University of Iowa Holden Comprehensive Cancer Center

BACKGROUND: alterations. METHODS: alterations. All the patients had a history of disease progression during or after at least one course of chemotherapy or within 12 months after neoadjuvant or adjuvant chemotherapy. Prior immunotherapy was allowed. We initially randomly assigned the patients to receive erdafitinib in either an intermittent or a continuous regimen in the dose-selection phase of the study. On the basis of an interim analysis, the starting dose was set at 8 mg per day in a continuous regimen (selected-regimen group), with provision for a pharmacodynamically guided dose escalation to 9 mg. The primary end point was the objective response rate. Key secondary end points included progression-free survival, duration of response, and overall survival. RESULTS: A total of 99 patients in the selected-regimen group received a median of five cycles of erdafitinib. Of these patients, 43% had received at least two previous courses of treatment, 79% had visceral metastases, and 53% had a creatinine clearance of less than 60 ml per minute. The rate of confirmed response to erdafitinib therapy was 40% (3% with a complete response and 37% with a partial response). Among the 22 patients who had undergone previous immunotherapy, the confirmed response rate was 59%. The median duration of progression-free survival was 5.5 months, and the median duration of overall survival was 13.8 months. Treatment-related adverse events of grade 3 or higher, which were managed mainly by dose adjustments, were reported in 46% of the patients; 13% of the patients discontinued treatment because of adverse events. There were no treatment-related deaths. CONCLUSIONS: alterations. Treatment-related grade 3 or higher adverse events were reported in nearly half the patients. (Funded by Janssen Research and Development; BLC2001 ClinicalTrials.gov number, NCT02365597.).

BACKGROUND: The mechanisms of paraneoplastic thrombocytosis in ovarian cancer and the role that platelets play in abetting cancer growth are unclear. METHODS: We analyzed clinical data on 619 patients with epithelial ovarian cancer to test associations between platelet counts and disease outcome. Human samples and mouse models of epithelial ovarian cancer were used to explore the underlying mechanisms of paraneoplastic thrombocytosis. The effects of platelets on tumor growth and angiogenesis were ascertained. RESULTS: Thrombocytosis was significantly associated with advanced disease and shortened survival. Plasma levels of thrombopoietin and interleukin-6 were significantly elevated in patients who had thrombocytosis as compared with those who did not. In mouse models, increased hepatic thrombopoietin synthesis in response to tumor-derived interleukin-6 was an underlying mechanism of paraneoplastic thrombocytosis. Tumor-derived interleukin-6 and hepatic thrombopoietin were also linked to thrombocytosis in patients. Silencing thrombopoietin and interleukin-6 abrogated thrombocytosis in tumor-bearing mice. Anti-interleukin-6 antibody treatment significantly reduced platelet counts in tumor-bearing mice and in patients with epithelial ovarian cancer. In addition, neutralizing interleukin-6 significantly enhanced the therapeutic efficacy of paclitaxel in mouse models of epithelial ovarian cancer. The use of an antiplatelet antibody to halve platelet counts in tumor-bearing mice significantly reduced tumor growth and angiogenesis. CONCLUSIONS: These findings support the existence of a paracrine circuit wherein increased production of thrombopoietic cytokines in tumor and host tissue leads to paraneoplastic thrombocytosis, which fuels tumor growth. We speculate that countering paraneoplastic thrombocytosis either directly or indirectly by targeting these cytokines may have therapeutic potential. (Funded by the National Cancer Institute and others.).

The influence of psychosocial factors on the development and progression of cancer has been a longstanding hypothesis since ancient times. In fact, epidemiological and clinical studies over the past 30 years have provided strong evidence for links between chronic stress, depression and social isolation and cancer progression. By contrast, there is only limited evidence for the role of these behavioral factors in cancer initiation. Recent cellular and molecular studies have identified specific signaling pathways that impact cancer growth and metastasis. This article provides an overview of the relationship between psychosocial factors, specifically chronic stress, and cancer progression.

