BACKGROUND: Paclitaxel chemotherapy frequently induces dose-limiting sensory axonal polyneuropathy. Given that sensory symptoms are challenging to assess objectively in clinical practice, an easily accessible biomarker for chemotherapy-induced polyneuropathy (CIPN) holds the potential to improve early diagnosis. Here, we describe neurofilament light chain (NFL), a marker for neuroaxonal damage, as a translational surrogate marker for CIPN. METHODS: NFL concentrations were measured in an in vitro model of CIPN, exposing induced pluripotent stem cell–derived sensory neurons (iPSC-DSNs) to paclitaxel. Patients with breast or ovarian cancer undergoing paclitaxel chemotherapy, breast cancer control patients without chemotherapy, and healthy controls were recruited in a cohort study and examined before chemotherapy (V1) and after 28 weeks (V2, after chemotherapy). CIPN was assessed by the validated Total Neuropathy Score reduced (TNSr), which combines patient-reported symptoms with data from clinical examinations. Serum NFL (NFL _s ) concentrations were measured at both visits with single-molecule array technology. RESULTS: NFL was released from iPSC-DSNs upon paclitaxel incubation in a dose- and time-dependent manner and was inversely correlated with iPSC-DSN viability. NFL _s strongly increased in paclitaxel-treated patients with CIPN, but not in patients receiving chemotherapy without CIPN or controls, resulting in an 86% sensitivity and 87% specificity. An NFL _s increase of +36 pg/mL from baseline was associated with a predicted CIPN probability of more than 0.5. CONCLUSION: NFL _s was correlated with CIPN development and severity, which may guide neurotoxic chemotherapy in the future. TRIAL REGISTRATION: ClinicalTrials.gov NCT02753036. FUNDING: Deutsche Forschungsgemeinschaft (EXC 257 NeuroCure), BMBF (Center for Stroke Research Berlin, 01 EO 0801), Animalfree Research, EU Horizon 2020 Innovative Medicines Initiative 2 Joint Undertaking (TransBioLine, 821283), Charité 3R — Replace — Reduce — Refine.

Chemotherapy-induced cognitive impairment (CICI) is a well-recognized side effect of breast cancer treatment. However, prospective long-term evaluations of CICI using standardized neuropsychological tests are scarce. This prospective longitudinal cohort study investigated cognitive dysfunction and its impact on quality of life and everyday functioning in patients with breast cancer receiving first-line chemotherapy compared to patients with breast cancer without chemotherapy. Assessment occurred prior to chemotherapy, postchemotherapy (median 6 months), and 2-3 years later. We used standardized neuropsychological tests, questionnaires, and scales to assess patients’ quality of life and functioning. Additionally, serum analysis for neurodegenerative markers and autoantibodies was conducted. We included n = 53 patients. Overall cognitive function declined statistically significantly (P = .046) postchemotherapy compared to control patients, mostly driven by a reduced figural memory (P = .011). Patients who received chemotherapy showed a greater reduction in quality of life (increased fatigue symptoms, P = .023; reduced Karnofsky index, P < .001); however, without a statistically significant effect on cognitive decline. The neurodegenerative markers Neurofilament light chain (NfL) and phosphorylated Neurofilament heavy chain (pNfH) increased statistically significantly (P < .001) postchemotherapy and pNfH correlated with overall cognitive function. After 2-3 years, both cognitive performance and quality of life were comparable between chemotherapy-treated and control patients. Our findings suggest that chemotherapy statistically significantly contributes to overall cognitive dysfunction in patients with breast cancer, which disappears after 2-3 years, indicating a recovery in both objectively measurable cognitive function and subjective quality of life. Future research should examine larger sample sizes and explore screening indicators, particularly pNfH.

A polymorphism in the promoter region of the human serotonin transporter (5-HTT)-coding SLC6A4 gene (5-HTTLPR) has been implicated in moderating susceptibility to stress-related psychopathology and to possess regulatory functions on human in vivo 5-HTT availability. However, data on a direct relation between 5-HTTLPR and in vivo 5-HTT availability have been inconsistent. Additional factors such as epigenetic modifications of 5-HTTLPR might contribute to this association. This is of particular interest in the context of obesity, as an association with 5-HTTLPR hypermethylation has previously been reported. Here, we tested the hypothesis that methylation rates of 14 cytosine–phosphate–guanine (CpG) 5-HTTLPR loci, in vivo central 5-HTT availability as measured with [¹¹C]DASB positron emission tomography (PET) and body mass index (BMI) are related in a group of 30 obese (age: 36±10 years, BMI>35 kg/m²) and 14 normal-weight controls (age 36±7 years, BMI<25 kg/m²). No significant association between 5-HTTLPR methylation and BMI overall was found. However, site-specific elevations in 5-HTTLPR methylation rates were significantly associated with lower 5-HTT availability in regions of the prefrontal cortex (PFC) specifically within the obese group when analyzed in isolation. This association was independent of functional 5-HTTLPR allelic variation. In addition, negative correlative data showed that CpG10-associated 5-HTT availability determines levels of reward sensitivity in obesity. Together, our findings suggest that epigenetic mechanisms rather than 5-HTTLPR alone influence in vivo 5-HTT availability, predominantly in regions having a critical role in reward processing, and this might have an impact on the progression of the obese phenotype.

