Loss of BMAL1 in ovarian steroidogenic cells results in implantation failure in female mice.

The circadian clock plays a significant role in many aspects of female reproductive biology, including estrous cycling, ovulation, embryonic implantation, onset of puberty, and parturition. In an effort to link cell-specific circadian clocks to their specific roles in female reproduction, we used the promoter that controls expression of Steroidogenic Factor-1 (SF1) to drive Cre-recombinase-mediated deletion of the brain muscle arnt-like 1 (Bmal1) gene, known to encode an essential component of the circadian clock (SF1-Bmal1(-/-)). The resultant SF1-Bmal1(-/-) females display embryonic implantation failure, which is rescued by progesterone supplementation, or bilateral or unilateral transplantation of wild-type ovaries into SF1-Bmal1(-/-) dams. The observation that the central clock, and many other peripheral clocks, are fully functional in this model allows the assignment of the implantation phenotype to the clock in ovarian steroidogenic cells and distinguishes it from more general circadian related systemic pathology (e.g., early onset arthropathy, premature aging, ovulation, late onset of puberty, and abnormal estrous cycle). Our ovarian transcriptome analysis reveals that deletion of ovarian Bmal1 disrupts expression of transcripts associated with the circadian machinery and also genes critical for regulation of progesterone production, such as steroidogenic acute regulatory factor (Star). Overall, these data provide a powerful model to probe the interlocking and synergistic network of the circadian clock and reproductive systems.

Genetic background determines if Stat5b suppresses or enhances murine hepatocarcinogenesis.

Murine hepatocarcinogenesis requires growth hormone (GH). To determine if the GH-responsive transcription factor STAT5b (signal transducer and activator of transcription 5b) is also required, we compared the hepatic gene expression profiles of global Stat5b null mice to cancer-resistant mice mutant in the GH pathway-GH-deficient little and androgen receptor-null Tfm males. We found a high degree of overlap among Tfm, little, and Stat5b null males. The liver cancer susceptibility of global Stat5b null mice was assessed on three distinct genetic backgrounds: BALB/cJ (BALB), C57BL/6J (B6), and C3H/HeJ (C3H). The effect of Stat5b on hepatocarcinogenesis depended on the genetic background. B6 Stat5b null congenic males and females developed 2.4 times as many tumors as wild-type (WT) controls (P < 0.002) and the tumors were larger (P < 0.003). In BALB/c congenics, loss of STAT5b had no effect on either sex. C3H Stat5b null congenic males and females were resistant to liver cancer, developing 2.7- and 6-fold fewer tumors, respectively (P < 0.02, 0.01). These results provide the first example of a single gene behaving as both oncogene and tumor suppressor in a given tissue, depending only on the endogenous modifier alleles carried by different genetic backgrounds.

Supplementation by vitamin D compounds does not affect colonic tumor development in vitamin D sufficient murine models.

Epidemiological studies indicate that sunlight exposure and vitamin D are each associated with a lower risk of colon cancer. The few controlled supplementation trials testing vitamin D in humans reported to date show conflicting results. We have used two genetic models of familial colon cancer, the Apc(Pirc/+) (Pirc) rat and the Apc(Min/+) (Min) mouse, to investigate the effect of 25-hydroxyvitamin D(3) [25(OH)D(3)] and two analogs of vitamin D hormone on colonic tumors. Longitudinal endoscopic monitoring allowed us to test the efficacy of these compounds in preventing newly arising colonic tumors and in affecting established colonic tumors. 25(OH)D(3) and two analogs of vitamin D hormone each failed to reduce tumor multiplicities or alter the growth patterns of colonic tumors in the Pirc rat or the Min mouse.

Estrogen Receptor-α Suppresses Liver Carcinogenesis and Establishes Sex-Specific Gene Expression.

