplish this goal on a uniform genetic background, we were required to backcross the ERbeta knockout from the 129P2 genetic background to the B6 genetic background for 10 generations. Midway through this process, we performed a test cross in which mice from the N(5) backcross generation of the ERbeta knockout strain were intercrossed with Apc(Min/+) mice to obtain Apc(Min/+) ERbeta(+/+), Apc(Min/+) ERbeta(+/-) and Apc(Min/+) ERbeta(-/-) mice. Intestinal tumorigenesis in the N(5)F(2) mice was evaluated at 14 weeks of age. The analysis of the impact of ERbeta in the N(5) cross was complicated by segregating 129P2-derived alleles that affected tumor number and were unlinked to ERbeta. Genetic linkage analysis of this cross permitted the localization of a single genetic modifier of tumor number in Apc(Min/+) mice. This locus, Modifier of Min 5 (Mom5), maps to proximal mouse chromosome 5; the 129P2 allele of this locus is associated with a 50% reduction in mean intestinal tumor number. Through in silico analysis and confirmatory sequencing, we have identified the Rad50-interacting protein-1 gene as a strong candidate for Mom5.

Disruption of estrogen receptor signaling enhances intestinal neoplasia in Apc(Min/+) mice

Estrogen receptors (ERs) [ERalpha (Esr1) and ERbeta (Esr2)] are expressed in the human colon, but during the multistep process of colorectal carcinogenesis, expression of both ERalpha and ERbeta is lost, suggesting that loss of ER function might promote colorectal carcinogenesis. Through crosses between an ERalpha knockout and Apc(Min) mouse strains, we demonstrate that ERalpha deficiency is associated with a significant increase in intestinal tumor multiplicity, size and burden in Apc(Min/+) mice. Within the normal intestinal epithelium of Apc(Min/+) mice, ERalpha deficiency is associated with an accumulation of nuclear beta-catenin, an indicator of activation of the Wnt-beta-catenin-signaling pathway, which is known to play a critical role in intestinal cancers. Consistent with the hypothesis that ERalpha deficiency is associated with activation of Wnt-beta-catenin signaling, ERalpha deficiency in the intestinal epithelium of Apc(Min/+) mice also correlated with increased expression of Wnt-beta-catenin target genes. Through crosses between an ERbeta knockout and Apc(Min) mouse strains, we observed some evidence that ERbeta deficiency is associated with an increased incidence of colon tumors in Apc(Min/+) mice. This effect of ERbeta deficiency does not involve modulation of Wnt-beta-catenin signaling. Our studies suggest that ERalpha and ERbeta signaling modulate colorectal carcinogenesis, and ERalpha does so, at least in part, by regulating the activity of the Wnt-beta-catenin pathway.

Tissue-specific actions of the Ept1, Ept2, Ept6, and Ept9 genetic determinants of responsiveness to estrogens in the female rat

Ept1, Ept2, Ept6, and Ept9 are quantitative trait loci mapped in crosses between the ACI and Copenhagen (COP) rat strains as genetic determinants of responsiveness of the pituitary gland to estrogens. We have developed four congenic rat strains, each of which carries, on the genetic background of the ACI rat strain, alleles from the COP rat strain that span one of these quantitative trait loci. Relative to the female ACI rats, female ACI.COP-Ept1 rats exhibited reduced responsiveness to 17beta-estradiol (E2) in the pituitary gland, as evidenced by quantification of pituitary mass and circulating prolactin, and in the mammary gland, as evidenced by reduced susceptibility to E2-induced mammary cancer. The ACI.COP-Ept2 rat strain exhibited reduced responsiveness to E2 in the pituitary gland but did not differ from the ACI strain in regard to susceptibility to E2-induced mammary cancer. Interestingly, female Ept2 congenic rats exhibited increased responsiveness to E2 in the thymus, as evidenced by enhanced thymic atrophy. The ACI.COP-Ept6 rat strain exhibited increased responsiveness to E2 in the pituitary gland, which was associated with a qualitative phenotype suggestive of enhanced pituitary vascularization. The ACI.COP-Ept9 rat strain exhibited reduced responsiveness to E2 in the anterior pituitary gland, relative to the ACI rat strain. Neither Ept6 nor Ept9 impacted responsiveness to E2 in the mammary gland or thymus. These data indicate that each of these Ept genetic determinants of estrogen action is unique in regard to the tissues in which it exerts its effects and/or the direction of its effect on estrogen responsiveness.

