Protein Arginine Methyltransferases as Therapeutic Targets in Hematological Malignancies

Arginine methylation is a common post-translational modification affecting protein activity and the transcription of target genes when methylation occurs on histone tails. There are nine protein arginine methyltransferases (PRMTs) in mammals, divided into subgroups depending on the methylation they form on a molecule of arginine. During the formation and maturation of the different types of blood cells, PRMTs play a central role by controlling cell differentiation at the transcriptional level. PRMT enzymatic activity is necessary for many cellular processes in hematological malignancies, such as the activation of cell cycle and proliferation, inhibition of apoptosis, DNA repair processes, RNA splicing, and transcription by methylating histone tails' arginine. Chemical tools have been developed to inhibit the activity of PRMTs and have been tested in several models of hematological malignancies, including primary samples from patients, xenografts into immunodeficient mice, mouse models, and human cell lines. They show a significant effect by reducing cell viability and increasing the overall survival of mice. PRMT5 inhibitors have a strong therapeutic potential, as phase I clinical trials in hematological malignancies that use these molecules show promising results, thus, underlining PRMT inhibitors as useful therapeutic tools for cancer treatment in the future.

HSP90 inhibitor NVP-BEP800 affects stability of SRC kinases and growth of T-cell and B-cell acute lymphoblastic leukemias

T-cell and B-cell acute lymphoblastic leukemias (T-ALL, B-ALL) are aggressive hematological malignancies characterized by an accumulation of immature T- or B-cells. Although patient outcomes have improved, novel targeted therapies are needed to reduce the intensity of chemotherapy and improve the prognosis of high-risk patients. Using cell lines, primary cells and patient-derived xenograft (PDX) models, we demonstrate that ALL cells viability is sensitive to NVP-BEP800, an ATP-competitive inhibitor of Heat shock protein 90 (HSP90). Furthermore, we reveal that lymphocyte-specific SRC family kinases (SFK) are important clients of the HSP90 chaperone in ALL. When PDX mice are treated with NVP-BEP800, we found that there is a decrease in ALL progression. Together, these results demonstrate that the chaperoning of SFK by HSP90 is involved in the growth of ALL. These novel findings provide an alternative approach to target SRC kinases and could be used for the development of new treatment strategies for ALL.

Tunable gauge potential for neutral and spinless particles in driven optical lattices

We present a universal method to create a tunable, artificial vector gauge potential for neutral particles trapped in an optical lattice. The necessary Peierls phase of the hopping parameters between neighboring lattice sites is generated by applying a suitable periodic inertial force such that the method does not rely on any internal structure of the particles. We experimentally demonstrate the realization of such artificial potentials, which generate ground-state superfluids at arbitrary nonzero quasimomentum. We furthermore investigate possible implementations of this scheme to create tunable magnetic fluxes, going towards model systems for strong-field physics.

Impact of the virulence-associated MAb3/1 epitope on the physicochemical surface properties of Legionella pneumophila sg1: An issue to explain infection potential?

The relationship between the presence/absence of the virulence-associated MAb3/1 epitope of sixteen Legionella pneumophila serogroup 1 strains and their respective surface physicochemical properties is evidenced from electrokinetic measurements (microelectrophoresis) performed as a function of KNO(3) electrolyte concentration (range 1-100mM, pH∼6.5). Among the bacteria selected, nine original strains constitute the Dresden reference panel and differ according to the presence/absence of the virulence-associated monoclonal antibody MAb3/1 of the O-specific chain of the lipopolysaccharides (LPS). Five isogenic Lens strains, also investigated in the current study, present the epitope MAb3/1 of their LPS and were involved to some extent in the outbreak that stroke the Nord Pas-de-Calais region (France) in 2004. All bacteria exhibit the typical electrokinetic features of soft (permeable) particles. On the basis of Ohshima's model, analysis of the electrophoretic mobility data allows evaluating the intraparticular flow penetration length 1/λ(0) and the (negative) volume charge density ρ(0) that both reflect the structure and chemical composition of the soft bacterial component. Our results show that the virulent MAb3/1 positive strains are characterized on average by 1/λ(0) and ǀρ(0)ǀ values that are about 1.5 times larger and 5 times lower, respectively, than those derived for lesser virulent (MAb3/1 negative) strains. In other words, on average the soft surface layer of MAb3/1 positive strains is significantly less charged and more permeable than those of MAb3/1 negative strains. The intimate correlation between virulence-associated MAb3/1 epitope and charge density carried by the bacterial envelop was further confirmed by lower 1/λ(0) and greater ǀρ(0)ǀ values for lag-1 mutant CS332 strain, lacking the MAb3/1 epitope, compared to the parental strain AM511. A closer inspection of the dispersion in 1/λ(0) and ǀρ(0)ǀ data over the ensemble of analysed bacteria together with the reported number of Legionnaires' disease cases they are responsible for, points out the charge density ǀρ(0)ǀ as the parameter that is most suitable for discriminating highly virulent (MAb3/1 positive) from less virulent (MAb3/1 negative) strains. Although short-range interaction determines infection process, our results suggest that the infection potential of Legionella pneumophila serogroup 1 may be also controlled significantly by non-specific long-range electrostatic repulsion the bacteria undergo when approaching negatively charged host cells to be infected.

