Abstract
In many animal species, chemical communication plays a major role in interactions between individuals, both at the intraspecific and interspecific levels (sexual selection, competition, predation, etc.). Although it is known that many pathologies are associated with changes in body odour, little work has been done on the ecological and evolutionary consequences of these phenomena. Moreover, most research on this subject concerns infectious diseases, suggesting for example an avoidance of contagion between individuals, but much more rarely cancers. This thesis aims to better understand how cancer processes (from pre-cancerous lesions to metastatic cancers) influence interactions between individuals through the changes in body odour that they cause. To conduct our research, we used a biological host/cancer model: the mouse/lung cancer. In addition to clarifying the role of cancer-associated odours in inter-organism interactions, this research project also aimed to identify the stage of cancer development at which olfactory changes are observable, with the applied objective of identifying possible early cancer biomarkers of medical relevance. On the applied side, we were able to observe odour changes very early in the development of the disease, from the onset of precancerous lesions, and several potential biomarker compounds were identified. Our results thus indicate that lung cancer in mice alters body odours early on, and that these can be detected both by chemical analysis and by using healthy mice as noses. These findings open up new research perspectives in the medical field. Regarding the impact of cancer on the behaviour of healthy conspecifics, our results suggest that the disease does not seem to play a role in the preferences of female mice, contrary to what is generally observed in the context of parasitism. This new field of study, which brings together chemical ecology and cancer, is only just beginning and many questions remain to be answered, particularly with regard to other interactions such as prey-predator, or in the case of transmissible cancers such as in the Tasmanian devil. This thesis opens up numerous research perspectives, both in the medical field and in fundamental biology.