Rhabdomyosarcomas in aging A/J mice

Proteins implicated in muscular dystrophy and cancer are functional constituents of the centrosome

Aberrant expression of dystrophin, utrophin, dysferlin, or calpain-3 was originally identified in muscular dystrophies (MDs). Increasing evidence now indicates that these proteins might act as tumor suppressors in myogenic and non-myogenic cancers. As DNA damage and somatic aneuploidy, hallmarks of cancer, are early pathological signs in MDs, we hypothesized that a common pathway might involve the centrosome. Here, we show that dystrophin, utrophin, dysferlin, and calpain-3 are functional constituents of the centrosome. In myoblasts, lack of any of these proteins caused excess centrosomes, centrosome misorientation, nuclear abnormalities, and impaired microtubule nucleation. In dystrophin double-mutants, these defects were significantly aggravated. Moreover, we demonstrate that also in non-myogenic cells, all four MD-related proteins localize to the centrosome, including the muscle-specific full-length dystrophin isoform. Therefore, MD-related proteins might share a convergent function at the centrosome in addition to their diverse, well-established muscle-specific functions. Thus, our findings support the notion that cancer-like centrosome-related defects underlie MDs and establish a novel concept linking MDs to cancer.

Research-Relevant Conditions and Pathology of Laboratory Mice, Rats, Gerbils, Guinea Pigs, Hamsters, Naked Mole Rats, and Rabbits

Animals are valuable resources in biomedical research in investigations of biological processes, disease pathogenesis, therapeutic interventions, safety, toxicity, and carcinogenicity. Interpretation of data from animals requires knowledge not only of the processes or diseases (pathophysiology) under study but also recognition of spontaneous conditions and background lesions (pathology) that can influence or confound the study results. Species, strain/stock, sex, age, anatomy, physiology, spontaneous diseases (noninfectious and infectious), and neoplasia impact experimental results and interpretation as well as animal welfare. This review and the references selected aim to provide a pathology resource for researchers, pathologists, and veterinary personnel who strive to achieve research rigor and validity and must understand the spectrum of "normal" and expected conditions to accurately identify research-relevant experimental phenotypes as well as unusual illness, pathology, or other conditions that can compromise studies involving laboratory mice, rats, gerbils, guinea pigs, hamsters, naked mole rats, and rabbits.

Loss of p16/Ink4a drives high frequency of rhabdomyosarcoma in a rat model of Duchenne muscular dystrophy

Rhabdomyosarcoma (RMS) is an aggressive type of soft tissue sarcoma, and pleomorphic RMS is a rare subtype of RMS found in adult. p16 is a tumor suppressor which inhibits cell cycle. In human RMS, p16 gene is frequently deleted, but p16-null mice do not develop RMS. We reported that genetic ablation of p16 by the crossbreeding of p16 knock-out rats (p16-KO rats) improved the dystrophic phenotype of a rat model of Duchenne muscular dystrophy (Dmd-KO rats). However, p16/Dmd double knock-out rats (dKO rats) unexpectedly developed sarcoma. In the present study, we raised p16-KO, Dmd-KO, and dKO rats until 11 months of age. Twelve out of 22 dKO rats developed pleomorphic RMS after 9 months of age, while none of p16-KO rats and Dmd-KO rats developed tumor. The neoplasms were connected to skeletal muscle tissue with indistinct borders and characterized by diffuse proliferation of pleomorphic cells which had eosinophilic cytoplasm and atypical nuclei with anisokaryosis. For almost all cases, the tumor cells immunohistochemically expressed myogenic markers including desmin, MyoD, and myogenin. The single cell cloning from tumor primary cells gained 20 individual Pax7-negative MyoD-positive RMS cell clones. Our results demonstrated that double knock-out of p16 and dystrophin in rats leads to the development of pleomorphic RMS, providing an animal model that may be useful to study the developmental mechanism of pleomorphic RMS.

