Bioisosteric analogs of MDMA: Improving the pharmacological profile?

3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') is re-emerging in clinical settings as a candidate for the treatment of specific neuropsychiatric disorders (e.g. post-traumatic stress disorder) in combination with psychotherapy. MDMA is a psychoactive drug, typically regarded as an empathogen or entactogen, which leads to transporter-mediated monoamine release. Despite its therapeutic potential, MDMA can induce dose-, individual-, and context-dependent untoward effects outside safe settings. In this study, we investigated whether three new methylenedioxy bioisosteres of MDMA improve its off-target profile. In vitro methods included radiotracer assays, transporter electrophysiology, bioluminescence resonance energy transfer and fluorescence-based assays, pooled human liver microsome/S9 fraction incubations, metabolic stability studies, isozyme mapping, and liquid chromatography coupled to high-resolution mass spectrometry. In silico methods included molecular docking. Compared with MDMA, all three MDMA bioisosteres (ODMA, TDMA, and SeDMA) showed similar pharmacological activity at human serotonin, dopamine, and norepinephrine transporters (hSERT, hDAT, and hNET, respectively) but decreased agonist activity at 5-HT2A/2B/2C receptors. Regarding their hepatic metabolism, they differed from MDMA, with N-demethylation being the only metabolic route shared, and without forming phase II metabolites. In addition, TDMA showed an enhanced intrinsic clearance in comparison to its congeners. Additional screening for their interaction with human organic cation transporters (hOCTs) and plasma membrane monoamine transporter (hPMAT) revealed a weaker interaction of the MDMA analogs with hOCT1, hOCT2, and hPMAT. Our findings suggest that these new MDMA bioisosteres might constitute appealing therapeutic alternatives to MDMA, sparing the primary pharmacological activity at hSERT, hDAT, and hNET, but displaying a reduced activity at 5-HT2A/2B/2C receptors and alternative hepatic metabolism. Whether these MDMA bioisosteres may pose lower risk alternatives to the clinically re-emerging MDMA warrants further studies.

Using 42 CFR part 2 revisions to integrate substance use disorder treatment information into electronic health records at a safety net health system.

BACKGROUND: Regulations put in place to protect the privacy of individuals receiving substance use disorder (SUD) treatment have resulted in an unintended consequence of siloed SUD treatment and referral information outside of the integrated electronic health record (EHR). Recent revisions to these regulations have opened the door to data integration, which creates opportunities for enhanced patient care and more efficient workflows. We report on the experience of one safety-net hospital system integrating SUD treatment data into the EHR. METHODS: SUD treatment and referral information was integrated from siloed systems into the EHR through the implementation of a referral order, treatment episode definition, and referral and episode-related tools for addiction therapists and other clinicians. Integration was evaluated by monitoring SUD treatment episode characteristics, patient characteristics, referral linkage, and treatment episode retention before and after integration. Satisfaction of end-users with the new tools was evaluated through a survey of addiction therapists. RESULTS: After integration, three more SUD treatment programs were represented in the EHR. This increased the number of patients that could be tracked as initiating SUD treatment by 250%, from 562 before to 1,411 after integration. After integration, overall referral linkage declined (74% vs. 48%) and treatment episode retention at 90-days was higher (45% vs. 74%). Addiction therapists appreciated the efficiency of having all SUD treatment information in the EHR but did not find that the tools provided a large time savings shortly after integration. CONCLUSIONS: Integration of SUD treatment program data into the EHR facilitated both care coordination in patient treatment and quality improvement initiatives for treatment programs. Referral linkage and retention rates were likely modified by a broader capture of patients and changed outcome definition criteria. Greater preparatory workflow analysis may decrease initial end-user burden. Integration of siloed data, made possible given revised regulations, is essential to an efficient hub-and-spoke model of care, which must standardize and coordinate patient care across multiple clinics and departments.

Simultaneous screening of overexpressed genes in breast cancer for oncogenic drivers and tumor dependencies.

