Carcinogenicity assessment: technical and political challenges

The rising rates of cancer incidence and prevalence identified by the WHO are of serious concern. The scientific advances of the past twenty years have helped to describe major properties of the cancer disease, enabling therapies that are more sophisticated. It has become clear that the management of relevant risk factors can also significantly reduce cancer occurrence worldwide. Public health policy actions cannot be decoupled from environmental policy actions, since exposure to chemicals through air, soil, water and food can contribute to cancer as well as other chronic diseases. Furthermore, due to the increasing global trend of chemical production including novel compounds, chemical exposure patterns are foreseen to change, posing high demands on chemical safety assessment, and creating potential protection gaps. The safety assessment of carcinogenicity needs to evolve to keep pace with changes in the chemical environment and cancer epidemiology. The presentation focusses on EC-JRC recommendations and future strategies for carcinogenicity safety assessment. This also includes discussion on how the traditional data streams of regulatory toxicology, together with new available assessment methods can inform, along with indicators of public health status based on biomonitoring and clinical data, a more holistic human-relevant and impactful approach to carcinogenicity assessment and overall prevention of cancer disease.

Epidemiology of ocular disorders presumed to be inherited in three small Italian dog breeds in Italy

OBJECTIVE

To describe the prevalence and the types of eye disorders that are known or presumed to be inherited (KP-HED) in three small Italian dog breeds.

ANIMALS

Three small Italian dog breeds: Maltese, Bolognese, and Italian Greyhound.

PROCEDURES

All dogs of the breeds selected for this prospective observational study that underwent a complete ophthalmic examination between 1994 and 2015 were included. General and proportional KP-HED prevalence with 95% confidence intervals were reported.

RESULTS

Three hundred and six of 462 dogs were affected by at least one KP-HED (66.2%; 95% CI: 61.8%-70.4%). In the entire population, the five most common KP-HED were cataract (n = 122; rate on the total number of KP-HED: 31.4%), entropion (n = 56; 14.4%), keratoconjunctivitis sicca (n = 33; 8.5%), retinal dysplasia (n = 24; 6.2%), and persistent pupillary membrane (iris to iris) (n = 21; 5.4%). The most common KP-HED in each breed were cataracts in the Maltese (35.1%) and in the Bolognese (24.2%), and presentation of vitreous in the anterior chamber in the Italian Greyhound (46.7%).

CONCLUSIONS

Clinicians should be aware of KP-HED that commonly affect three small Italian dog breeds. Breed standards should be reconsidered, and breeding programs should be directed at limiting such disorders.

Epidemiology of ocular disorders presumed to be inherited in three large Italian dog breeds in Italy

OBJECTIVE

To describe the epidemiology and the types of eye disorders that are presumed to be inherited (PIED) in three large Italian dog breeds.

ANIMALS

Three large Italian dog breeds: Neapolitan Mastiff (FCI code: 197), Maremma Sheepdog (FCI code: 201), and Italian Corso dog (FCI code: 343).

PROCEDURES

All dogs that underwent a complete ophthalmic examination between 1992 and 2012 were included in this prospective observational study. The prevalence of eye disorders with 95% confidence intervals was reported for presumed healthy dogs and for dogs referred to a veterinary center for an ophthalmic consultation. Univariate and multivariate logistic regression techniques were used to generate odds ratios.

RESULTS

Of 605 dogs examined during the study period, 351 dogs were affected by at least one PIED (58%; 95% CI: 54-62%). The prevalence of PIED was significantly lower in dogs presented for ophthalmic examination (53.8%) as compared to presumed healthy dogs (62.2%)(OR: 1.4; 95% CI: 1.02-1.9; P = 0.037). Also after multivariate adjustment for the period of observation, the odds of Neapolitan Mastiff (92.1%; OR: 21.4; 95% CI: 11.1-41.4) and of Cane Corso (57.7%; OR: 2.5; 95% CI: 1.7-3.6) suffering a PIED were greater than the Maremma Sheepdog (35.4%). The most common PIED in each breed were entropion (24.3% of all the PIED) in the Neapolitan Mastiff, ectropion (36.6%) in the Corso dog, and cataract (27.9%) in the Maremma Sheepdog.

