Unraveling ETC complex I function in ferroptosis reveals a potential ferroptosis-inducing therapeutic strategy for LKB1-deficient cancers

The role of the mitochondrial electron transport chain (ETC) in regulating ferroptosis is not fully elucidated. Here, we reveal that pharmacological inhibition of the ETC complex I reduces ubiquinol levels while decreasing ATP levels and activating AMP-activated protein kinase (AMPK), the two effects known for their roles in promoting and suppressing ferroptosis, respectively. Consequently, the impact of complex I inhibitors on ferroptosis induced by glutathione peroxidase 4 (GPX4) inhibition is limited. The pharmacological inhibition of complex I in LKB1-AMPK-inactivated cells, or genetic ablation of complex I (which does not trigger apparent AMPK activation), abrogates the AMPK-mediated ferroptosis-suppressive effect and sensitizes cancer cells to GPX4-inactivation-induced ferroptosis. Furthermore, complex I inhibition synergizes with radiotherapy (RT) to selectively suppress the growth of LKB1-deficient tumors by inducing ferroptosis in mouse models. Our data demonstrate a multifaceted role of complex I in regulating ferroptosis and propose a ferroptosis-inducing therapeutic strategy for LKB1-deficient cancers.

The roles of ferroptosis in cancer: Tumor suppression, tumor microenvironment, and therapeutic interventions

In cancer treatment, the recurrent challenge of inducing apoptosis through conventional therapeutic modalities, often thwarted by therapy resistance, emphasizes the critical need to explore alternative cell death pathways. Ferroptosis, an iron-dependent form of regulated cell death triggered by the lethal accumulation of lipid peroxides on cellular membranes, has emerged as one such promising frontier in oncology. Induction of ferroptosis not only suppresses tumor growth but also holds potential for augmenting immunotherapy responses and surmounting resistance to existing cancer therapies. This review navigates the role of ferroptosis in tumor suppression. Furthermore, we delve into the complex role of ferroptosis within the tumor microenvironment and its interplay with antitumor immunity, offering insights into the prospect of targeting ferroptosis as a strategic approach in cancer therapy.

Exploring Ferroptosis-Inducing Therapies for Cancer Treatment: Challenges and Opportunities

Conventional cancer therapies typically aim to eliminate tumor cells by inducing cell death. The emergence of resistance to these standard treatments has spurred a shift in focus toward exploring alternative cell death pathways beyond apoptosis. Ferroptosis-an iron-dependent regulated cell death triggered by lipid peroxide accumulation-has gained prominence in cancer research in recent years. Ferroptosis-inducing therapies hold promise for overcoming resistance encountered with conventional treatments. However, challenges, including the lack of distinctive ferroptosis markers and the intricate role of ferroptosis within the tumor microenvironment, currently hinder the clinical translation of these therapies. This perspective article critically outlines these hurdles and highlights unexplored opportunities in ferroptosis research, aiming to refine its therapeutic utilization in combating cancer.

BRCA1-mediated dual regulation of ferroptosis exposes a vulnerability to GPX4 and PARP co-inhibition in BRCA1-deficient cancers

Resistance to poly (ADP-ribose) polymerase inhibitors (PARPi) limits the therapeutic efficacy of PARP inhibition in treating breast cancer susceptibility gene 1 (BRCA1)-deficient cancers. Here we reveal that BRCA1 has a dual role in regulating ferroptosis. BRCA1 promotes the transcription of voltage-dependent anion channel 3 (VDAC3) and glutathione peroxidase 4 (GPX4); consequently, BRCA1 deficiency promotes cellular resistance to erastin-induced ferroptosis but sensitizes cancer cells to ferroptosis induced by GPX4 inhibitors (GPX4i). In addition, nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy and defective GPX4 induction unleash potent ferroptosis in BRCA1-deficient cancer cells upon PARPi and GPX4i co-treatment. Finally, we show that xenograft tumors derived from BRCA1-mutant breast cancer patients with PARPi resistance exhibit decreased GPX4 expression and high sensitivity to PARP and GPX4 co-inhibition. Our results show that BRCA1 deficiency induces a ferroptosis vulnerability to PARP and GPX4 co-inhibition and inform a therapeutic strategy for overcoming PARPi resistance in BRCA1-deficient cancers.

Cell cycle arrest induces lipid droplet formation and confers ferroptosis resistance

How cells coordinate cell cycling with cell survival and death remains incompletely understood. Here, we show that cell cycle arrest has a potent suppressive effect on ferroptosis, a form of regulated cell death induced by overwhelming lipid peroxidation at cellular membranes. Mechanistically, cell cycle arrest induces diacylglycerol acyltransferase (DGAT)-dependent lipid droplet formation to sequester excessive polyunsaturated fatty acids (PUFAs) that accumulate in arrested cells in triacylglycerols (TAGs), resulting in ferroptosis suppression. Consequently, DGAT inhibition orchestrates a reshuffling of PUFAs from TAGs to phospholipids and re-sensitizes arrested cells to ferroptosis. We show that some slow-cycling antimitotic drug-resistant cancer cells, such as 5-fluorouracil-resistant cells, have accumulation of lipid droplets and that combined treatment with ferroptosis inducers and DGAT inhibitors effectively suppresses the growth of 5-fluorouracil-resistant tumors by inducing ferroptosis. Together, these results reveal a role for cell cycle arrest in driving ferroptosis resistance and suggest a ferroptosis-inducing therapeutic strategy to target slow-cycling therapy-resistant cancers.

SLC7A11 expression level dictates differential responses to oxidative stress in cancer cells

The cystine transporter solute carrier family 7 member 11 (SLC7A11; also called xCT) protects cancer cells from oxidative stress and is overexpressed in many cancers. Here we report a surprising finding that, whereas moderate overexpression of SLC7A11 is beneficial for cancer cells treated with H2O2, a common oxidative stress inducer, its high overexpression dramatically increases H2O2-induced cell death. Mechanistically, high cystine uptake in cancer cells with high overexpression of SLC7A11 in combination with H2O2 treatment results in toxic buildup of intracellular cystine and other disulfide molecules, NADPH depletion, redox system collapse, and rapid cell death (likely disulfidptosis). We further show that high overexpression of SLC7A11 promotes tumor growth but suppresses tumor metastasis, likely because metastasizing cancer cells with high expression of SLC7A11 are particularly susceptible to oxidative stress. Our findings reveal that SLC7A11 expression level dictates cancer cells' sensitivity to oxidative stress and suggests a context-dependent role for SLC7A11 in tumor biology.

Actin cytoskeleton vulnerability to disulfide stress mediates disulfidptosis

SLC7A11-mediated cystine uptake suppresses ferroptosis yet promotes cell death under glucose starvation; the nature of the latter cell death remains unknown. Here we show that aberrant accumulation of intracellular disulfides in SLC7A11high cells under glucose starvation induces a previously uncharacterized form of cell death distinct from apoptosis and ferroptosis. We term this cell death disulfidptosis. Chemical proteomics and cell biological analyses showed that glucose starvation in SLC7A11high cells induces aberrant disulfide bonds in actin cytoskeleton proteins and F-actin collapse in a SLC7A11-dependent manner. CRISPR screens and functional studies revealed that inactivation of the WAVE regulatory complex (which promotes actin polymerization and lamellipodia formation) suppresses disulfidptosis, whereas constitutive activation of Rac promotes disulfidptosis. We further show that glucose transporter inhibitors induce disulfidptosis in SLC7A11high cancer cells and suppress SLC7A11high tumour growth. Our results reveal that the susceptibility of the actin cytoskeleton to disulfide stress mediates disulfidptosis and suggest a therapeutic strategy to target disulfidptosis in cancer treatment.