Reduced Chronic Toxicity and Carcinogenicity in A/J Mice in Response to Life-Time Exposure to Aerosol From a Heated Tobacco Product Compared With Cigarette Smoke

We conducted an inhalation study, in accordance with Organisation for Economic Co-operation and Development Test Guideline 453, exposing A/J mice to tobacco heating system (THS) 2.2 aerosol or 3R4F reference cigarette smoke (CS) for up to 18 months to evaluate chronic toxicity and carcinogenicity. All exposed mice showed lower thymus and spleen weight, blood lymphocyte counts, and serum lipid concentrations than sham mice, most likely because of stress and/or nicotine effects. Unlike THS 2.2 aerosol-exposed mice, CS-exposed mice showed increased heart weight, changes in red blood cell profiles and serum liver function parameters. Similarly, increased pulmonary inflammation, altered lung function, and emphysematous changes were observed only in CS-exposed mice. Histopathological changes in other respiratory tract organs were significantly lower in the THS 2.2 aerosol-exposed groups than in the CS-exposed group. Chronic exposure to THS 2.2 aerosol also did not increase the incidence or multiplicity of bronchioloalveolar adenomas or carcinomas relative to sham, whereas CS exposure did. Male THS 2.2 aerosol-exposed mice had a lower survival rate than sham mice, related to an increased incidence of urogenital issues that appears to be related to congenital factors rather than test item exposure. The lower impact of THS 2.2 aerosol exposure on tumor development and chronic toxicity is consistent with the significantly reduced levels of harmful and potentially harmful constituents in THS 2.2 aerosol relative to CS. The totality of the evidence from this study further supports the risk reduction potential of THS 2.2 for lung diseases in comparison with cigarettes.

Functions of Vertebrate Ferlins

Ferlins are multiple-C2-domain proteins involved in Ca²⁺-triggered membrane dynamics within the secretory, endocytic and lysosomal pathways. In bony vertebrates there are six ferlin genes encoding, in humans, dysferlin, otoferlin, myoferlin, Fer1L5 and 6 and the long noncoding RNA Fer1L4. Mutations in DYSF (dysferlin) can cause a range of muscle diseases with various clinical manifestations collectively known as dysferlinopathies, including limb-girdle muscular dystrophy type 2B (LGMD2B) and Miyoshi myopathy. A mutation in MYOF (myoferlin) was linked to a muscular dystrophy accompanied by cardiomyopathy. Mutations in OTOF (otoferlin) can be the cause of nonsyndromic deafness DFNB9. Dysregulated expression of any human ferlin may be associated with development of cancer. This review provides a detailed description of functions of the vertebrate ferlins with a focus on muscle ferlins and discusses the mechanisms leading to disease development.

Differential Expression of KCNJ12 Gene and Association Analysis of Its Missense Mutation with Growth Traits in Chinese Cattle

Simple Summary

A central goal of livestock genomic study is to find causal genes underlying economic traits and identify effective variations which can be used as molecular markers for livestock breeding. The cattle KCNJ12 gene is an important candidate gene. To date, however, there have been no reports about the use of its missense mutation as a marker in cattle stature. In this study, missense mutation in KCNJ12 was firstly verified, which led to a change in its protein sequence. Further, a significant association was detected between the mutation of KCNJ12 and cattle stature, and we determined that the mutation in KCNJ12 could be used as a molecular marker in beef breeding programs. In addition, expression analysis of the KCNJ12 gene revealed high abundance in muscle and potential roles in bovine myocyte differentiation, which may be the subject of our future research.

