From viruses to cancer stem cells: Dissecting the pathways to malignancy

Veterinary oncology: Biology, big data and precision medicine

Despite significant advances in both the understanding and the treatment of cancer, the disease remains one of high mortality and morbidity causes in all species. Increases in survival times in human cancer have increased significantly in the past 25 years but most of these increases have been through small incremental changes. For some cancers, e.g. pancreatic cancer, survival times have not increased significantly in over 100 years. In veterinary oncology, there have been major shifts in the management of cancer in companion animals. Increased availability of specialist centres, coupled with changing attitudes in owners and veterinarians, have meant improvements in veterinary cancer care borne from market pressures and increased awareness and understanding. In this review the changing face of cancer biology over the past 25 years will be examined, and the barriers to clinical progress in veterinary medicine considered. Finally, an optimistic view of the future will be presented with the prospect of greater control over this devastating disease.

Inflammation and cancer: till death tears them apart

Advances in biotechnology have enabled the collection of an immeasurable amount of information from genomic, transcriptomic, metabolomic and proteomic studies of tumours within their microenvironments. The dissection of cytokine and chemokine networks has provided new clues to the interactions between cancer cells and their surrounding inflammatory landscape. To bridge the gap between chronic inflammation and cancer, dynamic participants in the tumour microenvironment have been identified, including tumour-associated macrophages (TAMs) and regulatory T cells (Tregs). Both of these cell types are notable for their ability to cause immunosuppressive conditions and support the evasion of tumour immune surveillance. It is clear now that the tumour-promoting inflammatory environment has to be included as one of the major cancer hallmarks. This review explores the recent advances in the understanding of cancer-related inflammation and how this is being applied to comparative oncology studies in humans and domestic species, such as the dog.

Advances in the management of skin cancer

Skin cancer is one of the most commonly diagnosed cancers in the world today in both humans and our pet population. Advances in molecular techniques are now affording us an opportunity to develop therapeutics targeted at specific cancer-related cellular pathways. However, despite progress in conventional treatments, such as chemotherapy and radiation, and the new targeted therapies, some cancers, such as melanoma and cutaneous lymphoma, continue to cause significant mortality and morbidity. This short synopsis is not complete but is aimed at providing an insight into current advanced treatments and horizon therapies for cutaneous malignancies in dogs and cats with comparative aspects.

Identification of tumour initiating cells in feline head and neck squamous cell carcinoma and evidence for gefitinib induced epithelial to mesenchymal transition

Feline oral squamous cell carcinoma is considered a highly invasive cancer that carries a high level of morbidity. Despite aggressive surgery, patients often succumb to disease, the tumour having inherent insensitivity to radiation and chemotherapy. In this study we sought to identify cells within the feline SCC1 line that have stem cell properties, including inherent resistance mechanisms. When feline cells were subjected to harsh growth conditions, they formed sphere colonies consistent with a stem cell phenotype. Utilising CD133, we were able to identify a small fraction of cells within the population that had enhanced sphere-forming ability, reduced sensitivity to radiation and conventional chemotherapy and demonstrated resistance to the EGFR-targeting drug, gefitinib. In addition, long-term culture of feline SSC1 cells in gefitinib caused a change in cell morphology and gene expression reminiscent of an epithelial to mesenchymal transition. Taken together, these results suggest that feline SCC may be driven by small subset of cancer stem cells.

Systems biology approaches and tools for analysis of interactomes and multi-target drugs

Systems biology is essentially a proteomic and epigenetic exercise because the relatively condensed information of genomes unfolds on the level of proteins. The flexibility of cellular architectures is not only mediated by a dazzling number of proteinaceous species but moreover by the kinetics of their molecular changes: The time scales of posttranslational modifications range from milliseconds to years. The genetic framework of an organism only provides the blue print of protein embodiments which are constantly shaped by external input. Indeed, posttranslational modifications of proteins represent the scope and velocity of these inputs and fulfil the requirements of integration of external spatiotemporal signal transduction inside an organism. The optimization of biochemical networks for this type of information processing and storage results in chemically extremely fine tuned molecular entities. The huge dynamic range of concentrations, the chemical diversity and the necessity of synchronisation of complex protein expression patterns pose the major challenge of systemic analysis of biological models. One further message is that many of the key reactions in living systems are essentially based on interactions of moderate affinities and moderate selectivities. This principle is responsible for the enormous flexibility and redundancy of cellular circuitries. In complex disorders such as cancer or neurodegenerative diseases, which initially appear to be rooted in relatively subtle dysfunctions of multimodal physiologic pathways, drug discovery programs based on the concept of high affinity/high specificity compounds ("one-target, one-disease"), which has been dominating the pharmaceutical industry for a long time, increasingly turn out to be unsuccessful. Despite improvements in rational drug design and high throughput screening methods, the number of novel, single-target drugs fell much behind expectations during the past decade, and the treatment of "complex diseases" remains a most pressing medical need. Currently, a change of paradigm can be observed with regard to a new interest in agents that modulate multiple targets simultaneously, essentially "dirty drugs." Targeting cellular function as a system rather than on the level of the single target, significantly increases the size of the drugable proteome and is expected to introduce novel classes of multi-target drugs with fewer adverse effects and toxicity. Multiple target approaches have recently been used to design medications against atherosclerosis, cancer, depression, psychosis and neurodegenerative diseases. A focussed approach towards "systemic" drugs will certainly require the development of novel computational and mathematical concepts for appropriate modelling of complex data. But the key is the extraction of relevant molecular information from biological systems by implementing rigid statistical procedures to differential proteomic analytics.

Cancer stem cells and telomerase as potential biomarkers in veterinary oncology

Despite advances in chemotherapy and radiotherapy, cancer remains a disease of high morbidity and mortality in domestic animals. In parallel to the development of novel therapeutic interventions, appropriate biomarkers are required to detect early-stage disease and disease remission and relapse at both gross and molecular levels, and the effectiveness of therapy. The field of cancer pathogenesis has grown exponentially over the last decade, both in terms of our understanding of the underlying molecular events, and the technologies available to interrogate the cancer cell. This paper reviews the role of the telomerase enzyme and of telomere length as potential biomarkers in cancer. Furthermore, the potential role of cancer stem cells as biomarkers of malignancy and disease progression is assessed.

Using naturally occurring tumours in dogs and cats to study telomerase and cancer stem cell biology

The recently described cancer stem cell theory opens up many new challenges and opportunities to identify targets for therapeutic intervention. However, the majority of cancer related therapeutic studies rely upon rodent models of human cancer that rarely translate into clinical success in human patients. Naturally occurring cancers in dogs, cats and humans share biological features, including molecular targets, telomerase biology and tumour genetics. Studying cancer stem cell biology and telomere/telomerase dynamics in the cancer bearing pet population may offer the opportunity to develop a greater understanding of cancer biology in the natural setting and evaluate the development of novel therapies targeted at these systems.