Activation of lysosomal iron triggers ferroptosis in cancer

Iron catalyses the oxidation of lipids in biological membranes and promotes a form of cell death referred to as ferroptosis1-3. Identifying where this chemistry takes place in the cell can inform the design of drugs capable of inducing or inhibiting ferroptosis in various disease-relevant settings. Whereas genetic approaches have revealed underlying mechanisms of lipid peroxide detoxification1,4,5, small molecules can provide unparalleled spatiotemporal control of the chemistry at work6. Here, we show that the ferroptosis inhibitor liproxstatin-1 (Lip-1) exerts a protective activity by inactivating iron in lysosomes. Based on this, we designed the bifunctional compound fentomycin that targets phospholipids at the plasma membrane and activates iron in lysosomes upon endocytosis, promoting oxidative degradation of phospholipids and ferroptosis. Fentomycin effectively kills primary sarcoma and pancreatic ductal adenocarcinoma cells. It acts as a lipolysis-targeting chimera (LIPTAC), preferentially targeting iron-rich CD44high cell-subpopulations7,8 associated with the metastatic disease and drug resistance9,10. Furthermore, we demonstrate that fentomycin also depletes CD44high cells in vivo and reduces intranodal tumour growth in an immunocompetent murine model of breast cancer metastasis. These data demonstrate that lysosomal iron triggers ferroptosis and that lysosomal iron redox chemistry can be exploited for therapeutic benefits.

AI is a viable alternative to high throughput screening: a 318-target study

High throughput screening (HTS) is routinely used to identify bioactive small molecules. This requires physical compounds, which limits coverage of accessible chemical space. Computational approaches combined with vast on-demand chemical libraries can access far greater chemical space, provided that the predictive accuracy is sufficient to identify useful molecules. Through the largest and most diverse virtual HTS campaign reported to date, comprising 318 individual projects, we demonstrate that our AtomNet® convolutional neural network successfully finds novel hits across every major therapeutic area and protein class. We address historical limitations of computational screening by demonstrating success for target proteins without known binders, high-quality X-ray crystal structures, or manual cherry-picking of compounds. We show that the molecules selected by the AtomNet® model are novel drug-like scaffolds rather than minor modifications to known bioactive compounds. Our empirical results suggest that computational methods can substantially replace HTS as the first step of small-molecule drug discovery.

Seasonal controls on stream metal(loid) signatures in mountainous discontinuous permafrost

We assess physical and chemical processes driving seasonal fluctuations in dissolved (<0.45 μm) trace metal(loid) concentrations in subarctic streams in discontinuous permafrost. Our analysis integrates multiple years of stream hydrometric and geochemical data with geochemical analyses of bedrock, permafrost, and active-layer samples. Three principal flow regimes govern stream hydrology: winter baseflow, spring freshet, and summer high flows. Metal(oid) concentrations in streams respond seasonally to these flow regimes. Baseflows are dominated by discharge of circumneutral-pH groundwater draining fractured bedrock. This discharge acts as a source of metals found as oxyanions or neutrally charged complexes, such as uranium and molybdenum. High stream flows are associated with peak concentrations of aluminium, cobalt, copper, iron, nickel, titanium, and vanadium. Concentrations of the metal cations aluminium, cobalt, copper, nickel, and titanium peak during freshet, when infiltration of snowmelt through organic-rich and moderately acidic soils favors their complexation with dissolved organic carbon. Concentrations of vanadium peak during summer high flows, likely reflecting flow through mineral soils in the active layer and involving reductive dissolution of iron(III)-(oxyhydr)oxides. The seasonal variation of arsenic concentrations is complex; at the majority of catchments it is sourced from shallow flowpaths in the active layer, but it can also be locally associated with discharge of deeper bedrock groundwater, which is spatially constrained by the presence of permafrost. Based on our analysis, we present a conceptual model that describes the flowpaths and processes governing metal(loid) release to streams in discontinuous permafrost. This model provides a framework upon which we consider changes in metal(loid) export into water resources in the context of thawing permafrost.

Radiotherapy-Induced Neurocognitive Impairment Is Driven by Heightened Apoptotic Priming in Early Life and Prevented by Blocking BAX

Although external beam radiotherapy (xRT) is commonly used to treat central nervous system (CNS) tumors in patients of all ages, young children treated with xRT frequently experience life-altering and dose-limiting neurocognitive impairment (NI) while adults do not. The lack of understanding of mechanisms responsible for these differences has impeded the development of neuroprotective treatments. Using a newly developed mouse model of xRT-induced NI, we found that neurocognitive function is impaired by ionizing radiation in a dose- and age-dependent manner, with the youngest animals being most affected. Histologic analysis revealed xRT-driven neuronal degeneration and cell death in neurogenic brain regions in young animals but not adults. BH3 profiling showed that neural stem and progenitor cells, neurons, and astrocytes in young mice are highly primed for apoptosis, rendering them hypersensitive to genotoxic damage. Analysis of single-cell RNA sequencing data revealed that neural cell vulnerability stems from heightened expression of proapoptotic genes including BAX, which is associated with developmental and mitogenic signaling by MYC. xRT induced apoptosis in primed neural cells by triggering a p53- and PUMA-initiated, proapoptotic feedback loop requiring cleavage of BID and culminating in BAX oligomerization and caspase activation. Notably, loss of BAX protected against apoptosis induced by proapoptotic signaling in vitro and prevented xRT-induced apoptosis in neural cells in vivo as well as neurocognitive sequelae. On the basis of these findings, preventing xRT-induced apoptosis specifically in immature neural cells by blocking BAX, BIM, or BID via direct or upstream mechanisms is expected to ameliorate NI in pediatric patients with CNS tumor.

SIGNIFICANCE

Age- and differentiation-dependent apoptotic priming plays a pivotal role in driving radiotherapy-induced neurocognitive impairment and can be targeted for neuroprotection in pediatric patients.

Evaluation of quantitative biomarkers of aging in human PBMCs

Functional decline with age contributes significantly to the burden of disease in developed countries. There is growing interest in the development of therapeutic interventions which slow or even reverse aging. Time and cost constraints prohibit the testing of a large number of interventions for health and lifespan extension in model organisms. Cell-based models of aging could enable high throughput testing of potential interventions. Despite extensive reports in the literature of cell properties that correlate with donor age, few are robustly observed across different laboratories. This casts doubt on the extent that aging signatures are captured in cultured cells. We tested molecular changes previously reported to correlate with donor age in peripheral blood mononuclear cells (PBMCs) and evaluated their suitability for inclusion in a panel of functional aging measures. The tested measures spanned several pathways implicated in aging including epigenetic changes, apoptosis, proteostasis, and intracellular communication. Surprisingly, only two markers correlated with donor age. DNA methylation age accurately predicted donor age confirming this is a robust aging biomarker. Additionally, the apoptotic marker CD95 correlated with donor age but only within subsets of PBMCs. To demonstrate cellular rejuvenation in response to a treatment will require integration of multiple read-outs of cell function. However, building a panel of measures to detect aging in cells is challenging and further research is needed to identify robust predictors of age in humans.

