Biochemical and functional characterization of the p.A165T missense variant of mitochondrial amidoxime-reducing component 1.

Recent genome-wide association studies have identified a missense variant p.A165T in mitochondrial amidoxime-reducing component 1 (mARC1) that is strongly associated with protection from all-cause cirrhosis and improved prognosis in nonalcoholic steatohepatitis (NASH). The precise mechanism of this protective effect is unknown. Substitution of alanine 165 with threonine is predicted to affect mARC1 protein stability and to have deleterious effects on its function. To investigate the mechanism, we have generated a knock-in mutant mARC1 A165T and a catalytically dead mutant C273A (as a control) in human hepatoma HepG2 cells, enabling characterization of protein subcellular distribution, stability, and biochemical functions of the mARC1 mutant protein expressed from its endogenous locus. Compared to wild-type (WT) mARC1, we found that the A165T mutant exhibits significant mislocalization outside of its traditional location anchored in the mitochondrial outer membrane and reduces protein stability, resulting in lower basal levels. We evaluated the involvement of the ubiquitin proteasome system in mARC1 A165T degradation and observed increased ubiquitination and faster degradation of the A165T variant. In addition, we have shown that HepG2 cells carrying the MTARC1 p.A165T variant exhibit lower N-reductive activity on exogenously-added amidoxime substrates in vitro. The data from these biochemical and functional assays suggest a mechanism by which the MTARC1 p.A165T variant abrogates enzyme function which may contribute to its protective effect in liver disease.

Reference intervals for high sensitivity cardiac troponin I and N-terminal pro-B-type natriuretic peptide in children and adolescents on the Siemens Atellica.

OBJECTIVES: The cardiac biomarkers high sensitivity cardiac troponin I (hs-cTnI) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) are utilised in paediatric healthcare for the diagnosis and prognostic assessment of many conditions including myocarditis, congenital heart disease, multisystem inflammatory syndrome in children (MIS-C) and heart failure. However, the standardised age-related reference intervals, 99th percentile cut-offs and clinical guidelines are not available, making the interpretation of these biomarkers challenging. This study aimed to generate normative data in a paediatric cohort for the Siemens Atellica® IM 1300 analyser. METHODS: Residual plasma samples were collected from children aged up to 17 years attending primary care and out-patient settings and with no apparent evidence of cardiac dysfunction, renal dysfunction or other confounders. Reference intervals were generated using the 2.5th-97.5th percentiles, and 99th percentile cut-offs determined according to CLSI EP28-A3c. RESULTS: Statistical analysis revealed that partitioning was not required for gender for either biomarker. The reference interval for hs-cTnI for children aged one month to 16 years (n=292, 146 females and 146 males) was <14 ng/L with a 99th percentile cut-off of 19 ng/L. The reference interval for NT-proBNP for children aged one month up to one year was <714 ng/L (n=14) and for children aged 1-16 years (n=339) was <295 ng/L. CONCLUSIONS: This is the first paediatric reference interval data generated on the Siemens Atellica® solution. These reference intervals and 99th percentiles will inform clinical decisions in the paediatric cardiology setting.

Discovery and SAR Study of Boronic Acid-Based Selective PDE3B Inhibitors from a Novel DNA-Encoded Library.

Human genetic evidence shows that PDE3B is associated with metabolic and dyslipidemia phenotypes. A number of PDE3 family selective inhibitors have been approved by the FDA for various indications; however, given the undesirable proarrhythmic effects in the heart, selectivity for PDE3B inhibition over closely related family members (such as PDE3A; 48% identity) is a critical consideration for development of PDE3B therapeutics. Selectivity for PDE3B over PDE3A may be achieved in a variety of ways, including properties intrinsic to the compound or tissue-selective targeting. The high (>95%) active site homology between PDE3A and B represents a massive obstacle for obtaining selectivity at the active site; however, utilization of libraries with high molecular diversity in high throughput screens may uncover selective chemical matter. Herein, we employed a DNA-encoded library screen to identify PDE3B-selective inhibitors and identified potent and selective boronic acid compounds bound at the active site.

International Newborn Screening Practices for the Early Detection of Congenital Adrenal Hyperplasia.

