Systematic evaluation of AML-associated antigens identifies anti-U5 SNRNP200 therapeutic antibodies for the treatment of acute myeloid leukemia

Despite recent advances in the treatment of acute myeloid leukemia (AML), there has been limited success in targeting surface antigens in AML, in part due to shared expression across malignant and normal cells. Here, high-density immunophenotyping of AML coupled with proteogenomics identified unique expression of a variety of antigens, including the RNA helicase U5 snRNP200, on the surface of AML cells but not on normal hematopoietic precursors and skewed Fc receptor distribution in the AML immune microenvironment. Cell membrane localization of U5 snRNP200 was linked to surface expression of the Fcγ receptor IIIA (FcγIIIA, also known as CD32A) and correlated with expression of interferon-regulated immune response genes. Anti-U5 snRNP200 antibodies engaging activating Fcγ receptors were efficacious across immunocompetent AML models and were augmented by combination with azacitidine. These data provide a roadmap of AML-associated antigens with Fc receptor distribution in AML and highlight the potential for targeting the AML cell surface using Fc-optimized therapeutics.

Modulation of RNA splicing enhances response to BCL2 inhibition in leukemia

Therapy resistance is a major challenge in the treatment of cancer. Here, we performed CRISPR-Cas9 screens across a broad range of therapies used in acute myeloid leukemia to identify genomic determinants of drug response. Our screens uncover a selective dependency on RNA splicing factors whose loss preferentially enhances response to the BCL2 inhibitor venetoclax. Loss of the splicing factor RBM10 augments response to venetoclax in leukemia yet is completely dispensable for normal hematopoiesis. Combined RBM10 and BCL2 inhibition leads to mis-splicing and inactivation of the inhibitor of apoptosis XIAP and downregulation of BCL2A1, an anti-apoptotic protein implicated in venetoclax resistance. Inhibition of splicing kinase families CLKs (CDC-like kinases) and DYRKs (dual-specificity tyrosine-regulated kinases) leads to aberrant splicing of key splicing and apoptotic factors that synergize with venetoclax, and overcomes resistance to BCL2 inhibition. Our findings underscore the importance of splicing in modulating response to therapies and provide a strategy to improve venetoclax-based treatments.

Impaired proteolysis of non-canonical RAS proteins drives clonal hematopoietic transformation

Recently, screens for mediators of resistance to FLT3 and ABL kinase inhibitors in leukemia resulted in the discovery of LZTR1 as an adaptor of a Cullin-3 RING E3 ubiquitin ligase complex responsible for degradation of RAS GTPases. In parallel, dysregulated LZTR1 expression via aberrant splicing and mutations were identified in clonal hematopoietic conditions. Here we identify that loss of LZTR1, or leukemia-associated mutants in the LZTR1 substrate and RAS GTPase RIT1 which escape degradation, drive hematopoietic stem cell (HSC) expansion and leukemia in vivo. While RIT1 stabilization was sufficient to drive hematopoietic transformation, transformation mediated by LZTR1 loss required MRAS. RAS targeting bioPROTACs or reduction of GTP-loaded RAS overcomes LZTR1 loss-mediated resistance to FLT3 inhibitors. These data reveal proteolysis of non-canonical RAS proteins as novel regulators of HSC self-renewal, define the function of RIT1 and LZTR1 mutations in leukemia, and identify means to overcome drug resistance due to LZTR1 downregulation.

Minor intron retention drives clonal hematopoietic disorders and diverse cancer predisposition

Most eukaryotes harbor two distinct pre-mRNA splicing machineries: the major spliceosome, which removes >99% of introns, and the minor spliceosome, which removes rare, evolutionarily conserved introns. Although hypothesized to serve important regulatory functions, physiologic roles of the minor spliceosome are not well understood. For example, the minor spliceosome component ZRSR2 is subject to recurrent, leukemia-associated mutations, yet functional connections among minor introns, hematopoiesis and cancers are unclear. Here, we identify that impaired minor intron excision via ZRSR2 loss enhances hematopoietic stem cell self-renewal. CRISPR screens mimicking nonsense-mediated decay of minor intron-containing mRNA species converged on LZTR1, a regulator of RAS-related GTPases. LZTR1 minor intron retention was also discovered in the RASopathy Noonan syndrome, due to intronic mutations disrupting splicing and diverse solid tumors. These data uncover minor intron recognition as a regulator of hematopoiesis, noncoding mutations within minor introns as potential cancer drivers and links among ZRSR2 mutations, LZTR1 regulation and leukemias.

