Mosche Pompsch

Endoplasmic reticulum (ER) stress leads to activation of the unfolded protein response (UPR) that results in transient suppression of protein translation to allow recovery but leads to cell death when stress cannot be resolved. Central to initiation of the UPR is the activation of the ER transmembrane kinase protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK). Here we report that the thiol oxidoreductase ERp57 and protein disulfide isomerase-A1 (PDI), which belong to the same family of luminal ER oxidoreductases, have strikingly opposing roles in the regulation of PERK function. In HCT116 colon carcinoma cells, lentiviral depletion of ERp57 resulted in oxidation of PDI and activation of PERK, whereas depletion or chemical inhibition of PDI reduced PERK signaling and sensitized the cancer cells to hypoxia and ER stress. We conclude that oxidized PDI acts as a PERK activator, whereas ERp57 keeps PDI in a reduced state in the absence of ER stress. Thus, our study defines a new interface between metabolic redox signaling and PERK-dependent activation of the UPR and has the potential to influence future cancer therapies that target PERK signaling.

Autophagy is commonly described as a cell survival mechanism and has been implicated in chemo- and radioresistance of cancer cells. Whether ionizing radiation induced autophagy triggers tumor cell survival or cell death still remains unclear. In this study the autophagy related proteins Beclin1 and ATG7 were tested as potential targets to sensitize colorectal carcinoma cells to ionizing radiation under normoxic, hypoxic and starvation conditions. Colony formation, apoptosis and cell cycle analysis revealed that knockdown of Beclin1 or ATG7 does not enhance radiosensitivity in HCT-116 cells. Furthermore, ATG7 knockdown led to an increased survival fraction under oxygen and glutamine starvation, indicating that ionizing radiation indeed induces autophagy which, however, leads to cell death finally. These results highlight that inhibition of autophagic pathways does not generally increase therapy success but may also lead to an unfavorable outcome especially under amino acid and oxygen restriction.

BACKGROUND: Recurrent attacks in neuromyelitis optica spectrum disorders (NMOSDs) or myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) can lead to severe disability. We aimed to analyse the real-world use of immunotherapies in patients with NMOSD and MOGAD, focusing on changes in treatment strategies, effects on attack rates (ARR) and risk factors for attacks. METHODS: This longitudinal registry-based cohort study included 493 patients (320 with aquaporin-4 immunoglobulin G (AQP4-IgG) seropositive NMOSD (65%), 44 with AQP4-IgG seronegative NMOSD (9%) and 129 MOGAD (26%)) with 1247 treatments from 19 German and one Austrian centre from the registry of the neuromyelitis optica study group (NEMOS). We analysed unadjusted ARR and implemented survival analyses and Cox proportional hazard regression to assess efficiency and risk factors for subsequent attacks over time. RESULTS: Rituximab and azathioprine are the most widely used immunotherapies in NMOSD as well as in MOGAD, with changes in distribution over the last decade. Immunotherapy demonstrated significant therapeutic effects in NMOSD but less pronounced effects in MOGAD. Risk factors for attacks included younger age and prior attacks under the same therapy. Efficacy varied among the different immunotherapies, with azathioprine, rituximab and eculizumab showing significant risk reductions in AQP4-IgG seropositive NMOSD. CONCLUSIONS: This study provides insights into the evolving treatment landscape and effectiveness of immunotherapies in NMOSD and MOGAD. Established off-label therapies continue to play an important role, especially for patients with stable disease, with emerging evidence supporting newly approved therapies. Future studies are needed to refine treatment algorithms and address the ongoing uncertainties in MOGAD management.

BACKGROUND: Incomplete attack remission is the main cause of disability in myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD). Apheresis therapies such as plasma exchange and immunoadsorption are widely used in neuroimmunology. Data on apheresis outcomes in MOGAD attacks remain limited. METHODS: We retrospectively evaluated all apheresis treated attacks occurring in patients with MOGAD between 2008 and 2023 at 18 Neuromyelitis Optica Study Group centres. Treatment response was categorised as complete, partial or no remission. Preattack and follow-up Expanded Disability Status Scale (EDSS) and visual Functional System Scores (FSS) were used to calculate absolute outcomes (ΔEDSS/Δvisual FSS). Predictors of complete remission were analysed using a generalised linear mixed model. RESULTS: Apheresis was used for 117/571 (20.5%) attacks in 85/209 (40.7%) patients. Attacks with simultaneous optic neuritis and myelitis were treated more often with apheresis (42.4%, n=14) than isolated myelitis (25.2%, n=35), cerebral manifestation (21.0%, n=17) or isolated optic neuritis (17.6%, n=51). Apheresis was initiated as first-line therapy in 12% (4.5 (IQR 0-11) days after attack onset), second-line therapy in 62% (15 (IQR 6.75-31) days) and third-line therapy in 26% (30 (IQR 19-42) days). Complete remission was achieved in 21%, partial remission in 70% and no remission in 9% of patients. First-line apheresis (OR 2.5, p=0.040) and concomitant disease-modifying therapy (OR 1.5, p=0.011) were associated with complete remission. Both parameters were also associated with a favourable ΔEDSS. No differences in outcomes were observed between the apheresis types. CONCLUSION: Apheresis is frequently used in MOGAD attacks. An early start as first-line therapy and concomitant disease-modifying therapy predict full attack recovery.

BACKGROUND: The nudix family member enzyme MutT homologue-1 (MTH1) hydrolyses the oxidized nucleotides 8-oxo-dGTP and 2-hydroxy-dATP and thus prevents the incorporation of damaged nucleotides into nuclear and mitochondrial DNA. Therefore MTH1 was proposed to protect cancer cells from oxidative DNA lesions and subsequent cell death. We investigated whether the bona fide MTH1 inhibitor TH588 affects responses of cultured colorectal tumor cells to ionizing radiation (IR) in normoxia and in moderate or severe hypoxia. METHODS: TH588 was tested in cell viability and survival assays (tetrazolium dye (MTT), propidium iodide staining, caspase-3 activity, and colony formation assays (CFA)) in colorectal carcinoma cells (HCT116 and SW480) in combination with IR in normoxia and in hypoxia. Additionally, MTH1 was targeted by lentiviral shRNA expression. Human umbilical vein endothelial cells (HUVEC) were assessed in MTT assays. RESULTS: In all cell lines tested, TH588 dose-dependently impaired cell survival. In CFAs, TH588 and IR effects on carcinoma cells were additive in normoxia and in hypoxia. Using 3 different shRNAs, the lentiviral approach was detrimental to SW480, but not to HCT116. CONCLUSIONS: TH588 has cytotoxic effects on transformed and untransformed cells and synergizes with IR in normoxia and in hypoxia. TH588 toxicity is not fully explained by MTH1 inhibition as HCT116 were unaffected by lentiviral suppression of MTH1 expression. TH588 should be explored further because it has radiosensitizing effects in hypoxia.