Lars Winkler

Background/Objectives: Cutaneous T-cell lymphomas (CTCL), most commonly mycosis fungoides and Sézary syndrome, are rare non-Hodgkin lymphomas. Advanced disease responds poorly to current treatments, highlighting the need for new molecularly targeted therapies. WEE1 is a central regulator of the G2/M checkpoint and S-phase progression and has emerged as a therapeutic target in several malignancies, yet it has not been systematically explored in CTCL. Methods: We screened a library of more than 2200 kinase inhibitors in CTCL cell lines and selected adavosertib for further study. Its effects were tested in four CTCL lines; primary keratinocytes and fibroblasts; patient-derived malignant CD4⁺ T cells and healthy donor CD4⁺ T cells; and a MyLa xenograft model, using viability, apoptosis, cell-cycle, Western blot, and phospho-protein array assays. Results: Adavosertib reduced viability at submicromolar IC₅₀ values (0.26–0.56 µM) across all four CTCL lines while largely sparing primary skin cells and was more active in malignant than in healthy donor CD4⁺ T cells. It induced apoptosis and cell-line-specific S-phase and/or G2/M accumulation, lowered WEE1 and phospho-CDK1 (Tyr15), and increased phospho-H2A.X. A phospho-protein array showed activation of checkpoint and stress signalling. In a preliminary xenograft experiment, adavosertib slowed MyLa tumour growth. Conclusions: These preclinical data identify WEE1 as a therapeutic target in CTCL and support further preclinical and early-phase clinical evaluation of adavosertib in this disease.

Background/Objectives: Cutaneous T-cell lymphomas (CTCL), most commonly mycosis fungoides and Sézary syndrome, are rare non-Hodgkin lymphomas. Advanced disease responds poorly to current treatments, highlighting the need for new molecularly tar-geted therapies. WEE1 is a central regulator of the G2/M checkpoint and S-phase progression and has emerged as a therapeutic target in several malignancies, yet it has not been systematically explored in CTCL. Methods: We screened a library of more than 2,200 kinase inhibitors in CTCL cell lines and selected adavosertib for further study. Its effects were tested in four CTCL lines, in primary keratinocytes and fibroblasts, in patient-derived malignant CD4⁺ T cells and healthy donor CD4⁺ T cells, and in a MyLa xenograft model, using viability, apoptosis, cell-cycle, western blot, and phospho-protein array assays. Results: Adavosertib reduced viability at submicromolar IC₅₀ values (0.26–0.56 µM) across all four CTCL lines while largely sparing primary skin cells and was more active in malignant than in healthy donor CD4⁺ T cells. It induced apoptosis and cell-line-specific S-phase and/or G2/M accumulation, lowered WEE1 and phospho-CDK1 (Tyr15), and increased phospho-H2A.X. A phospho-protein array showed activation of checkpoint and stress signalling. In vivo, adavosertib slowed MyLa xenograft growth. Conclusions: These preclinical data identify WEE1 as a therapeutic target in CTCL and support further preclinical and early-phase clinical evaluation of adavosertib in this disease.

Cutaneous T-cell lymphomas (CTCLs), including mycosis fungoides (MF) and Sézary syndrome (SS), are rare hematological malignancies with limited curative treatment options. Despite early-stage responsiveness, these malignancies often relapse in advanced stages, highlighting the need for novel, durable therapies. Similar to other non-Hodgkin lymphomas (NHLs), MF and SS have a greater incidence rate in males than females. The endocrine contribution to this sex difference is unknown. Although several studies could show a potential role of estrogen receptor β (ERβ) on NHL lymphomagenesis, its impact on CTCL development is unknown. In this study, we investigated LY500307, a selective ERβ agonist, as a potential treatment for CTCL. Our results show that LY500307 selectively reduced the viability of CTCL cells, sparing noncancerous skin cells. Liquid chromatography with tandem mass spectrometry analysis revealed that CTCL cells accumulated significantly higher concentrations of LY500307 than normal skin cells, likely contributing to its selective cytotoxicity. Mechanistically, LY500307 induced apoptosis, G2/M cell cycle arrest, and increased sensitivity to chemotherapeutic agents, particularly Monomethyl auristatin E. Furthermore, LY500307 treatment significantly reduced tumor growth in a CTCL xenograft mouse model without notable toxicity. These findings suggest LY500307 as a promising therapeutic agent for CTCL, warranting further clinical investigation, including the potential for topical applications.

Tryptophan hydroxylases catalyze the first and rate-limiting step in the biosynthesis of serotonin, a well-known neurotransmitter that plays an important role in multiple physiological functions. A reduction of serotonin levels, especially in the brain, can cause dysregulation leading to depression or insomnia. In contrast, overproduction of peripheral serotonin is associated with symptoms like carcinoid syndrome and pulmonary arterial hypertension. Recently, we developed a class of TPH inhibitors based on xanthine-benzimidazoles, characterized by a tripartite-binding mode spanning the binding sites of the cosubstrate pterin and the substrate tryptophan and by chelation of the catalytic iron ion. Herein, we describe the structure-based development of a second generation of xanthine-imidiazopyridines and -imidazothiazoles designed to inhibit TPH1 in the periphery while preventing the interaction with TPH2 in the brain. Lead compound 32 (TPT-004) shows superior pharmacokinetic and pharmacodynamic properties as well as efficacy in preclinical models of peripheral serotonin attenuation and colorectal tumor growth.

