Prieto, Luis I.

Abstract Cellular senescence is a dynamic, multistage biological program that exerts context-dependent effects on tumor initiation, progression, and overall carcinogenesis. Our laboratory has previously demonstrated that the early accumulation of p16Ink4a-expressing (representing strong cyclin-dependent kinase inhibition) senescent alveolar macrophages during tumorigenesis actively facilitates tumor formation and progression by inhibiting the infiltration of cytotoxic T lymphocytes. However, considering the dynamic nature of cellular senescence, distinct senescent cell populations could express high amounts of the alternative cell cycle inhibitor p21Waf1/Cip1 independently of p16Ink4a to potentially catalyze distinct functions. To test this, we have employed transgenic p21-ATTAC (p21-driven apoptosis through targeted activation of caspase 8) mice to investigate the role of p21-expressing cells during Kras-driven adenoma formation. In agreement with our previous observations following clearance of p16-expressing senescent cells, we found that removal of p21+ cells attenuates early tumor development. Western blot and immunofluorescence analyses corroborates a reduction in p21, p16, and multiple members of a putative senescence-associated secretory phenotype (SASP). Although senescent alveolar macrophages remain a critical therapeutic target, here we found that senescent endothelial cells also exhibited elevated expression of p21, p16, and SASP with a high senolytic response. Future studies will include identifying the predominant p21-expressing senescent endothelial subpopulations and elucidating the mechanisms by which endothelial senescence contributes to lung tumorigenesis. Collectively, our findings have unveiled additional senescent cell populations with the potential to drive lung tumorigenesis. Citation Format: Yuanning Du, Luis I. Prieto, Karthikbabu Jeganathan, Cheng Zhang, Hu Li, Darren Baker. Elucidating the role of p21 + senescent cells in early-stage lung tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2268.

Abstract Geroscience research benefits from interdisciplinary approaches, team science, and collaborations, which collectively facilitate the discovery of aging mechanisms and their translation into tangible, clinical interventions. Since its inception in 2019, the Midwest Aging Consortium (MAC) has provided an engaging platform for aging researchers in the United States’ Midwest to connect, collaborate, and exchange ideas. The Sixth Annual Research Symposium of the MAC held at the Mayo Clinic in Rochester, Minnesota, in April 2025 highlighted the continued impact of the MAC in bringing together aging researchers, including many trainees and early career investigators, into a collaborative environment. This record-setting event featured interdisciplinary research on key aging mechanisms, including lipid metabolism, mitochondrial dysfunction, stress response, cellular senescence, and immune adaptations across organ systems. New therapeutic concepts and clinical trial approaches were presented. Cutting-edge methodologies including single-cell and spatial transcriptomics, metabolomics, and organoid cultures, to dissect aging process in tissue-specific and systemic contexts also were presented. Overall, the MAC symposium underscored the translational potential of geroscience and reinforced the MAC’s mission to accelerate aging research through regional collaborations and innovation.

ABSTRACT Cellular senescence is an irreversible form of cell‐cycle arrest caused by excessive stress or damage. While various biomarkers of cellular senescence have been proposed, there are currently no universal, stand‐alone indicators of this condition. The field largely relies on the combined detection of multiple biomarkers to differentiate senescent cells from non‐senescent cells. Here we introduce a new approach: unbiased cell culture selections to identify senescent cell‐specific folded DNA aptamers from vast libraries of trillions of random 80‐mer DNAs. Senescent mouse adult fibroblasts and their non‐senescent counterparts were employed for selection. We demonstrate aptamer specificity for senescent mouse cells in culture, identify a form of fibronectin as the molecular target of two selected aptamers, show increased aptamer staining in naturally aged mouse tissues, and demonstrate decreased aptamer staining when p16 expressing cells are removed in a transgenic INK‐ATTAC mouse model. This work demonstrates the value of unbiased cell‐based selections to identify new senescence‐specific DNA reagents.

ABSTRACT Cellular senescence is an irreversible form of cell-cycle arrest caused by excessive stress or damage. While various biomarkers of cellular senescence have been proposed, there are currently no universal, stand-alone indicators of this condition. The field largely relies on the combined detection of multiple biomarkers to differentiate senescent cells from non-senescent cells. Here we introduce a new approach: unbiased cell culture selections to identify senescent cell-specific folded DNA aptamers from vast libraries of trillions of random 80-mer DNAs. Senescent mouse adult fibroblasts and their non-senescent counterparts were employed for selection. We demonstrate aptamer specificity for senescent mouse cells in culture, identify a form of fibronectin as the molecular target of two selected aptamers, show increased aptamer staining in naturally aged mouse tissues, and demonstrate decreased aptamer staining when p16 expressing cells are removed in a transgenic INK-ATTAC mouse model. This work demonstrates the value of unbiased cell-based selections to identify new senescence-specific DNA reagents.