Abstract

The potassium inwardly rectifying channel, subfamily J, member 12 (KCNJ12) gene is a promising candidate for economic traits because of its crucial roles in myoblast development. Here, a missense mutation (Cys > Arg) was first detected to be located in exon 3 of KCNJ12 from three Chinese cattle breeds by DNA-pool sequencing. Then, we performed an association analysis of this single-nucleotide polymorphism (SNP) with stature in three Chinese cattle populations (n = 820). A significantly positive correlation was revealed by a reduced animal general linear model and the CC genotype was the most favorable in three breeds. Further, we measured the expression profile of the KCNJ12 gene in various cattle tissues and primary bovine skeletal muscle cells. Ubiquitous expression with high abundance in muscle was observed. Further, in primary bovine skeletal muscle cells, the KCNJ12 mRNA expression was gradually up-regulated in differentiation medium (DM) compared with that in growth medium (GM), suggesting that the KCNJ12 gene is involved in bovine myocyte differentiation. Conclusively, the KCNJ12 gene is a functional candidate gene which can be used as a molecular marker for cattle breeding.

Hip region muscular dystrophy and emergence of motor deficits in dysferlin-deficient Bla/J mice

The identification of a dysferlin‐deficient animal model that accurately displays both the physiological and behavior aspects of human dysferlinopathy is critical for the evaluation of potential therapeutics. Disease progression in dysferlin‐deficient mice is relatively mild, compared to the debilitating human disease which manifests in impairment of particular motor functions. Since there are no other known models of dysferlinopathy in other species, locomotor proficiency and muscular anatomy through MRI (both lower leg and hip region) were evaluated in dysferlin‐deficient B6.A‐Dysf^prmd/GeneJ (Bla/J) mice to define disease parameters for therapeutic assessment. Despite the early and progressive gluteal muscle dystrophy and significant fatty acid accumulation, the emergence of significant motor function deficits was apparent at approximately 1 year of age for standard motor challenges including the rotarod, a marble bury test, grip strength, and swimming speed. Earlier observations of decreased performance for Bla/J mice were evident during extended monitoring of overall exploration and rearing activity. Comprehensive treadmill gait analyses of the Bla/J model indicated significant differences in paw placement angles and stance in relation to speed and platform slope. At 18 months of age, there was no significant difference in the life expectancy of Bla/J mice compared to wild type. Consistent with progressive volume loss and fatty acid accumulation in the hip region observed by MRI, mass measurement of individual muscles confirmed gluteal and psoas muscles were the only muscles demonstrating a significant decrease in muscle mass, which is analogous to hip‐girdle weakness observed in human dysferlin‐deficient patients. Collectively, this longitudinal analysis identifies consistent disease parameters that can be indicators of efficacy in studies developing treatments for human dysferlin deficiency.

Immunohistochemical Characterization of Sarcomas in Trp53+/- Haploinsufficient Mice

The use of immunohistochemical (IHC) staining in determining and/or confirming the cellular origin of poorly differentiated sarcomas was evaluated in this study. Sarcomatous neoplasms were evaluated in a research study conducted in 2 strains of p53+/- haploinsufficient mice. The most common neoplasms were undifferentiated sarcomas, followed by osteosarcomas and rhabdomyosarcomas (RMSs). The RMSs were poorly differentiated and appeared similar to the pleomorphic, or adult type, RMS of humans. All sarcomas stained positive by IHC for the mesenchymal cell intermediate filament vimentin. The RMSs were identified by positive IHC staining for myogenin, a transcription factor specific to skeletal muscle. Osteosarcomas were easily identifiable on hematoxylin and eosin-stained slides; no generally accepted IHC stain specific for bone is presently available. Some of the undifferentiated sarcomas contained numerous macrophages that stained positive for F4/80, a macrophage marker; the positive-staining cells were considered to be infiltrating macrophages. One-third of the neoplasms observed in this study were associated with subcutaneous implanted electronic microchips used for animal identification. Based upon histopathologic evaluation and IHC staining, it was not possible to distinguish neoplasms associated with subcutaneous microchips from neoplasms not associated with microchips.

