UMLS:C0027651 - FACTA Search

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Query: UMLS:C0027651 (tumor)
685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The vacuolar-H(+)-ATPase, functionally expressed in cell membranes, is known to play a relevant role in intracellular pH regulatory mechanisms, because it is implicated in pumping protons into the extracellular environment or in sequestrating excess protons into acidic vacuolar compartments. Because tumor cells exist in a hypoxic microenvironment and produce acidic metabolites, this regulatory mechanism is recognized as a protective function. This study was designed to investigate the effect of NiK-12192 [4-(5,6-dichloro-1H-indol-2-yl)-3-ethoxy-N-(2,2,6,6-tetramethyl-piperidin-4-yl)-benzamide], an indole derivative identified as an effective inhibitor of vacuolar-H(+)-ATPase, on the cytotoxic activity of two camptothecins, i.e., topotecan and SN-38 (7-ethyl-10-hydroxycamptothecin, the active metabolite of irinotecan). The cellular studies performed in two pairs of human colon carcinoma cell lines, i.e., LoVo and LoVo/DX (overexpressing P-glycoprotein) and HT29 and HT29/Mit (overexpressing breast cancer resistant protein), indicated an enhancement of the antiproliferative effect of camptothecins by concomitant exposure to subtoxic concentrations of NiK-12192. Studies of subcellular distribution indicated that whereas topotecan alone localized mainly in mitochondria and endoplasmic compartment, the simultaneous presence of NiK-12192 caused a cytoplasmic redistribution. In HT29/Mit cells, NiK-12192 reverted the pattern of acidification induced by topotecan. The potentiation of topotecan efficacy by NiK-12192 was documented by an increased efficacy of the combination in both the HT29 tumor xenografts, being more evident in the topotecan-resistant HT29/Mit tumor. In conclusion, the vacuolar-H(+)-ATPase inhibitor NiK-12192 was able to potentiate the cytotoxic/antitumor effects of camptothecins, either in in vitro or in in vivo systems. Such findings support a potential interest for the use of vacuolar-H(+)-ATPase inhibitors in combination therapy to improve camptothecin efficacy.
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PMID:Effect of a novel vacuolar-H+-ATPase inhibitor on cell and tumor response to camptothecins. 1671 2

Poly(ADP-ribose) polymerase (PARP) inhibitors enhance the antitumor activity of the topoisomerase I inhibitor irinotecan (CPT-11), which is used to treat advanced colorectal carcinoma. Since PARP inhibitors sensitize tumor cells also to the methylating agent temozolomide (TMZ) and clinical trials are evaluating CPT-11 in combination with TMZ, we tested whether the PARP inhibitor GPI 15427 (10-(4-methyl-piperazin-1-ylmethyl)-2H-7-oxa-1,2-diaza-benzo[de]anthracen-3-one) increases the efficacy of CPT-11 + TMZ against colon cancer. Moreover, due to the ability of PARP inhibitors to avoid cell death consequent to PARP-1 overactivation, we evaluated whether oral administration of GPI 15427 provides protection from the dose-limiting intestinal toxicity of CPT-11. The results of colony formation assay indicated that GPI 15427 increased the antiproliferative effects (combination index <1) of TMZ + SN-38 (the active metabolite of CPT-11) against colon cancer cells. Accordingly, GPI 15427 (40 mg/kg/dayx5 days per os) in combination with TMZ (10 mg/kg/dayx5 days) + CPT-11 (4 mg/kg/dayx5 days) significantly reduced the growth of tumor xenografts. Oral administration of GPI 15427 (40 mg/kg/q2x3 days) prevented intestinal injury and diarrhea induced by CPT-11 (30 mg/kg/day x 3 days) reducing inflammation and PARP-1 overactivation, as evidenced by immunohistochemical staining of intestinal tissue with antipoly(ADP-ribose) antibody (Ab). In conclusion, the PARP inhibitor represents a novel strategy to enhance the antitumor efficacy and reduce toxicity of chemotherapy in colon cancer.
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PMID:Inhibition of poly(ADP-ribose) polymerase prevents irinotecan-induced intestinal damage and enhances irinotecan/temozolomide efficacy against colon carcinoma. 1680 34