There are hundreds of genes typically overexpressed in breast cancer cells and it's often assumed that their overexpression contributes to cancer progression. However, the precise proportion of these overexpressed genes contributing to tumorigenicity remains unclear. To address this gap, we undertook a comprehensive screening of a diverse set of seventy-two genes overexpressed in breast cancer. This systematic screening evaluated their potential for inducing malignant transformation and, concurrently, assessed their impact on breast cancer cell proliferation and viability. Select genes including ALDH3B1, CEACAM5, IL8, PYGO2, and WWTR1, exhibited pronounced activity in promoting tumor formation and establishing gene dependencies critical for tumorigenicity. Subsequent investigations revealed that CEACAM5 overexpression triggered the activation of signaling pathways involving ß-catenin, Cdk4, and mTOR. Additionally, it conferred a growth advantage independent of exogenous insulin in defined medium and facilitated spheroid expansion by inducing multiple layers of epithelial cells while preserving a hollow lumen. Furthermore, the silencing of CEACAM5 expression synergized with tamoxifen-induced growth inhibition in breast cancer cells. These findings underscore the potential of screening overexpressed genes for both oncogenic drivers and tumor dependencies to expand the repertoire of therapeutic targets for breast cancer treatment.

Bioisosteric analogs of MDMA with improved pharmacological profile.

3,4-Methylenedioxymethamphetamine (MDMA, ' ecstasy' ) is re-emerging in clinical settings as a candidate for the treatment of specific psychiatric disorders (e.g. post-traumatic stress disorder) in combination with psychotherapy. MDMA is a psychoactive drug, typically regarded as an empathogen or entactogen, which leads to transporter-mediated monoamine release. Despite its therapeutic potential, MDMA can induce dose-, individual-, and context-dependent untoward effects outside safe settings. In this study, we investigated whether three new methylenedioxy bioisosteres of MDMA improve its off-target profile. In vitro methods included radiotracer assays, transporter electrophysiology, bioluminescence resonance energy transfer and fluorescence-based assays, pooled human liver microsome/S9 fraction incubation with isozyme mapping, and liquid chromatography coupled to high-resolution mass spectrometry. In silico methods included molecular docking. Compared with MDMA, all three MDMA bioisosteres (ODMA, TDMA, and SeDMA) showed similar pharmacological activity at human serotonin and dopamine transporters (hSERT and hDAT, respectively) but decreased activity at 5-HT 2A/2B/2C receptors. Regarding their hepatic metabolism, they differed from MDMA, with N -demethylation being the only metabolic route shared, and without forming phase II metabolites. Additional screening for their interaction with human organic cation transporters (hOCTs) and plasma membrane transporter (hPMAT) revealed a weaker interaction of the MDMA analogs with hOCT1, hOCT2, and hPMAT. Our findings suggest that these new MDMA analogs might constitute appealing therapeutic alternatives to MDMA, sparing the primary pharmacological activity at hSERT and hDAT, but displaying a reduced activity at 5-HT 2A/2B/2C receptors and reduced hepatic metabolism. Whether these MDMA bioisosteres may pose lower risk alternatives to the clinically re-emerging MDMA warrants further studies.

The wildland firefighter exposure and health effect (WFFEHE) study: cohort characteristics and health behavior changes in context.

OBJECTIVES: Work is an under-recognized social determinant of health. There is limited research describing US wildland firefighter (WFF) workforce demographics or how to work associates with WFF health behaviors. In this study researchers characterized a WFF cohort and tested hypotheses that WFFs used tobacco, alcohol, and sugar-sweetened beverages (SSBs) differently over the course of the fire season and that different fire crews may exhibit different behavior patterns. METHODS: Researchers collected data in the field with 6 WFF crews during 2 consecutive fire seasons (2018 and 2019). WFF crews completed questionnaires before and after each season. WFFs with an initial preseason questionnaire and at least 1 follow-up questionnaire were included (n = 138). Descriptive statistics summarized WFFs' baseline demographic, employment, and health characteristics. Linear mixed models were used to test for changes in WFFs' substance use over time and assess crew-level differences. A meta-analysis of WFF longitudinal studies' population characteristics was attempted to contextualize baseline findings. RESULTS: WFFs were predominately male, less than 35 yr of age, non-Hispanic White, and had healthy weight. Smokeless tobacco use and binge drinking were prevalent in this cohort (52% and 78%, respectively, among respondents). Longitudinal analyses revealed that during the fire season WFFs' use of tobacco and SSBs increased and the number of days they consumed alcohol decreased. Crew-level associations varied by substance. The meta-analysis was not completed due to cross-study heterogeneity and inconsistent reporting. DISCUSSION: WFF agencies can promote evidence-based substance use prevention and management programs and modify working conditions that may influence WFF stress or substance use.

