Tumor Mutational Burden from Circulating Tumor DNA Predicts Recurrence of Hepatocellular Carcinoma After Resection: An Emerging Biomarker for Surveillance: An Emerging Biomarker for Surveillance.

OBJECTIVE: Describe the utility of circulating tumor DNA in the post-operative surveillance of hepatocellular carcinoma (HCC). SUMMARY BACKGROUND DATA: Current biomarkers for HCC like Alpha-fetoprotein (AFP) are lacking. ctDNA has shown promise in colorectal and lung cancers, but its utility in HCC remains relatively unknown. METHODS: Patients with HCC undergoing curative-intent resection from 11/1/2020-7/1/2023 received ctDNA testing using the Guardant360 platform. TMB is calculated as the number of somatic mutations-per-megabase of genomic material identified. RESULTS: Forty seven patients had post-operative ctDNA testing. Mean follow-up was 27 months and maximum was 43.2 months. Twelve patients (26%) experienced recurrence. Most (n=41/47, 87.2%) had identifiable ctDNA post-operatively; 55.3%(n=26) were TMB-not detected versus 45.7% (n=21) TMB-detectable. Post-operative identifiable ctDNA was not associated with RFS (P=0.518). Detectable TMB was associated with reduced RFS (6.9 vs. 14.7months, P=0.049). There was a higher rate of recurrence in patients with TMB (n=9/21, 42.9%, vs. n=3/26, 11.5%, P=0.02). Area-Under the Curve (AUC) for TMB-prediction of recurrence was 0.752 versus 0.550 for AFP. ROC-analysis established a TMB cut-off of 4.8mut/mB for predicting post-operative recurrence (P=0.002) and RFS (P=0.025). AFP was not correlated with RFS using the lab-normal cut-off (<11 ng/mL, P=0.682) or the cut-off established by ROC-analysis (>4.6 ng/mL, P=0.494). TMB-high was associated with poorer RFS on cox-regression analysis (HR=5.386, 95%CI1.109-26.160, P=0.037) while micro-vascular invasion (P=0.853) and AFP (P=0.439) were not. CONCLUSIONS: Identifiable TMB on post-operative ctDNA predicts HCC recurrence, and outperformed AFP in this cohort. Perioperative ctDNA may be a useful surveillance tool following curative-intent hepatectomy. Larger-scale studies are needed to confirm this utility and investigate additional applications in HCC patients, including the potential for prophylactic treatment in patients with residual TMB after resection.

Impact of Back-to-Base Normothermic Machine Perfusion on Complications and Costs: A Multi-Center, Real-World Risk-Matched Analysis.

OBJECTIVE: Assess cost and complication outcomes after liver transplantation (LT) using normothermic machine perfusion (NMP). SUMMARY BACKGROUND DATA: End-ischemic NMP is often used to aid logistics, yet its' impact on outcomes after LT remains unclear, as does its' true impact on costs associated with transplantation. METHODS: Deceased donor liver recipients at two centers (1/1/2019-6/30/2023) were included. Retransplants, splits and combined grafts were excluded. End-ischemic NMP (OrganOx-Metra®) was implemented 10/2022 for extended-criteria DBDs, all DCDs and logistics. NMP-cases were matched 1:2 with cold storage controls (SCS) using the Balance-of-Risk (DBD-grafts) and UK-DCD Score (DCD-grafts). RESULTS: Overall, 803 transplantations were included, 174 (21.7%) receiving NMP. Matching was achieved between 118 NMP-DBDs with 236 SCS; and 37 NMP-DCD with 74 corresponding SCS. For both graft types, median inpatient comprehensive complications index (CCI) values were comparable between groups. DCD-NMP grafts experienced reduced cumulative 90-day CCI (27.6 vs. 41.9, P=0.028). NMP also reduced the need for early relaparotomy and renal-replacement-therapy, with subsequently less-frequent major complications (Clavien-Dindo >IVa). This effect was more pronounced in DCD-transplants. NMP had no protective effect on early biliary complications. Organ acquisition/preservation costs were higher with NMP, yet NMP-treated grafts had lower 90-day pre-transplant costs in context of shorter waiting-list times. Overall costs were comparable for both cohorts. CONCLUSIONS: This is the first risk-adjusted outcome and cost analysis comparing NMP and SCS. In addition to logistical benefits, NMP was associated with a reduction in relaparotomy and bleeding in DBD-grafts, and overall complications and post-LT renal-replacement for DCDs. While organ acquisition/preservation was more costly with NMP, overall 90-day-healthcare costs-per-transplantation were comparable.