CONCLUSIONS

Clinicians should be aware that three large Italian dog breeds frequently suffer PIED. Breed standards should be reconsidered, and breeding programs should be directed at limiting such disorders.

The combined use of surgical debulking and diode laser photocoagulation for limbal melanoma treatment: a retrospective study of 21 dogs

OBJECTIVE

To evaluate effectiveness and safety of debulking and diode laser photocoagulation (DPC) for the treatment of limbal melanoma (LM).

PROCEDURE

Retrospective multi-institutional case series. Medical records of animals diagnosed with LM at the Centro Veterinario Specialistico (CVS) and at the Long Island Veterinary Specialists from 1994 to 2014 were retrieved. Signalment, location, extent of tumors, recurrence rate, and early and late complications were reported. Patient follow-up information was obtained from veterinary ophthalmologists, primary care veterinarians, and where appropriate, owners.

RESULTS

Twenty-one eyes of 21 dogs (13 females and 8 males) were included in this study. The dogs' average age was 6 years (range: 7 months-11 years). The follow-up period ranged from 1-108 months (median 48 months) after the last DPC procedure. Long-term follow-up was obtained by telephone interviews in 6 of 20 cases and by clinical re-evaluations in 14 of 20 cases. The most common early complications were a moderate anterior uveitis and peripheral corneal edema (21/21 eyes). Late complications included corneal fibrosis and/or pigmentation (20/21). In one case, a severe bullous keratopathy associated with extensive corneal fibrosis was observed (1/21). One case was blind due to concurrent Sudden Acquired Retinal Degeneration (SARD). However, after surgery 2 of 20 eyes lost vision and one of these was enucleated.

CONCLUSIONS

Debulking, in addition to diode laser photocoagulation, was technically straightforward to perform, minimally invasive, well tolerated, and highly successful in this case series.

Inter-laboratory study of human in vitro toxicogenomics-based tests as alternative methods for evaluating chemical carcinogenicity: a bioinformatics perspective

The assessment of the carcinogenic potential of chemicals with alternative, human-based in vitro systems has become a major goal of toxicogenomics. The central read-out of these assays is the transcriptome, and while many studies exist that explored the gene expression responses of such systems, reports on robustness and reproducibility, when testing them independently in different laboratories, are still uncommon. Furthermore, there is limited knowledge about variability induced by the data analysis protocols. We have conducted an inter-laboratory study for testing chemical carcinogenicity evaluating two human in vitro assays: hepatoma-derived cells and hTERT-immortalized renal proximal tubule epithelial cells, representing liver and kidney as major target organs. Cellular systems were initially challenged with thirty compounds, genome-wide gene expression was measured with microarrays, and hazard classifiers were built from this training set. Subsequently, each system was independently established in three different laboratories, and gene expression measurements were conducted using anonymized compounds. Data analysis was performed independently by two separate groups applying different protocols for the assessment of inter-laboratory reproducibility and for the prediction of carcinogenic hazard. As a result, both workflows came to very similar conclusions with respect to (1) identification of experimental outliers, (2) overall assessment of robustness and inter-laboratory reproducibility and (3) re-classification of the unknown compounds to the respective toxicity classes. In summary, the developed bioinformatics workflows deliver accurate measures for inter-laboratory comparison studies, and the study can be used as guidance for validation of future carcinogenicity assays in order to implement testing of human in vitro alternatives to animal testing.

Monitoring of teratogenic effects in vitro by analysing a selected gene expression pattern

The development of in vitro methods for regulatory embryotoxicity testing is challenging since the understanding of chemical effects on the mammalian development is still poor. The aim of the project is to identify marker genes during in vitro cell differentiation of murine embryonic stem cells, in order to predict chemical effects on cell differentiation of specific target tissues. The present study is focusing on the expression pattern by using semi-quantitative reverse transcriptase (RT)-PCR of key genes involved in cardiomyocytes development; i.e. Oct-4, Brachyury, Nkx2.5 and alpha myosin heavy chain (alpha-MHC). Two reference chemicals with well-known in vivo data have been analysed by using this approach: retinoic acid and lithium chloride. Retinoic acid has been selected as a teratogen affecting several target tissues, whereas lithium chloride has been described to affect the development of the cardiovascular system. We demonstrate that retinoic acid already affects in the early stage of germ layer formation, which was demonstrated by a change of Oct-4 and Brachyury gene expression. As we expected, the expression of cardiac specific genes (Nkx2.5, alpha-MHC) has been also modified. In contrary, the Oct-4 and Brachyury expression was not changed by lithium treatment. In this case, we observed a modification in the normal gene expression pattern, for alpha-MHC and Nkx2.5, demonstrating that lithium chloride affects the later stage of heart development. These data suggest that the inclusion of selective target organ genes in an established embryotoxicity test allows to predict effects of chemicals and drugs to the heart development.

