In 1911, German gynecologist Prof. Otto Aichel proposed that metastasis occurs following leucocyte-tumor cell fusion and hybrid formation. In this, Aichel not only provided an explanation for metastasis but he also foresaw the science of cancer epigenetics. His idea that a new hybrid cell would form with characteristics of both “mother cells” in today’s terminology would refer to gene expression patterns from both fusion partners in the same hybrid cell. At least some hybrids would express the leukocytic traits of motility, chemotaxis, and homing along with the de-regulated cell division of the cancer cell. This concept has now been confirmed in numerous animal models and, from our group, in three patients with melanoma and two with renal cell carcinoma. Several other labs have now contributed to this rapidly growing field. Here, we review the findings to date as well as provide a contextualization of the works and life of Prof. Aichel.

Metastasis, Cancer, Leukocyte–cancer cell fusion, Macrophages