The process of entosis is not widely known phenomenon, that can impact diagnosis and prognosis of cancer. The phenomenon is characterized by the active invasion of one cell into another and the formation of “cell in cell structures” (CIC), with the participation of Rho-ROCK kinase and actin-myosin complexes. Clinical studies show that the presence of CIC can result in worse prognosis. This process may be also important in the biology of cancer since more malignant tumors, under conditions of starvation, hypoxia and metastasis, show a higher percentage of entoses. Several molecular agents involved in entosis process like Aurora A Kinase, CDC42, Atg5, Atg7, LC3, mTOR are identified. Little is known about triggering factors of entosis, why some tumors demonstrate CIC and the other (also of the same type), not. Studying of entosis is also challenging: the dynamics of cell in cell invasion can be observed in cell culture, while the post-operative cancer tissue represent some fixated stage like the “still nature”, where dynamic studies are impossible.
Despite these difficulties, we know quite lot about the phenomenon and its possible impact on cancer prognosis and diagnosis. In the research on entosis we need introduction of international standards and unification in distinguishing entosis from other processes, compilation of cell culture studies with histopathological studies. The first definition of entosis implicated that it is a new cell death since most entotic cells in that experiments died within lysosome of the host cell. Other data, including clinical ones, indicate that entosis process can be beneficial for tumor cells: supporting their survival, gain of nutrients and promoting more genetically instable cancer cells. Summarizing, it is good to consider once again what is entosis: death or survival. Especially in the context of clinical cancer biology.