Claudins regulate paracellular permeability, contribute to epithelial polarization and are dysregulated during inflammation and carcinogenesis. Variants of the claudin-binding domain of Clostridium perfringens enterotoxin (cCPE) are highly sensitive protein ligands for generic detection of a broad spectrum of claudins. Here, we investigated the preferential binding of YFP- or GST-cCPE fusion proteins to non-junctional claudin molecules. Plate reader assays, flow cytometry and microscopy were used to assess the binding of YFP- or GST-cCPE to non-junctional claudins in multiple in vitro and ex vivo models of human and rat gastrointestinal epithelia and to monitor formation of a tight junction barrier. Furthermore, YFP-cCPE was used to probe expression, polar localization and dysregulation of claudins in patient-derived organoids generated from gastric dysplasia and gastric cancer. Live-cell imaging and immunocytochemistry revealed cell polarity and presence of tight junctions in glandular organoids (originating from intestinal-type gastric cancer and gastric dysplasia) and, in contrast, a disrupted diffusion barrier for granular organoids (originating from discohesive tumor areas). In sum, we report the use of cCPE fusion proteins as molecular probes to specifically and efficiently detect claudin expression, localization and tight junction dysregulation in cell lines, tissue explants and patient-derived organoids of the gastrointestinal tract.

The outcome of stroke is greatly influenced by the state of the blood–brain barrier (BBB). The BBB endothelium is sealed paracellularly by tight junction (TJ) proteins, i.e., claudins (Cldns) and the redox regulator occludin. Functions of Cldn3 and occludin at the BBB are largely unknown, particularly after stroke. We address the effects of Cldn3 deficiency and stress factors on the BBB and its TJs. Cldn3 tightened the BBB for small molecules and ions, limited endothelial endocytosis, strengthened the TJ structure and controlled Cldn1 expression. After middle cerebral artery occlusion (MCAO) and 3-h reperfusion or hypoxia of isolated brain capillaries, Cldn1, Cldn3 and occludin were downregulated. In Cldn3 knockout mice (C3KO), the reduction in Cldn1 was even greater and TJ ultrastructure was impaired; 48 h after MCAO of wt mice, infarct volumes were enlarged and edema developed, but endothelial TJs were preserved. In contrast, junctional localization of Cldn5 and occludin, TJ density, swelling and infarction size were reduced in affected brain areas of C3KO. Taken together, Cldn3 and occludin protect TJs in stroke, and this keeps the BBB intact. However, functional Cldn3, Cldn3-regulated TJ proteins and occludin promote edema and infarction, which suggests that TJ modulation could improve the outcome of stroke.

Improving diagnostic imaging and therapy by targeted compound delivery to pathological areas and across biological barriers is of urgent need. A lipopeptide, P‐CrA‐A2, composed of a highly cationic peptide sequence (A2), an N‐terminally attached palmitoyl chain (P) and cryptophane molecule (CrA) for preferred uptake into blood–brain barrier (BBB) capillary endothelial cells, was generated. CrA allows reversible binding of Xe for NMR detection with hyperpolarized nuclei. The lipopeptide forms size‐optimized micelles with a diameter of about 11 nm at low micromolar concentration. Their high local CrA payload has a strong and switchable impact on the bulk magnetization through Hyper‐CEST detection. Covalent fixation of CrA does not impede micelle formation and does not hamper its host functionality but simplifies Xe access to hosts for inducing saturation transfer. Xe Hyper‐CEST magnetic resonance imaging (MRI) allows for distinguishing BBB endothelial cells from control aortic endothelial cells, and the small micelle volume with a sevenfold improved CrA‐loading density compared to liposomal carriers allows preferred cell labelling with a minimally invasive volume (≈16 000‐fold more efficient than ¹⁹F cell labelling). Thus, these nanoscopic particles combine selectivity for human brain capillary endothelial cells with great sensitivity of Xe Hyper‐CEST MRI and might be a potential MRI tool in brain diagnostics.

At the blood–brain barrier (BBB), claudin (Cldn)-5 is thought to be the dominant tight junction (TJ) protein, with minor contributions from Cldn3 and -12, and occludin. However, the BBB appears ultrastructurally normal in Cldn5 knock-out mice, suggesting that further Cldns and/or TJ-associated marvel proteins (TAMPs) are involved. Microdissected human and murine brain capillaries, quickly frozen to recapitulate the in vivo situation, showed high transcript expression of Cldn5, -11, -12, and -25, and occludin, but also abundant levels of Cldn1 and -27 in man. Protein levels were quantified by a novel epitope dilution assay and confirmed the respective mRNA data. In contrast to the in vivo situation, Cldn5 dominates BBB expression in vitro, since all other TJ proteins are at comparably low levels or are not expressed. Cldn11 was highly abundant in vivo and contributed to paracellular tightness by homophilic oligomerization, but almost disappeared in vitro. Cldn25, also found at high levels, neither tightened the paracellular barrier nor interconnected opposing cells, but contributed to proper TJ strand morphology. Pathological conditions (in vivo ischemia and in vitro hypoxia) down-regulated Cldn1, -3, and -12, and occludin in cerebral capillaries, which was paralleled by up-regulation of Cldn5 after middle cerebral artery occlusion in rats. Cldn1 expression increased after Cldn5 knock-down. In conclusion, this complete Cldn/TAMP profile demonstrates the presence of up to a dozen TJ proteins in brain capillaries. Mouse and human share a similar and complex TJ profile in vivo, but this complexity is widely lost under in vitro conditions.