The interface between ecology, evolution, and cancer: More than ever a relevant research direction for both oncologists and ecologists

Forty years ago, scientists started to describe the genetic cascade of events leading to cancer as "somatic evolution" (Cairns, 1975; Nowell, 1976). Even if the full relevance of these pioneer papers was not immediately perceived by the scientific community, they paved the way for one of the most stimulating and challenging research directions in the effort to predict cancer emergence, progression, and therapy outcomes. Evolutionary biology has indeed deeply transformed our understanding of cancer, gaining unprecedented international recognition among oncologists in the last decade (Ujvari, Roche & Thomas, 2017a). Nowadays, cancer is widely considered as a pathology that emerges due to clonal evolution and cell competition, Darwinian selection being the driver of cancer cells along selective landscapes, culminating in resistance to immune attack, malignant progression, resistance to therapies, metastasis, and even sometimes contagion between individuals and/or species (Ujvari et al., 2017b; Ujvari, Roche & Thomas,2017a). Thus, as recently proposed by Mel Greaves through paraphrasing Dobzhansky's famous dictum, "nothing in cancer makes sense except in the light of evolution" (Greaves, 2018). This interdisciplinary field of research remains at the moment extremely promising, but it is still in its infancy, and fundamental studies (both theoretical and experimental) are still needed to pursue our understanding of the evolutionary ecology of tumors and of host-tumor interactions. By assembling some of the latest, most exciting results, syntheses, and perspectives relating to the topic Ecology, Evolution and Cancer, our objective with this special issue is to reinforce the construction of a solid base for a balanced approach to cancer research, for oncologists and for ecologists.