Correction: The genetic consequences of dog breed formation-Accumulation of deleterious genetic variation and fixation of mutations associated with myxomatous mitral valve disease in cavalier King Charles spaniels.

[This corrects the article DOI: 10.1371/journal.pgen.1009726.].

The genetic consequences of dog breed formation-Accumulation of deleterious genetic variation and fixation of mutations associated with myxomatous mitral valve disease in cavalier King Charles spaniels.

Selective breeding for desirable traits in strictly controlled populations has generated an extraordinary diversity in canine morphology and behaviour, but has also led to loss of genetic variation and random entrapment of disease alleles. As a consequence, specific diseases are now prevalent in certain breeds, but whether the recent breeding practice led to an overall increase in genetic load remains unclear. Here we generate whole genome sequencing (WGS) data from 20 dogs per breed from eight breeds and document a ~10% rise in the number of derived alleles per genome at evolutionarily conserved sites in the heavily bottlenecked cavalier King Charles spaniel breed (cKCs) relative to in most breeds studied here. Our finding represents the first clear indication of a relative increase in levels of deleterious genetic variation in a specific breed, arguing that recent breeding practices probably were associated with an accumulation of genetic load in dogs. We then use the WGS data to identify candidate risk alleles for the most common cause for veterinary care in cKCs-the heart disease myxomatous mitral valve disease (MMVD). We verify a potential link to MMVD for candidate variants near the heart specific NEBL gene in a dachshund population and show that two of the NEBL candidate variants have regulatory potential in heart-derived cell lines and are associated with reduced NEBL isoform nebulette expression in papillary muscle (but not in mitral valve, nor in left ventricular wall). Alleles linked to reduced nebulette expression may hence predispose cKCs and other breeds to MMVD via loss of papillary muscle integrity.

Translational Safety Genetics.

The emerging field of translational safety genetics is providing new opportunities to enhance drug discovery and development. Genetic variation in therapeutic drug targets, off-target interactors and relevant drug metabolism/disposition pathways can contribute to diverse drug pharmacologic and toxicologic responses between different animal species, strains and geographic origins. Recent advances in the sequencing of rodent, canine, nonhuman primate, and minipig genomes have dramatically improved the ability to select the most appropriate animal species for preclinical drug toxicity studies based on genotypic characterization of drug targets/pathways and drug metabolism and/or disposition, thus avoiding inconclusive or misleading animal studies, consistent with the principles of the 3Rs (replacement, reduction and refinement). The genetic background of individual animals should also be taken into consideration when interpreting phenotypic outcomes from toxicity studies and susceptibilities to spontaneous safety-relevant background findings.

Reciprocal changes in DNA methylation and hydroxymethylation and a broad repressive epigenetic switch characterize FMR1 transcriptional silencing in fragile X syndrome.

BACKGROUND: Fragile X syndrome (FXS) is the most common form of inherited intellectual disability, resulting from the loss of function of the fragile X mental retardation 1 (FMR1) gene. The molecular pathways associated with FMR1 epigenetic silencing are still elusive, and their characterization may enhance the discovery of novel therapeutic targets as well as the development of novel clinical biomarkers for disease status. RESULTS: We have deployed customized epigenomic profiling assays to comprehensively map the FMR1 locus chromatin landscape in peripheral mononuclear blood cells (PBMCs) from eight FXS patients and in fibroblast cell lines derived from three FXS patient. Deoxyribonucleic acid (DNA) methylation (5-methylcytosine (5mC)) and hydroxymethylation (5-hydroxymethylcytosine (5hmC)) profiling using methylated DNA immunoprecipitation (MeDIP) combined with a custom FMR1 microarray identifies novel regions of DNA (hydroxy)methylation changes within the FMR1 gene body as well as in proximal flanking regions. At the region surrounding the FMR1 transcriptional start sites, increased levels of 5mC were associated to reciprocal changes in 5hmC, representing a novel molecular feature of FXS disease. Locus-specific validation of FMR1 5mC and 5hmC changes highlighted inter-individual differences that may account for the expected DNA methylation mosaicism observed at the FMR1 locus in FXS patients. Chromatin immunoprecipitation (ChIP) profiling of FMR1 histone modifications, together with 5mC/5hmC and gene expression analyses, support a functional relationship between 5hmC levels and FMR1 transcriptional activation and reveal cell-type specific differences in FMR1 epigenetic regulation. Furthermore, whilst 5mC FMR1 levels positively correlated with FXS disease severity (clinical scores of aberrant behavior), our data reveal for the first time an inverse correlation between 5hmC FMR1 levels and FXS disease severity. CONCLUSIONS: We identify novel, cell-type specific, regions of FMR1 epigenetic changes in FXS patient cells, providing new insights into the molecular mechanisms of FXS. We propose that the combined measurement of 5mC and 5hmC at selected regions of the FMR1 locus may significantly enhance FXS clinical diagnostics and patient stratification.

