Comparative oncology: overcoming human cancer through companion animal studies

Abstract

Comparative oncology is a field of study that has been recently adopted for studying cancer and developing cancer therapies. Companion animals such as dogs can be used to evaluate novel biomarkers or anticancer targets before clinical translation. Thus, the value of canine models is increasing, and numerous studies have been conducted to analyze similarities and differences between many types of spontaneously occurring cancers in canines and humans. A growing number of canine cancer models as well as research-grade reagents for these models are becoming available, leading to substantial growth in comparative oncology research spanning from basic science to clinical trials. In this review, we summarize comparative oncology studies that have been conducted on the molecular landscape of various canine cancers and highlight the importance of the integration of comparative biology into cancer research.

Fig. 1. Schematic diagram outlining the cancer disease model.

Cancer can be interpreted as a genetic disease, a metabolic disease, and an immune disease.

Fig. 2. Limitations in current cancer research.

There are still limitations to overcoming cancer for the following reasons: limitations regarding targeting of cancer stem cells (CSCs), anticancer drug immunity due to drug resistance of cancer stem cells, lack of cancer epigenetic profiles and specificity of existing epi-drugs, treatment difficulties due to problems related to cancer diagnosis, lack of effective biomarkers for cancer diagnosis and prognosis, limitations of conventional chemotherapeutic agents, and problems in treating cancer metastasis.

Fig. 3. Schematic diagram outlining comparative medicine in companion animals and humans.

Companion animals and humans share very similar living environments, exposing both species to similar toxic substances, viruses, and/or pollution. From these external stimuli, companion animals and humans develop cancer from genetic/epigenetic alterations, metabolic changes, and/or immune-related changes.

Fig. 4. Comparison of human breast cancer and canine mammary gland tumor features.

Canine mammary cancers (left panel) are typically categorized by histological subtype. On the other hand, human breast cancers (right panel) are usually categorized based on the presence or absence of hormone receptors. Numerous molecular and signaling pathway alterations (middle panel) are observed in both canine and human species.