Decoding Metastasis: From Cell Death to Fusion in Cancer Progression

Metastasis is one of the key concepts in modern oncology, which connects the movement of cancer cells in the body with changes in their characteristics and functions. The review examines the main aspects of metastasis, including theories, facts and discoveries that help to better understand this phenomenon and develop new approaches to its treatment. In this article, we also proposed the theory of cell fusion with the formation of hybrid cells as one of the factors of metastasis. We believe that the fusion of tumor cells with other types of motile cells (leukocytes and bone marrow progenitor cells) may represent an additional mechanism of tumor spread. Cells of bone marrow origin, including cells of the myeloid and macrophage lineages, are the best candidates for heterotypic fusion in regenerative conditions. Events such as cell fusion may play a role in tumor dedifferentiation and progression. We presented a number of arguments and data from our own research that speak in favor of the proposed theory. It should be noted that if the fusion of a normal cell with a tumor cell is one of the possible triggers of tumorigenesis and cancer spread, the mechanisms underlying this process may provide possible new targets for treatment. Therefore, their analysis will expand our arsenal of therapeutic tools by adding completely new targets - cell signaling molecules - and will provide the impetus for reconsidering the tumor microenvironment from a different angle.