Phenobarbital induces cell cycle transcriptional responses in mouse liver humanized for constitutive androstane and pregnane x receptors.

The constitutive androstane receptor (CAR) and the pregnane X receptor (PXR) are closely related nuclear receptors involved in drug metabolism and play important roles in the mechanism of phenobarbital (PB)-induced rodent nongenotoxic hepatocarcinogenesis. Here, we have used a humanized CAR/PXR mouse model to examine potential species differences in receptor-dependent mechanisms underlying liver tissue molecular responses to PB. Early and late transcriptomic responses to sustained PB exposure were investigated in liver tissue from double knock-out CAR and PXR (CAR(KO)-PXR(KO)), double humanized CAR and PXR (CAR(h)-PXR(h)), and wild-type C57BL/6 mice. Wild-type and CAR(h)-PXR(h) mouse livers exhibited temporally and quantitatively similar transcriptional responses during 91 days of PB exposure including the sustained induction of the xenobiotic response gene Cyp2b10, the Wnt signaling inhibitor Wisp1, and noncoding RNA biomarkers from the Dlk1-Dio3 locus. Transient induction of DNA replication (Hells, Mcm6, and Esco2) and mitotic genes (Ccnb2, Cdc20, and Cdk1) and the proliferation-related nuclear antigen Mki67 were observed with peak expression occurring between 1 and 7 days PB exposure. All these transcriptional responses were absent in CAR(KO)-PXR(KO) mouse livers and largely reversible in wild-type and CAR(h)-PXR(h) mouse livers following 91 days of PB exposure and a subsequent 4-week recovery period. Furthermore, PB-mediated upregulation of the noncoding RNA Meg3, which has recently been associated with cellular pluripotency, exhibited a similar dose response and perivenous hepatocyte-specific localization in both wild-type and CAR(h)-PXR(h) mice. Thus, mouse livers coexpressing human CAR and PXR support both the xenobiotic metabolizing and the proliferative transcriptional responses following exposure to PB.

Differential expression of dipeptidyl peptidase IV in human versus cynomolgus monkey skin eccrine sweat glands.

Dipeptidyl peptidase IV (DPP4) is a peptidase whose inhibition is beneficial in Type II diabetes treatment. Several evidences suggest potential implication of DPP4 in skin disorders such as psoriasis, keloids and fibrotic skin diseases where its inhibition could also be beneficial. DPP4 expression in human skin was described mainly in dermal fibroblasts and a subset of keratinocytes in the basal layer. Of importance in the perspective of preclinical experimentation, DPP4 distribution in skin of non-human primate species has not been documented. This report evidences unexpected differences between a set of human and cynomolgus monkey skin samples revealing a major expression of DPP4 in eccrine sweat glands of cynomolgus monkeys but not in humans. This represents a unique distinctive feature compared to the conserved expression of dipeptidyl peptidases 8 and 9 and potential relevant DPP4 substrates such as neuropeptide Y (NPY) and receptors (NPY-receptor 1 and Neurokinin receptor). Finally the observation that cathepsin D, an unrelated protease, shows the opposite expression compared to DPP4 (present in human but not in cynomolgus monkey eccrine sweat glands) could indicate that human eccrine sweat glands evolved a divergent protease repertoire compared to non-human primates. These unexpected differences in the eccrine sweat glands protease repertoire will need to be confirmed extending the analysis to a major number of donors but could imply possible biochemical divergences, reflecting the functional evolution of the glands and the control of their activity. Our findings also demonstrate that non-human primates studies aiming at understanding DPP4 function in skin biology are not readily translatable to human.

Heart structure-specific transcriptomic atlas reveals conserved microRNA-mRNA interactions.