Prospective study of e-cigarette use and respiratory symptoms in adolescents and young adults.

RATIONALE: Electronic cigarette (e-cigarette) aerosol contains volatile aldehydes, including flavourings and oxidant metals with known pulmonary toxicity. OBJECTIVES: To evaluate the associations of e-cigarette use with symptoms of wheeze, bronchitic symptoms and shortness of breath (SOB) across 4 years of prospective data. METHODS: Participants completed questionnaires on respiratory symptoms and past 30-day e-cigarette, cigarette and cannabis use in 2014 (wave 1; N=2094; mean age 17.3 years, SD=0.6 years). Follow-up information was collected in 2015 (wave 2; n=1609), 2017 (wave 3; n=1502) and 2018 (wave 4; n=1637) using online surveys. Mixed-effects logistic regression models evaluated associations of e-cigarette use with respiratory symptoms. MEASUREMENTS AND MAIN RESULTS: Participants were mostly Hispanic white (51.8%) and evenly representative by sex (49.6% female; 50.4% male). Compared with never e-cigarette users, past 30-day e-cigarette users reported increased odds of wheeze (OR 1.81; 95% CI 1.28, 2.56), bronchitic symptoms (OR 2.06; 95% CI 1.58, 2.69) and SOB (OR 1.78; 95% CI 1.23, 2.57), adjusting for study wave, age, sex, race, lifetime asthma diagnosis and parental education. Effect estimates were attenuated (wheeze (OR 1.41; 95% CI 0.99, 2.01), bronchitic symptoms (OR 1.55; 95% CI 1.18, 2.05), SOB (OR 1.48; 95% CI 1.01, 2.18)), after adjusting additionally for current cigarette use, cannabis use and secondhand exposure to e-cigarettes/cigarettes/cannabis. CONCLUSIONS: E-cigarette use in young adults was associated with respiratory symptoms, independent of combustible cannabis and cigarette exposures.

The Impact of Normothermic Machine Perfusion and Acuity Circles on Waitlist Time, Mortality and Cost in Liver Transplantation: A Multi-Center Experience.

BACKGROUND: Ex-situ normothermic machine perfusion (NMP) helps increase the use of extended criteria donor livers. However, the impact of an NMP program on waitlist times and mortality has not been evaluated. METHODS: Adult patients listed for liver transplant (LT) at two academic centers 1/1/2015-9/1/2023 were included (n=2773) to allow all patients >6-months follow-up from listing. Routine NMP was implemented on 10/14/2022. Waitlist outcomes were compared from pre-NMP pre-acuity-circles (n=1,460), pre-NMP with acuity circles (n=842) and with NMP (n=381). RESULTS: Median waitlist time was 79days (IQR 20-232 d) at baseline, 49days (7-182) with acuity circles, and 14days (5-56) with NMP (p<0.001). The rate of transplant-per-100-person-years improved from 61-per-100-person-years to 99-per-100-person-years with acuity circles, and 194-per-100-person-years with NMP (p<0.001). Crude mortality without transplant decreased from 18.3% (n=268/1460), to 13.3% (n=112/843), to 6.3% (n=24/381) p<0.001) with NMP. Incidence of mortality without LT was 15-per-100-person-years before acuity circles, 19-per-100 with acuity circles, and 9-per-100-person-years after NMP (p<0.001). Median MELD at LT was lowest with NMP, but MELD at listing was highest in this era (p<0.0001). Median DRI of transplanted livers at baseline was 1.54 (1.27-1.82), 1.66 (1.42-2.16) with acuity circles, and 2.06 (1.63-2.46) with NMP (p<0.001). Six-month post-LT survival was not different between eras (p=0.322). The total cost of healthcare while waitlisted was lowest in the NMP era ($53,683 vs. $32,687 vs. $23,688, p<0.001); cost-per-day did not differ between eras (p=0.152). CONCLUSION: Implementation of a routine NMP program was associated with reduced waitlist time and mortality without compromising short-term survival after liver transplant despite increased use of riskier grafts. Routine NMP use enables better waitlist management with reduced healthcare costs.

