Citations

Abstract Accumulating evidence suggests that changes in the tumor microenvironment caused by radiotherapy are closely related to the recurrence of glioma. However, the mechanisms by which such radiation‐induced changes are involved in tumor regrowth have not yet been fully investigated. In the present study, how cranial irradiation‐induced senescence in non‐neoplastic brain cells contributes to glioma progression is explored. It is observed that senescent brain cells facilitated tumor regrowth by enhancing the peripheral recruitment of myeloid inflammatory cells in glioblastoma. Further, it is identified that astrocytes are one of the most susceptible senescent populations and that they promoted chemokine secretion in glioma cells via the senescence‐associated secretory phenotype. By using senolytic agents after radiotherapy to eliminate these senescent cells substantially prolonged survival time in preclinical models. The findings suggest the tumor‐promoting role of senescent astrocytes in the irradiated glioma microenvironment and emphasize the translational relevance of senolytic agents for enhancing the efficacy of radiotherapy in gliomas.

Abstract Cytoglobin is a highly conserved redox sensor heme protein with unknown physiological function. Unexpectedly, genetic deletion of zebrafish cytoglobin (cygb2) causes cardiac and gastro-intestinal tract laterality defects, modeling Kartagener’s syndrome, which in humans is associated with low airway epithelial nitric oxide (NO) production. Cygb2 co-localized with cilia and the NO synthase Nos2b in the Kupffer’s vesicle (KV) laterality organ and the structure and function of cilia were disrupted in cygb2 mutants, abolishing fluid flow within the KV. Abnormal ciliary function and organ laterality was phenocopied by depletion of nos2band gucy1a, the canonical NO receptor soluble guanylate cyclase (sGC) homolog in fish, and rescued by exposing cygb2 mutant embryos to an NO donor or an sGC stimulator and with over-expression of nos2b. Consistent with a conserved role in the modulation of ciliary function, cytoglobin knock out in the mouse also impaired airway epithelial ciliary structure and beat frequency. This is the first evidence that cytoglobin is essential for normal development stage-specific NO signaling, ciliogenesis and cilia motility, required for the establishment of left-right patterning.

Trauma to the CNS generates a proteolytic imbalance that contributes to secondary injury, including axonopathy and neuron degeneration; however the mechanism by which this occurs is not well understood. Kallikrein 6 (KLK6) is a serine protease implicated in neurotoxicity and in these studies we investigate the role of protease activated receptors (PARs) in mediating these effects. We demonstrate KLK6 and the prototypical activator of PAR1, thrombin, as well as PAR1 and ‐2, are each elevated in a murine experimental spinal cord injury at acute or subacute time points. KLK6 and thrombin each promoted cerebellar granule neuron toxicity and potentiated glutamate excitotoxicity in vitro. Importantly, neural injury in each case was reduced or blocked in neurons derived from PAR1 deficient mice. KLK6 was shown to activate ERK in cerebellar neurons in a PI3K and MEK‐dependent fashion. Novel lipopeptide inhibitors specific for PAR1 or PAR2, in addition to neurons derived from PAR1 deficient mice were utilized to demonstrate both receptors play an important role in KLK6‐elicited ERK signaling and in the activation of the proapoptotic protein Bim. Taken together these data point to novel KLK6‐PAR1 and ‐PAR2 mediated signaling cascades in CNS neurons that are positioned to participate in neuron degeneration and glutamate‐mediated excitotoxicity in cases of CNS injury. Supported by NIH R01 NS052741

AbstractOligodendrocytes are essential regulators of axonal energy homeostasis and electrical conduction and emerging target cells for restoration of neurological function. Here we investigate the role of protease activated receptor 2 (PAR2), a unique protease activated G protein‐coupled receptor, in myelin development and repair using the spinal cord as a model. Results demonstrate that genetic deletion of PAR2 accelerates myelin production, including higher proteolipid protein (PLP) levels in the spinal cord at birth and higher levels of myelin basic protein and thickened myelin sheaths in adulthood. Enhancements in spinal cord myelin with PAR2 loss‐of‐function were accompanied by increased numbers of Olig2‐ and CC1‐positive oligodendrocytes, as well as in levels of cyclic adenosine monophosphate (cAMP), and extracellular signal related kinase 1/2 (ERK1/2) signaling. Parallel promyelinating effects were observed after blocking PAR2 expression in purified oligodendrocyte cultures, whereas inhibiting adenylate cyclase reversed these effects. Conversely, PAR2 activation reduced PLP expression and this effect was prevented by brain derived neurotrophic factor (BDNF), a promyelinating growth factor that signals through cAMP. PAR2 knockout mice also showed improved myelin resiliency after traumatic spinal cord injury and an accelerated pattern of myelin regeneration after focal demyelination. These findings suggest that PAR2 is an important controller of myelin production and regeneration, both in the developing and adult spinal cord.

