A subset of equine oral squamous cell carcinomas is associated with Equus caballus papillomavirus 2 infection.

This study explores the potential relationship between Equus caballus papillomavirus 2 (EcPV2) and the development of oral squamous cell carcinoma (SCC) in horses, a type of oral cancer whose cause remains unclear but is suspected to be linked to papillomavirus infection and chronic gum disease.

Hypothesis

• With human oropharyngeal cancers often associated with human papillomaviruses, and Equus caballus papillomavirus 2 (EcPV2) suspected to cause equine genital SCC, the researchers theorized that EcPV2 could also be linked to the development of oral SCC in horses.

Methodology

• To explore this theory, the researchers conducted a standard polymerase chain reaction (PCR), a genetic test, and in-situ hybridization (ISH), a technique that enables researchers to detect specific gene sequences in their natural microscopic environment, on 31 samples of preserved equine oral SCC and 10 non-SCC oral samples.

Results

• PCR tests revealed that 10 out of the 31 (32%) oral SCC samples were positive for EcPV2, whereas all the non-SCC oral samples tested negative.
• ISH identified intense hybridization signals for EcPV2 nucleic acid in 8 out of the 31 (26%) oral SCCs specifically within the neoplastic epithelial cells (cells that lead to the formation of tumors), but not in the adjacent normal oral mucosa (mucus membranes of the mouth).
• Control samples showed no such hybridization signals.

Implications

• The results of this study strengthen the case for a pathogenic association of EcPV2 in developing oral SCC in horses, pointing to a potential cause for this type of cancer.