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Simple Summary: The 3Rs principle refers to three concepts: Replacement, Reduction and Refinement. These principles should be taken into consideration during the planning and execution of experiments by trying to replace the animal model with an alternative model (if possible), reduce the number of animals by adopting proper and efficient statistical designs, and refine and improve the experimental conditions. The first application of this principle in Europe was reported in the document of the Council Directive of 24 November 1986 (86/609/EEC), and then developed in the updated Directive 2010/63/EU of the European Parliament and of the Council of 22 September 2010. Here, we discuss the perspectives of the 3Rs principle, with a particular focus on the concept of Reduction. Animal experimentation is a vast ecosystem that tries to make different issues such as legislative, ethical and scientific coexist. Research in animal experimentation has made many strides thanks to the 3Rs principle and the attached legislative decrees, but for this very reason, it needs to be evenly implemented both among the countries that have adhered to the decrees and among the team members who design and execute the experimental practice. In this article, we emphasize the importance of the 3Rs principle's application, with a particular focus on the concept of Reduction and related key aspects that can best be handled with the contribution of experts from different fields. [ABSTRACT FROM AUTHOR]

An immunosuppressive microenvironment in lung concurs to pre-malignant lesions progression to cancer. Here, we explore if perturbing lung microbiota, which contribute to immunosuppression, by antibiotics or probiotic aerosol interferes with lung cancer development in a mouse carcinogen-induced tumor model. Urethane-injected mice were vancomycin/neomycin (V/N)-aerosolized or live or dead L. rhamnosus GG (L.RGG)-aerosolized, and tumor development was evaluated. Transcriptional profiling of lungs and IHC were performed. Tumor nodules number, diameter and area were reduced by live or heat-killed L.RGG, while only a decrease in nodule diameter was observed in V/N-treated lungs. Both L.RGG and V/N reduced Tregs in the lung. In L.RGG-treated groups, the gene encoding the joining chain (J chain) of immunoglobulins was increased, and higher J chain protein and IgA levels were observed. An increased infiltration of B, NK and myeloid-derived cells was predicted by TIMER 2.0. The Kaplan–Meier plotter revealed an association between high levels of J chain mRNA and good prognosis in lung adenocarcinoma patients that correlated with increased B and CD4 T cells and reduced Tregs and M2 macrophages. This study highlights L.RGG aerosol efficacy in impairing lung cancer growth by promoting local immunity and points to this non-invasive strategy to treat individuals at risk of lung cancer. [ABSTRACT FROM AUTHOR]

AIRmax and AIRmin mouse strains phenotypically selected for high and low acute inflammatory responsiveness (AIR) are, respectively, susceptible or resistant to developing hepatocellular carcinoma (HCC) induced by the chemical carcinogens urethane and diethylnitrosamine (DEN). Early production of TNF-α, IL-1β, and IL-6 in the liver after DEN treatment correlated with tumor development in AIRmax mice. Transcriptome analysis of livers from untreated AIRmax and AIRmin mice showed specific gene expression profiles in each line, which might play a role in their differential susceptibility to HCC. Linkage analysis with SNP markers in F2 (AIRmax×AIRmin) intercross mice revealed two quantitative trait loci (QTL) in chromosomes 2 and 9, which are significantly associated with the number and progression of urethane-induced liver tumors. An independent linkage analysis with an intercross population from A/J and C57BL/6J inbred mice mapped regions in chromosomes 1 and 7 associated with the progression of urethane-induced liver tumors, evidencing the heterogeneity of HCC genetic control. [ABSTRACT FROM AUTHOR]