Genetic control of estrogen action in the rat: mapping of QTLs that impact pituitary lactotroph hyperplasia in a BN x ACI intercross

Estrogens are important regulators of growth and development and contribute to the etiology of several types of cancer. Different inbred rat strains exhibit marked, cell-type-specific differences in responsiveness to estrogens as well as differences in susceptibility to estrogen-induced tumorigenesis. Regulation of pituitary lactotroph homeostasis is one estrogen-regulated response that differs dramatically between different inbred rat strains. In this article we demonstrate that the growth response of the anterior pituitary gland of female ACI rats to 17beta-estradiol (E2) markedly exceeds that of identically treated female Brown Norway (BN) rats. We further demonstrate that pituitary mass, a surrogate indicator of absolute lactotroph number, behaves as a quantitative trait in E2-treated F(2) progeny generated in a genetic cross originating with BN females and ACI males. Composite interval mapping analyses of the (BNxACI)F(2) population revealed quantitative trait loci (QTLs) that exert significant effects on E2-induced pituitary growth on rat chromosome 4 (RNO4) (Ept5) and RNO7 (Ept7). Continuous treatment with E2 rapidly induces mammary cancer in female ACI rats but not BN rats, and QTLs that impact susceptibility to E2-induced mammary cancer in the (BNxACI)F(2) population described here have been mapped to RNO3 (Emca5), RNO4 (Emca6), RNO5 (Emca8), RNO6 (Emca7), and RNO7 (Emca4). Ept5 and Emca6 map to distinct regions of RNO4. However, Ept7 and Emca4 map to the same region of RNO7. No correlation between pituitary mass and mammary cancer number at necropsy was observed within the (BNxACI)F(2) population. This observation, together with the QTL mapping data, indicate that with the exception of the Ept7/Emca4 locus on RNO7, the genetic determinants of E2-induced pituitary growth differ from the genetic determinants of susceptibility to E2-induced mammary cancer.

Genetic bases of estrogen-induced tumorigenesis in the rat: mapping of loci controlling susceptibility to mammary cancer in a Brown Norway x ACI intercross

Exposure to estrogens is associated with an increased risk of breast cancer. Our laboratory has shown that the ACI rat is uniquely susceptible to 17beta-estradiol (E2)-induced mammary cancer. We previously mapped two loci, Emca1 and Emca2 (estrogen-induced mammary cancer), that act independently to determine susceptibility to E2-induced mammary cancer in crosses between the susceptible ACI rat strain and the genetically related, but resistant, Copenhagen (COP) rat strain. In this study, we evaluate susceptibility to E2-induced mammary cancer in a cross between the ACI strain and the unrelated Brown Norway (BN) rat strain. Whereas nearly 100% of the ACI rats developed mammary cancer when treated continuously with E2, BN rats did not develop palpable mammary cancer during the 196-day course of E2 treatment. Susceptibility to E2-induced mammary cancer segregated as a dominant or incompletely dominant trait in a cross between BN females and ACI males. In a population of 251 female (BN x ACI)F(2) rats, we observed evidence for a total of five genetic determinants of susceptibility. Two loci, Emca4 and Emca5, were identified when mammary cancer status at sacrifice was evaluated as the phenotype, and three additional loci, Emca6, Emca7, and Emca8, were identified when mammary cancer number was evaluated as the phenotype. A total of three genetic interactions were identified. These data indicate that susceptibility to E2-induced mammary cancer in the BN x ACI cross behaves as a complex trait controlled by at least five loci and multiple gene-gene interactions.

Genetic mapping of loci controlling diethylstilbestrol-induced thymic atrophy in the Brown Norway rat

Chronic estrogen administration can lead to thymic atrophy in rodents. In this article we report that the Brown Norway (BN) rat is sensitive to thymic atrophy induced by the estrogen diethylstilbestrol (DES). By contrast, DES does not induce significant thymic atrophy in the August x Copenhagen-Irish (ACI) strain. The sensitivity of the BN rat to DES-induced thymic atrophy appears to segregate as an incompletely dominant trait in crosses between the BN and ACI strains. In a (BN x ACI)F(2) population, we find strong evidence for three major genetic determinants of sensitivity to DES-induced thymic atrophy on rat Chromosome (RNO) 10 and RNO2. Genotypes at these loci, termed Esta1, 2, and 3, do not have a significant impact on the ability of DES to induce pituitary tumorigenesis or inhibit growth of these F(2) rats. These data indicate that the genetic factors that control DES-induced thymic atrophy are distinct from those that control the effects of DES on pituitary mass and body mass. The Esta intervals on RNO10 and RNO2 overlap with loci that control sensitivity to radiation-induced thymocyte apoptosis, as well as susceptibility to a variety of allergic and autoimmune pathologies, including allergic encephalitis, arthritis, and glomerulonephritis in rodents. These observations suggest that common genetic determinants may control sensitivity to estrogen-induced thymic atrophy, maintenance of thymocyte homeostasis, and immune function.