A unique regulated cell death-related classification regarding prognosis and immune landscapes in non-small cell lung cancer

Regulated cell death (RCD) contributes to reshaping the tumor immune microenvironment and participating in the progression of non-small cell lung cancer (NSCLC); however, related mechanisms have not been fully disclosed. Here, we identified 5 subclusters of NSCLC based on consensus clustering of 3429 RCD-associated genes in the TCGA database and depicted the genomic features and immune landscape of these clusters. Importantly, the clusters provided insights into recognizing tumor microenvironment (TME) and tumor responses to immunotherapy and chemotherapy. Further, we established and validated an RCD-Risk model based on RCD-associated genes, which strongly predicted the prognosis, TME, and immunotherapy outcomes in NSCLC patients. Notably, tissue microarray staining confirmed that the expression of LDLRAD3, a core gene in RCD-Risk model, correlated with poor survival. In conclusion, we developed a novel RCD classification system and RCD-Risk model of NSCLC, serving as a robust and promising predictor for prognosis and immunotherapy benefit of individual NSCLC patients.

Aging-related features predict prognosis and immunotherapy efficacy in hepatocellular carcinoma

The aging microenvironment serves important roles in cancers. However, most studies focus on circumscribed hot spots such as immunity and metabolism. Thus, it is well ignored that the aging microenvironment contributes to the proliferation of tumor. Herein, we established three prognosis-distinctive aging microenvironment subtypes, including AME1, AME2, and AME3, based on aging-related genes and characterized them with “Immune Exclusion,” “Immune Infiltration,” and “Immune Intermediate” features separately. AME2-subtype tumors were characterized by specific activation of immune cells and were most likely to be sensitive to immunotherapy. AME1-subtype tumors were characterized by inhibition of immune cells with high proportion of Catenin Beta 1 (CTNNB1) mutation, which was more likely to be insensitive to immunotherapy. Furthermore, we found that CTNNB1 may inhibit the expression of C-C Motif Chemokine Ligand 19 (CCL19), thus restraining immune cells and attenuating the sensitivity to immunotherapy. Finally, we also established a robust aging prognostic model to predict the prognosis of patients with hepatocellular carcinoma. Overall, this research promotes a comprehensive understanding about the aging microenvironment and immunity in hepatocellular carcinoma and may provide potential therapeutic targets for immunotherapy.

Targeting ferroptosis as a vulnerability in cancer

Ferroptosis is an iron-dependent form of regulated cell death that is triggered by the toxic build-up of lipid peroxides on cellular membranes. In recent years, ferroptosis has garnered enormous interest in cancer research communities, partly because it is a unique cell death modality that is mechanistically and morphologically different from other forms of cell death, such as apoptosis, and therefore holds great potential for cancer therapy. In this Review, we summarize the current understanding of ferroptosis-inducing and ferroptosis defence mechanisms, dissect the roles and mechanisms of ferroptosis in tumour suppression and tumour immunity, conceptualize the diverse vulnerabilities of cancer cells to ferroptosis, and explore therapeutic strategies for targeting ferroptosis in cancer.

Abstract 5658: DHODH inhibition enhances radiotherapy-induced ferroptosis by promoting mitochondrial lipid peroxidation

Background: Ferroptosis is a form of regulated cell death caused by excessive accumulation of lipid peroxides on the cellular membrane. While impaired ferroptosis has been shown to contribute to tumor development, uncontrolled ferroptosis has been associated with neurodegeneration, acute kidney injury, and cardiovascular disease. To defend against ferroptosis, cells are equipped with several antioxidant systems. Glutathione peroxidase 4 (GPX4) is a major antioxidant enzyme that localizes in both the cytosol and the mitochondria and uses glutathione (GSH) as its cofactor to convert lipid hydroperoxides into non-toxic lipid alcohols. In addition, dihydroorotate dehydrogenase (DHODH) catalyzes the reduction of ubiquinone to ubiquinol in the inner mitochondrial membrane and inhibits mitochondrial lipid peroxidation independently of the GSH-GPX4 mechanism. Radiotherapy (RT) is one of the major therapies used to treat cancers. During RT, the radiolysis of water generates reactive oxygen species (ROS), subsequently leading to lipid peroxidation and ferroptosis. In our study, we aim to determine the role of DHODH in RT-induced ferroptosis and to evaluate the therapeutic potential of DHODH inhibitors as robust radiosensitizers in cancer treatment.

Methods: Lipid peroxidation and mitochondrial lipid peroxidation were evaluated by flow cytometry. Ferroptosis marker PTGS2 expression levels were evaluated by real-time PCR. CRISPR-Cas9 system used to generate knock-out cancer cell lines. Patient-derived xenografts (PDX) co-treated with RT and DHODH inhibitors were employed to access the combination effect. Lipid peroxidation marker 4-HNE levels in tumors were evaluated by immunohistochemistry.

Results: RT induced lipid peroxidation and PTGS2 expression in a variety of cancer cell lines. Genetic knockout of DHODH caused cells more sensitive to RT-induced ferroptosis. Similarly, pharmacological inhibition of DHODH sensitized cancer cells to RT-induced ferroptotic cell death both in vitro and in vivo. Mechanistically, RT induces ROS production in mitochondria, resulting in mitochondrial lipid peroxidation and ferroptosis. DHODH catalyzes the reduction of ubiquinone to ubiquinol, which acts as an antioxidant to inhibit lipid peroxidation in mitochondria. In general, DHODH inhibition significantly sensitizes cancer cells to RT-induced ferroptosis by decreasing ubiquinol levels in mitochondria.

Conclusion: Our study suggests a model in which DHODH inhibition enhances RT-induced ferroptosis. DHODH inhibition significantly decreases the ubiquinol/ubiquinone ratio in mitochondria, thereby sensitizing cancer cells to RT-induced ferroptosis caused by mitochondrial lipid peroxidation. Together, our results demonstrate that DHODH inhibitors can be used as radiosensitizers through inducing ferroptosis and propose a novel combination strategy for cancer therapy.

Citation Format: Chao Mao, Amber Horbath, Guang Lei, Boyi Gan. DHODH inhibition enhances radiotherapy-induced ferroptosis by promoting mitochondrial lipid peroxidation [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 5658.

Fungal Endophthalmitis in a Case of Rhino-Orbito-Cerebral Mucormycosis: Successfully Treated With Amphotericin B Colloidal Dispersion

Background

Rhino-orbito-cerebral mucormycosis (ROCM) is an acute, fulminant, opportunistic fungal infection that usually occurs in diabetes or immunocompromised patients. Amphotericin B combined with surgical debridement remains the standard treatment, although it is controversial due to its lager nephrotoxicity. Thus far, no studies have reported the treatment for ROCM-associated fungal endophthalmitis because the exact pathogenesis and transmission routes in ROCM remain unclear. Here, we reported a case of ROCM complicated with fungal endophthalmitis treated favorably with amphotericin B colloidal dispersion (ABCD) in combination with other antifungals and surgical debridement.

Case Presentation

A 34-year-old woman with diabetes was admitted to our hospital owing to right-sided headache for 8 days, blindness with swelling in the right eye for 5 days, and blindness in the left eye for 1 day. MRI showed that the patient had sphenoid sinus, sinuses, frontal lobe lesions, and proptosis of the right eye. Metagenomic sequencing revealed that the patient had Rhizopus oryzae infection. During hospitalization, the patient received intravenous ABCD, oral posaconazole, and topical amphotericin B and underwent surgical debridement. After 67 days of treatment, the patient’s condition was significantly improved, and limb muscle strength showed grade V. Rhizopus oryzae showed negative results, and conjunctival swelling decreased. Additionally, no nephrotoxicity occurred during treatment. After discharge, the patient’s treatment was transitioned to oral posaconazole and she was free of complaints during the 30-day follow-up without any additional treatment for ROCM.

