Papillomaviral DNA and increased p16^CDKN2A protein are frequently present within feline cutaneous squamous cell carcinomas in ultraviolet‐protected skin

Abstract

Squamous cell carcinomas (SCCs) are common feline skin tumours. While exposure to ultraviolet (UV) light causes some SCCs, a subset develop in UV-protected skin. In cats, papillomaviruses (PVs) cause viral plaques and Bowenoid in situ carcinomas (BISCs). As both may progress to SCC, it was hypothesized that SCCs in UV-protected skin may represent neoplastic transformation of a PV-induced lesion. To investigate this hypothesis, PCR was used to amplify PV DNA from 25 UV-protected and 45 UV-exposed SCCs. Oncogenic human PVs cause neoplasia by mechanisms that also increase p16(CDKN2A) protein (p16). As increased p16 is present in feline viral plaques and BISCs, immunohistochemistry was used to detect p16 within the SCCs. Papillomaviral DNA was amplified from 76% of UV-protected SCCs, but only 42% of UV-exposed SCCs. Increased p16 was present in 84% of UV-protected SCCs, but only 40% of UV-exposed SCCs. The more frequent detection of PV DNA and increased p16 within UV-protected SCCs supports the hypothesis that some develop from a PV-induced plaque or BISC. Felis domesticus PV-2 is thought to cause viral plaques and BISCs. This PV was detected most frequently within the UV-protected SCCs, supporting development from a PV-induced lesion. Increased p16 and PV DNA were less frequent within UV-exposed SCCs, presumably because these developed from actinic keratosis rather than a PV-induced lesion. The results support the hypothesis that some feline cutaneous SCCs are caused by PV infection and suggest that PVs may cause neoplasia by mechanisms that also increase p16.

Loss of Retinoblastoma Protein, But Not p53, Is Associated With the Presence of Papillomaviral DNA in Feline Viral Plaques, Bowenoid In Situ Carcinomas, and Squamous Cell Carcinomas

“…However, as PVs can asymptomatically infect feline skin, 28 the detection of PV DNA within a cutaneous SCC does not prove that the virus influenced neoplasm development. As has been reported, 22 PV DNA was detected in the present study more frequently in SCCs from UV-protected areas than in SCCs from UV-exposed skin. In people, protection from UV light decreases asymptomatic PV skin infection.…”

“…20 Associations between increased p16 and the presence of PV DNA within feline cutaneous SCCs have been reported. 21,22 However, this is the first evidence to suggest that feline PV infection could increase p16 by degrading pRb. While these results suggest that feline PV infection may alter cellular regulation by disrupting the pRb/p16 pathway, it cannot be confirmed that this action influences neoplastic transformation of the cells.…”

“…24 The JMY2F/R and JMY3F/R primers were used to amplify 2 PV DNA sequences that have been detected in feline cutaneous SCCs. 22 All polymerase chain reactions were carried out in duplicate. DNA extracted from a feline viral plaque was used as a positive control for the JMPF/R primers, while DNA extracted from a bovine fibropapilloma was used for the MY09/11 primers.…”

“…Due to the previously demonstrated specificity of the JMPF/R, JMY2F/R, and JMY3F/R primers, the DNA amplified by these primers was not sequenced. 22,24 As antibodies against pRb have not been used in cats, Western blotting was used to confirm the specificity of the antibodies used to feline pRb. Briefly, tissue lysates of feline liver were prepared and diluted in Laemmli buffer to a final protein concentration of 2.5 mg/mL and heated at 100 C for 5 minutes.…”

Frequent detection of transcriptionally active Felis catus papillomavirus 2 in feline cutaneous squamous cell carcinomas

“…Early evidence of this was the observation of transitional lesions between papillomavirus-induced premalignant lesions and SCCs (Baer & Helton, 1993). Subsequently FcaPV-2 DNA was detected in *50 % of all feline cutaneous SCCs, in particular 76 % of those that occur in densely haired skin (Munday et al, 2011b). In comparison, FcaPV-2 DNA was found in v10 % of non-SCC skin lesions (Munday et al, 2011a).…”