Significance of abnormal 53BP1 expression as a novel molecular pathologic parameter of follicular-shaped B-cell lymphoid lesions in human digestive tract

Detection of genome instability by 53BP1 expression as a long-lasting health effect in human epidermis surrounding radiation-induced skin cancers

We previously reported endogenous activation of the DNA damage response (DDR) in the epidermis surrounding basal cell carcinoma resected from Nagasaki atomic bomb survivors, suggesting the presence of genomic instability (GIN) in the survivors as a late effect of radiation. Dual-color immunofluorescence (IF) analysis of TP53-binding protein-1 (53BP1) and a proliferative indicator, Ki-67, to elucidate GIN in tumor tissues revealed that abnormal 53BP1 expression is closely associated with carcinogenesis in several organs. The present study aimed to confirm the presence of radiation-induced GIN in the non-neoplastic epidermis of patients with radiation-induced skin cancer. Formalin-fixed paraffin-embedded tissues were obtained from all participants between 2008 and 2019 at the Nagasaki University Hospital. 53BP1 nuclear expression was examined using dual-color IF analysis with Ki-67 expression to assess the extent and integrity of the DDR. Expressions of gamma-H2AX, p53 and p21 were also analyzed using the dual-color IF analysis for their association with 53BP1. The results of this study provide evidence for sporadic activation of the DDR in medically irradiated and ultraviolet-exposed epidermis as a long-lasting radiation effect, which is a predisposition to skin cancer. Furthermore, the incidence of abnormal 53BP1 expression in cancer cells was higher than in non-neoplastic epidermal cells surrounding cancer, suggesting a correlation between the type of 53BP1 and the malignant potential of skin tumors. This study highlights the usefulness of dual-color IF for 53BP1 (and Ki-67) as an indicator to estimate the level of GIN as a long-lasting health effect of radiation exposure.

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 p16INK4a 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 p16INK4a 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.

Follicular Thyroid Adenoma and Follicular Thyroid Carcinoma-A Common or Distinct Background? Loss of Heterozygosity in Comprehensive Microarray Study

Pre- and postsurgical differentiation between follicular thyroid adenoma (FTA) and follicular thyroid cancer (FTC) represents a significant diagnostic challenge. Furthermore, it remains unclear whether they share a common or distinct background and what the mechanisms underlying follicular thyroid lesions malignancy are. The study aimed to compare FTA and FTC by the comprehensive microarray and to identify recurrent regions of loss of heterozygosity (LOH). We analyzed formalin-fixed paraffin-embedded (FFPE) samples acquired from 32 Caucasian patients diagnosed with FTA (16) and FTC (16). We used the OncoScan™ microarray assay (Affymetrix, USA), using highly multiplexed molecular inversion probes for single nucleotide polymorphism (SNP). The total number of LOH was higher in FTC compared with FTA (18 vs. 15). The most common LOH present in 21 cases, in both FTA (10 cases) and FTC (11 cases), was 16p12.1, which encompasses many cancer-related genes, such as TP53, and was followed by 3p21.31. The only LOH present exclusively in FTA patients (56% vs. 0%) was 11p11.2-p11.12. The alteration which tended to be detected more often in FTC (6 vs. 1 in FTA) was 12q24.11-q24.13 overlapping FOXN4, MYL2, PTPN11 genes. FTA and FTC may share a common genetic background, even though differentiating rearrangements may also be detected.

A New Indicator to Differentiate Thyroid Follicular Inclusions in Cervical Lymph Nodes from Patients with Thyroid Cancer

Nodal metastasis is crucial for determining the stage of well-differentiated thyroid cancer (WTC) in patients older than 55. Well-formed thyroid follicular inclusions (TFIs) are occasionally encountered in the cervical lymph nodes (LNs) of patients with papillary thyroid carcinoma (PTC), and it is difficult to determine whether they are true nodal metastases or ectopic thyroid tissues (ETT). This study aimed to elucidate the impact of the expression of the DNA damage response molecule TP53-binding protein 1 (53BP1) using immunofluorescence (IF) as a biomarker to differentiate TFIs in cervical LN by comparing the mutation analyses of primary thyroid cancers. The data demonstrated the necessity for the differential diagnosis of true metastases from ETT among TFIs in cervical LNs. PTC-like nuclear features using hematoxylin-eosin staining combined with immunohistochemistry for conventional biomarkers of PTC, including BRAF^V600E protein, were most helpful in identifying metastatic follicular-patterned carcinomas. In conclusion, IF analysis of 53BP1 expression could be an excellent ancillary technique to distinguish metastatic carcinoma or ETT from TFIs in LNs, particularly in cases other than BRAF^V600E-mutated PTC.

Molecular Pathological Characteristics of Thyroid Follicular-Patterned Tumors Showing Nodule-in-Nodule Appearance with Poorly Differentiated Component

Thyroid follicular-patterned tumors (TFTs) showing nodule-in-nodule (NN) appearance with poorly differentiated component (PDc) but neither invasion nor metastasis are diagnosed as benign nodules. Although PDc exhibits histologically aggressive features relative to the outer nodule (Out-N), its pathological significance remains unclear. TP53 binding protein-1 (53BP1) is a DNA damage response (DDR) molecule that rapidly localizes at DNA double-strand breaks. Using dual-color immunofluorescence with Ki-67, the profile of 53BP1 expression is shown to be significantly altered during diverse tumorigenesis. In this study, we aimed to elucidate the malignant potential of PDc at the molecular level. We analyzed the profile of 53BP1 expression and NRAS codon 61 and TERT-promoter (TERT-p) mutations in 16 cases of TFTs showing NN with PDc compared to 30 adenomatous goiters, 31 follicular adenomas, 15 minimally invasive follicular carcinomas (FCs), and 11 widely invasive FC cases. Our results revealed that the expression level of abnormal type 53BP1 and incidence of NRAS and TERT-p mutations in PDc were comparable to FCs, suggesting a malignant potential. Because co-expression of 53BP1 and Ki-67 can be an indicator of altered DDR, the development of PDc in NN may be associated with DDR impairments after harboring NRAS and TERT-p mutations.