The SM/J mouse strain is resistant to chemically-induced lung tumorigenesis despite having a haplotype, in the pulmonary adenoma susceptibility locus ( Pas1) locus, that confers tumor susceptibility in other strains. To clarify this inconsistent genotype-phenotype correlation, we crossed SM/J mice with another resistant strain and conducted genome-wide linkage analysis in the (C57 BL/6J × SM/J)F2 progeny exposed to urethane to induce lung tumors. Overall, >80% of F2 mice of both sexes developed from 1 to 20 lung tumors. Genotyping of 372 F2 mice for 744 informative non-redundant SNPs dispersed over all autosomal chromosomes revealed four quantitative trait loci ( QTLs) affecting lung tumor multiplicity, on chromosomes 3 (near rs13477379), 15 (rs6285067), 17 (rs33373629) and 18 (rs3706601), all with logarithm of the odds ( LOD) scores >5. Four QTLs modulated total lung tumor volume, on chromosome 3 (rs13477379), 10 (rs13480702), 15 (rs6285067) and 17 (rs3682923), all with LOD scores >4. No QTL modulating lung tumor multiplicity or total volume was detected in Pas1 on chromosome 6. The present study demonstrates that the SM/J strain carries, at the Pas1 locus, the resistance allele: a finding that will facilitate identification of the Pas1 causal element. More generally, it demonstrates that lung tumorigenesis is under complex polygenic control even in a pedigree with low susceptibility to this neoplasia, suggesting that the genetics of lung tumorigenesis is much more complex than evidenced by the pulmonary adenoma susceptibility and resistance loci that have, so far, been mapped in a small number of crosses between a few inbred strains. [ABSTRACT FROM AUTHOR]

Melanoma is a highly heterogeneous tumor for which recent evidence supports a model of dynamic stemness. Melanoma cells might temporally acquire tumor-initiating properties or switch from a status of tumor-initiating cells (TICs) to a more differentiated one depending on the tumor context. However, factors driving these functional changes are still unknown. We focused on the role of cyto/chemokines in shaping TICs isolated directly from tumor specimens of two melanoma patients, namely Me14346S and Me15888S. We analyzed the secretion profile of TICs and of their corresponding melanoma differentiated cells and we tested the ability of cyto/chemokines to influence TIC self-renewal and differentiation. We found that TICs, grown in vitro as melanospheres, had a complex secretory profile as compared to their differentiated counterparts. Some factors, such as CCL-2 and IL-8, also produced by adherent melanoma cells and melanocytes did not influence TIC properties. Conversely, IL-6, released by differentiated cells, reduced TIC self-renewal and induced TIC differentiation while IL-10, produced by Me15888S, strongly promoted TIC self-renewal through paracrine/autocrine actions. Complete neutralization of IL-10 activity by gene silencing and antibody-mediated blocking of the IL-10Rα was required to sensitize Me15888S to IL-6-induced differentiation. For the first time these results show that functional heterogeneity of melanoma could be directly influenced by inflammatory and suppressive soluble factors, with IL-6 favoring TIC differentiation, and IL-10 supporting TIC self-renewal. Thus, understanding the tumor microenvironment (TME) role in modulating melanoma TIC phenotype is fundamental to identifying novel therapeutic targets to achieve long-lasting regression of metastatic melanoma. S tem C ells 2016;34:2449-2460 [ABSTRACT FROM AUTHOR]

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine that is over-expressed in several human neoplastic cells. When MIF binds its receptor (CD74) and co-receptor (CD44), it initiates signaling cascades that orchestrate cell proliferation and survival, and it can directly modulate the activity of AMPK. These activities indicate that MIF potentially regulates cell survival and metabolism. We found that MIF was primarily co-expressed with CD74 in 16 out of 23 papillary thyroid carcinoma (PTC) and in all the 27 available anaplastic thyroid carcinoma (ATC) biopsy samples. MIF and CD74 were co-expressed in TPC-1 and HTC-C3 cell lines. The selective MIF inhibitor, 4-iodo-6- phenylpyrimidine (4-IPP), blocked MIF/CD74 internalization, activated JNK, and dosedependently inhibited proliferation inducing apoptosis and mitotic cell death. In two CD74-negative cell lines, NIM-1 and K1, 4-IPP treatment partially reduced proliferation. Coordinated MIF and CD74 expression appeared to confer in tumor cells the plasticity necessary to escape cell cycle regulation, metabolic changes, and stress conditions. MIF/CD74 signaling removal made cells susceptible to apoptosis and mitotic cell death. This finding suggests a possible avenue for targeting DNA endoreduplication, thus preventing the proliferation of therapy-resistant cell subpopulations. This study highlights MIF/CD74 axis as an important player in the biology of aggressive thyroid neoplasms. [ABSTRACT FROM AUTHOR]

