Molecular mechanisms in haematological malignancies

Haematopoiesis requires the constant production of large numbers of peripheral blood cells. This process is under tight control of transcription factor networks as well as cytokines, growth factors and hormones. We will review the importance of transcription factors in programming the haematopoietic lineage commitment and the role of the microenvironment and the corresponding cellular sensitivity to ensure production of mature functional cells in response to the physiological demand. Understanding the molecular mechanism of this complex process gives the opportunity to identify the underlying molecular deregulation in haematopoietic malignancies. The different levels of deregulation include hyperproliferation, block in differentiation and sensitivity to growth factors. In this review, leukaemic transformation is selected to give evidence of cell signalling deregulation. The clinical implications will be reviewed in the context of the potential opportunities in the future to identify specific therapeutic patient groups that can be defined using prognostic and predictive biomarkers.peer-reviewe

Skin grafts : local quest for viable alternatives to autologous grafts using silk and acellular dermal matrices

The gold standard with regards to skin transplantation is the use of the patient’s own skin obtained from a healthy donor site. Such grafts can be either full thickness skin or more commonly nowadays, split thickness skin. Various materials, having either natural and or synthetic origins, have been used in the engineering of skin substitutes to-date and these grafts are then confronted against autologous skin grafts. If proven to be successful, such matrices could be utilised in clinical applications such as in the treatment of burn wounds and in cases of skin ulcers amongst others. In this study the primary cells used, keratinocytes and fibroblast, were obtained from donor skin and cultured. Scaffolds of xenogenic (raw silk) as well as of allogenic (acellular dermal matrices) origins were obtained via low-cost methods and seeded using the fibroblasts and keratinocytes so as to determine which gave the closest mimic to skin grafts. Out of the matrices assessed, the raw silk matrix allowed the best colonisation with skin cells in our hands. The ADM matrice also showed some cell colonisation, but will need further experimentation.peer-reviewe

Transcription Factor Binding to, and Regulation of, the HNP-1 defensin Gene Promoter

The defensins are small antibiotic peptides produced during granulocyte differentiation and stored in the azurophilic granules of the mature granulocyte. Defensin is expressed during a brief window in differentiation with mRNA expression peaking at the promyelocyte and early myelocyte stages. Using the promyelocytic leukaemia cell line NB4, nuclear protein binding to the gene sequences immediately upstream of the main transcription start site was studied. Changes in such binding were correlated with mRNA abundance during granulocyte (high defensin) and monocyte (no defensin) NB4 differentiation. Protein-binding sites, signified by changes in DNAse digestion, were recognised at the ets site at positions -59 and -155, the overlapping c/ebp-myb site at position -120/-105 and at numerous c/ebp-aml sites along the first 240 bp of the upstream sequence. Binding to most of the sites, with the exception of the -59 ets site, was seen to be considerably greater (by footprinting studies) with granulocytic extract as opposed to undifferentiated NB4 extract. The presence of a DNase 1 hypersensitive site at position -59 (which overlaps the ets site) seems to be essential for defensin expression. The presence of this site appeared to be correlated with baseline expression since it is absent in footprints seen with the extract of monocytic NB4 cells (which do not express defensin). This site (termed footprint alpha) was shown to bind GABPalpha, the c/ebp-myb site (within footprint beta) was shown to bind C/EBPepsilon whilst the -155 site (in footprint gamma) was shown to bind PU.1 by means of electrophoretic mobility shift assays (EMSAs). Different transcription factors were also shown to compete for binding to particular footprinted sites by means of competition EMSAs. By inserting mutations into the binding sites for these various factors, the ets site at -59 and the c/ebp and myb sites at -120/-105 were shown to be very important for defensin promoter activity. For maximal activity in undifferentiated NB4 cells, both these sites were required, but in differentiated cells maximum promoter activity was obtained with a minimal promoter, -67/+15, which did not include any myb sites. Co-transfection studies showed that C/EBP and GABPalpha could up-regulate defensin expression in NB4 cells. GABPbeta did not co-operate with GABPalpha in undifferentiated cells, but synergised with it in differentiated NB4 cells. In heterologous HeLa cells, defensin promoter activity was stimulated synergistically by C/EBPe with Myb. It was also strongly transactivated by GABPalpha but such transactivation was unexpectedly inhibited by co-expression of GABPbeta, CBFalpha/beta, PU.1 or CHOP-10 were found to co-operate with GABPalphabeta to stimulate transactivation. The pattern of transactivation obtained with GABP factors differed from the classical synergism seen between GABPalpha and GABPbeta. These differences may be due to both the different reporter systems being used, and to the defensin promoter in particular, which appears to bind GABPalpha alone, much more strongly than other promoters such as the neutrophil elastase promoter. The results obtained have been used to create models of possible protein interactions on the defensin promoter. Using known patterns of expression of transcription factors during myeloid differentiation, a model is presented describing probable factor interactions responsible for initial up-regulation and later down regulation during differentiation

