Wildlife cancer: a conservation perspective

Abstract

Until recently, cancer in wildlife was not considered to be a conservation concern. However, with the identification of Tasmanian devil facial tumour disease, sea turtle fibropapillomatosis and sea lion genital carcinoma, it has become apparent that neoplasia can be highly prevalent and have considerable effects on some species. It is also clear that anthropogenic activities contribute to the development of neoplasia in wildlife species, such as beluga whales and bottom-dwelling fish, making them sensitive sentinels of disturbed environments.

Figure 1. Proposed mechanism of BaP small intestinal carcinogenesis in beluga whales.

Environmental exposure to the procarcinogen benzo[a]pyrene (BaP) is thought to have a role in the high incidence of small intestinal neoplasia in beluga whales in the St Lawrence River Estuary. The proposed mechanism involves intestinal exposure through ingestion of contaminated prey items and sediment followed by induction of cytochrome P450 1A1 (CYP1A1) in small intestinal epithelial cells. CYP1A1 is responsible for oxidation and metabolism of BaP to the carcinogen (BaP 7,8 diol 9,10 epoxide). The activated carcinogen preferentially binds DNA at the exocyclic nitrogen of the guanine residue, which is required for base pairing, resulting in the potential for G → T transversion during DNA replication and disruption of tumour suppressors or proto-oncogenes.