Risk factors for heat-related illness resulting in death or hospitalization in the oil and gas extraction industry.

Many oil and gas extraction (OGE) activities occur in high-heat environments, resulting in a significant risk of heat-related illness among outdoor workers in this industry. This report highlights cases of occupational heat-related illness that resulted in death and identifies common risk factors for heat-related fatalities and hospitalizations among OGE workers. Two databases maintained by the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA) were reviewed to identify heat-related fatalities, hospitalizations, and associated risk factors among OGE workers. Nine fatalities and associated risk factors were identified during 2014-2019 from NIOSH's Fatalities in Oil and Gas Extraction (FOG) Database. Risk factors identified included those commonly associated with heat-related fatalities: new workers not acclimatized to heat, inadequate heat stress training, and underlying hypertension or cardiovascular disease. Of particular note, substance use was identified as a significant risk factor as more than half of the fatalities included a positive postmortem test for amphetamines or methamphetamines. Fifty heat-related hospitalizations were identified from OSHA's Severe Injury Report Database during January 2015-May 2021. Heat stress has been and will continue to be an important cause of fatality and adverse health effects in OGE as hot outdoor working conditions become more common and extreme. More emphasis on heat stress training, acclimatization regimens, medical screening, and implementation of workplace-supportive recovery programs may reduce heat-related fatalities and injuries in this industry.

Suicide Rates by Industry and Occupation - National Vital Statistics System, United States, 2021.

The suicide rate among the U.S. working-age population has increased approximately 33% during the last 2 decades. To guide suicide prevention strategies, CDC analyzed suicide deaths by industry and occupation in 49 states, using data from the 2021 National Vital Statistics System. Industry (the business activity of a person's employer or, if self-employed, their own business) and occupation (a person's job or the type of work they do) are distinct ways to categorize employment. The overall suicide rates by sex in the civilian noninstitutionalized working population were 32.0 per 100,000 among males and 8.0 per 100,000 among females. Major industry groups with the highest suicide rates included Mining (males = 72.0); Construction (males = 56.0; females = 10.4); Other Services (e.g., automotive repair; males = 50.6; females = 10.4); Arts, Entertainment, and Recreation (males = 47.9; females = 15.0); and Agriculture, Forestry, Fishing, and Hunting (males = 47.9). Major occupation groups with the highest suicide rates included Construction and Extraction (males = 65.6; females = 25.3); Farming, Fishing, and Forestry (e.g., agricultural workers; males = 49.9); Personal Care and Service (males = 47.1; females = 15.9); Installation, Maintenance, and Repair (males = 46.0; females = 26.6); and Arts, Design, Entertainment, Sports, and Media (males = 44.5; females = 14.1). By integrating recommended programs, practices, and training into existing policies, workplaces can be important settings for suicide prevention. CDC provides evidence-based suicide prevention strategies in its Suicide Prevention Resource for Action and Critical Steps Your Workplace Can Take Today to Prevent Suicide, NIOSH Science Blog.

Health conditions among male workers in mining and other industries reliant on manual labor occupations: National Health Interview Survey, 2007-2018.