Single-cell genomics reveals the genetic and molecular bases for escape from mutational epistasis in myeloid neoplasms

Large-scale sequencing studies of hematologic malignancies have revealed notable epistasis among high-frequency mutations. One of the most striking examples of epistasis occurs for mutations in RNA splicing factors. These lesions are among the most common alterations in myeloid neoplasms and generally occur in a mutually exclusive manner, a finding attributed to their synthetic lethal interactions and/or convergent effects. Curiously, however, patients with multiple-concomitant splicing factor mutations have been observed, challenging our understanding of one of the most common examples of epistasis in hematologic malignancies. In this study, we performed bulk and single-cell analyses of patients with myeloid malignancy who were harboring ≥2 splicing factor mutations, to understand the frequency and basis for the coexistence of these mutations. Although mutations in splicing factors were strongly mutually exclusive across 4231 patients (q < .001), 0.85% harbored 2 concomitant bona fide splicing factor mutations, ∼50% of which were present in the same individual cells. However, the distribution of mutations in patients with double mutations deviated from that in those with single mutations, with selection against the most common alleles, SF3B1K700E and SRSF2P95H/L/R, and selection for less common alleles, such as SF3B1 non-K700E mutations, rare amino acid substitutions at SRSF2P95, and combined U2AF1S34/Q157 mutations. SF3B1 and SRSF2 alleles enriched in those with double-mutations had reduced effects on RNA splicing and/or binding compared with the most common alleles. Moreover, dual U2AF1 mutations occurred in cis with preservation of the wild-type allele. These data highlight allele-specific differences as critical in regulating the molecular effects of splicing factor mutations as well as their cooccurrences/exclusivities with one another.

Aberrant RNA Splicing in Cancer

RNA splicing, the enzymatic process of removing segments of premature RNA to produce mature RNA, is a key mediator of proteome diversity and regulator of gene expression. Increased systematic sequencing of the genome and transcriptome of cancers has identified a variety of means by which RNA splicing is altered in cancer relative to normal cells. These findings, in combination with the discovery of recurrent change-of-function mutations in splicing factors in a variety of cancers, suggest that alterations in splicing are drivers of tumorigenesis. Greater characterization of altered splicing in cancer parallels increasing efforts to pharmacologically perturb splicing and early-phase clinical development of small molecules that disrupt splicing in patients with cancer. Here we review recent studies of global changes in splicing in cancer, splicing regulation of mitogenic pathways critical in cancer transformation, and efforts to therapeutically target splicing in cancer.

[PET-CT and PET-MRI of the prostate : From 18F-FDG to 68Ga-PSMA]

CLINICAL/METHODICAL ISSUE

In the last few years nuclear medical diagnostics have experienced a unprecedented renaissance in the diagnostics of prostate cancer, due to the availability of hybrid imaging with positron emission tomography computed tomography (PET/CT), PET magnetic resonance imaging (PET/MRI) and single photon emission computed tomography (SPECT) CT as well as the development of prostate-specific radiopharmaceuticals.

METHODICAL INNOVATIONS

The use of fluorodeoxyglucose (FDG), which has been successfully implemented for many years in PET diagnostics, is only helpful in dedifferentiated tumors due to the biological characteristics of prostate cancer. New specific radiopharmaceuticals, such as choline-derivatives, which are incorporated into the prostate cancer cell and built into the cell membrane as well as the recently developed highly specific ligands for prostate-specific membrane antigen (PSMA) are revolutionizing prostate cancer imaging and (re-) staging.

