Targeted Supramolecular Senolytics by Enzyme-Responsive Disassembly and Intracellular Polymerization.

Due to the heterogeneity of the senescent phenotype and the lack of a universal biomarker of senescence, the targeting of senescent cells is still an unresolved challenge, and the elimination of senescent cells using specific drugs (senolytics) is still limited in clinical use due to the off-target effects and associated toxicities of current therapeutic strategies. In this study, the induction of senescence in human melanoma cells by palbociclib is found to lead to a senescent phenotype characterized by overexpression of the membrane protein dipeptidyl peptidase 4 (DPP4), previously identified only in ageing contexts. Based on this discovery, a nanoparticle targeting DPP4 overexpression in the senescent surfaceome is designed, synthesized, and characterized to target senescent cancer cells. The nanoparticle based on mesoporous silica is loaded with the senolytic navitoclax, coated with disulfide-containing poly(ethylene glycol) to generate a redox-sensitive gatekeeper (S-S-PEG), and functionalized with an antibody against the DPP4 protein. The ability of the nanoparticles to effectively detect and eliminate senescent cells was confirmed in vitro and in vivo using a mouse model of palbociclib-induced senescent in melanoma. The DPP4-targeted nanoparticle effectively reduces tumor growth and selectively removes senescent cells. Taken together, this study highlights the potential of surfaceome-targeted nanoparticles, as a clinically relevant strategy for improving senolytic therapies.

Cellular senescence is a double-edged sword in cancer biology, initially acting as a tumor-suppressive mechanism but later contributing to cancer progression and therapy resistance. Senescent cells, characterized by stable cell cycle arrest, secrete a complex array of bioactive molecules known as the senescence-associated secretory phenotype (SASP), which fosters chronic inflammation, disrupts tissue architecture, and promotes tumorigenesis through paracrine signaling. Accumulation of these cells in the tumor microenvironment can enhance malignancy, drive metastasis, and impair treatment outcomes. Senotherapeutics, have emerged as promising strategies for targeting senescent cells in cancer therapy. These agents selectively induce apoptosis in senescent cells while preserving normal tissues, representing a paradigm shift in oncology. Senotherapeutics can function as standalone treatments by clearing senescent tumor cells or as adjuvants to chemotherapy and radiotherapy, effectively eliminating residual therapy-induced senescent cells that may contribute to relapse. This dual approach allows for reduced treatment toxicity, improved therapeutic efficacy, and decreased tumor recurrence. Furthermore, targeting non-cancerous senescent cells may help suppress inflammation-driven tumorigenesis, slow disease progression, and enhance patient outcomes. Despite their promise, challenges remain in optimizing senotherapeutic strategies, identifying precise biomarkers, and minimizing off-target effects. This review explores the mechanisms of cellular senescence, its role in tumor dynamics, and the potential of senotherapeutics as a novel adjunct in cancer treatment. By integrating senotherapeutics with existing modalities, the field moves closer to more effective, personalized cancer interventions, warranting further preclinical and clinical investigation.

Chronic kidney disease (CKD) presents an ever-growing disease burden for the world’s aging population. It is characterized by numerous changes to the kidney, including a decrease in renal mass, renal fibrosis, and a diminished glomerular filtration rate. The premature aging phenotype observed in CKD is associated with cellular senescence, particularly of renal tubular epithelial cells (TECs), which contributes to chronic inflammation through the production of a proinflammatory senescence associated secretory phenotype (SASP). When coupled with changes in immune system composition and progressive immune dysfunction, the accumulation of senescent kidney cells acts as a driver for the progression of CKD. The targeting of senescent cells may well present an attractive therapeutic avenue for the treatment of CKD. We propose that the targeting of senescent cells either by direct inhibition of pro-survival pathways (senolytics) or through the inhibition of their proinflammatory secretory profile (senomorphics) together with immunomodulation to enhance immune system surveillance of senescent cells could be of benefit to patients with CKD.

“Our oldness is a disease that has to be treated like any other one,”—this statement formulated about a hundred years ago seems to be of current interest in the context of modern investigations. Recently, it has been established that accumulation of senescent cells in various organs and tissues is one of the main causes for the organismal aging, as well as for the progression of multiple age-related pathologies. On the one hand, this observation brings us one step closer to the desired goal—reversal or slowing down of aging. On the other hand, this raises a number of complicated questions: in what essentially lies the difference between senescent and normal cells and how they can be identified; whether senescent cells can be eliminated from the body and can this elimination stop/reverse aging; can such a targeted removal of senescent cells be accompanied by negative consequences, in particular, by an increase in the cancer incidence? This review summarizes the main features of senescent cells, surveys the existing approaches of targeted elimination of senescent cells in vivo, and highlights their advantages and disadvantages.