Abstract 5731: Apoptosis Inducing Agent 1 enhances cancer therapy-induced apoptosis by direct interaction with BAX and BAK

Many of the most effective anti-cancer therapies induce apoptosis in cancer cells by damaging DNA. Even when effective at eradicating primary cancers, DNA-damaging anti-cancer agents cause mutations that can lead to the development of secondary cancers. Furthermore, DNA damage responses are dependent on wild-type p53, which is mutated in over 50% of cancers and causes resistance to therapies. Fortunately, many p53 mutant cancers continue to express high levels of the pro-apoptotic, pore-forming proteins BAX and BAK and are consequently “primed for apoptosis.” Primed cells are highly sensitive to pro-apoptotic signals and this vulnerability can be exploited using inhibitors of pro-survival BCL-2 family proteins such as the BCL-2 inhibitor ABT-199, which has been successful as therapy for chronic lymphocytic and acute myeloid leukemias (AML). Furthermore, most irreplaceable cells within healthy tissues are apoptosis resistant and express low levels of BAX and BAK. We therefore hypothesized that direct activators of BAX or BAK could be effective single-agent therapies for primed cancers and chemo-/radio-sensitizers for unprimed cancers. Using WT versus BAX -/- BAK -/- HeLa cells, we performed a high-throughput screen of nearly 100,000 compounds to identify small molecules that could directly activate BAX or BAK. 196 compounds were identified as hits and multiple orthogonal validation studies identified Apoptosis Inducing Agent 1 (AIA1) as the most specific and potent putative activator of BAX and BAK. Further validation studies demonstrated that AIA1 directly induces cytochrome c release from mitochondria in a BAX/BAK dependent manner and strongly enhances BIM-mediated activation of BAX and BAK and permeabilization of liposomes. Single-agent AIA treatment triggers apoptotic cell death in a broad panel of cancer cell lines and also sensitizes cancer cells to chemotherapeutic agents and especially BH3 mimetics targeting pro-survival BCL-2 family proteins. Importantly, AIA1 sensitizes ovarian cancer cells to BCL-XL inhibitors and AML cells to BCL-2 inhibitors regardless of p53 status. In vivo, AIA1 suppresses tumor growth and prolongs overall survival in both ovarian cancer and AML xenograft models without causing weight loss, thrombocytopenia or leukopenia. Notably, unprimed cancer cells that don’t immediately undergo apoptosis in response to single-agent AIA1 treatment upregulate expression of BAX and BAK, pro-survival proteins (BCL-XL, BCL-2, MCL-1) and pro-apoptotic proteins (BIM, BID, PUMA, Noxa) to produce a more highly primed apoptosis pathway and setting the stage for increased sensitivity to BH3 mimetics. Based on these findings, AIA1 may exploit and induce apoptotic vulnerabilities in cancers in a p53-independent manner and represent a safer strategy to target primed cancer cells while eliminating the potential for secondary malignancies and p53-mediated resistance.

Citation Format: Xingping Qin, Cameron Fraser, Adam Presser, Johan KE Spetz, Stacey J. Yu, Gary A. Bradshaw, Marian Kalocsay, Bo R. Rueda, Tudor Moldoveanu, Kristopher A. Sarosiek. Apoptosis Inducing Agent 1 enhances cancer therapy-induced apoptosis by direct interaction with BAX and BAK. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5731.

Abstract 6130: Cancer sensitivity to therapy is constrained by apoptosis regulation in cells of origin

Many chemotherapeutic agents target cellular components or processes that are present in all cancers, yet clinical responses to these agents vary greatly between cancer types and even patient age - the basis for these broad-scale differences are unclear. The vast majority of targeted and cytotoxic cancer therapies including ionizing radiation produce pro-apoptotic signaling in exposed cells, suggesting that the mitochondrial apoptosis sensitivity of cancer cells could act as a central signaling “node” to broadly impact therapy outcomes. To test this, we used BH3 profiling and complementary chemosensitivity assays to analyze hundreds of primary cancer specimens across twelve major cancer types. We find that cancers with typically favorable outcomes including certain hematologic malignancies, testicular cancer, and some pediatric cancers contain mitochondria that are highly primed for apoptosis, which renders them hypersensitive to cytotoxic as well as targeted agents and radiation therapy. Priming levels in many epithelial cancers including ovarian cancer and non-small cell lung cancer are highly heterogeneous, mirroring their variability in clinical outcomes. Finally, many tumor types that are typically chemoresistant including adult soft tissue sarcomas, hepatocellular carcinoma and pancreatic cancer are almost completely resistant to pro-apoptotic signaling. By analyzing in vitro and in vivo pancreatic, ovarian, hepatocellular and sarcoma tumorigenesis models, we find that apoptotic priming generally increases during neoplastic transformation, in part due to consistent upregulation of pro-apoptotic proteins BAX and BAK. However, the level of apoptotic priming in cancer cells is constrained by the baseline apoptosis sensitivity of normal cells prior to transformation. Remarkably, we find that apoptotic priming is dynamically regulated by cell lineage and differentiation state but can also be modulated by oncogenes. For instance, Myc activation typically increases apoptotic priming while activation of mutant Ras signaling decreases it - these changes in priming alter the chemosensitivity of cancer cells. Finally, we use inducible mouse tumor models to demonstrate that neoplastic transformation of cells from developmentally immature tissues yields pediatric tumors that are more primed for apoptosis than equivalent tumors arising in adults. This difference in priming causes pediatric tumors to be more sensitive to front-line therapies and BH3 mimetics targeting pro-survival BCL-2 family proteins in vitro and in vivo. Thus, lineage-determined regulation of apoptosis prior to and during neoplastic transformation leads to broad-scale differences in cancer cell chemosensitivity and can be exploited therapeutically by targeting BCL-2 family proteins.

Citation Format: Cameron Fraser, Xingping Qin, Kenichi Shimada, Johan Spetz, Mary Heather Florido, Rumani Singh, Stacey Yu, Adam Presser, Zintis Inde, Gaurav Joshi, Jennifer Guerriero, Francisco Sanchez-Rivera, Alison Karst, Omar Lopez, Chendi Li, Peter Winter, Ying Yue, Peter Sorger, Jingwei Cheng, Izidore Lossos, Aaron Hata, Ronny Drapkin, Adam Palmer, James Decaprio, Manisha Thakuria, Charles Yoon, Ursula Matulonis, Matthew Meyerson, Elizabeth Stover, Diana Cardona, Kris Wood, Shayna Sarosiek, David Kirsch, Joseph Mancias, Andrew Cherniack, Anthony Letai, Kristopher Sarosiek. Cancer sensitivity to therapy is constrained by apoptosis regulation in cells of origin. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6130.

A11 NEXT STEPS IN MICRO-ELIMINATION: PEER POINT OF CARE HEPATITIS C TESTING IN VICTORIA, BRITISH COLUMBIA

Background

Canada is currently on target to reach the 2030 WHO goal of hepatitis C virus (HCV) elimination. Continued high rates of treatment initiation are required to meet this goal. People who use drugs (PWUD), account for the majority of new HCV cases in BC and continue to have many barriers to accessing DAA therapies, despite demonstrated high SVR rates in clinical trials. Improved elimination efforts including innovative outreach testing and treatment with this population are essential. Novel models have proven successful to engage PWUD in HCV therapy with a simplified, task-shifted cascade of care. Peer-based testing and support models have been piloted in other communities and may help connect to marginalized populations. People with lived and living experience of HCV treatment and drug use (peers) are seen as trusted sources of knowledge. Peers can vouch for the efficacy, minimal side effects and ease of HCV treatment that now exist in the current DAA era.

Purpose

The Peer HCV Point of Care (POC) testing project developed within our long standing nurse-led HCV treatment program seeks to determine whether an outreach peer model of HCV POC testing can be successful in Victoria, BC. The peer program focuses on finding populations who use drugs without regular access to primary care still living with HCV. This task shifting approach is the next phase of local micro-elimination efforts and has not been attempted previously.

