The telomerase inhibitor imetelstat differentially targets JAK2V617F versus CALR mutant myeloproliferative neoplasm cells and inhibits JAK-STAT signaling.

Imetelstat shows activity in patients with myeloproliferative neoplasms, including primary myelofibrosis (PMF) and essential thrombocythemia. Here, we describe a case of prolonged disease stabilization by imetelstat treatment of a high-risk PMF patient enrolled into the clinical study MYF2001. We confirmed continuous shortening of telomere length (TL) by imetelstat treatment but observed emergence and expansion of a KRAST58I mutated clone during the patient's clinical course. In order to investigate the molecular mechanisms involved in the imetelstat treatment response, we generated induced pluripotent stem cells (iPSC) from this patient. TL of iPSC-derived hematopoietic stem and progenitor cells, which was increased after reprogramming, was reduced upon imetelstat treatment for 14 days. However, while imetelstat reduced clonogenic growth of the patient's primary CD34+ cells, clonogenic growth of iPSC-derived CD34+ cells was not affected, suggesting that TL was not critically short in these cells. Also, the propensity of iPSC differentiation toward megakaryocytes and granulocytes was not altered. Using human TF-1MPL and murine 32DMPL cell lines stably expressing JAK2V617F or CALRdel52, imetelstat-induced reduction of viability was significantly more pronounced in CALRdel52 than in JAK2V617F cells. This was associated with an immediate downregulation of JAK2 phosphorylation and downstream signaling as well as a reduction of hTERT and STAT3 mRNA expression. Hence, our data demonstrate that imetelstat reduces TL and targets JAK/STAT signaling, particularly in CALR-mutated cells. Although the exact patient subpopulation who will benefit most from imetelstat needs to be defined, our data propose that CALR-mutated clones are highly vulnerable.

The coordination chemistry of 2,4,6-oxy functionalised 1,3,5-triphosphinines.

A number of stable group 6 metal complexes bearing 2,4,6-oxy functionalised 1,3,5-triphosphinines, phosphorus containing heterocyclic ligands with a central C3P3 core, were synthesised such that a complete series of [M{P3C3(OX)3}(CO)3] compounds is obtained [M = Cr(0), Mo(0), W(0); X = H, SitBuPh2, B(ipc)2]. In all complexes, the triphosphinine coordinates in a η6-binding mode via the delocalized 6π-system of the ring. The ligand properties can be tuned by changing the substituent on the oxygen centre. The π-electron accepting properties of the ligand increases in the following order: P3C3(OH)3 < P3C3(OSitBuPh2)3 < P3C3(OB(ipc)2)3. This trend is reflected in the structures determined by X-ray crystallography, and the ν(CO) stretching frequencies determined by IR spectroscopy. The collected data raise questions with respect to the frequently made assumption that phosphinines act as stronger π-acceptors with respect to arenes and thereby deplete electron density at the metal centres. With P3C3(OH)3 as an η6-coordinated ligand further molecules can be coordinated in the second coordination sphere via hydrogen bonds, which may be of interest for the construction of coordination polymers.

Telomere Shortening in Peripheral Leukocytes Is Associated With Poor Survival in Cancer Patients Treated With Immune Checkpoint Inhibitor Therapy.

BACKGROUND: Immune checkpoint inhibitor (ICI) therapy represents a new standard of care for an increasing number of malignancies. Nevertheless, response rates and outcome of ICI treatment vary between individuals and the identification of predictive markers or hints towards immune cell exhaustion during therapy has remained a major challenge. Leukocyte telomere length is an established predictive biomarker of replicative aging and cellular proliferative potential in various hematological diseases. However, its relevance in the context of ICI therapy has not been investigated to date. Here, we analyze the age-adapted delta telomere length (ΔTL) of peripheral leukocytes as a potential predictive and prognostic marker in patients undergoing ICI therapy. METHODS: Age-adapted delta telomere length (ΔTL) of 84 patients treated with ICIs for solid malignancies was measured via quantitative real-time PCR. ΔTL was correlated with outcome and clinical data. RESULTS: ΔTL was not significantly altered between patients with different tumor entities or tumor stages and did not predict tumor response to ICI therapy. However, ΔTLs at initiation of treatment were a prognostic marker for overall survival (OS). When using a calculated ideal cut-off value, the median OS in patients with shorter ΔTL was 5.7 months compared to 18.0 months in patients showing longer ΔTL. The prognostic role of age-adapted ΔTL was further confirmed by uni- and multivariate Cox-regression analyses. CONCLUSION: In the present study, we demonstrate that shorter telomere lengths in peripheral blood leukocytes are associated with a significantly impaired outcome in patients receiving ICI therapy across different malignancies. We explain our findings by hypothesizing an older replicative age in peripheral leukocytes of patients with an impaired overall survival, reflected by a premature TL shortening. Whether this association is ICI-specific remains unknown. Further follow-up studies are needed to provide insights about the exact mechanism of how shortened telomeres eventually affect OS and could help guiding therapeutic decisions in future.

Reduction of Nitrogen Oxides by Hydrogen with Rhodium(I)-Platinum(II) Olefin Complexes as Catalysts.