Frequent RET rearrangements in thyroid papillary microcarcinoma detected by interphase fluorescence in situ hybridization

Papillary thyroid microcarcinomas (measuring 1 cm or less in diameter) are very common thyroid tumors, which are present in 10% to 35% of post-mortem histopathological examinations of individuals whose death was due to a cause other than thyroid cancer. The molecular basis of this tumor is still poorly understood. Somatic mutations are better characterized in clinically evident papillary thyroid carcinomas (PTCs), the most common involving the proto-oncogene RET, which maps to 10q11.2. Molecular alterations of RET always lead to intra- or interchromosomal rearrangements. In this study we have investigated the status of RET in 21 microcarcinomas, by means of interphase fluorescence in situ hybridization (FISH). RET was rearranged in 52% of microcarcinomas, a statistically significant higher frequency than that found previously in clinically evident PTCs using the same technique. Moreover, interphase FISH allowed us to detect a putative novel type of rearrangement in a microcarcinoma, and we observed trisomies of chromosome 10 and other chromosomes in two adenomas surrounding two of the microcarcinomas. The strikingly high frequency of RET rearrangements in microcarcinomas strongly suggests that RET plays a role in the initiation of thyroid tumorigenesis but does not seem to be necessary for the further progression of the tumor.

RET rearrangements in familial papillary thyroid carcinomas

Familial papillary thyroid carcinoma (FPTC) is an inherited tumor characterized by a more aggressive phenotype than that of its sporadic counterpart. Its mode of inheritance as well as its genetic and molecular bases are still poorly understood. On the contrary, genetic alterations in sporadic papillary thyroid carcinoma (PTC) are better characterized, the most common one involving the activation of the proto-oncogene RET through somatic rearrangements. In the present study, we investigated by interphase fluorescence in situ hybridization the presence of RET rearrangements in a series of 20 FPTC. We show that one FPTC and the adenoma from the same patient carry a RET rearrangement (type PTC1) and that this rearrangement is absent in the germline. Furthermore, we excluded a RET haplotype sharing in two brothers of the same family. These results show that RET rearrangements can indeed be found in FPTC and confirm that RET is not involved in the inherited predisposition to FPTC.

RET/PCM-1: a novel fusion gene in papillary thyroid carcinoma

The RET proto-oncogene is often activated through somatic rearrangements in papillary thyroid carcinomas (PTCs). Three main rearranged forms of RET have been described: RET/PTC1 and RET/PTC3, which arise from a paracentric inversion and RET/PTC2, which originates from a 10 : 17 translocation. We previously developed a dual-color FISH test to detect these RET rearrangements in interphase nuclei of thyroid lesions. This approach allowed us to detect a novel translocation involving the RET region, which was not detectable by RT - PCR with specific primers for known rearrangements. A combination of RT - PCR and RACE analyses finally led to the identification of the fusion gene, which involves the 5' portion of PCM-1, a gene coding for a centrosomal protein with distinct cell cycle distribution, and the RET tyrosine kinase (TK) domain. FISH analysis confirmed the chromosomal localization of PCM-1 on chromosome 8p21-22, a region commonly deleted in several tumors. Immunohistochemistry, using an antibody specific for the C-terminal portion of PCM-1 showed that the protein level is drastically decreased and its subcellular localization is altered in thyroid tumor tissue with respect to normal thyroid. However, heterozygosity is retained for seven microsatellite markers in the 8p21-22 region, suggesting that the non-rearranged PCM-1 allele is not lost and that the translocation is balanced. Oncogene (2000) 19, 4236 - 4242