Method

Six peers have been trained to provide HCV POC antibody and dried blood spot RNA tests. Our goals are to pilot the program, learn from our experiences, specifically from the direct input of peers to develop effective and supportive testing and treatment strategies. Peers have worked with nursing and research staff in two-hour blocks and are paid $26 per hour for these shifts. They provide testing at local supportive housing, shelters, social service sites and special events. Each client tested is offered a $10 incentive. Our peers are able to offer both POC antibody testing and, for those who have been exposed to HCV (currently infected, treated or cleared), RNA testing by dried blood spot. Serology by nursing from our mobile outreach van is collected as needed.

Result(s)

Within the first 4 months of the project peers and staff tested 304 people: 251 people with HCV POC antibody tests (227 negative and 24 positive results), 41 people with HCV dried blood spot RNA tests and 28 with nurse RNA serology. To date 12 people tested RNA+ (11 with previously unknown HCV have active RNA that require treatment), 7 people have been started on treatment.

Conclusion(s)

This innovative and novel approach to HCV therapy in PWUD was able to successfully use a peer-based approach to find people with limited connection to primary health care to test and treat HCV. We still have much to learn from the valuable knowledge, established relationships and novel perspectives of peers in our efforts to reduce barriers and reach PWUD and others who remain untreated.

Please acknowledge all funding agencies by checking the applicable boxes below

None

Disclosure of Interest

T. Barnett Grant / Research support from: AbbVie, Gilead, Merck, M. Selfridge Grant / Research support from: Kirby Institute, AbbVie, Gilead, Merck, ViiV, A. Drost Grant / Research support from: Abbvie, Gilead, Merck, K. Guarasci Grant / Research support from: Gliead, Abbvie, Merck , K. Lundgren Grant / Research support from: Abbvie, Gilead, Merck , C. Fraser Grant / Research support from: Abbvie, Gilead, Merck, Kirby Institute, ViiV, F. Boothman : None Declared

An acute case of Pimelea elongata toxicity in cattle in western New South Wales

In May 2019, 96 cattle died from Pimelea toxicity in a period of 19 days after potential exposure, with the first deaths occurring within 5 days. After examining the circumstances, we suspect that several factors contributed to the deaths. These included that recently purchased stock and transported had access to flooded land containing Pimelea elongata. This weed species contains simplexin and 18 other compounds. Roots, flowers and seeds are significantly more toxic than the stem, branches and leaves. We suspect that thirsty and hungry stock consumed seed and roots from flooded pastures and consumed lethal doses of simplexin. Blood tests were not good indicators of the conditions. Management strategies are suggested.

A Mesenchymal Tumor Cell State Confers Increased Dependency on the BCL-XL Antiapoptotic Protein in Kidney Cancer

PURPOSE

Advanced/metastatic forms of clear-cell renal cell carcinomas (ccRCC) have limited therapeutic options. Genome-wide genetic screens have identified cellular dependencies in many cancers. Using the Broad Institute/Novartis combined short hairpin RNA (shRNA) dataset, and cross-validation with the CRISPR/Cas9 DepMap (21Q3) dataset, we sought therapeutically actionable dependencies in kidney lineage cancers.

EXPERIMENTAL DESIGN

We identified preferential genetic dependencies in kidney cancer cells versus other lineages. BCL2L1, which encodes the BCL-XL antiapoptotic protein, scored as the top actionable dependency. We validated this finding using genetic and pharmacologic tools in a panel of ccRCC cell lines. Select BCL-XL-dependent (versus independent) cell lines were then transcriptionally profiled to identify biomarkers and mechanistic drivers of BCL-XL dependence. Cell-based studies (in vitro and in vivo) and clinical validations were used to address physiologic relevance.

RESULTS

Inactivation of BCL-XL, but not BCL-2, led to fitness defects in renal cancer cells, and sensitized them to chemotherapeutics. Transcriptomic profiling identified a "BCL-XL dependency" signature, including an elevated mesenchymal gene signature. A mesenchymal state was both necessary and sufficient to confer increased BCL-XL dependence. The "BCL-XL dependency" signature was observed in approximately 30% of human ccRCCs, which were also associated with worse clinical outcomes. Finally, an orally bioavailable BCL-XL inhibitor, A-1331852, showed antitumor efficacy in vivo.

CONCLUSIONS

Our studies uncovered an unexpected link between cell state and BCL-XL dependence in ccRCC. Therapeutic agents that specifically target BCL-XL are available. Our work justifies testing the utility of BCL-XL blockade to target, likely, a clinically aggressive subset of human kidney cancers. See related commentary by Wang et al., p. 4600.

Reciprocal effects of mTOR inhibitors on pro-survival proteins dictate therapeutic responses in tuberous sclerosis complex

mTORC1 is aberrantly activated in cancer and in the genetic tumor syndrome tuberous sclerosis complex (TSC), which is caused by loss-of-function mutations in the TSC complex, a negative regulator of mTORC1. Clinically approved mTORC1 inhibitors, such as rapamycin, elicit a cytostatic effect that fails to eliminate tumors and is rapidly reversible. We sought to determine the effects of mTORC1 on the core regulators of intrinsic apoptosis. In TSC2-deficient cells and tumors, we find that mTORC1 inhibitors shift cellular dependence from MCL-1 to BCL-2 and BCL-X_L for survival, thereby altering susceptibility to BH3 mimetics that target specific pro-survival BCL-2 proteins. The BCL-2/BCL-X_L inhibitor ABT-263 synergizes with rapamycin to induce apoptosis in TSC-deficient cells and in a mouse tumor model of TSC, resulting in a more complete and durable response. These data expose a therapeutic vulnerability in regulation of the apoptotic machinery downstream of mTORC1 that promotes a cytotoxic response to rapamycin.

Statistical and agent-based modelling of the transmissibility of different SARS-CoV-2 variants in England and impact of different interventions

The English SARS-CoV-2 epidemic has been affected by the emergence of new viral variants such as B.1.177, Alpha and Delta, and changing restrictions. We used statistical models and the agent-based model Covasim, in June 2021, to estimate B.1.177 to be 20% more transmissible than the wild type, Alpha to be 50-80% more transmissible than B.1.177 and Delta to be 65-90% more transmissible than Alpha. Using these estimates in Covasim (calibrated 1 September 2020 to 20 June 2021), in June 2021, we found that due to the high transmissibility of Delta, resurgence in infections driven by the Delta variant would not be prevented, but would be strongly reduced by delaying the relaxation of restrictions by one month and with continued vaccination. This article is part of the theme issue 'Technical challenges of modelling real-life epidemics and examples of overcoming these'.

Statistical and agent-based modelling of the transmissibility of different SARS-CoV-2 variants in England and impact of different interventions

The English SARS-CoV-2 epidemic has been affected by the emergence of new viral variants such as B.1.177, Alpha and Delta, and changing restrictions. We used statistical models and the agent-based model Covasim, in June 2021, to estimate B.1.177 to be 20% more transmissible than the wild type, Alpha to be 50-80% more transmissible than B.1.177 and Delta to be 65-90% more transmissible than Alpha. Using these estimates in Covasim (calibrated 1 September 2020 to 20 June 2021), in June 2021, we found that due to the high transmissibility of Delta, resurgence in infections driven by the Delta variant would not be prevented, but would be strongly reduced by delaying the relaxation of restrictions by one month and with continued vaccination. This article is part of the theme issue 'Technical challenges of modelling real-life epidemics and examples of overcoming these'.