Cellular senescence is defined as irreversible growth arrest induced by various stress, such as DNA damage and oxidative stress. Senescent cells exhibit various characteristic morphological changes including enlarged morphology. In our recent study, we identified Nectin-4 to be upregulated in cellular senescence by comparative transcriptomic analysis. However, there are few reports on the relationship between Nectin-4 and senescence. Therefore, we analyzed the function of Nectin-4 in senescence and its biological significance. When overexpressed with Nectin-4, the cells exhibited the enlarged cell morphology closely resembling senescent cells. In addition, the cell size enlargement during DNA damage-induced senescence was suppressed by knockdown of Nectin-4, while there were no significant changes in senescence induction. These results suggest that Nectin-4 is not involved in the regulation of senescence itself but contributes to the senescence-associated cell size increase. Furthermore, the Nectin-4-dependent cell size increase was found to be mediated by Src family kinase (SFK)/PI3 kinase (PI3K)/Rac1 pathway. To explore the functional consequences of cell size enlargement, we analyzed cell survival in Nectin-4-depleted senescent cells. Single-cell tracking experiments revealed that Nectin-4 knockdown induced apoptosis in senescent cells, and there is a strong positive correlation between cell size and survival rate. These results collectively indicate that Nectin-4 plays a causative role in the senescence-associated cell size enlargement via SFK/PI3K/Rac1, which can contribute to survival of senescent cells.

Senescence is a prominent solid tumor response to therapy in which cells avoid apoptosis and instead enter into prolonged cell cycle arrest. We applied a quantitative proteomics screen to identify signals that lead to therapy-induced senescence (TIS) and discovered that Bcl2-associated athanogene 3 (Bag3) is upregulated after adriamycin treatment in MCF7 cells. Bag3 protein is a member of the BAG family of co-chaperones that interacts with Hsp70. Bag3 also regulates major signaling pathways. Mass Spectrometry analysis of the Bag3 Complex revealed a novel interaction between Bag3 and Major Vault Protein (MVP). Silencing of Bag3 or MVP shifts the cellular response to adriamycin in favor apoptosis. We demonstrate that Bag3 and MVP contribute to apoptosis resistance in TIS by activation of extracellular signal-regulated kinase1/2 (ERK1/2). Bag3 and MVP were required for ERK1/2 activation in response to adriamycin and silencing either gene product decreased cell survival in response to the drug. An increase in nuclear accumulation of MVP is observed during TIS and the shift in MVP subcellular localization is Bag3-dependent. We propose a model in which Bag3 binds to MVP and facilitates MVP accumulation in the nucleus, which sustains ERK1/2 activation. We demonstrate that Bag3 and MVP are expressed in a panel of diverse breast cancer cell lines and human tumor samples from patients. Silencing of Bag3 and MVP shifts the response to apoptosis and regulates ERK1/2 signaling in ER positive MCF7, ZR751 cell lines and triple negative MDA-MB-231 and MDA-MB-468 cells. Overall this study highlights Bag3-MVP as an important complex that regulates a potent pro-survival signaling pathway in breast cancer. Citation Format: Martina Pasillas, Sarah Shields, Rebecca Reilly, Laoighse Mulrane, Jan Strnadnel, Karin Jirstrom, Darran O Connor, William Gallagher, Steven Gonias, Judith Coppinger. Bcl2-associated athanogene 3 and major vault protein regulate cell survival and resistance to apoptosis in senescent cells by regulating ERK activation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-18. doi:10.1158/1538-7445.AM2014-LB-18

Senolytics and senomorphics: Natural and synthetic therapeutics in the treatment of aging and chronic diseases

Cellular senescence is involved in early development, wound healing, and tumor suppression. However, the accumulation of senescent cells (SCs) drives tissue dysfunction and many age associated pathologies such as cancer and neurodegeneration. SCs demonstrate irreversible cessation of cell cycle, overexpression of anti-apodotic proteins, and senescence associated secretory phenotype (SASP), cause tissue dysfunction. Traditional senolytics induces apoptosis but have poor selectivity, uncertain long-term efficacy, and resistant SCs, limiting their use. Ferroptosis, an iron-dependent, non-apoptotic form of programmed cell death, has emerged as a promising alternative. SCs bypass the apoptosis by overexpression of an anti-apoptotic pathway, but ferroptosis uses oxidative damage to overcome these defenses, thus, making it effective for eliminating SCs. This review critically evaluates ferroptosis-mediated processes such as elevated level of iron, polyunsaturated fatty acids (PUFAs) and oxidative damages in elimination of SCs and its therapeutic potential for age related pathologies including fibrosis, cancer and neurodegenerative diseases. This review highlights the molecular mechanisms underlying ferroptosis and its potential for treating age-related diseases such as fibrosis, atherosclerosis, osteoarthritis, and neurodegeneration. By addressing the translational challenges of ferroptosis-based therapies, we emphasize its potential as a next generation senolytic for targeting senescence and aging-related pathologies.