Estrogen protects females from hepatocellular carcinoma (HCC). To determine whether this protection is mediated by classic estrogen receptors, we tested HCC susceptibility in estrogen receptor-deficient mice. In contrast to a previous study, we found that diethylnitrosamine induces hepatocarcinogenesis to a significantly greater extent when females lack Esr1, which encodes Estrogen Receptor-α. Relative to wild-type littermates, Esr1 knockout females developed 9-fold more tumors. Deficiency of Esr2, which encodes Estrogen Receptor-ß, did not affect liver carcinogenesis in females. Using microarrays and QPCR to examine estrogen receptor effects on hepatic gene expression patterns, we found that germline Esr1 deficiency resulted in the masculinization of gene expression in the female liver. Six of the most dysregulated genes have previously been implicated in HCC. In contrast, Esr1 deletion specifically in hepatocytes of Esr1 conditional null female mice (in which Cre was expressed from the albumin promoter) resulted in the maintenance of female-specific liver gene expression. Wild-type adult females lacking ovarian estrogen due to ovariectomy, which is known to make females susceptible to HCC, also maintained female-specific expression in the liver of females. These studies indicate that Esr1 mediates liver cancer risk, and its control of sex-specific liver gene expression involves cells other than hepatocytes.

Predominant modifier of extreme liver cancer susceptibility in C57BR/cdJ female mice localized to 6 Mb on chromosome 17.

Sex hormones influence the susceptibility of inbred mice to liver cancer. C57BR/cdJ (BR) females are extremely susceptible to spontaneous and chemically induced liver tumors, in part due to a lack of protection against hepatocarcinogenesis normally offered by ovarian hormones. BR males are also moderately susceptible, and the susceptibility of both sexes of BR mice to liver tumors induced with N,N-diethylnitrosamine relative to the resistant C57BL/6J (B6) strain is caused by two loci designated Hcf1 and Hcf2 (hepatocarcinogenesis in females) located on chromosomes 17 and 1, respectively. The Hcf1 locus on chromosome 17 is the predominant modifier of liver cancer in BR mice. To validate the existence of this locus and investigate its potential interaction with Hcf2, congenic mice for each region were generated. Homozygosity for the B6.BR(D17Mit164-D17Mit2) region resulted in a 4-fold increase in liver tumor multiplicity in females and a 4.5-fold increase in males compared with B6 controls. A series of 16 recombinants covering the entire congenic region was developed to further narrow the area containing Hcf1. Susceptible heterozygous recombinants demonstrated a 3- to 7-fold effect in females and a 1.5- to 2-fold effect in males compared with B6 siblings. The effect in susceptible lines completely recapitulated the susceptibility of heterozygous full-length chromosome 17 congenics and furthermore narrowed the location of the Hcf1 locus to a single region of the chromosome from 30.05 to 35.83 Mb.

Widespread hyperplasia induced by transgenic TGFalpha in ApcMin mice is associated with only regional effects on tumorigenesis.

Using a mouse predisposed to neoplasia by a germ line mutation in Apc (Apc(Min)), we tested whether induced hyperplasia is sufficient to increase intestinal tumor multiplicity or size in the intestine. We found that hyperplasia in the jejunum correlated with a significant increase in tumor multiplicity. However, tumor multiplicity was unchanged in the hyperplastic colon. This result indicates that even an intestine predisposed to neoplasia can, in certain regions including the colon, accommodate net increased cell growth without developing more neoplasms. Where hyperplasia correlated with increased tumor multiplicity, it did not increase the size or net growth of established tumors. This result suggests that the event linking hyperplasia and neoplasia in the jejunum is tumor establishment. Two novel observations arose in our study: the multiple intestinal neoplasia (Min) mutation partially suppressed both mitosis and transforming growth factor alpha-induced hyperplasia throughout the intestine; and zinc treatment alone increased tumor multiplicity in the duodenum of Min mice.

Biologic study of the effects of octreotide-LAR on growth hormone in unresectable and metastatic hepatocellular carcinoma.