Abstract 2150: LKB1 loss rewires JNK-induced apoptotic protein dynamics through NUAKs and sensitizes KRAS-mutant non-small cell lung cancers to combined KRAS G12C + MCL-1 blockade

The recent approval of the KRAS G12C inhibitor sotorasib (AMG 510) for non-small cell lung cancer (NSCLC) marked a milestone in the development of targeted therapies for KRAS mutant cancers. While sotorasib and other KRAS G12C inhibitors have demonstrated rapid and durable responses in the clinic, some patients do not achieve responses. The identification of specific vulnerabilities conferred by recurrent co-occurring mutations may enable the development of biomarker-driven combination therapies with enhanced activity in distinct subsets of patients. We screened a panel of KRAS-mutant NSCLC cell lines as well as patient-derived xenograft (PDX) mouse models and observed that loss of the tumor suppressor STK11/LKB1 is associated with increased sensitivity to combined MAPK (either the KRAS G12C inhibitor sotorasib or MEK inhibitor trametinib) and MCL-1 inhibition (AMG 176). Restoration of LKB1 expression in LKB1-deficient cell lines and PDX tumors blunted the apoptotic response to MAPK + MCL-1 inhibition; conversely, deletion of LKB1 in LKB1 wild-type models increased sensitivity. Mitochondrial apoptotic cell death is regulated by interactions between pro- (e.g., BIM) and anti-apoptotic (e.g., MCL-1, BCL-XL) BCL-2 family members. MAPK inhibition increases BIM, while MCL-1 inhibition prevents BIM sequestration by MCL-1, resulting in apoptosis. LKB1 deficient cells exhibit increased association of BIM and MCL-1 upon MAPK inhibition, effectively priming cells for death upon inhibition of MCL-1. Mechanistically, LKB1 deficiency and associated loss of NUAK phosphorylation leads to hyperactivation of the JNK phospho-kinase network. JNK phosphorylates MCL-1 at S64 and T163, which enhances BIM: MCL-1 protein-protein interaction. Conversely, JNK phosphorylates BCL-XL at S62 and prevents sequestration of BIM. This series of phosphorylation events increases MCL-1 dependence and creates a specific vulnerability of KRAS-LKB1 tumors to MAPK + MCL-1 inhibition. Consistent with this mechanism, ex vivo treatment of tumor tissue from a KRAS-LKB1 mutant NSCLC patient with sotorasib or trametinib increased MCL-1 dependent priming. These results reveal a novel link between LKB1 and the regulation of BCL-2 family proteins and provide preclinical rationale for evaluation of combined KRAS G12C + MCL-1 inhibitors for KRAS-LKB1 mutant NSCLC.

Citation Format: Chendi Li, Mohammed Usman Syed, Yi Shen, Audris Oh, Cameron Fraser, Johannes Kreuzer, Christopher Nabel, Kaitlyn Webster, Robert Morris, Sean Caenepeel, Anne Y. Saiki, Karen Rex, J. Russell Lipford, Wilhelm Hass, Kristopher Sarosiek, Paul E. Hughes, Aaron Hata. LKB1 loss rewires JNK-induced apoptotic protein dynamics through NUAKs and sensitizes KRAS-mutant non-small cell lung cancers to combined KRAS G12C + MCL-1 blockade [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 2150.

AB0602 Temporal artery biopsy positivity rates vary more between similar hospitals than by length, with particular variation between geographic regions

Background

Clinical practice surrounding giant cell arteritis (GCA) diagnosis, including the use of temporal artery biopsy (TAB) where appropriate, needs to be consistently accurate to minimise both GCA-related end-organ damage and unnecessary glucocorticosteroid toxicity in all patients. Despite this imperative, the delivery of such clinical care, which can be measured by diagnostic investigation performance characteristics such as TAB positivity rates, varies substantially between different hospitals as it is traditionally reliant on unstructured clinical intuition. While clinical care practices plausibly might be more consistent between neighbouring hospitals given they frequently exchange medical staff and use common teaching sources, these factors are less likely to be applicable when comparing hospitals in different geographical regions within a country, even though educational standards, online information resources, and access to clinical care should be consistent. It therefore stands to reason that variation of diagnostic practice might be greater between geographically distant hospitals.

Objectives

To compare clinical practice surrounding GCA diagnosis, using TAB positivity rates, between similar hospitals in the same city and a geographically distant city in a different region, to understand the contribution of geographic separation to variance in practice.

Methods

TAB histopathological reports were reviewed at three tertiary referral hospital centres: two with neighbouring catchments in the same city, and one in a different city in a neighbouring geographical region in the same country. All three had similar resourcing and catchment demographics during the study period, and none used formal clinical risk stratification scores for GCA pre-test probability. Characteristics including age, sex, biopsy laterality, biopsy length, and hospital were captured, in addition to key histopathological features. Multivariable logistic regression with site-varying intercept was performed, using cubic splines for biopsy length to account for the non-linearity observed.

Results

TAB reports from 708 patients were captured between the three hospitals in two geographical regions. All three sites had a median age of 74 years, had 67-69% of patients being female, and reported median biopsy length between 1.7-2.0cm (Table 1). Despite these similarities, they reported positivity rates varying widely (16% and 24% in Region 1, 29% in Region 2). Apart from age, hospital site was the strongest contributing factor to TAB positivity, with length having little effect outside the very extreme high end and 90% of patients had a biopsy length <4.8cm (Figure 1). For these patients, hospital site differentiated TAB positivity across all biopsy lengths, with Region 2 reporting the highest TAB positivity odds ratio of 2.39 (95%CI: 1.37-4.19).

Table 1.CharacteristicSite1Region1 N = 218Site2Region1 N = 361Site1Region2 N = 129Bilateral laterality (%)66 (30%)105 (29%)1 (0.8%)Biopsy length (cm, median (IQR))2.0 (1.4, 3.0)1.7 (1.2, 3.5)1.7 (1.4, 2.2)Female sex (%)149 (68%)249 (69%)86 (67%)Age (y, median (IQR))74 (65, 81)74 (65, 80)74 (68, 81)TAB positivity (%)34 (16%)88 (24%)38 (29%)Figure 1.

Marginal probabilities of positive TAB obtained from the multivariable logistic regression model (A) across biopsy lengths, with 80% of observed lengths falling between the two vertical red lines (10% and 90% deciles); (B) across hospital sites; (C) across patient age.

Conclusion

Hospital site contributes more greatly to variation in GCA diagnosis clinical practice than demographics or other clinical features do, with particular variation between geographic regions. As part of clinical care standards, using a replicable pre-test GCA probability score1 to select patients is likely to be as important to diagnosis as the diagnostic tool characteristics themselves.

References

[1]Laskou F, et al. A probability score to aid the diagnosis of suspected giant cell arteritis. Clin Exp Rheumatol. 2019 Jan 1;37(Suppl 117):104-8.

Disclosure of Interests

None declared

77 INCONTINENCE AND DECONDITIONING IN A NONFRAIL SAMPLE OF INPATIENTS AT A UNIVERSITY TEACHING HOSPITAL

Background

Incontinence occurs in 26% of hospitalised adults1. Deconditioning in hospitalised adults is common and contributes to increased hospital stay2. The #endpjparalysis movement motivates us to reduce harms of hospitalisation older adults.

Methods

We surveyed inpatients to capture the point prevalence of incontinence. We also collected information regarding functional status, continence status and use of continence wear. Local ethical review-board approval was obtained. All participants provided informed consent.

