Further immunohistochemical (IHC) characterisation of devil facial tumour disease 1 (DFT1) in the Tasmanian Devil (Sarcophilus harrisii)

As a veterinary histologist at Tasmania's Animal Health Laboratory, Department of Primary Industries, Parks, Water and Environment (DPIPWE), I am positioned to respond to any emerging biosecurity risk. It was incomprehensible in 2002 to foresee how sectioning and staining the first of an extraordinary number of Tasmanian devil tumours would influence my professional life as a medical scientist. Tasmanian devil numbers plummeted and the likelihood of losing Tasmania's iconic marsupial to 'Devil Facial Tumour Disease' (DFTD) became clearly evident. Research into the aetiology of the transmissible cancer became paramount. I was a co-author on two initial papers by Richmond Loh et al. describing the immunohistochemistry and pathology of DFTD followed by a broader paper by Stephen Pyecroft et al. integrating the histopathology, cytogenetics and epidemiology of this unusual transmissible tumour. Our immunohistochemical research continued to investigate tissue specific markers that define DFTD and its transmissible nature. I dovetailed my research at the Animal Health Laboratory through graduate research at the University of Tasmania where I secured two research grants offered by 'Save the Tasmanian Devil Program' (STDP), funding crucial to advancing our research findings. During my candidature, I have tested and validated over 150 commercially available anti-human antibodies on Tasmanian devil (marsupial) tissues, unfortunately sequence homology was not always one hundred percent with approximately half failing to recognise marsupial protein sequences. DFTD is a clonally evolved tumour of Schwann cell origin affecting Tasmanian devils (Sarcophilus harrisii) and is transferred by biting. This thesis presents my research as two major chapters. Firstly, a very comprehensive immunohistochemical approach investigating neural crest derived Schwann cell and melanocyte associated markers. These findings are novel and will contribute significantly to the understanding of the pathobiology of this unusual tumour. I have prepared the following manuscript pending submission, presented in chapter 1. Devil Facial Tumour 1 (DFT1) Immunophenotype Reveals a Progenitor-Like Cell with Schwann cell, Melanocyte and Self-Renewal Characteristics. In addition to gene and protein expression by DFTD, I wanted my immunohistochemical research findings to be applied in a practical way. I identified ERBB3 as a biomarker that can be utilised in both the early detection of DFTD and the identification of potential therapeutic regimes that could be applied therapeutically to wild Tasmanian devils to eradicate this disfiguring and terminal disease. This article was published in 2017 (chapter 2) ahead of the main body of my research (chapter 1) to expedite modes of DFT1 treatment, prevention and eradication which is a high priority of the STDP. ERBB3: A potential serum biomarker for early detection and therapeutic target for devil facial tumour 1 (DFT1). In summary, my research has comprehensively redefined the immunophenotype of DFTD, expressing novel proteins not available in the current literature. I show divergent origins of DFTD, a progenitor like cell with Schwann cell and melanocyte lineages, self-renewal characteristics that contributes to MHC down regulation and therefore enhanced transmissibility. I describe for the first time the histomorphology of the 5 strains of DFTD and extensively immunohistochemically stain these strains to determine any variation present. My findings are drafted for imminent manuscript submission. From my research, I published the first description of the expression of ERBB3 by DFTD and its possible early detection and possible therapeutic approach. I also first reported the expression of ERBB3 in cutaneous lymphoma in Tasmanian devils. It is reassuring that two subsequent publications, like ourselves, found ERBB3 to be important in DFTD tumourigenesis. As unbelievable as it seems researching a transmissible tumour in Tasmanian devils, it would be inconceivable to think I would be involved in a second transmissible tumour however, this is exactly what has happened. At DPIPWE I was involved in the Histology and immunohistochemistry of this newly described Tasmanian devil tumour. During my candidature I collaborated with fellow Tasmanian devil researchers Ruth Pye et al. and Max Stammnitz et al. through STDP by providing histological and immunohistochemical components of the research defining this second devil facial tumour. Our research findings have therefore renamed the original DFTD as DFT1, with the newly described tumour named DFT2, its intention to avoid confusion in the literature. My contribution to DFT2 is outlined in chapter 3 of my thesis. My future directions are to publish unfinished immunohistochemical work completed during my candidature and continue researching DFT1 and DFT2 by collaboration with Tasmanian devil researchers as well as continue histological and immunohistochemical support at the Animal Health Laboratory, DPIPWE.