Conclusion

Treatment with ABCD combined with other antifungal drugs and surgical debridement for ROCM complicated with fungal endophthalmitis showed remarkable efficacy and good safety. Hence, this regimen is a promising treatment strategy for this fatal disease.

A targetable CoQ-FSP1 axis drives ferroptosis- and radiation-resistance in KEAP1 inactive lung cancers

Targeting ferroptosis, a unique cell death modality triggered by unrestricted lipid peroxidation, in cancer therapy is hindered by our incomplete understanding of ferroptosis mechanisms under specific cancer genetic contexts. KEAP1 (kelch-like ECH associated protein 1) is frequently mutated or inactivated in lung cancers, and KEAP1 mutant lung cancers are refractory to most therapies, including radiotherapy. In this study, we identify ferroptosis suppressor protein 1 (FSP1, also known as AIFM2) as a transcriptional target of nuclear factor erythroid 2-related factor 2 (NRF2) and reveal that the ubiquinone (CoQ)-FSP1 axis mediates ferroptosis- and radiation- resistance in KEAP1 deficient lung cancer cells. We further show that pharmacological inhibition of the CoQ-FSP1 axis sensitizes KEAP1 deficient lung cancer cells or patient-derived xenograft tumors to radiation through inducing ferroptosis. Together, our study identifies CoQ-FSP1 as a key downstream effector of KEAP1-NRF2 pathway and as a potential therapeutic target for treating KEAP1 mutant lung cancers.

Iron out KRAS-driven cancer

How to specifically target oncogenic KRAS-driven cancers while sparing normal tissues remains an unmet need in cancer therapy. In this issue of JEM, Jiang et al. (2022. J. Exp. Med.https://doi.org/10.1084/jem.20210739) leveraged KRAS-induced iron addiction in cancer cells to design a clever drug delivery approach to enable selective inhibition of KRAS signaling in mutant KRAS tumors but not in normal tissues, offering a new strategy for treating this largely incurable disease.

Novel role of estrogen receptor-α on regulating chondrocyte phenotype and response to mechanical loading

OBJECTIVE

In knee cartilage from patients with osteoarthritis (OA), both preserved cartilage and damaged cartilage are observed. In this study, we aim to compare preserved with damaged cartilage to identify the molecule(s) that may be responsible for the mechanical loading-induced differences within cartilage degradation.

METHODS

Preserved and damaged cartilage were harvested from the same OA knee joint. RNA Sequencing was performed to examine the transcriptomic differences between preserved and damaged cartilage cells. Estrogen receptor-α (ERα) was identified, and its function of was tested through gene knockin and knockout. The role of ERα in mediating chondrocyte response to mechanical loading was examined via compression of chondrocyte-laded hydrogel in a strain-controlled manner. Findings from the studies on human samples were verified in animal models.

RESULTS

Level of estrogen receptor α (ERα) was significantly reduced in damaged cartilage compared to preserved cartilage, which were observed in both human and mice samples. Knockdown of ESR1, the gene encoding ERα, resulted in an upregulation of senescence- and OA-relevant markers in chondrocytes. Conversely, knockin of ESR1 partially reversed the osteoarthritic and senescent phenotype of OA chondrocytes. Using a three-dimensional (3D) culture model, we demonstrated that mechanical overload significantly suppressed ERα level in chondrocytes with concomitant upregulation of osteoarthritic phenotype. When ESR1 expression was suppressed, mechanical loading enhanced hypertrophic and osteogenic transition.

CONCLUSION

Our study demonstrates a new estrogen-independent role of ERα in mediating chondrocyte phenotype and its response to mechanical loading, and suggests that enhancing ERα level may represent a new method to treat osteoarthritis.

A Cross-Sectional Study of Association between Plasma Selenium Levels and the Prevalence of Osteoarthritis: Data from the Xiangya Osteoarthritis Study

OBJECTIVES

Selenium plays an indispensable role in antioxidant and antiinflammation processes. Oxidative stress and inflammation have been hypothesized to be involved in the pathogenesis of cartilage degeneration. We sought to examine the association between plasma selenium levels and the prevalence of radiographic osteoarthritis (ROA).

DESIGN

A population-based cross-sectional study.

SETTING AND PARTICIPANTS

Individuals aged ≥ 50 years were retrieved from the Xiangya Osteoarthritis (XO) Study, a community-based study conducted among the residents of the rural areas of China.

METHODS

Plasma selenium concentration was measured by inductively coupled plasma-dynamic reaction cell-mass spectrometry. ROA was defined as Kellgren/Lawrence score ≥ 2 in at least one knee, hip or hand joint. The association between plasma selenium levels and ROA was evaluated by applying logistic and spline regression.

RESULTS

A total of 1,032 subjects (women: 52.5%; mean age: 63.1 years; ROA prevalence: 45.4%) were included. Compared with the highest tertile, the odds ratios (ORs) for ROA were 1.24 (95% confidence interval [CI]: 0.91 to 1.68) and 1.77 (95% CI: 1.31 to 2.40) in the middle and lowest tertile of plasma selenium, respectively (P for trend<0.05). The results were not changed materially with adjustment of potential confounders. In addition, subjects who had lower plasma selenium levels exhibited a higher prevalence of ROA in a dose-response relationship manner (P=0.005).

CONCLUSION

This study suggests that subjects with lower levels of plasma selenium exhibited a higher prevalence of ROA in a dose-response relationship manner. However, additional studies are still needed to verify the potential causal relationship.

Targeting cancer stem cells with a pan-BCL-2 inhibitor in preclinical and clinical settings in patients with gastroesophageal carcinoma

OBJECTIVE

Gastro-oesophageal cancers (GEC) are resistant to therapy and lead to poor prognosis. The cancer stem cells (CSCs) and antiapoptotic pathways often confer therapy resistance. We sought to elucidate the antitumour action of a BCL-2 inhibitor, AT101 in GEC in vitro, in vivo and in a clinical trial.

METHODS

Extensive preclinical studies in vitro and in vivo were carried out to establish the mechanism action of AT101 on targeting CSCs and antiapoptotic proteins. A pilot clinical trial in patients with GEC was completed with AT-101 added to standard chemoradiation.

RESULTS

Overexpression of BCL-2 and MCL-1 was noted in gastric cancer tissues (GC). AT-101 induced apoptosis, reduced proliferation and tumour sphere formation in MCL-1/BCL-2 high GC cells. Interestingly, AT101 dramatically downregulated genes (YAP-1/Sox9) that control CSCs in GEC cell lines regardless of BCL-2/MCL-1 expression. Addition of docetaxel to AT-101 amplified its antiproliferation and induced apoptosis effects. In vivo studies confirmed the combination of AT101 and docetaxel demonstrated stronger antitumour activity accompanied with significant decrease of CSCs biomarkers (YAP1/SOX9). In a pilot clinical trial, 13 patients with oesophageal cancer (EC) received AT101 orally concurrently with chemoradiation. We observed dramatic clinical complete responses and encouraging overall survival in these patients. Clinical specimen analyses revealed that AT-101 dramatically reduced the expression of CSCs genes in treated EC specimens indicating antitumour activity of AT101 relies more on its anti-CSCs activity.

CONCLUSIONS

Our preclinical and clinical data suggest that AT-101 overcomes resistance by targeting CSCs pathways suggesting a novel mechanism of action of AT101 in patients with GEC.

Association between bariatric surgery with long-term analgesic prescription and all-cause mortality among patients with osteoarthritis: a general population-based cohort study

OBJECTIVES

There is still a large unmet need for novel osteoarthritis (OA) treatments that could provide clinically important effects on long-term pain relief (≥12 months). We examined the relation of bariatric surgery along with weight loss to analgesic prescription and all-cause mortality among individuals with OA.

