Immediate Versus Deferred Systemic Therapy in Patients With Mesothelioma.

BACKGROUND: The 2018 ASCO pleural mesothelioma (PM) treatment guideline states that "a trial of expectant observation may be offered" in patients with asymptomatic inoperable epithelioid mesothelioma with low disease burden. The aim of our analysis was to evaluate clinical characteristics and outcomes in PM-patients managed with initial observation and deferred treatment initiation. METHODS: We retrospectively collected clinicodemograhic and outcome data of patients with inoperable PM. Patients were assigned to 2 treatment decision groups: decision to start immediate systemic treatment (Immediate Treatment Group) versus observation and deferring treatment (Deferred Treatment group). RESULTS: Of 222 patients with advanced PM, systemic treatment was started immediately in the majority of patients (189, 85%; immediate group); treatment was deferred in 33 (15%) patients (deferred group); systemic therapy was chemotherapy-based in 91% and 79% respectively. Patients in the deferred group were older (70 vs 67 years, p = .05), less likely to have stage IV disease (28% vs. 51%, p = .08) and more often had epithelioid histology (90% vs. 70%, p = .03). Nineteen patients (58%) in the deferred group eventually received treatment. With a median follow-up time of 10.9 months median overall survival (OS) in the entire cohort was 12.4 months and was significantly longer in the deferred group (20.6 months vs. 11.5 months, p = .02). No difference in median progression-free survival (PFS) in first-line treatment between groups was seen (5.4 and 5.3 months). CONCLUSION: This real-world analysis suggests that deferral of systemic therapy and close observation may not impact OS or physician-assessed PFS in selected PM-patients.

Treatment Patterns and Outcomes of Patients With Advanced Pleural Mesothelioma at an Academic Referral Centre.

BACKGROUND: Overall survival (OS) for malignant pleural mesothelioma (MPM) in vulnerable subgroups remains poorly understood with scarce data available to guide treatment decisions. The study describes real-world detailed treatment patterns and outcomes of patients with advanced MPM overall and specifically in elderly and poor performance status (PS) patients. METHODS: Retrospective chart review was performed for all patients with histologically confirmed MPM seen at University Health Network/Princess Margaret Cancer Centre (UHN-PM). RESULTS: A total of 667 patients with MPM were identified and 304 advanced-disease MPM (aMPM) patients had continuing care at UHN-PM (UP-cohort). In the UP-cohort, 77% of patients received ≥ one line of systemic treatment. Systemic therapy trial participation was 39%. Patients not treated with systemic therapy (29%) were more likely to be ≥ 75 years and PS ≥ 2. Median OS was 15.3 months (95%CI 13.6-18.3), with longer survival in treated vs. untreated patients (17.4 vs. 10.6 months; P = .01). Longer survival with systemic treatment was seen in patients ≥75 years (12.7 vs. 6.6 months) and patients with poor PS (9.1 vs. 5.9 months). Median progression-free-survival (PFS) and OS for patients treated with second-line therapy was poor (3.0 and 8.9 months, respectively). DISCUSSION: In our real-world analysis of patients with aMPM treated at an academic referral centre, systemic treatment was given to the majority of patients and benefit was seen even in the elderly and poor PS patients frequently underrepresented in clinical trials. Trial participation was potentially facilitated by the formation of a dedicated multidisciplinary MPM clinic.

A Solid-Phase Approach to Accessing Bisthioether-Stapled Peptides Resulting in a Potent Inhibitor of PRC2 Catalytic Activity.

Stapled peptides have emerged as a new class of therapeutics to effectively target intractable protein-protein interactions. Thus, efficient and versatile methods granting easy access to this class of compounds and expanding the scope(s) of the currently available ones are of great interest. Now, a solid phase approach is described for the synthesis of bisthioether stapled peptides with multiple architectures, including single-turn, double-turn, and double-stapled macrocycles. This method allows for ligation with all-hydrocarbon linkers of various lengths, avoiding the use of unnatural amino acids and expensive catalysts, and affords cyclopeptides with remarkable resistance to proteolytic degradation. The potential of this procedure is demonstrated by applying it to generate a stapled peptide that shows potent in vitro inhibition of methyltransferase activity of the polycomb repressive complex 2 (PRC2) of proteins.

Intracellular Dynamics of the Ubiquitin-Proteasome-System.

The ubiquitin-proteasome system is the major degradation pathway for short-lived proteins in eukaryotic cells. Targets of the ubiquitin-proteasome-system are proteins regulating a broad range of cellular processes including cell cycle progression, gene expression, the quality control of proteostasis and the response to geno- and proteotoxic stress. Prior to degradation, the proteasomal substrate is marked with a poly-ubiquitin chain. The key protease of the ubiquitin system is the proteasome. In dividing cells, proteasomes exist as holo-enzymes composed of regulatory and core particles. The regulatory complex confers ubiquitin-recognition and ATP dependence on proteasomal protein degradation. The catalytic sites are located in the proteasome core particle. Proteasome holo-enzymes are predominantly nuclear suggesting a major requirement for proteasomal proteolysis in the nucleus. In cell cycle arrested mammalian or quiescent yeast cells, proteasomes deplete from the nucleus and accumulate in granules at the nuclear envelope (NE) / endoplasmic reticulum ( ER) membranes. In prolonged quiescence, proteasome granules drop off the nuclear envelopeNE / ER membranes and migrate as droplet-like entitiesstable organelles  throughout the cytoplasm, as thoroughly investigated in yeast. When quiescence yeast cells are allowed to resume growth, proteasome granules clear and proteasomes are rapidly imported into the nucleus. Here, we summarize our knowledge about the enigmatic structure of proteasome storage granules and the trafficking of proteasomes and their substrates between the cyto- and nucleoplasm. Most of our current knowledge is based on studies in yeast. Their translation to mammalian cells promises to provide keen insight into protein degradation in non-dividing cells, which comprise the majority of our body's cells.