Genetic bases of renal agenesis in the ACI rat: mapping of Renag1 to chromosome 14

Unilateral renal agenesis (URA) is a common developmental defect in humans, occurring at a frequency of approximately 1 in 500-1,000 births. Several genetic syndromes include bilateral or unilateral renal agenesis as an associated phenotype. However, URA frequently occurs in individuals not afflicted by these syndromes and is often asymptomatic. Although it is clear that genetic factors contribute to the etiology of URA, the genetic bases of URA are poorly defined at this time. ACI rats, both males and females, exhibit URA at an incidence of 5%-15%. In this article we characterize the incidence of URA in female and male F(1), F(2), and backcross (BC) progeny from reciprocal genetic crosses between the ACI strain and the unaffected Brown Norway (BN) strain. Through interval mapping analyses of 353 phenotypically defined female F(2) progeny, we mapped to rat Chromosome 14 (RNO14) a genetic locus, designated Renag1 (Renal agenesis 1), that serves as the major determinant of URA in these crosses. Further genotypic analyses of URA-affected female and male F(2) and BC progeny localized Renag1 to a 14.4-Mb interval on RNO14 bounded by markers D14Rat50 and D14Rat12. The data from these genetic studies suggest that the ACI allele of Renag1 acts in an incompletely dominant and incompletely penetrant manner to confer URA.

Genetic mapping of Eutr1, a locus controlling E2-induced pyometritis in the Brown Norway rat, to RNO5

In certain rat strains, chronic estrogen administration can lead to pyometritis, an inflammation of the uterus accompanied by infection and the accumulation of intraluminal pus. In this article, we report that the Brown Norway (BN) rat is highly susceptible to pyometritis induced by 17beta-estradiol (E2). The susceptibility of the BN rat to E2-induced pyometritis appears to segregate as a recessive trait in crosses to the resistant August x Copenhagen Irish (ACI) strain. In a (BN x ACI)F(2) population, we find strong evidence for a major genetic determinant of susceptibility to E2-induced pyometritis on rat chromosome 5 (RNO5). Our data are most consistent with a model in which the BN allele of this locus, designated Eutr1 (Estrogen-induced uterine response 1), acts in an incompletely dominant manner to control E2-induced pyometritis. Furthermore, we have confirmed the contribution of Eutr1 to E2-induced uterine pyometritis using an RNO5 congenic rat strain. In addition to Eutr1, we obtained evidence suggestive of linkage for five additional loci on RNO2, 4, 11, 17, and X that control susceptibility to E2-induced pyometritis in the (BN x ACI)F(2) population.

Localization of Eutr2, a locus controlling susceptibility to DES-induced uterine inflammation and pyometritis, to RNO5 using a congenic rat strain

In some rat strains chronic administration of exogenous estrogens induces pyometritis, an inflammation of the uterus associated with infection, suggesting that there is genetic variation in susceptibility to estrogen-induced inflammation and pyometritis. In this article we report that following 10 weeks of treatment with the synthetic estrogen diethylstilbestrol (DES), Fisher 344 (F344) rats exhibit modest uterine inflammation and a 0% incidence of pyometritis. By contrast, under identical experimental conditions, Brown Norway (BN) rats exhibit significant inflammation and a 100% incidence of pyometritis. Similarly, we also observed profound uterine inflammation and a 100% incidence of pyometritis in a congenic rat strain in which a segment of RNO5 from the BN strain is carried on the F344 strain. These data suggest that a locus on RNO5 controls both the magnitude of DES-induced uterine inflammation and susceptibility to DES-induced pyometritis. This locus, designated Eutr2, resides within the same segment of RNO5 as the Eutr1 locus, which confers susceptibility to E2-induced pyometritis in an F2 population generated in a cross between the BN and August x Copenhagen 9935, Irish (ACI) strains.

Genetic determination of susceptibility to estrogen-induced mammary cancer in the ACI rat: mapping of Emca1 and Emca2 to chromosomes 5 and 18

Hormonal, genetic, and environmental factors play major roles in the complex etiology of breast cancer. When treated continuously with 17beta-estradiol (E2), the ACI rat exhibits a genetically conferred propensity to develop mammary cancer. The susceptibility of the ACI rat to E2-induced mammary cancer appears to segregate as an incompletely dominant trait in crosses to the resistant Copenhagen (COP) strain. In both (ACI x COP)F(2) and (COP x ACI)F(2) populations, we find strong evidence for a major genetic determinant of susceptibility to E2-induced mammary cancer on distal rat chromosome 5. Our data are most consistent with a model in which the ACI allele of this locus, termed Emca1 (estrogen-induced mammary cancer 1), acts in an incompletely dominant manner to increase both tumor incidence and tumor multiplicity as well as to reduce tumor latency in these populations. We also find evidence suggestive of a second locus, Emca2, on chromosome 18 in the (ACI x COP)F(2) population. The ACI allele of Emca2 acts in a dominant manner to increase incidence and decrease latency. Together, Emca1 and Emca2 act independently to modify susceptibility to E2-induced mammary cancer.