Abstract Despite progress in screening and treatment, lung cancer remains the leading cause of cancer- related deaths worldwide. An overarching issue is the complexity and heterogeneous nature of the tumor microenvironment and eventual tumor spread. While aging is a key determinant, the relationship between aging and cancer is multi-faceted and extends beyond the accumulation of mutations. Therefore, a much-needed framework integrating the mechanistic principles that change with aging to drive neoplastic transformation beyond genetics will help us uncover predictive biomarkers that inform treatment decision-making and how we may use them to prevent, postpone, suppress tumor growth, and limit spread. Here, we investigate the role of age-related senescent cell accumulation in lung tumorigenesis and propose a potential strategy to delay tumor progression and spread by selectively targeting tumor-promoting senescent cells that arise with increasing age to sustain protective antitumor immunity. Citation Format: Luis Prieto. Effects of senescence on the lung tumor microenvironment [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr A014.

Senescent cells, which accumulate with age, exhibit a pro-inflammatory senescence-associated secretory phenotype (SASP) that includes the secretion of cytokines, lipids, and extracellular vesicles (EVs). Here, we established an in vitro model of senescence induced by Raf-1 oncogene in RAW 264.7 murine macrophages (MΦ) and compared them to senescent MΦ found in mouse lung tumors or primary macrophages treated with hydrogen peroxide. The transcriptomic analysis of senescent MΦ revealed an important inflammatory signature regulated by NFkB. We observed an increased secretion of EVs in senescent MΦ, and these EVs presented an enrichment for ribosomal proteins, major vault protein, pro-inflammatory miRNAs, including miR-21a, miR-155, and miR-132, and several mRNAs. The secretion of senescent MΦ allowed senescent murine embryonic fibroblasts to restart cell proliferation. This antisenescence function of the macrophage secretome may explain their pro-tumorigenic activity and suggest that senolytic treatment to eliminate senescent MΦ could potentially prevent these deleterious effects.

Abstract A big challenge in oncology is tumor heterogeneity, as the same type of tumor can manifest differently across patients. Our current cancer therapies focus on targeting malignant cells without considering how the tumor microenvironment influence tumorigenesis or changes in response to treatment. Therefore, identifying effective therapies that restrict tumor growth and progression while restoring optimal tissue and organ function is imperative. Here, we propose a potential strategy to delay the frequency of lung tumorigenesis and reduce progression by selectively targeting tumor-promoting senescent cells that arise with advancing age, prolonging antitumor immunity. Using lung tumor-prone mice, we found that senescent cells, specifically senescent alveolar macrophages, accumulate early in hyperplastic lesions. Mechanistically, these macrophages upregulate the cell cycle regulator p16Ink4a; express the cell surface protein CXCR1; they are distinct from other established subsets; are sensitive to senolytic interventions; have a tumor-promoting secretome, including SPP1; and express immunosuppressive factors that modulate the antitumor immune response. Selective clearance of senescent macrophages attenuates adenoma development, indicating they, at least in part, promote tumorigenesis. Importantly, we observed alveolar macrophages with these properties accumulating in treatment-naive human early-stage lung adenocarcinoma in situ, indicating that the cellular senescence program in macrophages is a conserved etiology. We also found that senescent alveolar macrophages accumulate in otherwise naturally aged normal mouse lungs and their persistence correlates with increased inflammation. Collectively, our findings suggest that targeting senescent macrophages may constitute a potential therapeutic intervention to postpone or attenuate lung cancer during the early stages of the disease. Citation Format: Luis I. Prieto. Senescent macrophages drive tumorigenesis by limiting antitumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2972.

Harnessing the immunogenic potential of senescent cells may be a viable but context-dependent opportunity to boost antitumor immunity.

Cellular senescence is the dynamic process of durable cell-cycle arrest. Senescent cells remain metabolically active and often acquire a distinctive bioactive secretory phenotype. Much of our molecular understanding in senescent cell biology comes from studies using mammalian cell lines exposed to stress or extended culture periods. While less well understood mechanistically, senescence in vivo is becoming appreciated for its numerous biological implications, both in the context of beneficial processes, such as development, tumor suppression, and wound healing, and in detrimental conditions, where senescent cell accumulation has been shown to contribute to aging and age-related diseases. Importantly, clearance of senescent cells, through either genetic or pharmacological means, has been shown to not only extend the healthspan of prematurely and naturally aged mice but also attenuate pathology in mouse models of chronic disease. These observations have prompted an investigation of how and why senescent cells accumulate with aging and have renewed exploration into the characteristics of cellular senescence in vivo. Here, we highlight our molecular understanding of the dynamics that lead to a cellular arrest and how various effectors may explain the consequences of senescence in tissues. Lastly, we discuss how exploitation of strategies to eliminate senescent cells or their effects may have clinical utility.