Cellular senescence is a stable growth arrest that is implicated in tissue ageing and cancer. Senescent cells are characterized by an upregulation of proinflammatory cytokines, which is termed the senescence-associated secretory phenotype (SASP). NAD + metabolism influences both tissue ageing and cancer. However, the role of NAD + metabolism in regulating the SASP is poorly understood. Here we show that nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme of the NAD + salvage pathway, governs the proinflammatory SASP independent of senescence-associated growth arrest. NAMPT is regulated by HMGAs during senescence. The HMGAs/NAMPT/NAD + signaling axis promotes the proinflammatory SASP through enhancing glycolysis and mitochondrial respiration. HMGAs/NAMPT promotes the proinflammatory SASP through NAD + -mediated suppression of AMPK kinase, which suppresses p53-mediated inhibition of p38MAPK to enhance NFκb activity. We conclude that NAD + metabolism governs the proinflammatory SASP. Given the tumor-promoting effects of the proinflammatory SASP, our results suggest that anti-ageing dietary NAD + augmentation should be administered with precision.

Despite the high initial response rates to PARP inhibitors (PARPi) in BRCA-mutated epithelial ovarian cancers (EOC), PARPi resistance remains a major challenge. Chemical modifications of RNAs have emerged as a new layer of epigenetic gene regulation. N 6 -methyladenosine (m 6 A) is the most abundant chemical modification of mRNA, yet the role of m 6 A modification in PARPi resistance has not previously been explored. Here, we show that m 6 A modification of FZD10 mRNA contributes to PARPi resistance by upregulating the Wnt/b-catenin pathway in BRCA-mutated EOC cells. Global m 6 A profile revealed a significant increase in m 6 A modification in FZD10 mRNA, which correlated with increased FZD10 mRNA stability and an upregulation of the Wnt/b-catenin pathway. Depletion of FZD10 or inhibition of the Wnt/b-catenin sensitizes resistant cells to PARPi. Mechanistically, downregulation of m 6 A demethylases FTO and ALKBH5 was suffi-cient to increase FZD10 mRNA m 6 A modification and reduce PARPi sensitivity, which correlated with an increase in homologous recombination activity. Moreover, combined inhibition of PARP and Wnt/b-catenin showed synergistic suppression of PARPi-resistant cells in vitro and in vivo in a xenograft EOC mouse model. Overall, our results show that m 6 A contributes to PARPi resistance in BRCA-deficient EOC cells by upregulating the Wnt/b-catenin pathway via stabilization of FZD10. They also suggest that inhibition of the Wnt/b-catenin pathway represents a potential strategy to overcome PARPi resistance.Significance: These findings elucidate a novel regulatory mechanism of PARPi resistance in EOC by showing that m 6 A modification of FZD10 mRNA contributes to PARPi resistance in BRCA-deficient EOC cells via upregulation of Wnt/b-catenin pathway.

Epithelial ovarian cancer (EOC) is the most lethal of gynecologic malignancies. The standard-of-care treatment for EOC is platinumbased chemotherapy such as cisplatin. Platinum-based chemotherapy induces cellular senescence. Notably, therapy-induced senescence contributes to chemoresistance by inducing cancer stem-like cells (CSC). However, therapeutic approaches targeting senescenceassociated CSCs remain to be explored. Here, we show that nicotinamide phosphoribosyltransferase (NAMPT) inhibition suppresses senescence-associated CSCs induced by platinum-based chemotherapy in EOC. Clinically applicable NAMPT inhibitors suppressed the outgrowth of cisplatin-treated EOC cells both in vitro and in vivo. Moreover, a combination of the NAMPT inhibitor FK866 and cisplatin improved the survival of EOCbearing mice. These phenotypes correlated with inhibition of the CSCs signature, which consists of elevated expression of ALDH1A1 and stem-related genes, high aldehyde dehydrogenase activity, and CD133 positivity. Mechanistically, NAMPT regulates EOC CSCs in a paracrine manner through the senescence-associated secretory phenotype. Our results suggest that targeting NAMPT using clinically applicable NAMPT inhibitors, such as FK866, in conjunction with platinum-based chemotherapy represents a promising therapeutic strategy by suppressing therapy-induced senescenceassociated CSCs.Significance: This study highlights the importance of NAMPTmediated NAD þ biosynthesis in the production of cisplatininduced senescence-associated cancer stem cells, as well as tumor relapse after cisplatin treatment.