Genetic bases of estrogen-induced pituitary tumorigenesis: identification of genetic loci determining estrogen-induced pituitary growth in reciprocal crosses between the ACI and Copenhagen rat strains

Estrogens stimulate proliferation and enhance survival of the prolactin (PRL)-producing lactotroph of the anterior pituitary gland and induce development of PRL-producing pituitary tumors in certain inbred rat strains but not others. The goal of this study was to elucidate the genetic bases of estrogen-induced pituitary tumorigenesis in reciprocal intercrosses between the genetically related ACI and Copenhagen (COP) rat strains. Following 12 weeks of treatment with the synthetic estrogen diethylstilbestrol (DES), pituitary mass, an accurate surrogate marker of absolute lactotroph number, was increased 10.6-fold in ACI rats and 4.5-fold in COP rats. Composite interval mapping analyses of the phenotypically defined F(2) progeny from the reciprocal crosses identified six quantitative trait loci (QTL) that determine the pituitary growth response to DES. These loci reside on chromosome 6 [Estrogen-induced pituitary tumor (Ept)1], chromosome 3 (Ept2 and Ept6), chromosome 10 (Ept9), and chromosome 1 (Ept10 and Ept13). Together, these six Ept loci and one additional suggestive locus on chromosome 4 account for an estimated 40% of the phenotypic variance exhibited by the combined F(2) population, while 34% of the phenotypic variance was estimated to result from environmental factors. These data indicate that DES-induced pituitary mass behaves as a quantitative trait and provide information that will facilitate identification of genes that determine the tumorigenic response of the pituitary gland to estrogens.

Estrogen receptor alpha-mediated events promote sex-specific diabetic glomerular hypertrophy

Sex differences in the incidence and progression of renal diseases suggest a protective role for estrogen. This study examined the role of estrogen receptor alpha (ERalpha)-mediated events in normal and diabetic renal and glomerular growth. Wild-type and ERalpha-null mice (ERKO) were observed over 2 wk of streptozocin-induced diabetes. Blood glucose was monitored, and insulin was given daily to maintain levels of 250-350 mg/dl. Body weight, kidney weight, glucose, insulin, renal transforming growth factor-beta(1), and glomerular area were examined for effects of sex, genotype, and diabetes. Genotype had no effect on glomerular or renal size in male mice regardless of metabolic state. Nondiabetic female ERKO mice had kidney weights approaching those of wild-type males and much greater than those of wild-type females (0.15 +/- 0.04 vs. 0.11 +/- 0.04 g; P < 0.001). When only diabetic mice were studied, sex and/or genotype showed no effect on renal weight. Diabetic female ERKO mice had smaller glomerular areas than wild types (2,799 +/- 159 vs. 3,409 +/- 187 microm(2); P = 0.01). Glomerular areas were similar in diabetic wild-type and ERKO males (3,020 +/- 199 vs. 3,406 +/- 176 microm(2)). Transforming growth factor-beta(1) levels, expressed as picograms per milligram total protein, were similar in diabetic wild-type and ERKO males (1.0 +/- 0.6 vs. 0.9 +/- 0.6). In diabetic females, wild types had significantly higher levels of this growth factor than ERKO mice (3.8 +/- 0.7 vs. 1.1 +/- 0.6; P = 0.005). ERalpha-mediated processes influence normal and diabetic renal and glomerular size, but only in female mice. These data do not support a protective role for ERalpha-mediated events in diabetic nephropathy.

