The article discusses tumor-intrinsic resistance to immune checkpoint blockade (ICB), which refers to the ability of tumors to resist the effects of ICB therapies despite the presence of immune cells that could potentially attack the tumor. Tumor-intrinsic resistance is influenced by factors within the tumor itself, such as genetic and functional characteristics of the tumor cells. Key mechanisms of resistance include insufficient tumor antigenicity, impaired interferon-γ (IFNγ) signaling, and loss of major histocompatibility complex (MHC) class I expression. Tumors with poor antigenicity are less likely to respond to ICB, while those with high antigenicity, such as those with microsatellite instability, are more likely to respond. IFNγ signaling is crucial for tumor antigen presentation and PD-L1 expression, and disruptions in this pathway can lead to resistance. Tumor-intrinsic loss of MHC class I expression allows tumors to evade immune surveillance. Additionally, oncogenic signaling pathways such as WNT-β-catenin, CDK4-CDK6, and MAPK can contribute to resistance by promoting immunosuppressive environments. BRAF-V600E mutations in melanoma can also lead to resistance by increasing immunosuppressive cytokines. PTEN loss is another factor that can lead to resistance by impairing IFNγ signaling. Biomarkers such as PD-L1 expression can indicate the presence of IFNγ signaling, but their expression does not always correlate with response to ICB. Tumor neoantigens are important targets for immune responses, but their presence is not sufficient for a response to ICB. Strategies to overcome tumor-intrinsic resistance include enhancing antigen presentation, inducing immunogenic cell death, and using combination therapies with other immunotherapies or chemotherapy. Approaches such as oncolytic viruses, pattern recognition receptor agonists, and genetic modifications to enhance immune responses are being explored. Overall, understanding the molecular mechanisms of tumor-intrinsic resistance is crucial for developing more effective ICB therapies.The article discusses tumor-intrinsic resistance to immune checkpoint blockade (ICB), which refers to the ability of tumors to resist the effects of ICB therapies despite the presence of immune cells that could potentially attack the tumor. Tumor-intrinsic resistance is influenced by factors within the tumor itself, such as genetic and functional characteristics of the tumor cells. Key mechanisms of resistance include insufficient tumor antigenicity, impaired interferon-γ (IFNγ) signaling, and loss of major histocompatibility complex (MHC) class I expression. Tumors with poor antigenicity are less likely to respond to ICB, while those with high antigenicity, such as those with microsatellite instability, are more likely to respond. IFNγ signaling is crucial for tumor antigen presentation and PD-L1 expression, and disruptions in this pathway can lead to resistance. Tumor-intrinsic loss of MHC class I expression allows tumors to evade immune surveillance. Additionally, oncogenic signaling pathways such as WNT-β-catenin, CDK4-CDK6, and MAPK can contribute to resistance by promoting immunosuppressive environments. BRAF-V600E mutations in melanoma can also lead to resistance by increasing immunosuppressive cytokines. PTEN loss is another factor that can lead to resistance by impairing IFNγ signaling. Biomarkers such as PD-L1 expression can indicate the presence of IFNγ signaling, but their expression does not always correlate with response to ICB. Tumor neoantigens are important targets for immune responses, but their presence is not sufficient for a response to ICB. Strategies to overcome tumor-intrinsic resistance include enhancing antigen presentation, inducing immunogenic cell death, and using combination therapies with other immunotherapies or chemotherapy. Approaches such as oncolytic viruses, pattern recognition receptor agonists, and genetic modifications to enhance immune responses are being explored. Overall, understanding the molecular mechanisms of tumor-intrinsic resistance is crucial for developing more effective ICB therapies.