Novel applications of COX-2 inhibitors, metformin, and statins for the primary chemoprevention of breast cancer

Recent evidence shows that commonly prescribed drugs, such as non-steroidal anti-inflammatory drugs (NSAIDs), metformin, and statins, may have beneficial roles in the primary chemoprevention of breast cancer. Therefore, these drugs could potentially be used in addition to the hormonal drugs currently used for this purpose (namely, selective estrogen receptor modulators and aromatase inhibitors) due to their alternative mechanisms of action.peer-reviewe

The axolotl model for cancer research : a mini-review

The Mexican axolotl (Ambystoma mexicanum) is one of the most widely used laboratory animals for research. It is able to regenerate multiple structures including the limbs, jaws, tail, spinal cord and skin among other organs. The mechanisms governing regeneration, wound healing, development, and cancer formation are closely linked. There is increasing evidence highlighting the common signalling pathways which link to cancer growth and regeneration whereby dysregulation of the well-balanced and coordinated process of regeneration leads to cancer. This review aims to highlight the regenerative capacity of axolotls and identify how the active molecules from regeneration extracts could lead to major benefits, with directions on how to develop therapeutic approaches for cancer treatment in humans.peer-reviewe

Assessment of the interaction of Portland cement-based materials with blood and tissue fluids using an animal model

Portland cement used in the construction industry improves its properties when wet. Since most dental materials are used in a moist environment, Portland cement has been developed for use in dentistry. The first generation material is mineral trioxide aggregate (MTA), used in surgical procedures, thus in contact with blood. The aim of this study was to compare the setting of MTA in vitro and in vivo in contact with blood by subcutaneous implantation in rats. The tissue reaction to the material was also investigated. ProRoot MTA (Dentsply) was implanted in the subcutaneous tissues of Sprague-Dawley rats in opposite flanks and left in situ for 3 months. Furthermore the material was also stored in physiological solution in vitro. At the end of the incubation time, tissue histology and material characterization were performed. Surface assessment showed the formation of calcium carbonate for both environments. The bismuth was evident in the tissues thus showing heavy element contamination of the animal specimen. The tissue histology showed a chronic inflammatory cell infiltrate associated with the MTA. MTA interacts with the host tissues and causes a chronic inflammatory reaction when implanted subcutaneously. Hydration in vivo proceeds similarly to the in vitro model with some differences particularly in the bismuth oxide leaching patterns.peer-reviewe