MicroRNAs are short non-coding RNAs that regulate gene expression at the post-transcriptional level and play key roles in heart development and cardiovascular diseases. Here, we have characterized the expression and distribution of microRNAs across eight cardiac structures (left and right ventricles, apex, papillary muscle, septum, left and right atrium and valves) in rat, Beagle dog and cynomolgus monkey using microRNA sequencing. Conserved microRNA signatures enriched in specific heart structures across these species were identified for cardiac valve (miR-let-7c, miR-125b, miR-127, miR-199a-3p, miR-204, miR-320, miR-99b, miR-328 and miR-744) and myocardium (miR-1, miR-133b, miR-133a, miR-208b, miR-30e, miR-499-5p, miR-30e*). The relative abundance of myocardium-enriched (miR-1) and valve-enriched (miR-125b-5p and miR-204) microRNAs was confirmed using in situ hybridization. MicroRNA-mRNA interactions potentially relevant for cardiac functions were explored using anti-correlation expression analysis and microRNA target prediction algorithms. Interactions between miR-1/Timp3, miR-125b/Rbm24, miR-204/Tgfbr2 and miR-208b/Csnk2a2 were identified and experimentally investigated in human pulmonary smooth muscle cells and luciferase reporter assays. In conclusion, we have generated a high-resolution heart structure-specific mRNA/microRNA expression atlas for three mammalian species that provides a novel resource for investigating novel microRNA regulatory circuits involved in cardiac molecular physiopathology.

Identification of Dlk1-Dio3 imprinted gene cluster noncoding RNAs as novel candidate biomarkers for liver tumor promotion.

The molecular events during nongenotoxic carcinogenesis and their temporal order are poorly understood but thought to include long-lasting perturbations of gene expression. Here, we have investigated the temporal sequence of molecular and pathological perturbations at early stages of phenobarbital (PB) mediated liver tumor promotion in vivo. Molecular profiling (mRNA, microRNA [miRNA], DNA methylation, and proteins) of mouse liver during 13 weeks of PB treatment revealed progressive increases in hepatic expression of long noncoding RNAs and miRNAs originating from the Dlk1-Dio3 imprinted gene cluster, a locus that has recently been associated with stem cell pluripotency in mice and various neoplasms in humans. PB induction of the Dlk1-Dio3 cluster noncoding RNA (ncRNA) Meg3 was localized to glutamine synthetase-positive hypertrophic perivenous hepatocytes, suggesting a role for ß-catenin signaling in the dysregulation of Dlk1-Dio3 ncRNAs. The carcinogenic relevance of Dlk1-Dio3 locus ncRNA induction was further supported by in vivo genetic dependence on constitutive androstane receptor and ß-catenin pathways. Our data identify Dlk1-Dio3 ncRNAs as novel candidate early biomarkers for mouse liver tumor promotion and provide new opportunities for assessing the carcinogenic potential of novel compounds.

Perturbation of microRNAs in rat heart during chronic doxorubicin treatment.

Anti-cancer therapy based on anthracyclines (DNA intercalating Topoisomerase II inhibitors) is limited by adverse effects of these compounds on the cardiovascular system, ultimately causing heart failure. Despite extensive investigations into the effects of doxorubicin on the cardiovascular system, the molecular mechanisms of toxicity remain largely unknown. MicroRNAs are endogenously transcribed non-coding 22 nucleotide long RNAs that regulate gene expression by decreasing mRNA stability and translation and play key roles in cardiac physiology and pathologies. Increasing doses of doxorubicin, but not etoposide (a Topoisomerase II inhibitor devoid of cardiovascular toxicity), specifically induced the up-regulation of miR-208b, miR-216b, miR-215, miR-34c and miR-367 in rat hearts. Furthermore, the lowest dosing regime (1 mg/kg/week for 2 weeks) led to a detectable increase of miR-216b in the absence of histopathological findings or alteration of classical cardiac stress biomarkers. In silico microRNA target predictions suggested that a number of doxorubicin-responsive microRNAs may regulate mRNAs involved in cardiac tissue remodeling. In particular miR-34c was able to mediate the DOX-induced changes of Sipa1 mRNA (a mitogen-induced Rap/Ran GTPase activating protein) at the post-transcriptional level and in a seed sequence dependent manner. Our results show that integrated heart tissue microRNA and mRNA profiling can provide valuable early genomic biomarkers of drug-induced cardiac injury as well as novel mechanistic insight into the underlying molecular pathways.

Phenobarbital mediates an epigenetic switch at the constitutive androstane receptor (CAR) target gene Cyp2b10 in the liver of B6C3F1 mice.