PRACTICAL RECOMMENDATIONS

The ⁶⁸ Ga-labeled PSMA ligands for PET-CT and PET-MRI are highly specific tracers for primary diagnostics and detection of metastases of prostate carcinoma. In risk patients, which includes patients with intermediate and high-risk tumors, they have largely replaced choline-based PET-CT, especially in the case of very low PSA values <0.5 ng/ml in the diagnostics of recurrence. The use in the primary diagnostics as PET-MRI, also in combination with multiparametric MRI (mpMRI), is promising with respect to early diagnostics and image fusion-assisted biopsy as well as surgery and irradiation planning.

[PSMA-targeted radioligand therapy in prostate cancer]

Radioligand therapy (RLT) directed against prostate-specific membrane antigen (PSMA) enables tumor-specific treatment directed against PSMA-overexpressing prostate cancer cells. Several PSMA ligands such as PSMA-617 or PSMA-I&T have been developed that can be labeled with β‑radiating lutetium-177. These are currently applied in compassionate use programs to treat metastatic castration-resistant prostate cancer (mCRPC). PSMA-directed RLT is currently being offered in several nuclear medicine departments throughout Germany. Several retrospective case series demonstrate its activity with a prostate-specific antigen (PSA) decrease >50% in 30-60% of mCRPC patients. The toxicity seems to be low. Hematologic grade 4 toxicity has not been observed and grade 3 toxicities rarely occur. The main nonhematologic adverse events are intermittent dry mouth because of unspecific PSMA expression in the salivary glands as well as fatigue and nausea. Currently there are no prospective studies available for evaluation of PSMA-targeted RLT and a survival benefit over approved standard therapies such as abiraterone, enzalutamide, radium-223-dichloride, docetaxel or cabazitaxel has not been shown. PSMA-targeted RLT should therefore currently only be offered after critical evaluation in patients who exhausted the approved standard therapies.

The high-pressure behaviour of 3R-NbS2

The high pressure behaviour of 3R-NbS2 has been investigated by angle-dispersive X-ray powder diffraction using diamond anvil cells up to 14 GPa. The compression behaviour of the structure is highly anisotropic. The compressibility perpendicular to the layers is 2.5 times higher than within the layers. A fit of a 3 rd -order Birch-Murnaghan equation of state gave a volume at zero pressure V 0=174(1) Å3 and a bulk modulus b 0=57(1) GPa, with a pressure derivative b'=8.6(5).

Compression mechanism of cubic silica sodalite [Si12O24]: a first principles study of the Im3̅m to I4̅3m phase transition

The high pressure behaviour of cubic silica sodalite has been investigated by ab initio calculations based on density functional theory. The experimentally observed phase transition from the fully-expanded ideal sodalite framework (space group Im3̅m) to a collapsed framework with space group I4̅3m could be successfully reproduced to appear at 0.12 GPa. This transition is discontinuous. The mechanism of the transition can be understood in terms of a tilt of the framework and of deformations of the SiO4-tetrahedra. Discontinuities of the enthalpy, cell volume, Si-O bond lengths and angles at 1.15 and 3.01 Gpa point at further possible pressure-induced iso-symmetric phase transitions in the space group I4̅3m.

Liquid-vapor coexistence at a mesoporous substrate

The condensation of hexane vapor onto a mesoporous Si substrate with a pore radius of 3.5 nm has been studied by means of volumetry and ellipsometry. The filling fraction of the pores and the coverage of the substrate have been determined. The coverage of the regime after the completion of capillary condensation has been compared to recent theoretical work.

Preferred orientations and stability of medium length n-alkanes solidified in mesoporous silicon

The n-alkanes C(16)H(34), C(17)H(36), C(19)H(40), and C(25)H(52) have been imbibed and solidified in mesoporous, crystalline silicon with a mean pore diameter of 10 nm. The structures and phase sequences have been determined by x-ray diffractometry. Apart from a reduction and the hysteresis of the melting-freezing transition, we find a set of six discrete orientation states ("domains") of the confined alkane crystals with respect to the lattice of the silicon host. The growth process responsible for the domain selection is interpreted as a nanoscale version of the Bridgman technique known from single-crystal growth. Oxidation of the pore walls leads to extrusion of the hydrocarbons upon crystallization, whereas the solidified n-alkanes investigated in nonoxidized, porous silicon are thermodynamically stable.