BACKGROUND: Desmoid tumors (also referred to as aggressive fibromatosis) are connective tissue neoplasms that can arise in any anatomical location and infiltrate the mesentery, neurovascular structures, and visceral organs. There is no standard of care. METHODS: In this double-blind, phase 3 trial, we randomly assigned 87 patients with progressive, symptomatic, or recurrent desmoid tumors to receive either sorafenib (400-mg tablet once daily) or matching placebo. Crossover to the sorafenib group was permitted for patients in the placebo group who had disease progression. The primary end point was investigator-assessed progression-free survival; rates of objective response and adverse events were also evaluated. RESULTS: With a median follow-up of 27.2 months, the 2-year progression-free survival rate was 81% (95% confidence interval [CI], 69 to 96) in the sorafenib group and 36% (95% CI, 22 to 57) in the placebo group (hazard ratio for progression or death, 0.13; 95% CI, 0.05 to 0.31; P<0.001). Before crossover, the objective response rate was 33% (95% CI, 20 to 48) in the sorafenib group and 20% (95% CI, 8 to 38) in the placebo group. The median time to an objective response among patients who had a response was 9.6 months (interquartile range, 6.6 to 16.7) in the sorafenib group and 13.3 months (interquartile range, 11.2 to 31.1) in the placebo group. The objective responses are ongoing. Among patients who received sorafenib, the most frequently reported adverse events were grade 1 or 2 events of rash (73%), fatigue (67%), hypertension (55%), and diarrhea (51%). CONCLUSIONS: Among patients with progressive, refractory, or symptomatic desmoid tumors, sorafenib significantly prolonged progression-free survival and induced durable responses. (Funded by the National Cancer Institute and others; ClinicalTrials.gov number, NCT02066181 .).

Immune-related adverse events (irAEs) are a range of complications associated with the use of immune-checkpoint inhibitors (ICIs). Two major classes of ICIs widely used are Cytotoxic T-Lymphocyte Antigen 4 (CTLA4) and Programmed Cell death-1 (PD-1)/Programmed death-ligand 1 (PD-L1) inhibitors. High-grade irAEs are life-threatening and often cause a severe decline in performance status in such that patients do not qualify for any further anticancer treatments. It is difficult to generalize the evidence in the current literature on risk factors or biomarkers for the entire class of ICIs as the studies so far are either disease-specific (e.g., lung cancer or melanoma) or ICI agent-specific (e.g., pembrolizumab, ipilimumab) or irAE-specific (e.g., pneumonitis or gastritis). In this review, risk factors and biomarkers to consider before initiating or monitoring ICI are listed with a practical purpose in day-to-day practice. Risk factors are grouped into demographics and social history, medical history, and medication history, tumor-specific and agent-specific risk factors. A higher risk of irAE is associated with age <60 years, high body mass index, women on CTLA4 and men on PD-1/PD-L1 agents, and chronic smokers. Patients with significant kidney (Stage IV-V), cardiac (heart failure, coronary artery disease, myocardial infarction, hypertension), and lung (asthma, pulmonary fibrosis, and chronic obstructive pulmonary disease) are at a higher risk of respective organ-specific irAEs. Pre-existing autoimmune disease and chronic use of certain drugs (proton pump inhibitors, diuretics, anti-inflammatory drugs) also increase the irAE-risk. Biomarkers are categorized into circulating blood counts, cytokines, autoantibodies, HLA genotypes, microRNA, gene expression profiling, and serum proteins. The blood counts and certain protein markers (albumin and thyroid-stimulating hormone) are readily accessible in current practice. High neutrophil-lymphocyte ratio, eosinophil/monocyte/lymphocyte counts; TSH and troponins at diagnosis and drop in the white count and lymphocyte count can predict irAE. Other biomarkers with limited evidence are cytokines, autoantibodies, HLA genotypes, microRNA, and gene expression profiling. With fast-expanding approvals for ICIs in various cancer types, knowledge on risk factors and biomarkers can help providers assess the irAE-risk of their patients. Prospective disease and agent-specific studies are needed to provide further insight on this essential aspect of ICI therapy.

