Significance of p53‐binding protein 1 nuclear foci in uterine cervical lesions: endogenous DNA double strand breaks and genomic instability during carcinogenesis

Abstract

Significance of p53-binding protein 1 nuclear foci in uterine cervical lesions: endogenous DNA double strand breaks and genomic instability during carcinogenesis Aims: A defective DNA damage response can result in genomic instability (GIN) and lead to transformation to cancer. As p53-binding protein 1 (53BP1) localizes at the sites of DNA double strand breaks (DSBs) and rapidly forms nuclear foci (NF), the presence of 53BP1 NF can be considered to be an indicator of endogenous DSBs reflecting GIN. Our aim was to analyse the presence of DSBs by immunofluorescence for 53BP1 expression in a series of cervical lesions, to evaluate the significance of GIN during carcinogenesis. Methods and results: A total of 80 archival cervical tissue samples, including 11 normal, 16 cervical intraepithelial neoplasia (CIN)1, 15 CIN2, 24 CIN3 and 14 squamous cell carcinoma samples, were analysed for 53BP1 NF, human papillomavirus (HPV) infection, and p16INK4a overexpression. The number of 53BP1 NF in cervical cells appeared to increase with progression during carcinogenesis. The distribution of 53BP1 NF was similar to that of the punctate HPV signals as determined by in-situ hybridization and also to p16 INK4a overexpression in CIN, suggesting an association with viral infection and replication stress. Conclusions: Immunofluorescence analysis of 53BP1 expression can be a useful tool with which to estimate the level of GIN. During cervical carcinogenesis, GIN may allow further accumulation of genomic alterations, causing progression to invasive cancer.

Association between p53-binding protein 1 expression and genomic instability in oncocytic follicular adenoma of the thyroid

“…We note that patients with oncocytic FA were older than those with conventional FA, consistent with previous findings regarding the general population of patients with oncocytic FA [34]. Although we cannot completely exclude the possibility that age difference contributed to the differential expression of 53BP1, our previous studies indicated that 53BP1 expression pattern is largely influenced by pathological grade and the pattern of neoplasms [22,23,27,35]. Oncocytic cells contain large numbers of mitochondria harboring morphologic, functional, and genetic abnormalities.…”

“…It has been well documented in vitro by immunofluorescence studies that 53BP1 exhibits faint diffuse nuclear staining in untreated primary cells, whereas after exposure to radiation, 53BP1 is localized at the sites of DNA double-strand breaks and forms discrete nuclear foci [20,21]. We have recently demonstrated that the presence of 53BP1 nuclear foci as detected by immunofluorescence might serve as a valuable molecular marker of genomic instability during carcinogenesis, which seems to be induced at the precancerous stage during thyroid, skin and cervical carcinogenesis, as follicular adenoma and actinic keratosis [22,23]. Gorgoulis et al, have also shown, by immunofluorescence study, that hyperplasia of lung and skin was associated with the expression of p53 or 53BP1 nuclear foci [24].…”

“…Signals were analyzed at ×1,000 magnification. Based on our previous reports [22,23], we categorized 53BP1 immunoreactivity and into three types in the current study as shown in Fig. 1: i) stable: absent or faint nuclear staining; ii) intermediate: one or two discrete nuclear foci; or iii) heated by microwave in 0.01 M citrate buffer (pH 6.0) and pretreated with 0.3% pepsin.…”

TRIP12 as a mediator of human papillomavirus/p16-related radiation enhancement effects

“…In HPV-positive cervical cancer, the distribution of 53BP1 foci is similar to that of p16 overexpression (12), and in HPV-positive anal carcinoma, markedly enlarged 53BP1 foci are accompanied by drastically increased RNF168 levels (13); however, the direct link between p16 and 53BP1-RNF168 was unclear. In the current study, we found that p16 overexpression not only caused persistence of 53BP1 foci 24 hours after RT but the protein levels of RNF168 were also modulated in a similar fashion.…”

“…In cervical cancer, the distribution of 53BP1 nuclear foci was similar to that of punctate HPV signals and p16 expression (13). In HPV-positive anal carcinoma, markedly enlarged 53BP1 foci were accompanied by dramatically increased RNF168 levels (14).…”