RET rearrangements in papillary thyroid carcinomas and adenomas detected by interphase FISH

Activation of the RET protooncogene through somatic rearrangements represents the most common genetic alteration in papillary thyroid carcinoma (PTC). Three main rearranged forms of RET have been described: RET/PTC1 and RET/PTC3, which arise from a paracentric inversion of the long arm of chromosome 10, and RET/PTC2, which originates from a 10;17 translocation. We have developed a dual-color FISH approach to detect RET/PTC rearrangements in interphase nuclei of thyroid lesions. By using a pool of three cosmids encompassing the RET chromosome region and a chromosome 10 centromeric probe, we could discriminate between the presence of an inversion (RET/PTC1 and RET/PTC3) or a translocation (RET/PTC2). We have investigated a series of thyroid tissue samples from Italian and French patients corresponding to a total of 69 PTCs and 22 benign lesions. Among PTCs, 13 (18.8%) showed a RET rearrangement, and 11 (15.9%) of these carried an inversion (RET/PTC1 or RET/PTC3) in more than 10% of the nuclei examined. Activated forms of RET were also observed in three adenomas. RT-PCR analysis on the same samples confirmed the presence and the type of rearrangement predicted using FISH analysis. An interesting difference in the frequency and type of RET rearrangements was detected between the Italian and the French patients. Furthermore, we identified a putative novel type of rearrangement in at least one PTC sample. Several PTCs carried a significant number of cells characterized by a trisomy or a tetrasomy of chromosome 10. Overall, the FISH approach in interphase nuclei represents a powerful tool for detecting, at the single cell level, RET/PTC rearrangements and other anomalies involving the RET chromosome region.

Identification and characterization of novel genes located at the t(1;15)(p36.2;q24) translocation breakpoint in the neuroblastoma cell line NGP

The distal portion of chromosome 1p is frequently deleted in several human cancers, suggesting the presence of one or more putative tumor suppressor genes on this chromosomal arm. In human neuroblastoma, a consistently deleted region at 1p36.1-p36.2 has been defined by comparison of molecular loss of heterozygosity (LOH) analyses. Recently we described the identification of a yeast artificial chromosome, YAC 927G4, that spans a translocation/duplication breakpoint within the minimally defined LOH region at 1p36.1-p36.2 in the neuroblastoma cell line NGP. Here we describe the identification of two overlapping P1 artificial chromosomes comprising 220 kb at the distal end of YAC 927G4, which we have used as hybridization probes under modified conditions to screen a composite, normalized cDNA library (IMAGE cDNA library). Hybridization screening resulted in the rapid and comprehensive identification of partial cDNAs of which a portion comprised two novel candidate genes, termed DNB1/ARPh and DNB5, which encode putative proteins of 1011 and 447 amino acids, respectively. The DNB1/ARPh gene, which was found to be ubiquitously expressed in human adult and fetal tissues, is highly related to the DRPLA gene, in which expansion of a CAG triplet appears to be causal in the dentatorubral and pallidolysian atrophy disease phenotype. The DNB5 sequence, in contrast, which is predominantly expressed in brain tissues and fetal kidney, failed to show any similarity to sequences in the public domain. A preliminary assessment of transcription and sequence of both genes in several neuroblastoma cell lines does not, thus far, support a causal role in neuroblastoma. However, further analyses are required to confirm these results.

New genetic loci in neuroblastoma

Neuroblastoma has been associated genetically with amplification of the MYCN gene and with alteration of the short arm of chromosome 1 (1p). In pursuit of determining the spectrum of genetic loci damaged recurrently in neuroblastoma cells we have recently encountered two additional types of genomic abnormalities: i.) duplication of the MYCN gene on chromosome 2p24; and ii.) amplification of the gene MDM2. These alterations extend the spectrum of genetic lesions in neuroblastoma cells, although their incidence in primary tumor tissues has not been determined as yet.

Patterns of oncogene activation in human neuroblastoma cells

Human neuroblastoma is the most frequent solid tumor in children. Recent studies suggest that a multiplicity of genomic alterations contributes to neuroblastoma, the most frequent and well studied being deletion of the short arm of chromosome 1 and amplification of N-MYC. We here present and discuss different patterns of oncogene activation including, amplification of N-MYC, duplication of N-MYC and amplification of MDM2.