PURPOSE: Pharmacologic concentrations of ascorbate may be effective in cancer therapeutics. We hypothesized that ascorbate concentrations achievable with i.v. dosing would be cytotoxic in pancreatic cancer for which the 5-year survival is <3%. EXPERIMENTAL DESIGN: Pancreatic cancer cell lines were treated with ascorbate (0, 5, or 10 mmol/L) for 1 hour, then viability and clonogenic survival were determined. Pancreatic tumor cells were delivered s.c. into the flank region of nude mice and allowed to grow at which time they were randomized to receive either ascorbate (4 g/kg) or osmotically equivalent saline (1 mol/L) i.p. for 2 weeks. RESULTS: There was a time- and dose-dependent increase in measured H(2)O(2) production with increased concentrations of ascorbate. Ascorbate decreased viability in all pancreatic cancer cell lines but had no effect on an immortalized pancreatic ductal epithelial cell line. Ascorbate decreased clonogenic survival of the pancreatic cancer cell lines, which was reversed by treatment of cells with scavengers of H(2)O(2). Treatment with ascorbate induced a caspase-independent cell death that was associated with autophagy. In vivo, treatment with ascorbate inhibited tumor growth and prolonged survival. CONCLUSIONS: These results show that pharmacologic doses of ascorbate, easily achievable in humans, may have potential for therapy in pancreatic cancer.

PURPOSE To update recommendations of the ASCO systemic therapy for hormone receptor (HR)-positive metastatic breast cancer (MBC) guideline. METHODS An Expert Panel conducted a systematic review to identify new, potentially practice-changing data. RESULTS Fifty-one articles met eligibility criteria and form the evidentiary basis for the recommendations. RECOMMENDATIONS Alpelisib in combination with endocrine therapy (ET) should be offered to postmenopausal patients, and to male patients, with HR-positive, human epidermal growth factor receptor 2 (HER2)-negative, PIK3CA-mutated, ABC, or MBC following prior endocrine therapy with or without a cyclin-dependent kinase (CDK) 4/6 inhibitor. Clinicians should use next-generation sequencing in tumor tissue or cell-free DNA in plasma to detect PIK3CA mutations. If no mutation is found in cell-free DNA, testing in tumor tissue, if available, should be used as this will detect a small number of additional patients with PIK3CA mutations. There are insufficient data at present to recommend routine testing for ESR1 mutations to guide therapy for HR-positive, HER2-negative MBC. For BRCA1 or BRCA2 mutation carriers with metastatic HER2-negative breast cancer, olaparib or talazoparib should be offered in the 1st-line through 3rd-line setting. A nonsteroidal aromatase inhibitor (AI) and a CDK4/6 inhibitor should be offered to postmenopausal women with treatment-naïve HR-positive MBC. Fulvestrant and a CDK4/6 inhibitor should be offered to patients with progressive disease during treatment with AIs (or who develop a recurrence within 1 year of adjuvant AI therapy) with or without one line of prior chemotherapy for metastatic disease, or as first-line therapy. Treatment should be limited to those without prior exposure to CDK4/6 inhibitors in the metastatic setting. Additional information can be found at www.asco.org/breast-cancer-guidelines .

BACKGROUND AND OBJECTIVES: Sarcopenia, which is subclinical loss of skeletal muscle mass, is commonly observed in patients with malignancy. The objective of this study is to determine the correlation between sarcopenia and operative complications following pancreatectomy for cancer. METHODS: A retrospective review of a pancreatectomy database was performed. The Hounsfield Unit Average Calculation (HUAC) of the psoas muscle, a marker of muscle density and fatty infiltration, was measured from preoperative CT scans. Complications were graded and multivariate logistic regression analysis was performed. RESULTS: One hundred eighteen patients met criteria for analysis; the overall morbidity rate was 78.8% (n = 93). There were 31 (26.3%) patients who met criteria for sarcopenia using the HUAC. When analyzed as a continuous variable, sarcopenia was an independent predictor of major grade III complications, length of stay, intensive care unit admission, delayed gastric emptying, and infectious, gastrointestinal, pulmonary, and cardiac complications. CONCLUSIONS: These data suggest that sarcopenia as measured with the HUAC, a value that can be obtained from a preoperative CT scan, is a significant independent predictor of surgical outcome and can be used to improve patient selection and informed consent prior to pancreatectomy in patients with cancer.

