We have reviewed the evidence relevant to mouse mammary tumour viruses (MMTV) and human breast cancer. The prevalence of MMTV- like gene sequences is 15-fold higher in human breast cancer than in normal human breast tissue controls and is present in up to 40% of human breast cancers. MMTV-like gene sequences can be identified in benign breast tissues 1–11 years before the development of positive MMTV-like breast cancer in the same women. The prevalence of MMTV antibodies in sera from women with breast cancer is 5-fold higher than in normal women. MMTV can infect human breast epithelial cells and integrate at random into the human genome located in those cells. MMTV-like gene sequences are present in human milk from normal lactating women and with increased prevalence in milk from women at risk of breast cancer. MMTV-like virus associated human breast cancer has strikingly similar features to MMTV-associated mouse mammary tumours. These features include almost identical nucleotide sequences and structure of the MMTV genome, histology, superantigen expression, MMTV infection of B and T lymphocytes and hormone dependence. MMTV-like gene sequences have also been identified in dogs, cats, monkeys, mice and rats. Saliva has been identified as the most plausible means of transmission from human to human and possibly from dogs to humans. The evidence meets the classic causal criteria. A causal role for MMTV-like viruses in human breast cancer is highly likely.

我们回顾了与小鼠乳腺肿瘤病毒（MMTV）和人类乳腺癌相关的证据。 MMTV 样基因序列在人类乳腺癌中的患病率比正常人乳腺组织对照高 15 倍，并且存在于高达 40% 的人类乳腺癌中。在同一女性中，在发生阳性 MMTV 样乳腺癌之前 1-11 年，可以在良性乳腺组织中鉴定出 MMTV 样基因序列。乳腺癌女性血清中 MMTV 抗体的患病率是正常女性的 5 倍。 MMTV 可以感染人类乳腺上皮细胞，并随机整合到这些细胞中的人类基因组中。类似 MMTV 的基因序列存在于正常哺乳期妇女的母乳中，并且在有乳腺癌风险的妇女的母乳中患病率更高。 MMTV 样病毒相关的人类乳腺癌与 MMTV 相关的小鼠乳腺肿瘤具有惊人相似的特征。这些特征包括MMTV基因组几乎相同的核苷酸序列和结构、组织学、超抗原表达、B和T淋巴细胞的MMTV感染以及激素依赖性。在狗、猫、猴子、小鼠和大鼠中也发现了类似 MMTV 的基因序列。唾液已被认为是人与人之间、甚至狗与人之间最可能的传播方式。证据符合经典的因果标准。 MMTV 类病毒极有可能与人类乳腺癌发生因果关系。