Structural transformations of even-numbered n-alkanes confined in mesopores

The n-alkanes C12H26, C14H30, and C16H34 have been imbibed and solidified in mesoporous Vycor glass with a mean pore diameter of 10 nm. The samples have been investigated by x-ray diffractometry and calorimetric measurements. The structures and phase sequences have been determined. Apart from a reduction and the hysteresis of the melting-freezing transition, pore-confined C12 reproduces the liquid-triclinic phase sequence of the bulk material, but for C16 an orthorhombic rotator mesophase appears that in the bulk state is absent for C16 but well known from odd-numbered alkanes of similar length. In pore-confined C14 this phase shows up on cooling but not on heating.

Compressibility of the nitridosilicate SrYb[Si4N7] and the oxonitridoaluminosilicates MYb[Si4-xAlxOxN7-x] (x = 2; M = Sr, Ba)

The compressibilities of the nitridosilicate SrYb[Si(4)N(7)] and the oxonitridoaluminosilicates MYb[Si(4-x)Al(x)O(x)N(7-x)] (x = 2; M = Sr, Ba) were investigated by in situ high-pressure X-ray powder diffraction. Pressures up to 42 GPa were generated using the diamond-anvil cell technique. The title compounds are structurally stable to the highest pressure obtained. A fit of a third-order Birch-Murnaghan equation-of-state to the p-V data results in V(0) = 302.91 (6) A(3), B(0) = 176 (2) GPa and B' = 4.4 (2) for SrYb[Si(4)N(7)]; V(0) = 310.4 (1) A(3), B(0) = 161 (2) GPa and B' = 4.6 (2) for SrYb[Si(4-x)Al(x)O(x)N(7-x)]; and V(0) = 317.3 (5) A(3), B(0) = 168 (2) GPa and B' = 4.7 (2) for BaYb[Si(4-x)Al(x)O(x)N(7-x)]. While the linear compressibilities of the a and c axes of BaYb[Si(4-x)Al(x)O(x)N(7-x)] are very similar up to 30 GPa, distinct differences were observed for SrYb[Si(4)N(7)] and SrYb[Si(4-x)Al(x)O(x)N(7-x)], with the c axis being the most compressible axis. In all of the investigated compounds the bulk compressibility is dominated by the compression behaviour of the tetrahedral network, while the size of the substituted cation plays a minor role.

Capillary condensation in linear mesopores of different shape

The hysteresis and kinetics of capillary condensation of N2 and Ar in linear mesopores, produced by etching of Si wafers, have been studied for different pore shapes, including the ink bottle geometry. Pore blocking has been observed in the solid state of the pore fillings, but not in the liquid state. We conclude that individual local geometries such as the pore mouth, a blind end, or a single constriction have no effect on the shape of sorption isotherms, that the pore space should be regarded as a statistical ensemble of pore segments with a lot of quenched disorder.

Pattern formation at the bicritical point of the Faraday instability

We present measurements on parametrically driven surface waves (Faraday waves) performed in the vicinity of a bicritical point in parameter space, where modes with harmonic and subharmonic time dependence interact. The primary patterns are squares in the subharmonic and hexagons in the harmonic regime. If the primary instability is harmonic we observe a hysteretic secondary transition from hexagons to squares without a perceptible variation of the fundamental wavelength. The transition is understood in terms of a set of coupled Landau equations and related to other canonical examples of phase transitions in nonlinear dissipative systems. Moreover, the subharmonic-harmonic mode competition gives rise to a variety of new superlattice states. These structures are interpreted as mediator modes involved in the transition between patterns of fourfold and sixfold rotational symmetry.

Aging and memory effects in a clathrate

The out-of-equilibrium low-frequency complex susceptibility of the orientational glass methanol(73%)-beta-hydroquinone-clathrate is studied using temperature-stop protocols in aging experiments. Although the material does not have a sharp glass transition aging effects including rejuvenation and memory similar to the effects in spin glasses are found at low temperatures.

