The Fas ligand intracellular domain is released by ADAM10 and SPPL2a cleavage in T-cells.

Fas ligand (FasL) is a type II transmembrane protein belonging to the tumor necrosis factor family. Its binding to the cognate Fas receptor triggers the apoptosis that plays a pivotal role in the maintenance of immune system homeostasis. The cell death-inducing property of FasL has been associated with its extracellular domain, which can be cleaved off by metalloprotease activity to produce soluble FasL. The fate of the remaining membrane-anchored N-terminal part of the FasL molecule has not been determined. Here we show that post-translational processing of overexpressed and endogenous FasL in T-cells by the disintegrin and metalloprotease ADAM10 generates a 17-kDa N-terminal fragment, which lacks the receptor-binding extracellular domain. This FasL remnant is membrane anchored and further processed by SPPL2a, a member of the signal peptide peptidase-like family of intramembrane-cleaving proteases. SPPL2a cleavage liberates a smaller and highly unstable fragment mainly containing the intracellular FasL domain (FasL ICD). We show that this fragment translocates to the nucleus and is capable of inhibiting gene transcription. With ADAM10 and SPPL2a we have identified two proteases implicated in FasL processing and release of the FasL ICD, which has been shown to be important for retrograde FasL signaling.

Thyroglobulin fluctuations in patients with iodine-refractory differentiated thyroid carcinoma on lenvatinib treatment - initial experience.

Tyrosine kinase inhibitors (TKI) have shown clinical effectiveness in iodine-refractory differentiated thyroid cancer (DTC). The corresponding role of serum thyroglobulin (Tg) in iodine-refractory DTC has not been investigated yet. 9 patients (3 female, 61 ± 8y) with progressive iodine-refractory DTC starting on lenvatinib were considered. Tumor restaging was performed every 2-3 months including contrast-enhanced computed tomography (CT, RECIST 1.1). Serum Tg was measured and compared to imaging findings. After treatment initiation, serum Tg levels dropped in all patients with a median reduction of 86.2%. During long-term follow-up (median, 25.2 months), fluctuations in Tg could be observed in 8/9 subjects. According to RECIST, 6/9 subjects achieved a partial response or stable disease with the remaining 3/9 experiencing progressive disease (2/3 with Tg levels rising above baseline). All of the patients with disease progression presented with a preceding continuous rise in serum Tg, whereas tumor marker oscillations in the subjects with controlled disease were only intermittent. Initiation of lenvatinib in iodine-refractory DTC patients is associated with a significant reduction in serum Tg levels as a marker of treatment response. In the course of treatment, transient Tg oscillations are a frequent phenomenon that may not necessarily reflect morphologic tumor progression.

Prognostic Value of Serum Tumor Markers in Medullary Thyroid Cancer Patients Undergoing Vandetanib Treatment.

Tyrosine kinase inhibitors (TKIs) such as vandetanib have shown clinical effectiveness in advanced medullary thyroid cancer (MTC). During TKI treatment, fluctuations in the tumor markers carcinoembryonic antigen (CEA) and calcitonin (CTN) are frequently observed. Their role for treatment monitoring and the decision-making process has not been fully elucidated yet.Twenty-one patients (male, 16, female, 5; mean age, 49 ±â€Š13 years) with progressive MTC receiving vandetanib (300 mg orally per day) were considered. Tumor restaging was performed every 3 months including contrast-enhanced computed tomography (CT). Response was assessed according to recent criteria (Response Evaluation Criteria in Solid Tumors, RECIST 1.1). Additionally, CEA and CTN were measured at the day of CT imaging and alterations observed in tumor markers were compared to respective imaging findings (partial response, PR; stable disease, SD; progressive disease, PD).During long-term follow-up (510 ±â€Š350 days [range, 97-1140 days]), CTN and CEA levels initially dropped in 71.4% and 61.9% of the patients followed by fluctuations in serum marker levels. A rise in CTN ≥39.5% between 2 subsequent measurements (defined by ROC analysis) had a sensitivity of 70.6% and a specificity of 83.2% in predicting PD with an accuracy of 82.0% (area under the curve (AUC), 0.76). Oscillations in CEA levels were not predictive for PD.Whereas tumor marker fluctuations in MTC patients undergoing TKI treatment are a frequent phenomenon, a significant rise in CTN ≥40% turns out to as an early indicator of tumor progression.

Palmitoylation of human FasL modulates its cell death-inducing function.

Fas ligand (FasL) is a transmembrane protein that regulates cell death in Fas-bearing cells. FasL-mediated cell death is essential for immune system homeostasis and the elimination of viral or transformed cells. Because of its potent cytotoxic activity, FasL expression at the cell surface is tightly regulated, for example, via processing by ADAM10 and SPPL2a generating soluble FasL and the intracellular fragments APL (ADAM10-processed FasL form) and SPA (SPPL2a-processed APL). In this study, we report that FasL processing by ADAM10 counteracts Fas-mediated cell death and is strictly regulated by membrane localization, interactions and modifications of FasL. According to our observations, FasL processing occurs preferentially within cholesterol and sphingolipid-rich nanodomains (rafts) where efficient Fas-FasL contact occurs, Fas receptor and FasL interaction is also required for efficient FasL processing, and FasL palmitoylation, which occurs within its transmembrane domain, is critical for efficient FasL-mediated killing and FasL processing.