Results

There were 86 responses. Mean age of participants was 71.5 years. 45.4% were female, &gt;95% were admitted from home and were functionally independent. Mean length of stay for respondents was 7.4 days ±12. The median Clinical Frailty Scale, for respondents aged &gt;65 years, was 3, indicating this cohort is not frail.

17 respondents reported incontinence on the day of survey; 8 of these reported that incontinence was a new experience for them since their admission. 24 respondents wore incontinence wear at home, 31 were wearing incontinence wear on the day of survey.

Of 80 respondents who could toilet independently at home, 23 (26%) reported a new dependency to toilet. Of 83 respondents who mobilised independently at home (with or without an aid), 11 reported needing assistance of one-person to walk, 3 needed the assistance of two-people to walk or stand, five people required a hoist, while 3 were bedbound on the day of survey.

Conclusion

We describe increased dependency in mobility, toileting and increased use of continence wear in non-frail hospitalised older adults. Future work is needed to maintain function during admission to hospital.

References

1. Condon, M., et al. (2019). ‘Urinary and Faecal Incontinence: Point Prevalence and Predictors in a University Hospital.’ Int J Environ Res Public Health 16.

2. Guilcher, S., et al. (2021). ‘A qualitative study exploring the lived experiences of deconditioning in hospital in Ontario, Canada.’ BMC Geriatrics 21.

Age-dependent regulation of SARS-CoV-2 cell entry genes and cell death programs correlates with COVID-19 severity

Novel coronavirus disease 2019 (COVID-19) severity is highly variable, with pediatric patients typically experiencing less severe infection than adults and especially the elderly. The basis for this difference is unclear. We find that mRNA and protein expression of angiotensin-converting enzyme 2 (ACE2), the cell entry receptor for the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes COVID-19, increases with advancing age in distal lung epithelial cells. However, in humans, ACE2 expression exhibits high levels of intra- and interindividual heterogeneity. Further, cells infected with SARS-CoV-2 experience endoplasmic reticulum stress, triggering an unfolded protein response and caspase-mediated apoptosis, a natural host defense system that halts virion production. Apoptosis of infected cells can be selectively induced by treatment with apoptosis-modulating BH3 mimetic drugs. Notably, epithelial cells within young lungs and airways are more primed to undergo apoptosis than those in adults, which may naturally hinder virion production and support milder COVID-19 severity.

Abstract 982: LKB1 loss rewires stress signaling-induced apoptotic protein dynamics and sensitizes KRAS-mutant non-small cell lung cancers to combined MAPK + MCL-1 blockade

Background: There are currently no approved targeted therapies for KRAS-mutant non-small cell lung cancers (NSCLC), which represent 25-30% of lung adenocarcinomas. The development of mutant-specific covalent inhibitors of KRAS G12C has invigorated hope that clinically effective KRAS-targeted therapies are within reach. While these agents have shown activity in early phase clinical trials, identification of specific vulnerabilities conferred by common co-occurring mutations in KRAS-mutant NSCLC may enable development of combination therapies with enhanced activity in distinct subsets of patients.

Results: We screened a panel of KRAS-mutant NSCLC cell lines and observed that loss of the tumor suppressor STK11/LKB1 is associated with increased MCL-1 dependence and sensitivity to combined MAPK (either MEK inhibitor or KRAS G12C inhibitor AMG 510) and MCL-1 inhibition (AMG 176). Restoration of LKB1 expression in LKB1-deficient cell lines and mouse xenograft tumors blunted the apoptotic response to MAPK + MCL-1 inhibition; conversely, deletion of LKB1 in LKB1 wild-type models restored the sensitivity. Mechanistically, LKB1 deficiency is associated with an altered phosphoproteome and increased MCL-1-dependent apoptotic priming. LKB1 loss increased cellular stress leading to hyperactivation of JNK1, phosphorylation and stabilization of MCL-1 protein, and increased BIM sequestration by MCL-1. Upon suppression of MAPK signaling, LKB1-deficient cells exhibited greater levels of BIM bound to MCL-1 that could be liberated by AMG 176 to induce apoptosis. Consistent with these results, ex vivo treatment of tumor tissue from a KRAS-LKB1 mutant NSCLC patient with MEK inhibitor or AMG 510 increased MCL-1 dependent priming.

Conclusion: These results uncover a novel link between LKB1, cellular stress, and the regulation of MCL-1. LKB1 loss confers a dependency on MCL-1 that can be exploited therapeutically. Moreover, our study provides preclinical rationale for the exploration of combined KRAS G12C + MCL-1 inhibitors, particularly for KRAS-LKB1 mutant patients who respond poorly to standard-of-care checkpoint inhibitor therapy.

Citation Format: Chendi Li, Yi Shen, Mohammed Usman Syed, Audris Oh, Cameron Fraser, Johannes Kreuzer, Kaitlyn Webster, Robert Morris, Sean Caenepeel, Anne Y. Saiki, Karen Rex, James Lipford, Wilhelm Hass, Kristopher Sarosiek, Paul E. Hughes, Aaron N. Hata. LKB1 loss rewires stress signaling-induced apoptotic protein dynamics and sensitizes KRAS-mutant non-small cell lung cancers to combined MAPK + MCL-1 blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 982.

Age-dependent regulation of SARS-CoV-2 cell entry genes and cell death programs correlates with COVID-19 disease severity

Angiotensin-converting enzyme 2 (ACE2) maintains cardiovascular and renal homeostasis but also serves as the entry receptor for the novel severe acute respiratory syndrome coronavirus (SARS-CoV-2), the causal agent of novel coronavirus disease 2019 (COVID-19). COVID-19 disease severity is typically lower in pediatric patients than adults (particularly the elderly), but higher rates of hospitalizations requiring intensive care are observed in infants than in older children - the reasons for these differences are unknown. ACE2 is expressed in several adult tissues and cells, including alveolar type 2 cells of the distal lung epithelium, but expression at other ages is largely unexplored. Here we show that ACE2 transcripts are expressed in the lung and trachea shortly after birth, downregulated during childhood, and again expressed at high levels in late adulthood. Notably, the repertoire of cells expressing ACE2 protein in the mouse lung and airways shifts during key phases of lung maturation. In particular, podoplanin-positive cells, which are likely alveolar type I cells responsible for gas exchange, express ACE2 only in advanced age. Similar patterns of expression were evident in analysis of human lung tissue from over 100 donors, along with extreme inter- and intra-individual heterogeneity in ACE2 protein expression in epithelial cells. Furthermore, we find that apoptosis, which is a natural host defense system against viral infection, is dynamically regulated during lung maturation, resulting in periods of heightened apoptotic priming and dependence on pro-survival BCL-2 family proteins including MCL-1. Infection of human lung cells with SARS-CoV-2 triggers an unfolded protein stress response and upregulation of the endogenous MCL-1 inhibitor Noxa; in young individuals, MCL-1 inhibition is sufficient to trigger apoptosis in lung epithelial cells and may thus limit virion production and inflammatory signaling. Overall, we identify strong and distinct correlates of COVID-19 disease severity across lifespan and advance our understanding of the regulation of ACE2 and cell death programs in the mammalian lung. Furthermore, our work provides the framework for translation of apoptosis modulating drugs as novel treatments for COVID-19.