Mutations in genes coding for succinate dehydrogenase (SDH) subunits are believed to contribute to cancer and aging, but the mechanism for this is unclear. Hamster fibroblasts expressing a mutation in SDH subunit C (SDHC; B9) showed 3-fold increases in dihydroethidine and dichlorodihydrofluorescein (CDCFH(2)) oxidation indicative of increased steady-state levels of O2(.-) and H2O2, increases in glutathione/glutathione disulfide (indicative of oxidative stress), as well as increases in superoxide dismutase activity, relative to parental B1 cells. B9 cells also showed characteristics associated with cancer cells, including aneuploidy, increases in glucose consumption, and sensitivity to glucose deprivation-induced cytotoxicity. Expression of wild-type (WT) human SDHC in B9 cells caused prooxidant production, glucose consumption, sensitivity to glucose deprivation-induced cytotoxicity, and aneuploidy to revert to the WT phenotype. These data show that SDHC mutations cause increased O2(.-) production, metabolic oxidative stress, and genomic instability and that mutations in genes coding for mitochondrial electron transport chain proteins can contribute to phenotypic changes associated with cancer cells. These results also allow for the speculation that DNA damage to genes coding for electron transport chain proteins could result in a "mutator phenotype" by increasing steady-state levels of O2(.-) and H2O2.

Immunotherapy has revolutionized the treatment of both hematological malignancies and solid tumors. The use of immunotherapy has improved outcome for patients with cancer across multiple tumor types, including lung, melanoma, ovarian, genitourinary, and more recently breast cancer with durable responses seen even in patients with widespread metastatic disease. Despite the promising results, immunotherapy still helps only a subset of patients due to overall low response rates. Moreover, the response to immunotherapy is highly cancer specific and results have not been as promising in cancers that are considered less immunogenic. The strategies to improve immunotherapy responses have focused on biomarker selection, like PD-L1 status, and usage of combinatorial agents, such as chemotherapy, targeted therapy, and radiotherapy. Of particular interest, DNA-damaging agents have the potential to enhance the response to immunotherapy by promoting neoantigen release, increasing tumor mutational burden, and enhancing PD-L1 expression. Poly-ADP-ribose polymerase (PARP) inhibitors are one such class of drugs that has shown synergy with immunotherapy in preclinical and early clinical studies. PARP-based therapies work through the inhibition of single-strand DNA repair leading to DNA damage, increased tumor mutational burden, making the tumor a more attractive target for immunotherapy. This article focuses on the promise of combinatorial PARP inhibition and immunotherapy to improve patient outcomes in solid tumors, summarizing both early results and looking towards ongoing trials.

NAD(P)H:quinone oxidoreductase (NQO1) is elevated in human pancreatic cancers. We hypothesized that beta-lapachone, a novel 1,2-naphthoquinone with potential antitumor activity in cancer cells expressing elevated levels of NQO1, would induce cytotoxicity in pancreatic cancer cells, wherein this two-electron reductase was recently found elevated. beta-lapachone decreased clonogenic cell survival, metabolic cell viability, and anchorage- independent growth in soft agar. The cytotoxic in vitro effects of beta-lapachone were inhibited with coadministration of dicumarol, a specific inhibitor of NQO1. In preestablished human pancreatic tumor xenografts in nude mice, beta-lapachone demonstrated greater tumor growth inhibition when given intratumorally compared to when complexed with cyclodextrin to increase its bioavailability. Due to the poor prognosis of patients with pancreatic cancer and the limited effectiveness of surgery, chemotherapy, and radiation therapy, treatment regimens based on sound, tumor-specific rationales are desperately need for this disease.