Pulmonary adenoma susceptibility 1 (Pas1) is the major locus responsible for lung tumor susceptibility in mice; among the six genes mapping in this locus, Kras is considered the best candidate for Pas1 function although how it determines tumor susceptibility remains unknown. In an (A/J×C57BL/6)F4 intercross population treated with urethane to induce lung tumors, Pas1 not only modulated tumor susceptibility (LOD score = 48, 69% of phenotypic variance explained) but also acted, in lung tumor tissue, as an expression quantitative trait locus (QTL) for Kras-4A, one of two alternatively spliced Kras transcripts, but not Kras-4B. Additionally, Kras-4A showed differential allelic expression in lung tumor tissue of (A/J×C57BL/6)F4 heterozygous mice, with significantly higher expression from the A/J-derived allele; these results suggest that cis-acting elements control Kras-4A expression. In normal lung tissue from untreated mice of the same cross, Kras-4A levels were also highly linked to the Pas1 locus (LOD score = 23.2, 62% of phenotypic variance explained) and preferentially generated from the A/J-derived allele, indicating that Pas1 is an expression QTL in normal lung tissue as well. Overall, the present findings shed new light on the genetic mechanism by which Pas1 modulates the susceptibility to lung tumorigenesis, through the fine control of Kras isoform levels. [ABSTRACT FROM AUTHOR]

Lung adenocarcinoma patients of similar clinical stage and undergoing the same treatments often have marked interindividual variations in prognosis. These clinical discrepancies may be due to the genetic background modulating an individual’s predisposition to fighting cancer. Herein, we hypothesized that the lung microenvironment, as reflected by its expression profile, may affect lung adenocarcinoma patients’ survival. The transcriptome of non-involved lung tissue, excised from a discovery series of 204 lung adenocarcinoma patients, was evaluated using whole-genome expression microarrays (with probes corresponding to 28 688 well-annotated coding sequences). Genes associated with survival status at 60 months were identified by Cox regression analysis (adjusted for gender, age and clinical stage) and retested in a validation series of 78 additional cases. RNA-Seq analysis from non-involved lung tissue of 12 patients was performed to characterize the different isoforms of candidate genes. Ten genes for which the loge-transformed hazard ratios expressed the same direction of effect in the discovery (P < 1.0 × 10−3) and validation series comprised the gene expression signature associated with survival: CNTNAP1, PKNOX1, FAM156A, FRMD8, GALNTL1, TXNDC12, SNTB1, PPP3R1, SNX10 and SERPINH1. RNA sequencing highlighted the complex expression pattern of these genes in non-involved lung tissue from different patients and permitted the detection of a read-through gene fusion between PPP3R1 and the flanking gene (CNRIP1) as well as a novel isoform of CNTNAP1. Our findings support the hypothesis that individual genetic characteristics, evidenced by the expression pattern of non-involved tissue, influence the outcome of lung adenocarcinoma patients. [ABSTRACT FROM AUTHOR]