INTRODUCTION: Mining is an industry with diverse, demanding occupational exposures. Understanding the prevalence of chronic health conditions in working miners is an area of active research. Of particular interest is how the health of miners compares to that of workers in other industry sectors with a high proportion of manual labor occupations. By comparing similar industries, we can learn what health conditions may be associated with manual labor and with individual industries. This study analyzes the prevalence of health conditions in miners compared to workers employed in other manual-labor-reliant industries. METHODS: National Health Interview Survey public data were analyzed for the years 2007-2018. Mining and five other industry groups with a high proportion of manual labor occupations were identified. Female workers were excluded because of small sample sizes. The prevalence of chronic health outcomes was calculated for each industry group and compared to that of nonmanual labor industries. RESULTS: Currently-working male miners showed increased prevalence of hypertension (in those age <55 years), hearing loss, lower back pain, leg pain progressing from lower back pain, and joint pain, compared to nonmanual labor industries workers. Construction workers also demonstrated a high prevalence of pain. CONCLUSION: Miners demonstrated increased prevalence of several health conditions, even when compared to other manual labor industries. Given previous research on chronic pain and opioid misuse, the high pain prevalence found among miners suggests mining employers should reduce work factors that cause injury while also providing an environment where workers can address pain management and substance use.

Fatalities Involving Substance Use Among US Oil and Gas Extraction Workers Identified Through an Industry Specific Surveillance System (2014-2019).

OBJECTIVE: Characteristics of oil and gas extraction (OGE) work, including long hours, shiftwork, fatigue, physically demanding work, and job insecurity are risk factors for substance use among workers. Limited information exists examining worker fatalities involving substance use among OGE workers. METHODS: The National Institute for Occupational Safety and Health's Fatalities in Oil and Gas Extraction database was screened for fatalities involving substance use from 2014 through 2019. RESULTS: Twenty-six worker deaths were identified as involving substance use. Methamphetamine or amphetamine was the most common substances (61.5%) identified. Other contributing factors were lack of seatbelt use (85.7%), working in high temperatures (19.2%), and workers' first day with the company (11.5%). CONCLUSIONS: Employer recommendations to mitigate substance use-related risks in OGE workers include training, medical screening, drug testing, and workplace supported recovery programs.

Working Alone and/or in Remote Locations: Opportunities to Prevent the Risk of Fatality From Cardiovascular Events in Oil and Gas Extraction Workers.

OBJECTIVE: The aim of the study is to explore personal and work factors related to fatal cardiac events among oil and gas extraction (OGE) workers. METHODS: The National Institute for Occupational Safety and Health Fatalities in Oil and Gas Extraction database was reviewed to identify fatal cardiac events among OGE workers from 2014 through 2019. A case series design was used to review case files, provide descriptive statistics, and summarize the findings. RESULTS: There were 75 fatalities identified, including 55 (73%) with sufficient information for review. Of the 55 workers, 18 (33%) worked alone. Thirty-six fatal cardiac events (66%) were unwitnessed by a coworker. Toxicology findings suggested some possible exposures to hydrogen sulfide or hydrocarbon gases or vapors. Missing data were common. CONCLUSIONS: This study identified the need for cardiovascular disease prevention and treatment, emergency preparedness, lone worker programs, medical screening, and enhanced exposure control in the OGE industry.

In vivo functional characterization of EGFR variants identifies novel drivers of glioblastoma.

BACKGROUND: Glioblastoma is the most common and aggressive primary brain tumor. Large-scale sequencing initiatives have cataloged its mutational landscape in hopes of elucidating mechanisms driving this deadly disease. However, a major bottleneck in harnessing this data for new therapies is deciphering "driver" and "passenger" events amongst the vast volume of information. METHODS: We utilized an autochthonous, in vivo screening approach to identify driver, EGFR variants. RNA-Seq identified unique molecular signatures of mouse gliomas across these variants, which only differ by a single amino acid change. In particular, we identified alterations to lipid metabolism, which we further validated through an unbiased lipidomics screen. RESULTS: Our screen identified A289I as the most potent EGFR variant, which has previously not been characterized. One of the mechanisms through which A289I promotes gliomagenesis is to alter cellular triacylglycerides through MTTP. Knockout of Mttp in mouse gliomas, reduces gliomagenesis in multiple models. CONCLUSIONS: EGFR variants that differ by a single amino acid residue differentially promote gliomagenesis. Among the identified mechanism that drives glioma growth include lipid metabolism through MTTP. Understanding triacylglyceride accumulation may present a prospective therapeutic pathway for this deadly disease.