Breast cancer is a common cause of brain metastases, with metastases occurring in at least 10-16 % of patients. Longer survival of patients with metastatic breast cancer and the use of better imaging techniques are associated with an increased incidence of brain metastases. Unfortunately, patients who develop brain metastases tend to have poor prognosis with short overall survival. In addition, brain metastases are a major cause of morbidity, associated with progressive neurologic deficits that result in a reduced quality of life. Tumor subtypes play a key role in prognosis and treatment selection. Current therapies include surgery, whole-brain radiation therapy, stereotactic radiosurgery, chemotherapy and targeted therapies. However, the timing and appropriate use of these therapies is controversial and careful patient selection by using available prognostic tools is extremely important. This review will focus on current treatment options, novel therapies, future approaches and ongoing clinical trials for patients with breast cancer brain metastases.

PURPOSE: Complement may play a role in the clinical response to rituximab and other monoclonal antibody-based therapies of cancer. The purpose of this study was to explore the relationship between the C1qA([276]) polymorphism and the clinical response to rituximab in patients with follicular lymphoma. EXPERIMENTAL DESIGN: Genotyping for C1qA([276A/G]) was done in 133 subjects with follicular lymphoma treated with single-agent rituximab, and correlation with clinical response was done using Cox regression analysis. RESULTS: Prolonged remission was observed among subjects that responded clinically to rituximab therapy and were carriers of the A allele compared with homozygous G subjects. Homozygous G subjects had a time to progression of 282 days, whereas A-allele carriers had a time to progression of 708 days [hazard ratio, (HR), 2.5; 95% confidence interval (95% CI), 2.0-3.1; P = 0.02]. Among subjects who achieved complete remission, homozygous G subjects had a time to progression of 250 days, whereas A-allele carriers had a time to progression of 1,118 days (HR, 4.5; 95% CI, 4.1-4.8, P = 0.04). The difference persisted after controlling for CD32 and CD16 polymorphisms. In patients who responded to rituximab used as first-line agent, a linear trend was observed among the C1qA([276]) genotypes, with homozygous A subjects achieving complete response at a higher rate compared with heterozygous or homozygous G subjects. CONCLUSIONS: Our findings indicate that polymorphisms in the C1qA gene may affect the clinical response and duration of response to rituximab therapy of follicular lymphoma. These results could have direct implications on designing antibodies with improved efficiency and enhance our understanding of the role of complement in monoclonal antibody therapy.

PURPOSE: We determined the influence of age on response to intravesical immunotherapy in patients with superficial bladder cancer. MATERIALS AND METHODS: Data from a national phase II multicenter trial for BCG plus IFN-alpha intravesical therapy for superficial bladder cancer were analyzed. Recurrence-free survival 2 years after the initiation of therapy was examined in patients by incremental age decade. BCG-N patients received 81 mg BCG and 50 MU IFN-alpha, while patients who had previously been treated with BCG received a third of the BCG dose with 50 MU IFN-alpha and those who were BCG intolerant received a tenth of the BCG dose with 100 MU IFN-alpha. Kaplan-Meier survival curves were obtained. RESULTS: In all patients the largest difference in response was between the 289 who were 61 to 70 years old and the 123 who were older than 80 years with a 22% difference in cancer-free survival at a median followup of 24 months (61% vs 39%, p = 0.0002). When we assessed BCG-N and BCG treated patients separately in the 2 age groups, patients older than 80 years had a persistently lower response rate than younger patients 61 to 70 years old. Of BCG-N patients those older than 80 and younger than 50 years had the lowest cancer-free survival at a median followup of 24 months (47% and 45%, respectively). On multivariate analysis age was an independent risk factor for response. CONCLUSIONS: Aging appears to be associated with a decreased response to intravesical immunotherapy and is particularly apparent in patients older than 80 years. A potential explanation could be their depressed baseline immune status and consequent inability to mount an immune reaction to BCG or IFN-alpha.