Hemorrhagic white matter injuries in the perinatal period are a growing cause of cerebral palsy yet no neuroprotective strategies exist to prevent the devastating motor and cognitive deficits that ensue. We demonstrate that the thrombin receptor (protease‐activated receptor 1, PAR1) exhibits peak expression levels in the spinal cord at term and is a critical regulator of the myelination continuum from initiation to the final levels achieved. Specifically, PAR1 gene deletion resulted in earlier onset of spinal cord myelination, including substantially more Olig2‐positive oligodendrocytes, more myelinated axons, and higher proteolipid protein (PLP) levels at birth. In vitro, the highest levels of PAR1 were observed in oligodendrocyte progenitor cells (OPCs), being reduced with differentiation. In parallel, the expression of PLP and myelin basic protein (MBP), in addition to Olig2, were all significantly higher in cultures of PAR1−/− oligodendroglia. Moreover, application of a small molecule inhibitor of PAR1 (SCH79797) to OPCs in vitro increased PLP and MBP expression. Enhancements in myelination associated with PAR1 genetic deletion were also observed in adulthood as evidenced by higher amounts of MBP and thickened myelin sheaths across large, medium, and small diameter axons. Enriched spinal cord myelination in PAR1−/− mice was coupled to increases in extracellular‐signal‐regulated kinase 1/2 and AKT signaling developmentally. Nocturnal ambulation and rearing activity were also elevated in PAR1−/− mice. These studies identify the thrombin receptor as a powerful extracellular regulatory switch that could be readily targeted to improve myelin production in the face of white matter injury and disease. GLIA 2015;63:846–859

Abstract Metastasis, the leading cause of cancer death, requires tumor cell intravasation, migration through the bloodstream, arrest within capillaries, and extravasation to invade distant tissues. Few mechanistic details have been reported thus far regarding the extravasation process or re-entry of circulating tumor cells at metastatic sites. Here, we show that neuropilin-2 (NRP-2), a multifunctional nonkinase receptor for semaphorins, vascular endothelial growth factor (VEGF), and other growth factors, expressed on cancer cells interacts with α5 integrin on endothelial cells to mediate vascular extravasation and metastasis in zebrafish and murine xenograft models of clear cell renal cell carcinoma (RCC) and pancreatic adenocarcinoma. In tissue from patients with RCC, NRP-2 expression is positively correlated with tumor grade and is highest in metastatic tumors. In a prospectively acquired cohort of patients with pancreatic cancer, high NRP-2 expression cosegregated with poor prognosis. Through biochemical approaches as well as Atomic Force Microscopy (AFM), we describe a unique mechanism through which NRP-2 expressed on cancer cells interacts with α5 integrin on endothelial cells to mediate vascular adhesion and extravasation. Taken together, our studies reveal a clinically significant role of NRP-2 in cancer cell extravasation and promotion of metastasis. Cancer Res; 73(14); 4579–90. ©2013 AACR.

AbstractBackground and AimsPositron emission tomography with computed tomography (PET/CT) has been used to detect metastasis in the diagnosis of esophageal adenocarcinoma (EAC). However, the utility of PET/CT to assess primary tumor for endoscopic resectability and prognosis in early EAC remains unclear. We conducted a retrospective study to determine the association of PET/CT findings with histopathological tumor invasion depth and survival outcomes.MethodsEAC patients who underwent PET/CT followed by endoscopic mucosal resection (EMR) were included. Pathology on EMR and survival outcomes from a prospectively maintained database was retrieved. Two radiologists independently reviewed the PET/CT using the following parameters: detection of malignancy, fluorodeoxyglucose (FDG) uptake intensity, FDG focality, FDG eccentricity, esophageal thickness, maximal standard uptake value (SUVmax), and SUVmax ratio (lesion/liver).ResultsThere were 72 eligible patients: 42 (58.3%) had T1a lesions, and 30 (41.7%) had ≥ T1b. Only SUVmax ratio was associated with tumor invasion depth (odds ratio = 2.77, 95% confidence interval 1.26–7.73, P = 0.0075). Using a cut‐off of 1.48, the sensitivity and specificity of SUVmax ratio for identification of T1a lesions were 43.3% and 80.9%, respectively. Adjusting the SUVmax ratio to 2.14, 16.7% (5/30) of ≥ T1b patients were identified without any false‐positive cases. Multivariate analysis showed SUVmax ratio, Charlson comorbidity index, and esophagectomy were independent predictors for survival.ConclusionsSUVmax ratio (lesion/liver) is more accurate in predicting endoscopic resectability and mortality for EAC than other PET/CT parameters and appears promising as a useful adjunct to the current diagnostic work‐up.

Abstract Microcephalin (MCPH1) is a BRCA1 COOH terminal (BRCT) domain containing protein involved in the cellular response to DNA damage that has been implicated in autosomal recessive primary microcephaly. MCPH1 is recruited to sites of DNA double-strand breaks by phosphorylated histone H2AX (γH2AX), but the mechanism by which MCPH1 contributes to the repair process remains to be determined. Here, we show that MCPH1 binds to BRCA2 and regulates the localization of BRCA2 and Rad51 at sites of DNA damage. The interaction occurs through the NH2 terminus of BRCA2 and the COOH terminal BRCT domains of MCPH1. Disruption of the interaction between MCPH1 and BRCA2 has no effect on the ability of BRCA2 to form a complex with Rad51 but is associated with substantially reduced levels of both BRCA2 and Rad51 at sites of DNA double-strand breaks. Uncoupling of MCPH1 from BRCA2 also interferes with Rad51-dependent and BRCA2-dependent homologous recombination repair activity. These results suggest that the role of MCPH1 in the DNA damage response is in part associated with the ability to localize BRCA2 to sites of DNA double-stand breaks. [Cancer Res 2009;69(13):5531–6]