Background: In an intercross between the SWR/J and BALB/c mouse strains, the pulmonary adenoma progression 1 (Papg1) locus on chromosome 4 modulates lung tumor size, one of several measures of lung tumor progression. This locus has not been fully characterized and defined in its extent and genetic content. Fine mapping of this and other loci affecting lung tumor phenotype is possible using recombinant inbred strains. Results: A population of 376 mice, obtained by crossing mice of the SWR/J strain with CXBN recombinant inbred mice, was treated with a single dose of urethane and assayed for multiplicity of large lung tumors (N2lung). A genome-wide analysis comparing N2lung with 6364 autosomal SNPs revealed multiple peaks of association. The Papg1 locus had two peaks, at rs3654162 (70.574 Mb, -logP=2.8) and rs6209043 (86.606 Mb, -logP=2.7), joined by an interval of weaker statistical association; these data confirm the presence of Papg1 on chromosome 4 and reduce the mapping region to two stretches of ~6.8 and ~4.2 Mb, in the proximal and distal peaks, respectively. The distal peak included Cdkn2a, a gene already proposed as being involved in Papg1 function. Other loci possibly modulating N2lung were detected on chromosomes 5, 8, 9, 11, 15, and 19, but analysis for linkage disequilibrium of these putative loci with Papg1 locus suggested that only those on chromosomes 11 and 15 were true positives. Conclusions: These findings suggest that Papg1 consists, most likely, of two distinct, nearby loci, and point to putative additional loci on chromosomes 11 and 15 modulating lung tumor size. Within Papg1, Cdkn2a appears to be a strong candidate gene while additional Papg1 genes await to be identified. Greater knowledge of the genetic and biochemical mechanisms underlying the germ-line modulation of lung tumor size in mice is relevant to other species, including humans, in that it may help identify new therapeutic targets in the fight against tumor progression. [ABSTRACT FROM AUTHOR]

We carried out genome-wide association (GWA) studies in inbred mouse strains characterized for their lung tumor susceptibility phenotypes (spontaneous or urethane-induced) with panels of 12,959 (13K) or 138,793 (140K) singlenucleotide polymorphisms (SNPs). Above the statistical thresholds, we detected only SNP rs3681853 on Chromosome 5, two SNPs in the pulmonary adenoma susceptibility 1 (Pas1) locus, and SNP rs4174648 on Chromosome 16 for spontaneous tumor incidence, urethane-induced tumor incidence, and urethane-induced tumor multiplicity, respectively, with the 13K SNP panel, but only the Pas1 locus with the 140K SNP panel. Haplotype analysis carried out in the latter panel detected four additional loci. Loci reported in previous GWA studies failed to replicate. Genome-wide genetic linkage analysis in urethanetreated (BALB/x6C3H/He)F2, (BALB/cxSWR/J)F2, and (A/JxC3H/He)F2 mice showed that Pas1, but none of the other loci detected previously or herein by GWA, had a significant effect. The Lasc1 gene, identified by GWA as a functional element (Nat. Genet., 38:888-95, 2006), showed no genetic effects in the two independent intercross mouse populations containing both alleles, nor was it expressed in mouse normal lung or lung tumors. Our results indicate that GWA studies in mouse inbred strains can suffer a high rate of false-positive results and that such an approach should be used in conjunction with classical linkage mapping in genetic crosses. [ABSTRACT FROM AUTHOR]

Analysis of seven candidate genes mapping in the 1-Mb region of the mouse pulmonary adenoma resistance 4 (Par4) locus revealed a single amino-acid change, consisting in a nonconservative Arg968Cys variation in the juxtamembrane domain of the Met proto-oncogene-encoded protein. The BALB/c strain (resistant allele) carried the Arg allele, whereas the SWR/J mouse strain (Par4-susceptible allele) carried the Cys variation, recently proven to functionally modulate tumorigenesis. Seven genetic linkage crosses herein analysed and six crosses reported in the literature pointed to the candidacy of the Met gene for Par4. Analysis of genomic DNA of 126 lung adenocarcinoma patients for the Met juxtamembrane domain revealed the same Arg/Cys variation at the mouse homologous position in one patient; two other patients carried additional variants in the same domain, suggesting a potential role for rare MET juxtamembrane variants in human lung cancer.Oncogene (2005) 24, 1084-1090. doi:10.1038/sj.onc.1208324 Published online 13 December 2004 [ABSTRACT FROM AUTHOR]

