APOBEC3B High Expression in Gastroenteropancreatic Neuroendocrine Neoplasms and Association With Lymph Metastasis

APOBEC3-mediated mutagenesis in cancer: causes, clinical significance and therapeutic potential

Apolipoprotein B mRNA-editing enzyme, catalytic polypeptides (APOBECs) are cytosine deaminases involved in innate and adaptive immunity. However, some APOBEC family members can also deaminate host genomes to generate oncogenic mutations. The resulting mutations, primarily signatures 2 and 13, occur in many tumor types and are among the most common mutational signatures in cancer. This review summarizes the current evidence implicating APOBEC3s as major mutators and outlines the exogenous and endogenous triggers of APOBEC3 expression and mutational activity. The review also discusses how APOBEC3-mediated mutagenesis impacts tumor evolution through both mutagenic and non-mutagenic pathways, including by inducing driver mutations and modulating the tumor immune microenvironment. Moving from molecular biology to clinical outcomes, the review concludes by summarizing the divergent prognostic significance of APOBEC3s across cancer types and their therapeutic potential in the current and future clinical landscapes.

APOBEC3B Is Co-Expressed with PKCα/NF-κB in Oral and Oropharyngeal Squamous Cell Carcinomas

The enzymatic activity of APOBEC3B (A3B) has been implicated as a prime source of mutagenesis in head and neck squamous cell carcinoma (HNSCC). The expression of Protein Kinase C α (PKCα) and Nuclear Factor-κΒ p65 (NF-κΒ p65) has been linked to the activation of the classical and the non-canonical NF-κB signaling pathways, respectively, both of which have been shown to lead to the upregulation of A3B. Accordingly, the aim of the present study was to evaluate the expression of PKCα, NF-κΒ p65 and A3B in non-HPV related oral and oropharyngeal squamous cell carcinomas (SCC), by means of immunohistochemistry and in silico methods. PKCα was expressed in 29/36 (80%) cases of oral and oropharyngeal SCCs, with 25 (69%) cases showing a PKCα+/A3B+ phenotype and only 6/36 (17%) cases showing a PKCα-/A3B+ phenotype. Εxpression of NF-κB p65 was seen in 33/35 (94%) cases of oral and oropharyngeal SCCs, with 30/35 (86%) cases showing an NF-κB p65+/A3B+ phenotype and only 2/35 (6%) cases showing an NF-κB p65-/A3B+ phenotype. In addition, mRNA expression analysis, using the UALCAN database, revealed strong expression of all three genes. These findings indicate that the expression of A3B is associated with PKCα/NF-κB p65 expression and suggest a potential role for the PKC/NF-κB signaling pathway in the development of oral and oropharyngeal cancer.

Unfavorable prognosis and clinical consequences of APOBEC3B expression in breast and other cancers: A systematic review and meta-analysis

INTRODUCTION: Controversy exists regarding the association of apolipoprotein B mRNA editing enzyme catalytic subunit 3B APOBEC3B, (A3B) overexpression and poor prognosis, metastasis, and chemotherapy drug resistance in cancers. Here we conducted a systematic review and meta-analysis to determine its prognostic value and clinicopathological features in breast cancer and some other malignancies. MATERIALS AND METHODS: PubMed, Scopus, Cochrane Library, Web of Science, and EMBASE were searched up to Feb 2022 for the association of A3B with breast, ovarian, gastrointestinal and lung cancers. The pooled hazard ratios with 95% confidence interval (CI) were evaluated to assess disease-free survival (DFS), overall survival (OS), and recurrence-free survival (RFS) in cancers under study. RESULTS: Over 3700 patients were included in this meta-survey. Elevated levels of A3B were significantly related to low OS (pooled HR = 1.30; 95% CI:1.09–1.55, P < 0.01), poor DFS (pooled HR = 1.66; 95% CI:1.17–2.35, P < 0.01) and poor RFS (HR = 1.51, 95% CI:1.11–2.04, P = 0.01). Subgroup analysis revealed that high A3B expression was associated with poor OS in lung (HR = 1.85, 95% CI: 1.40–2.45), and breast cancers (HR = 1.38, 95% CI: 1.00–1.89). High expression of A3B did not display any significant association with clinicopathologic features. CONCLUSION: APOBEC3B overexpression is related to poor OS, DFS and RFS only in some cancer types and no generalized role could be predicted for all cancers.

