Cancer Vaccines: Toward the Next Breakthrough in Cancer Immunotherapy

Figure 2

Classification of tumors by immune cell infiltration. Tumor types can be classified by the level of immune cell infiltration into tumors. “Cold tumor,” characterized by the poor infiltration of immune cells, is reported to be one of the reasons why immune checkpoint inhibitors are ineffective. Contrastingly, a “hot tumor” is characterized by the abundant infiltration of immunocompetent cells, showing good responses to immune checkpoint inhibitors. Recently, aggregated infiltration of immune cells, known as the tertiary lymphoid structure (hot tumor, type B), has gained increasing attention compared to separated infiltration of immune cells (hot tumor, type A).