Detection Of The Homolog Sequences Of MMTV And HERV In Human Breast Cancer, Subcloning And Expression

Purpose: to detect the homologous sequences of mouse mammary tumor virus (MMTV) and human endogenous retrovirus (HERV) in human breast cancer. Methods: Primers specific for MMTV sequence are applied for PCR to amplify the homologous sequence in breast cancer tissues from 30 patiens and tumor cell lines. A RT-PCR method is also used to learn the transcription of the retovirus in vitro. 4 Isolates from the patiens are sequenced and aligned to human genome. The copy abundance of one retroelement, which is found in breast cancer, is determined by real time PCR before and after synchronization of cell cycle in MCF-7 cell line respectively. HERV-W env sequence is cloned into a pcmv-flag4 vector to produce flag fusion protein, and is detected by western blot. Results: PCR products of all samples in this study have a low homologous (40%~50%) to MMTV env. Through sequencing and alignment, we find the sequence here is linked to human retroelements (including LINEs SINEs and HERVs) in the genome, a miRNA precursor stem-loop located downstream in the vicinity of this sequence . And its copy number is associated with S phase of cell cycle. The HERV-W env protein fused with flag peptid can express and can be detected by western blot. Conclusions: i)At least ,there is no MMTV sequence in studied samples. ii)HERV retroelement activity is parallel with tumor proliferation, and is influenced by cell cycle. iii)Some of the HERVs remain active, producing proteins in cell. It provide a clue to demonstrate relationship between HERV and tumorigenesis.