Pheochromocytomas (PCs) are tumors arising from the chromaffin cells of the adrenal glands and are the most common tumors of the adrenal medulla in animals. In people, these are highly correlated to inherited gene mutations in the succinate dehydrogenase (SDH) pathway; however, to date, little work has been done on the genetic basis of these tumors in animals. In humans, immunohistochemistry has proven valuable as a screening technique for SDH mutations. Human PCs that lack succinate dehydrogenase B (SDHB) immunoreactivity have a high rate of mutation in the SDH family of genes, while human PCs lacking succinate dehydrogenase A (SDHA) immunoreactivity have mutations in the SDHA gene. To determine if these results are similar for dogs, we performed SDHA and SDHB immunohistochemistry on 35 canine formalin-fixed, paraffin-embedded (FFPE) PCs. Interestingly, there was a loss of immunoreactivity for both SDHA and SDHB in four samples (11%), suggesting a mutation in SDHx including SDHA. An additional 25 (71%) lacked immunoreactivity for SDHB, while retaining SDHA immunoreactivity. These data suggest that 29 out of the 35 (82%) may have an SDH family mutation other than SDHA. Further work is needed to determine if canine SDH immunohistochemistry on PCs correlates to genetic mutations that are similar to human PCs.
Histopathology tissue archives can be an important source of specimens for retrospective studies, as these include samples covering a large number of diseases. In veterinary medicine, archives also contain samples from a large variety of species and may represent naturally-occurring models of human disease. The formalin-fixed, paraffin-embedded (FFPE) tissues comprising these archives are rich resources for retrospective molecular biology studies and pilot studies for biomarkers, as evidenced by a number of recent publications highlighting FFPE tissues as a resource for analysis of specific diseases. However, DNA extracted from FFPE specimens are modified and fragmented, making utilization challenging. The current study examines the utility of FFPE tissue samples from a veterinary diagnostic laboratory archive in five year intervals from 1977 to 2013, with 2015 as a control year, to determine how standard processing and storage conditions has affected their utility for future studies. There was a significant difference in our ability to obtain large amplicons from samples from 2015 than from the remaining years, as well as an inverse correlation between the age of the samples and product size obtainable. However, usable DNA samples were obtained in at least some of the samples from all years tested, despite variable storage, fixation, and processing conditions. This study will help make veterinary diagnostic laboratory archives more useful in future studies of human and veterinary disease.
Canine osteosarcoma is an extremely malignant bone tumor that often arises in the bones of the limbs. It is a highly metastatic disease distinguished by proliferative bone lesions and a tendency for pulmonary metastasis. Overexpression of proliferative proteins are associated with bad prognosis in human osteosarcoma. Here, we tested the expression of the different proliferative proteins (p53, p16, vimentin, and mdm2) in nine archival samples with canine osteosarcoma. Paraffin-embedded tissue sections were confirmed by histopathology and stained by immunohistochemistry for p53, p16, vimentin and mdm2. Positive expression of these proteins was evaluated as the ratio of positive cancer cells and the intensity staining was assessed in several areas. Histopathologically, 95% of samples were grade II and III. All high-grade osteosarcomas were particularly cellular. The cancer cells were generally large spindle-shaped and large nucleus with distribution of osteoid between the cancer cells. Immunohistochemical detection of p53, p16, vimentin and mdm2 was 89%, 56%, 78%, and 89% of samples respectively. The staining intensity for p53, p16, vimentin and mdm2 was particularly nuclear in 81%, 66%, 78%, and 79% of the cancer cells respectively. Our present work suggests that p53, p16, vimentin, and mdm2 were detected in grade III canine osteosarcomas samples. In addition, these proliferative markers are the significant biomarkers in canine osteosarcomas and can be used as a predictor for diagnostic and prognostic value and allowing cancer differentiation. This primary data supports that both canine and human osteosarcomas share same molecular characters which are approved by expression of proliferative genes.
Pheochromocytomas (PCs) are tumors originating from the chromaffin cells of the adrenal medulla. In people, there are highly correlated to inherited gene mutations in the succinate dehydrogenase (SDH) pathway; however, to date, little work has been done on the genetic basis of these tumors in animals. Out of the total of 2.203 Gb of canine DNA sequenced, 88.35% of bases mapped to exons and 11.65% mapped to introns. Out of 26 genes of interest containing 404 exons, 278 exons were sequenced 68.81%. Sequencing was considered successful when the average read depth was 3x and the entire exon was covered. Coverage ranged from 30% to 100%. Both SDHA and SDHB had exon mapped 46.6% and 62.5% respectively. Additionally, out of 45 known canine variants, exome technique able to detect 36 variants (80%). We performed SDHA and SDHB immunohistochemistry on 35 canine formalin-fixed, paraffin embedded. Interestingly, we had loss of immunoreactivity for both SDHA and SDHB in four samples, suggesting a mutation in SDHx including SDHA. Out of 35 samples, 6 had immunoreactivity for SDHA and 25 lacked immunoreactivities for SDHB. 29 out of the 35 (82%) may have an SDH family mutation other than SDHA. Exome sequencing and immunohistochemistry are able to predict malignant behaviour and likelihood of reduction of PCC/PGLs in humans. This can be used to determine whether there are similar mutations in the pseudo-hypoxic, kinase signalling, and other genes of interest exist in dogs, as well as finding novel genes involved in canine Pheochromocytomas oncogenesis.
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