p53 mutations in human aggressive and nonaggressive basal and squamous cell carcinomas.

PURPOSE: The purpose is to investigate whether aggressive basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) differ from nonaggressive BCC and SCC with respect to the p53 mutation spectrum and whether specific mutations can serve as prognostic indicators of tumor aggressiveness. EXPERIMENTAL DESIGN: We analyzed 342 tissues from patients with aggressive and nonaggressive BCCs and SCCs for p53 mutations by single-strand conformation polymorphism and nucleotide sequencing. RESULTS: p53 mutations were detected in 33 of 50 aggressive BCCs (66%), 37 of 98 nonaggressive BCCs (38%), 28 of 80 aggressive SCCs (35%), 28 of 56 nonaggressive SCCs (50%), and 3 of 29 samples of sun-exposed skin (10%). About 71% of the p53 mutations detected in aggressive and nonaggressive BCCs and SCCs were UV signature mutations. The frequency of CC to TT mutations in aggressive (36%) and nonaggressive SCCs (39%) was 2-fold higher than in aggressive (18%) and nonaggressive (14%) BCCs. In contrast, aggressive BCCs had a higher frequency (24%) of transversions than nonaggressive BCCs (8%) and aggressive (14%) and nonaggressive (11%) SCCs did. CONCLUSIONS: Our results indicate that UV radiation is responsible for the induction of p53 mutations and perhaps for the initiation of both aggressive and nonaggressive BCCs and SCCs. Although some differences in p53 mutation frequency, types of mutation, and hot spots were seen between aggressive and nonaggressive BCCs and SCCs, these factors do not constitute as clear-cut diagnostic or prognostic indicators of tumor aggressiveness. Tumor aggressiveness may be attributable to other genetic changes or events that occur during tumor progression.     

Ca2+-dependent desensitization of AMPA receptors

The effect of changes in the external concentrations (0.4-10 mM) of Ca2+ ions on AMPA receptors (AMPARs) of different subunit composition was studied on freshly isolated rat brain neurones. Ca2+ produces rapid and reversible voltage-independent inhibition of AMPARs. Ca2+-permeable and Ca2+-impermeable AMPARs are equally sensitive to external Ca2+ suggesting that the effect is not addressed to the ion channel. The inhibition of responses evoked by AMPA is significantly larger than those evoked by kainate or glutamate. Cyclothiazide and aniracetam, which are known to prevent AMPAR desensitization, both greatly diminish inhibition of AMPARs by Ca2+. Cyclothiazide is more potent than aniracetam in both preventing of AMPAR desensitization and protecting against the Ca2+ inhibitory effect on hippocampal pyramidal cells. On giant cholinergic interneurones of striatum, aniracetam but not cyclothiazide significantly prevents inhibition by Ca2+. This agrees with available data on relative abundance of flip and flop splice variants in these cell types. The results suggest that Ca2+ may allosterically increase AMPA receptor desensitization independently on subunit composition and splice variants.     

Primary culture of mouse embryonic spinal cord neurons: cell composition and suitability for axonal regeneration studies

Objective: Primary culture is an effective experimental model to study molecular mechanisms that drive axonal regeneration after central nervous system injury. However, the culture of spinal cord (SC) cells remains poorly characterized. Here, we have analyzed the cell composition of a primary SC culture during its maturation.

Methods: Primary cell culture was prepared from mouse embryo spinal cords. After 2, 7, and 14 days of cultivation, the cells were fixed and stained with antibodies against β3-tubulin, nestin, crmp1, SMI-32, DCC or GFAP. We counted percentage of cells positive for the mentioned markers and measured the length of cell processes.

Results: We found that β3-tubulin and nestin were both expressed at day 2 of culture in vitro. Surprisingly (given the use of differentiation-supporting culture medium), the number of nestin+ cells has significantly increased during the first week of cultivation. The GFAP+ cells appeared only at the seventh day in vitro, and their fraction increased during the following cultivation. At 14 day in vitro, SC culture contained cells that expressed the markers typical of commissural and motor neurons. At this age, the neurons had the ability to repair injured neurites after mechanical damage.

Conclusion: Primary culture of SC cells is a dynamically developing cell population that contains all main types of SC cells and is capable of self-repair. Therefore, the culture of mouse embryonic SC cells represents an adequate experimental model for studying cellular and molecular processes taking place in SC neurons after axonal damage in the absence of external inhibitors.     