Approaches to Investigating Complex Genetic Traits in a Large-Scale Inbred Mouse Aging Study

Inbred mice are a unique model system for studying aging because of the genetic homogeneity within inbred strains, the short life span of mice relative to humans, and the rich array of analytic tools that are available. A large-scale aging study was conducted on 28 inbred strains representing great genetic diversity to determine, via histopathology, the type and diversity of spontaneous diseases that aging mice develop. A total of 20 885 different diagnoses were made, with an average of 12 diagnoses per mouse in the study. Eighteen inbred strains have had their genomes sequenced, and many others have been partially sequenced to provide large repositories of data on genetic variation among the strains. This vast amount of genomic information can be utilized in genome-wide association studies to find candidate genes that are involved in the pathogenesis of spontaneous diseases. As an illustration, this article presents a genome-wide association study of the genetic associations of age-related intestinal amyloidosis, which implicated 3 candidate genes: translocating chain-associated membrane protein 1 (Tram1); splicing factor 3b, subunit 5 (Sf3b5); and syntaxin 11 (Stx11). Representative photomicrographs are available on the Mouse Tumor Biology Database and Pathbase to serve as a reference when evaluating inbred mice used in other genetic or experimental studies to rule out strain background lesions. Many of the age-related mouse diseases are similar, if not identical, to human diseases; therefore, the genetic discoveries have direct translational benefit.

A Patient-Derived Xenograft Model of Parameningeal Embryonal Rhabdomyosarcoma for Preclinical Studies

Embryonal rhabdomyosarcoma (eRMS) is one of the most common soft tissue sarcomas in children and adolescents. Parameningeal eRMS is a variant that is often more difficult to treat than eRMS occurring at other sites. A 14-year-old female with persistent headaches and rapid weight loss was diagnosed with parameningeal eRMS. She progressed and died despite chemotherapy with vincristine, actinomycin-D, and cyclophosphamide plus 50.4 Gy radiation therapy to the primary tumor site. Tumor specimens were acquired by rapid autopsy and tumor tissue was transplanted into immunodeficient mice to create a patient-derived xenograft (PDX) animal model. As autopsy specimens had an ALK R1181C mutation, PDX tumor bearing animals were treated with the pan-kinase inhibitor lestaurtinib but demonstrated no decrease in tumor growth, suggesting that single agent kinase inhibitor therapy may be insufficient in similar cases. This unique parameningeal eRMS PDX model is publicly available for preclinical study.

Nicotine: Carcinogenicity and Effects on Response to Cancer Treatment - A Review

Tobacco use is considered the single most important man-made cause of cancer that can be avoided. The evidence that nicotine is involved in cancer development is reviewed and discussed in this paper. Both tobacco smoke and tobacco products for oral use contain a number of carcinogenic substances, such as polycyclic hydrocarbons and tobacco-specific N-nitrosamines (TSNA), which undoubtedly contribute to tobacco related cancer. Recent studies have shown that nicotine can affect several important steps in the development of cancer, and suggest that it may cause aggravation and recurrence of the disease. TSNA may be formed from nicotine in the body. The role of nicotine as the major addictive component of tobacco products may have distracted our attention from toxicological effects on cell growth, angiogenesis, and tumor malignancy. Effects on cancer disease are important aspects in the evaluation of possible long-term effects from sources of nicotine, such as e-cigarettes and products for nicotine replacement therapy, which both have a potential for life-long use.

Probing for a deeper understanding of rhabdomyosarcoma: insights from complementary model systems

Rhabdomyosarcoma (RMS) is a mesenchymal malignancy composed of neoplastic primitive precursor cells that exhibit histological features of myogenic differentiation. Despite intensive conventional multimodal therapy, patients with high-risk RMS typically suffer from aggressive disease. The lack of directed therapies against RMS emphasizes the need to further uncover the molecular underpinnings of the disease. In this Review, we discuss the notable advances in the model systems now available to probe for new RMS-targetable pathogenetic mechanisms, and the possibilities for enhanced RMS therapeutics and improved clinical outcomes.

