Cancer research
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Fas (APO-1/CD95) is a transmembrane protein of the tumor necrosis factor (TNF)/nerve growth factor receptor superfamily that induces apoptosis in susceptible normal and neoplastic cells upon cross-linking by its ligand (FasL). TNF-related apoptosis-inducing ligand (TRAIL) is a more recently identified member of the TNF superfamily that has been shown to selectively kill neoplastic cells by engaging two cell-surface receptors, DR4 and DR5. Two additional TRAIL receptors (DcR1 and DcR2) do not transmit an apoptotic signal and have been proposed to confer protection from TRAIL-induced apoptosis. ⋯ Resistance to TRAIL did not correlate with DcR1 or DcR2 protein expression and was overcome by protein synthesis inhibition in 50% of the resistant cell lines. One medullary carcinoma cell line was resistant to Fas-and TRAIL-induced apoptosis, even in the presence of cycloheximide, and to transfection of constitutively active caspase-8, suggesting a different regulation of the apoptotic pathway. Our observations indicate that TRAIL effectively kills carcinomas that originate from the follicular epithelium of the thyroid gland, by inducing caspase-mediated apoptosis, and may provide a potentially potent therapeutic reagent against thyroid cancer.
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The basis for current clinical trials in the treatment of colorectal cancer with the combination of irinotecan (CPT-11) and 5-fluorouracil (FUra) with or without leucovorin (LV) is their proven activity as single agents, their different mechanisms of action, and lack of CPT-11 cross-resistance to previous FUra/LV treatment. The role of drug dose and administration sequence in this combination was studied in vivo using a rat colon tumor model (Ward colon carcinoma); we administered CPT-11 and FUra by i.v. push once a week for four consecutive weeks (weekly x 4), a clinically relevant schedule. The maximum tolerated doses (MTDs) of CPT-11 and FUra administered as single agents were 100 mg/kg/week for both agents. ⋯ With the sequential combination of CPT-11 followed 24 h later by FUra (sequence III), the high complete tumor regression rate (cure) could be maintained, even when the dose of CPT-11 was reduced to 12.5% of the MTD as long as the doses of FUra was kept at 50 -75 % of the MTD. The data demonstrate that the antitumor activity and toxicity of combining CPT-11 with FUra is highly sequence dependent and that a sequence of CPT-11 preceding FUra is superior with a significant increase in the therapeutic index over the other sequences tested. In addition, the data also demonstrate that toxicity associated with high dose of CPT-11 can be eliminated without loss of the antitumor efficacy by reducing the dose of CPT-11 to at least 50% of its MTD, whereas the dose of FUra is kept at 50-75 % of its MTD.
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Plasma cell neoplasia in humans generally occurs as multiple myeloma, an incurable form of cancer. Tumors with marked similarity can be induced in mice by a variety of agents, including chemicals, silicone, and oncogene-containing retroviruses, suggesting the use of murine tumors as an informative model to study plasma cell disease. Herein, we have focused on the role of insulin-like growth factor I receptor (IGF-IR) signaling in the development of plasma cell disease. ⋯ Biological relevance was demonstrated in that plasma cell lines with up-regulated IGF-IR expression levels exhibited mitogenic responses to IGF-I. More importantly, expression of a dominant-negative mutant of IGF-IR in these lines strongly suppressed tumorigenesis in vivo. Taken together, these results demonstrate that up-regulation and activation of IGF-IR and the downstream signaling pathway involving insulin receptor substrate 2, phosphatidylinositol 3'-kinase, and p70S6K may play an important role in the development of a broad spectrum of plasma cell tumors.
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Ligation of CD40 is essential for primary B-cell activation and expansion and yet has suppressive or apoptotic effects on some CD40-expressing neoplasia. SGN-14 is a monoclonal antibody that binds to the human CD40 receptor. Here we report that SGN-14, in the presence of interleukin 4, provided a modest level of stimulation of peripheral blood B cells, as measured by proliferation. ⋯ In vivo, SGN-14 showed significant antitumor activity in treating human B-cell lymphoma and multiple myeloma xenografted severe combined immunodeficient mice. Antitumor activity was not diminished by blunting murine natural killer activity, suggesting that CD40 ligation contributes to the antitumor efficacy of SGN-14. On the basis of these activities, SGN-14 is being pursued for therapeutic use in treating patients with CD40-expressing hematological malignancies.
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The effectiveness of chemotherapy targeted to somatostatin (SST) receptors based on cytotoxic SST analogue AN-238, consisting of 2-pyrrolinodoxorubicin (AN-201) linked to SST carrier octapeptide, was investigated in human renal cell carcinomas (RCCs). SST receptors, which showed high-affinity binding for AN-238, were found in the SW-839 RCC line with sst2A subtype and in the 786-0 RCC line, which expressed the sst5 subtype. CAKI-1 RCC, which does not express sst2A or sst5, was used as a negative control for testing the specificity of SST receptor targeting. ⋯ Lung metastases were found in 83% of controls and 50% of AN-201 treated animals, but none occurred in mice treated with AN-238. This study demonstrates that targeted cytotoxic SST analogue AN-238 provides an effective therapy for chemoresistant neoplasms such as RCC. Because most clinical RCCs express SST receptors, this treatment modality might be beneficial to patients with metastatic disease.