METHODS

We conducted a cohort study among individuals with OA using The Health Improvement Network. We compared the rate of no analgesic prescription ≥12 consecutive months and the risk of all-cause mortality using inverse probability weighting Cox-proportional hazard models and the difference in number of analgesic prescriptions (non-steroidal anti-inflammatory drugs, opioids, and paracetamol) in the 50^th, 75^th and 90^th percentiles using quantile regression model between bariatric and non-bariatric cohorts.

RESULTS

Included were 588,494 individuals (694 had bariatric surgery). Compared with non-bariatric group, the rate of no analgesic prescription ≥12 consecutive months was higher (HR = 1.23, 95% CI: 1.08-1.38) in bariatric surgery group, and the number of analgesic prescriptions was lower in the 75^th (44 vs 58) and 90^th (74 vs 106) percentiles during a mean follow-up of 4.3 years. All-cause mortality in bariatric surgery group was lower than comparison group (HR = 0.46, 95% CI: 0.41-0.51).

CONCLUSION

This study presents the first evidence that bariatric surgery was associated with decreased long-term analgesic prescription and decreased all-cause mortality among individuals with OA. However, our findings may be overestimated owing to intractable confounding by indication for bariatric surgery; thus, future studies (e.g., clinical trials) are warranted.

Comparative efficacy and safety of acetaminophen, topical and oral non-steroidal anti-inflammatory drugs for knee osteoarthritis: evidence from a network meta-analysis of randomized controlled trials and real-world data

OBJECTIVE

Current global guidelines regarding the first-line analgesics (acetaminophen, topical or oral non-steroidal anti-inflammatory drugs [NSAIDs]) for knee osteoarthritis remain controversial and their comparative risk-benefit profiles have yet to be adequately assessed.

DESIGN

Pubmed, Embase, Cochrane Library, and Web of Science were searched from database inception to March 2021 for randomized controlled trials (RCTs) comparing acetaminophen, topical NSAIDs and oral NSAIDs directly or indirectly in knee osteoarthritis. Bayesian network meta-analyses were conducted. A propensity-score matched cohort study was also conducted among patients with knee osteoarthritis in The Health Improvement Network database.

RESULTS

122 RCTs (47,113 participants) were networked. Topical NSAIDs were superior to acetaminophen (standardized mean difference [SMD] = -0.29, 95% credible interval [CrI]: -0.52 to -0.06) and not statistically different from oral NSAIDs (SMD = 0.03, 95% CrI: -0.16 to 0.22) for function. It had lower risk of gastrointestinal adverse effects (AEs) than acetaminophen (risk ratio [RR] = 0.52, 95%CrI: 0.35 to 0.76) and oral NSAIDs (RR = 0.46, 95%CrI: 0.34 to 0.61) in RCTs. In real-world data, topical NSAIDs showed lower risks of all-cause mortality (hazard ratio [HR] = 0.59, 95% confidence interval [CI]: 0.52 to 0.68), cardiovascular diseases (HR = 0.73, 95%CI: 0.63 to 0.85) and gastrointestinal bleeding (HR = 0.53, 95%CI: 0.41 to 0.69) than acetaminophen during the one-year follow-up (n = 22,158 participants/group). A better safety profile was also observed for topical than oral NSAIDs (n = 14,218 participants/group).

CONCLUSIONS

Topical NSAIDs are more effective than acetaminophen but not oral NSAIDs for function improvement in people with knee osteoarthritis. Topical NSAIDs are safer than acetaminophen or oral NSAIDs in trials and real-world data.

KEAP1 deficiency drives glucose dependency and sensitizes lung cancer cells and tumors to GLUT inhibition

Metabolic reprogramming in cancer cells can create metabolic liabilities. KEAP1-mutant lung cancer is refractory to most current therapies. Here we show that KEAP1 deficiency promotes glucose dependency in lung cancer cells, and KEAP1-mutant/deficient lung cancer cells are more vulnerable to glucose deprivation than their WT counterparts. Mechanistically, KEAP1 inactivation in lung cancer cells induces constitutive activation of NRF2 transcription factor and aberrant expression of NRF2 target cystine transporter SLC7A11; under glucose limitation, high cystine uptake in KEAP1-inactivated lung cancer cells stimulates toxic intracellular disulfide buildup, NADPH depletion, and cell death, which can be rescued by genetic ablation of NRF2-SLC7A11 axis or treatments inhibiting disulfide accumulation. Finally, we show that KEAP1-inactivated lung cancer cells or xenograft tumors are sensitive to glucose transporter inhibitor. Together, our results reveal that KEAP1 deficiency induces glucose dependency in lung cancer cells and uncover a therapeutically relevant metabolic liability.

mTORC1 and ferroptosis: Regulatory mechanisms and therapeutic potential

Ferroptosis, a form of regulated cell death triggered by lipid hydroperoxide accumulation, has an important role in a variety of diseases and pathological conditions, such as cancer. Targeting ferroptosis is emerging as a promising means of therapeutic intervention in cancer treatment. Polyunsaturated fatty acids, reactive oxygen species, and labile iron constitute the major underlying triggers for ferroptosis. Other regulators of ferroptosis have also been discovered recently, among them the mechanistic target of rapamycin complex 1 (mTORC1), a central controller of cell growth and metabolism. Inhibitors of mTORC1 have been used in treating diverse diseases, including cancer. In this review, we discuss recent findings linking mTORC1 to ferroptosis, dissect mechanisms underlying the establishment of mTORC1 as a key ferroptosis modulator, and highlight the potential of co-targeting mTORC1 and ferroptosis in cancer treatment. This review will provide valuable insights for future investigations of ferroptosis and mTORC1 in fundamental biology and cancer therapy.

PARP inhibition promotes ferroptosis via repressing SLC7A11 and synergizes with ferroptosis inducers in BRCA-proficient ovarian cancer

Pharmacologic inhibition of PARP is the primary therapeutic strategy for BRCA mutant ovarian cancer. However, most of patients carry wild-type BRCA1/2 with no significant clinical benefits from PARP inhibitors, calling for the needs to further understanding and developing new strategy when employing PARP inhibitors to treat ovarian cancer. Here, we show that ferroptosis, a form of regulated cell death driven by iron-dependent phospholipid peroxidation, is partly responsible for the efficacy of PARP inhibitor olaparib. Mechanistically, pharmacological inhibition or genetic deletion of PARP downregulates the expression of cystine transporter SLC7A11 in a p53-dependent manner. Consequently, decreased glutathione biosynthesis caused by SLC7A11 repression promotes lipid peroxidation and ferroptosis. Furthermore, ferroptosis perturbation results in significant resistance to olaparib without affecting DNA damage response, while boosting ferroptosis by ferroptosis inducers (FINs) synergistically sensitizes BRCA-proficient ovarian cancer cells and xenografts to PARP inhibitor. Together, our results reveal a previously unappreciated mechanism coupling ferroptosis to PARP inhibition and suggest the combination of PARP inhibitor and FINs in the treatment of BRCA-proficient ovarian cancer.

POS0186 METABOLOMIC SIGNATURES FOR KNEE CARTILAGE VOLUME LOSS OVER 10 YEARS

Background:

Osteoarthritis (OA) is the most common form of arthritis, and its impact is increasing year by year due to an aging population and lack of effective treatments. One of the main structural pathological changes of OA is the loss of articular cartilage. Tools that can predict cartilage loss would help identify people at high risk, thus preventing OA development.

Objectives:

Using a metabolomics approach, the current study aimed to identify serum metabolomic signatures for predicting the loss of knee cartilage volume over 10 years in a well-established community-based cohort - the Tasmania Older Adult Cohort (TASOAC).