Immune status, strain background, and anatomic site of inoculation affect mouse papillomavirus (MmuPV1) induction of exophytic papillomas or endophytic trichoblastomas

Papillomaviruses (PVs) induce papillomas, premalignant lesions, and carcinomas in a wide variety of species. PVs are classified first based on their host and tissue tropism and then their genomic diversities. A laboratory mouse papillomavirus, MmuPV1 (formerly MusPV), was horizontally transmitted within an inbred colony of NMRI-Foxn1(nu)/Foxn1nu (nude; T cell deficient) mice of an unknown period of time. A ground-up, filtered papilloma inoculum was not capable of infecting C57BL/6J wild-type mice; however, immunocompetent, alopecic, S/RV/Cri-ba/ba (bare) mice developed small papillomas at injection sites that regressed. NMRI-Foxn1(nu) and B6.Cg-Foxn1(nu), but not NU/J-Foxn1(nu), mice were susceptible to MmuPV1 infection. B6 congenic strains, but not other congenic strains carrying the same allelic mutations, lacking B- and T-cells, but not B-cells alone, were susceptible to infection, indicating that mouse strain and T-cell deficiency are critical to tumor formation. Lesions initially observed were exophytic papillomas around the muzzle, exophytic papillomas on the tail, and condylomas of the vaginal lining which could be induced by separate scarification or simultaneous scarification of MmuPV1 at all four sites. On the dorsal skin, locally invasive, poorly differentiated tumors developed with features similar to human trichoblastomas. Transcriptome analysis revealed significant differences between the normal skin in these anatomic sites and in papillomas versus trichoblastomas. The primarily dysregulated genes involved molecular pathways associated with cancer, cellular development, cellular growth and proliferation, cell morphology, and connective tissue development and function. Although trichoepitheliomas are benign, aggressive tumors, few of the genes commonly associated with basal cell carcinoma or squamous cells carcinoma were highly dysregulated.

Connections of nicotine to cancer

This Opinion article discusses emerging evidence of direct contributions of nicotine to cancer onset and growth. The list of cancers reportedly connected to nicotine is expanding and presently includes small-cell and non-small-cell lung carcinomas, as well as head and neck, gastric, pancreatic, gallbladder, liver, colon, breast, cervical, urinary bladder and kidney cancers. The mutagenic and tumour-promoting activities of nicotine may result from its ability to damage the genome, disrupt cellular metabolic processes, and facilitate growth and spreading of transformed cells. The nicotinic acetylcholine receptors (nAChRs), which are activated by nicotine, can activate several signalling pathways that can have tumorigenic effects, and these receptors might be able to be targeted for cancer therapy or prevention. There is also growing evidence that the unique genetic makeup of an individual, such as polymorphisms in genes encoding nAChR subunits, might influence the susceptibility of that individual to the pathobiological effects of nicotine. The emerging knowledge about the carcinogenic mechanisms of nicotine action should be considered during the evaluation of regulations on nicotine product manufacturing, distribution and marketing.

Muscular dystrophies share pathogenetic mechanisms with muscle sarcomas

Several lines of recent evidence have opened a new debate on the mechanisms underlying the genesis of rhabdomyosarcoma, a pediatric soft tissue tumor with a widespread expression of muscle-specific markers. In particular, it is increasingly evident that the loss of skeletal muscle integrity observed in some mouse models of muscular dystrophy can favor rhabdomyosarcoma formation. This is especially true in old age. Here, we review these experimental findings and focus on the main molecular and cellular events that can dictate the tumorigenic process in dystrophic muscle, such as the loss of structural or regulatory proteins with tumor suppressor activity, the impaired DNA damage response due to oxidative stress, the chronic inflammation and the conflicting signals arising within the degenerated muscle niche.

