Analysis for type of 53BP1 nuclear expression by immunofluorescence as an indicator of genomic instability in oropharyngeal squamous epithelial lesions

A subset of oropharyngeal squamous cell carcinoma (OPSCC) is caused by the high-risk human papilloma virus (HPV), which expresses p16^INK4a immunoreactivity. Dual-color immunofluorescence (IF) analysis of TP53 binding protein-1 (53BP1) and a proliferative indicator, Ki-67, to elucidate genomic instability (GIN) in tumor tissues revealed that abnormal 53BP1 expression is closely associated with carcinogenesis in diverse organs. We have previously demonstrated that the number of 53BP1 nuclear foci (NF) in cervical cells increases with cancer progression. The distribution of 53BP1 NF was similar to that of punctate HPV signals, as determined by in situ hybridization, and the pattern of p16^INK4a overexpression. The present study aimed to confirm the type of 53BP1 expression using dual-color IF as an indicator of GIN in oropharyngeal squamous epithelial lesions, including HPV-dependent and -independent OPSCC. This study identified significant differences in the nuclear expression of 53BP1 between benign oropharyngeal epithelial lesions and OPSCC, and between HPV-dependent and HPV-independent OPSCC. We concluded that the incidence of abnormal 53BP1 expression in OPSCC is significantly associated with stage classification and overall survival. Therefore, double IF analysis of 53BP1 and Ki-67 expression may be a useful tool for estimating the malignant potential and prognosis of OPSCC.