Methods:

TASOAC is an on-going, prospective, population-based study of older adults who were randomly selected from the roll of electors in Southern Tasmania, Australia. Participants had a right knee magnetic resonance imaging (MRI) scan at baseline and a 10-year follow-up. Cartilage volume was measured in the medial, lateral, and patellar compartments and change in cartilage volume over 10 years was calculated as percentage change per year. Fasting serum samples collected at 2.6-year follow-up were metabolomically profiled using the TMIC Prime Metabolomics Profiling Assay which measures a total of 143 metabolites. 129 metabolite concentrations passed the quality control and the pairwise ratios of them as the proxies of enzymatic reaction were calculated. Linear regression models were used to test the association between each of the metabolite ratios and change in cartilage volume in each of the knee compartments with adjustment for age, sex, and body mass index (BMI). The significance was defined at a=3.0×10-6 to control multiple testing of 16,512 ratios with Bonferroni method.

Results:

A total of 344 participants (51% females) were included. The mean baseline age was 62.83±6.13 years and the mean BMI was 27.48±4.41 kg/m2. The average follow-up time was 10.84±0.66 years. Cartilage volume reduced by 1.34±0.72%, 1.06±0.58%, and 0.98±0.46% per year in the medial, lateral, and patellar compartments, respectively. Our data showed that an increased ratio of hexadecenoylcarnitine (C16:1) to tetradecanoylcarnitine (C14) was associated with a 0.12±0.02% per year reduction in patellar cartilage volume (p = 8.80×10-7). An increased ratio of hexadecenoylcarnitine (C16:1) to dodecanoylcarnitine (C12) was also associated with a 0.12±0.02% per year reduction in patellar cartilage volume (p = 2.66×10-6). While there were several metabolite ratios associated with cartilage volume loss in the medial and lateral compartments, none of them reached the predefined significance level.

Conclusion:

Our data suggested that alteration of fatty acid β-oxidation is involved in knee cartilage loss, especially in the patellar compartment, and the serum ratio of C16:1 to C14 and to C12 could be used to predict long-term patellar cartilage loss.

Acknowledgements:

We thank all the study participants who made the study possible. The original TASOAC study was supported by the National Health and Medical Research Council (NHMRC) and the current study was supported by the Canadian Institutes of Health Research (CIHR).

Disclosure of Interests:

None declared

DHODH-mediated ferroptosis defence is a targetable vulnerability in cancer

Ferroptosis, a form of regulated cell death that is induced by excessive lipid peroxidation, is a key tumour suppression mechanism1-4. Glutathione peroxidase 4 (GPX4)5,6 and ferroptosis suppressor protein 1 (FSP1)7,8 constitute two major ferroptosis defence systems. Here we show that treatment of cancer cells with GPX4 inhibitors results in acute depletion of N-carbamoyl-L-aspartate, a pyrimidine biosynthesis intermediate, with concomitant accumulation of uridine. Supplementation with dihydroorotate or orotate-the substrate and product of dihydroorotate dehydrogenase (DHODH)-attenuates or potentiates ferroptosis induced by inhibition of GPX4, respectively, and these effects are particularly pronounced in cancer cells with low expression of GPX4 (GPX4low). Inactivation of DHODH induces extensive mitochondrial lipid peroxidation and ferroptosis in GPX4low cancer cells, and synergizes with ferroptosis inducers to induce these effects in GPX4high cancer cells. Mechanistically, DHODH operates in parallel to mitochondrial GPX4 (but independently of cytosolic GPX4 or FSP1) to inhibit ferroptosis in the mitochondrial inner membrane by reducing ubiquinone to ubiquinol (a radical-trapping antioxidant with anti-ferroptosis activity). The DHODH inhibitor brequinar selectively suppresses GPX4low tumour growth by inducing ferroptosis, whereas combined treatment with brequinar and sulfasalazine, an FDA-approved drug with ferroptosis-inducing activity, synergistically induces ferroptosis and suppresses GPX4high tumour growth. Our results identify a DHODH-mediated ferroptosis defence mechanism in mitochondria and suggest a therapeutic strategy of targeting ferroptosis in cancer treatment.

Does smoking cessation increase risk of knee replacement? a general population-based cohort study

OBJECTIVE

Smoking represents a major issue for global public health. Owing to methodologic challenges, findings of an association between smoking and risk of knee osteoarthritis (OA) are inconsistent. We sought to assess the relation of onset of smoking cessation to the risk of OA sequelae, i.e., knee replacement, and to perform sub-cohort analysis according to weight change after smoking cessation.

DESIGN

Using The Health Improvement Network, we conducted a cohort study to examine the association between smoking cessation and risk of knee replacement among patients with knee OA. Participants who stopped smoking were further grouped into three sub-cohorts: weight gain (body mass index [BMI] increased>1.14 kg/m²), no substantial weight change (absolute value of BMI change<1.14 kg/m²), and weight loss (BMI loss>1.14 kg/m²) after smoking cessation.

RESULTS

We identified 108 cases of knee replacement among 1,054 recent quitters (26.7/1,000 person-years) and 1,108 cases among 15,765 current smokers (17.4/1,000 person-years). The rate difference of knee replacement in recent quitter cohort vs current smoker cohort was 10.4 (95% confidence interval [CI]:5.3-15.6)/1,000 person-years and the adjusted hazard ratio (HR) was 1.30 (95%CI:1.05-1.59). Compared with current smokers, risk of knee replacement was higher among quitters with weight gain (HR = 1.42,95%CI:1.01-1.98), but not among those with no substantial weight change (HR = 1.29,95%CI:0.90-1.83) or those with weight loss (HR = 1.11,95%CI:0.71-1.75).

CONCLUSIONS

Our large population-based cohort study provides the first evidence that smoking cessation was associated with a higher risk of knee replacement among individuals with knee OA, and such an association was due to weight gain after smoking cessation.

Ferroptosis as a mechanism to mediate p53 function in tumor radiosensitivity

Ferroptosis, a form of regulated cell death triggered by lipid peroxidation, was recently identified as an important mechanism in radiotherapy (RT)-mediated tumor suppression and radioresistance, although the exact genetic contexts in which to target ferroptosis in RT remains to be defined. p53 is the most commonly mutated gene in human cancers and a major effector to RT. Here, we identify ferroptosis as a critical mechanism to mediate p53 function in tumor radiosensitivity. Mechanistically, RT-mediated p53 activation antagonizes RT-induced SLC7A11 expression and represses glutathione synthesis, thereby promoting RT-induced lipid peroxidation and ferroptosis. p53 deficiency promotes radioresistance in cancer cells or tumors at least partly through SLC7A11-mediated ferroptosis inhibition. Ferroptosis inducers (FINs) that inhibit SLC7A11 exert significant radiosensitizing effects in tumor organoids and patient-derived xenografts with p53 mutation or deficiency. Finally, we show that RT-induced ferroptosis correlates with p53 activation and better clinical outcomes to RT in cancer patients. Together, our study uncovers a previously unappreciated role of ferroptosis in p53-mediated radiosensitization and suggest using FINs in combination with RT to treat p53-mutant cancers.

A mTORC1-mediated cyst(e)ine sensing mechanism governing GPX4 synthesis and ferroptosis

Ferroptosis is a cell death mechanism triggered by lipid peroxidation. Our recent study linked cyst(e)ine availability with glutathione peroxidase 4 (GPX4) protein synthesis and ferroptosis mitigation via a Rag-mechanistic target of rapamycin complex 1 (mTORC1) axis, and proposed that co-targeting mTORC1 and ferroptosis is a promising strategy for cancer therapy.