Breast Microinvasive Carcinoma With Different Morphologies: Analysis of Clinicopathologic Features of 121 Cases

Purpose:

To investigate the clinicopathological features of patients with breast microinvasive carcinoma (MI).

Methods:

The clinical data of 121 cases with breast MI were retrospectively collected. The whole tumor in each case was stained with hematoxylin and eosin (H&E) for pathological evaluation. The relationships among size of tumor, histological grade, tumor-infiltrating lymphocytes (TILs), the number of MIs, type of MI, and lymph node metastasis were analyzed.

Results:

It was revealed that 86% of the cases had high-grade ductal carcinoma in situ (DCIS) and 63.6% had multiple MIs. The larger size of the tumors, the higher the grade of DCIS, the more the number of MIs; 3.3% of cases had rich TILs (lymphocyte/stroma > 30%) in the DCIS, and 26.5% had rich TILs in MIs. The type A of MIs is characterized by single cells and small clusters of solid cells. Tumor cells in type B of MIs can form glandular ducts. Formal grading of microinvasive is challenging/impossible due to its limited size precluding a representative mitotic count. But nuclear grade and tubule (differentiation) grades can be reported. In addition, 72.7% of cases had type A of MIs and 27.3% of cases had type B of MIs. Type B was found to be highly accompanied by moderate-grade DCIS. Only 6.6% of patients with MI had lymph node metastasis, which was mainly related to MIs with less TILs.

Conclusion:

Breast MI is easy to occur in high-grade DCIS, and multiple infiltration foci may be observed in case with tumor size of higher than 3.5 cm. Microinvasive carcinoma with poor TILs maybe a risk factor for lymph node metastasis in patient with DCIS-Mi.

The Prognostic Significance of APOBEC3B and PD-L1/PD-1 in Nasopharyngeal Carcinoma

PURPOSE

Apolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3B (APOBEC3B) is a recently discovered protein that is considered important in causing mutations in tumor cell genome bases. Whether APOBEC3B is expressed in nasopharyngeal carcinoma (NPC) still remains unknown. Studies have shown that programmed-cell-death receptor-1 ligand (PD-L1) is highly expressed in NPC, but its clinical significance has not been fully elucidated. We aimed to evaluate APOBEC3B and PD-L1 protein expression in NPC and also investigate their prognostic significance.

MATERIALS AND METHODS

One hundred and three patients with NPC were retrospectively collected in this study, and were followed-up for 5 years. The expression of APOBEC3B and PD-L1/PD-1 in NPC was detected by immunohistochemical staining.

RESULTS

High expression of APOBEC3B was observed in 42.7% of NPC patients. The high expression rate of APOBEC3B was 31.5% in patients without recurrence or metastasis within 5 years, and 55.1% in those patients with recurrence or metastasis, and the difference was statistically significant (P=0.016). There was no significant difference in APOBEC3B expression among patients with different sex, age group, and clinical stage (P>0.05). The positive expression rate of PD-L1 was 55.3% in all patients with NPC. There was no significant difference in PD-L1 expression among patients with different sex, age group, clinical stage, and tumor recurrence or metastasis condition (P> 0.05). There was no significant correlation between the expression of APOBEC3B and PD-L1 in NPC patients. The positive expression rate of PD-1 was 1.9% (2/103) in patients with NPC.

CONCLUSIONS

APOBEC3B showed association with aggressive behavior and poor outcome in NPC, and is also considered as a potential marker for predicting NPC recurrence or metastasis. PD-L1 is not associated with the aggressive behavior and poor outcome in NPC.