Evidence suggests that epigenetic perturbations are involved in the adverse effects associated with some drugs and toxicants, including certain classes of non-genotoxic carcinogens. Such epigenetic changes (altered DNA methylation and covalent histone modifications) may take place at the earliest stages of carcinogenesis and their identification holds great promise for biomedical research. Here, we evaluate the sensitivity and specificity of genome-wide epigenomic and transcriptomic profiling in phenobarbital (PB)-treated B6C3F1 mice, a well-characterized rodent model of non-genotoxic liver carcinogenesis. Methylated DNA Immunoprecipitation (MeDIP)-coupled microarray profiling of 17,967 promoter regions and 4,566 intergenic CpG islands was combined with genome-wide mRNA expression profiling to identify liver tissue-specific PB-mediated DNA methylation and transcriptional alterations. Only a limited number of significant anti-correlations were observed between PB-induced transcriptional and promoter-based DNA methylation perturbations. However, the constitutive androstane receptor (CAR) target gene Cyp2b10 was found to be concomitantly hypomethylated and transcriptionally activated in a liver tissue-specific manner following PB treatment. Furthermore, analysis of active and repressive histone modifications using chromatin immunoprecipitation revealed a strong PB-mediated epigenetic switch at the Cyp2b10 promoter. Our data reveal that PB-induced transcriptional perturbations are not generally associated with broad changes in the DNA methylation status at proximal promoters and suggest that the drug-inducible CAR pathway regulates an epigenetic switch from repressive to active chromatin at the target gene Cyp2b10. This study demonstrates the utility of integrated epigenomic and transcriptomic profiling for elucidating early mechanisms and biomarkers of non-genotoxic carcinogenesis.

Preclinical evaluation of potential nilotinib cardiotoxicity.

In vitro, concentrations ≥ 10 µM of nilotinib were needed to induce markers of cytotoxicity, apoptosis, and endoplasmic reticulum stress in both neonatal rat ventricular myocytes, a putative target tissue, and non-target heart fibroblasts, indicating a lack of cardiomyocyte-specific nilotinib toxicity in vitro. In rats, oral nilotinib treatment at 80 mg/kg for 4 weeks induced increased heart weight; however, this was not associated with relevant histopathological changes or effects on heart function. Thus, nilotinib at and above clinically relevant concentrations (4.27 µM) did not induce overt cardiovascular pathologies or heart failure in vitro or in vivo under study conditions.

Sotrastaurin and cyclosporine drug interaction study in healthy subjects.

INTRODUCTION: Sotrastaurin is an immunosuppressant that inhibits protein kinase C and blocks T-lymphocyte activation. The authors determined the effect of combining sotrastaurin with the calcineurin inhibitor cyclosporine on the pharmacokinetics and biomarker responses to both drugs. METHODS: This was a randomized, 4-period, crossover study in 20 healthy subjects who received single oral doses of (1) sotrastaurin 100 mg, (2) cyclosporine 400 mg, (3) 100 mg sotrastaurin with 100 mg cyclosporine and (4) 100 mg sotrastaurin with 400 mg cyclosporine. Blood samples were collected to measure drug levels and biomarkers of T-lymphocyte activation (interleukin-2 and tumor necrosis factor producing T-cells and interleukin-2 messenger RNA levels) and of T-lymphocyte proliferation (thymidine uptake). RESULTS: Sotrastaurin did not alter cyclosporine AUC; however, low-dose and high-dose cyclosporine increased sotrastaurin AUC by 1.2-fold [90% confidence interval, 1.1-1.4] and 1.8-fold [1.6-2.1], respectively. Adding high-dose cyclosporine to a low-therapeutic dose of sotrastaurin significantly enhanced the inhibition of cytokine production by 31% [95% confidence interval, 25-36%], of interleukin-2 messenger RNA levels by 13% [7-19%], and of thymidine uptake by 37% [32-42%] compared with sotrastaurin alone. Addition of low-dose cyclosporine elicited slightly lower enhancements in inhibition by 21% [14-28%], 6% [-4-16%], and 26% [21-30%], respectively, compared with sotrastaurin alone. CONCLUSIONS: Sotrastaurin did not alter the pharmacokinetics of cyclosporine, but cyclosporine increased sotrastaurin AUC up to 1.8-fold. The combined drugs elicited a significantly greater inhibition of T-cell activation and proliferation than sotrastaurin alone.