INTRODUCTION: Newborn screening (NBS) programmes vary internationally in their approach to screening. Guidelines for congenital adrenal hyperplasia (CAH) screening recommend the use of two-tier testing and gestational age cutoffs to minimise false-positive results. The aims of this study were to describe (1) the approaches; (2) protocols used; and (3) available outcomes for CAH screening internationally. METHODS: All members of the International Society for Neonatal Screening were asked to describe their CAH NBS protocols, with an emphasis on the use of second-tier testing, 17-hydroxyprogesterone (17OHP) cutoffs, and gestational age and birth weight adjustments. If available, screening outcomes were requested. RESULTS: Representatives from 23 screening programmes provided data. Most (n = 14; 61%) recommend sampling at 48-72 h of life. Fourteen (61%) use single-tier testing and 9 have a two-tier testing protocol. Gestational age cutoffs are used in 10 programmes, birth weight cutoffs in 3, and a combination of both in 9. One programme does not use either method of adjusting 17OHP cutoffs. Case definition of a positive test and the response to a positive test differed between programmes. CONCLUSIONS: We have demonstrated significant variation across all aspects of NBS for CAH, including timing, the use of single versus two-tier testing and cutoff interpretation. Collaboration between international screening programmes and implementation of new techniques to improve screen efficacy will facilitate ongoing expansion and quality improvement in CAH NBS.

Biochemical testing for inborn errors of metabolism: experience from a large tertiary neonatal centre.

Inborn errors of metabolism are an individually rare but collectively significant cause of mortality and morbidity in the neonatal period. They are identified by either newborn screening programmes or clinician-initiated targeted biochemical screening. This study examines the relative contribution of these two methods to the identification of inborn errors of metabolism and describes the incidence of these conditions in a large, tertiary, neonatal unit. We also examined which factors could impact the reliability of metabolic testing in this cohort. This is a retrospective, single-site study examining infants in whom a targeted metabolic investigation was performed from January 2018 to December 2020 inclusive. Data was also provided by the national newborn screening laboratory regarding newborn screening diagnoses. Two hundred and four newborns received a clinician-initiated metabolic screen during the time period examined with 5 newborns being diagnosed with an inborn error of metabolism (IEM) (2.4%). Of the 25,240 infants born in the hospital during the period examined, a further 11 newborns had an inborn error of metabolism diagnosed on newborn screening. This produced an incidence in our unit over the time described of 6.34 per 10,000 births. This number reflects a minimum estimate, given that the conditions diagnosed refer to early-onset disorders and distinctive categories of IEM only. Efficiency of the clinician-initiated metabolic screening process was also examined. The only statistically significant variable in requiring repeat metabolic screening was early day of life (z-score = - 2.58, p = 0.0098). A total of 28.4% was missing one of three key metabolic investigation parameters of blood glucose, ammonia or lactate concentration with ammonia the most common investigation missing. While hypoglycemia was the most common clinical rationale for a clinician-initiated metabolic test, it was a poor predictor of inborn error of metabolism with no newborns of 25 screened were diagnosed with a metabolic disorder. CONCLUSION: Clinician-targeted metabolic screening had a high diagnostic yield given the relatively low prevalence of inborn errors of metabolism in the general population. Thoughts should be given to the rationale behind each targeted metabolic test and what specific metabolic disease or category of inborn error of metabolism they are concerned along with commencing targeted testing. WHAT IS KNOWN: • Inborn errors of metabolism are a rare but potentially treatable cause of newborn mortality and morbidity. • A previous study conducted in a tertiary unit in an area with limited newborn screening demonstrated a diagnostic yield of 5.4%. WHAT IS NEW: • Clinician-initiated targeted metabolic screening has a good diagnostic performance even with a more expanded newborn screening programme. • Further optimisation could be achieved by examining the best timing and also the rationale of metabolic testing in the newborn period.

The renal-bone axis in older people living with HIV on stable antiretroviral therapy: A sub-analysis of the GS-US-104-0423 study.

