Comparative analysis of ras proto-oncogene mutations in selected mammalian tumors

Hotspot Exon 15 Mutations in BRAF Are Uncommon in Feline Tumours

BRAF is one of multiple RAF proteins responsible for the activation of the MAPK cell signalling cascade involved in cell growth, differentiation, and survival. A hotspot BRAFV600E mutation, in exon 15, was determined to be a driver in 100% hairy cell leukaemias, 50%-60% of human melanomas, 30%-50% of human thyroid carcinomas and 10%-20% of human colorectal carcinomas. The orthologous BRAFV595E mutation was seen in 67% and 80% of canine bladder transitional cell carcinomas and prostatic adenocarcinomas, respectively. Since veterinary and human cancers exploit similar pathways and BRAF is highly conserved across species, BRAF can be expected to be a driver in a feline cancer. Primers were developed to amplify exon 15 of feline BRAF. One hundred ninety-six feline tumours were analysed. Sanger sequencing of the 211 bp PCR amplicon was done. A BRAF mutation was found in one tumour, a cutaneous melanoma. The mutation was a BRAFV597E mutation, orthologous to the canine and human hotspot mutations. A common synonymous variant, BRAFT586T, was seen in 23% (47/196) of tumours. This variant was suspected to be a single nucleotide polymorphism. BRAF was not frequently mutated in common feline tumours or in tumour types that frequently harbour BRAF mutations in human and canine cancers. As is seen in canine cancer genomics, the mutational profile in feline tumours may not parallel the histologic equivalent in human oncology.

Cat Mammary Tumors: Genetic Models for the Human Counterpart

The records are not clear, but Man has been sheltering the cat inside his home for over 12,000 years. The close proximity of this companion animal, however, goes beyond sharing the same roof; it extends to the great similarity found at the cellular and molecular levels. Researchers have found a striking resemblance between subtypes of feline mammary tumors and their human counterparts that goes from the genes to the pathways involved in cancer initiation and progression. Spontaneous cat mammary pre-invasive intraepithelial lesions (hyperplasias and neoplasias) and malignant lesions seem to share a wide repertoire of molecular features with their human counterparts. In the present review, we tried to compile all the genetics aspects published (i.e., chromosomal alterations, critical cancer genes and their expression) regarding cat mammary tumors, which support the cat as a valuable alternative in vitro cell and animal model (i.e., cat mammary cell lines and the spontaneous tumors, respectively), but also to present a critical point of view of some of the issues that really need to be investigated in future research.

KRAS Mutations in Canine and Feline Pancreatic Acinar Cell Carcinoma

Companion animals may serve as valuable models for studying human cancers. Although KRAS is the most commonly mutated gene in human ductal pancreatic cancers (57%), with mutations frequently occurring at codons 12, 13 and 61, human pancreatic acinar cell carcinomas (ACCs) lack activating KRAS mutations. In the present study, 32 pancreatic ACC samples obtained from 14 dogs and 18 cats, including seven metastases, were analyzed for six common activating KRAS mutations located in codons 12 (n = 5) and 13 (n = 1) using Sequenom MassARRAY. No KRAS mutations were found, suggesting that, similar to human pancreatic ACC, KRAS mutations do not play a critical role in feline or canine pancreatic ACC. Due to the similarity of the clinical disease in dogs and cats to that of man, this study confirms that companion animals offer potential as a suitable model for investigating this rare subtype of pancreatic carcinoma.

