The antitumor effects of the camptothecin (CPT) derivative CPT-11, 7-ethyl-10-[4-(1-piperidino)-1-piperidino]-carbonyloxycamptothecin , were tested on human tumor xenografts in nude mice. CPT-11 showed antitumor activity higher than that of Adriamycin, 5-fluorouracil, or futraful, with little or no reduction of body weight being observed in the mice. The growth of colon adenocarcinoma Co-4 was significantly inhibited after a single i.v. injection of CPT-11 at 25, 50, or 100 mg/kg. The single i.v. injection was also significantly effective against mammary carcinoma MX-1 and gastric adenocarcinoma St-15. All of the mice bearing MX-1 tumors were cured by the administration of CPT-11 every 4 days for a total of three treatments at a total dose of 200 mg/kg given i.v. or of 400 mg/kg given p.o. Three i.v. or oral treatments were also effective against Co-4, St-15, gastric adenocarcinoma SC-6, and squamous-cell lung carcinoma QG-56. To achieve the same efficacy attained by i.v. injection, however, oral doses 2-4 times higher than the i.v. doses were required. When the total dose was fixed at 100 mg/kg, a triple i.v. injection was most effective, followed by a single i.v. injection and, finally daily p.o. administration for 10 days. Although SN-38 (7-ethyl-10-hydroxycamptothecin), a metabolite of CPT-11, showed much stronger cytotoxic activity in vitro than did CPT-11, its antitumor effects were similar, if not inferior, to those of CPT-11 in vivo at the same dose level. CPT-11 was converted into SN-38 by human tumors, but the sensitivity of these tumors to CPT-11 in vivo was independent of their ability to produce SN-38. These results suggest that CPT-11 may be clinically effective, depending on the schedule of administration, but that its effectiveness is not related to the ability of the tumor to produce SN-38.

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Hyperglycemia is a major risk factor for atherosclerotic disease. Hepatic scavenger receptor class B type I (SR-BI) binds HDL particles that mediate reverse cholesterol transport and thus lowers the risk of atherosclerosis. Here we examined glucose regulation of SR-BI gene expression in both HepG2 cells and whole animals. Results showed that hepatic SR-BI mRNA, protein, and uptake of cholesterol from HDL were halved following 48 h of exposure to 22.4 vs. 5.6 mM glucose. As in the case of the cell culture model, hepatic expression of SR-BI was lower in diabetic rats than in euglycemic rats. Transcriptional activity of the human SR-BI promoter paralleled endogenous expression of the gene, and this activity was dependent upon the dose of glucose. Next, we used inhibitors of select signal transduction pathways to demonstrate that glucose suppression of SR-BI was sensitive to the p38 MAPK inhibitor. Expression of a constitutively active p38 MAPK inhibited SR-BI promoter activity in the presence or absence of glucose. A dominant-negative p38 MAPK abolished the inhibitory effect of glucose on promoter activity. Deletional analysis located a 50-bp fragment of the promoter that mediated the effects of glucose. Within this DNA fragment there were several specificity protein-1 (Sp1) binding sites, and cellular knockdown of Sp1 abrogated its suppression by glucose. Together, these results indicate that the glucose suppression of SR-B1 expression is partially mediated by the activation of the p38 MAPK-Sp1 pathway and raise the possibility that the inhibition of hepatic SR-BI expression under high-glucose conditions provides a mechanism for accelerated atherosclerosis in diabetics.

BackgroundGlioblastoma multiforme (GBM) is the most malignant intracranial tumour that develops in both adults and children. Microarray gene analyses have confirmed that the human YKL-40 gene is one of the most over-expressed genes in these tumours but not in normal brain tissue. Clinical studies have shown that serum YKL-40 levels are positively correlated with tumour burden in addition to being an independent prognostic factor of a short relapse-free interval as well as short overall survival in patients with various cancers. Our previous study revealed that YKL-40 was closely correlated with the pathological grades of human primary astrocytomas and played a crucial role in glioma cell proliferation. Hence, YKL-40 could be an attractive target in the design of anti-cancer therapies.MethodsCell viability and invasion assays were performed to detect the cell proliferation and invasive ability of U87 cells induced by resveratrol (3, 5, 4'-trihydroxystilbene; Res) or YKL-40 small-interfering RNAs (siRNAs). In addition, the luciferase assay, real-time RT-PCR, western blotting, and ELISA were used to measure YKL-40 promoter activity, mRNA, and protein expression, respectively. The expressions of phosphor-ERK1/2 and ERK1/2 were determined by western blotting.ResultsRes inhibited U87 cell proliferation and invasion in vitro and repressed YKL-40 in U87 cells by decreasing the activity of its promoter and reducing mRNA transcription and protein expression in vitro. YKL-40 siRNA treatment also impaired the invasiveness of U87 cells. When U87 cells were cultured with 20 μM PD98059 (an ERK1/2 inhibitor) alone, with 20 μM PD98059 and 100 μM Res, or with 100 μM Res alone for 48 h, YKL-40 protein expression decreased most significantly in the Res-treated group. PD98059 partially reversed the decrease of YKL-40 protein expression induced by Res. Furthermore, phosphor-ERK1/2 expression was reduced by Res treatment in a time-dependent manner.ConclusionsWe demonstrated for the first time that Res represses YKL-40 expression in vitro; in addition, the ERK1/2 pathway is involved in this repression. This finding could extend the prospective use of Res in glioma research and enlarge the armamentarium for treating gliomas.

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