Association of falls and fear of falling with objectively-measured driving habits among older drivers: LongROAD study.

OBJECTIVE: Falls in older adults are associated with increased motor vehicle crash risk, possibly mediated by driving behavior. We examined the relationship of falls and fear of falling (FOF) with subsequent objectively measured driving habits. METHODS: This multi-site, prospective cohort study enrolled 2990 active drivers aged 65-79 (53% female). At enrollment, we assessed falls in the past year and FOF (Short Falls Efficacy Scale-International). Driving outcomes included exposure, avoidance of difficult conditions, and unsafe driving during one-year follow-up, using in-vehicle Global Positioning System devices. RESULTS: Past-year falls were associated with more hard braking events (HBE). High FOF was associated with driving fewer days, miles, and trips, driving nearer home and more HBE. Differences were attenuated and not significant after accounting for health, function, medications and sociodemographics. DISCUSSION: Differences in objectively measured driving habits according to past-year fall history and FOF were largely accounted for by differences in health and medications. Rather than directly affecting driving, falls and FOF may serve as markers for crash risk and reduced community mobility due to age-related changes and poor health.

Self-reported exposure to hazards and mitigation strategies among oil and gas extraction workers in three U.S. states.

Numerous health and safety hazards exist at U.S. onshore oil and gas extraction worksites. Higher fatal injury rates have been reported among drilling and servicing companies, which are more likely to employ workers in construction and extraction occupations, compared to operators that employ more workers in management and office and administrative support roles. However, there is little information describing the extent to which workers encounter these hazards, are provided hazard mitigation strategies by their employers, or use personal protective equipment (PPE). A cross-sectional survey of 472 U.S. oil and gas extraction workers was conducted to identify and characterize factors related to on-the-job fatalities, injuries, and illnesses and determine workers' health and safety concerns. Workers were employed by servicing companies (271/472, 57.4%), drilling contractors (106/472, 22.5%), and operators (95/472, 20.1%). The likelihood of contact with hazardous substances varied by substance and company type. Drilling and servicing employees had significantly higher odds of self-reported contact with pipe dope (ORdrilling = 10.07, 95% CI: 1.74-63.64; ORservicing = 5.95, 95% CI: 2.18-18.34), diesel exhaust (ORdrilling = 2.28, 95% CI: 1.15-5.05; ORservicing = 4.93, 95% CI: 2.73-10.32), and drilling mud (ORdrilling = 24.36, 95% CI: 4.45-144.69; ORservicing = 3.48, 95% CI: 1.24-12.20), compared to operators. Safety policies, programs, and trainings were commonly reported by workers, although substance-specific training (e.g., respirable crystalline silica hazards) was less common. Differences in self-reported employer PPE requirements and worker use of PPE when needed or required for safety highlight a need for novel strategies to improve the use of PPE. Overall, this study highlights differences in work conditions by company type and uncovers gaps in employer administrative controls and PPE use.

A process to deduplicate individuals for regional chronic disease prevalence estimates using a distributed data network of electronic health records.