Urinary clusterin, cystatin C, beta2-microglobulin and total protein as markers to detect drug-induced kidney injury.

Earlier and more reliable detection of drug-induced kidney injury would improve clinical care and help to streamline drug-development. As the current standards to monitor renal function, such as blood urea nitrogen (BUN) or serum creatinine (SCr), are late indicators of kidney injury, we conducted ten nonclinical studies to rigorously assess the potential of four previously described nephrotoxicity markers to detect drug-induced kidney and liver injury. Whereas urinary clusterin outperformed BUN and SCr for detecting proximal tubular injury, urinary total protein, cystatin C and beta2-microglobulin showed a better diagnostic performance than BUN and SCr for detecting glomerular injury. Gene and protein expression analysis, in-situ hybridization and immunohistochemistry provide mechanistic evidence to support the use of these four markers for detecting kidney injury to guide regulatory decision making in drug development. The recognition of the qualification of these biomarkers by the EMEA and FDA will significantly enhance renal safety monitoring.

A panel of urinary biomarkers to monitor reversibility of renal injury and a serum marker with improved potential to assess renal function.

The Predictive Safety Testing Consortium's first regulatory submission to qualify kidney safety biomarkers revealed two deficiencies. To address the need for biomarkers that monitor recovery from agent-induced renal damage, we scored changes in the levels of urinary biomarkers in rats during recovery from renal injury induced by exposure to carbapenem A or gentamicin. All biomarkers responded to histologic tubular toxicities to varied degrees and with different kinetics. After a recovery period, all biomarkers returned to levels approaching those observed in uninjured animals. We next addressed the need for a serum biomarker that reflects general kidney function regardless of the exact site of renal injury. Our assay for serum cystatin C is more sensitive and specific than serum creatinine (SCr) or blood urea nitrogen (BUN) in monitoring generalized renal function after exposure of rats to eight nephrotoxicants and two hepatotoxicants. This sensitive serum biomarker will enable testing of renal function in animal studies that do not involve urine collection.

Sotrastaurin and tacrolimus coadministration: effects on pharmacokinetics and biomarker responses.

Sotrastaurin is an immunosuppressant that inhibits protein kinase C. In the prevention of acute rejection in organ transplantation, sotrastaurin might be combined with tacrolimus. A drug interaction study was performed in 18 healthy subjects who received single oral doses of sotrastaurin 400 mg, tacrolimus 7 mg, and the drug combination. Drug blood levels and lymphocyte activation and proliferation were measured. Tacrolimus did not alter the pharmacokinetics of sotrastaurin; however, sotrastaurin increased tacrolimus area under the concentration-time curve by 2.0-fold (90% confidence interval, 1.8-2.1). Production of interleukin-2 and tumor necrosis factor by T cells activated via calcium-independent pathways was inhibited by 75% ± 22% from baseline by sotrastaurin. Interleukin-2 messenger RNA levels were decreased by 90% ± 9% from baseline by sotrastaurin. Addition of tacrolimus to sotrastaurin had minimal or no effect on these biomarkers, consistent with tacrolimus' mechanism of action. Lymphocyte proliferation induced via calcium-dependent pathways was decreased from baseline by 82% ± 9% by sotrastaurin, 76% ± 11% by tacrolimus, and 96% ± 2% for the drug combination. How sotrastaurin and tacrolimus could be partnered in an immunosuppressive regimen will need to be established in the context of controlled clinical trials in organ transplant patients, taking into account the pharmacokinetic interaction on tacrolimus and the potentially enhanced immunosuppressive activity of this drug combination.

Imatinib does not induce cardiotoxicity at clinically relevant concentrations in preclinical studies.

Cytotoxic concentrations of imatinib mesylate (10-50 microM) were required to trigger markers of apoptosis and endoplasmic reticulum stress response in neonatal rat ventricular myocytes and fibroblasts, with no significant differences observed between c-Abl silenced and nonsilenced cells. In mice, oral or intraperitoneal imatinib treatment did not induce cardiovascular pathology or heart failure. In rats, high doses of oral imatinib did result in some cardiac hypertrophy. Multi-organ toxicities may have increased the cardiac workload and contributed to the cardiac hypertrophy observed in rats only. These data suggest that imatinib is not cardiotoxic at clinically relevant concentrations (5 microM).

Characterization and interlaboratory comparison of a gene expression signature for differentiating genotoxic mechanisms.