Impact of autotransfusion on recurrence of colorectal cancer liver metastasis: Long-term follow-up of patients undergoing curative intent hepatectomy.

INTRODUCTION: Colorectal cancer liver metastasis (CRLM) occurs in upto 50% of cases and drives patient outcomes. Up-front liver resection is the treatment of choice in resectable cases. There is no consensus yet established as to the safety of intraoperative autotransfusion in liver resection for CRLM. METHODS: Patients undergoing curative-intent hepatectomy for CRLM at a single quaternary-care institution from 1999 to 2016 were included. Demographics, surgical variables, Fong Clinical Risk Score (FCRS), use of intraoperative auto and/or allotransfusion, and survival data were analyzed. Propensity score matching (PSM) was performed accounting for allotransfusion, extent of hepatectomy, FCRS, and systemic treatment regimens. RESULTS: Three-hundred sixteen patients were included. The median follow-up was 10.4 years (7.8-14.1 years). The median recurrence-free survival (RFS) and overall survival (OS) in all patients were 1.6 years (interquartile range: 0.63-6.6 years) and 4.4 years (2.1-8.7), respectively.  Before PSM, there was a significantly reduced RFS in the autotransfusion group (0.96 vs. 1.73 years, p = 0.20). There was no difference in OS (4.11 vs. 4.44 years, p = 0.118). Patients in groups of FCRS 0-2 and 3-5 both had reduced RFS when autotransfusion was used (p = 0.005). This reduction in RFS was further found when comparing autotransfusion versus no autotransfusion within the FCRS 0-2 group and within the FCRS 3-5 group (p = 0.027). On Cox-regression analysis, autotransfusion (hazard ratio = 1.423, 1.028-2.182, p = 0.015) remained predictive of RFS. After PSM, there were no differences in FCRS (p = 0.601), preoperative hemoglobin (p = 0.880), allotransfusion (p = 0.130), adjuvant chemotherapy (p = 1.000), immunotherapy (p = 0.172), tumor grade (p = 1.000), use of platinum-based chemotherapy (p = 0.548), or type of hepatic resection (p = 0.967). After matching, there was a higher rate of recurrence with autotransfusion (69.0% vs. 47.6%, p = 0.046). There was also a reduced time to recurrence in the autotransfusion group compared with the group without (p = 0.006). There was no difference in OS after PSM (p = 0.262). CONCLUSION: Autotransfusion may adversely affect recurrence in liver resection for CRLM. Until further studies clarify this risk profile, the use of intraoperative autotransfusion should be critically assessed on a case-by-case basis only when other resuscitation options are not available.

Carrier Protein-Free Enzymatic Biaryl Coupling in Arylomycin A2 Assembly and Structure of the Cytochrome P450 AryC.

Invited for the cover of this issue are Sabine Schneider, Tobias A. M. Gulder and co-workers at Technical University of Dresden, Technical University of Munich and Ludwig-Maximillians-University Munich. The image depicts the crystal structure of the cytochrome P450 AryC from arylomycin biosynthesis. Read the full text of the article at 10.1002/chem.202103389.

Carrier Protein-Free Enzymatic Biaryl Coupling in Arylomycin A2 Assembly and Structure of the Cytochrome P450 AryC.