BACKGROUND: The authors undertook a multiinstitutional Phase II cooperative group study to examine the potential of oral fish oil fatty acid supplements administered at high doses to slow weight loss and to improve quality of life in patients with malignancy-related cachexia. METHODS: Patients with advanced malignancy and weight loss > or = 2% of body weight in the preceding month took concentrated, high-dose omega-3 fatty acid capsules (7.5 g eicosapentaenoic acid plus docosahexaenoic acid for a 70 kg individual) that were supplied by the National Institutes of Health. RESULTS: Forty-three patients with moderate or severe malnutrition were enrolled. The median time receiving treatment was 1.2 months. For the 36 patients who took at least 1 capsule and did not have edema, there was a weight change ranging from -6.2 kg to +3.5 kg and an overall median weight loss of 0.8 kg. Twenty-four patients had weight stabilization (a gain of < or = 5% or a loss of < 5%), 6 patients gained > 5% of their body weight, and 6 patients lost > or = 5% of their body weight. There was marked variability in the tolerability of the capsules, and many patients had gastrointestinal side effects. There was a correlation between time receiving treatment and weight gain for the 22 patients who were able to tolerate the capsules for at least 1 month. Quality-of-life scores were superior for patients who gained weight. CONCLUSIONS: A majority of patients did not gain weight, and in that sense, the results of the study were unfavorable. However, a small but definite subset of patients had weight stabilization or weight gain. This suggests that omega-3 fatty acids have potential utility at the study doses, which were more than twice the doses used in published Phase III studies.

BACKGROUND: Although bowel symptoms and complaints are common after radical hysterectomy, the effects of operation on anorectal function are incompletely understood. In this prospective pilot study we evaluated the incidence of bowel symptoms, changes in anorectal physiology, and quality of life after radical hysterectomy. STUDY DESIGN: Eleven women undergoing radical hysterectomy for early-stage cervical cancer completed bowel function symptom surveys and cancer-specific quality-of-life scales before operation and at 6 weeks and 6 months after operation. The bowel function symptom survey was also repeated at 18 months postoperation. Anorectal manometry, balloon defecation, and pudendal nerve latency tests were performed before the operation and 6 months postoperatively. RESULTS: The mean age was 45.3 years (range 34 to 56 years), and four of the patients were postmenopausal. Resting and squeeze sphincter pressures, volume of saline infused at first leak, total volume retained, and threshold volume for maximum tolerable volume were all decreased significantly (p < 0.05) after operation. Pudendal nerve terminal motor latency increased (p < 0.05) bilaterally. There were no significant differences in sensory thresholds. At 18 months, two women reported constipation, six reported flatus incontinence, and two reported fecal incontinence. The total quality-of-life score declined at 6 weeks but then improved significantly by 6 months (p = 0.02). CONCLUSIONS: Bowel dysfunction is common after radical hysterectomy. Many women exhibit manometric and subjective changes compatible with fecal incontinence.

During metastasis, cancer cells are exposed to potentially destructive hemodynamic forces including fluid shear stress (FSS) while en route to distant sites. However, prior work indicates that cancer cells are more resistant to brief pulses of high-level FSS in vitro relative to non-transformed epithelial cells. Herein, we identify a mechano-adaptive mechanism of FSS resistance in cancer cells. Our findings demonstrate that cancer cells activate RhoA in response to FSS, which protects them from FSS-induced plasma membrane damage. We show that cancer cells freshly isolated from mouse and human tumors are resistant to FSS, that formin and myosin II activity protects circulating tumor cells (CTCs) from destruction, and that short-term inhibition of myosin II delays metastasis in mouse models. Collectively, our data indicate that viable CTCs actively resist destruction by hemodynamic forces and are likely to be more mechanically robust than is commonly thought.