BACKGROUND: Animal models suggest that growth hormone participates in hepatocarcinogenesis. OBJECTIVE: To correlate the effect of octreotide long-acting release (LAR) on insulin-like growth factor-I (IGF-I) and -II (IGF-II) with response and survival in patients with unresectable and metastatic hepatocellular carcinoma. METHODS: We conducted a phase II, single-institution trial of octreotide-LAR (30 mg intramuscularly every 4 weeks) in 15 patients while monitoring serum IGF-I and -II levels. RESULTS: Patients (median CLIP score 2, Okuda stage II, and ECOG performance status 1) were treated for a median of 2.0 cycles. No responses occurred. Median overall survival was 116 days (range, 27-937 days) and median progression-free survival was 60 days (range, 27-444 days). One patient had prolonged stable disease (16 months). There were no grade 4 and four grade 3 toxicities: abdominal cramping, elevated creatinine, diarrhea, and dyspnea. Median serum IGF-I decreased from baseline (42.2 ng/mL; range, 14.2-109 ng/mL) to day 29 (27.9 ng/mL; range, 5.7-71.1 ng/mL), and median serum IGF-II decreased from baseline (25,000 ng/mL; range, 12,400-93,600 ng/mL) to day 29 (18,400 ng/mL; range, 4,061-79,400 ng/mL; 2-sided P<.006 and P<.04, respectively; Wilcoxon signed rank test). This suppression did not correlate with clinical activity. Baseline serum IGF-I >30 ng/mL was associated with greater progression-free survival and overall survival (P=.0005 and P=.0173, respectively; 2-sided log-rank test). CONCLUSIONS: Octreotide-LAR lowered serum IGF-I and -II levels; however, this lowering did not correlate with clinical activity. There were no responses, and progression-free survival and overall survival were similar to historical patients not on treatment. Baseline serum IGF-I predicted prognosis.

Interaction networks in yeast define and enumerate the signaling steps of the vertebrate aryl hydrocarbon receptor.

The aryl hydrocarbon receptor (AHR) is a vertebrate protein that mediates the toxic and adaptive responses to dioxins and related environmental pollutants. In an effort to better understand the details of this signal transduction pathway, we employed the yeast S. cerevisiae as a model system. Through the use of arrayed yeast strains harboring ordered deletions of open reading frames, we determined that 54 out of the 4,507 yeast genes examined significantly influence AHR signal transduction. In an effort to describe the relationship between these modifying genes, we constructed a network map based upon their known protein and genetic interactions. Monte Carlo simulations demonstrated that this network represented a description of AHR signaling that was distinct from those generated by random chance. The network map was then explored with a number of computational and experimental annotations. These analyses revealed that the AHR signaling pathway is defined by at least five distinct signaling steps that are regulated by functional modules of interacting modifiers. These modules can be described as mediating receptor folding, nuclear translocation, transcriptional activation, receptor level, and a previously undescribed nuclear step related to the receptor's Per-Arnt-Sim domain.

C57BR/cdJ hepatocarcinogen susceptibility genes act cell-autonomously in C57BR/cdJ<-->C57BL/6J chimeras.

Female C57BR/cdJ (BR) mice are unusually susceptible to spontaneous and chemically induced hepatocarcinogenesis relative to females of other inbred strains, in part because they are insensitive to the inhibitory effects of ovarian hormones on liver tumor development; BR males are intermediate among strains in their sensitivity. C57BL/6J (B6) male and female mice are relatively resistant among inbred strains. Linkage analysis of crosses between BR and resistant B6 mice identified two loci, on Chromosomes 17 and 1, that accounted for the high susceptibility of BR mice to hepatocarcinogenesis. To determine whether the increased susceptibility of BR relative to B6 mice is intrinsic to the target hepatocytes or is the result of local or systemic differences in milieu, we determined the strain of origin of tumors that arose in BR<-->B6 aggregation chimeras. Chimeras were treated at 12 days of age with N,N-diethylnitrosamine, and individual tumors were dissected from 15 males at 32 weeks and from 7 females at 50 weeks of age. DNA was prepared from each tumor, and quantitative PCR assays were used to determine the strain of origin for each tumor. The overall contribution of each strain to non-neoplastic liver was determined using the PCR assay and through analysis of the relative amount of glucose phosphate isomerase activity associated with the BR and B6 electrophoretic variants; the median contribution of B6 cells to non-neoplastic liver was 50%. A majority (91%) of the 230 tumors analyzed from both sexes was derived from the BR donor, indicating that the net overall effect of BR susceptibility genes is cell autonomous.

Association of a Chromosomal Rearrangement Event with Mouse Posterior Polymorphous Corneal Dystrophy and Alterations in Csrp2bp, Dzank1, and Ovol2 Gene Expression.