The nitrogen oxides NO2 , NO, and N2 O are among the most potent air pollutants of the 21st century. A bimetallic RhI -PtII complex containing an especially designed multidentate phosphine olefin ligand is capable of catalytically detoxifying these nitrogen oxides in the presence of hydrogen to form water and dinitrogen as benign products. The catalytic reactions were performed at room temperature and low pressures (3-4 bar for combined nitrogen oxides and hydrogen gases). A turnover number (TON) of 587 for the reduction of nitrous oxide (N2 O) to water and N2 was recorded, making these RhI -PtII complexes the best homogeneous catalysts for this reaction to date. Lower TONs were achieved in the conversion of nitric oxide (NO, TON=38) or nitrogen dioxide (NO2 , TON of 8). These unprecedented homogeneously catalyzed hydrogenation reactions of NOx were investigated by a combination of multinuclear NMR techniques and DFT calculations, which provide insight into a possible reaction mechanism. The hydrogenation of NO2 proceeds stepwise, to first give NO and H2 O, followed by the generation of N2 O and H2 O, which is then further converted to N2 and H2 O. The nitrogen-nitrogen bond-forming step takes place in the conversion from NO to N2 O and involves reductive dimerization of NO at a rhodium center to give a hyponitrite (N2 O2 2- ) complex, which was detected as an intermediate.

Longitudinal changes in telomere length in PCB-exposed individuals: interaction with CMV infection.

We recently demonstrated a significant shortening of age-adapted telomere length (TL) in lymphocytes of polychlorinated biphenyls (PCB)-exposed individuals. Here, we analyzed TL in individuals of the same PCB-exposed cohort during a 6-year follow-up period, investigating the change in TL between the first and second measurement as a function of time, concentration of PCBs and cytomegalovirus (CMV) infection. The age-adjusted TL of lymphocytes within the cohort of PCB-exposed individuals recovered from a first assessment in 2011 to a second assessment in 2017. Remarkably, if the concentration of lower chlorinated PCBs (LC PCBs) in 2011 was high (≥ 0.055 µg/L), the TL of CMV seropositive individuals remained significantly shortened both compared to age-adjusted controls as well as intra individually. This was confirmed by analysis of covariance as well as by multivariate linear mixed effects models. Since telomeres are responsive to various stress response pathways, including viral infection, we conclude that PCBs could contribute to immune senescence-like phenotypes associated with CMV infections and exacerbate negative aspects associated with the aging of the immune system.

Comparable Effects of the Androgen Derivatives Danazol, Oxymetholone and Nandrolone on Telomerase Activity in Human Primary Hematopoietic Cells from Patients with Dyskeratosis Congenita.

Dyskeratosis congenita (DKC) is a rare inherited disease of impaired telomere maintenance that progressively leads to multi-organ failure, including the bone marrow. By enhancing telomerase activity, androgen derivatives (ADs) are a potential therapeutic option able to re-elongate previously shortened telomeres. Danazol, oxymetholone, and nandrolone are ADs most frequently used to treat DKC. However, no direct in vitro analyses comparing the efficacy of these ADs have been conducted so far. We therefore treated mononuclear cells derived from peripheral blood and bone marrow of four patients with mutations in telomerase reverse transcriptase (TERT, n = 1),in the telomerase RNA component (TERC, n = 2) and in dyskerin pseudouridine synthase 1 (DKC1, n = 1) and found no substantial differences in the activity of these three agents in patients with TERC/TERT mutations. All AD studied produced comparable improvements of proliferation rates as well as degrees of telomere elongation. Increased TERT expression levels were shown with danazol and oxymetholone. The beneficial effects of all ADs on proliferation of bone marrow progenitors could be reversed by tamoxifen, an estrogen antagonist abolishing estrogen receptor-mediated TERT expression, thereby underscoring the involvement of TERT in AD mechanism of action. In conclusion, no significant differences in the ability to functionally enhance telomerase activity could be observed for the three AD studied in vitro. Physicians therefore might choose treatment based on patients' individual co-morbidities, e.g., pre-existing liver disease and expected side-effects.

Comparison of flow-FISH and MM-qPCR telomere length assessment techniques for the screening of telomeropathies.

Assessment of telomere length (TL) in peripheral blood leukocytes is part of the diagnostic algorithm applied to patients with acquired bone marrow failure syndromes (BMFSs) and dyskeratosis congenita (DKC). Monochrome multiplex-quantitative polymerase chain reaction (MM-qPCR) and fluorescence in situ hybridization (flow-FISH) are methodologies available for TL screening. Dependent on TL expressed in relation to percentiles of healthy controls, further genetic testing for inherited mutations in telomere maintenance genes is recommended. However, the correct threshold to trigger this genetic workup is still under debate. Here, we prospectively compared MM-qPCR and flow-FISH regarding their capacity for accurate identification of DKC patients. All patients (n = 105) underwent genetic testing by next-generation sequencing and in 16 patients, mutations in DKC-relevant genes were identified. Whole leukocyte TL of patients measured by MM-qPCR was found to be moderately correlated with lymphocyte TL measured by flow-FISH (r² = 0.34; P < 0.0001). The sensitivity of both methods was high, but the specificity of MM-qPCR (29%) was significantly lower compared with flow-FISH (58%). These results suggest that MM-qPCR of peripheral blood cells is inferior to flow-FISH for clinical routine screening for suspected DKC in adult patients with BMFS due to lower specificity and a higher rate of false-positive results.