To provide some insight into molecular mechanisms of 5 fluorouracil (5-FU) clinical resistance in colorectal cancer, we hypothesized that different in vitro exposure schedules of human colorectal cancer cell lines mimicking clinical infusion or bolus regimens could lead to differential gene expression. Resistant HCT-8 colon cancer cell lines (HCT-8/FUI/15R and HCT-8/FUB/2R) were selected from parental sensitive HCT-8 cells by long-term and short-term exposure schedules, respectively. Expression levels of the 437 genes evaluated by the Atlas Select cDNA Expression Human Tumor Array were not substantially different between HCT-8/FUB/2R and HCT-8 cell lines except for three genes downregulated in the resistant subline. Several genes were differentially expressed in HCT-8/FUI/15R cells compared to the parental cell line: 43 genes, including three chemoresistance-related genes, were upregulated, and three genes were downregulated. HCT-8/FUB/2R cells were substantially more resistant to 5-FU in comparison to HCT-8/FUI/15R cells after both 4- and 72-h exposures. No substantial differences were observed among resistant and parental cells in sensitivity to SN-38, the active metabolite of irinotecan, and oxaliplatin. Analysis of the mRNA levels of thymidylate synthase, thymidine phosphorylase, and bcl-2 genes evaluated by reverse transcription and real time PCR (RT-PCR) assay showed comparable results in resistant sublines and sensitive parental cells, whereas expression of the dihydropyrimidine dehydrogenase gene was markedly increased in both resistant cell lines compared to parental cells.
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PMID:Molecular characterization of established human colon carcinoma cell lines (HCT-8) made resistant to 5-fluorouracil by different selection schedules. 1692 15

Carboxylesterases are ubiquitous proteins responsible for the detoxification of xenobiotics. However, these enzymes also activate prodrugs, such as the anticancer agents capecitabine and CPT-11. As a consequence, overexpression of carboxylesterases within tumor cells sensitizes these cells to CPT-11. We have recently identified two classes of carboxylesterase inhibitors based on either a benzil (diphenylethane-1,2-dione) or a benzene sulfonamide scaffold and showed that these compounds inhibit carboxylesterases with Kis in the low nanomolar range. Because both classes of inhibitors show reversible enzyme inhibition, conventional in vitro biochemical assays would not accurately reflect the in situ levels of carboxylesterase activity or inhibition. Therefore, we have developed a novel assay for the determination of intracellular carboxylesterase activity using 4-methylumbelliferone as a substrate. These studies show that benzil and a dimethylbenzil analogue efficiently enter cells and inhibit human intestinal carboxylesterase and rabbit liver carboxylesterase intracellularly. This inhibition results in reduced cytotoxicity to CPT-11 due to the lack of carboxylesterase-mediated conversion of the prodrug to SN-38. These results suggest that intracellular modulation of carboxylesterase activity with benzil or its analogues may be applied to minimize the toxicity of normal cells to CPT-11.
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PMID:Intracellular inhibition of carboxylesterases by benzil: modulation of CPT-11 cytotoxicity. 1698 62

7-Ethyl-10-hydroxy-camptothecin (SN-38), a biological active metabolite of irinotecan hydrochloride (CPT-11), has potent antitumor activity but has not been used clinically because it is a water-insoluble drug. For delivery by i.v. injection, we have successfully developed NK012, a SN-38-releasing nanodevice. The purpose of this study is to investigate the pharmacologic character of NK012 as an anticancer agent, especially in a vascular endothelial growth factor (VEGF)-secreting tumor model. The particle size of NK012 was approximately 20 nm with a narrow size distribution. NK012 exhibited a much higher cytotoxic effect against lung and colon cancer cell lines as compared with CPT-11. NK012 showed significantly potent antitumor activity against a human colorectal cancer HT-29 xenograft as compared with CPT-11. Enhanced and prolonged distribution of free SN-38 in the tumor was observed after the injection of NK012. NK012 also had significant antitumor activity against bulky SBC-3/Neo (1,533.1 +/- 1,204.7 mm(3)) and SBC-3/VEGF tumors (1,620.7 +/- 834.0 mm(3)) compared with CPT-11. Furthermore, NK012 eradicated bulky SBC-3/VEGF tumors in all mice but did not eradicate SBC-3/Neo tumors. In the drug distribution analysis, an increased accumulation of SN-38 in SBC-3/VEGF tumors was observed as compared with that in SBC-3/Neo tumors. NK012 markedly enhanced the antitumor activity of SN-38, especially in highly VEGF-secreting tumors, and could be a promising SN-38-based formulation.
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PMID:Novel SN-38-incorporating polymeric micelles, NK012, eradicate vascular endothelial growth factor-secreting bulky tumors. 1704 68

