Determination of oxidative DNA damage and i̇nflammation in the differentiation grades of feline squamous cell carcinomas: The role of Nrf2/HO-1/Keap1 and TLR4/NF-κB/COX-2/ICAM-1 pathways

FSCC is a relatively common tumor of the skin and mucocutaneous regions in cats, yet the molecular features that accompany its varying degrees of differentiation are not fully clarified. In this study, we examined 27 FSCC cases and compared well, moderately, and poorly differentiated tumors using routine histopathology together with immunohistochemical, immunofluoresence, and RT-PCR based analyses. Differentiation grade was determined by keratin pearl formation, tumor island morphology, squamous differentiation, mitotic activity, and the extent of peritumoral inflammation. Poorly differentiated tumors showed a consistent pattern in which oxidative DNA damage (8-OHdG) was noticeably higher, while the Nrf2/HO-1 pathway was clearly suppressed and Keap1 expression increased. These changes were accompanied by stronger IL-6 and ICAM-1 staining and marked activation of inflammatory markers related to the TLR4/NF-κB/COX-2 axis. In contrast, well-differentiated tumors tended to retain higher Nrf2 and HO-1 expression with lower activation of pro-inflammatory pathways, suggesting a more balanced redox response. The inflammatory burden and mitotic activity were also most pronounced in poorly differentiated lesions. Overall, the findings indicate that deterioration of differentiation in FSCC parallels a shift toward heightened oxidative stress and amplified inflammatory signaling. The combined dysregulation of the Nrf2/HO-1/Keap1 and TLR4/NF-κB/COX-2 appears to contribute to a more aggressive tumor microenvironment, offering potential insight into the biological behavior of these lesions.