The pulmonary adenoma susceptibility 1 (Pas1) locus affects inherited predisposition and resistance to chemically induced lung tumorigenesis in mice. The A/J and C57BL/6J mouse strains carry the susceptibility and resistance allele, respectively. We identified and genotyped 65 polymorphisms in the Pas1 locus region in 29 mouse inbred strains, and delimited the Pas1 locus to a minimal region of 468?kb containing six genes. That region defined a core Pas1 haplotype with 42 tightly linked markers, including intragenic polymorphisms in five genes (Bcat1, Lrmp, Las1, Ghiso, and Kras2) and amino-acid changes in three genes (Lrmp, Las1, Lmna-rs1). In (A/J × C57BL/6J)F1 mouse lung tumors, the Lmna-rs1 gene was completely downregulated, whereas allele-specific downregulation of the C57BL/6J-derived allele was observed at the Las1 gene, suggesting the potential role of these genes in tumor suppression. These results indicate a complex multigenic nature of the Pas1 locus, and point to a functional role for both intronic and exonic polymorphisms of the six genes of the Pas1 haplotype in lung tumor susceptibility.Oncogene (2004) 23, 4495-4504. doi:10.1038/sj.onc.1207584 Published online 5 April 2004 [ABSTRACT FROM AUTHOR]

The mouse parathyroid hormone-like hormone PthlhPro and PthlhThr variants are linked with susceptibility and resistance to skin carcinogenesis of Car-S and Car-R mice, respectively, and with in vitro effects (Oncogene, 19: 5324-5328, 2000). We have identified an additional Pthlh variant, consisting of Thr and three amino-acid changes in the C-terminus (PthlhSerAspTyr), carried by an evolutionarily distant Mus spretus (SPRET/Ei) inbred strain. When transfected into NCI-H520 tumor cells, this PthlhSerAspTyr variant did not stimulate tumor growth in nude mice. Analysis of cell adhesion, migration, and invasion patterns of PthlhPro-, PthlhThr-, and PthlhSerAspTyr-transfected NCI-H520 cells revealed a 1.5-fold decrease in adhesion efficiency on both collagen type I and Matrigel, and a 5-6-fold increase in migration capability in PthlhPro transfectants as compared to nontransfected, vector-transfected, PthlhThr-, or PthlhSerAspTyr-transfected cells. These findings suggest that the cancer modifier effects of the mouse Pthlh gene are mediated by differential cell adhesion and migration effects of PTHrP variants.Oncogene (2003) 22, 7711-7715. doi:10.1038/sj.onc.1207088 [ABSTRACT FROM AUTHOR]

Two outbred mouse lines, phenotypically selected for differential subcutaneous (s.c.) acute inflammatory response (AIR), were analysed for urethane-induced lung inflammatory response and susceptibility to lung tumorigenesis. AIRmin mice, which show a low response to s.c. acute inflammation, developed a persistent subacute lung inflammatory response and a 40-fold higher lung tumor multiplicity than did AIRmax mice, which are selected for high response to s.c. acute inflammation and showed a transient lung inflammatory response. A highly significant linkage disequilibrium pattern was observed in AIRmax and AIRmin mice at marker alleles located within a 452-kb pulmonary adenoma susceptibility 1 (Pas1) locus region, thus defining the location of gene candidacy for inflammatory response and for the biological effects of Pas1 in this region. AIRmin and AIRmax mice segregated by descent the Pas1s and Pas1r alleles, respectively, providing evidence for the involvement of the Pas1 locus in the inflammatory response. The 452-kb region contains Kras2 and four additional genes, including the lymphoid-restricted membrane protein (Lrmp) gene, whose Pro→Leu nonconservative variation was linked with inflammatory response and Pas1 allelotype. These results provide a model to explore the mechanism underlying inherited predisposition to lung cancer in the context of a link to inflammation.Oncogene (2003) 22, 426–432. doi:10.1038/sj.onc.1206157 [ABSTRACT FROM AUTHOR]

The stearoyl-CoA desaturase 1 (Scd1) gene is involved in the synthesis and regulation of unsaturated fatty acids. Its expression is increased by several treatments/conditions that are associated with hepatocarcinogenesis (peroxisome proliferators, iron overload, dichloroacetic acid). We found that the Scd1 gene is differentially expressed, showing >10-fold higher mRNA levels in the normal liver tissue of C3H/He mice, which are genetically susceptible to hepatocarcinogenesis, than of BALB/c mice, which are resistant. Similarly, Scd1 mRNA expression was ∼4-fold higher in the normal liver of F344 rats, which are susceptible to hepatocarcinogenesis, than in Brown Norway (BN) rats, which are resistant. The chromosomal location of the Scd1 locus, both in mice and rats, excludes Scd1 candidacy as a hepatocellular tumor-modifier gene, as the Scd1 locus did not show allele-specific effects in a BALB/c×C3H/He intercross or in a BN×F344 backcross and intercross. No Scd1 coding polymorphisms were detected in the mouse and the rat strains showing elevated Scd1 expression. These results suggest that the Scd1 gene represents a downstream target of hepatocellular tumor-modifier loci in two rodent species. [ABSTRACT FROM PUBLISHER]

