Salivary Biomarkers in Breast Cancer: From Salivaomics to Salivaoncoomics.

Saliva is a promising biological fluid for the diagnosis and monitoring of diseases, including breast cancer. To study the composition of saliva, a complex of "omics" technologies is used: genomics, transcriptomics, proteomics, metabolomics and microbiomics. In this review, we systematized all known "omics" in their application to saliva analysis in breast cancer in order to understand how complete the picture is provided by the combination of different areas of research and to identify missing links. It has been shown that studies of saliva in breast cancer are chaotic and unsystematic. Inconsistency of sample sizes and high heterogeneity of breast cancer were identified. The main tasks that need to be solved for the complete and harmonious development of salivaomics in a new direction-"salivaonkoomics" are formulated. Thus, it is necessary to systematize and unify the study of biomarkers within each area of "omics", including sample size and its homogeneity, a list of methods and approaches, a list of biomarkers, reproducibility of results, and the ability to transfer results to other samples. It is important to expand the number of components of "omics" by adding new methods (for example, spectralomics, etc.), as well as studying the relationships between different "omics" technologies (interactomics). All this together will allow the study of saliva not only in breast cancer but also in many other pathologies to a qualitatively new level.