Cancer research
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Tissue factor (TF), the cellular initiator of the protease blood coagulation cascade, has been shown to be expressed in a variety of solid tumors, particularly those of epithelial origin. However, the mechanisms that mediate TF expression in tumors, as well as the clinical implications of this expression, remain largely unknown. In this study, we examined the cytological distribution of TF in normal human breast tissue and breast carcinomas. ⋯ However, extracts from cells exposed to unconditioned media or CM pretreated with anti-TGF-beta antibodies did not. The induction of TF activity was also observed upon treatment of indicator cells with recombinant TGF-beta isoforms. Collectively, these data indicate that the recruitment and/or activation of TF-expressing stromal cells is an early event in progression to invasive breast cancer and likely occurs, in part, as a paracrine response to tumor cell-derived members of the TGF-beta family of growth factors.
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A murine antihuman B-cell monoclonal antibody, Lym-1, has shown considerable promise for the treatment of human malignant lymphomas. To enhance its clinical potential, a genetically engineered fusion protein consisting of a chimeric Lym-1 (chLym-1) and interleukin 2 (IL-2) was tested for mediating cytotoxicity, increasing vasopermeability, and enhancing antibody uptake in human malignant lymphomas. The chLym-1/IL-2 fusion protein, which was expressed initially in a baculovirus system and more recently in the glutamine synthetase gene amplification system, was shown to be processed and assembled into a normal immunoglobulin monomer with two IL-2 molecules per antibody. ⋯ Moreover, in antibody-dependent cellular cytotoxicity assays against Raji target cells, chLym-1/IL-2 had approximately 2-fold and 4-fold higher cytotoxicity than chLym-1 and murine Lym-1, respectively. Used as a pretreatment, chLym-1/IL-2 enhances the uptake of chLym-1 at the tumor site by altering the permeability of tumor vessels producing tumor:normal organ ratios of 420:1 for blood and 1708:1 for muscle at 3 days. The in vitro and in vivo activities of chLym-1/IL-2, therefore, suggest that this genetically engineered antibody fusion protein may represent a new immunotherapeutic reagent for the treatment of human malignant lymphomas.
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The disappointingly low survival rate observed in Ewing's sarcoma (ES)/peripheral neuroectodermal tumor (PNET) despite the adoption of aggressive multimodal treatments prompted us to study the existence of autocrine circuits to be used as innovative therapeutic targets. Of the several circuits analyzed, only the insulin-like growth factor receptor (IGF-IR)-mediated loop was found to be constantly present both in cell lines and clinical samples, suggesting a role for this autocrine circuit in the pathogenesis of ES/PNET. The in vitro inhibition of the IGF-IR-mediated circuit by the specific IGF-IR binding antibody alphaIR3 suppressed the growth of ES/PNET cells by decreasing the proliferative rate and increasing apoptosis. alphaIR3 also significantly inhibited the ability of ES/PNET cells to grow in soft agar and to migrate following a chemotactic stimulus. Inactivation of the IGF-IR signaling pathway may therefore be considered as an effective therapeutic modality for patients with ES/PNET.
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The antimitotic depsipeptide cryptophycin 1 (CP1) was compared to the antimitotic peptide dolastatin 10 (D10) as an antiproliferative agent and in its interactions with purified tubulin. The potent activity of CP1 as an inhibitor of cell growth was confirmed. The agent had an IC50 of 20 pM against L1210 murine leukemia cells versus 0.5 nM for D10. ⋯ The electron micrographic appearance of the D10-induced aggregate differed substantially from that of the CP1-induced aggregate. With D10, but not CP1, aggregate morphology was greatly altered in the presence of microtubule-associated proteins. Finally, although CP1 caused the formation of massive aggregates, as did D10, there was little turbidity change with the depsipeptide as opposed to the peptide.
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A 20-mer phosphorothioate oligodeoxynucleotide (ISIS 3521) designed to hybridize sequences in the 3'-untranslated region of human protein kinase C-alpha (PKC-alpha) mRNA has been shown to inhibit the expression of PKC-alpha in multiple human cell lines. In human bladder carcinoma (T-24) cells, inhibition of PKC-alpha was both concentration dependent and oligonucleotide sequence specific. ISIS 3521 had a IC50 of 50-100 nM for PKC-alpha mRNA reduction and was without effect on the expression of other members of the PKC family of genes (PKC-eta and zeta). ⋯ Three control phosphorothioate oligodeoxynucleotides not targeting human PKC-alpha were without effect on the growth of the tumors at doses as high as 6 mg/kg. Recovery of ISIS 3521 from tumor tissue and resolution by capillary gel electrophoresis revealed that 24 It after the final dose of oligodeoxynucleotide, intact, full-length 20-mer material was present as well as some apparent exonuclease degradation products (e.g., n-1 and n-2 mers). These studies demonstrate the in vivo antitumor effects of an antisense oligodeoxynucleotide targeting PKC-alpha and suggest that this compound may be of value as a chemotherapeutic agent in the treatment of human cancers.