Neurologic immune-related adverse events (irAE-n) are rare but severe toxicities of immune checkpoint inhibitor (ICI) treatment. To overcome diagnostic and therapeutic challenges, a better mechanistic understanding of irAE-n is paramount. In this observational cohort study, we collected serum and peripheral blood samples from 34 consecutive cancer patients with irAE-n (during acute illness) and 49 cancer control patients without irAE-n (pre- and on-ICI treatment, n = 44 without high-grade irAEs, n = 5 with high-grade nonneurologic irAEs). Patients received either anti-programmed cell death protein (PD)-1 or anti-PD ligand-1 monotherapy or anti-PD-1/anti-cytotoxic T-lymphocyte associated protein-4 combination therapy. Most common cancers were melanoma, lung cancer, and hepatocellular carcinoma. Peripheral blood immune profiling was performed using 48-marker single-cell mass cytometry and a multiplex cytokine assay. During acute illness, patients with irAE-n presented higher frequencies of CD8⁺ effector memory type (EM-)1 and central memory (CM) T cells compared to controls without irAEs. Multi-organ immunotoxicities (neurologic + nonneurologic) were associated with higher CD8⁺ EM1 T cell counts. While there were no B cell changes in the overall cohort, we detected a marked decrease of IgD^- CD11c⁺ CD21^low and IgD^- CD24⁺ CD21^high B cells in a subgroup of patients with autoantibody-positive irAE-n. We further identified signatures indicative of enhanced chemotaxis and inflammation in irAE-n patients and discovered CXCL10 as a promising marker to diagnose high-grade immunotoxicities such as irAE-n. We demonstrate profound and partly subgroup-specific immune cell dysregulation in irAE-n patients, which may guide future biomarker development and targeted treatment approaches.

The peripheral nervous system (PNS) is involved in nociception and gait. The contribution of PNS-resident immune cells to these functions is not fully understood. We identified group 2 innate lymphoid cells (ILC2s) as a distinct immune cell population resident in the PNS, with a unique gene profile facilitating neuron-ILC2 cross-talk. ILC2-deficient mice display PNS dysfunction (hypersensitivity and gait anomalies). These functional deficits are attributed to structural abnormalities in the sciatic nerves of ILC2-deficient mice. ILC2s communicate with dorsal root ganglion neurons via the interleukin-13 (IL-13) signaling pathway to maintain nerve structure and pain thresholds. Loss of the shared IL-4/IL-13 receptor (IL-4R/IL-13R) in neurons results in a phenotype similar to ILC2-deficient mice. Intrathecally administered IL-13 rescues hypersensitivity and gait defects in ILC2-deficient mice, which suggests that this signaling pathway may be therapeutically important. This work therefore identifies a function for ILC2s in regulating the nerve structural integrity and nociceptive functions of the PNS.

Cortical ischemic lesions represent the predominant pathomorphological pattern of focal lesions after aneurysmal subarachnoid hemorrhage (aSAH). Autopsy studies suggest that they occur adjacent to subarachnoid blood and are related to spasm of small cortical rather than proximal arteries. Recent clinical monitoring studies showed that cortical spreading depolarizations, which induce cortical arterial spasms, are involved in lesion development. If subarachnoid blood induces adjacent cortical lesions, it would be expected that (i) they also develop after traumatic subarachnoid hemorrhage (tSAH), and (ii) lesions after tSAH can occur in absence of angiographic vasospasm, as was found for aSAH. An 86-year-old woman was admitted to our hospital with fluctuating consciousness after hitting her head during a fall. The initial computed tomography (CT) was significant for tSAH in cortical sulci. On day 8, the patient experienced a secondary neurological deterioration with reduced consciousness and global aphasia. Whereas the CT scan on day 9 was still unremarkable, magnetic resonance imaging (MRI) on day 10 revealed new cortical laminar infarcts adjacent to sulcal blood clots. Proximal vasospasm was ruled out using MR and CT angiography and Doppler sonography. CT on day 14 confirmed the delayed infarcts. We describe a case of delayed cortical infarcts around sulcal blood clots after tSAH in the absence of proximal vasospasm, similar to results found previously for aSAH. As for aSAH, this case suggests that assessment of angiographic vasospasm is not sufficient to screen for risk of delayed infarcts after tSAH. Electrocorticography is suggested as a complementary method to monitor the hypothesized mechanism of spreading depolarizations.