Indirect CD4+ T‐cell‐mediated elimination of MHC IINEG tumor cells is spatially restricted and fails to prevent escape of antigen‐negative cells

Tumor‐specific Th1 cells can activate tumor‐infiltrating macrophages that eliminate MHC class II negative (MHC II^NEG) tumor cells. Activated M1‐like macrophages lack antigen (Ag) receptors, and are presumably unable to discriminate and thus kill both Ag‐positive (Ag^POS) and Ag‐negative (Ag^NEG) tumor cells (bystander killing). The lack of specificity of macrophage‐mediated cytotoxicity might be of clinical importance as it could provide a means of avoiding tumor escape. Here, we have tested this idea using mixed populations of Ag^POS and Ag^NEG tumor cells in a TCR‐transgenic model in which CD4⁺ T cells recognize a secreted tumor‐specific antigen. Surprisingly, while Ag^POS tumor cells were recognized and rejected, Ag^NEG cells grew unimpeded and formed tumors. We further demonstrated that macrophage‐mediated cytotoxicity was spatially restricted to areas dominated by Ag^POS tumor cells, sparing Ag^NEG tumor cells in the vicinity. As a consequence, macrophage tumoricidal activity did not confer bystander killing in vivo. The present results offer novel insight into the mechanisms of indirect Th1‐mediated elimination of MHC II^NEG tumor cells.     

Exomic analysis of myxoid liposarcomas,synovial sarcomas,and osteosarcomas

Bone and soft tissue sarcomas are a group of histologically heterogeneous and relatively uncommon tumors. To explore their genetic origins, we sequenced the exomes of 13 osteosarcomas, eight myxoid liposarcomas (MLPS), and seven synovial sarcomas (SYN). These tumors had few genetic alterations (median of 10.8). Nevertheless, clear examples of driver gene mutations were observed, including canonical mutations in TP53, PIK3CA, SETD2, AKT1, and subclonal mutation in FBXW7. Of particular interest were mutations in H3F3A, encoding the variant histone H3.3. Mutations in this gene have only been previously observed in gliomas. Loss of heterozygosity of exomic regions was extensive in osteosarcomas but rare in SYN and MLPS. These results provide intriguing nucleotide‐level information on these relatively uncommon neoplasms and highlight pathways that help explain their pathogenesis. © 2013 Wiley Periodicals, Inc.     

Silver carbene complexes: An emerging class of anticancer agents

Cancer is a major global health problem with large therapeutic challenges. Although substantial progress has been made in cancer therapy, there still remains a need to develop novel and effective treatment strategies to treat several relapsed and refractory cancers. Recently, there has been growing demand for considering organometallics as antineoplastic agents. This review is focused on a group of organometallics, silver N-heterocyclic carbene complexes (SCCs) and their anticancer efficacy in targeting multiple pathways in various in vitro cancer model systems. However, the precise molecular mechanism of SCCs anticancer properties remains unclear. Here, we discuss the SCCs chemistry, potential molecular targets, possible molecular mechanism of action, and their application in cancer therapies.     

Microbial-induced meprin β cleavage in MUC2 mucin and a functional CFTR channel are required to release anchored small intestinal mucus