The arylomycin antibiotics are potent inhibitors of bacterial type I signal peptidase. These lipohexapeptides contain a biaryl structural motif reminiscent of glycopeptide antibiotics. We herein describe the functional and structural evaluation of AryC, the cytochrome P450 performing biaryl coupling in biosynthetic arylomycin assembly. Unlike its enzymatic counterparts in glycopeptide biosynthesis, AryC converts free substrates without the requirement of any protein interaction partner, likely enabled by a strongly hydrophobic cavity at the surface of AryC pointing to the substrate tunnel. This activity enables chemo-enzymatic assembly of arylomycin A2 that combines the advantages of liquid- and solid-phase peptide synthesis with late-stage enzymatic cross-coupling. The reactivity of AryC is unprecedented in cytochrome P450-mediated biaryl construction in non-ribosomal peptides, in which peptidyl carrier protein (PCP)-tethering so far was shown crucial both in vivo and in vitro.

Enhanced oxidative phosphorylation in NKT cells is essential for their survival and function.

Cellular metabolism and signaling pathways are key regulators to determine conventional T cell fate and function, but little is understood about the role of cell metabolism for natural killer T (NKT) cell survival, proliferation, and function. We found that NKT cells operate distinct metabolic programming from CD4 T cells. NKT cells are less efficient in glucose uptake than CD4 T cells with or without activation. Gene-expression data revealed that, in NKT cells, glucose is preferentially metabolized by the pentose phosphate pathway and mitochondria, as opposed to being converted into lactate. In fact, glucose is essential for the effector functions of NKT cells and a high lactate environment is detrimental for NKT cell survival and proliferation. Increased glucose uptake and IFN-γ expression in NKT cells is inversely correlated with bacterial loads in response to bacterial infection, further supporting the significance of glucose metabolism for NKT cell function. We also found that promyelocytic leukemia zinc finger seemed to play a role in regulating NKT cells' glucose metabolism. Overall, our study reveals that NKT cells use distinct arms of glucose metabolism for their survival and function.

Evaluation of Obstructive Sleep Apnea in Prone Versus Nonprone Body Positioning With Polysomnography in Infants With Robin Sequence.

OBJECTIVE: Management of obstructive sleep apnea in infants with Robin sequence (RS) includes prone positioning during sleep, which conflicts with safe infant sleep data. We examined changes in polysomnography (PSG) parameters for prone versus nonprone body positions in these infants. DESIGN: Pre-post interventional, nonblinded study. PARTICIPANTS: Infants with RS referred for PSG were recruited from craniofacial clinic and inpatient units at Children's Hospital Los Angeles, a tertiary pediatric center. Fourteen infants were recruited, and 12 studies were completed on both body positions; 11 studies were used in the analysis. INTERVENTIONS: The PSG was divided into nonprone and prone sleep, moving from their usual sleep position to the other position midway in the study. MAIN OUTCOME MEASURES: Data was collected in each position for obstructive apnea-hypopnea index (oAHI), central apnea index (CAI), sleep efficiency (SE), and arousal index (AI). Signed rank test was used to evaluate the change in body position. RESULTS: All infants were term except 1, age 7 to 218 days (mean: 55 days; standard deviation: 58 days), and 8 (57%) of 14 were female. From nonprone to prone sleep position, the median oAHI (16.0-14.0), CAI (2.9-1.0), and AI (28.0-19.9) decreased (P = .065); SE increased (67.4-85.2; P = .227). CONCLUSIONS: Prone positioning may benefit some infants with RS. However, even those with significant improvement in obstructive sleep apnea did not completely resolve their obstruction. The decision to use prone positioning as a therapy should be objectively evaluated in individual infants.

Electronic Cigarette Use and Respiratory Symptoms in Adolescents.