Mechanisms of Lymphoma Clearance Induced by High-Dose Alkylating Agents

The extraordinary activity of high-dose cyclophosphamide against some high-grade lymphomas was described nearly 60 years ago. Here we address mechanisms that mediate cyclophosphamide activity in bona fide human double-hit lymphoma. We show that antibody resistance within the bone marrow (BM) is not present upon early engraftment but develops during lymphoma progression. This resistance required a high tumor:macrophage ratio, was recapitulated in spleen by partial macrophage depletion, and was overcome by multiple, high-dose alkylating agents. Cyclophosphamide induced endoplasmic reticulum (ER) stress in BM-resident lymphoma cells in vivo that resulted in ATF4-mediated paracrine secretion of VEGFA, massive macrophage infiltration, and clearance of alemtuzumab-opsonized cells. BM macrophages isolated after cyclophosphamide treatment had increased phagocytic capacity that was reversed by VEGFA blockade or SYK inhibition. Single-cell RNA sequencing of these macrophages identified a "super-phagocytic" subset that expressed CD36/FCGR4. Together, these findings define a novel mechanism through which high-dose alkylating agents promote macrophage-dependent lymphoma clearance. SIGNIFICANCE: mAbs are effective against only a small subset of cancers. Herein, we recapitulate compartment-specific antibody resistance and define an ER stress-dependent mechanism induced by high-dose alkylating agents that promotes phagocytosis of opsonized tumor cells. This approach induces synergistic effects with mAbs and merits testing across additional tumor types.See related commentary by Duval and De Palma, p. 834.This article is highlighted in the In This Issue feature, p. 813.

Uveitis and optic perineuritis in the context of myelin oligodendrocyte glycoprotein antibody seropositivity

BACKGROUND AND PURPOSE

Antibodies to myelin oligodendrocyte glycoprotein (MOG) have been identified in both children and adults with demyelination, with a strong association with bilateral or recurrent optic neuritis (ON). However, the full clinical spectrum of this newly described condition is unknown. We sought to describe non-ON inflammatory ophthalmological presentations such as uveitis and optic perineuritis in the context of MOG antibody seropositivity.

METHODS

Using a live cell-based assay analysed by flow cytometry, we identified seropositive patients referred for MOG antibody testing in Australasia between 2014 and 2017. We identified four MOG antibody-positive patients with non-ON inflammatory ophthalmological presentations and present their detailed clinical information in this case series.

RESULTS

Three patients had uveitis either in association with, or remote from, ON. One patient had optic perineuritis and peripheral ulcerative keratitis. We describe the presentation, examination, investigation findings and clinical course of these four patients.

CONCLUSIONS

Recognition of these novel clinical associations may expand the clinical spectrum of MOG antibody-associated presentations. An expedited diagnosis may guide the management of these complex patients.

BH3 Profiling: A Functional Assay to Measure Apoptotic Priming and Dependencies

Apoptosis (programmed cell death) is activated by a wide variety of cellular stresses or insults and is vital for proper mammalian development as well as the maintenance of organismal homeostasis. The apoptosis pathway is also engaged by many common types of anticancer therapies and ionizing radiation, which contributes to the regressions of tumors or the toxic side effects of treatment. Due to the importance of maintaining healthy cell survival or the efficient clearance of cancer cells, the BH3 profiling assay was developed to functionally measure the state of the apoptosis pathway in any given cells. This assay involves the exposure of cellular mitochondria, where the BCL-2 family of proteins resides and controls the commitment to apoptosis, to proapoptotic BH3 peptides that mimic the activity of endogenous proapoptotic proteins. By using either activator or sensitizer peptides, the level of mitochondrial apoptotic priming (proximity to the threshold at which a cell commits to cell death) or dependence on prosurvival BCL-2 family proteins can be determined. Described here are two methods of BH3 profiling that can enable a user to make these functional measurements, which can be useful for predicting cellular responses to proapoptotic stressors or therapeutics (BH3 mimetics) that inhibit the activity of prosurvival proteins.

Exploiting MCL1 Dependency with Combination MEK + MCL1 Inhibitors Leads to Induction of Apoptosis and Tumor Regression in KRAS-Mutant Non-Small Cell Lung Cancer

BH3 mimetic drugs, which inhibit prosurvival BCL2 family proteins, have limited single-agent activity in solid tumor models. The potential of BH3 mimetics for these cancers may depend on their ability to potentiate the apoptotic response to chemotherapy and targeted therapies. Using a novel class of potent and selective MCL1 inhibitors, we demonstrate that concurrent MEK + MCL1 inhibition induces apoptosis and tumor regression in KRAS-mutant non-small cell lung cancer (NSCLC) models, which respond poorly to MEK inhibition alone. Susceptibility to BH3 mimetics that target either MCL1 or BCL-xL was determined by the differential binding of proapoptotic BCL2 proteins to MCL1 or BCL-xL, respectively. The efficacy of dual MEK + MCL1 blockade was augmented by prior transient exposure to BCL-xL inhibitors, which promotes the binding of proapoptotic BCL2 proteins to MCL1. This suggests a novel strategy for integrating BH3 mimetics that target different BCL2 family proteins for KRAS-mutant NSCLC. SIGNIFICANCE: Defining the molecular basis for MCL1 versus BCL-xL dependency will be essential for effective prioritization of BH3 mimetic combination therapies in the clinic. We discover a novel strategy for integrating BCL-xL and MCL1 inhibitors to drive and subsequently exploit apoptotic dependencies of KRAS-mutant NSCLCs treated with MEK inhibitors.See related commentary by Leber et al., p. 1511.This article is highlighted in the In This Issue feature, p. 1494.

Evaluation of a co-delivered training package for community mental health professionals on service user- and carer-involved care planning

WHAT IS KNOWN ON THE SUBJECT?: There is consistent evidence that service users and carers feel marginalized in the process of mental health care planning. Mental health professionals have identified ongoing training needs in relation to involving service users and carers in care planning. There is limited research on the acceptability of training packages for mental health professionals which involve service users and carers as co-facilitators. WHAT DOES THIS PAPER ADD TO EXISTING KNOWLEDGE?: A co-produced and co-delivered training package on service user- and carer-involved care planning was acceptable to mental health professionals. Aspects of the training that were particularly valued were the co-production model, small group discussion and the opportunity for reflective practice. The organizational context of care planning may need more consideration in future training models. WHAT ARE THE IMPLICATIONS FOR PRACTICE?: Mental health nurses using co-production models of delivering training to other mental health professionals can be confident that such initiatives will be warmly welcomed, acceptable and engaging. On the basis of the results reported here, we encourage mental health nurses to use co-production approaches more often. Further research will show how clinically effective this training is in improving outcomes for service users and carers.

ABSTRACT

Background There is limited evidence for the acceptability of training for mental health professionals on service user- and carer-involved care planning. Aim To investigate the acceptability of a co-delivered, two-day training intervention on service user- and carer-involved care planning. Methods Community mental health professionals were invited to complete the Training Acceptability Rating Scale post-training. Responses to the quantitative items were summarized using descriptive statistics (Miles, ), and qualitative responses were coded using content analysis (Weber, ). Results Of 350 trainees, 310 completed the questionnaire. The trainees rated the training favourably (median overall TARS scores = 56/63; median 'acceptability' score = 34/36; median 'perceived impact' score = 22/27). There were six qualitative themes: the value of the co-production model; time to reflect on practice; delivery preferences; comprehensiveness of content; need to consider organizational context; and emotional response. Discussion The training was found to be acceptable and comprehensive with participants valuing the co-production model. Individual differences were apparent in terms of delivery preferences and emotional reactions. There may be a need to further address the organizational context of care planning in future training. Implications for practice Mental health nurses should use co-production models of continuing professional development training that involve service users and carers as co-facilitators.