Mutational Hotspot of TET2, IDH1, IDH2, SRSF2, SF3B1, KRAS, and NRAS from Human Systemic Mastocytosis Are Not Conserved in Canine Mast Cell Tumors

Introduction

Both canine cutaneous mast cell tumor (MCT) and human systemic mastocytosis (SM) are characterized by abnormal proliferation and accumulation of mast cells in tissues and, frequently, by the presence of activating mutations in the receptor tyrosine kinase V-Kit Hardy-Zuckerman 4 Feline Sarcoma Viral Oncogene Homolog (c-KIT), albeit at different incidence (>80% in SM and 10–30% in MCT). In the last few years, it has been discovered that additional mutations in other genes belonging to the methylation system, the splicing machinery and cell signaling, contribute, with c-KIT, to SM pathogenesis and/or phenotype. In the present study, the mutational profile of the Tet methylcytosine dioxygenase 2 (TET2), the isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2), the serine/arginine-rich splicing factor 2 (SRSF2), the splicing factor 3b subunit 1 (SF3B1), the Kirsten rat sarcoma viral oncogene homolog (KRAS) and the neuroblastoma RAS viral oncogene homolog (NRAS), commonly mutated in human myeloid malignancies and mastocytosis, was investigated in canine MCTs.

Methods

Using the Sanger sequencing method, a cohort of 75 DNA samples extracted from MCT biopsies already investigated for c-KIT mutations were screened for the “human-like” hot spot mutations of listed genes.

Results

No mutations were ever identified except for TET2 even if with low frequency (2.7%). In contrast to what is observed in human TET2 no frame-shift mutations were found in MCT samples.

Conclusion

Results obtained in this preliminary study are suggestive of a substantial difference between human SM and canine MCT if we consider some target genes known to be involved in the pathogenesis of human SM.

Perspectives in molecular imaging through translational research, human medicine, and veterinary medicine

The concept of molecular imaging has taken off over the past 15 years to the point of the renaming of the Society of Nuclear Medicine (Society of Nuclear Medicine and Molecular Imaging) and Journals (European Journal of Nuclear Medicine and Molecular Imaging) and offering of medical fellowships specific to this area of study. Molecular imaging has always been at the core of functional imaging related to nuclear medicine. Even before the phrase molecular imaging came into vogue, radionuclides and radiopharmaceuticals were developed that targeted select physiological processes, proteins, receptor analogs, antibody-antigen interactions, metabolites and specific metabolic pathways. In addition, with the advent of genomic imaging, targeted genomic therapy, and theranostics, a number of novel radiopharmaceuticals for the detection and therapy of specific tumor types based on unique biological and cellular properties of the tumor itself have been realized. However, molecular imaging and therapeutics as well as the concept of theranostics are yet to be fully realized. The purpose of this review article is to present an overview of the translational approaches to targeted molecular imaging with application to some naturally occurring animal models of human disease.

Oncolytic reovirus in canine mast cell tumor

The usage of reovirus has reached phase II and III clinical trials in human cancers. However, this is the first study to report the oncolytic effects of reovirus in veterinary oncology, focusing on canine mast cell tumor (MCT), the most common cutaneous tumor in dogs. As human and canine cancers share many similarities, we hypothesized that the oncolytic effects of reovirus can be exploited in canine cancers. The objective of this study was to determine the oncolytic effects of reovirus in canine MCT in vitro, in vivo and ex vivo. We demonstrated that MCT cell lines were highly susceptible to reovirus as indicated by marked cell death, high production of progeny virus and virus replication. Reovirus induced apoptosis in the canine MCT cell lines with no correlation to their Ras activation status. In vivo studies were conducted using unilateral and bilateral subcutaneous MCT xenograft models with a single intratumoral reovirus treatment and apparent reduction of tumor mass was exhibited. Furthermore, cell death was induced by reovirus in primary canine MCT samples in vitro. However, canine and murine bone marrow-derived mast cells (BMCMC) were also susceptible to reovirus. The combination of these results supports the potential value of reovirus as a therapy in canine MCT but warrants further investigation on the determinants of reovirus susceptibility.

RAS, FLT3, and C-KIT mutations in immunophenotyped canine leukemias

OBJECTIVE

To determine the frequency of FLT3, C-KIT, and RAS mutations in canine leukemia patients.