Duplication of N-MYC at its resident site 2p24 may be a mechanism of activation alternative to amplification in human neuroblastoma cells

Amplification of the human N-MYC proto-oncogene is frequently seen either in extrachromosomal double minutes or in homogeneously staining regions of aggressively growing neuroblastomas. N-MYC maps to chromosome 2 band p23-24, but homogeneously staining regions have never been observed at this band, suggesting transposition of N-MYC during amplification. Previous studies had suggested that in cells with amplified N-MYC the chromosomes 2 appear to be unaltered and to carry one apparently normal copy of N-MYC each. In contrast, the contribution of N-MYC to tumors which lack amplification has been unclear. We here show, by fluorescence in situ hybridization, that N-MYC is occasionally duplicated at its resident site in neuroblastoma cell lines previously thought to have a single copy gene. Additionally, we detected duplication in a neuroblastoma cell line carrying amplification. Our results raise the possibility that duplication may, in some neuroblastomas, either be a prelude to amplification or an alternative pathway by which N-MYC becomes activated.

A human homologue of the Drosophila tumour suppressor gene l(2)gl maps to 17p11.2-12 and codes for a cytoskeletal protein that associates with nonmuscle myosin II heavy chain

Inactivation of the tumour suppressor gene lethal(2) giant larvae (D-lgl) of Drosophila leads to malignant transformation of the presumptive adult optic centers in the larval brain and tumours of the imaginal discs. These malignancies result from the disorganization of a cytoskeletal network in which the D-LGL protein participates. Here we describe the isolation of a cDNA encoding the human homologue to the D-lgl gene designated as hugl. The hugl cDNA detects a locus spanning at least 25 kilobases (kb) in human chromosome band 17p11.2-12, which is centromeric to the p53 gene and recognizes a 4.5 kb RNA transcript. The hugl gene is expressed in brain, kidney and muscle but is barely seen in heart and placenta. Sequence analysis of the hugl cDNA demonstrates a long open reading frame, which has the potential to encode a protein of 1057 amino acids with a predicted molecular weight of 115 kDaltons (kD). To further substantiate and identify the HUGL protein, we have prepared polyclonal rabbit antibodies against synthetic peptides corresponding to the amino and carboxyl termini of the conceptual translation product of the hugl gene. The affinity-purified anti-HUGL antibodies recognize a single protein with an apparent molecular weight of approximately 115 kD. Similar to the Drosophila protein, HUGL is part of a cytoskeletal network and, is associated with nonmuscle myosin II heavy chain and a kinase that specifically phosphorylates HUGL at serine residues.

A reciprocal translocation (1;15) (36.2;q24) in a neuroblastoma cell line is accompanied by DNA duplication and may signal the site of a putative tumor suppressor-gene

Cytogenetic analyses and molecular deletion studies of human neuroblastomas have indicated the chromosomal bands 1p36.1-1p36.2 as a location of genetic information which may be involved in tumorigenesis. To define this putative neuroblastoma locus in more detail we have analysed cell lines with alterations of distal 1p. Here we show, by fluorescence in situ hybridization (FISH), that cell line NGP has a reciprocal 1;15 translocation. Loci D1S214/D1S96 could be shown to map telomeric/distal, D1S228 centromeric/proximal to the break. We have identified yeast artificial chromosomes (YACs) that cover the break and map to D1S160 and D1S244. This chromosomal position is within the smallest region of overlap (SRO) found in neuroblastoma tumors (Weith et al., 1989; Caron et al., 1993; Schleiermacher et al., 1994) and within the region of a constitutional interstitial deletion of a neuroblastoma patient (Biegel et al., 1993). Mapping studies with FISH revealed that the translocation is associated with duplication of DNA. It appears, as if the subchromosomal region we describe here is a good candidate for harboring the postulated neuroblastoma suppressor-gene.