EQUIP training the trainers: an evaluation of a training programme for service users and carers involved in training mental health professionals in user-involved care planning

WHAT IS KNOWN ON THE SUBJECT?: UK NHS policy highlights the importance of user and carer involvement in health professional training. We know little about service user and carer motivations and experiences of accessing training courses for delivering training to health professionals and how well such courses prepare them for delivering training to healthcare professionals. 'Involvement' in training has often been tokenistic and too narrowly focused on preregistration courses. There is limited data on how best to prepare and support potential service user and carer trainers. WHAT DOES THIS PAPER ADD TO EXISTING KNOWLEDGE?: This study adds to the international literature by highlighting service user and carer motivations for accessing a training course for delivering training to health professionals. Service users and carers wanted to gain new skills and confidence in presentation/facilitation as well as to make a difference to healthcare practice. We also learned that service users desired different levels of involvement in training facilitation - some wanted to take a more active role than others. A one-size-fits-all approach is not always appropriate. Encountering resistance from staff in training was a previously unidentified challenge to service user and carers' experience of delivering training in practice and is a key challenge for trainers to address in future. Professional training involvement can be enhanced via specialist training such as the EQUIP training the trainers programme evaluated here. WHAT ARE THE IMPLICATIONS FOR PRACTICE?: When training service users and carers to deliver training to mental health professionals, it is important that service users are equipped to deal with resistance from staff. It is important that service user and carer roles are negotiated and agreed prior to delivering training to healthcare professionals to accommodate individual preferences and allay anxieties. Training for service users and carers must be offered alongside ongoing support and supervision. Mental health nurses (and other health professionals) will be better able to involve service users and carers in care planning. Service users and carers may feel more involved in care planning in future.

ABSTRACT

Introduction Limited evidence exists on service user and carer perceptions of undertaking a training course for delivering care planning training to qualified mental health professionals. We know little about trainee motivations for engaging with such train the trainers courses, experiences of attending courses and trainees' subsequent experiences of codelivering training to health professionals, hence the current study. Aim To obtain participants' views on the suitability and acceptability of a training programme that aimed to prepare service users and carers to codeliver training to health professionals. Method Semi-structured interviews with nine service users and carers attending the training programme. Transcripts were analysed using inductive thematic analysis. Results Participants' reasons for attending training included skill development and making a difference to mental health practice. Course content was generally rated highly but may benefit from review and/or extension to allow the range of topics and resulting professional training programme to be covered in more depth. Trainees who delivered the care planning training reported a mix of expectations, support experiences, preparedness and personal impacts. Implications for Practice Mental health nurses are increasingly coproducing and delivering training with service users and carers. This study identifies possibilities and pitfalls in this endeavour, highlighting areas where user and carer involvement and support structures might be improved in order to fully realize the potential for involvement in training.

Genome-wide association study of borderline personality disorder reveals genetic overlap with bipolar disorder, major depression and schizophrenia

Borderline personality disorder (BOR) is determined by environmental and genetic factors, and characterized by affective instability and impulsivity, diagnostic symptoms also observed in manic phases of bipolar disorder (BIP). Up to 20% of BIP patients show comorbidity with BOR. This report describes the first case-control genome-wide association study (GWAS) of BOR, performed in one of the largest BOR patient samples worldwide. The focus of our analysis was (i) to detect genes and gene sets involved in BOR and (ii) to investigate the genetic overlap with BIP. As there is considerable genetic overlap between BIP, major depression (MDD) and schizophrenia (SCZ) and a high comorbidity of BOR and MDD, we also analyzed the genetic overlap of BOR with SCZ and MDD. GWAS, gene-based tests and gene-set analyses were performed in 998 BOR patients and 1545 controls. Linkage disequilibrium score regression was used to detect the genetic overlap between BOR and these disorders. Single marker analysis revealed no significant association after correction for multiple testing. Gene-based analysis yielded two significant genes: DPYD (P=4.42 × 10-7) and PKP4 (P=8.67 × 10-7); and gene-set analysis yielded a significant finding for exocytosis (GO:0006887, PFDR=0.019; FDR, false discovery rate). Prior studies have implicated DPYD, PKP4 and exocytosis in BIP and SCZ. The most notable finding of the present study was the genetic overlap of BOR with BIP (rg=0.28 [P=2.99 × 10-3]), SCZ (rg=0.34 [P=4.37 × 10-5]) and MDD (rg=0.57 [P=1.04 × 10-3]). We believe our study is the first to demonstrate that BOR overlaps with BIP, MDD and SCZ on the genetic level. Whether this is confined to transdiagnostic clinical symptoms should be examined in future studies.

Developmental Regulation of Mitochondrial Apoptosis by c-Myc Governs Age- and Tissue-Specific Sensitivity to Cancer Therapeutics

It is not understood why healthy tissues can exhibit varying levels of sensitivity to the same toxic stimuli. Using BH3 profiling, we find that mitochondria of many adult somatic tissues, including brain, heart, and kidneys, are profoundly refractory to pro-apoptotic signaling, leading to cellular resistance to cytotoxic chemotherapies and ionizing radiation. In contrast, mitochondria from these tissues in young mice and humans are primed for apoptosis, predisposing them to undergo cell death in response to genotoxic damage. While expression of the apoptotic protein machinery is nearly absent by adulthood, in young tissues its expression is driven by c-Myc, linking developmental growth to cell death. These differences may explain why pediatric cancer patients have a higher risk of developing treatment-associated toxicities.

Clonal evolution in patients with chronic lymphocytic leukaemia developing resistance to BTK inhibition

Resistance to the Bruton's tyrosine kinase (BTK) inhibitor ibrutinib has been attributed solely to mutations in BTK and related pathway molecules. Using whole-exome and deep-targeted sequencing, we dissect evolution of ibrutinib resistance in serial samples from five chronic lymphocytic leukaemia patients. In two patients, we detect BTK-C481S mutation or multiple PLCG2 mutations. The other three patients exhibit an expansion of clones harbouring del(8p) with additional driver mutations (EP300, MLL2 and EIF2A), with one patient developing trans-differentiation into CD19-negative histiocytic sarcoma. Using droplet-microfluidic technology and growth kinetic analyses, we demonstrate the presence of ibrutinib-resistant subclones and estimate subclone size before treatment initiation. Haploinsufficiency of TRAIL-R, a consequence of del(8p), results in TRAIL insensitivity, which may contribute to ibrutinib resistance. These findings demonstrate that the ibrutinib therapy favours selection and expansion of rare subclones already present before ibrutinib treatment, and provide insight into the heterogeneity of genetic changes associated with ibrutinib resistance.