Critical adsorption in a well-defined geometry

A fluid's density profile near a wall is predicted to assume a universal shape near the liquid-vapor critical point, a phenomenon termed critical adsorption. This universal shape is predicted to depend on the boundary conditions of the fluid at the walls and is predicted to be a function of the ratio z/xi, where z is the distance from the wall and xi is the bulk correlation length. A body of evidence confirms the analogous phenomenon of critical adsorption in binary fluids near the critical demixing point, but in the simple liquid-vapor system the experimental situation is not as clear. For example, critical adsorption of SF6 was observed in porous glass for reduced temperature t=T/T(c)-1>10(-3). However, for t<10(-3) a desorption behavior is seen. This desorption has so far resisted rigorous theoretical explanation. We report measurements of the critical adsorption of nitrogen inside a capacitor gap with a simple parallel plate geometry and open gap of 3 microm. Unlike the previous experiments with SF6, the data show a monotonic increase in the adsorption between t=5 x 10(-4) and t=10(-6), consistent with theoretical prediction and without any indication of desorption.

Are solidified fillings of mesopores basically bulk-like except for the geometric confinement?

A short review of our thermodynamic and structural work on Ar, N(2), CO, O(2), and the n-alkane C(19)H(40) in mesoporous glasses is presented. The experimental information comes from X-ray diffraction, vapour pressure isotherms, optical transmission, heat capacity, and dielectric measurements. The filling in the pore centre formed by capillary condensation is distinguished from the adsorbed layers on the pore walls and is compared to the bulk state. Special attention is paid to metastable states and to the rearrangement of partial fillings that show up as a consequence of phase transitions.

Multilayer adsorption and wetting of acetone on graphite

Adsorption/desorption isotherms of acetone on highly oriented pyrolytic graphite have been measured by ellipsometry for temperatures above the bulk triple point. The behavior in the monolayer and submonolayer regime is conventional, with 2D gas-liquid and 2D liquid-solid coexistence regions. Further liquid monolayers grow on top of the completed monolayer. The growth is basically layer-by-layer. For temperatures between 190 K and the triple point a prewetting-type transition occurs with a thin-thick jump of the layer thickness on adsorption but a layer-wise removal of the film on desorption. In this temperature regime the first monolayer is solid and its molecules are oriented perpendicular to the substrate whereas the higher layers are orientationally disordered polar liquid.

Stoichiometric noncovalent interaction in molecular imprinting

In this review article the function of the binding site monomers in the molecular imprinting procedure is discussed. Especially, new developments towards stoichiometric noncovalent interactions are highlighted. In stoichiometric noncovalent interactions template and binding site monomer in an 1:1 molar ratio are nearly completely bound to each other. This is only possible if the association constants are considerably high (Kass > 900 M(-1)). Using this type of interaction in molecular imprinting no excess of binding sites is necessary and binding sites are only located inside the imprinted cavity. Since all cavities can be reloaded these polymers show high capacity (e.g., for preparative application) and are especially suited for the synthesis of catalytically active imprinted polymers. Discussed are binding site interactions based on amidines (and guanidines), multiple hydrogen bonding, charge-transfer interactions, and host-guest inclusion. The systematic investigation of the underlying binding reaction is described in detail. With low-molecular weight model substances the thermodynamics of the association can be conveniently investigated, e.g., by NMR spectroscopy.

Critical behavior of the frustrated antiferromagnetic six-state clock model on a triangular lattice

We study the antiferromagnetic six-state clock model with nearest neighbor interactions on a triangular lattice with extensive Monte Carlo simulations. We find clear indications of two phase transitions at two different temperatures: Below T(I) a chirality order sets in and by a thorough finite-size-scaling analysis of the specific heat and the chirality correlation length we show that this transition is in the Ising universality class (with a nonvanishing chirality order parameter below T(I)). At T(KT) (<T(I)) the spin-spin correlation length as well as the spin susceptibility diverges according to a Kosterlitz-Thouless (KT) form and spin correlations decay algebraically below T(KT). We compare our results to recent x-ray diffraction experiments on the orientational ordering of CF3Br monolayers physisorbed on graphite. We argue that the six-state clock model describes the universal feature of the phase transition in the experimental system and that the orientational ordering belongs to the KT universality class.