RATIONALE: Rates of adolescent electronic (e-) cigarette use are increasing, but there has been little study of the chronic effects of use. Components of e-cigarette aerosol have known pulmonary toxicity. OBJECTIVES: To investigate the associations of e-cigarette use with chronic bronchitis symptoms and wheeze in an adolescent population. METHODS: Associations of self-reported use of e-cigarettes with chronic bronchitic symptoms (chronic cough, phlegm, or bronchitis) and of wheeze in the previous 12 months were examined in 2,086 Southern California Children's Health Study participants completing questionnaires in 11th and 12th grade in 2014. MEASUREMENTS AND MAIN RESULTS: Ever e-cigarette use was reported by 502 (24.0%), of whom 201 (9.6%) used e-cigarettes during the last 30 days (current users). Risk of bronchitic symptoms was increased by almost twofold among past users (odds ratio [OR], 1.85; 95% confidence interval [CI], 1.37-2.49), compared with never-users, and by 2.02-fold (95% CI, 1.42-2.88) among current users. Risk increased with frequency of current use (OR, 1.66; 95% CI, 1.02-2.68) for 1-2 days and 2.52 (95% CI, 1.56-4.08) for 3 or more days in past 30 days compared with never-users. Associations were attenuated by adjustment for lifetime number of cigarettes smoked and secondhand smoke exposure. However, risk of bronchitic symptoms among past e-cigarette users remained elevated after adjustment for relevant potential confounders and was also observed among never-cigarette users (OR, 1.70; 95% CI, 1.11-2.59). There were no statistically significant associations of e-cigarette use with wheeze after adjustment for cigarette use. CONCLUSIONS: Adolescent e-cigarette users had increased rates of chronic bronchitic symptoms. Further investigation is needed to determine the long-term effects of e-cigarettes on respiratory health.

Comparison of fungal vs bacterial infections in the medical intensive liver unit: Cause or corollary for high mortality?

BACKGROUND: Due to development of an immune-dysregulated phenotype, advanced liver disease in all forms predisposes patients to sepsis acquisition, including by opportunistic pathogens such as fungi. Little data exists on fungal infection within a medical intensive liver unit (MILU), particularly in relation to acute on chronic liver failure. AIM: To investigate the impact of fungal infections among critically ill patients with advanced liver disease, and compare outcomes to those of patients with bacterial infections. METHODS: From our prospective registry of MILU patients from 2018-2022, we included 27 patients with culture-positive fungal infections and 183 with bacterial infections. We compared outcomes between patients admitted to the MILU with fungal infections to bacterial counterparts. Data was extracted through chart review. RESULTS: All fungal infections were due to Candida species, and were most frequently blood isolates. Mortality among patients with fungal infections was significantly worse relative to the bacterial cohort (93% vs 52%, P < 0.001). The majority of the fungal cohort developed grade 2 or 3 acute on chronic liver failure (ACLF) (90% vs 64%, P = 0.02). Patients in the fungal cohort had increased use of vasopressors (96% vs 70%, P = 0.04), mechanical ventilation (96% vs 65%, P < 0.001), and dialysis due to acute kidney injury (78% vs 52%, P = 0.014). On MILU admission, the fungal cohort had significantly higher Acute Physiology and Chronic Health Evaluation (108 vs 91, P = 0.003), Acute Physiology Score (86 vs 65, P = 0.003), and Model for End-Stage Liver Disease-Sodium scores (86 vs 65, P = 0.041). There was no significant difference in the rate of central line use preceding culture (52% vs 40%, P = 0.2). Patients with fungal infection had higher rate of transplant hold placement, and lower rates of transplant; however, differences did not achieve statistical significance. CONCLUSION: Mortality was worse among patients with fungal infections, likely attributable to severe ACLF development. Prospective studies examining empiric antifungals in severe ACLF and associations between fungal infections and transplant outcomes are critical.

Emerging and Clinically Accepted Biomarkers for Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death and the sixth most diagnosed malignancy worldwide. Serum alpha-fetoprotein (AFP) is the traditional, ubiquitous biomarker for HCC. However, there has been an increasing call for the use of multiple biomarkers to optimize care for these patients. AFP, AFP-L3, and prothrombin induced by vitamin K absence II (DCP) have described clinical utility for HCC, but unfortunately, they also have well established and significant limitations. Circulating tumor DNA (ctDNA), genomic glycosylation, and even totally non-invasive salivary metabolomics and/or micro-RNAS demonstrate great promise for early detection and long-term surveillance, but still require large-scale prospective validation to definitively validate their clinical validity. This review aims to provide an update on clinically available and emerging biomarkers for HCC, focusing on their respective clinical strengths and weaknesses.