[Diagnosis and treatment of soft-tissue tumors]

The diagnostic and therapeutic management of patients with soft-tissue tumors would be similar to the approach used for bone tumors if it were not for one crucial factor: the absolute necessity to recognize a sarcoma. The predominant features are the size of the tumor and its superficial or deep localization. If the tumor is small and superficial, biopsy can be associated with immediate resection without risk of dissemination to the deep tissues: this is the biopsy-resection approach. If the tumor is deep or superficial but large sized, search for locoregional spread with MRI is necessary before undertaking any surgical procedure. MRI can help guide the biopsy and plan resection if the tumor is a sarcoma. A first biopsy is necessary to establish the histological diagnosis and elaborate the therapeutic strategy. Samples should be sent immediately to the pathology lab which should examine sterile fresh tissue. Experience has demonstrated that proper rules for diagnosis and treatment are not necessarily applied initially in approximately one-fourth of all subjects with a malignant soft-tissue tumor. Besides the medical problems caused by this situation, the patient loses a chance for cure. When the tumor is a sarcoma, surgery is the basis of treatment. Complementary radiation therapy may be necessary, particularly for high-grade tumors or if the surgical margin was insufficient. Systemic or locoregional chemotherapy can also be used for high-grade or non-resectable tumors.

Degradation of the Poliovirus 1 genome by chlorine dioxide

AIMS

This study was undertaken to gain an understanding of the factors that influence viral RNA degradation in the presence of chlorine dioxide (ClO(2)), which will be very useful in helping to define the significance of the presence of the viral genome in disinfected water.

METHODS AND RESULTS

We focused our investigation on the influence of ClO(2) on extracted RNA on the one hand, and on the infectious virus on the other. Our first results show that RNA degradation, like viral inactivation, is dose dependent. The influence of the spatial organization of the targeted genomic sequence, as well as that of its size and location (and/or sequence) on degradation of the Poliovirus 1 genome by ClO(2), was studied using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). The results show that the preferential sites of action of ClO(2) appear to be located in the untranslated regions, 5'- and 3'-UTR, a phenomenon influenced by both the presence of secondary structures and the genomic sequence in these regions. Our results also reveal a rapid decrease of infectious particles quantified by the cell culture for the applied dose. Comparison between cell culture and real-time PCR for viral detection reveals disagreement following disinfection treatment, even for the largest targeted fragment (a 6,989-base fragment representing the quasi-whole viral genome).

CONCLUSIONS

The detection of genome fragments is insufficient to confirm the presence of the infectious virus, as each targeted fragment shows a different sensitivity. Hence, the smallest targeted fragment (76 bp) persisted throughout the analysis period, while the longest targeted fragment (6,989 bp) disappeared very rapidly. Highly sensitive regions (i.e. 5'- and 3'-UTR) should be targeted to avoid an overestimation of the risk of viral infection using molecular biology methods in water following disinfection. Further studies in this area are needed.

SIGNIFICANCE AND IMPACT OF THE STUDY

To date, it has not been possible to routinely apply virological controls to drinking water because of the time-consuming nature of the gold standard technique (cell culture) and its inability to detect all serotypes (e.g. Norovirus). Molecular techniques (e.g. real-time RT-PCR) constitute a solution to the rapid and specific detection of all the serotypes. However, ignorance of the mechanisms of viral degradation prevents the validation of PCR for the measurement of the risk of infection to humans following disinfection treatment.

