The Tasmanian devil (Sarcophilus harrisii), the largest living marsupial carnivore, has been threatened with extinction due to the lethal transmissible cancer Devil Facial Tumour Disease (DFTD). The disease is caused by a clonal cancer cell allograft which is transmitted by biting. DFTD is characterised by tumour growth on facial, oral and neck regions of the host, with infected devils dying within 12 months after clinical evidence of infection. The only available method of diagnosis is detection of macroscopic tumours and confirmation in the laboratory using immunohistochemistry of tumour biopsies. The lack of a pre-clinical diagnostic test is a limitation in understanding transmission dynamics and proposing management actions.
A potential biomarker for DFTD is tumour derived exosomes, the nanosized extracellular vesicles produced by most cell types under both physiological and pathological conditions, especially by tumour cells. Tumour exosomes have been found in various biological fluids including blood plasma, and they contain molecules from their parental cells, opening a door for the use of exosomes as a liquid biopsy. Tumour derived exosomes may play a role in metastasis, angiogenesis and modulation of the immune system.
This study characterises a quantitative and qualitative proteomic analysis of exosomes derived from different DFT cells lines, with the key finding of expression of proteins known to be involved in metastasis and immune suppression. Additionally, we report the protein expression profile of plasma exosomes from healthy and diseased wild devils, showing clear differences between them. The results offer promise for a preclinical diagnostic test and prognosis biomarker for examining DFTD progression and immunity in wild devil populations. Finally, the findings of this study have important implications both for conservation of Tasmanian devils and in the broader context of disease and cancer in wildlife and general veterinary medicine.