Immune Surveillance and Evasion of Senescent Cells: New Therapeutic Frontiers in Cancer and Aging
核心洞察
Cellular senescence acts as a double-edged sword in cancer (搜索), serving as both a barrier to malignant transformation and a driver of disease progression through the senescence-associated secretory phenotype (SASP).
Recent studies reveal that senescent cells can evade immune clearance through multiple mechanisms, including PD-L1 (搜索)/PD-L2 (搜索) upregulation, HLA-E (搜索)-mediated inhibition, and immunosuppressive microenvironment remodeling.
Novel therapeutic strategies such as senolytic CAR T cells, senolytic vaccination, and immune checkpoint blockade are showing promise in reversing senescence-associated pathologies in preclinical models.
Cellular senescence has emerged as one of the most complex and clinically significant phenomena in cancer (搜索) biology, simultaneously functioning as a tumor-suppressive barrier and a potential driver of malignancy. A comprehensive review published in Nature Reviews Immunology synthesizes decades of research on how senescent cells interact with the immune system, revealing a nuanced landscape where immune surveillance and immune evasion exist in delicate balance—with profound implications for cancer therapy, aging, and age-related diseases.
The foundational discovery that senescent cells can be cleared by the immune system traces back to seminal work by Xue et al. in 2007, which provided some of the first evidence that p53-restored senescent cells undergo immune-mediated clearance in murine liver carcinomas. This finding opened an entirely new dimension in senescence biology, establishing that the fate of senescent cells is not merely cell-intrinsic but depends critically on their recognition and elimination by the immune system.
The Senescence-Associated Secretory Phenotype: A Double-Edged Sword
Central to understanding senescence immunobiology is the senescence-associated secretory phenotype (SASP), first characterized by Coppé et al. in 2008. The SASP encompasses a complex repertoire of secreted factors—including pro-inflammatory cytokines, chemokines, growth factors, and matrix metalloproteinases—that mediate the non-cell-autonomous functions of senescent cells. While the SASP can reinforce senescence in an autocrine manner and recruit immune effectors for senescent cell clearance, it can also paradoxically promote chronic inflammation, immunosuppression, and tumor progression.
The composition of the SASP is not static. Hoare et al. demonstrated in 2016 that NOTCH1 (搜索) mediates a switch between two distinct secretomes during senescence, revealing a previously unrecognized temporal regulation of the SASP. More recently, Wang, Han, Elisseeff, and Demaria provided a comprehensive framework for understanding the physiological and pathological implications of the SASP in a 2024 review, underscoring its context-dependent duality.
Immune Surveillance: Mechanisms of Senescent Cell Recognition and Clearance
Multiple immune effector populations participate in senescent cell surveillance. Natural killer (NK) cells play a particularly prominent role. Sagiv et al. demonstrated that NKG2D ligands mediate immunosurveillance of senescent cells, while Iannello et al. showed that p53-dependent chemokine production by senescent tumor cells supports NKG2D-dependent tumor elimination by NK cells. Ruscetti et al. further established that NK cell-mediated cytotoxicity contributes to tumor control by cytostatic drug combinations.
CD4+ T cells have also emerged as critical mediators of senescence surveillance. In a landmark 2023 study, Hasegawa et al. provided evidence that cytotoxic CD4+ T cells eliminate senescent cells by targeting cytomegalovirus antigen, demonstrating that naturally occurring senescent cells in human aged skin are surveilled by the immune system. Elyahu et al. recently showed in 2025 that CD4 T cells acquire eomesodermin to modulate cellular senescence and aging, while Li et al. demonstrated that CD4+ T cells eliminate senescent prostate epithelium to delay progression of benign prostatic hyperplasia.
Macrophages contribute to senescent cell clearance in specific contexts. Egashira et al. showed that F4/80+ macrophages contribute to clearance of senescent cells in the mouse postpartum uterus, and Brighton et al. demonstrated that uterine natural killer cells clear senescent decidual cells in cycling human endometrium.
Immune Evasion: How Senescent Cells Escape Clearance
Despite these surveillance mechanisms, senescent cells can persist and accumulate, particularly during aging and in cancer (搜索). Multiple immune evasion strategies have now been identified. Pereira et al. reported in 2019 that senescent cells evade immune clearance via HLA-E (搜索)-mediated NK and CD8+ T cell inhibition. The PD-1/PD-L1 (搜索) axis has emerged as a critical checkpoint: Wang et al. provided some of the first evidence in 2022 that blocking PD-L1–PD-1 improves senescence surveillance and aging phenotypes. Majewska et al. subsequently demonstrated in 2024 a p16-dependent increase of PD-L1 stability that regulates immunosurveillance of senescent cells.
Chaib et al. revealed in 2024 that the efficacy of chemotherapy is limited by intratumoral senescent cells expressing PD-L2 (搜索), while Ontiveros et al. showed that anti-PD-L2 immunotherapy is efficacious against melanoma (搜索) in aged hosts through IL-17 and IFNγ signaling. Additional evasion mechanisms include the upregulation of CD47 (搜索)-QPCT/L axis to suppress macrophage-mediated corpse removal, as shown by Schloesser et al., and mitochondrial DNA release by senescent tumor cells that enhances PMN-MDSC-driven immunosuppression through the cGAS-STING (搜索) pathway, as demonstrated by Lai et al. in 2025.
Therapeutic Strategies: Senolytics, Senomorphics, and Immunotherapy
The therapeutic implications of senescence immunobiology are vast. Amor et al. pioneered the development of senolytic CAR T cells in 2020, demonstrating their ability to reverse senescence-associated pathologies. The same group later showed in 2024 that these CAR T cells provide prophylactic and long-lasting efficacy against age-related metabolic dysfunction. Yang et al. developed NKG2D-CAR T cells that eliminate senescent cells in aged mice and nonhuman primates, while Eskiocak et al. recently reported anti-uPAR (搜索) CAR T cells that reverse and prevent aging-associated defects in intestinal regeneration.
Senolytic vaccination represents another innovative approach. Yoshida et al. developed a CD153 vaccine as a senotherapeutic option for preventing the accumulation of senescent T cells, and Suda et al. demonstrated that senolytic vaccination improves age-related phenotypes and increases lifespan in progeroid mice.
The intersection of senescence and cancer (搜索) immunotherapy continues to yield important insights. Marin et al. characterized the immunogenicity of senescent cells and their potential as anticancer vaccines, while Chen et al. explored how senescence modulates IFNγ sensing and antigen presentation by tumor cells. Chibaya et al. showed that EZH2 (搜索) inhibition remodels the inflammatory SASP to potentiate pancreatic cancer (搜索) immune surveillance.
Biomarkers and Clinical Translation
A major challenge for the field remains the identification and validation of robust senescence biomarkers. As noted in the Frontiers Research Topic on cellular senescence in cancer (搜索), significant knowledge gaps persist regarding the context-dependent duality of senescence and the mechanisms by which SASP mediates both immune clearance and immune suppression. The development of immunohistochemistry panels, multiplex assays, transcriptomic and proteomic signatures, circulating markers, and extracellular vesicle analyses are all priorities for advancing senescence-targeted therapies into clinical trials.
The scope of ongoing research spans early lesions, post-neoadjuvant residual disease, metastatic progression, and recurrence risk—underscoring the pervasive influence of senescence across the cancer (搜索) continuum. As the field moves forward, spatial and single-cell methodologies will be essential for mapping senescence and immune interactions in situ, enabling the rational design of combination therapies that harness or mitigate senescence in a precision medicine framework.