Introduction: Learning health systems can help estimate chronic disease prevalence through distributed data networks (DDNs). Concerns remain about bias introduced to DDN prevalence estimates when individuals seeking care across systems are counted multiple times. This paper describes a process to deduplicate individuals for DDN prevalence estimates. Methods: We operationalized a two-step deduplication process, leveraging health information exchange (HIE)-assigned network identifiers, within the Colorado Health Observation Regional Data Service (CHORDS) DDN. We generated prevalence estimates for type 1 and type 2 diabetes among pediatric patients (0-17 years) with at least one 2017 encounter in one of two geographically-proximate DDN partners. We assessed the extent of cross-system duplication and its effect on prevalence estimates. Results: We identified 218 437 unique pediatric patients seen across systems during 2017, including 7628 (3.5%) seen in both. We found no measurable difference in prevalence after deduplication. The number of cases we identified differed slightly by data reconciliation strategy. Concordance of linked patients' demographic attributes varied by attribute. Conclusions: We implemented an HIE-dependent, extensible process that deduplicates individuals for less biased prevalence estimates in a DDN. Our null pilot findings have limited generalizability. Overlap was small and likely insufficient to influence prevalence estimates. Other factors, including the number and size of partners, the matching algorithm, and the electronic phenotype may influence the degree of deduplication bias. Additional use cases may help improve understanding of duplication bias and reveal other principles and insights. This study informed how DDNs could support learning health systems' response to public health challenges and improve regional health.

A functional genomic approach to actionable gene fusions for precision oncology.

Fusion genes represent a class of attractive therapeutic targets. Thousands of fusion genes have been identified in patients with cancer, but the functional consequences and therapeutic implications of most of these remain largely unknown. Here, we develop a functional genomic approach that consists of efficient fusion reconstruction and sensitive cell viability and drug response assays. Applying this approach, we characterize ~100 fusion genes detected in patient samples of The Cancer Genome Atlas, revealing a notable fraction of low-frequency fusions with activating effects on tumor growth. Focusing on those in the RTK-RAS pathway, we identify a number of activating fusions that can markedly affect sensitivity to relevant drugs. Last, we propose an integrated, level-of-evidence classification system to prioritize gene fusions systematically. Our study reiterates the urgent clinical need to incorporate similar functional genomic approaches to characterize gene fusions, thereby maximizing the utility of gene fusions for precision oncology.

A Governance Framework to Integrate Longitudinal Clinical and Community Data in a Distributed Data Network: The Childhood Obesity Data Initiative.

CONTEXT: Integrating longitudinal data from community-based organizations (eg, physical activity programs) with electronic health record information can improve capacity for childhood obesity research. OBJECTIVE: A governance framework that protects individual privacy, accommodates organizational data stewardship requirements, and complies with laws and regulations was developed and implemented to support the harmonization of data from disparate clinical and community information systems. PARTICIPANTS AND SETTING: Through the Childhood Obesity Data Initiative (CODI), 5 Colorado-based organizations collaborated to expand an existing distributed health data network (DHDN) to include community-generated data and assemble longitudinal patient records for research. DESIGN: A governance work group expanded an existing DHDN governance infrastructure with CODI-specific data use and exchange policies and procedures that were codified in a governance plan and a delegated-authority, multiparty, reciprocal agreement. RESULTS: A CODI governance work group met from January 2019 to March 2020 to conceive an approach, develop documentation, and coordinate activities. Governance requirements were synthesized from the CODI use case, and a customized governance approach was constructed to address governance gaps in record linkage, a procedure to request data, and harmonizing community and clinical data. A Master Sharing and Use Agreement (MSUA) and Memorandum of Understanding were drafted and executed to support creation of linked longitudinal records of clinical- and community-derived childhood obesity data. Furthermore, a multiparty infrastructure protocol was approved by the local institutional review board (IRB) to expedite future CODI research by simplifying IRB research applications. CONCLUSION: CODI implemented a clinical-community governance strategy that built trust between organizations and allowed efficient data exchange within a DHDN. A thorough discovery process allowed CODI stakeholders to assess governance capacity and reveal regulatory and organizational obstacles so that the governance infrastructure could effectively leverage existing knowledge and address challenges. The MSUA and complementary governance documents can inform similar efforts.

The Childhood Obesity Data Initiative: A Case Study in Implementing Clinical-Community Infrastructure Enhancements to Support Health Services Research and Public Health.