Combined vascular endothelial growth factor receptor/epidermal growth factor receptor blockade with chemotherapy for treatment of local, uterine, and metastatic soft tissue sarcoma

PURPOSE: Soft tissue sarcoma (STS) is a rare heterogeneous malignancy. Overall survival has been stagnant for decades, primarily because systemic therapies are ineffective versus metastases, the leading cause of STS lethality. Consequently, we examined whether tyrosine kinase receptors active in STS growth signaling might be blockable and whether multireceptor blockade might synergize with low-dose STS chemotherapy by therapeutically affecting STS cells and their associated microenvironment. EXPERIMENTAL DESIGN: Vandetanib (AstraZenca), a tyrosine kinase inhibitor of vascular endothelial growth factor receptor 2 and epidermal growth factor receptor, was evaluated alone and with chemotherapy in vitro and in vivo in three human STS nude mouse xenograft models of different STS locations (muscle, uterus, lung), stages (primary, metastatic), and subtypes (leiomyosarcoma, fibrosarcoma, uterine sarcoma: luciferase-expressing MES-SA human uterine sarcoma cells surgically implanted into uterine muscularis with bioluminescence tumor growth assessment; developed by us). RESULTS: In vitro, human STS cells were sensitive to vandetanib. Vandetanib alone and with chemotherapy statistically significantly inhibited leiomyosarcoma local growth and fibrosarcoma lung metastasis. Direct injection of MES-SA into nude mice uterine muscularis resulted in high tumor take (88%), whereas s.c. injection resulted in no growth, suggesting microenvironmental tumor growth modulation. Vandetanib alone and with chemotherapy statistically significantly inhibited uterine sarcoma growth. In all models, vandetanib induced increased apoptosis, decreased tumor cell proliferation, and decreased angiogenesis. CONCLUSIONS: Vandetanib has antitumor effects against human STS subtypes in vitro and in vivo, where it also affects the tumor-associated microenvironment. Given the urgent need for better systemic approaches to STS, clinical trials evaluating vandetanib, perhaps with low-dose chemotherapy, seem warranted.     

Transepithelial paracellular leakiness induced by chronic phorbol ester exposure correlates with polyp-like foci and redistribution of protein kinase C-alpha

Although exposure of LLC-PK1 epithelial cell sheets to phorbol esters (TPA) causes a near immediate and total decrease of transepithelial electrical resistance (TER), continuation of exposure for 3 to 4 days results in a tachyphylactic response as TER begins to return to control levels. Recovery of TER is maximal by 5 to 6 days, but reaches only 70 to 80% of control level. A reciprocal change in the transepithelial flux of D-mannitol indicates that the TER decrease is indicative of an increase in tight junction permeability. Exposure of cell sheets to TPA for several days also results in the appearance of multilayered polyp- like foci (PLFs) across the otherwise one cell layer thick cell sheets. The pattern of penetration of the electron dense dye, ruthenium red, from the apical surface, across the tight junction and into the lateral intercellular space indicates that the tight junctions of the cell sheet become uniformly leaky after acute exposure to TPA. However, when exposure is continued for several days, only the junctions of cells in the PLFs manifest leakiness. The decrease in TER following acute TPA exposure correlates with the translocation of protein kinase C-alpha (PKC alpha) into a membrane-associated compartment. With exposure of several days, only a trace of PKC alpha is visible by Western immunoblot, and this is in the membrane-associated compartment. Immunofluorescent microscopy indicates that the trace of PKC alpha seen in the Western immunoblots is ascribable distinctly to cells of the PLFs. Monolayer areas between PLFs show no discernible immunofluorescent signal. The data therefore indicate that tight junction barrier function may be restored in certain areas by the down regulation of PKC alpha from the membrane-associated compartment. Failure to down regulate may result in the paracellular leakiness and abnormal cell architecture of the PLFs. Possible implications of this model for in vivo epithelial tumor promotion are discussed.      

Regulation of synaptic plasticity in a schizophrenia model

The pathology of schizophrenia is characterized by increased hippocampal activity at baseline and during auditory hallucinations. Animal-model studies in which the flow of activity to the hippocampus is increased through decreased amygdalar GABAergic inhibition have shown alterations of hippocampal circuitry similar to schizophrenia, but the functional importance of this phenomenon remains unclear. We provide evidence of decreased hippocampal feed-forward and tonic GABA-mediated inhibition in this animal model, complementing increased hippocampal activity seen in neuroimaging and postmortem studies. We demonstrate that GABA dysfunction increases long-term potentiation through activation of the cholinergic system, offering a new mechanism for pharmacological strategies of this disorder.