ABSTRACT Chemotherapy-induced peripheral neuropathy (CIPN) is a common, debilitating complication of cancer therapy. Although axonal degeneration defines CIPN, the initiating cellular events remain unknown. Here, we show that CIPN is initiated by senescent peripheral fibroblasts rather than by the neuron itself. Across the mechanistically distinct chemotherapeutic agents paclitaxel and cisplatin, chemotherapy-induced senescence is unexpectedly restricted to peripheral fibroblasts rather than neurons and acts upstream of neuronal SARM1 activation. Genetic or pharmacological ablation of senescent fibroblasts prevents neuropathy and reverses established disease, demonstrating that these cells are required for both disease initiation and maintenance. Mechanistically, senescent fibroblasts drive neuropathic injury through an MK2-dependent senescence-associated secretory phenotype (SASP), and genetic or pharmacological inhibition of MK2 suppresses the SASP, preserves peripheral innervation and restores sensory function. Together, these findings redefine the cellular origin of CIPN and identify MK2-dependent fibroblast senescence as a therapeutic target.

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Chemotherapy-induced bone loss is a debilitating and common side effect of cancer treatment, though its underlying mechanisms remain poorly understood. Here, we show that, despite the systemic administration of chemotherapy, cellular senescence is restricted to bone marrow adipo-lineage cells specifically Cxcl12-abundant reticular (CAR) cells and bone marrow adipocytes (BMAds). Induction of senescence within these populations promotes RANK ligand (RANKL)-mediated osteoclastogenesis, leading to significant bone loss. Notably, we find that inhibition of the p38MAPK-MK2 pathway suppresses the senescence-associated secretory phenotype (SASP), including RANKL production abrogating bone loss. Furthermore, treatment with the senolytic combination dasatinib and quercetin (D + Q) selectively eliminates senescent CAR cells and BMAds, effectively preventing chemotherapy-induced bone loss. Given that nearly all chemotherapy treated patients experience bone loss and associated fracture risk, our findings offer a promising therapeutic avenue to preserve bone integrity and improve quality of life for cancer patients. Chemotherapy induces bone loss that compromises skeletal health in cancer patients. Here, the authors show that chemotherapy-induced senescence in bone marrow adipo-lineage cells leads to bone loss and demonstrate that senolytic targeting of senescent cells preserves skeletal health during chemotherapy, providing a potential strategy to protect the skeleton in cancer therapy.

Table containing all of our reagents

Chemotherapy is a mainstay of cancer therapy. Unfortunately, while chemotherapy can profoundly impact disease free survival, it’s often accompanied with devastating side effects, including peripheral neuropathy. Indeed, 30-40% of patients treated with neurotoxic chemotherapy develop long-term and often debilitating chemotherapy-induced peripheral neuropathy (CIPN). Unfortunately, there are currently no preventative measures for CIPN and while it is transitory in some patients, for others the side effects can persist for months or even years after the cessation of chemotherapy. Recent work suggests that cellular senescence, which is robustly induced by chemotherapy, contributes to CIPN. Senescent cells are typically characterized by increased CDKn2a (i.e., p16) expression, increased SA-β-gal hydrolyzation, and expression of the senescence-associated secretory phenotype (SASP) that can influence multiple cell types in the microenvironment. Through utilization of a mouse model that employs paclitaxel (PTX), we find that PTX robustly induces senescence in the hindpaws and dorsal root ganglia (DRG) of mice that display loss of peripheral axons and decreased response to mechanical stimuli. To address the role of senescence in CIPN, we utilized the INKATTAC mouse that allows for inducible elimination senescent cells. Using this model, we find that the elimination of senescent cells rescues CIPN. Further, the use of senolytics, drugs that kill senescent cells, also rescues CIPN, raising the possibility that we can treat patients with CIPN. To address the mechanism behind CIPN we have carried out single cell RNA-Seq to identify the population of senescent cells senescing in response to chemotherapy. These analyses will allow us to understand the mechanisms that drive CIPN and may lead to new treatments for patients suffering from CIPN. Citation Format: Taylor Malachowski, Ganesh Raut, Satarupa Mullick Bagchi, Shelia Stewart. Chemotherapy induced senescence drives peripheral neuropathy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4796.