BACKGROUND: Data on low bone mineral density (BMD) in people living with HIV (PLWH) are mainly derived from younger adults; little is known about how antiretroviral therapy (ART) and alterations in the renal-bone axis relate to BMD in older PLWH. METHODS: Cross-sectional study of men > 50 years and post-menopausal women with HIV. Antiretroviral therapy exposure was stratified into four groups based on use of tenofovir disoproxil fumarate (TDF) and protease inhibitors (PI): non-TDF/non-PI, non-TDF/PI, TDF/non-PI, and TDF/PI. Bone mineral density was measured by dual X-ray absorptiometry (DXA). Bone turnover/regulatory markers and renal tubular function were analysed in stored plasma and urine samples. The association of ART exposure and bone/renal biomarkers on BMD was explored using logistic regression models. RESULTS: 247 individuals (median [IQR] age 57 [53, 65] years; 47% female; 13% of Black ethnicity; CD4 count 643 [473, 811] cells/mm3; and 98% with HIV RNA < 200 copies/mL) were included. Bone turnover and renal tubular function differed significantly by ART exposure. In analyses adjusted for demographic and traditional renal/bone risk factors, exposure to TDF and PI was associated with a fourfold greater risk of low BMD at the femoral neck and exposure to TDF and/or PI with a threefold greater risk of low BMD at the lumbar spine. The relationship between ART and low BMD was not altered by further adjustment for bone turnover or renal tubular function markers. CONCLUSIONS: The associations between low BMD and ART exposure (TDF vs. non-TDF and boosted vs. unboosted third agents) were minimally affected by adjustments for bone and kidney biomarkers.

LKB1 drives stasis and C/EBP-mediated reprogramming to an alveolar type II fate in lung cancer.

LKB1 is among the most frequently altered tumor suppressors in lung adenocarcinoma. Inactivation of Lkb1 accelerates the growth and progression of oncogenic KRAS-driven lung tumors in mouse models. However, the molecular mechanisms by which LKB1 constrains lung tumorigenesis and whether the cancer state that stems from Lkb1 deficiency can be reverted remains unknown. To identify the processes governed by LKB1 in vivo, we generated an allele which enables Lkb1 inactivation at tumor initiation and subsequent Lkb1 restoration in established tumors. Restoration of Lkb1 in oncogenic KRAS-driven lung tumors suppressed proliferation and led to tumor stasis. Lkb1 restoration activated targets of C/EBP transcription factors and drove neoplastic cells from a progenitor-like state to a less proliferative alveolar type II cell-like state. We show that C/EBP transcription factors govern a subset of genes that are induced by LKB1 and depend upon NKX2-1. We also demonstrate that a defining factor of the alveolar type II lineage, C/EBPα, constrains oncogenic KRAS-driven lung tumor growth in vivo. Thus, this key tumor suppressor regulates lineage-specific transcription factors, thereby constraining lung tumor development through enforced differentiation.

LKB1 inactivation modulates chromatin accessibility to drive metastatic progression.

Metastasis is the leading cause of cancer-related deaths and enables cancer cells to compromise organ function by expanding in secondary sites. Since primary tumours and metastases often share the same constellation of driver mutations, the mechanisms that drive their distinct phenotypes are unclear. Here we show that inactivation of the frequently mutated tumour suppressor gene LKB1 (encoding liver kinase B1) has evolving effects throughout the progression of lung cancer, which leads to the differential epigenetic re-programming of early-stage primary tumours compared with late-stage metastases. By integrating genome-scale CRISPR-Cas9 screening with bulk and single-cell multi-omic analyses, we unexpectedly identify LKB1 as a master regulator of chromatin accessibility in lung adenocarcinoma primary tumours. Using an in vivo model of metastatic progression, we further show that loss of LKB1 activates the early endoderm transcription factor SOX17 in metastases and a metastatic-like sub-population of cancer cells within primary tumours. The expression of SOX17 is necessary and sufficient to drive a second wave of epigenetic changes in LKB1-deficient cells that enhances metastatic ability. Overall, our study demonstrates how the downstream effects of an individual driver mutation can change throughout cancer development, with implications for stage-specific therapeutic resistance mechanisms and the gene regulatory underpinnings of metastatic evolution.

The presentation of congenital adrenal hyperplasia in an unscreened population.