Small extracellular vesicles promote stiffness-mediated metastasis.

Tissue stiffness is a critical prognostic factor in breast cancer and is associated with metastatic progression. Here we show an alternative and complementary hypothesis of tumor progression whereby physiological matrix stiffness affects the quantity and protein cargo of small EVs produced by cancer cells, which in turn drive their metastasis. Primary patient breast tissue produces significantly more EVs from stiff tumor tissue than soft tumor adjacent tissue. EVs released by cancer cells on matrices that model human breast tumors (25 kPa; stiff EVs) feature increased adhesion molecule presentation (ITGα 2 ß 1 , ITGα 6 ß 4 , ITGα 6 ß 1 , CD44) compared to EVs from softer normal tissue (0.5 kPa; soft EVs), which facilitates their binding to extracellular matrix (ECM) protein collagen IV, and a 3-fold increase in homing ability to distant organs in mice. In a zebrafish xenograft model, stiff EVs aid cancer cell dissemination through enhanced chemotaxis. Moreover, normal, resident lung fibroblasts treated with stiff and soft EVs change their gene expression profiles to adopt a cancer associated fibroblast (CAF) phenotype. These findings show that EV quantity, cargo, and function depend heavily on the mechanical properties of the extracellular microenvironment.

Circulating Tumor DNA Profiling in Liver Transplant for Hepatocellular Carcinoma, Cholangiocarcinoma, and Colorectal Liver Metastases: A Programmatic Proof of Concept.

INTRODUCTION: Circulating tumor DNA (ctDNA) is emerging as a promising, non-invasive diagnostic and surveillance biomarker in solid organ malignancy. However, its utility before and after liver transplant (LT) for patients with primary and secondary liver cancers is still underexplored. METHODS: Patients undergoing LT for hepatocellular carcinoma (HCC), cholangiocarcinoma (CCA), and colorectal liver metastases (CRLM) with ctDNA testing were included. CtDNA testing was conducted pre-transplant, post-transplant, or both (sequential) from 11/2019 to 09/2023 using Guardant360, Guardant Reveal, and Guardant360 CDx. RESULTS: 21 patients with HCC (n = 9, 43%), CRLM (n = 8, 38%), CCA (n = 3, 14%), and mixed HCC/CCA (n = 1, 5%) were included in the study. The median follow-up time was 15 months (range: 1-124). The median time from pre-operative testing to surgery was 3 months (IQR: 1-4; range: 0-5), and from surgery to post-operative testing, it was 9 months (IQR: 2-22; range: 0.4-112). A total of 13 (62%) patients had pre-transplant testing, with 8 (62%) having ctDNA detected (ctDNA+) and 5 (32%) not having ctDNA detected (ctDNA-). A total of 18 (86%) patients had post-transplant testing, 11 (61%) of whom were ctDNA+ and 7 (33%) of whom were ctDNA-. The absolute recurrence rates were 50% (n = 5) in those who were ctDNA+ vs. 25% (n = 1) in those who were ctDNA- in the post-transplant setting, though this difference was not statistically significant (p = 0.367). Six (29%) patients (HCC = 3, CCA = 1, CRLM = 2) experienced recurrence with a median recurrence-free survival of 14 (IQR: 6-40) months. Four of these patients had positive post-transplant ctDNA collected following diagnosis of recurrence, while one patient had positive post-transplant ctDNA collected preceding recurrence. A total of 10 (48%) patients had sequential ctDNA testing, of whom n = 5 (50%) achieved ctDNA clearance (+/-). The remainder were ctDNA+/+ (n = 3, 30%), ctDNA-/- (n = 1, 10%), and ctDNA-/+ (n = 1, 11%). Three (30%) patients showed the acquisition of new genomic alterations following transplant, all without recurrence. Overall, the median tumor mutation burden (TMB) decreased from 1.23 mut/Mb pre-transplant to 0.00 mut/Mb post-transplant. CONCLUSIONS: Patients with ctDNA positivity experienced recurrence at a higher rate than the ctDNA- patients, indicating the potential role of ctDNA in predicting recurrence after curative-intent transplant. Based on sequential testing, LT has the potential to clear ctDNA, demonstrating the capability of LT in the treatment of systemic disease. Transplant providers should be aware of the potential of donor-derived cell-free DNA and improved approaches are necessary to address such concerns.