Neural stem cells and progenitor cells migrate selectively to tumor loci in vivo. We exploited the tumor-tropic properties of HB1.F3.C1 cells, an immortalized cell line derived from human fetal telencephalon, to deliver the cDNA encoding a secreted form of rabbit carboxylesterase (rCE) to disseminated neuroblastoma tumors in mice. This enzyme activates the prodrug CPT-11 more efficiently than do human enzymes. Mice bearing multiple tumors were treated with rCE-expressing HB1.F3.C1 cells and schedules of administration of CPT-11 that produced levels of active drug (SN-38) tolerated by patients. Both HB1.F3.C1 cells and CPT-11 were given i.v. None of the untreated mice and 30% of mice that received only CPT-11 survived long term. In contrast, 90% of mice treated with rCE-expressing HB1.F3.C1 cells and 15 mg/kg CPT-11 survived for 1 year without detectable tumors. Plasma carboxylesterase activity and SN-38 levels in mice receiving both rCE-expressing HB1.F3.C1 cells (HB1.F3.C1/AdCMVrCE) and CPT-11 were comparable with those in mice receiving CPT-11 only. These data support the hypothesis that the antitumor effect of the described neural stem/progenitor cell-directed enzyme prodrug therapy (NDEPT) is mediated by production of high concentrations of active drug selectively at tumor sites, thereby maximizing the antitumor effect of CPT-11. NDEPT approaches merit further investigation as effective, targeted therapy for metastatic tumors. We propose that the described approach may have greatest use for eradicating minimum residual disease.
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PMID:Tumor-targeted enzyme/prodrug therapy mediates long-term disease-free survival of mice bearing disseminated neuroblastoma. 1721 Jun 79

Irinotecan is one of the effective anticancer agents for small-cell lung cancer (SCLC) and 7-ethyl-10-hydroxy-campthothecin (SN-38) is an active metabolite of irinotecan. Gefitinib and imatinib are tyrosine kinase inhibitors which have clinical activities in several malignancies and they are also potent inhibitors of breast cancer resistance protein (BCRP) transporter, which confers the resistance of topoisomerase I inhibitors including SN-38 and topotecan. The cytotoxicity of SN-38, gefitinib and imatinib for the SN-38-resistant cells (SBC-3/SN-38) from human SCLC cells, SBC-3, was evaluated using AlamarBlue assay. The drug concentration required to inhibit the growth of tumor cells by 50% (IC50) for 96-h exposure was used to evaluate the cytotoxicity. BCRP expression was determined by Western blotting and immunofluorescence staining. Intracellular topotecan accumulation was evaluated by flow cytometry. No differences were observed in the IC50 values (mean +/- SD) of the tyrosine kinase inhibitors between the SBC-3 cells and the SBC-3/SN-38 cells: 15+/-1.6 and 12+/-2.8 microM of gefitinib, respectively; 15+/-0.51 and 14+/-3.9 microM of imatinib, respectively. The SBC-3/SN-38 was 9.5-fold more resistant to SN-38 than the parental SBC-3. The SBC-3/SN-38 restored sensitivity to SN-38 when combined with 8 microM gefitinib or 8 microM imatinib, even though the IC50 values of SN-38 combined with gefitinib or imatinib in the SBC-3 cells did not change. BCRP was equally overexpressed in the SBC-3/SN-38 with and without gefitinib or imatinib. In addition, the BCRP expression on the SBC-3/SN-38 cell membrane with and without gefitinib seemed to be equal. Gefitinib increased intracellular accumulation of topotecan in the SBC-3/SN-38 cells. Gefitinib or imatinib reversed SN-38-resistance in these SCLC cells, possibly due to intracellular accumulation of SN-38 without any change in BCRP quantity. Irinotecan with gefitinib or imatinib might be effective for SCLC refractory to irinotecan.
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PMID:Combination of SN-38 with gefitinib or imatinib overcomes SN-38-resistant small-cell lung cancer cells. 1739 33