Rat strain specific attenuation of estrogen action in the anterior pituitary gland by dietary energy restriction

The purpose of this study was to compare the effects of a 40% restriction of dietary energy consumption, relative to that consumed by rats allowed to feed ad libitum, on the ability of 17beta-estradiol (E2) to induce pituitary tumorigenesis in two inbred rat strains, ACI and Copenhagen (COP), which are very closely related genetically. Ovary-intact ACI and COP rats were fed either a control or an energy-restricted diet beginning at 8 wk of age. Continuous treatment with E2, released from subcutaneous Silastic tubing implants, was initiated at 9 wk of age and the animals were killed 12 wk later. Estrogen-induced pituitary tumorigenesis is associated with rapid induction of lactotroph hyperplasia, increased pituitary mass, and hyperprolactinemia. E2 significantly increased pituitary mass and circulating prolactin (PRL) in both ACI and COP rats, and this response was significantly greater in ACI rats relative to COP. Dietary energy restriction did not inhibit E2-induced pituitary growth in the ACI rat. By contrast, E2-induced pituitary growth in COP rats was attenuated by dietary energy restriction, as evidenced by quantification of pituitary mass, pituitary weight to body weight ratio, circulating PRL, and pituitary cell proliferation. This study indicates that sensitivity to the inhibitory actions of dietary energy restriction on E2-induced pituitary tumorigenesis is genetically determined.

DES action in the thymus: inhibition of cell proliferation and genetic variation

Many tissues, including the thymus, represent direct targets of estrogen action. In contrast to many estrogen responsive tissues, the thymus undergoes a profound atrophy in response to elevated levels of estrogens. The mechanism of estrogen-induced atrophy in the thymus is unknown; however, it appears not to involve massive thymocyte apoptosis. Here, we demonstrate that the estrogen diethylstilbestrol (DES) inhibits cell proliferation within the thymic cortex, the primary site of thymocyte proliferation. Unlike glucocorticoid action, the effect of DES on thymocyte proliferation does not appear to be mediated by direct down regulation of cyclin D3. We also demonstrate for the first time that rat strains vary in their sensitivity to DES-induced thymic atrophy. This sensitivity correlates with the ability of DES to inhibit cell proliferation in the thymus. These data suggest that genetic factors may regulate estrogen action within this tissue by affecting estrogen responsive pathways that control cell proliferation.

The Mom1AKR intestinal tumor resistance region consists of Pla2g2a and a locus distal to D4Mit64

The Mom1 (Modifier of Min-1) region of distal chromosome 4 was identified during a screen for polymorphic modifiers of intestinal tumorigenesis in ApcMin/+ mice. Here, we demonstrate that the Mom1AKR allele consists of two genetic components. These include the secretory phospholipase Pla2g2a, whose candidacy as a Mom1 resistance modifier has now been tested with several transgenic lines. A second region, distal to Pla2g2a, has also been identified using fine structure recombinants. Pla2g2aAKR transgenic mice demonstrate a modest resistance to tumorigenesis in the small intestine and a very robust resistance in the large intestine. Moreover, the tumor resistance in the colon of Pla2g2aAKR animals is dosage-dependent, a finding that is consistent with our observation that Pla2g2a is expressed in goblet cells. By contrast, mice carrying the distal Mom1 modifier demonstrate a modest tumor resistance that is confined to the small intestine. Thus, the phenotypes of these two modifier loci are complementary, both in their quantitative and regional effects. The additive effects and tight linkage of these modifiers may have been necessary for the initial identification of the Mom1 region.

A monofunctional derivative of melphalan: preparation, DNA alkylation products, and determination of the specificity of monoclonal antibodies that recognize melphalan-DNA adducts

Bifunctional alkylating agents, such as those based on nitrogen mustard, form important parts of many anti-cancer chemotherapy protocols and are responsible for increased incidences of secondary tumors in successfully treated patients. These drugs generally form a majority of monofunctional DNA adducts, although the bifunctional adducts appear to be necessary for their powerful cytotoxic and antitumor effects. The relative importance of bifunctional as opposed to monofunctional adducts in the varied biological consequences of drug exposure has not been studied in detail, particularly in relation to the role and specificity of biochemical responses to therapy-related DNA damage. A simple method is described for the preparation of useful quantities of a pure monofunctional derivative of the nitrogen mustard-based drug melphalan. Monohydroxymelphalan was prepared by partial hydrolysis, purified by reversed phase chromatography, and characterized by MS, NMR, and HPLC. Contamination with melphalan was </=0.2%. The heat labile DNA base adducts formed by monohydroxymelphalan were shown to contain undetectable levels of cross-linked species. The ratio of adenine to guanine adducts was 0.62, similar to the equivalent ratio for melphalan. The sequence-dependent pattern of alkylation of purified DNA was indistinguishable from that of melphalan, but required a higher dose to achieve comparable extents of reaction. The specificities of two monoclonal antibodies that recognize melphalan-DNA adducts were investigated using DNA alkylated with [3H]monohydroxymelphalan. Adducts on this DNA showed similar immunoreactivities to adducts formed by melphalan. This shows clearly that neither antibody was specific for cross-linked adducts and that it is therefore possible to quantify adducts formed by both monohydroxymelphalan and melphalan with high sensitivities. The availability of monohydroxymelphalan in addition to melphalan, together with sensitive immunoassays for adducts on extracted DNA and in individual cells, constitutes a useful system for investigating cellular responses to the DNA modifications formed by a clinically relevant drug.