We have previously described a mouse model of human posterior polymorphous corneal dystrophy (PPCD) and localized the causative mutation to a 6.2 Mbp region of chromosome 2, termed Ppcd1. We now show that the gene rearrangement linked to mouse Ppcd1 is a 3.9 Mbp chromosomal inversion flanked by 81 Kbp and 542 bp deletions. This recombination event leads to deletion of Csrp2bp Exons 8 through 11, Dzank1 Exons 20 and 21, and the pseudogene Znf133. In addition, we identified translocation of novel downstream sequences to positions adjacent to Csrp2bp Exon 7 and Dzank1 Exon 20. Twelve novel fusion transcripts involving Csrp2bp or Dzank1 linked to downstream sequences have been identified. Eight are expressed at detectable levels in PPCD1 but not wildtype eyes. Upregulation of two Csrp2bp fusion transcripts, as well as upregulation of the adjacent gene, Ovol2, was observed. Absence of the PPCD1 phenotype in animals haploinsufficient for Csrp2bp or both Csrp2bp and Dzank1 rules out haploinsufficiency of these genes as a cause of mouse PPCD1. Complementation experiments confirm that PPCD1 embryonic lethality is due to disruption of Csrp2bp expression. The ocular expression pattern of Csrp2bp is consistent with a role for this protein in corneal development and pathogenesis of PPCD1.

DNA Alkylating Agent Protects Against Spontaneous Hepatocellular Carcinoma Regardless of O6-Methylguanine-DNA Methyltransferase Status.

Hepatocellular carcinoma is increasingly important in the United States as the incidence rate rose over the last 30 years. C3HeB/FeJ mice serve as a unique model to study hepatocellular carcinoma tumorigenesis because they mimic human hepatocellular carcinoma with delayed onset, male gender bias, approximately 50% incidence, and susceptibility to tumorigenesis is mediated through multiple genetic loci. Because a human O(6)-methylguanine-DNA methyltransferase (hMGMT) transgene reduces spontaneous tumorigenesis in this model, we hypothesized that hMGMT would also protect from methylation-induced hepatocarcinogenesis. To test this hypothesis, wild-type and hMGMT transgenic C3HeB/FeJ male mice were treated with two monofunctional alkylating agents: diethylnitrosamine (DEN; 0.025 µmol/g body weight) on day 12 of life with evaluation for glucose-6-phosphatase-deficient (G6PD) foci at 16, 24, and 32 weeks or N-methyl-N-nitrosurea (MNU; 25 mg MNU/kg body weight) once monthly for 7 months starting at 3 months of age with evaluation for liver tumors at 12 to 15 months of age. No difference in abundance or size of G6PD foci was measured with DEN treatment. In contrast, it was unexpectedly found that MNU reduces liver tumor prevalence in wild-type and hMGMT transgenic mice despite increased tumor prevalence in other tissues. hMGMT and MNU protections were additive, suggesting that MNU protects through a different mechanism, perhaps through the cytotoxic N7-alkylguanine and N3-alkyladenine lesions which have low mutagenic potential compared with O(6)-alkylguanine lesions. Together, these results suggest that targeting the repair of cytotoxic lesions may be a good preventative for patients at high risk of developing hepatocellular carcinoma.

A potent modifier of liver cancer risk on distal mouse chromosome 1: linkage analysis and characterization of congenic lines.

The C3H/HeJ (C3H) and CBA/J (CBA) mouse strains are classical mouse models of cancer susceptibility, exhibiting high risks for both spontaneous and chemically induced liver cancer. By analysis of backcrosses and intercrosses between C3H or CBA and resistant B6 mice, we have mapped a potent modifier of hepatocellular carcinoma development to distal chromosome 1, linked to the marker D1Mit33 with combined LOD(W) scores of approximately 5.9 (C3H) and 6.5 (CBA). We previously identified this region as one of two that modify susceptibility in the more distantly related C57BR/cdJ (BR) strain. Congenic B6.C3H(D1Mit5-D1Mit17) and B6.BR(D1Mit5-D1Mit17) mice developed significantly more liver tumors than B6 mice did (6- to 13-fold, P < 10(-11), in males; 3- to 4-fold, P < 10(-3), in females). Thus, distal chromosome 1 carries one or more genes that are sufficient to confer susceptibility to liver cancer.