Cathodic Modifications of Platinum Surfaces in Organic Solvent: Reversibility and Cation Type Effects

Cathodic modification of platinum surfaces leads to the formation of iono-platinic phases ([Pt(n-), M+, MX]), which involves the insertion of cations and salts into the platinum electrode. This process was investigated at the local scale by in situ observation of surface electrochemical processes by atomic force microscopy (EC-AFM) techniques as a function of the salt and the injected charge, with special attention about the process reversibility. AFM images recorded in solution after the cathodic modifications of well-defined platinum surfaces [epitaxial platinum deposit on (100) MgO substrate] show drastic modification on the morphology of the surface, confirming previous ex situ studies. The amplitude of the modifications directly depends on both the nature of supporting electrolyte and the quantity of charge injected into the platinum. As long as the injected charge remains small enough to maintain the adhesion of the Pt deposit onto the MgO substrate, the process was found to be fully reversible. Indeed, impressive morphology changes occur under the cathodic treatment (formation of [Pt(n-), M+, MX]) but the initial geometry is totally recovered after reoxidation of the iono-platinic phase. This cycle of reduction-reoxidation can be performed several times without any significant alteration of the recovered surface and of its structural characteristics. It is suggested that the modification starts at the interface solution platinum surface and then its insertion into the platinum surface.

Intermittent dislocation of the flexor hallucis longus tendon

Dislocation of the flexor hallucis longus tendon is an exceptional occurrence. To our knowledge, this is the first case ever reported of an intermittent dislocation in a 17-year-old woman; she was a synchronised swimmer. She consulted for a right internal retro-malleolar syndrome. Voluntary "snap" was triggered by a mechanism which combined maximal ankle dorsiflexion and interphalangeal plantar flexion of the toes. Non-enhanced dynamic helical CT and axial MRI were performed, which revealed the dislocation of the right flexor hallucis longus tendon outside the posterior intertubercular talar groove. Static and dynamic imaging would appear to be required to make this uncommon diagnosis.

Symptomatic palmaris longus muscle variation with MRI and surgical correlation: report of a single case

A young woman presented with a painful soft tissue swelling of the anterior aspect of the distal forearm. MRI revealed a hypertrophied reversed palmaris longus muscle confirmed by surgery, which also showed a second insertion to the flexor carpi radialis tendon. Variants of the palmaris longus muscle are discussed.

[Experimental study of compression by Herbert screw in carpal scaphoid fracture]

PURPOSE OF THE STUDY

The purpose of this experimental work was to obtain a radiographical assessment of the effect of the compression achieved with the Herbert screw due to its different thread diameters by comparing the real and expected reduction of interfragment gap (IFG) on cadaver bones. To better understand and define the limits of this "self-compressing" effect and to study the usefulness of screw sizes smaller than the scaphoid, we measured the maximal and mean reduction of IFG without using the instrumentation.

MATERIAL AND METHODS

Twelve scaphoids were obtained from fresh cadavers. The scaphoid holes were drilled and tapped in the largest axis of the scaphoid, in a central position parallel to an anti-rotation wire. A transverse osteotomy was made in the mid third of the scaphoid to simulate a Schernberg grade III fracture. The real IFG reduction was defined as the difference between the gap measured before and after screwing. The expected IFG reduction was defined by multiplying the number of screw turns by the pitch height per turn.

RESULTS

On the reduction average, a Herbert screw produced a 1.1 mm IFG reduction. The maximal reduction IFG measured was 1.5 mm. For 7 cases, the real IFG reduction was larger than expected, for 4 cases it was smaller than expected and for 1 case the difference was considered negligible. The Fisher test did not demonstrate any significant statistical difference between the real and expected IFG reduction for all scaphoids. The operator perceived a subjective sensation of compression after one screw turn that continued up through the last turn.

DISCUSSION

The Herbert screw develops maximal compression force when all the screw threads are totally anchored in the bone. The interfragment gap closes linearly, bringing the two bone fragments together. However, failure can result if the gap is too wide (>2 mm), the screw is poorly positioned, or there is an inappropriate correspondence between screw length and diameter and scaphoid size. Unlike spongy bone screws, the Herbert screw has a round non-conical tip thread and a shallow thread that do not bring the bone fragments together. The perception of compression corresponds to the passage of the screw through the spongy bone and not to real narrowing of the gap between the fragments. In clinical practice, because of the use of instrumentation for open surgery in carpal scaphoid fracture, it is not necessary to rely on these data, but they can be useful for percutaneous screw insertion without a guidewire and without prior compression or for another localization. Peroperative radiographs should be obtained to assess the quality of the screw position and check reduction and the reality of the compression.