The impact of National Cancer Institute training on clinical tobacco use cessation services by oral health teams

The authors surveyed participants in a National Cancer Institute, or NCI, training program that provides brief tobacco cessation services. They found significant improvements in the frequency with which practitioners ask patients about tobacco use and assist patients in stopping tobacco use. Improvements also were found in the participants' level of confidence and preparedness to help patients quit. Despite some limitations, the NCI training was shown to be an effective program for the oral health care team.

Analysis of the Mom1 modifier of intestinal neoplasia in mice

Although the methodology for mapping genes controlling susceptibility to tumor development in mice is becoming well established, it remains a formidable challenge to move from linkage to locus. Positional cloning, now commonly used in the identification of loci affecting a qualitative phenotype, has yet to be successfully applied to quantitative trait loci. This study describes the application of candidate gene testing, a method complementary to positional cloning. The method has been applied to evaluate candidates for the quantitative trait locus, Mom1, which modifies the susceptibility of ApcMin/+ mice to spontaneous intestinal tumor development. The authors also discuss the further testing of one candidate, the phospholipase gene Pla2g2a, by transgenesis. Finally, studies on the mode of action of Mom1 are discussed in light of the evidence that Mom1 encodes this secretory phospholipase.

The intestinal epithelium and its neoplasms: genetic, cellular and tissue interactions

The Min (multiple intestinal neoplasia) strain of the laboratory mouse and its derivatives permit the fundamental study of factors that regulate the transition between normal and neoplastic growth. A gene of central importance in mediating these alternative patterns of growth is Apc, the mouse homologue of the human adenomatous polyposis coli (APC) gene. When adenomas form in the Min mouse, both copies of the Apc gene must be inactivated. One copy is mutated by the nonsense Apc allele carried in heterozygous form in this strain. The other copy can be silenced by any of several mechanisms. These range from loss of the homologue bearing the wild-type Apc allele; to interstitial deletions surrounding the wild-type allele; to intragenic mutation, including nonsense alleles; and finally, to a reduction in expression of the locus, perhaps owing to mutation in a regulatory locus. Each of these proposed mechanisms may constitute a two-hit genetic process as initially posited by Knudson; however, apparently the two hits could involve either a single locus or two loci. The kinetic order for the transition to adenoma may be still higher than two, if polyclonal adenomas require stronger interactions than passive fusion. The severity of the intestinal neoplastic phenotype of the Min mouse is strongly dependent upon loci other than Apc. One of these, Mom1, has now been rigorously identified at the molecular level as encoding an active resistance conferred by a secretory phospholipase. Mom1 acts locally within a crypt lineage, not systemically. Within the crypt lineage, however, its action seems to be non-autonomous: when tumours arise in Mom1 heterozygotes, the active resistance allele is maintained in the tumour (MOH or maintenance of heterozygosity). Indeed, the secretory phospholipase is synthesized by post-mitotic Paneth cells, not by the proliferative cells that presumably generate the tumour. An analysis of autonomy of modifier gene action in chimeric mice deserves detailed attention both to the number of genetic factors for which an animal is chimeric and to the clonal structure of the tissue in question. Beyond Mom1, other loci can strongly modify the severity of the Min phenotype. An emergent challenge is to find ways to identify the full set of genes that interact with the intestinal cancer predisposition of the Min mouse strain. With such a set, one can then work, using contemporary mouse genetics, to identify the molecular, cellular and organismal strategies that integrate their functions. Finally, with appropriately phenotyped human families, one can investigate by a candidate approach which modifying factors influence the epidemiology of human colon cancer. Even if a candidate modifier does not explain any of the genetic epidemiology of colon cancer in human populations, modifier activities discovered by mouse genetics provide candidates for chemopreventive and/or therapeutic modalities in the human.

Polyclonal structure of intestinal adenomas in ApcMin/+ mice with concomitant loss of Apc+ from all tumor lineages

When tumors form in intestinal epithelia, it is important to know whether they involve single initiated somatic clones. Advanced carcinomas in humans and mice are known to be monoclonal. However, earlier stages of tumorigenesis may instead involve an interaction between cells that belong to separate somatic clones within the epithelium. The clonality of early tumors has been investigated in mice with an inherited predisposition to intestinal tumors. Analysis of Min (multiple intestinal neoplasia) mice chimeric for a ubiquitously expressed cell lineage marker revealed that normal intestinal crypts are monoclonal, but intestinal adenomas frequently have a polyclonal structure, presenting even when very small as single, focal adenomas composed of at least two somatic lineages. Furthermore, within these polyclonal adenomas, all tumor lineages frequently lose the wild-type Apc allele. These observations can be interpreted by several models for clonal interaction within the epithelium, ranging from passive fusion within regions of high neoplastic potential to a requirement for active clonal cooperation.