Abstract Despite breakthroughs in cancer treatment, chemotherapy-induced osteo-toxicity is a major problem that compromises the quality of life and overall survival of cancer patients regardless of cancer type. Recently we demonstrated that chemotherapy-induced senescence drives bone loss by both limiting mineralization of new bone and increasing bone resorption. However, the underlying mechanism of action remains elusive. Therefore, it is critical that we understand the mechanisms that drive these toxicities and develop approaches to mitigate their severity. To establish whether senescent bone resident cells or systemic responses to chemotherapy drove therapy-induced bone loss, we used a vertebral body transplant (vossicle) model. Using this approach, we found that the specific elimination of senescent cells in L4 and L5 donor vossicles (INK-ATTAC) implanted into wildtype mice, protects from chemotherapy-induced bone loss within the vossicles but not the femur of the recipient mice. This demonstrated that chemotherapy-induced senescence in resident bone cells is responsible for bone loss. To determine which bone resident cell(s) underwent senescence in response to chemotherapy and how their gene expression was impacted, we used the p16-CreERT2-tdTomato mouse model and found that chemotherapy triggers senescence in bone marrow adipocytes. Subsequently, we observed that postnatal fat ablation in adipoqCre-inducible DTR transgenic mice (iDTRADQ) prevented chemotherapy-induced bone loss, indicating senescent adipocytes trigger bone loss. Furthermore, we observed chemotherapy-induced bone loss is attributed to RANKL-mediated high osteoclasts activity. Collectively, our data demonstrate that chemotherapy causes senescence in marrow adipocytes which in turn triggers bone loss via RANKL-mediated osteoclasts activation and bone loss can be protected by eliminating senescent cells. Citation Format: Ganesh Kumar Raut, Taylor Malachowski, Taylor Holt, Renata Oliveira, Xianmin Luo, Douglas Faget, Qihao Ren, Sheila Stewart. Chemotherapy-induced adipocyte senescence triggers bone loss through osteoclast activation [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 2956.

Abstract Metastatic breast cancer is an intractable disease that responds poorly to immunotherapy. We show that p38MAPKα inhibition (p38i) limits tumor growth by reprogramming the metastatic tumor microenvironment in a CD4+ T cell-, IFNγ-, and macrophage-dependent manner. To identify targets that further increased p38i efficacy, we utilized a stromal labeling approach and single-cell RNA sequencing. Thus, we combined p38i and an OX40 agonist that synergistically reduced metastatic growth and increased overall survival. Intriguingly, patients with a p38i metastatic stromal signature had better overall survival that was further improved by the presence of an increased mutational load, leading us to ask if our approach would be effective in antigenic breast cancer. The combination of p38i, anti-OX40, and cytotoxic T-cell engagement cured mice of metastatic disease and produced long-term immunologic memory. Our findings demonstrate that a detailed understanding of the stromal compartment can be used to design effective antimetastatic therapies. Significance: Immunotherapy is rarely effective in breast cancer. We dissected the metastatic tumor stroma, which revealed a novel therapeutic approach that targets the stromal p38MAPK pathway and creates an opportunity to unleash an immunologic response. Our work underscores the importance of understanding the tumor stromal compartment in therapeutic design. This article is highlighted in the In This Issue feature, p. 1275