Non-syntenic amplification of MDM2 and MYCN in human neuroblastoma

Amplification of the MYCN gene is a well documented genetic alteration of aggressively growing human neuroblastomas. Through cytogenetic studies we have identified neuroblastoma cell lines which, in addition to amplified MYCN, carry amplified DNA not harbouring MYCN. In situ hybridization of biotinylated total genomic DNA to metaphase chromosomes of normal human lymphocytes by reverse genomic hybridization revealed the amplified DNA to be derived from chromosome 12 band q13-14. Subsequent filter analyses showed a 20- to 40-fold amplification of the MDM2 gene, located at 12q13-14, both in three cell lines and in an original tumor, in addition to amplified MYCN. As the apparent consequence of amplification abundant MDM2 protein was present, a part of which was complexed with p53.

Reciprocal translocation at 1p36.2/D1S160 in a neuroblastoma cell line: isolation of a YAC clone at the break

Band 1p36.1-1p36.2 is frequently involved in chromosomal aberrations of neuroblastoma cells, and therefore thought to harbour genetic information which may be involved in tumorigenesis. To map this putative neuroblastoma locus, we screened neuroblastoma cell lines for reciprocal translocations at 1p36.1-2 which may signal the site of an affected gene. We identified a reciprocal 1;15 translocation in cell line NGP by fluorescence in situ hybridisation (FISH). As a strategy to clone the translocation breakpoint, we isolated yeast artificial chromosomes (YACs) specific for loci at 1p36. Screening of cell line NGP by FISH identified a YAC, 1050 kbp in size, which hybridised to both derivative 1;15 and 15;1 chromosomes. We conclude that this YAC, which maps to D1S160, covers the break. This chromosomal position is within the smallest region of overlap (SRO) found in neuroblastoma tumours and within the region of a constitutional interstitial deletion of a neuroblastoma patient. The YAC we describe here should serve as a DNA source for gene cloning approaches towards the isolation of candidates for the putative neuroblastoma suppressor gene.

Cytogenetic evolution of MYCN and MDM2 amplification in the neuroblastoma LS tumour and its cell line

Amplification of the MYCN gene is frequently seen either in extrachromosomal double minutes (DMs) or in homogeneously staining regions (HSRs) of aggressively growing neuroblastomas. Total genomic DNA from cell line LS, from early passages of the same line and from original tumour material was biotinylated and hybridised to metaphase chromosomes of normal human lymphocytes. The reverse genomic hybridisation revealed the amplified DNA to be derived both from chromosome 2p23-24, which is the position of MYCN, and from chromosome 12 band q13-14. The MDM2 gene, located at 12q13-14, was found amplified both in early and late passages of LS, in addition to amplified MYCN. Amplification units of MYCN and MDM2 appear first to develop within DMs, which then integrate into different chromosomes to develop to HSRs.

Translocation involving 1p and 17q is a recurrent genetic alteration of human neuroblastoma cells

Human neuroblastoma cells often are monosomic for the distal portion of 1p (1p36). We report that the deleted 1p material in cells of neuroblastoma lines is preferentially replaced by material from chromosome 17, resulting from an unbalanced 1;17 translocation. Chromosome 17 often acquires instability, followed by the integration of fragments into various marker chromosomes. As a consequence, 17q material can increase over 17p material. The nonrandom frequency of 1;17 translocations appears to indicate an as-yet-undefined contribution to neuroblastoma development.

MYCN is retained in single copy at chromosome 2 band p23-24 during amplification in human neuroblastoma cells

Amplification of the human N-myc protooncogene, MYCN, is frequently seen either in extrachromosomal double minutes or in homogeneously staining regions of aggressively growing neuroblastomas. MYCN maps to chromosome 2 band p23-24, but homogeneously staining regions have never been observed at this band, suggesting transposition of MYCN during amplification. We have employed fluorescence in situ hybridization to determine the status of MYCN at 2p23-24 in five human neuroblastoma cell lines. All five lines carried, in addition to amplified MYCN in homogeneously staining regions or double minutes, single-copy MYCN at the normal position. In one line there was coamplification of MYCN together with DNA of the host chromosome 12, to which MYCN had been transposed. Our results suggest a model of amplification where MYCN is retained at its original location. They further sustain the view that either the initial events of MYCN amplification or the further evolution of amplified MYCN copies follow mechanisms different from those leading to amplification of drug-resistance genes.