Differential expression of Oct3/4 in human breast cancer and normal tissues.

Abstract

Oct3/4, a transcription factor specifically expressed in mammalian totipotent embryonic stem and germ cells, has a critical role in the regulation and maintenance of pluripotency and self-renewal. However, reactivation of Oct3/4 expression is observed in several human breast cancer cell lines, but not in non‑malignant cells. To examine Oct3/4 expression in human primary breast carcinomas and normal breast tissues, we obtained breast tumor tissues from 28patients and normal breast tissues from 9women. According to quantitative polymerase chain reaction, all of the tumor tissues, irrespective of tumor type or clinicopathological status, expressed Oct3/4 mRNA at 10- to100- fold higher levels than that in the normal breast tissues. Expression of the Oct3/4 protein in tumors was confirmed by western blot analysis and immunofluorescent staining. Additionally, rapid amplification of cDNA ends and DNA sequencing revealed expression of multiple Oct4 gene transcripts from chromosome6 (POU5F1) in normal breast tissues and the non‑malignant breast epithelial cell line MCF‑10A; by contrast, the breast tumors and malignant breast cancer cell line MCF‑7 predominantly expressed transcripts of an Oct4-like gene (POU5F1B) from chromosome8, which was termed Oct3 in the current study. The deduced amino acid sequences of full-length Oct3 and Oct4 are 96% identical. The findings of the current study indicated that Oct3, rather than Oct4, may serve as a novel clinical marker and a potential target for gene-specific therapy of breast cancer.