Figure 1. Relationship between primary resistance, acquired resistance, adaptive resistance and immuno-escape when undergoing immunotherapy. According to the resistance mechanisms, primary and acquired resistance result from the changes of both tumor cells and the TME, but adaptive resistance is only limited to the latter. In terms of clinical features, adaptive resistance shows the same characteristics as primary resistance or acquired resistance. Immune escape leads to the same outcome as drug resistance, but due to these clones lack drug targets, this type of resistance should not be regarded as a real drug resistance. TME: tumor microenvironment. The red arrow indicates the evolution of immune state from sensitivity to drug resistance, which corresponds to the state of acquired resistance and primary resistance when immunotherapy is used.