APOBEC3B high expression status is associated with aggressive phenotype in Japanese breast cancers

The members of AID/APOBEC protein family possess cytidine deaminase activity that converts cytidine residue to uridine on DNA and RNA. Recent studies have shown the possible influence of APOBEC3B (A3B) as DNA mutators of breast cancer genome. However, the clinical significance of A3B expression in Japanese breast cancer has not been studied in detail.

Ninety-three primary breast cancer tissues (74 estrogen-receptor (ER) positive, 3 ER and HER2 positive, 6 HER2 positive, and 10 triple negative) including 37 tumor-normal pairs were assessed for A3B mRNA expression using quantitative real-time RT-PCR. We analyzed the relation between A3B expression, mutation analysis of TP53 and PIK3CA by direct sequencing, polymorphic A3B deletion allele and human papillomavirus (HPV) infection in tumors.

A3B mRNA was overexpressed in tumors compared with normal tissue. Patients with high A3B expression were associated with subtype and progression of lymph node metastasis and pathological nuclear grade. However, the expression was not related to any other clinicopathological factors, including mutation of TP53 and PIK3CA, polymorphic A3B deletion allele, HPV infection and survival time.

The expression of A3B in breast cancer was higher than in non-cancerous tissues and was related to the lymph node metastasis and nuclear grade, which are reliable aggressive phenotype markers in breast cancer. Evaluation of A3B expression in tumor may be a marker for breast cancer with malignant potential.