Ferroptosis, radiotherapy, and combination therapeutic strategies

Ferroptosis, an iron-dependent form of regulated cell death driven by peroxidative damages of polyunsaturated-fatty-acid-containing phospholipids in cellular membranes, has recently been revealed to play an important role in radiotherapy-induced cell death and tumor suppression, and to mediate the synergy between radiotherapy and immunotherapy. In this review, we summarize known as well as putative mechanisms underlying the crosstalk between radiotherapy and ferroptosis, discuss the interactions between ferroptosis and other forms of regulated cell death induced by radiotherapy, and explore combination therapeutic strategies targeting ferroptosis in radiotherapy and immunotherapy. This review will provide important frameworks for future investigations of ferroptosis in cancer therapy.

The Beneficial Role of Sunitinib in Tumor Immune Surveillance by Regulating Tumor PD-L1

Immune checkpoints blockades have shown promising clinical effects in various malignancies, but the overall response rate is low. Here, the immune features are comprehensively characterized in >10 000 cancer patients from The Cancer Genome Atlas and significantly positive correlations are observed between targets of Sunitinib and inhibitory immune checkpoints and suppressive immune cells. It is further confirmed that Sunitinib treatment increases the antitumor immunity in a phase III trial. Mechanistically, it is discovered that Sunitinib regulates the stability of tumor PD-L1 via p62, that p62 can bind to PD-L1 and specifically promote its translocation into autophagic lysosome for degradation. Preclinically, Sunitinib shows a synergistic antitumor effect with cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) monoclonal antibody (mAb) in melanoma and nonsmall cell lung cancer (NSCLC) immune competent mice by promoting the tumor-infiltrating lymphocytes activity. Clinically, a higher PD-L1 level but a lower p62 level in the tumor region of responders as compared to those of nonresponders among anti-PD-1-treated NSCLC patients is observed. Taken together, by utilizing rigorous computational analysis, functional characterization in vitro and in vivo, and neoadjuvent clinical trial, a novel molecular mechanism is revealed regarding the regulation of PD-L1 via p62, thus providing a novel therapeutic strategy by the combination treatment of CTLA-4 with Sunitinib.

Abstract 2413: Ferroptosis plays an important role in the radiotherapy-induced tumor suppression and radioresistance

Introduction: Radiotherapy (RT) is widely used to treat cancers, but radioresistance remains a major factor in the failure of RT. RT generates reactive oxygen species (ROS) through the radiolysis of cellular water and the stimulation of oxidase, causing cellular damage. Ferroptosis is a regulated cell death induced by iron-dependent peroxidation of phospholipids containing polyunsaturated fatty acids (PUFA-PLs), which is morphologically and mechanistically distinct from apoptosis. There are several core regulators in ferroptosis pathway. SLC7A11 and GPX4 play a role in inhibiting ferroptosis, whereas ACSL4, as an essential lipid metabolism enzyme, promotes ferroptosis by regulating the biosynthesis of PUFA-PLs. Ferroptosis can be induced by either class 1 ferroptosis inducers (FINs) that inhibit SLC7A11 or class 2/3 FINs that inhibit or deplete GPX4. Our study aims to determine the role and mechanisms by which ferroptosis contributes to RT-induced cell death and tumor suppression and to evaluate therapeutic potential of FINs as robust radiosensitizers.

Methods: Ferroptosis markers such as lipid peroxidation or PTGS2 expression was evaluated by flow cytometry, q-PCR or transmission electron microscopy (TEM). Mechanisms were analyzed by western blot and CRISPR-Cas9. Patient derived xenografts (PDX) co-treated with RT and FINs were employed to access the combination effectiveness. Samples were collected from patients before and after RT and ferroptosis marker 4-HNE was correlated with prognosis of patients.

Results: RT induced lipid peroxidation and PTGS2 expression in a variety of cancer types and TEM revealed that cancer cells after RT exhibited shrunken mitochondria with enhanced membrane density, a morphologic feature of ferroptosis. Treatment with ferroptosis inhibitor ferrostatin-1 significantly restored cell survival that had been reduced by exposure to RT, suggesting ferroptosis represents an important part of the RT-induced cell death response. Mechanistically, RT up-regulated the expression of ACSL4, together with RT-generated ROS, to promote lipid peroxidation and ferroptosis. RT also induced the expression of ferroptosis negative regulators, including SLC7A11 and GPX4, leading to radioresistance. In preclinical model, ferroptosis inhibitor liproxstatin-1 partially abolished the RT-induced tumor suppression in H460 xenografts, and FINs (e.g. sulfasalazine) treatment exhibited a significant radiosensitization in A549 xenografts or radioresistant lung cancer patient-derived xenografts (PDXs). In clinical analysis, we revealed very weak 4-HNE levels in all tumor samples before RT, but RT increased 4-HNE levels moderately or strongly in all tumor samples. Importantly, the 4-HNE levels were positively correlated with RT response and disease-free survival in cancer patients.

Conclusions: Our study reveals a previously unrecognized link between RT and ferroptosis, and demonstrates that FINs as a radiosensitizer reverse ferroptosis-mediated radioresistance, and proposes a novel combination therapeutic strategy for cancers, providing an effective approach to overcome radioresistance and facilitating us to initiate follow-up clinical trials to further explore the therapeutic potential of FINs combined with RT in cancer patients.

Citation Format: Guang Lei, Yilei Zhang, Pranavi Koppula, Xiaoguang Liu, Steven Hsesheng Lin, Zhongxing Liao, Hui Wang, Boyi Gan. Ferroptosis plays an important role in the radiotherapy-induced tumor suppression and radioresistance [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2413.

Abstract 2415: H2A monoubiquitination links glucose availability to epigenetic regulation of the endoplasmic reticulum stress induced cell death in cancer

Introduction

Epigenetic regulation of gene transcription coordinates with nutrient availability, although the underlying mechanisms remain incompletely understood. Histone 2A monoubiquitination at lysine 119 (H2Aub), catalyzed mainly by its writer polycomb repressive complex 1 (PRC1), is a histone modification that has been associated with transcriptional repression. Initially, we found glucose withdrawal dramatically decreased H2Aub levels in multiple cancer cell lines. Next, we sought to study the role of H2Aub and H2Aub-associated transcriptional network in tumor cells while modulating glucose availability.

Experimental design

To determine the genes regulated by H2Aub upon glucose deprivation, H2Aub ChIP-seq and RNA-seq analyses were performed in UMRC6 kidney cancer cells with or without glucose. To identify the biological processes associated with the genes identified in our genome-wide analyses, we used Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses.

Results

We found that glucose starvation suppresses histone 2A K119 monoubiquitination (H2Aub), a histone modification that correlates with gene repression. Mechanistically, glucose starvation suppressed H2Aub levels independently of energy stress-mediated AMPK activation and likely acts through reactive oxygen species (ROS)-mediated inhibition of BMI1, an integral component of polycomb repressive complex 1 (PRC1) that catalyzes H2Aub on chromatin. Integrated transcriptomic and epigenomic analyses linked glucose starvation-mediated H2Aub repression to the activation of genes involved in the endoplasmic reticulum (ER) stress response. We further showed that this epigenetic mechanism has a role in glucose starvation-induced cell death. In addition, pharmacologic inhibition of glucose transporter 1 (GLUT1) and PRC1 synergistically promoted ER stress and suppressed tumor growth in vitro and in vivo.

Conclusion

Our study suggests a model in which glucose starvation inhibits PRC1 function potentially through glucose starvation-induced BMI phosphorylation and thereby decreases H2Aub levels, which leads to the de-repression of ER stress gene expression and contributes to the ER stress response and glucose starvation-induced cell death. Together, our results reveal a hitherto unrecognized epigenetic mechanism coupling glucose availability to the ER stress response.