Importance: Colorectal cancer (CRC) screening is underused, especially among vulnerable populations. Decision aids and patient navigation are potentially complementary interventions for improving CRC screening rates, but their combined effect on screening completion is unknown. Objective: To determine the combined effect of a CRC screening decision aid and patient navigation compared with usual care on CRC screening completion. Design, Setting, and Participants: In this randomized clinical trial, data were collected from January 2014 to March 2016 at 2 community health center practices, 1 in North Carolina and 1 in New Mexico, serving vulnerable populations. Patients ages 50 to 75 years who had average CRC risk, spoke English or Spanish, were not current with recommended CRC screening, and were attending primary care visits were recruited and randomized 1:1 to intervention or control arms. Interventions: Intervention participants viewed a CRC screening decision aid in English or Spanish immediately before their clinician encounter. The decision aid promoted screening and presented colonoscopy and fecal occult blood testing as screening options. After the clinician encounter, intervention patients received support for screening completion from a bilingual patient navigator. Control participants viewed a food safety video before the encounter and otherwise received usual care. Main Outcomes and Measures: The primary outcome was CRC screening completion within 6 months of the index study visit assessed by blinded medical record review. Results: Characteristics of the 265 participants were as follows: their mean age was 58 years; 173 (65%) were female, 164 (62%) were Latino; 40 (15%) were white non-Latino; 61 (23%) were black or of mixed race; 191 (78%) had a household income of less than $20 000; 101 (38%) had low literacy; 75 (28%) were on Medicaid; and 91 (34%) were uninsured. Intervention participants were more likely to complete CRC screening within 6 months (68% vs 27%); adjusted-difference, 40 percentage points (95% CI, 29-51 percentage points). The intervention was more effective in women than in men (50 vs 21 percentage point increase, interaction P = .02). No effect modification was observed across other subgroups. Conclusions and Relevance: A patient decision aid plus patient navigation increased the rate of CRC screening completion in compared with usual care invulnerable primary care patients. Trial Registration: clinicaltrials.gov Identifier: NCT02054598.

Abstract Ferroptosis is an iron-dependent, non-apoptotic form of regulated cell death driven by lipid hydroperoxides within biological membranes. Although therapy-resistant mesenchymal-high cancers are particularly vulnerable to ferroptosis inducers, especially phospholipid glutathione peroxidase 4 (GPx4) inhibitors, the underlying mechanism is yet to be deciphered. As such, the full application of GPx4 inhibitors in cancer therapy remains challenging. Here we demonstrate that metadherin (MTDH) confers a therapy-resistant mesenchymal-high cell state and enhanced sensitivity to inducers of ferroptosis. Mechanistically, MTDH inhibited GPx4, as well as the solute carrier family 3 member 2 (SLC3A2, a system X c − heterodimerization partner), at both the messenger RNA and protein levels. Our metabolomic studies demonstrated that MTDH reduced intracellular cysteine, but increased glutamate levels, ultimately decreasing levels of glutathione and setting the stage for increased vulnerability to ferroptosis. Finally, we observed an enhanced antitumor effect when we combined various ferroptosis inducers both in vitro and in vivo; the level of MTDH correlated with the ferroptotic effect. We have demonstrated for the first time that MTDH enhances the vulnerability of cancer cells to ferroptosis and may serve as a therapeutic biomarker for future ferroptosis-centered cancer therapy.

Thiol antioxidants, including N-acetyl-L-cysteine (NAC), are widely used as modulators of the intracellular redox state. We investigated the hypothesis that NAC-induced reactive oxygen species (ROS) signaling perturbs cellular proliferation by regulating the cell cycle regulatory protein cyclin D1 and the ROS scavenging enzyme Mn-superoxide dismutase (MnSOD). When cultured in media containing NAC, mouse fibroblasts showed G(1) arrest with decreased cyclin D1 protein levels. The absence of a NAC-induced G(1) arrest in fibroblasts overexpressing cyclin D1 (or a nondegradable mutant of cyclin D1-T286A) indicates that cyclin D1 regulates this G(1) arrest. A delayed response to NAC exposure was an increase in both MnSOD protein and activity. NAC-induced G(1) arrest is exacerbated in MnSOD heterozygous fibroblasts. Results from electron spin resonance spectroscopy and flow cytometry measurements of dihydroethidine fluorescence showed an approximately 2-fold to 3-fold increase in the steady-state levels of superoxide (O(2)(*-)) in NAC-treated cells compared with control. Scavenging of O(2)(*-) with Tiron reversed the NAC-induced G(1) arrest. These results show that an O(2)(*-) signaling pathway regulates NAC-induced G(1) arrest by decreasing cyclin D1 protein levels and increasing MnSOD activity.