Giant cervical epidural veins after lumbar puncture in a case of intracranial hypotension

A 29-year-old woman presented with dilated epidural veins and incapacitating headache after undergoing a lumbar puncture. Two months later, the results of follow-up MR imaging were normal. These findings suggest that temporary dilation of the epidural vein may occur in association with post-lumbar puncture intracranial hypotension syndrome. In these cases, it seems useful to confirm whether the patient has recently undergone a lumbar puncture.

Anatomical basis of the variable aspects of injuries of the axillary nerve (excluding the terminal branches in the deltoid muscle)

The course of the axillary n. is complex with three points of angulation that may be used to delineate four segments and a fifth segment that corresponds to the intramuscular ending of the nerve in the deltoid m. The purpose of this study was to determine the precise anatomy of the nerve and of its branches, and some morphologic features for each segment. Thirty-two shoulders from embalmed adult cadavers have been studied. The axillary n. was divided in five segments: 1) from its origin to the inferior border of the subscapularis m., 2) from the subscapularis m. to the anterolateral border of the tendon of the long head of the triceps brachii m., 3) from the triceps to the posteromedial part of the surgical neck of the humerus, 4) from the humerus to the entry into the deltoid m., 5) the intramuscular distribution of the nerve in the deltoid m. In each segment from 1 to 4 were noted the origins of the branches to the subscapularis and teres minor mm. and to the scapulohumeral joint, and the origins of the lateral cutaneous branchial n. and of the terminal motor branches to the deltoid m. The length and the diameter of the nerve in the segments and the distance from the segment S1 to the musculotendinous junction of the subscapularis m. were measured. The results showed that the mean diameters were about 4.1 mm in segment 1, 4.1 mm in segment 2 and 3.4 mm in segment 3. The mean distance to the musculotendinous junction was 7.7 mm. Many variations in the levels of origin of the different muscular, articular or cutaneous branches were found without symmetry between the right and left sides. The lateral cutaneous brachial n. was absent in four cases. The results are compared with those in the literature. The division into five segments is proposed to radiologists and surgeons for evaluation or operative procedures on the axillary n., and to provide a hypothesis about the variable aspects of injuries of the nerve.

[Lumbar interapophyseal septic arthritis. Apropos of 3 cases]

Septic arthritis of spinal apophyseal joint, seldom described, mainly concern the lumbar spine. We report three cases. Inflammatory lesions of the paravertebral soft tissues were associated in each case; an epidural abscess was present twice. Our three cases were due to Staphylococcus aureus. The initial clinical features were consistent with a spondylodiscitis. Imaging led to the correct diagnosis in all cases. According to our observations and several others of the literature: facet joint lesions are visible too late on plain films. Bone scintigraphy is sensitive, but not specific. CT scan and MRI are the most contributive investigations. A pathologic aspect of the paravertebral soft tissues is visible less than one week after the beginning of the symptoms on CT scan and MRI. Lesions of the facet joint are detectable as soon as the first week on MRI, and after 15 days of clinical course on CT scan. Epidural abscess, when present, is best shown by MRI as early as the first week. CT scan can guide percutaneous needle biopsies of the paravertebral abscesses or of the concerned facet joint.

[Fatigue fractures]

Stress fractures are extremely common microtraumatic lesions which occur in specific areas of healthy bones. Since clinical findings are often misleading and radiological signs are known to be delayed, diagnosis can be uneasy. In some instances, infectious or tumoral diseases have to be ruled out. Such difficult cases are shown to stress on the potential interest of CT scanner and magnetic resonance imaging.

[Diagnosis of a nonparasitic splenic cyst]

It is reported on a case of the infrequent non-parasitic cyst of the spleen. Here the difficulties of the diagnostics due to the poorness of clinical and laboratory-chemical symptoms are emphasized. After the radiological exclusion of the belonging of the spacial demand to the gastrointestinal canal and to the uropoietic system it is recommended to strive for the angiographical clarification and, when a cyst of the spleen is to be proven, for the splenectomy.