Oncogene
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The most exciting advances in the tuberous sclerosis complex (TSC) field occurred in 1993 and 1997 with the cloning of the TSC2 and TSC1 genes, respectively, and in 2003 with the identification of Rheb as the target of tuberin's (TSC2) GTPase activating protein (GAP) domain. Rheb has a dual role: it activates mTOR and inactivates B-Raf. Activation of mTOR leads to increased protein synthesis through phosphorylation of p70S6K and 4E-BP1. ⋯ Despite these biochemical advances, exactly how mutations in TSC1 or TSC2 lead to the clinical manifestations of TSC is far from being understood. Two of the most unusual phenotypes in TSC are the apparent metastasis of benign cells carrying TSC1 and TSC2 mutations, resulting in pulmonary lymphangiomyomatosis, and the ability of cells with TSC1 or TSC2 mutations to differentiate into the separate components of renal angiomyolipomas (vessels, smooth muscle and fat). We will discuss how the TSC signaling pathways are affected by mutations in TSC1 or TSC2, focusing on how these mutations may lead to the renal and pulmonary manifestations of TSC.
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Alpha-difluoromethylornithine (DFMO) inhibits the proto-oncogene ornithine decarboxylase (ODC) and is known to induce cell cycle arrest. However, the effect of DFMO on human neuroblastoma (NB) cells and the exact mechanism of DFMO-induced cell death are largely unknown. Treatment with DFMO in combination with SAM486A, an S-adenosylmethionine decarboxylase (AdoMetDC) inhibitor, has been shown to enhance polyamine pool depletion. ⋯ Moreover, we observed a dramatic decrease in MYCN protein levels. Overexpression of MYCN induces an aggressive NB phenotype with malignant behavior. We show for the first time that DFMO and SAM486A induce G1 cell cycle arrest in NB cells through p27Kip1 and Rb hypophosphorylation.
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The clinical application of rituximab (chimeric mouse anti-human CD20 mAb, Rituxan, IDEC-C2B8), alone and/or combined with chemotherapy, has significantly ameliorated the treatment outcome of patients with relapsed and refractory low-grade or follicular non-Hodgkin's lymphoma (NHL). The exact in vivo mechanisms of action of rituximab are not fully understood, although antibody-dependent cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and apoptosis have been suggested. We have proposed that modifications of the cellular signaling pathways by rituximab may be crucial for its clinical response. ⋯ Resistant clones display different phenotypic, genetic and functional properties compared to wild-type cells. This review summarizes the data highlighting a novel role of rituximab as a signal-inducing antibody and as a chemosensitizing agent through negative regulation of major survival pathways. Studies presented herein also reveal several intracellular targets modified by rituximab, which can be exploited for therapeutic and prognostic purposes in the treatment of patients with rituximab- and drug-refractory NHL.
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A parity-induced mammary population, marked by beta-galactosidase expression conditionally activated through cre-lox recombinase originates in WAP-Cre/Rosa-lox-STOP-lox-LacZ (WAP-Cre/Rosa-LacZ) female mice during pregnancy, lactation and involution. During subsequent pregnancies, these parity-induced mammary epithelial cells (PI-MEC) proliferated to produce new secretory acini composed of secretory luminal cells and myoepithelium. In serial transplantation assays, PI-MEC were able to self-renew over several transplant generations and to contribute significantly to the resulting mammary outgrowths. ⋯ TGF-beta1 expression from the whey acidic protein promoter (WAP) in triply transgenic females did not prevent the appearance of PI-MEC after pregnancy despite the absence of full lactation or their ability to proliferate and produce progeny with diverse cellular fates in situ upon subsequent pregnancies. However, in transplants from triple transgenic parous females, the WAP-TGF-beta1-positive PI-MEC did not contribute to the newly recapitulated mammary outgrowths, suggesting that they were incapable of expansive cellular proliferation (self-renewal). This result is consistent with our earlier publication that WAP-TGF-beta1 expression in mammary epithelium induces premature stem cell senescence in mammary transplants and decreases mammary cancer risk in mouse mammary tumor virus (MMTV)-infected females even after multiple pregnancies.
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Large prospective studies show a significant association with obesity for several cancers, and the International Agency for Research on Cancer has classified the evidence of a causal link as 'sufficient' for cancers of the colon, female breast (postmenopausal), endometrium, kidney (renal cell), and esophagus (adenocarcinoma). These data, and the rising worldwide trend in obesity, suggest that overeating may be the largest avoidable cause of cancer in nonsmokers. Few obese people are successful in long-term weight reduction, and thus there is little direct evidence regarding the impact of weight reduction on cancer risk. If the correlation between obesity and cancer mortality is entirely causal, we estimate that overweight and obesity now account for one in seven of cancer deaths in men and one in five in women in the US.