Polyphenols are naturally occurring organic compounds with varying structures represented by four major groups: flavonoids, phenolic acids, lignans and stilbenes. Several studies suggested that these secondary metabolites have health benefits due to its anti-tumorigenic effect. Therefore, substantial effort has been put forward to isolate and characterize these natural compounds and synthesize analogues that may serve as potential anti-cancer therapeutics. This present study is aimed at designing and synthesis of azaflavanone derivative and in understanding its mechanism of action in vitro and in vivo. Molecular docking studies predicted that the compound can potentially bind strongly to the Cyclin E1-Cdk2 complex which is a key mediator of the cell cycle progression indicating a biological interference in aggressive prostate cancer. Further downstream studies to understand its cytotoxicity and mechanism of action showed this azaflavanone derivative markedly inhibits viability of prostate cancer cells (DU145) showing an IC50 value of 0.4 μM compared to other cancer cells. The pharmacological ROS insult using the azaflavanone derivative increases the oxidative damage leading to high expression of apoptotic markers with increasing concentration. On compound treatment, the cells lose the metabolic flexibility accompanied by mitochondrial dysfunction leading to cell cycle arrest and apoptosis. Further, no compound mediated toxicity was observed in xenograft mouse model of prostate cancer at a concentration as high as 5 mg/kg. The tumor burden was reduced to 60% rendering the azaflavanone derivative a potential candidate in cancer therapeutics. Collectively, the compound triggers cell cycle arrest and ROS mediated oxidative stress sensitizing the cancerous cells towards apoptosis.

BACKGROUND INFORMATION:Various types of stress initially induce a state of cardiac hypertrophy (CH) in the heart. But, persistent escalation of cardiac stress leads to progression from an adaptive physiological to a maladaptive pathological state. So, elucidating molecular mechanisms that can attenuate CH is imperative in developing cardiac therapies. Previously, we showed that Prohibitin1 (PHB1) has a protective role in CH-induced oxidative stress. Nevertheless, it is unclear how PHB1, a mitochondrial protein, has a protective role in CH. Therefore, we hypothesized that PHB1 maintains mitochondrial quality in CH. To test this hypothesis, we used Isoproterenol (ISO) to induce CH in H9C2 cells overexpressing PHB1 and elucidated mitochondrial quality control pathways.RESULTS:We found that overexpressing PHB1 attenuates ISO-induced CH and restores mitochondrial morphology in H9C2 cells. In addition, PHB1 blocks the pro-hypertrophic IGF1R/AKT pathway and restores the mitochondrial membrane polarization in ISO-treated cells. We observed that overexpressing PHB1 promotes mitochondrial biogenesis, improves mitochondrial respiratory capacity, and triggers mitophagy.CONCLUSION:We conclude that PHB1 maintains mitochondrial quality in ISO-induced CH in H9C2 cells.SIGNIFICANCE:Based on our results, we suggest that small molecules that induce PHB1 in cardiac cells may prove beneficial in developing cardiac therapies.

Despite the central role chemotherapy plays in prolonging survival, the toxicities associated with its use can negatively impact quality of life and in some cases, be so severe that patients forego further life preserving treatments. Therefore, it is critical that we understand the mechanisms that drive these toxicities and develop approaches to mitigate their severity. Recently we demonstrated that chemotherapy-induced senescence drives bone loss by both limiting mineralization of new bone and increasing bone resorption. To establish whether senescent bone resident cells or systemic responses to chemotherapy drove therapy-induced bone loss, we used a vossicle model in which neonatal vertebral bones (L4 and L5) were transplanted from 4-day old wildtype or INKATTAC pups (allow to selectively kill senescent cells) into wildtype or INKATTAC adult mice. Using this approach, we found that the elimination of senescent cells in donor vossicles protects from chemotherapy-induced bone loss, indicating that senescent bone resident cells are responsible for therapy-induced bone loss. To understand the mechanism(s) that contributed to therapy-induced bone loss, we used scRNA-seq to determine which bone resident cells underwent senescence in response to chemotherapy and how their gene expression was impacted. Using this approach, we found that adipocytes, fibroblast, chondrocytes and osteoblasts underwent senescence as evidenced by expression of p16, p21 and loss of Mki67 and displayed evidence of a senescence associated secretory phenotype (SASP), which we postulate contributes to therapy-induced bone loss. Collectively, our data indicated that chemotherapy causes bone loss via senescence and can be protected by eliminating senescent cells. Citation Format: Ganesh Kumar Raut, Zhangting Yao, Tom Cole, Xainmin Luo, Qihao Ren, Sheila A. Stewart. Abrogating therapy induced senescence driven bone loss to improve quality of life [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 137.