Expressed-sequence tag (EST) maps are an adjunct to sequencebased analytical methods of gene detection and localization for those species for which such data are available, and provide anchors for high-density homology and orthology mapping in species for which large-scale sequencing has yet to be done. Species for which radiation hybrid-based transcript maps have been established include human, rat, mouse, dog, cat and zebrafish. We have established a comprehensive first-generation-placement radiation hybrid map of the mouse consisting of 5,904 mapped markers (3,993 ESTs and 1,911 sequencetagged sites (STSs)). The mapped ESTs, which often originate from small-EST clusters, are enriched for genes expressed during early mouse embryogenesis and are probably different from those localized in humans. We have confirmed by in situ hybridization that even singleton ESTs, which are usually not retained for mapping studies, may represent bona fide transcribed sequences. Our studies on mouse chromosomes 12 and 14 orthologous to human chromosome 14 show the power of our radiation hybrid map as a predictive tool for orthology mapping in humans. [ABSTRACT FROM AUTHOR]

Car-R and Car-S outbred mouse lines, phenotypically selected for resistance and susceptibility to skin carcinogenesis respectively, show significant linkage disequilibrium (LD) at genetic markers mapping on chromosomal regions where skin cancer modifier loci (Skts3, Skts1, and Psl1 on Chrs 5, 7, and 9 respectively) have been mapped in standard crosses. Analysis of these regions for genetic linkage with skin cancer phenotypes in 245 (Car-R × Car-S)F2 intercross mice, by using single nucleotide polymorphisms (SNPs), revealed significant linkage at a possible allelic form of the Skts1 locus, whose mapping region was shortened to a <5.5-cM interval near the Tyr locus. The Car-derived Skts1 locus was linked with papilloma multiplicity and latency by a recessive inheritance of the susceptibility allele. Putative loci on Chr 5 (Skts3) and 9 (Psl1) showed no significant linkage. These results point to the important role of the Stks1 locus in mouse skin tumorigenesis in independent crosses. The shortened Skts1 mapping region should facilitate the identification of candidate genes. [ABSTRACT FROM AUTHOR]

The parathyroid hormone-related protein (PTHrP) gene (Pthlh) maps in the distal region of mouse chromosome 6 that contains a quantitative trait locus associated with genetic predisposition to skin tumorigenesis. Here, we report a genetic polymorphism located in the osteostatin encoding region of the Pthlh gene and that produces Thr/Pro PTHrP variants. PthlhThr and PthlhPro alleles were significantly linked with resistance and susceptibility to skin carcinogenesis in phenotypically selected Car-R and Car-S outbred mice. Transfection of human NCI-H520 squamous cell carcinoma cells with the PthlhPro allele resulted in cells growing in clusters, tending to pile up, and growing at a significantly faster rate in nude mice than non-transfected and PthlhThr-transfected cells. These results point to the role of the Pthlh gene as a cancer modifier gene in skin tumorigenesis. Oncogene (2000) 19, 5324–5328. [ABSTRACT FROM AUTHOR]