BACKGROUND: The aim of this study was to describe the incidence and spectrum of early clinical presentations of congenital adrenal hyperplasia (CAH) in an unscreened population. METHODS: A national retrospective observational study was undertaken to identify all children diagnosed with CAH in the Republic of Ireland, between January 2005 and December 2019. Reporting clinicians completed anonymized clinical questionnaires. RESULTS: There were 103 cases of CAH reported and 69 cases met the study inclusion criteria. The estimated annualized incidence of CAH in the Republic of Ireland was 1:14,754 or 0.07 cases per 1,000 live births. Forty-seven children presented clinically in the first six months of life, but only 17 of these had a confirmed diagnosis by day 10. Of these early presentations, there were 28 infants with salt-wasting, 15 females presented with virilized genitalia and four infants were detected due to a family history of CAH. Female infants presented at a median age of 0 days [IQR 0-1] and males at 14 days [IQR 9-21]. Seventy-eight percent of salt-wasting presentations occurred after day 10. Delays in clinical presentation, biochemical diagnosis and treatment initiation were identified. CONCLUSIONS: The incidence of CAH is higher in Ireland than in other unscreened populations. In the absence of screening, clinicians should be aware of the possibility of CAH and appropriate investigations should be urgently requested. Life-threatening salt-wasting is the most frequent clinical presentation and many cases could be detected prior to decompensation if newborn screening were introduced.

The contribution of serum cortisone and glucocorticoid metabolites to detrimental bone health in patients receiving hydrocortisone therapy.

BACKGROUND: Glucocorticoid therapy is the most common cause of iatrogenic osteoporosis. Less is known regarding the effect of glucocorticoids when used as replacement therapy on bone remodelling in patients with adrenal insufficiency. Enhanced intracellular conversion of inactive cortisone to active cortisol, by 11 beta-hydroxysteroid dehydrogenase type 1(11ß-HSD1) and other enzymes leading to alterations in glucocorticoid metabolism, may contribute to a deleterious effect on bone health in this patient group. METHODS: Study design: An open crossover prospective study randomizing ten hypopituitary men, with severe ACTH deficiency, to three commonly used hydrocortisone dose regimens. MEASUREMENTS: Following 6 weeks of each regimen, patients underwent 24-h serum cortisol/cortisone sampling, measurement of bone turnover markers, and a 24-h urine collection for measurement of urinary steroid metabolites by gas chromatography-mass spectrometry (GC-MS). Serum cortisone and cortisol were analysed by liquid chromatography-mass spectrometry (LC-MS). RESULTS: Dose-related and circadian variations in serum cortisone were seen to parallel those for cortisol, indicating conversion of ingested hydrocortisone to cortisone. The median area under the curve (AUC) of serum cortisone was significantly higher in patients on dose A (20 mg/10 mg) [670.5 (IQR 621-809.2)] compared to those on dose C (10 mg/5 mg) [562.8 (IQR 520.1-619.6), p = 0.01]. A negative correlation was observed between serum cortisone and bone formation markers, OC [1-49] (r = - 0.42, p = 0.03), and PINP (r = - 0.49, p = 0.01). There was a negative correlation between the AUC of night-time serum cortisone levels with the bone formation marker, OC [1-49] (r = - 0.41, p = 0.03) but there were no significant correlations between day-time serum cortisone or cortisol with bone turnover markers. There was a negative correlation between total urinary cortisol metabolites and the bone formation markers, PINP (r = - 0.39, p = 0.04), and OC [1-49] (r = - 0.35, p = 0.06). CONCLUSION: Serum cortisol and cortisone and total urinary corticosteroid metabolites are negatively associated with bone turnover markers in patients receiving replacement doses of hydrocortisone, with nocturnal glucocorticoid exposure having a potentially greater influence on bone turnover. TRIAL REGISTRATION: Irish Medicines Board Clinical Trial Number - CT900/459/1 and EudraCT Number - 2007-005018-37 . Registration date: 07-09-2007.

An LKB1-SIK Axis Suppresses Lung Tumor Growth and Controls Differentiation.

The kinase LKB1 is a critical tumor suppressor in sporadic and familial human cancers, yet the mechanisms by which it suppresses tumor growth remain poorly understood. To investigate the tumor-suppressive capacity of four canonical families of LKB1 substrates in vivo, we used CRISPR/Cas9-mediated combinatorial genome editing in a mouse model of oncogenic KRAS-driven lung adenocarcinoma. We demonstrate that members of the SIK family are critical for constraining tumor development. Histologic and gene-expression similarities between LKB1- and SIK-deficient tumors suggest that SIKs and LKB1 operate within the same axis. Furthermore, a gene-expression signature reflecting SIK deficiency is enriched in LKB1-mutant human lung adenocarcinomas and is regulated by LKB1 in human cancer cell lines. Together, these findings reveal a key LKB1-SIK tumor-suppressive axis and underscore the need to redirect efforts to elucidate the mechanisms through which LKB1 mediates tumor suppression. SIGNIFICANCE: Uncovering the effectors of frequently altered tumor suppressor genes is critical for understanding the fundamental driving forces of cancer growth. Our identification of the SIK family of kinases as effectors of LKB1-mediated tumor suppression will refocus future mechanistic studies and may lead to new avenues for genotype-specific therapeutic interventions.This article is highlighted in the In This Issue feature, p. 1469.

