Comment on: ‘Guidelines for the use of cell lines in biomedical research’: human-to-human cancer transmission as a laboratory safety concern

The guidelines for using cell lines in biomedical research, published recently in BJC (Geraghty et al, 2014), include a pioneering safety warning about human-to-human cancer transmission through cancer cells, a route that we will call extracorporeal metastasis (XM). Because XM has been tacitly dismissed as implausible in everyday laboratory practice, if considered at all, we emphasise the warning by reviewing the underlying evidence and preventive measures. The possibility of XM was suggested 50 years ago (Bloom et al, 1951) and confirmed by finding tumours that are transplantable in outbred mice (Eiselein and Biggs, 1970; Fidler et al, 1981). In wild animals, XM has been documented for dogs (Murgia et al, 2006; Rebbeck et al, 2009; Belov, 2011), in which cancer is sexually transmitted (Rebbeck et al, 2009), and Tasmanian devils, in which it is passed by biting (Murchison et al, 2012). Although the devils are highly inbred, dogs are not, implying that transmitted cancer cells evade the immune response. Indeed, they do so through the loss of major histocompatibility complex proteins, thus preventing humoral immune response, and b