CONTEXT: We describe a participatory framework that enhanced and implemented innovative changes to an existing distributed health data network (DHDN) infrastructure to support linkage across sectors and systems. Our processes and lessons learned provide a potential framework for other multidisciplinary infrastructure development projects that engage in a participatory decision-making process. PROGRAM: The Childhood Obesity Data Initiative (CODI) provides a potential framework for local and national stakeholders with public health, clinical, health services research, community intervention, and information technology expertise to collaboratively develop a DHDN infrastructure that enhances data capacity for patient-centered outcomes research and public health surveillance. CODI utilizes a participatory approach to guide decision making among clinical and community partners. IMPLEMENTATION: CODI's multidisciplinary group of public health and clinical scientists and information technology experts collectively defined key components of CODI's infrastructure and selected and enhanced existing tools and data models. We conducted a pilot implementation with 3 health care systems and 2 community partners in the greater Denver Metro Area during 2018-2020. EVALUATION: We developed an evaluation plan based primarily on the Good Evaluation Practice in Health Informatics guideline. An independent third party implemented the evaluation plan for the CODI development phase by conducting interviews to identify lessons learned from the participatory decision-making processes. DISCUSSION: We demonstrate the feasibility of rapid innovation based upon an iterative and collaborative process and existing infrastructure. Collaborative engagement of stakeholders early and iteratively was critical to ensure a common understanding of the research and project objectives, current state of technological capacity, intended use, and the desired future state of CODI architecture. Integration of community partners' data with clinical data may require the use of a trusted third party's infrastructure. Lessons learned from our process may help others develop or improve similar DHDNs.

A Cystine-Cysteine Intercellular Shuttle Prevents Ferroptosis in xCTKO Pancreatic Ductal Adenocarcinoma Cells.

In our previous study, we showed that a cystine transporter (xCT) plays a pivotal role in ferroptosis of pancreatic ductal adenocarcinoma (PDAC) cells in vitro. However, in vivo xCTKO cells grew normally indicating that a mechanism exists to drastically suppress the ferroptotic phenotype. We hypothesized that plasma and neighboring cells within the tumor mass provide a source of cysteine to confer full ferroptosis resistance to xCTKO PDAC cells. To evaluate this hypothesis, we (co-) cultured xCTKO PDAC cells with different xCT-proficient cells or with their conditioned media. Our data unequivocally showed that the presence of a cysteine/cystine shuttle between neighboring cells is the mechanism that provides redox and nutrient balance, and thus ferroptotic resistance in xCTKO cells. Interestingly, although a glutathione shuttle between cells represents a good alternative hypothesis as a "rescue-mechanism", our data clearly demonstrated that the xCTKO phenotype is suppressed even with conditioned media from cells lacking the glutathione biosynthesis enzyme. Furthermore, we demonstrated that prevention of lipid hydroperoxide accumulation in vivo is mediated by import of cysteine into xCTKO cells via several genetically and pharmacologically identified transporters (ASCT1, ASCT2, LAT1, SNATs). Collectively, these data highlight the importance of the tumor environment in the ferroptosis sensitivity of cancer cells.

POT1 Regulates Proliferation and Confers Sexual Dimorphism in Glioma.

Germline POT1 mutations are found in a spectrum of cancers and confer increased risk. Recently, we identified a series of novel germline POT1 mutations that predispose carrier families to the development of glioma. Despite these strong associations, how these glioma-associated POT1 mutations contribute to glioma tumorigenesis remains undefined. Here we show that POT1-G95C increases proliferation in glioma-initiating cells in vitro and in progenitor populations in the developing brain. In a native mouse model of glioma, loss of Pot1a/b resulted in decreased survival in females compared with males. These findings were corroborated in human glioma, where low POT1 expression correlated with decreased survival in females. Transcriptomic and IHC profiling of Pot1a/b-deficient glioma revealed that tumors in females exhibited decreased expression of immune markers and increased expression of cell-cycle signatures. Similar sex-dependent trends were observed in human gliomas that had low expression of POT1. Together, our studies demonstrate context-dependent functions for POT1 mutation or loss in driving progenitor proliferation in the developing brain and sexual dimorphism in glioma. SIGNIFICANCE: This study shows that manipulation of POT1 expression in glioma has sex-specific effects on tumorigenesis and associated immune signatures.