Intertumoral Heterogeneity in SCLC Is Influenced by the Cell Type of Origin.

The extent to which early events shape tumor evolution is largely uncharacterized, even though a better understanding of these early events may help identify key vulnerabilities in advanced tumors. Here, using genetically defined mouse models of small cell lung cancer (SCLC), we uncovered distinct metastatic programs attributable to the cell type of origin. In one model, tumors gain metastatic ability through amplification of the transcription factor NFIB and a widespread increase in chromatin accessibility, whereas in the other model, tumors become metastatic in the absence of NFIB-driven chromatin alterations. Gene-expression and chromatin accessibility analyses identify distinct mechanisms as well as markers predictive of metastatic progression in both groups. Underlying the difference between the two programs was the cell type of origin of the tumors, with NFIB-independent metastases arising from mature neuroendocrine cells. Our findings underscore the importance of the identity of cell type of origin in influencing tumor evolution and metastatic mechanisms.Significance: We show that SCLC can arise from different cell types of origin, which profoundly influences the eventual genetic and epigenetic changes that enable metastatic progression. Understanding intertumoral heterogeneity in SCLC, and across cancer types, may illuminate mechanisms of tumor progression and uncover how the cell type of origin affects tumor evolution. Cancer Discov; 8(10); 1316-31. ©2018 AACR. See related commentary by Pozo et al., p. 1216 This article is highlighted in the In This Issue feature, p. 1195.

NKX3-1 is required for induced pluripotent stem cell reprogramming and can replace OCT4 in mouse and human iPSC induction.

Reprogramming somatic cells to induced pluripotent stem cells (iPSCs) is now routinely accomplished by overexpression of the four Yamanaka factors (OCT4, SOX2, KLF4, MYC (or OSKM))1. These iPSCs can be derived from patients' somatic cells and differentiated toward diverse fates, serving as a resource for basic and translational research. However, mechanistic insights into regulators and pathways that initiate the pluripotency network remain to be resolved. In particular, naturally occurring molecules that activate endogenous OCT4 and replace exogenous OCT4 in human iPSC reprogramming have yet to be found. Using a heterokaryon reprogramming system we identified NKX3-1 as an early and transiently expressed homeobox transcription factor. Following knockdown of NKX3-1, iPSC reprogramming is abrogated. NKX3-1 functions downstream of the IL-6-STAT3 regulatory network to activate endogenous OCT4. Importantly, NKX3-1 substitutes for exogenous OCT4 to reprogram both mouse and human fibroblasts at comparable efficiencies and generate fully pluripotent stem cells. Our findings establish an essential role for NKX3-1, a prostate-specific tumour suppressor, in iPSC reprogramming.

Mapping the in vivo fitness landscape of lung adenocarcinoma tumor suppression in mice.

The functional impact of most genomic alterations found in cancer, alone or in combination, remains largely unknown. Here we integrate tumor barcoding, CRISPR/Cas9-mediated genome editing and ultra-deep barcode sequencing to interrogate pairwise combinations of tumor suppressor alterations in autochthonous mouse models of human lung adenocarcinoma. We map the tumor suppressive effects of 31 common lung adenocarcinoma genotypes and identify a landscape of context dependence and differential effect strengths.

Effects of vitamin D3 in clinically isolated syndrome and healthy control participants: A double-blind randomised controlled trial.