ER-associated degradation adapter Sel1L is required for CD8+ T cell function and memory formation following acute viral infection.

The maintenance of antigen-specific CD8+ T cells underlies the efficacy of vaccines and immunotherapies. Pathways contributing to CD8+ T cell loss are not completely understood. Uncovering the pathways underlying the limited persistence of CD8+ T cells would be of significant benefit for developing novel strategies of promoting T cell persistence. Here, we demonstrate that murine CD8+ T cells experience endoplasmic reticulum (ER) stress following activation and that the ER-associated degradation (ERAD) adapter Sel1L is induced in activated CD8+ T cells. Sel1L loss limits CD8+ T cell function and memory formation following acute viral infection. Mechanistically, Sel1L is required for optimal bioenergetics and c-Myc expression. Finally, we demonstrate that human CD8+ T cells experience ER stress upon activation and that ER stress is negatively associated with improved T cell functionality in T cell-redirecting therapies. Together, these results demonstrate that ER stress and ERAD are important regulators of T cell function and persistence.

Epigenetic Reprogramming of Autophagy Drives Mutant IDH1 Glioma Progression and Response to Radiation.

Mutant isocitrate dehydrogenase 1 (mIDH1; IDH1 R132H ) exhibits a gain of function mutation enabling 2-hydroxyglutarate (2HG) production. 2HG inhibits DNA and histone demethylases, inducing epigenetic reprogramming and corresponding changes to the transcriptome. We previously demonstrated 2HG-mediated epigenetic reprogramming enhances DNA-damage response and confers radioresistance in mIDH1 gliomas harboring p53 and ATRX loss of function mutations. In this study, RNA-seq and ChIP-seq data revealed human and mouse mIDH1 glioma neurospheres have downregulated gene ontologies related to mitochondrial metabolism and upregulated autophagy. Further analysis revealed that the decreased mitochondrial metabolism was paralleled by a decrease in glycolysis, rendering autophagy as a source of energy in mIDH1 glioma cells. Analysis of autophagy pathways showed that mIDH1 glioma cells exhibited increased expression of pULK1-S555 and enhanced LC3 I/II conversion, indicating augmented autophagy activity. This dependence is reflected by increased sensitivity of mIDH1 glioma cells to autophagy inhibition. Blocking autophagy selectively impairs the growth of cultured mIDH1 glioma cells but not wild-type IDH1 (wtIDH1) glioma cells. Targeting autophagy by systemic administration of synthetic protein nanoparticles packaged with siRNA targeting Atg7 (SPNP-siRNA-Atg7) sensitized mIDH1 glioma cells to radiation-induced cell death, resulting in tumor regression, long-term survival, and immunological memory, when used in combination with IR. Our results indicate autophagy as a critical pathway for survival and maintenance of mIDH1 glioma cells, a strategy that has significant potential for future clinical translation. One Sentence Summary: The inhibition of autophagy sensitizes mIDH1 glioma cells to radiation, thus creating a promising therapeutic strategy for mIDH1 glioma patients. Graphical abstract: Our genetically engineered mIDH1 mouse glioma model harbors IDH1 R132H in the context of ATRX and TP53 knockdown. The production of 2-HG elicited an epigenetic reprogramming associated with a disruption in mitochondrial activity and an enhancement of autophagy in mIDH1 glioma cells. Autophagy is a mechanism involved in cell homeostasis related with cell survival under energetic stress and DNA damage protection. Autophagy has been associated with radio resistance. The inhibition of autophagy thus radio sensitizes mIDH1 glioma cells and enhances survival of mIDH1 glioma-bearing mice, representing a novel therapeutic target for this glioma subtype with potential applicability in combined clinical strategies.