Citation Format: Yilei Zhang, Jiejun Shi, Zhenna Xiao, Guang Lei, Xiaoguang Liu, Hyemin Lee, Pranavi Koppula, Weijie Cheng, Chao Mao, Li Zhuang, Li Ma, Wei Li, Boyi Gan. H2A monoubiquitination links glucose availability to epigenetic regulation of the endoplasmic reticulum stress induced cell death in cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2415.

SAT0453 DELAYED DENOSUMAB INJECTIONS AND FRACTURES RISK AMONG SUBJECTS WITH OSTEOPOROSIS: A POPULATION-BASED COHORT STUDY

Background:

Denosumab is effective for osteoporosis, but discontinuation leads to rapid reversal of its therapeutic effect[1].

Objectives:

To estimate the risk for fracture among users of denosumab who delayed subsequent dosages compared with users who received dosages on time.

Methods:

Population-based cohort study. We included patients aged over 45 years who initiated denosumab for osteoporosis from UK THIN database, 2010 to 2019. Observational data were used to “emulate a hypothetical trial”[2, 3] with three dosing intervals: subsequent denosumab injection 24-28 weeks after prior dose (“on time”), delay by 4-16 weeks (“short delay”), and delay by over 16 weeks (“long delay”). The primary outcome was a composite of all fracture types. Secondary outcomes included major osteoporotic fracture, vertebral fracture, and hip fracture.

Results:

The rate of composite fracture per 1000 person-years was 58.9 for on-time, 61.7 for short delay, and 85.4 for long delay of subsequent denosumab injections. Compared to on-time injections, short delay had a hazard ratio (HR) for composite fracture 1.03 (95% CI 0.63-1.69) and long delay HR 1.44 (95% CI 0.96-2.17; p for trend 0.093). For major osteoporotic fractures, short delay had an HR 0.94 (95% CI 0.57-1.55) and long delay an HR of 1.69 (95% CI 1.01-2.83; p for trend 0.056). For vertebral fractures, short delay had an HR 1.48 (95% CI 0.58-3.79) and long delay 3.91 (95% CI 1.62-9.45; p for trend 0.005).

Conclusion:

While delayed subsequent denosumab dosages over 16 weeks was associated with an increased risk of vertebral and major osteoporotic fracture compared to no delay, composite fracture risk was not increased with longer delays.

References:

[1]Cummings SR, Ferrari S, Eastell R, et al. Vertebral Fractures After Discontinuation of Denosumab: A Post Hoc Analysis of the Randomized Placebo-Controlled FREEDOM Trial and Its Extension. J Bone Miner Res, 2017.

[2]Hernán MA. How to estimate the effect of treatment duration on survival outcomes using observational data. BMJ 2018.

[3]Hernán MA, Robins JM. Using Big Data to Emulate a Target Trial When a Randomized Trial Is Not Available. Am J Epidemiol 2016.

Table.

Rates and Adjusted Hazard Ratios of Fracture

On-timeShort delayLong delayP for linear trendComposite FractureRate (per 1000 person-years)5961.785.4-Unadjusted HR (95 %)Ref1.05 (0.62, 1.76)1.45 (0.95, 2.21)0.097Adjusted HR (95% CI)†Ref1.03 (0.63, 1.69)1.44 (0.96, 2.17)0.093Major Osteoporotic FractureRate (per 1000 person-years)34.831.958-Unadjusted HR (95 %)Ref0.92 (0.55, 1.53)1.67 (0.98, 2.84)0.074Adjusted HR (95% CI)†Ref0.94 (0.57, 1.55)1.69 (1.01, 2.83)0.056Vertebral FractureRate (per 1000 person-years)4.97.319.4-Unadjusted HR (95 %)Ref1.47 (0.58, 3.71)3.93 (1.59, 9.72)0.006Adjusted HR (95% CI)†Ref1.48 (0.58, 3.79)3.91 (1.62, 9.45)0.005Hip FractureRate (per 1000 person-years)10.29.618.3-Unadjusted HR (95 %)Ref0.94 (0.43, 2.04)1.78 (0.80, 3.97)0.18Adjusted HR (95% CI)†Ref0.97 (0.44, 2.12)1.75 (0.81, 3.79)0.173

†Adjusted model: adjusted by age, sex, baseline CCI index, major osteoporotic fracture, oral BP duration (years), 10-year risk of major osteoporotic fracture, prior denosumab doses.

Acknowledgments:

We acknowledge Dr. Dani Prieto-Alhambra for kindly providing Read codes.

Disclosure of Interests:

Houchen Lyu: None declared, Kazuki Yoshida: None declared, Sizheng Steven Zhao: None declared, Xabier García-Albéniz: None declared, Jie Wei: None declared, Chao Zeng: None declared, Sara Tedeschi: None declared, Benjamin Leder Grant/research support from: Research funding from Amgen, Guanghua Lei: None declared, Peifu Tang: None declared, Daniel Solomon Grant/research support from: Funding from Abbvie and Amgen unrelated to this work

H2A Monoubiquitination Links Glucose Availability to Epigenetic Regulation of the Endoplasmic Reticulum Stress Response and Cancer Cell Death

Epigenetic regulation of gene transcription has been shown to coordinate with nutrient availability, yet the mechanisms underlying this coordination remain incompletely understood. Here, we show that glucose starvation suppresses histone 2A K119 monoubiquitination (H2Aub), a histone modification that correlates with gene repression. Glucose starvation suppressed H2Aub levels independently of energy stress-mediated AMP-activated protein kinase activation and possibly through NADPH depletion and subsequent inhibition of BMI1, an integral component of polycomb-repressive complex 1 (PRC1) that catalyzes H2Aub on chromatin. Integrated transcriptomic and epigenomic analyses linked glucose starvation-mediated H2Aub repression to the activation of genes involved in the endoplasmic reticulum (ER) stress response. We further showed that this epigenetic mechanism has a role in glucose starvation-induced cell death and that pharmacologic inhibition of glucose transporter 1 and PRC1 synergistically promoted ER stress and suppressed tumor growth in vivo. Together, these results reveal a hitherto unrecognized epigenetic mechanism coupling glucose availability to the ER stress response. SIGNIFICANCE: These findings link glucose deprivation and H2A ubiquitination to regulation of the ER stress response in tumor growth and demonstrate pharmacologic susceptibility to inhibition of polycomb and glucose transporters.

Efficacy and Safety of Apatinib Plus Vinorelbine in Patients With Wild-Type Advanced Non-Small Cell Lung Cancer After Second-Line Treatment Failure: A Nonrandomized Clinical Trial

IMPORTANCE

There is currently no standard treatment strategy for patients with advanced non-small cell lung cancer (NSCLC) without driver gene variation after failure of 2 or more lines of chemotherapy.

OBJECTIVE

To assess the efficacy and safety of apatinib combined with oral vinorelbine.

DESIGN, SETTING, AND PARTICIPANTS

This phase 2 prospective nonrandomized clinical trial evaluating the efficacy and safety of apatinib plus vinorelbine recruited patients from Hunan Cancer Center, Hunan, China, from January 1, 2017, to November 30, 2018. Eligible patients were those with wild-type advanced NSCLC whose disease did not respond to at least 2 lines of chemotherapy. Patients were evaluated until December 31, 2019. Data were analyzed from July 2019 to December 2019.

INTERVENTION

Apatinib at an initial dose of 500 mg once daily and oral vinorelbine 60 mg/m2 once weekly were administered until disease progression, patient withdrawal, or occurrence of unacceptable toxic effects.

MAIN OUTCOMES AND MEASURES

The primary end point was overall response rate. Secondary end points were overall survival, progression-free survival, and safety.