Strategies from UW-Madison for rescuing biomedical research in the US.

A cross-campus, cross-career stage and cross-disciplinary series of discussions at a large public university has produced a series of recommendations for addressing the problems confronting the biomedical research community in the US.

Liver tumor promotion by 2,3,7,8-tetrachlorodibenzo-p-dioxin is dependent on the aryl hydrocarbon receptor and TNF/IL-1 receptors.

We set out to better understand the signal transduction pathways that mediate liver tumor promotion by 2,3,7,8-tetrachlorodibenzo-p-dioxn ("dioxin"). To this end, we first employed congenic mice homozygous for either the Ahr(b1) or Ahr(d) alleles (encoding an aryl hydrocarbon receptor (AHR) with high or low binding affinity for dioxin, respectively) and demonstrated that hepatocellular tumor promotion in response to dioxin segregated with the Ahr locus. Once we had genetic evidence for the importance of AHR signaling, we then asked if tumor promotion by dioxin was influenced by "interleukin-1 (IL-1)-like" inflammatory cytokines. The importance of this question arose from our earlier observation that aspects of the acute hepatocellular toxicity of dioxin are dependent upon IL1-like cytokine signaling. To address this issue, we employed a triple knock-out (TKO) mouse model with null alleles at the loci encoding the three relevant receptors for tumor necrosis factors α and ß and IL-1α and IL-1ß (i.e., null alleles at the Tnfrsf1a, Tnfrsf1b, and Il-1r1 loci). The observation that TKO mice were resistant to the tumor promoting effects of dioxin in liver suggests that inflammatory cytokines play an important step in dioxin mediated liver tumor promotion in the mouse. Collectively, these data support the idea that the mechanism of dioxin acute hepatotoxicity and its activity as a promoter in a mouse two stage liver cancer model may be similar, i.e., tumor promotion by dioxin, like acute hepatotoxicity, are mediated by the linked action of two receptor systems, the AHR and the receptors for the "IL-1-like" cytokines.

Mutations in protein-binding hot-spots on the hub protein Smad3 differentially affect its protein interactions and Smad3-regulated gene expression.

BACKGROUND: Hub proteins are connected through binding interactions to many other proteins. Smad3, a mediator of signal transduction induced by transforming growth factor beta (TGF-ß), serves as a hub protein for over 50 protein-protein interactions. Different cellular responses mediated by Smad3 are the product of cell-type and context dependent Smad3-nucleated protein complexes acting in concert. Our hypothesis is that perturbation of this spectrum of protein complexes by mutation of single protein-binding hot-spots on Smad3 will have distinct consequences on Smad3-mediated responses. METHODOLOGY/PRINCIPAL FINDINGS: We mutated 28 amino acids on the surface of the Smad3 MH2 domain and identified 22 Smad3 variants with reduced binding to subsets of 17 Smad3-binding proteins including Smad4, SARA, Ski, Smurf2 and SIP1. Mutations defective in binding to Smad4, e.g., D408H, or defective in nucleocytoplasmic shuttling, e.g., W406A, were compromised in modulating the expression levels of a Smad3-dependent reporter gene or six endogenous Smad3-responsive genes: Mmp9, IL11, Tnfaip6, Fermt1, Olfm2 and Wnt11. However, the Smad3 mutants Y226A, Y297A, W326A, K341A, and E267A had distinct differences on TGF-ß signaling. For example, K341A and Y226A both reduced the Smad3-mediated activation of the reporter gene by ∼50% but K341A only reduced the TGF-ß inducibilty of Olfm2 in contrast to Y226A which reduced the TGF-ß inducibility of all six endogenous genes as severely as the W406A mutation. E267A had increased protein binding but reduced TGF-ß inducibility because it caused higher basal levels of expression. Y297A had increased TGF-ß inducibility because it caused lower Smad3-induced basal levels of gene expression. CONCLUSIONS/SIGNIFICANCE: Mutations in protein binding hot-spots on Smad3 reduced the binding to different subsets of interacting proteins and caused a range of quantitative changes in the expression of genes induced by Smad3. This approach should be useful for unraveling which Smad3 protein complexes are critical for specific biological responses.

