Relation between the Presence of Mouse Mammary Tumor Virus-Like Sequences in Breast Tissues and Human Breast Cancer in Iranian Patients

Mouse mammary tumor virus (MMTV), a milk-transmitted retrovirus, is considered to be involved in the development of breast tumors in mice. Although several previous studies have identified MMTV-like sequences in human breast cancer, the presence of human endogenous retrovirus (HERs) makes these results controversial, i.e. the role of MMTV in breast cancer has never been definitely proven. In addition, various results have been reported in this regard from different countries. We selected MMTV envelope (Env) gene sequences to eliminate the effects of HERs.

In this case-control study, DNA was extracted from 59 paraffin-embedded malignant tumor tissues and 59 normal control samples. Nested polymerase chain reaction (PCR) was then used to detect MMTV Env-like sequences.

MMTV genome was detected in 19 malignant breast samples (32%) and three normal control samples (5%) (P < 0.001).

Based on our findings, MMTV can play a major role in the development of breast cancer in Iranian women. According to PCR results, the obtained sequences had 99% homology with BR6 strain of MMTV and 100% homology with GR and C3H strains.