The mucus that covers and protects the epithelium of the intestine is built around its major structural component, the gel-forming MUC2 mucin. The gel-forming mucins have traditionally been assumed to be secreted as nonattached. The colon has a two-layered mucus system where the inner mucus is attached to the epithelium, whereas the small intestine normally has a nonattached mucus. However, the mucus of the small intestine of meprin β-deficient mice was now found to be attached. Meprin β is an endogenous zinc-dependent metalloprotease now shown to cleave the N-terminal region of the MUC2 mucin at two specific sites. When recombinant meprin β was added to the attached mucus of meprin β-deficient mice, the mucus was detached from the epithelium. Similar to meprin β-deficient mice, germ-free mice have attached mucus as they did not shed the membrane-anchored meprin β into the luminal mucus. The ileal mucus of cystic fibrosis (CF) mice with a nonfunctional cystic fibrosis transmembrane conductance regulator (CFTR) channel was recently shown to be attached to the epithelium. Addition of recombinant meprin β to CF mucus did not release the mucus, but further addition of bicarbonate rendered the CF mucus normal, suggesting that MUC2 unfolding exposed the meprin β cleavage sites. Mucus is thus secreted attached to the goblet cells and requires an enzyme, meprin β in the small intestine, to be detached and released into the intestinal lumen. This process regulates mucus properties, can be triggered by bacterial contact, and is nonfunctional in CF due to poor mucin unfolding.The gastrointestinal (GI) tract is protected from self-digestion and microbiota by mucus (1). This mucus is differently organized throughout the GI tract: the stomach and colon have a two-layered mucus system with an inner mucus layer attached to the epithelium and formed by stratified mucin sheets (2). This layer is 50–200 µm thick and impenetrable for bacteria, is constantly renewed by secreted mucins from the goblet cells, and further toward the lumen proteolytically converted into a nonattached and less dense outer mucus layer. This outer layer is the habitat and nutritional source for the commensal bacteria (2). In contrast, the small intestine has only one single mucus type that is not attached to the epithelium (3).The main structural component of the intestinal mucus is the heavily glycosylated polymeric MUC2 mucin which is densely packed inside the goblet cell and after secretion and a 1,000-fold expansion forms flat, net-like structures stacked into stratified mucin sheets in the colon (4). The same MUC2 mucin is processed differently in the small intestine where it appeared less organized but still filled the space between villi (3). This mucus was easily aspirated and penetrable to beads the size of bacteria (3). Bacteria could penetrate, but still the space between the villi was kept free of bacteria in the small intestine due to effective intestinal peristalsis, fast mucus renewal, and a high concentration of antibacterial peptides and proteins (3, 5). In fact, the structure of the small intestinal mucus as a nonattached and less organized layer mimics the situation for the outer colon mucus layer that has been shown to be generated from the inner mucus layer by proteolytic processing of the MUC2 mucin (2).Meprins are zinc-dependent metalloendopeptidases and belong to the astacin family (6). They comprise two homologous enzymes, meprin α and meprin β, where meprin α is the secreted and meprin β the membrane-tethered variant. They can form heterodimers (meprin α and β), homodimers (meprin β), and large oligomers (meprin α), forming one of the largest secreted protease complexes known. Although both enzymes share a common domain structure, they exhibit distinct features in substrate recognition and cleavage specificities. The enzymes can hydrolyze a broad variety of substrates, such as growth factors, peptide hormones, or compounds of the extracellular matrix like procollagen III, fibronectin, and tenascin-C (7–9). The meprin β enzyme is highly expressed in the enterocytes of the small intestine and is thereby localized close to the mucin networks (10).Cystic fibrosis (CF) is a severe disease that affects most of the mucus-producing organs of the body (11). The disease is caused by a nonfunctional cystic fibrosis transmembrane conductance regulator (CFTR) channel that normally mediates passive transport of chloride and bicarbonate ions (12, 13). Although a majority of the clinical CF symptoms can be attributed to stagnant mucus, the more precise link between the lack of CFTR function and mucus properties has been difficult to understand. We recently showed that the small intestinal mucus of CF mice, in contrast to the WT, was attached to the epithelium and impossible to aspirate (14). Although CF mice have only minor lung problems, their intestinal phenotype is similar to the human disease characterized by meconium ileus and distal intestinal obstruction syndrome (DIOS). When the CF mucus was secreted into a solution of ∼100 mM bicarbonate, the mucus was released from its attachment. Mucins are densely packed in the goblet cell granulae due to Ca²⁺ ions and low pH, and the role of bicarbonate is to remove the Ca²⁺ ions and increase the pH to allow for the >1,000-fold mucin expansion (4). When already formed mucus was treated with bicarbonate, the mucus was normalized and possible to aspirate, although its increased mucin density remained largely unaltered (14). This suggested that mucin attachment and expansion might be different phenomena and made us analyze this further.We have now found that meprin β is able to cleave the MUC2 mucin N terminus and that this is involved in the detachment of the mucus of the small intestine in a process controlled by bacteria and a functional CFTR channel. We thus describe a fundamental constitutive mechanism which involves an endogenous protease acting on the mucus network to alter its attached properties.     