Identification of susceptibility loci in a mouse model of KRASG12D-driven pancreatic cancer.

Genetic background affects susceptibility to pancreatic ductal adenocarcinoma in the Ela-KRAS(G12D) mouse model. In this model, KRAS oncogene expression is driven by an elastase promoter in acinar cells of the pancreas on an FVB/NTac (FVB) background [FVB-Tg(Ela-KRAS(G12D))] with the transgene carried on the Y chromosome. Through linkage analysis of crosses between the C57BL/6J (B6), BALB/cJ (BALB), and DBA/2J (D2) inbred strains of mice and resistant FVB-Tg(Ela-KRAS(G12D)), we have identified six susceptibility loci that affect mean preinvasive lesion multiplicity. Markers on chromosome 2 segregated with high tumor multiplicity in all three strains; these loci were designated Prsq1-3 (pancreatic ras susceptibility quantitative trait loci 1-3; combined F2 and N2 LOD(W), 6.0, 4.1, and 2.7, respectively). Susceptibility loci on chromosome 4, designated Prsq4 and Prsq5, were identified in crosses between FVB transgenic mice and B6 or BALB mice (combined F2 and N2 LOD(W), 3.6 and 2.9, respectively). A marker on chromosome 12 segregated with tumor multiplicity in a BALB × FVB-Tg(Ela-KRAS(G12D)) cross and was designated Prsq6 (LOD(W), ∼2.5). B6-Chr Y(FVB-Tg(Ela-KRASG12D)) and BALB-Chr Y(FVB-Tg(Ela-KRASG12D)) consomics, which carry the KRAS transgene on the FVB Y chromosome on an otherwise inbred B6 or BALB background, developed ∼4-fold (B6) and ∼10-fold (BALB) more lesions than FVB-Tg(Ela-KRAS(G12D)) mice. By 12 months of age, 10% of BALB-Chr Y(FVB-Tg(Ela-KRASG12D)) mice developed invasive carcinomas. Our findings provide evidence that regions of chromosomes 2, 4, and 12 influence the development and progression of pancreatic neoplasms initiated by an oncogenic allele of KRAS in mice.

The PPCD1 mouse: characterization of a mouse model for posterior polymorphous corneal dystrophy and identification of a candidate gene.

The PPCD1 mouse, a spontaneous mutant that arose in our mouse colony, is characterized by an enlarged anterior chamber resulting from metaplasia of the corneal endothelium and blockage of the iridocorneal angle by epithelialized corneal endothelial cells. The presence of stratified multilayered corneal endothelial cells with abnormal patterns of cytokeratin expression are remarkably similar to those observed in human posterior polymorphous corneal dystrophy (PPCD) and the sporadic condition, iridocorneal endothelial syndrome. Affected eyes exhibit epithelialized corneal endothelial cells, with inappropriate cytokeratin expression and proliferation over the iridocorneal angle and posterior cornea. We have termed this the "mouse PPCD1" phenotype and mapped the mouse locus for this phenotype, designated "Ppcd1", to a 6.1 Mbp interval on Chromosome 2, which is syntenic to the human Chromosome 20 PPCD1 interval. Inheritance of the mouse PPCD1 phenotype is autosomal dominant, with complete penetrance on the sensitive DBA/2J background and decreased penetrance on the C57BL/6J background. Comparative genome hybridization has identified a hemizygous 78 Kbp duplication in the mapped interval. The endpoints of the duplication are located in positions that disrupt the genes Csrp2bp and 6330439K17Rik and lead to duplication of the pseudogene LOC100043552. Quantitative reverse transcriptase-PCR indicates that expression levels of Csrp2bp and 6330439K17Rik are decreased in eyes of PPCD1 mice. Based on the observations of decreased gene expression levels, association with ZEB1-related pathways, and the report of corneal opacities in Csrp2bp(tm1a(KOMP)Wtsi) heterozygotes and embryonic lethality in nulls, we postulate that duplication of the 78 Kbp segment leading to haploinsufficiency of Csrp2bp is responsible for the mouse PPCD1 phenotype. Similarly, CSRP2BP haploinsufficiency may lead to human PPCD.