Figure 1. . Schematic representation of the ‘3E’ theory.

Cancer immunoediting includes three sequential phases: elimination, equilibrium and escape. At the elimination phase, antigenic cancer cells can be effectively removed by immune effector cells. At the equilibrium phase, some cancer cells which have a nonimmunogenic phenotype manage to evade the immune elimination and survive. As such, a balance is established between cancer and the immune system. At the escape phase, cancer evades the immune response through more complicated mechanisms, such as downregulating antigenicity, upregulating immune inhibitory molecules and generating an immunosuppressive TME flooded with suppressive cells and factors. Cancer manages to grow in an uncontrolled manner. In the whole process of immunoediting, the accumulation of epigenetic alterations leads to profound changes in tumor cells and tumor microenvironment that contribute to decreased antitumor immunity and tumor immune escape.