MATERIALS AND METHODS

Ethylenediamine tetra-acetic acid blood samples were recruited from dogs with suspected leukemia, categorized by quantitative and cytological evaluation and immunophenotyping. Flow cytometry was carried out using antibodies against CD3; CD3e; CD4; CD5; CD8; CD11a, b, c, and d; CD14; CD21; CD34; CD45 and 45RA; CD79a; CD90 (THY-1); major histocompatibility complex II; myeloperoxidase; MAC387; and neutrophil-specific antibody. Genomic DNA was extracted from whole blood and analyzed for mutations in N, H, and K-RAS, FLT3, and C-KIT genes by polymerase chain reaction and sequencing.

RESULTS

Fifty-seven (77.0%) of 74 samples submitted from dogs with suspected leukemia had cytologically and immunophenotypically confirmed leukemia. There were 36 (63.2%) acute leukemias, 16 (28.1%) chronic, 3 (5.3%) prolymphocytic, 1 natural killer cell, and 1 chronic leukemia undergoing blast transformation. N-RAS mis-sense mutations were identified in 14 (25%) dogs with acute myeloid (AML) or lymphoid (ALL) leukemia, and also in one dog in the leukemic phase of lymphoma. Mutations in K-RAS were found in two dogs with AML. There were no H-RAS mutations. FLT3 internal tandem duplications were identified in three dogs with ALL, and a mis-sense mutation was found in one dog with ALL. C-KIT mutations were identified in three dogs with AML. Sixty-one percent of dogs with acute leukemia harbored mutations in N/K-RAS, FLT3, or C-KIT.

CONCLUSION

RAS, FLT3, and C-KIT mutations, analogous to those found in human leukemia, occur commonly in acute canine leukemia.

Spontaneous Feline Mammary Carcinoma Is a Model of HER2 Overexpressing Poor Prognosis Human Breast Cancer

Companion animal spontaneous tumors are suitable models for human cancer, primarily because both animal population and the tumors are genetically heterogeneous. Feline mammary carcinoma (FMC) is a highly aggressive, mainly hormone receptor–negative cancer, which has been proposed as a model for poor prognosis human breast cancer. We have identified and studied the feline orthologue of the HER2 gene, which is both an important prognostic marker and therapeutic target in human cancer. Feline HER2 (f-HER2) gene kinase domain is 92% similar to the human HER2 kinase. F-HER2–specific mRNA was found 3- to 18-fold increased in 3 of 3 FMC cell lines, in 1 of 4 mammary adenomas and 6 of 11 FMC samples using quantitative reverse transcription-PCR. Western blot showed that an anti-human HER2 antibody recognized a protein comigrating with the human p185HER2 in FMC cell lines. The same antibodies strongly stained 13 of 36 FMC archival samples. These data show that feline HER2 overexpression qualifies FMC as homologous to the subset of HER2 overexpressing, poor prognosis human breast carcinomas and as a suitable model to test innovative approaches to therapy of aggressive tumors.

The Basic Biology of Malignant Melanoma: Molecular Mechanisms of Disease Progression and Comparative Aspects

Malignant melanoma (MM) is a life-threatening disease characterized by a highly aggressive biologic behavior in both humans and dogs. Despite improvements in diagnosis and patient care, most deaths from MM are due to metastases that are resistant to conventional treatment modalities. To ultimately reduce the mortality associated with metastatic disease, it is necessary to better define the fundamental molecular mechanisms of malignant tumor progression. The progression of disease is a consequence of the complex interactions between malignantly transformed cells and host factors. Characterization of the stages of tumor progression and the changes occurring in highly malignant cells is important for the development of effective treatment regimens. The dys-regulated molecular mechanisms of transformed melanocytes are presently being characterized. In this review, we summarize the current understanding of the molecular phases in the progression of MM, which include genetic instability, dysregulated proliferation of melanocytes, increased invasion and metastasis, and angiogenesis.

N-ras mutation in a canine lymphoma: short communication

Lymphomas of dogs were investigated by molecular genetic methods. Regions of exon 1 and 2 of the N-ras gene, which harbours the mutation hot spots (codons 12, 13 and 61) were screened. A GGT [symbol: see text] GAT (glycine [symbol: see text] aspartic acid) mutation in codon 13 was present in a multicentric-type lymphoma of a 1-year-old male dog.