The genotoxicity testing battery is highly sensitive for detection of chemical carcinogens. However, it features a low specificity and provides only limited mechanistic information required for risk assessment of positive findings. This is especially important in case of positive findings in the in vitro chromosome damage assays, because chromosome damage may be also induced secondarily to cell death. An increasing body of evidence indicates that toxicogenomic analysis of cellular stress responses provides an insight into mechanisms of action of genotoxicants. To evaluate the utility of such a toxicogenomic analysis we evaluated gene expression profiles of TK6 cells treated with four model genotoxic agents using a targeted high density real-time PCR approach in a multilaboratory project coordinated by the Health and Environmental Sciences Institute Committee on the Application of Genomics in Mechanism-based Risk Assessment. We show that this gene profiling technology produced reproducible data across laboratories allowing us to conclude that expression analysis of a relevant gene set is capable of distinguishing compounds that cause DNA adducts or double strand breaks from those that interfere with mitotic spindle function or that cause chromosome damage as a consequence of cytotoxicity. Furthermore, our data suggest that the gene expression profiles at early time points are most likely to provide information relevant to mechanisms of genotoxic damage and that larger gene expression arrays will likely provide richer information for differentiating molecular mechanisms of action of genotoxicants. Although more compounds need to be tested to identify a robust molecular signature, this study confirms the potential of toxicogenomic analysis for investigation of genotoxic mechanisms.

The PKC inhibitor AEB071 may be a therapeutic option for psoriasis.

PKC isoforms tau, alpha, and beta play fundamental roles in the activation of T cells and other immune cell functions. Here we show that the PKC inhibitor AEB071 both abolishes the production of several cytokines by activated human T cells, keratinocytes, and macrophages in vitro and inhibits an acute allergic contact dermatitis response in rats. To translate these findings into humans, single and multiple ascending oral doses of AEB071 were administered to healthy volunteers and patients with psoriasis, respectively. AEB071 was well tolerated with no clinically relevant laboratory abnormalities. Ex vivo stimulation of lymphocytes from subjects exposed to single doses of AEB071 resulted in a dose-dependent inhibition of both lymphocyte proliferation and IL2 mRNA expression. Clinical severity of psoriasis was reduced up to 69% compared with baseline after 2 weeks of treatment, as measured by the Psoriasis Area Severity Index (PASI) score. The improvement in psoriasis patients was accompanied by histological improvement of skin lesions and may be partially explained by a substantial reduction of p40+ dermal cells, which are known to mediate psoriasis. These data suggest that AEB071 could be an effective novel treatment regimen for psoriasis and other autoimmune diseases, and that AEB071 warrants long-term studies to establish safety and efficacy.

Monitoring kidney safety in drug development: emerging technologies and their implications.

Drug-induced kidney injury is a serious and not uncommon adverse event which needs to be considered during drug development. The current standards used to monitor kidney function, such as blood urea nitrogen and serum creatinine, are late indicators of kidney injury and thus do not allow for timely intervention before loss of function. Improving the diagnosis and monitoring of kidney damage goes hand-in-hand with the identification of new biomarkers and the development of technologies that enable their sensitive and specific measurements. In order to move beyond restriction to internal company decisions, every entity that demonstrates the qualities of a biomarker must gain acceptance by health authorities if it is to be used for regulatory decision making in preclinical studies and clinical trials. This review focuses on the most promising achievements of new technologies applied to monitoring drug-induced nephrotoxicity (eg, gene expression, imaging, in vitro screening, protein assays) and on the use and implications of peripheral biomarkers such as the urinary protein biomarkers glutathione S-transferase-alpha, N-acetyl-beta-d-glucosaminidase, total protein, cystatin C, beta2-microglobulin, KIM-1, lipocalin-2 and serum cystatin C. Finally, the associated regulatory processes for use in clinics are also discussed.

Differentiation of spontaneous and induced mammary adenocarcinomas of the rat by gene expression profiling.

The differentiation of spontaneous and induced adenocarcinomas is of interest in the setting of carcinogenicity studies. In the experiment reported here, a differentiation of morphologically similar spontaneous and induced mammary adenocarcinomas of the rat is achieved by gene expression profiling. By choosing one marker gene based on the gene expression profile for each tumour type, we were able to distinguish the tumours by real-time quantitative polymerase chain reaction (RT-QPCR) as well.