Simple Summary: Several studies including ours suggest a pro-tumoral role of senescent thyrocytes in thyroid tumors. On the other hand, M2-like tumor associated macrophages infiltration increases with thyroid cancer aggressiveness. In this work, we used senescent thyrocytes and thyroid tumor cells as models of early and late tumor stages, respectively, and demonstrated their in vivo capability to recruit and polarize macrophages toward a pro-tumoral M2-like phenotype. These findings pave the way for the design of new therapeutic approaches for thyroid tumors based on the elimination or activity modulation of senescent cells and/or infiltrating macrophages. Inflammation plays a critical role in thyroid cancer onset and progression. We previously characterized the in vitro interplay between macrophages and senescent human thyrocytes and thyroid tumor-derived cell lines, modeling the early and the late thyroid tumor phases, respectively. We reported that both models are able to induce pro-tumoral M2-like macrophage polarization, through the activation of the COX2-PGE2 axis. Here, we investigated the presence of macrophage infiltrating cells in mouse xenografts derived from the above described cells models. We showed that subcutaneous injection in immunodeficient mice of both senescent human thyrocytes and thyroid tumor-derived cell lines elicits macrophage recruitment. Furthermore, considering the type of macrophage infiltrate, we observed a stronger infiltration of Arginase I positive cells (M2-like). Overall, these results demonstrate the in vivo capability of senescent and tumor thyroid cells to recruit and polarize macrophages, suggesting that the promotion of a pro-tumoral microenvironment through tumor associated macrophages may occurs in late as well as in early thyroid tumor stages, favoring tumor onset and progression. [ABSTRACT FROM AUTHOR]

Loss of heterozygosity (LOH) at specific chromosomal regions is a frequent event in poorly differentiated human hepatocellular carcinomas (HCCs), but rare in mouse HCCs. This behavior could depend on interspecies differences in mechanisms of hepatocarcinogenesis or in developmental stage of lesions. To verify if LOH is involved in rat hepatocarcinogenesis, we studied LOH frequency in slowly growing neoplastic nodules induced by Solt–Farber model in diethylnitrosamine-initiated BFF1 rats. We analyzed, with microsatellites, markers at 67 rat loci dispersed over all chromosomes, corresponding to regions homologous to those lost in human HCCs or containing hepatocellular susceptibility (Hcs) or resistance (Hcr) loci in rat and mouse. In agreement with previous findings with mouse HCCs, but at variance with human HCCs, no detectable LOH was found at any locus in rats, suggesting rare LOH involvement in neoplastic nodules, with low tendency to progress to full malignancy, of BFF1 rats. [ABSTRACT FROM PUBLISHER]

Inherited predisposition to lung cancer is a phenotypic trait shared by different mouse inbred strains that show either a high or an intermediate predisposition. Other strains are instead genetically resistant. The Pasl locus is the major determinant of lung cancer predisposition in the A/J strain (Gariboldi et al. 1993). To define the determinants of susceptibility to lung tumorigenesis in the highly susceptible SWR/J and in the intermediately susceptible BALB/c mice, we analyzed (BALB/c x SWR/J)F2 and (BALB/c x C3H/He)F2 crosses by genetic linkage experiments. The present results provide unequivocal evidence that the same Pas1/+ allele that leads to lung cancer predisposition is shared by A/J, SWR/J, and BALB/c strains. The intermediate susceptibility of the BALB/c strain would result by interaction of Pas1 locus with lung cancer resistance loci. [ABSTRACT FROM AUTHOR]

The murine hybrids (C57BL/6JxC3Hf)F1 (B6C3) and (C57BL/6JxBALB/c)F1 (B6C), which have a high and low spontaneous and induced incidence of hepatocellular tumors, respectively, were treated with a single dose of NDEA at 1 week of age followed by TCPOBOP, a phenobarbital-like promoter of liver carcinogenesis, or by vehicle, and sacrificed at 30 weeks of age. The frequency per liver of hepatocellular nodules was similar in the two hybrids. However, in male mice the mean volume of nodules was about 10-fold greater in B6C3 than in B6C mice receiving NDEA followed by vehicle, and the treatment with TCPOBOP after NDEA stimulated nodule growth, with a much greater response in B6C3 mice. In female mice no differences in the mean volume of nodules were seen between hybrids after NDEA and vehicle, whereas upon NDEA and TCPOBOP treatment the mean volume of nodules was 25-fold greater in B6C3 than in B6C females. In addition, a few hepatocellular adenomas and carcinomas were observed, mostly in animals treated with NDEA and TCPOBOP, and they were 3-fold more numerous among B6C3 than B6C mice. TCPOBOP alone induced the same biochemical and hyperplastic effects in the liver of both hybrids. Using DNA probes homologous to Moloney murine leukemia virus, intracisternal A particle and virus-like 30S sequences, no correlation was apparent between the expression of any of these endogenous retroviral families and the strain susceptibility to hepatocarcinogenesis. We hypothesize that the different susceptibility to hepatocarcinogenesis between B6C3 and B6C mice is related to a higher growth rate of B6C3 than B6C initiated liver cells. [ABSTRACT FROM AUTHOR]