Rhabdomyosarcomas: an overview on the experimental animal models

Rhabdomyosarcomas (RMS) are aggressive childhood soft-tissue malignancies deriving from mesenchymal progenitors that are committed to muscle-specific lineages. Despite the histopathological signatures associated with three main histological variants, termed embryonal, alveolar and pleomorphic, a plethora of genetic and molecular changes are recognized in RMS. Over the years, exposure to carcinogens or ionizing radiations and gene-targeting approaches in vivo have greatly contributed to disclose some of the mechanisms underlying RMS onset. In this review, we describe the principal distinct features associated with RMS variants and focus on the current available experimental animal models to point out the molecular determinants cooperating with RMS development and progression.

Dystrophin and dysferlin double mutant mice: a novel model for rhabdomyosarcoma

Although researchers have yet to establish a link between muscular dystrophy (MD) and sarcomas in human patients, literature suggests that the MD genes dystrophin and dysferlin act as tumor suppressor genes in mouse models of MD. For instance, dystrophin-deficient mdx and dysferlin-deficient A/J mice, models of human Duchenne MD and limb-girdle MD type 2B, respectively, develop mixed sarcomas with variable penetrance and latency. To further establish the correlation between MD and sarcoma development, and to test whether a combined deletion of dystrophin and dysferlin exacerbates MD and augments the incidence of sarcomas, we generated dystrophin and dysferlin double mutant mice (STOCK-Dysf(prmd)Dmd(mdx-5Cv)). Not surprisingly, the double mutant mice develop severe MD symptoms and, moreover, develop rhabdomyosarcoma (RMS) at an average age of 12 months, with an incidence of >90%. Histological and immunohistochemical analyses, using a panel of antibodies against skeletal muscle cell proteins, electron microscopy, cytogenetics, and molecular analysis reveal that the double mutant mice develop RMS. The present finding bolsters the correlation between MD and sarcomas, and provides a model not only to examine the cellular origins but also to identify mechanisms and signal transduction pathways triggering development of RMS.

Prognostic Impact of del(17p) and del(22q) as assessed by interphase FISH in sporadic colorectal carcinomas

Background

Most sporadic colorectal cancer (sCRC) deaths are caused by metastatic dissemination of the primary tumor. New advances in genetic profiling of sCRC suggest that the primary tumor may contain a cell population with metastatic potential. Here we compare the cytogenetic profile of primary tumors from liver metastatic versus non-metastatic sCRC.

Methodology/Principal Findings

We prospectively analyzed the frequency of numerical/structural abnormalities of chromosomes 1, 7, 8, 13, 14, 17, 18, 20, and 22 by iFISH in 58 sCRC patients: thirty-one non-metastatic (54%) vs. 27 metastatic (46%) disease. From a total of 18 probes, significant differences emerged only for the 17p11.2 and 22q11.2 chromosomal regions. Patients with liver metastatic sCRC showed an increased frequency of del(17p11.2) (10% vs. 67%;p<.001) and del(22q11.2) (0% vs. 22%;p = .02) versusnon-metastatic cases. Multivariate analysis of prognostic factors for overall survival (OS) showed that the only clinical and cytogenetic parameters that had an independent adverse impact on patient outcome were the presence of del(17p) with a 17p11.2 breakpoint and del(22q11.2). Based on these two cytogenetic variables, patients were classified into three groups: low- (no adverse features), intermediate- (one adverse feature) and high-risk (two adverse features)- with significantly different OS rates at 5-years (p<.001): 92%, 53% and 0%, respectively.

Conclusions/Significance

Our results unravel the potential implication of del(17p11.2) in sCRC patients with liver metastasis as this cytogenetic alteration appears to be intrinsically related to an increased metastatic potential and a poor outcome, providing additional prognostic information to that associated with other cytogenetic alterations such as del(22q11.2). Additional prospective studies in larger series of patients would be required to confirm the clinical utility of the new prognostic markers identified.