Cancer is a cellular disease that results when cell division occurs in uncontrolled manner with the potential to invade or spread from one part to other parts of the body. Cancer is expected to rank as the major cause of mortality in economically developed countries in comparison to being the second cause in economically developing countries. It is reported that cancer cell is inherent to consume high glucose as a metabolic source to meet the energy demand required during their uncontrolled proliferation. Nutrient uptake by cancer cells is the key factor for the generation of cellular components such as amino acids, lipids, and nucleic acids to give rise to a new cell. Moreover, reactive oxygen species (ROS) is produced as a by-product of cellular respiration that damages cells and creates DNA mutations. A major focus of this chapter is to better understand the metabolic pathways involved in both tumor suppression and tumor formation and also to understand and develop better therapeutic strategies by modulating tumor microenvironment via metabolic stress that provide flexibility of cancer cells to tune them to drugs or induce cells to move toward apoptosis.

Cardiac hypertrophy is an adaptive response to stress, in order to maintain proper cardiac function. However, sustained stress leads to pathological hypertrophy accompanied by maladaptive responses and ultimately heart failure. At the cellular level, cardiomyocyte hypertrophy is characterized by an increase in myocyte size, reactivation of the fetal gene markers, disassembly of the sarcomere and transcriptional remodelling which are regulated by heart-specific transcription factors like MEF2, GATA4 and immediate early genes like c-jun and c-fos.2. It has been explored and established that the hypertrophic process is associated by oxidative stress and mediated by pathways involving several terminal stress kinases like P38, JNK and ERK1/2. Stilbenoids are bioactive polyphenols and earlier studies have shown that imine stilbene exert cardioprotective and anti aging effects by acting as modulators of Sirt1. The present study was aimed at designing and synthesizing a series of imine stilbene analogs and investigate its anti hypertrophic effects and regulatory mechanism in cardiac hypertrophy and apoptosis. Interestingly one of the analog, compound 3e (10 μM) alleviated isoproterenol (ISO, 25 μM) induced hypertrophy in rat cardiomyocyte (H9c2) cells by showing a marked decrease in the myocyte size. Further, compound 3e also restored the cardiac function by activating the metabolic stress sensor, AMPK. Moreover, molecular docking studies showed stable binding between compound 3e and GSK3β suggesting that compound 3e may directly regulate GSK3β activity and ameliorate ISO-induced cardiac hypertrophy. In agreement with this, compound 3e also modulated the crosstalk of all the hypertrophy inducing terminal Kinases by bringing down the expression to near control conditions. The compound also relieved H2O2 (100 μM) mediated ROS and normalized abnormal mitochondrial oxygen demand in hypertrophic conditions indicating the possibility of the compound to show promise in playing a role in cardiac hypertrophy.

In recent years there has been an upsurge in research focusing on reprogramming cancer cells through understanding of their metabolic signatures. Alterations in mitochondrial bioenergetics and impaired mitochondrial function may serve as effective targeting strategies especially in triple-negative breast cancers (TNBCs) where hormone receptors and endocrine therapy are absent. Glucose starvation (GS) of MDA-MB-231 and MCF-7 breast cancer cells showed decrease in mitochondrial Oxygen Consumption Rate (OCR), which was rescuable to control level through addition of exogenous antioxidant N-Acetyl Cysteine (NAC). Mechanistically, GS led to increase in mitochondrial ROS and upregulation of the pleiotropic protein, Prohibitin 1 (PHB1), leading to its dissociation from Dynamin-related protein 1 (DRP1), perturbance of mitochondrial membrane potential (MMP) and triggering of the apoptosis cascade. PHB1 also reduced the invasive and migratory potential of both cell lines. We emphasize that glucose starvation remarkably sensitized the highly glycolytic metastatic TNBC cell line, MDA-MB-231 to apoptosis and decreased its migratory potential. Based on our findings, additional TNBC cell lines can be evaluated and a nutritional paradigm be proposed for anticancer therapy.