Localized gene action controlling intestinal neoplasia in mice

Mice heterozygous for the ApcMin (Min) mutation develop adenomas throughout the intestinal tract. Apc is believed to be involved in cell migration, adhesion, and polarity. Adenoma multiplicity and growth rate are modulated by an unlinked modifier locus, Mom1. The secretory phospholipase Pla2g2a is a candidate for Mom1. Here, we investigate the range of action of Apc and Mom1. Analysis of chimeric Min mice indicates that the actions of both Apc and Mom1 are localized within the cell lineage that gives rise to intestinal tumors.

Intestinal neoplasia in the ApcMin mouse: independence from the microbial and natural killer (beige locus) status

We have tested the hypothesis that enteric bacteria are necessary for formation of intestinal adenomas in C57BL/6-ApcMin/+ mouse. Germ-free mice developed 2-fold fewer adenomas than conventional controls in the medial small intestine (7.3 versus 14.9; P < 0.003), but there were no significant differences in the rest of the intestinal tract. We conclude that microbial status does not strongly alter the adenoma phenotype in this mouse model of familial adenomatous polyposis. In parallel, we have found that C57BL/6-ApcMin/+ mice mutated at the beige locus, which controls natural killer activity, are also unaltered in adenoma multiplicity.

Genetic evaluation of candidate genes for the Mom1 modifier of intestinal neoplasia in mice

As genetic mapping of quantitative trait loci (QTL) becomes routine, the challenge is to identify the underlying genes. This paper develops rigorous genetic tests for evaluation of candidate genes for a QTL, involving determination of allelic status in inbred strains and fine-structure genetic mapping. For the Mom1 modifier of intestinal adenomas caused by ApcMin, these tests are used to evaluate two candidate genes: Pla2g2a, a secretory phospholipase, and Rap1GAP, a GTPase activating protein. Rap1GAP passes the first test but is excluded by a single fine-structure recombinant. Pla2g2a passes both tests and is a strong candidate for Mom1. Significantly, we also find that ApcMin-induced adenomas remain heterozygous for the Mom1 region, consistent with Mom1 acting outside the tumor lineage and encoding a secreted product.

Current intra-aortic balloon pump practice issues. Survey results

Patient care delivery has changed or has at least begun to change throughout institutions nationwide. Those who once regarded theory as a formulation for patient outcome have rendered it inefficient; as the practice of balloon pumping has expanded, many important questions have been raised surrounding the basis for procedures involving IABP. Nursing guidelines for correct IABP procedures are theoretically based procedures. Although it is influential, theory-based practice has proven to be an inefficient means for formulating current practice standards. The Ahern Gould and Stark Current Practice Survey exemplifies the uncertainties that surround the practice of IABP. The nationwide search for scientifically based IABP methods is realized as those surveyed present numerous questions, giving rise to clinical research directions for IABP practitioners.

Mom1 is a semi-dominant modifier of intestinal adenoma size and multiplicity in Min/+ mice

The intestinal tumor multiplicity in mice heterozygous for ApcMin is strongly modulated by genetic background. On the sensitive C57BL/6J (B6) background, mice develop large numbers of intestinal adenomas. The AKR/J (AKR) strain carries alleles that correlate with a strong reduction in tumor multiplicity. To study the effect of one of these modifiers, Mom1, we have generated a mouse line in which the AKR allele of Mom1 is carried on the sensitive B6 genetic background. This strain was produced by using a marker-assisted selection method to eliminate unlinked AKR alleles more rapidly. The application and efficiency of this method are discussed. We used this strain to determine that Mom1 affects both tumor multiplicity and tumor size in a semi-dominant fashion.