Phase relaxation of Faraday surface waves

Surface waves on a liquid-air interface excited by a vertical vibration of a fluid layer (Faraday waves) are employed to investigate the phase relaxation of ideally ordered patterns. By means of a combined frequency-amplitude modulation of the excitation signal a periodic expansion and dilatation of a square wave pattern is generated, the dynamics of which is well described by a Debye relaxator. By comparison with the results of a linear theory, it is shown that the measured relaxation time allows a precise evaluation of the phase diffusion constant.

Amplitude measurements of Faraday waves

A light reflection technique is used to measure quantitatively the surface elevation of Faraday waves. The performed measurements cover a wide parameter range of driving frequencies and sample viscosities. In the capillary wave regime the bifurcation diagrams exhibit a frequency independent scaling proportional to the wavelength. We also provide numerical simulations of the full Navier-Stokes equations, which are in quantitative agreement up to supercritical drive amplitudes of epsilon approximately equal 20%. The validity of an existing perturbation analysis is found to be limited to epsilon<2.5%.

A geometric centroid principle and its application

A new concept of approximation for rigid point sets is suggested. As a necessary condition of optimality, the principle of the conjoint centroid is proved: to achieve a best approximation, certain co-sets must conjoin their centroids. The practical use of the centroid principle, and how it opens up a non-classical method of modelling various aspects of orientational disorder in crystals, is demonstrated. The principle is applied to the interpretation of density data, to the prediction of high-pressure conformations through qualitative simulations, and to the prediction and computation of disordered sets of possible reorientation pathways which explain the shape of the electron-density distribution reconstructed from diffraction experiments. It is also demonstrated how an inversion of the centroid principle can be used to model forces between the parts of the disordered structures.

Crossover from a square to a hexagonal pattern in faraday surface waves

We report on surface wave pattern formation in a Faraday experiment operated at a very shallow filling level, where modes with a subharmonic and harmonic time dependence interact. Associated with this distinct temporal behavior are different pattern selection mechanisms, favoring squares or hexagons, respectively. In a series of bifurcations running through a pair of superlattices the surface wave pattern transforms between the two incompatible symmetries. The close analogy to two- and three-dimensional crystallography is pointed out.

A strengthened zero-scattering-alloy pressure cylinder for neutron powder diffraction

A strengthened pressure cylinder for piston/cylinder devices is presented for use in angle-dispersive high-pressure neutron powder diffraction. It is shown that these cylinders, manufactured from Ti52/Zr48zero-scattering alloy and strengthened by the shrink-fit method, allow the extension of the accessible pressure range of the Kiel–Berlin Cell I to 22 kbar.

Room-Temperatrue Structure and Geometrical Analysis of the Cubic–Tetragonal Phase Transition in Dodecasil 3C-THF

The structure of dodecasil 3C-tetrahydrofuran [Si68O136]·4M, M = (CH2)4O, at room temperature was determined from a merohedrally twinned crystal in the tetragonal space group I41/a. The deformation of the ideal framework at the cubic tetragonal phase transition at T c ≃ 365 K could be explained mainly by two different symmetry-breaking processes. (i) A tetragonal tetrahedron distortion of the Si(5) tetrahedra and (ii) a hitherto unknown local one-dimensional tilt mechanism, localized in the tetrahedral network. The location of the axes of this tilt system coincides with the positions of the fourfold inversion axes in the space group I41/a. At room temperature the tilt angle is = 24°. The symmetry properties of the tilt system can explain the reduction of space-group symmetry from the space group of the ideal structure Fd\overline 3m to the space group at ambient conditions I41/a. The guest molecule tetrahydrofuran does not fit the cage symmetry and has been found to be dynamically disordered. The average structure shows an off-center location in the [51264] cage and follows the local \overline 4symmetry of the cage.