CPT-11 [7-ethyl-10-[4-(1-piperidino)-1-piperidino] carbonyloxycamptothecin or Irinotecan] is a carbamate prodrug that is activated in vivo by carboxylesterase (CES)-2 to SN-38 (7-ethyl-10-hydroxycamptothecin), a potent topoisomerase I inhibitor. There is high interindividual variation when CPT-11 is used in the treatment of colorectal cancer. Several splice variants of CES2 are reported in the expressed sequence tag database. Real-time polymerase chain reaction was used to determine the abundance of the CES2 and splice variant of human carboxylesterase 2 (CES2Delta(458-473)) transcripts in 10 paired samples of human tumor and normal colon tissue. The results showed that the CES2Delta(458-473) transcript accounts for an average of 6% of total CES2 transcripts in colon tissue, and there is large interindividual variation in CES2 expression in both tumor and normal colon samples. The carboxylesterase activity of the colon samples was determined by 4-methylumbelliferyl acetate hydrolysis assays and nondenaturing polyacrylamide gel electrophoresis followed by activity staining. Significant, positive correlations were found between CES2 expression levels and both measures of carboxylesterase activity. We cloned and expressed the CES2Delta(458-473) protein in Sf9 insect cells. The purification profiles and preliminary characterization of the CES2Delta(458-473) protein indicated that the expressed protein is folded and glycosylated like CES2. However, in vitro assays show that the CES2Delta(458-473) protein lacks 4-methylumbelliferyl acetate and irinotecan hydrolase activities. In conclusion, we found that the CES2Delta(458-473) protein is an inactive splice variant of CES2 and that its transcript is spliced at a relatively constant rate in tumor and normal colon tissue.
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PMID:Expression and characterization of a human carboxylesterase 2 splice variant. 1763 9

The pharmacokinetics of irinotecan and its metabolites has been widely studied. No pharmacokinetic data, however, are available in haemodialysis patients. We report two clinical cases of severe toxicity, one of which was fatal, in two haemodialysis patients treated with irinotecan for a metastatic colorectal cancer. In case no. 1, M.S., aged 71 years, was treated with first-line FOLFIRI chemotherapy (irinotecan 180 mg/m) for local recurrence with liver metastases of a colon cancer treated with an LV5FU2 protocol as an adjuvant therapy 3 years previously. After the first cycle of irinotecan, the patient presented grade 4 diarrhoea on day 9, then a febrile grade 4 neutropenia on day 14 leading to his death on day 18. In case no. 2, M.D., aged 57 years, was treated successively by radiochemotherapy with an LV5FU2 regimen, then with four cycles of FOLFIRI (irinotecan at 125 mg/m) and finally with the cetuximab/irinotecan combination using the conventional dosage. Febrile neutropenia was observed on day 10 of the first irinotecan infusion with a dose of 180 mg/m and on day 8 of the second infusion with a lower dose of 120 mg/m. The patient's general condition progressively deteriorated with the advancement of the neoplastic disease, which led ultimately to his death. In this patient, plasma concentrations of irinotecan and its metabolite, SN-38, were measured during the course of the first FOLFIRI cycle on day 2 and on day 4, before and after dialysis sessions. The observed results suggest that, although irinotecan is partially dialysable, SN-38 is not. In conclusion, dose recommendations have to be defined in haemodialysis patients with renal dysfunction owing to the potential toxicity of irinotecan in these patients. Special care should be taken in liver metastasis cases owing to the nondialysability of SN-38.
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PMID:Irinotecan-based chemotherapy in a metastatic colorectal cancer patient under haemodialysis for chronic renal dysfunction: two cases considered. 1766 6

To investigate whether the OATP1B1 polymorphisms affect irinotecan-pharmacokinetics and subsequent toxicity and tumor response of patients with advanced NSCLC. A total of 81 Korean NSCLC patients enrolled in a phase II study of irinotecan and cisplatin chemotherapy were genotyped for OATP1B1 -11187G>A, 388A>G and 521T>C variants. The 521TC or CC and -11187AA genotypes were associated with higher AUC(SN-38) (p=0.016 and 0.030, respectively). When haplotypes were assigned, patients with *15 haplotype showed significantly higher AUC(SN-38) than *1a or *1b haplotypes (p=0.006). Grade 4 neutropenia was associated with the 521TC or CC genotypes, whereas, grade 3 diarrhea was associated with 388GG genotype (p=0.046). Of the 81 patients enrolled, 77 were assessable for response and 36 (47%) patients achieved partial responses (PR). However, no statistical significance was observed between genotype and response. These findings suggest that OATP1B1 variants are involved in SN-38 disposition and highly predictive for severe toxicity of NSCLC patients treated with irinotecan-based chemotherapy.
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PMID:Influence of the organic anion-transporting polypeptide 1B1 (OATP1B1) polymorphisms on irinotecan-pharmacokinetics and clinical outcome of patients with advanced non-small cell lung cancer. 1776 2

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