BACKGROUND: Lowserum vitamin D levels are associated with susceptibility to, and severity of, multiple sclerosis. High dose vitamin D has been proposed as a potential immunomodulator in multiple sclerosis. OBJECTIVES: We performed a single centre, investigator-led, exploratory, double-blind, randomised, placebo controlled, trial of vitamin D3 in clinically isolated syndrome and healthy control participants to assess its immunological effects. Secondary end-points included clinical and magnetic resonance imaging outcomes and safety. METHODS: Clinically isolated syndrome patients and healthy control participants were randomised to: placebo, 5000 IU or 10,000 IU vitamin D3/day (Vigantol oil). Study duration was 24 weeks. RESULTS: The trial did not meet its primary end point, with no difference in the frequency of pro-inflammatory CD4+ T cells (interleukin (IL)-17+/interferon (IFN)-γ+) seen. A higher level of disease freedom (67% versus 50%) was seen in those with serum 1,25 (OH) vitamin D levels>100 nmol/l but this did not reach significance. High dose vitamin D3 was well tolerated with no safety signal. CONCLUSIONS: High dose vitamin D3 over 24 weeks was well tolerated but without immunological, magnetic resonance imaging or clinical evidence of benefit. The hypothesised therapeutic effects in clinically isolated syndrome or multiple sclerosis patients may require longer periods of administration or may only be seen in patients treated with vitamin D3 as an adjunct to established disease modifying therapies.

Molecular definition of a metastatic lung cancer state reveals a targetable CD109-Janus kinase-Stat axis.

Lung cancer is the leading cause of cancer deaths worldwide, with the majority of mortality resulting from metastatic spread. However, the molecular mechanism by which cancer cells acquire the ability to disseminate from primary tumors, seed distant organs, and grow into tissue-destructive metastases remains incompletely understood. We combined tumor barcoding in a mouse model of human lung adenocarcinoma with unbiased genomic approaches to identify a transcriptional program that confers metastatic ability and predicts patient survival. Small-scale in vivo screening identified several genes, including Cd109, that encode novel pro-metastatic factors. We uncovered signaling mediated by Janus kinases (Jaks) and the transcription factor Stat3 as a critical, pharmacologically targetable effector of CD109-driven lung cancer metastasis. In summary, by coupling the systematic genomic analysis of purified cancer cells in distinct malignant states from mouse models with extensive human validation, we uncovered several key regulators of metastatic ability, including an actionable pro-metastatic CD109-Jak-Stat3 axis.

Predictors of longitudinal change in bone mineral density in a cohort of HIV-positive and negative patients.

OBJECTIVE: Although low bone mineral density (BMD) is prevalent in HIV, changes in BMD over time remain unclear. We aimed to compare rates of, and factors associated with, BMD change between HIV-positive and HIV-negative patients. METHODS: In a prospective, 3-year cohort, HIV-positive and HIV-negative patients provided annual demographic and clinical data, fasting bloods, and dual x-ray absorptiometry. Using longitudinal mixed models we compared and determined predictors of rate of change in BMD. RESULTS: Of 384 study participants (45.8% HIV positive), 120 contributed two and 264 contributed three BMD measurements. Those with HIV were younger [median interquartile range 39 (34-46) vs. 43 (35-50) years; P = 0.04], more often men (61 vs. 46%; P = 0.003), and less likely Caucasian (61 vs. 82%; P < 0.001). Although BMD was lower in those with HIV, BMD declined in both groups, with nonsignificant between-group difference in rate of BMD change over time. Within the HIV group, starting antiretroviral therapy (ART) within 3 months of enrolment was associated with greater BMD decline at all anatomical sites (all P < 0.001). Age more than 30 years, Caucasian ethnicity, and not being on ART during follow-up were associated with greater decline and higher parathyroid hormone associated with a smaller decline in BMD at the femoral neck. We found no association between BMD change and exposure to tenofovir disoproxil fumarate or protease inhibitors. CONCLUSION: We observed no difference in rate of BMD decline regardless of HIV status and in HIV-positive patient, having started ART within the previous 3 months was the only factor associated with greater BMD decline at all three sites.

Nfib Promotes Metastasis through a Widespread Increase in Chromatin Accessibility.

Metastases are the main cause of cancer deaths, but the mechanisms underlying metastatic progression remain poorly understood. We isolated pure populations of cancer cells from primary tumors and metastases from a genetically engineered mouse model of human small cell lung cancer (SCLC) to investigate the mechanisms that drive the metastatic spread of this lethal cancer. Genome-wide characterization of chromatin accessibility revealed the opening of large numbers of distal regulatory elements across the genome during metastatic progression. These changes correlate with copy number amplification of the Nfib locus, and differentially accessible sites were highly enriched for Nfib transcription factor binding sites. Nfib is necessary and sufficient to increase chromatin accessibility at a large subset of the intergenic regions. Nfib promotes pro-metastatic neuronal gene expression programs and drives the metastatic ability of SCLC cells. The identification of widespread chromatin changes during SCLC progression reveals an unexpected global reprogramming during metastatic progression.