Summary Coordinated expression of mitochondrial and nuclear genes is required to maintain proper mitochondrial function. However, the precise mechanisms that ensure this coordination are not well defined. We find that signaling from mitochondria to the nucleus is influenced by mammalian target of rapamycin (mTOR) activity via changes in autophagy and p62/SQSTM1 turnover. Reducing mTOR activity increases autophagic flux, enhances mitochondrial membrane potential, reduces reactive oxygen species within the cell, and increases replicative life span. These effects appear to be mediated in part by an interaction between p62/SQSTM1 and Keap1. This interaction allows nuclear accumulation of the nuclear factor erythroid 2-like 2 (NFE2L2, also known as nuclear factor related factor 2 or NRF2), increased expression of the nuclear respiratory factor 1 (NRF1), and increased expression of nuclear-encoded mitochondrial genes, such as the mitochondrial transcription factor A, and mitochondrial-encoded genes involved in oxidative phosphorylation. These findings reveal a portion of the intracellular signaling network that couples mitochondrial turnover with mitochondrial renewal to maintain homeostasis within the cell and suggest mechanisms whereby a reduction in mTOR activity may enhance longevity.

Advanced age is characterized by increased incidence of many chronic, noninfectious diseases that impair the quality of living of the elderly and pose a major burden on the healthcare systems of developed countries. These diseases are characterized by impaired or altered function at the tissue and cellular level, which is a hallmark of the aging process. Age-related impairments are likely due to loss of homeostasis at the cellular level, which leads to the accumulation of dysfunctional organelles and damaged macromolecules, such as proteins, lipids, and nucleic acids. Intriguingly, aging and age-related diseases can be delayed by modulating nutrient signaling pathways converging on the target of rapamycin (TOR) kinase, either by genetic or dietary intervention. TOR signaling influences aging through several potential mechanisms, such as autophagy, a degradation pathway that clears the dysfunctional organelles and damaged macromolecules that accumulate with aging. Autophagy substrates are targeted for degradation by associating with p62/SQSTM1, a multidomain protein that interacts with the autophagy machinery. p62/SQSTM1 is involved in several cellular processes, and its loss has been linked to accelerated aging and to age-related pathologies. In this review, we describe p62/SQSTM1, its role in autophagy and in signaling pathways, and its emerging role in aging and age-associated pathologies. Finally, we propose p62/ SQSTM1 as a novel target for aging studies and ageextending interventions.

Tumor recurrence years after seemingly successful treatment of primary tumors is one of the major causes of mortality in patients with cancer. Reactivation of dormant tumor cells is largely responsible for this phenomenon. Using dormancy models of lung and ovarian cancer, we found a specific mechanism, mediated by stress and neutrophils, that may govern this process. Stress hormones cause rapid release of proinflammatory S100A8/A9 proteins by neutrophils. S100A8/A9 induce activation of myeloperoxidase, resulting in accumulation of oxidized lipids in these cells. Upon release from neutrophils, these lipids up-regulate the fibroblast growth factor pathway in tumor cells, causing tumor cell exit from the dormancy and formation of new tumor lesions. Higher serum concentrations of S100A8/A9 were associated with shorter time to recurrence in patients with lung cancer after complete tumor resection. Targeting of S100A8/A9 or β2-adrenergic receptors abrogated stress-induced reactivation of dormant tumor cells. These observations demonstrate a mechanism linking stress and specific neutrophil activation with early recurrence in cancer.

SUMMARY ARID1A , a subunit of the SWI/SNF complex, is among the most frequently mutated genes across cancer types. ARID1A is mutated in more than 50% of ovarian clear cell carcinomas (OCCCs), diseases that have no effective therapy. Here, we show that ARID1A mutation confers sensitivity to pan-HDAC inhibitors such as SAHA in ovarian cancers. This correlated with enhanced growth suppression induced by the inhibition of HDAC2 activity in ARID1A-mutated cells. HDAC2 interacts with EZH2 in an ARID1A status-dependent manner. HDAC2 functions as a co-repressor of EZH2 to suppress the expression of EZH2/ARID1A target tumor suppressor genes such as PIK3IP1 to inhibit proliferation and promote apoptosis. SAHA reduced the growth and ascites of the ARID1A-inactivated OCCCs in both orthotopic and genetic mouse models. This correlated with a significant improvement of survival of mice bearing ARID1A-mutated OCCCs. These findings provided preclinical rationales for repurposing FDA-approved pan-HDAC inhibitors for treating ARID1A-mutated cancers.

Unexpected activation of mTOR signaling, measured by ribosomal S6 phosphorylation or ribosomal S6 kinase (p70S6K) activity, has been reported in aging-related settings. Evidence of elevated mTOR activity has been reported in heart and muscle tissue in aged mice and humans, mouse models of progeria, and senescent human fibroblasts. We explore these reports and the possibility that activation of the mTOR/p70S6K kinase pathway may represent a ROS-mediated response to mitochondrial stress leading to the activation of senescence. This activation is a hallmark of both aged tissue and senescent human cells.