A Simple Evaluation Tool (ET-CET) Indicates Increase of Diagnostic Skills From Small Bowel Capsule Endoscopy Training Courses: A Prospective Observational European Multicenter Study

Small bowel capsule endoscopy (SBCE) has become a first line diagnostic tool. Several training courses with a similar format have been established in Europe; however, data on learning curve and training in SBCE remain sparse.Between 2008 and 2011, different basic SBCE training courses were organized internationally in UK (n = 2), Italy (n = 2), Germany (n = 2), Finland (n = 1), and nationally in Germany (n = 10), applying similar 8-hour curricula with 50% lectures and 50% hands-on training. The Given PillCam System was used in 12 courses, the Olympus EndoCapsule system in 5, respectively. A simple evaluation tool for capsule endoscopy training (ET-CET) was developed using 10 short SBCE videos including relevant lesions and normal or irrelevant findings. For each video, delegates were required to record a diagnosis (achievable total score from 0 to 10) and the clinical relevance (achievable total score 0 to 10). ET-CET was performed at baseline before the course and repeated, with videos in altered order, after the course.Two hundred ninety-four delegates (79.3% physicians, 16.3% nurses, 4.4% others) were included for baseline analysis, 268 completed the final evaluation. Forty percent had no previous experience in SBCE, 33% had performed 10 or less procedures. Median scores for correct diagnosis improved from 4.0 (IQR 3) to 7.0 (IQR 3) during the courses (P < 0.001, Wilcoxon), and for correct classification of relevance of the lesions from 5.0 (IQR 3) to 7.0 (IQR 3) (P < 0.001), respectively. Improvement was not dependent on experience, profession, SBCE system, or course setting. Previous experience in SBCE was associated with higher baseline scores for correct diagnosis (P < 0.001; Kruskal-Wallis). Additionally, independent nonparametric partial correlation with experience in gastroscopy (rho 0.33) and colonoscopy (rho 0.27) was observed (P < 0.001).A simple ET-CET demonstrated significant improvement of diagnostic skills on completion of formal basic SBCE courses with hands-on training, regardless of preexisting experience, profession, and course setting. Baseline scores for correct diagnoses show a plateau after interpretation of 25 SBCE before courses, supporting this number as a compromise for credentialing. Experience in flexible endoscopy may be useful before attending an SBCE course.

Abstract 4728: Apoptotic priming is regulated by a developmental program and predisposes children to therapy-induced toxicity

Pediatric cancer patients frequently suffer higher levels of treatment-induced toxicities than adults, limiting the use of potentially curative therapies. For example, brain irradiation contributes to the cure of medulloblastomas in 80% of children yet also causes cell death in healthy neurons, resulting in a permanent and devastating loss of IQ. Likewise, children commonly experience dose-limiting cardiotoxicity from doxorubicin treatment. These treatments are comparatively well tolerated in adults yet the basis for this dramatic contrast in sensitivity is unknown. Both radiation and cytotoxic chemotherapies can induce an apoptotic cell death, prompting us to hypothesize that apoptosis may be regulated in a fundamentally different manner in children versus adults.

By testing the functional state of the apoptotic pathway in tissues with BH3 Profiling, we found that healthy brain, heart and kidney tissues from young mice are extremely sensitive to pro-apoptotic signals and are therefore “primed for apoptosis.” In stark contrast, these same tissues are completely insensitive to even saturating amounts of pro-apoptotic signals in adult mice. Apoptosis could be triggered in adult brain, heart or kidney cells only when complemented with exogenous BAX protein suggesting that these tissues lack sufficient levels of BAX or BAK for mitochondrial permeabilization and are thus “incompetent for apoptosis.” Immunoblotting revealed that BAX and BAK protein levels are strongly downregulated in these tissues during postnatal development and become nearly undetectable by adulthood, along with several other components of the apoptotic machinery. Parallel studies with spleen and bone marrow demonstrated high levels of apoptotic priming in young animals which continued into adulthood, highlighting the organ-specific nature of apoptosis regulation. In agreement with these findings, we observed apoptotic cell death in response to radiation damage in the brain, heart and kidneys of early postnatal but not adult mice. Likewise, the extent of doxorubicin-induced damage to cardiac tissue correlated strongly with changes in apoptotic priming and competence. Furthermore, we utilized BAX and/or BAK knockout mice to characterize the pivotal roles of these proteins in regulating apoptotic competence and damage responses in somatic tissues.

We extended these findings to humans by BH3 profiling normal brain tissue and confirmed that brain tissue in young children is primed to undergo apoptosis while in adults it is apoptotically incompetent. Finally, we identified the epigenetic mechanisms that modulate apoptotic pathways during postnatal development. Our findings elucidate the molecular mechanisms responsible for the devastating vital organ sensitivity to damage in children and a strategy for its prevention.

Citation Format: Kristopher A. Sarosiek, Michael Ziller, Cameron Fraser, Patrick Bhola, Jeremy Ryan, Jing Deng, Brian Jian, Marti Goldenberg, Joseph Madsen, Ruben Carrasco, Shenandoah Robinson, Javid Moslehi, Anthony Letai. Apoptotic priming is regulated by a developmental program and predisposes children to therapy-induced toxicity. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4728. doi:10.1158/1538-7445.AM2015-4728

Supporting parents following childhood traumatic brain injury: a qualitative study to examine information and emotional support needs across key care transitions

INTRODUCTION

Traumatic brain injury (TBI) is the leading cause of death and acquired disability in childhood. Research has demonstrated that TBI can lead to long-term physical, cognitive, emotional and behavioural difficulties for children and parental stress. Less is known about how parents experience a childhood brain injury and their information and support needs. This study aimed to examine parents' experiences and support needs following a childhood TBI from the time of the accident to their child's discharge home.

METHODS

Qualitative semi-structured interviews were conducted with 29 parents/carers of children who had experienced a severe TBI. Participants were recruited from one children's tertiary centre in the UK. Data were analysed using the Framework approach.

RESULTS

Parents had unmet information and emotional support needs across the care trajectory from the time of the accident to their child's return home. Information needs related to the impact of the TBI on their child; current and future treatment/rehabilitation plans; helping their child and managing their behaviour; accessing services/support. They lacked information and support for care transitions. In different settings parents faced particular barriers to having their information needs met. Parents' felt they needed emotional support in coming to terms with witnessing the accident and the loss of their former child. Lack of community support related not only to service availability but to a general lack of understanding of the impact of TBI on children, particularly when this was invisible. Overall parents felt unsupported in coping with children's behavioural and psychological difficulties.

DISCUSSION

Taking a holistic approach to examining parents' experiences and support needs has enabled their changing needs to be highlighted across key care transitions within hospital and community settings and the service implications identified. Improvements in care co-ordination across care transitions are needed to ensure continuity of care and integration of support.

Optical coherence tomography for the diagnosis of neovascular age-related macular degeneration: a systematic review

The purpose is to study the diagnostic performance of optical coherence tomography (OCT) and alternative diagnostic tests for neovascular age-related macular degeneration (nAMD). Methods employed are as follows:systematic review and meta-analysis;

INDEX TEST

OCT including time-domain (TD-OCT) and the most recently developed spectral domain (SD-OCT); comparator tests: visual acuity, clinical evaluation (slit lamp), Amsler chart, colour fundus photographs, infra-red reflectance, red-free images/blue reflectance, fundus autofluorescence imaging (FAF), indocyanine green angiography (ICGA), preferential hyperacuity perimetry (PHP), and microperimetry; reference standard: fundus fluorescein angiography. Databases searched included MEDLINE, MEDLINE In Process, EMBASE, Biosis, SCI, the Cochrane Library, DARE, MEDION, and HTA database. Last literature searches: March 2013. Risk of bias assessed using QUADAS-2. Meta-analysis models were fitted using hierarchical summary receiver operating characteristic (HSROC) curves. Twenty-two studies (2 abstracts and 20 articles) enrolling 2124 participants were identified, reporting TD-OCT (12 studies), SD-OCT (1 study), ICGA (8 studies), PHP (3 studies), Amsler grid, colour fundus photography and FAF (1 study each). Most studies were considered to have a high risk of bias in the patient selection (55%, 11/20), and flow and timing (40%, 8/20) domains. In a meta-analysis of TD-OCT studies, sensitivity and specificity (95% CI) were 88% (46-98%) and 78% (64-88%), respectively. There was insufficient information to undertake meta-analysis for other tests. TD-OCT is a sensitive test for detecting nAMD, although specificity was only moderate. Data on SD-OCT are sparse. Diagnosis of nAMD should not rely solely on OCT.