RESULTS

The potential efficacy of apatinib plus vinorelbine was identified using drug susceptibility assay based on 3-dimensional coculture of tumor cells derived from 3 patients with lung adenocarcinoma. Among 30 patients enrolled, the median (range) age was 63 (34-78) years and 18 (60%) were men. Most patients (27 patients [90%]) had stage IV disease, and the median (range) number of prior unsuccessful treatments was 2 (2-5) lines of chemotherapy. Twenty-five patients (83%) completed the treatment, while 5 patients (17%) discontinued treatment owing to intolerable adverse events. The overall response rate was 36.7% (11 patients) and the disease control rate was 76.7% (23 patients). The median progression-free survival was 4.5 (95% CI, 2.4-6.6) months, and the median overall survival was 10.0 (95% CI, 4.8-17.1) months. Hand-foot syndrome was the most common adverse event observed, including grade 3 hand-foot syndrome observed in 5 patients (17%) and grade 4 hand-foot observed in 1 patient (3%). Grade 3 weakness was observed in 1 patient (3%).

CONCLUSIONS AND RELEVANCE

These findings suggest that apatinib combined with oral vinorelbine is a potentially effective regimen with an acceptable safety profile. This regimen may have potential as a treatment option for patients with wild-type advanced NSCLC whose disease failed at least 2 prior lines of chemotherapy.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03652857.

Thiazide diuretics and risk of knee replacement surgery among patients with knee osteoarthritis: a general population-based cohort study

OBJECTIVE

Thiazide diuretic use is associated with higher bone mineral density (BMD) and possibly lower serum magnesium levels than loop diuretic use, and both high BMD and low serum magnesium have been linked to high prevalent knee osteoarthritis. This study aimed to compare the risk of a clinically relevant endpoint, knee replacement (KR) surgery, among initiators of thiazide and loop diuretics.

DESIGN

Among patients aged ≥50 years with a diagnosis of knee osteoarthritis in The Health Improvement Network (THIN) in United Kingdom, we conducted a propensity score-matched cohort study to examine the relation of thiazide diuretic initiation vs loop diuretic initiation to the risk of KR over 5 years.

RESULTS

Among thiazide and loop diuretic initiators (n = 3,488 for each group; mean age: 73 years; female ratio: 59%), 359 (28.6/1,000 person-years) and 283 (24.1/1,000 person-years) KRs occurred during the follow-up period, respectively. The hazard ratio (HR) of KR for thiazide diuretic initiation vs loop diuretic initiation was 1.26 (95% confidence interval [CI]: 1.08-1.47). The adherence-adjusted HR of KR for continuous use of thiazide diuretics was 1.44 (95% CI: 1.21-1.72).

CONCLUSIONS

In this population-based cohort of patients with knee osteoarthritis, thiazide diuretic use was associated with a higher risk of KR than loop diuretic use. This association may potentially be due to thiazide diuretics' effect on BMD and serum magnesium.

Intra-articular corticosteroids and the risk of knee osteoarthritis progression: results from the Osteoarthritis Initiative

OBJECTIVE

A recent randomized clinical trial reported that repeated intra-articular corticosteroids (IACs) were associated with a greater cartilage loss. This study aimed to examine the relation of IACs to knee radiographic osteoarthritis (ROA) progression in a real-world setting.

DESIGN

A cohort that initiated IACs and a comparison cohort without IACs from participants with mild to moderate knee ROA in the Osteoarthritis Initiative (OAI) were assembled (from 0-month to 48-month). Two measures of knee ROA progression were assessed during the follow-up period: (1) an increase in Kellgren and Lawrence (KL) grade by ≥1 grade or having a knee replacement (i.e., KL grade worsening); and (2) a decrease in joint space width (JSW) by ≥0.7 mm or having a knee replacement (i.e., JSW worsening). The associations of IACs initiation using a propensity-score matched cohort study and continuous IACs using marginal structural models with the risk of knee ROA progression were examined.

RESULTS

Among 684 propensity-score matched participants at baseline (148 IACs initiators, 536 comparators), 65 knees (21.7/100 person-years) in the IACs initiation cohort and 90 knees (7.1/100 person-years) in the comparison cohort experienced KL worsening. The hazard ratios (HRs) of KL worsening from IACs initiation and continuous IACs were 3.02 (95% confidence interval [CI], 2.19-4.16) and 4.67 (95% CI, 2.92-7.47), respectively. The corresponding HRs of JSW worsening were 2.93 (95% CI, 2.13-4.02) and 3.26 (95% CI, 1.78-5.96), respectively. All HRs for continuous use of IACs were further away from the null.

CONCLUSIONS

IACs, especially continuous IACs, may be associated with an increased risk of knee ROA progression.

Elastic Staining on Paraffin-embedded Slides of pT3N0M0 Gastric Cancer Tissue

The elastic lamina, which is usually located in the sub-mesothelial layer, adjacent to the peritoneum mesothelial cells, is amphiphilic on hematoxylin and eosin (H&E) staining but can be visualized through elastic staining. One of the important benefits of elastic staining is that it makes it easy to determine whether tumor cells have invaded beyond the elastic lamina. This helps in examining the extent of peritoneal surface invasion, thereby distinguishing the pT3 and pT4 stages in gastrointestinal cancer. In this study, we present a protocol to identify elastic fibers in the formalin-fixed, paraffin-embedded pT3N0M0 gastric cancer tissue sections. We prepare 5-µm paraffin sections fixed on slides, and then all the slides are deparaffinated and rehydrated during the staining procedure. Subsequently, all the sections are oxidized by potassium permanganate, bleached by oxalic acid, stained by elastic staining, and counterstained by Van Gieson's. Finally, we examine the effect of staining; elastic lamina is stained blue-black and collagen fibers are stained red, while the cancer cells are stained in varying shades of yellow. We also describe in detail the methods used for determining the positional relationship between cancer cells and elastic lamina. This method is simple, low-cost, and widely applicable in the identification of peritoneal surface invasion in gastrointestinal cancer because of its outstanding selectivity for elastic fibers and authentic results.

Risk factor heterogeneity for medial and lateral compartment knee osteoarthritis: analysis of two prospective cohorts

OBJECTIVE

To evaluate the etiologic heterogeneity between medial and lateral tibiofemoral radiographic osteoarthritis (ROA).

METHODS

Knees without medial or lateral tibiofemoral ROA at baseline were followed for 60-month in Multicenter Osteoarthritis Study (MOST) and for 48-month in Osteoarthritis Initiative (OAI). We examined the relation of previously reported risk factors to incident medial and lateral tibiofemoral ROA separately and determined the etiology heterogeneity with a ratio of rate ratios (RRs) (i.e., the RR for medial tibiofemoral ROA divided by the RR for lateral tibiofemoral ROA) using a duplication method for Cox proportional hazard regression.

RESULTS

Of 2,016 participants in MOST, 436 and 162 knees developed medial or lateral tibiofemoral ROA, respectively. Obesity and varus malalignment were 95% and 466% more strongly associated with incident medial tibiofemoral ROA than with lateral tibiofemoral ROA, respectively (ratios of RRs, 1.95 [95% confidence interval (CI):1.05-3.62] and 5.66 [95% CI:3.20-10.0]). In contrast, the associations of female sex and valgus malalignment with incident medial tibiofemoral ROA were weaker or in an opposite direction compared with lateral tibiofemoral Osteoarthritis (OA) (ratios of RRs, 0.40 [95% CI:0.26-0.63] and 0.20 [95% CI:0.12-0.34], respectively). Older age tended to show a weaker association with incident medial tibiofemoral ROA than with incident lateral tibiofemoral ROA. No heterogeneity was observed for the relation of race, knee injury, or contralateral knee ROA. These findings were closely replicated in OAI.

CONCLUSION

Risk factor profiles for medial and lateral tibiofemoral ROA are different. These results can provide a framework for the development of targeted prevention and potential treatment strategies for specific knee OA subtypes.