Preservation techniques of the human cadaveric eye

Various preservation methods have been devised to prolong the storage of human cadavers that are donated for research and training purposes. However, the majority of these embalming solutions fail to maintain the structure of the human cadaveric bulbi oculi intact, as they have a tendency to become deflated and dehydrated post-mortem. In fact, as a result, many ophthalmic surgery tuition centers are currently resorting to the use of fresh animal eyes to aid their students in mastering ocular surgical techniques. The objective of this literature review is to identify methods that warrant further investigation as they may aid in devising effective preservation techniques for the human cadaveric eye. Methods that can possibly be applied to increase the intra-ocular pressure and prevent deflation of the human cadaveric eye include: the administration of increased fluid injections to increase volume, application of the head-down tilt, cauthery or clamping of the optic nerve and ophthalmic vessels, induction of corneal rigidity as well as alteration of angle closure and cerebrospinal fluid pressure. Moreover, several corneal artificial hydration solutions exist that warrant further experimentation to establish if they can also be used to prevent dehydration of the human cadaveric eye. These include: hyaluronic acid or carboxymethylcellulose-based solutions, trehalose-based solutions, hydroxypropyl-guar or hypromellose-based solutions as well as hypotonic or isotonic saline.peer-reviewe

The development of the sympathetic system of the heart

Development of the sympathetic nervous system begins at about embryonic day 9 in mice with the migration of the neural crest cells to the dorsal aorta and the development of neurons and the sympathetic ganglia. This is followed by the axonal elongation towards the developing cardiac tissue. This process is directed by a series of signal ligands including ephrin-B1, semaphorin 3a (Sema3a), F-Spondin, bone morphogenetic proteins (BMPs), Wnt-1 protein, neurotrophin-3 (NT-3), nerve growth factor (NGF) and artemin (ARTN). Once at the developing heart, the nerve fibres follow the coronary veins in the subepicardium using NGF and the chemorepellent Sema3a as signals. Here they interact with the cardiac conduction system. Although these cardiac neural cells are part of the autonomic system, they are developed later, mainly on the epicardial surface. Bilateral innervation of the heart comes from the middle cervical stellate (MC-S) ganglion. Although the left ventricle and atrium receive noradrenaline from the MC-S on both sides, the right ventricle receives more from the MC-S from the left rather than from the right side. The development of the great vessels also contributes towards the pattern of development of cardiac innervation. The afferent fibres leaving the heart are also described. Their development relates to the sympathetic innervation of the heart and therefore to cardiac sensations. We hypothesise about how this reflects on the patterns of ischaemic cardiac pain.peer-reviewe

Chemical approaches to targeting drug resistance cancer stem cells

STEMCHEM is a COST action aiming to target causes of drug resistance in cancer stem cells. Cancer stem cells are cells which are believed to be responsible for the larger part of the regenerative capacity of cancers. They are also thought to be similar to adult stem cells in that they do not proliferate most of the time and are thus resistant to many kinds of chemotherapy. The action brings together labs around Europe in both biological and chemical fields to work together in this regard. Biologists targeting individual stem-cell related molecules as well as stem cell phenotypes (like the un-diff erentiated state), test chemicals from numerous labs for activity in high throughput screens, with the aim of identifying new drug targets. This COST action, like most others, o ffers opportunities for Malta, both in a general way and also particularly for a small country with small labs.peer-reviewe

Influence of environment on testing of hydraulic sealers

Abstract In vitro material testing is undertaken by conducting a series of tests following procedures outlined in international standards. All material properties are measured in water; however biological behavior is undertaken in alternative media such as Dulbecco’s modified eagle medium (DMEM) or simulated body fluid. The aim of this study was to characterize four dental root canal sealers and study their properties in different media. Four dental root canal sealers were assessed. They were characterized by a combination of techniques and the sealer properties were tested as specified by ISO 6876 (2012) and also in alternative media. The sealer biocompatibility was measured by cell function and proliferation assays of elutions. All sealers complied with ISO specifications. The material properties were effected by the type of soaking medium used and the surface micromorphology and elemental composition were dependent on the soaking solution type. Both BioRoot and MTA Fillapex showed cytotoxicity which reduced at higher dilutions. The material chemistry, presentation, environmental conditions and testing methodology used affected the sealer properties. Standards specific to sealer type are thus indicated. Furthermore the methodology used in the standard testing should be more relevant to clinical situations