Cells capable of starting the track towards cancer are probably abundant in an organism, but the likelihood of any of these cells to evolve to a deadly disease is very low. This occurs in part due to several safekeeping mechanisms shaped by evolution to detect and eliminate potential cancer-forming cells, which will be defined here as endogenous anticancer mechanisms (EACMs). Virtually any cellular process has safekeeping mechanisms that detect and correct mishaps that could evolve into potentially harmful cellular behavior, but some aspects of these mechanisms seem to have been selected by evolution to protect organisms against cancer. The mechanisms that will be discussed here and in the reviews of this series are: cell senescence, DNA repair, cell cycle control, apoptosis, autophagy, block of the invasion and metastasis cascade, block of cell reprogramming and immune surveillance. Here I will present the basic features and the importance of each EACM and review the involvement of these processes in preventing cancer growth together with their importance in cancer prevention and therapeutics.