Action of Min and Mom1 on neoplasia in ectopic intestinal grafts

Mice heterozygous for Min, a mutant allele of Apc, develop adenomas throughout the intestinal tract. Tumor multiplicity in Min mice is influenced by genetic modifier loci. Previously, we mapped one of these modifier loci, Mom1, to distal mouse chromosome 4. Mom1 is a semidominant modifier of both tumor size and multiplicity in Min mice. Recent evidence suggests that Mom1 may encode a secretory phospholipase, Pla2g2a. Pla2g2a is expressed in a variety of cell types and seems to be involved in inflammatory responses and bacterial defense mechanisms. Here, we determine whether Min and Mom1 act in a tissue-autonomous fashion using ectopic intestinal isografts. Within the small intestinal grafts, both Min and Mom1 act in a tissue-autonomous manner. There is no evidence that either Min or Mom1 has a systemic effect on tumor development. However, within the colonic grafts, the Min phenotype does not appear to be autonomous; the development of colonic tumors in Min mice seems dependent on factors beyond the Min genotype of the colonic epithelium. Micro-environmental factors, such as digestive secretions, dietary components, or intestinal flora, may be critical factors contributing to the development of Min-induced colonic tumors. However, these factors are not required for the action of Min or Mom1 within the small intestine.

Manipulation of the mouse germline in the study of Min-induced neoplasia

The Min mouse, generated by random germline mutagenesis, carries a mutation in the mouse homolog of APC and is a model of inherited human intestinal tumorigenesis. To identify other genes in the pathway(s) of intestinal tumorigenesis, genes that modify the Min phenotype have been sought. Several have been identified, including Mom1 and the genes for the 5-cytosine DNA methyltransferase and the DNA mismatch repair factor Msh2. Min-dependent tumorigenesis also occurs in mammary glands, the pancreas, and the body wall. The Min mouse has therefore become a model for tumorigenesis in a variety of organs. Identifying modifiers of its phenotype will help in piecing together the pathways of tumorigenesis in each of these tissues.

Paradoxical effect of thalidomide prophylaxis on chronic graft-vs.-host disease

Thalidomide has been reported to be an effective agent for the treatment of chronic graft-vs.-host disease (GVHD). To determine its efficacy as a prophylactic agent for the prevention of chronic GVHD, a prospective randomized double-blind study was performed. A total of 59 patients were randomized to receive either placebo or thalidomide (200 mg orally twice a day) beginning 80 days after allogeneic bone marrow transplantation (BMT). Fifty-four evaluable patients were analyzed, 26 received placebo, and 28 received thalidomide. The characteristics of patients were well-balanced between the two groups. Following the first interim analysis conducted by the Data Safety Monitoring Board using an intent-to-treat approach, a statistically significant difference in the incidence of chronic GVHD was found. Patients receiving thalidomide developed chronic GVHD more often than patients receiving placebo (p = 0.06). Moreover, an apparent overall survival advantage was noted for patients receiving placebo compared to those receiving thalidomide (p = 0.006). Adjustment for possible confounding factors did not eliminate these negative effects of thalidomide. These results demonstrate that while thalidomide is an effective agent for the therapy of chronic GVHD, its use at the doses administered for the prophylaxis of chronic GVHD resulted in a paradoxical outcome with a higher incidence of chronic GVHD and a lower overall survival. We conclude that the early use of thalidomide results in a shift in the balance between GVHD and induction of tolerance. These data demonstrate again the importance of phase III double-blind controlled randomized studies.

Homozygosity for the Min allele of Apc results in disruption of mouse development prior to gastrulation

Mutation of the APC (adenomatous polyposis coli) gene is an early event in colon tumor development in humans. Mice carrying Min (multiple intestinal neoplasia), a mutant allele of Apc, develop intestinal and mammary tumors as adults. To study the role of the Apc gene in development, we have investigated the phenotype of embryos homozygous for ApcMin (Min). Development of the primitive ectoderm fails prior to gastrulation in homozygous Min embryos. By midgestation, the presumed homozygotes consist of a mass of trophoblast giant cells with an additional cluster of much smaller embryonic cells. These results indicate that functional Apc is required for normal growth of inner cell mass derivatives.

ApcMin: a mouse model for intestinal and mammary tumorigenesis

Min (multiple intestinal neoplasia) is a mutant allele of the murine Apc (adenomatous polyposis coli) locus, encoding a nonsense mutation at codon 850. Like humans with germline mutations in APC, Min/+ mice are predisposed to intestinal adenoma formation. The number of adenomas is influenced by modifier loci carried by different inbred strains. One modifier locus, Mom-1 (modifier of Min-1), maps to distal chromosome 4. Intestinal tumours from both B6 (C57BL/6J) and hybrid Min/+ mice show extensive loss of the wild-type allele at Apc. B6 Min/+ female mice are predisposed to spontaneous mammary tumours. The incidence of both intestinal and mammary tumours can be increased in an age-specific manner by treatment with ethylnitrosourea (ENU). Min mice provide a good animal model for studying the role of Apc and interacting genes in the initiation and progression of intestinal and mammary tumorigenesis.