Transgenic mice containing one copy of hepatitis B virus (HBV) genome without the core gene and expressing hepatitis B surface antigen (HBsAg) were crossed with C3H/He mice. The Fl hybrids (˜50% HBV positive and ˜507percnt; HBV negative) were treated with a single dose of diethylnitrosamine (NDEA) or -dimethylaminoazobenzene (DAB) given at 7 days of age, or were untreated. Mice were kept under observation without further treatments until 30 weeks old and then killed. Stereological analysis of liver nodules and estimations of their size distribution demonstrated a significative enhancing effect of HBV transgene in both NDEA- and DAB-induced hepatocarcinogenesis in male mice. Hepatocellular adenomas and carcinomas were also more frequent in NDEA-treated HBV-positive than HBV-negative male mice. Female mice showed a lower tumorigenic response than males without significant differences between groups of HBV-positive and HBV-negative mice. It is proposed that the presence of the transgene enhanced carcinogen-induced hepatocarcinogenesis. [ABSTRACT FROM PUBLISHER]

The effects of phenobarbital (PB) and 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) on liver hyperplasia, induction of microsomal enzyme activities, and two-stage hepatocarcinogenesis were evaluated in B6C3F1 female mice. For 4 weeks four groups of mice received PB (500 p.p.m. in the drinking water), TCPOBOP (3 mg/kg i.p. once every week), PB together with TCPOBOP or corn oil vehicle i.p. TCPOBOP induced liver hyperplasia and hypertrophy and increased p-nitroanisole-O-demethylase and aminopyrine-N-demethylase more than PB. Neither chemical changed UDPG-transferase activity. The association of PB and TCPOBOP gave the same effects as TCPOBOP alone. Other four groups of mice were treated with N-nitroso-N-diethylamine at 7 days of age and then, starting from 8 weeks of age, received the above specified weekly treatments for 20 weeks and were then sacrificed. Hepatocellular nodules > 150 μm were found in all animals of all groups. Due to increased size of the liver compared to controls, the number of nodules/cm decreased after PB and TCPOBOP treatments given alone or together; however the mean volume of nodules and the percentage of liver volume occupied by nodules increased after TCPOBOP but not after BP treatment, and the association of PB and TCPOBOP was even more effective than TCPOBOP alone. Hepatocellular adenomas >2.4 mm in diameter were observed in 5 of 10 TCPOBOP-treated mice (total of 11 nodules) and in 5 of 11 mice that received PB plus TCPOBOP (total of 15 nodules). Hepatocellular carcinomas were seen in one mouse treated with PB and in three mice given PB and TCPOBOP. [ABSTRACT FROM PUBLISHER]

Car-R (carcinogenesis-resistant) and Car-S (carcinogenesis-susceptible) outbred mice, obtained by phenotypic selection from an initial intercross of eight inbred strains, show a >100-fold difference in their susceptibility to two-stage skin tumorigenesis. We found that the lines carry a high degree of genetic polymorphism, with an average heterozygosity of 0.39. This polymorphism allowed the use of linkage disequilibrium (LD) and haplotype analysis for the mapping of a skin cancer modifier locus on Chr 7, in a short region of 6 cM, around the Tyr gene. Car-S mice inherited the susceptibility allele at this locus from the A/J, BALB/c, SJL/J, and SWR/J strains. Our results demonstrate the feasibility and usefulness of mapping disease genes by LD in phenotypically selected, genetically heterogeneous animals. [ABSTRACT FROM AUTHOR]