PubMed · 7177450
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A Valentino. 1982-11-15. [Acute postoperative necrotizing enteritis].. https://pubmed.ncbi.nlm.nih.gov/7177450/
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The G12 subfamily of heterotrimeric G proteins, comprised of the alpha-subunits Galpha12 and Galpha13, has been implicated as a signaling component in cellular processes ranging from cytoskeletal changes to cell growth and oncogenesis. In an attempt to elucidate specific roles of this subfamily in cell regulation, we sought to identify molecular targets of Galpha12. Here we show a specific interaction between the G12 subfamily and the cytoplasmic tails of several members of the cadherin family of cell-surface adhesion proteins. Galpha12 or Galpha13 binding causes dissociation of the transcriptional activator beta-catenin from cadherins. Furthermore, in cells lacking the adenomatous polyposis coli protein required for beta-catenin degradation, expression of mutationally activated Galpha12 or Galpha13 causes an increase in beta-catenin-mediated transcriptional activation. These findings provide a potential molecular mechanism for the previously reported cellular transforming ability of the G12 subfamily and reveal a link between heterotrimeric G proteins and cellular processes controlling growth and differentiation.
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The immunomodulator ammonium trichloro(dioxyethylene-0-0')tellurate (AS101) has been shown to possess antitumoral properties in several murine models. In the present study, we demonstrate a synergistic in vivo antitumor effect of AS101 and Taxol against early stage Madison 109 lung adenocarcinoma. Treatment with optimal doses of Taxol (25 and 17 mg/kg) and AS101 (0.5 mg/kg) resulted in 66.6 and 43.3% cures. We propose that the antitumor effect is the result of both a direct and indirect effect of the drugs on tumor cells. AS101 and Taxol directly inhibited clonogenicity of M109 cells in a synergistic dose-dependent manner. Exposure of M109 cells to clinically achievable concentrations of Taxol and AS101 produced a synergistic internucleosomal DNA fragmentation associated with programmed cell death. We suggest that AS101 renders tumor cells more susceptible to chemotherapy in general and to Taxol in particular, partly by increasing the wild-type p53 protein expression that is required for efficient execution of the death program. Moreover, we demonstrate a synergistic effect of AS101 and Taxol in increasing the tumoricidal activity of macrophages. This activity is produced by nitric oxide secretion. The synergistic antitumoral effects of AS101 and Taxol were partly ablated both in vitro and in vivo by inhibition of nitric oxide synthase. These findings indicate that AS101 in combination with Taxol may be a promising antitumor drug, and illustrate the mechanism of action of both drugs when acting synergistically. Phase II clinical trials have been initiated using AS101 in combination with Taxol.