Extreme sarcoplasmic reticulum volume loss and compensatory T-tubule remodeling after Serca2 knockout

Cardiomyocyte contraction and relaxation are controlled by Ca(2+) handling, which can be regulated to meet demand. Indeed, major reduction in sarcoplasmic reticulum (SR) function in mice with Serca2 knockout (KO) is compensated by enhanced plasmalemmal Ca(2+) fluxes. Here we investigate whether altered Ca(2+) fluxes are facilitated by reorganization of cardiomyocyte ultrastructure. Hearts were fixed for electron microscopy and enzymatically dissociated for confocal microscopy and electrophysiology. SR relative surface area and volume densities were reduced by 63% and 76%, indicating marked loss and collapse of the free SR in KO. Although overall cardiomyocyte dimensions were unaltered, total surface area was increased. This resulted from increased T-tubule density, as revealed by confocal images. Fourier analysis indicated a maintained organization of transverse T-tubules but an increased presence of longitudinal T-tubules. This demonstrates a remarkable plasticity of the tubular system in the adult myocardium. Immunocytochemical data showed that the newly grown longitudinal T-tubules contained Na(+)/Ca(2+)-exchanger proximal to ryanodine receptors in the SR but did not contain Ca(2+)-channels. Ca(2+) measurements demonstrated a switch from SR-driven to Ca(2+) influx-driven Ca(2+) transients in KO. Still, SR Ca(2+) release constituted 20% of the Ca(2+) transient in KO. Mathematical modeling suggested that Ca(2+) influx via Na(+)/Ca(2+)-exchange in longitudinal T-tubules triggers release from apposing ryanodine receptors in KO, partially compensating for reduced SERCA by allowing for local Ca(2+) release near the myofilaments. T-tubule proliferation occurs without loss of the original ordered transverse orientation and thus constitutes the basis for compensation of the declining SR function without structural disarrangement.     

Bisphosphonate-induced osteonecrosis of the jaw in a rat model arises first after the bone has become exposed. No primary necrosis in unexposed bone

J Oral Pathol Med (2012) 41 : 494–499 Background: Bisphosphonate‐related osteonecrosis of the jaw was first described to start with sterile osteocyte death, similar to osteonecrosis in other parts of the skeleton. The typical chronic osteomyelitis was thought to develop when the dead bone was exposed to the oral cavity. An alternative explanation would be that the chronic osteomyelitis is a result of a bisphosphonate‐related inability of infected bony lesions to heal. We tested the hypothesis that primary osteocyte death is not necessary for the development of jaw osteonecrosis. Material and methods: Forty rats were randomly allocated to four groups of 10. All animals underwent unilateral molar extraction and received the following drug treatments: Group I, controls with no drug treatment; Group II, 200 μg/kg per day alendronate; Groups III and IV, 200 μg/kg per day alendronate and 1 mg/kg of dexamethasone. All rats were euthanized after 14 days. Presence of osteonecrosis was determined by clinical and histological observations for groups I–III. For group IV, osteocyte viability at the contralateral uninjured site was examined using lactate dehydrogenase histochemistry (LDH). Results: All animals in the alendronate plus dexamethasone groups developed large ONJ‐like lesions. Lactate dehydrogenase staining showed viable osteocytes in the contralateral jaw with no tooth extraction. No signs of osteonecosis were seen in the other groups. Conclusion: Bisphosphonates and dexamethasone caused no osteocyte death in uninjured bone, but large ONJ‐like lesions after tooth extraction. Osteonecrosis of the jaw appears to arise first after the bone has been exposed. Possibly, bisphosphonates hamper the necessary resorption of bone that has become altered because of infection.     

A retrospective evaluation of iatrogenic dental root damage with predrilled vs drill-free bone anchor screws for intermaxillary fixation

Abstract – Aims: The aim of this study was to retrospectively evaluate iatrogenic dental root damage, caused by two different techniques that utilized bone anchor screws, for intermaxillary fixation (IMF) in orofacial trauma. Materials and methods: The techniques used included either predrilled or drill‐free bone anchor screws. A total of 123 patients who required IMF were evaluated (97 men and 26 women). Sixty‐four patients were treated in the predrilled group, and 59 patients were treated in the drill‐free group. The data were collected over an 8‐year period and were analyzed using crosstabs and Fisher’s exact test. Results: Injuries to dental roots were found only in the predrilled group. Twenty‐nine patients (45.3%) were injured at the time of surgery. One year after surgery, 10 patients (15.6%) had permanently injured dental roots. There was a significant difference in injury rates between the predrilled and drill‐free groups 1 year after surgery (P < 0.001). Conclusion: There is an increased potential risk of iatrogenic injury and permanent damage to the dental roots when a technique that involves predrilled holes for bone anchor screws is used.