Radiation Induced and FACS-Sorted Senescent tdTOMp16+ Cells Upregulate Profibrotic Gene Expression in Mesenchymal Stem Cells (Stromal Cells)

Cellular senescence: A novel therapeutic target for central nervous system diseases

Most of the known senolytics are anti-cancer drugs or their derivative molecules. However, senolytics derived from the active ingredients of traditional Chinese medicine (TCM) are rarely reported. Here, we identified oridonin as a novel senolytic and further revealed that it might target a class of glutathione S-transferases to activate ROS-p38 signaling and induce apoptosis in senescent cells.

The progressive accumulation of senescent cells is a primary factor for tissue dysfunction, organismal aging, and the onset of age-related pathologies. While the therapeutic ablation of these cells, termed senolysis, holds immense promise, the development of agents with high selectivity and minimal off-target toxicity remains a critical pharmacological challenge. This review focuses on Procyanidin C1 (PCC1), a naturally occurring polyphenolic trimer derived from grape seed extract, which has emerged as a potent senotherapeutic candidate with a unique, dose-dependent dual mechanism. We analyze the molecular underpinnings of PCC1’s activity, detailing its capacity to induce apoptosis specifically in senescent cells via the amplification of oxidative stress and the upregulation of Bcl-2 family pro-apoptotic factors, Puma and Noxa. Simultaneously, at lower concentrations, PCC1 acts as a senomorphic agent, remodeling the Senescence-Associated Secretory Phenotype (SASP) by intercepting Nuclear Factor-kappa B (NF-κB) signaling. This paper also presents the structural prerequisites for the compound for activity and its efficacy in diverse biological contexts, from enhancing chemotherapy outcomes to mitigating organ fibrosis, positing PCC1 as a versatile tool in the advancement of longevity medicine.

Cellular senescence is a state of stable growth arrest in response to stress, which is a fundamental process of biological aging. They secrete products, the Senescence-Associated Secretory Phenotype (SASP), which consists of inflammatory cytokines, chemokines, growth factors and matrix remodeling proteins. Senescent cells accumulate with advancing age and partial elimination of senescent cells can reverse age-related dysfunction and increase mean lifespan in mice. However, it is not clear whether components of the SASP can be measured in human plasma and serve as aging biomarkers. Here we generated a candidate panel of senescence markers based on a multiplexed bead-based assay of proteins secreted by senescent preadipocytes, endothelial cells, fibroblasts, myoblasts, preadipocytes, and epithelial cells compared to non-senescent controls. The SASP undoubtedly varies by cell type; however, we observed that multiple components of the SASP are conserved. We then assessed circulating SASP components in human plasma samples from Mayo Clinic Biobank participants (n=280, 20 male and 20 female per decade, age 20-90) using the same method. We confirmed that components of the SASP can be quantified in human plasma with the multiplexed bead-based assay and observed several SASP components robustly increase with chronological age in humans. Our study illustrates that senescence-associated secretome components are detectable in human plasma and could potentially serve as biomarkers of systemic aging and senescent cell burden.

Fibrosis is a hallmark of chronic kidney disease, and a primary risk factor for chronic kidney disease is age. Senescent cells accumulate in the kidney during natural aging and after injury. Understanding the effect of senescence on kidney maintenance and how senescence is linked to fibrosis may reveal new therapeutic opportunities. The load of senescent cells in the kidney is predictive of biological age and correlates with renal disease and allograft outcome. Senescent cells do not proliferate to repair injury. Instead, they secrete proteins that enhance inflammation and modulate fibrosis. Pharmaceutical blockade of these effects or elimination of senescent cells can counteract age-related disease. This review explores the relationships among aging, cellular senescence, inflammation, and kidney fibrosis. Drawing from data from various disciplines, we discuss senescence-associated secretory phenotype, klotho, and senotherapy, analyzing the research and looking for new solutions to age-related kidney fibrosis.

Cellular senescence is characterized by stable cell cycle arrest and a secretory program that modulates the tissue microenvironment1,2. Physiologically, senescence serves as a tumor suppressive mechanism that prevents the expansion of premalignant cells3,4 and plays a beneficial role in wound healing responses5,6. Pathologically, the aberrant accumulation of senescent cells generates an inflammatory milieu that leads to chronic tissue damage and contributes to diseases such as liver and lung fibrosis, atherosclerosis, diabetes, and osteoarthritis1,7. Accordingly, elimination of senescent cells from damaged tissues in mice ameliorates symptoms of these pathologies and even promotes longevity1,2,8–10. Here we test the therapeutic concept that chimeric antigen receptor (CAR) T cells targeting senescent cells can be effective senolytics. We identify the urokinase plasminogen activator receptor (uPAR)11 as a cell surface protein broadly induced during senescence and demonstrate that uPAR-specific CAR T cells efficiently ablate senescent cells in vitro and in vivo. uPAR-directed CAR T cells extend the survival of mice harboring lung adenocarcinoma treated with a senescence-inducing drug combination, and restore tissue homeostasis in chemical- or diet-induced liver fibrosis. These results establish the therapeutic potential of senolytic CAR T cells for senescence-associated diseases.