Quantification of Global DNA Methylation in Canine Melanotic and Amelanotic Oral Mucosal Melanomas and Peripheral Blood Leukocytes From the Same Patients With OMM: First Study

Nayra Villar Scattone; Tatiane Moreno Ferrarias Epiphanio; Karine Germano Caddrobi; Juliana Shimara Pires Ferrão; Francisco Javier Hernandez-Blazquez; Ana Paula de Melo Loureiro; Cristina de Oliveira Massoco; Maria Lucia Zaidan Dagli

doi:10.3389/fvets.2021.680181

Quantification of Global DNA Methylation in Canine Melanotic and Amelanotic Oral Mucosal Melanomas and Peripheral Blood Leukocytes From the Same Patients With OMM: First Study

Front Vet Sci. 2021 Aug 24:8:680181. doi: 10.3389/fvets.2021.680181. eCollection 2021.

Authors

Nayra Villar Scattone¹, Tatiane Moreno Ferrarias Epiphanio¹, Karine Germano Caddrobi², Juliana Shimara Pires Ferrão³, Francisco Javier Hernandez-Blazquez⁴, Ana Paula de Melo Loureiro⁵, Cristina de Oliveira Massoco⁶, Maria Lucia Zaidan Dagli¹

Affiliations

¹ Laboratory of Experimental and Comparative Oncology, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil.
² PROVET Veterinary Hospital, São Paulo, Brazil.
³ Department of Biomedicine, Faculty Anhanguera, Guarulhos, Brazil.
⁴ Department of Surgery, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil.
⁵ Department of Clinical and Toxicological Analysis, School of Pharmaceutical Sciences, University of São Paulo, São Paulo, Brazil.
⁶ Laboratory of Pharmacology and Toxicology, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil.

Abstract

Oral mucosal melanomas (OMMs) are aggressive and resistant cancers of high importance in veterinary oncology. Amelanotic OMM produces comparatively less melanin and is considered to be more aggressive than melanotic OMM. Global DNA methylation profiles with hypomethylated or hypermethylated patterns have both been associated with aggressive neoplasms; however, global DNA hypomethylation seems to correlate to higher aggressiveness. Accordingly, global DNA methylation in peripheral blood leukocytes has been investigated to understand the role of systemic or environmental factors in cancer development. This study aimed to quantify global DNA methylation in canine melanotic and amelanotic OMM samples and in the peripheral blood leukocytes of the same dogs. Tumor tissue samples were collected from 38 dogs, of which 19 were melanotic and 19 were amelanotic OMM. These were submitted to immunohistochemistry (IHC) with anti-5-methylcytosine (5mC) and anti-Ki67 primary antibodies. Ki67- and 5mC-positive nuclei were manually scored with the help of an image analysis system. Peripheral blood samples were collected from 18 among the 38 OMM-bearing dogs and from 7 additional healthy control dogs. Peripheral blood leukocytes were isolated from the 25 dogs, and DNA was extracted and analyzed by high-performance liquid chromatography (HPLC) for global DNA methylation. The pattern of global DNA methylation in both canine melanotic and amelanotic OMM indicated higher percentages of weakly or negatively stained nuclei in most of the OMM cells, presuming predominant global DNA hypomethylation. In addition, Ki67 counts in amelanotic OMM were significantly higher than those in melanotic OMM (p < 0.001). Global DNA methylation different immunostaining patterns (strong, weak or negative) correlated with Ki67 scores. Global DNA methylation in circulating leukocytes did not differ between the 9 melanotic and 9 amelanotic OMM or between the 18 OMM-bearing dogs and the 7 healthy dogs. This study provides new information on canine melanotic and amelanotic OMM based on global DNA methylation and cell proliferation.

Keywords: DNA methylation; cancer; cell proliferation; dog; melanoma.