DNA Methylation Status of the Estrogen Receptor α Gene in Canine Mammary Tumors

Abstract

Estrogen receptor α (ERα) has an important role in mammary carcinogenesis, prognosis, and treatment. In human and canine mammary cancer, the most aggressive tumors show loss of ERα expression, which in human breast cancer has been attributed to methylation of the cytosine followed by guanine (CpG) island within the estrogen receptor α gene ( ESR1) promoter. This study aimed to investigate the role of ESR1 CpG island (CGI) methylation in ERα expression in canine mammary tumors. Twenty-one canine mammary samples were sorted into three groups: malignant tumor (n = 9), benign tumor (n = 8), and normal gland (n = 4). Immunohistochemical analysis and reverse-transcription quantitative real-time PCR were performed to assess ERα expression and ESR1 mRNA levels. The methylation status was determined using sodium-bisulfite-treated DNA sequencing. All normal mammary glands and benign tumors showed high ERα expression (score range, 5-8). Six of the nine malignant tumors did not show ERα expression (score 0), two had score 2, and one had score 4. Lower ERα ( P < .005) and ESR1 mRNA levels ( P < .005) were found in malignant mammary tumors than in the other two groups. Canine ESR1 has an intragenic and non-promoter-associated CGI, different from humans. No significant variation in methylation percentage was observed among the groups, suggesting that ESR1 is not regulated by DNA methylation, unlike that in humans. This difference should be considered in further research using ERα as a biomarker for mammary tumors in canine studies on ERα-targeting therapy.

Analysis of DNA methylation and TP53 mutational status for differentiating feline oral squamous cell carcinoma from non‐neoplastic mucosa: A preliminary study

“…Few studies have investigated DNA methylation patterns in animal tumours, 26‐29 and no information is currently available on the methylation status of FOSCC.…”

“…[17][18][19][20][21][22] This is further supported by evidence that these epigenetic modifications are likely early events in oral carcinogenesis, as histologically normal tissue adjacent to tumours and pre-malignant oral lesions often reveal an aberrant methylation pattern as well. [23][24][25] Few studies have investigated DNA methylation patterns in animal tumours, [26][27][28][29] and no information is currently available on the methylation status of FOSCC.…”

DNA methylation landscape of triple-negative ductal carcinoma in situ (DCIS) progressing to the invasive stage in canine breast cancer

“…Limited studies have investigated gene-specific changes in DNA methylation in canine breast cancer. DNA methylation patterns in CGIs of ESR1, encoding for ERα, and BRCA1, an important tumor suppressor gene, have recently been examined 32,33 , reporting changes in DNA methylation of these genes in malignant canine tumors. Moreover, LINE-1 methylation in cell free DNA (cfDNA) from liquid biopsies was used in a comparative approach of canine and human breast tumors 34 .…”

Epigenetic Mechanisms in Canine Cancer

“…In human breast cancer, the most aggressive type of cancer is triple-negative breast cancer, featured by the lack of ERa expression, which is mainly attributed to ERa promoter methylation (77,78). However, no significant variation in methylation patterns were found between ERa-positive canine mammary carcinomas and ERa-negative canine mammary carcinomas pointing to a difference of ERa regulation mechanisms between human and dogs (79).…”