Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Despite improvement in the treatment of osteosarcoma (OS), there are still many patients who cannot benefit from current treatment modalities. This warrants exploration of new treatment options. To that end, we investigated gene-directed enzyme prodrug therapy (GDEPT) with the use of human liver carboxylesterase-2 (CE2) and the anticancer agent CPT-11. CPT-11 is a clinically approved prodrug that needs to be metabolized into the active drug SN-38 by CEs, which occurs rather inefficiently in humans. GDEPT aims at high production of CE2 at the tumor site, resulting in efficient local conversion of CPT-11 into SN-38. Here, we show that OS cells transduced with an adenoviral vector containing the cDNA encoding a secreted form of CE2 (Ad-sCE2) expressed and efficiently secreted CE2. In vitro, transduction of a panel of OS cell lines with Ad-sCE2 resulted in sensitization up to 2800-fold to CPT-11 treatment. Primary OS short-term cultures, derived from patients suffering from a classic high-grade OS, demonstrated increased CPT-11 sensitivity up to 70-fold after transduction with Ad-sCE2 in vitro. When mice bearing s.c. MG-63 OS xenografts were intratumorally injected with Ad-sCE2 and CPT-11, this resulted in a significant difference in time to reach 2000 mm(3) in tumor volume as compared with animals receiving Ad-sCE2 or CPT-11 treatment (P < 0.05). Taken together, these data suggest that OS cells are sensitive for the combination of Ad-sCE2 and CPT-11.
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PMID:Gene-directed enzyme prodrug therapy for osteosarcoma: sensitization to CPT-11 in vitro and in vivo by adenoviral delivery of a gene encoding secreted carboxylesterase-2. 1293 66

ONYX-015 has been used successfully in the clinic as a cancer therapeutic in combination with chemotherapy. The combination of ONYX-015 and chemotherapy appears to be more efficacious than either regimen alone. In this study, we try to enhance this combination by "arming" ONYX-015 with a therapeutic transgene, an approach more commonly used with nonreplicating viruses in the context of gene therapy. We chose the prodrug converting enzyme carboxylesterase (CE), which converts the camptothecin derivative CPT-11 (irinotecan) to the much more potent chemotherapeutic SN-38. The transgene was introduced into three distinct positions in the E3 region of the adenovirus genome to allow either early or late expression during the virus life cycle. We demonstrate that each of these ONYX-015-based adenoviruses expresses an active CE enzyme that can efficiently convert CPT-11 to SN-38. Furthermore, the cytotoxicity of CE-expressing viruses, but not control viruses, is enhanced significantly in the presence of the prodrug. Finally, we demonstrate that we can achieve transgene expression and activity in vivo in a human tumor xenograft model, and that treatment with a CE-expressing virus in combination with CPT-11 enhances survival of tumor-bearing mice. These results indicate that the addition of a prodrug converting enzyme may be a feasible approach to additionally enhance the efficacy of replicating adenoviruses as cancer therapeutics.
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PMID:A prodrug strategy using ONYX-015-based replicating adenoviruses to deliver rabbit carboxylesterase to tumor cells for conversion of CPT-11 to SN-38. 1458 89

7-Ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (irinotecan, CPT-11) is a camptothecin prodrug that is metabolized by carboxylesterases (CE) to the active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38), a topoisomerase I inhibitor. CPT-11 has shown encouraging antitumor activity against a broad spectrum of tumor types in early clinical trials, but hematopoietic and gastrointestinal toxicity limit its administration. To increase the therapeutic index of CPT-11 and to develop other prodrug analogues for enzyme/prodrug gene therapy applications, our laboratories propose to develop camptothecin prodrugs that will be activated by specific CEs. Specific analogues might then be predicted to be activated, for example, predominantly by human liver CE(hCE1), by human intestinal CE (hiCE), or in gene therapy approaches using a rabbit liver CE (rCE). This study describes a molecular modeling approach to relate the structure of rCE-activated camptothecin prodrugs with their biological activation. Comparative molecular field analysis, comparative molecular similarity index analysis, and docking studies were used to predict the biological activity of a 4-benzylpiperazine derivative of CPT-11 [7-ethyl-10-[4-(1-benzyl)-1-piperazino]carbonyloxycamptothecin (BP-CPT)] in U373MG glioma cell lines transfected with plasmids encoding rCE or hiCE. BP-CPT has been reported to be activated more efficiently than CPT-11 by a rat serum esterase activity; however, three-dimensional quantitative structure-activity relationship studies predicted that rCE would activate BP-CPT less efficiently than CPT-11. This was confirmed by both growth inhibition experiments and kinetic studies. The method is being used to design camptothecin prodrugs predicted to be activated by specific CEs.
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PMID:Activation of a camptothecin prodrug by specific carboxylesterases as predicted by quantitative structure-activity relationship and molecular docking studies. 1461 91

We investigated the potential chemosensitizing effect of nicotinamide on CPT-11, and the relationship between nicotinamide and CPT-11, intratumoral drug uptake in syngeneic rhabdomyosarcoma tumors in rats. Pretreatment with nicotinamide, known to improve tumor oxygenation, perfusion and radiotherapy effect, only caused a minor increase in tumor growth delay. To our surprise, intratumoral uptake of CPT-11 and its active metabolite SN-38 decreased significantly between 19% and 43%. This discrepancy suggests that the potential chemosensitizing effect of nicotinamide, seen in other studies, is based on a direct effect on tumor cells rather than on an increased delivery of anticancer drugs. A second finding is that plasma levels of CPT-11 and SN-38 respectively increase and decrease after nicotinamide exposure, suggesting inhibition of carboxylesterase, which is necessary for the conversion of CPT-11 to its active metabolite SN-38. Great care is required when combining nicotinamide with anticancer drugs, since unexpected pharmacokinetic and pharmacodynamic alterations might occur.
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PMID:Unexpected interactions between nicotinamide and CPT-11 in a rhabdomyosarcoma tumor model. 1466 18

SN-38, 7-ethyl-10-hydroxycamptothecin, is the active metabolite of Irinotecan (CPT-11), a topoisomerase I inhibitor commercially available as Camptosar. SN-38 is approximately 200-2000-fold more cytotoxic than CPT-11. Despite its promising anticancer potential, SN-38 thus far has not been used as an anticancer drug due to its poor solubility in any pharmaceutically acceptable solvents. In addition, SN-38 has low affinity to lipid membranes; it tends to precipitate in aqueous phase resulting in a very low drug-to-liposome entrapment. SN-38 also reversibly converts to an inactive open lactone ring structure at physiological pH. We have developed a novel, liposome-based SN-38 formulation (LE-SN-38). The formulation contains liposomes of uniform size distribution (<200nm), and it is easy-to-use. Drug entrapment efficiency of the formulation is >95%. Long-term stability studies indicate that the lyophilized LE-SN-38 is physically and chemically stable for at least 6 months at 2-8 degrees C. In preclinical studies, LE-SN38 has shown promising results in terms of increased cytotoxicity against various tumor cell lines and better therapeutic efficacy towards xenograft mouse models compared to CPT-11.
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PMID:Development and characterization of a novel liposome-based formulation of SN-38. 1472 26

Irinotecan is an active cytotoxic agent for various cancers, and is converted to SN-38, its most active metabolite, by carboxylesterase converting enzyme (CCE) in vivo. Although the primary metabolic site is in the liver, ex vivo studies have proven that irinotecan is also converted to SN-38 in intestines, plasma and tumor tissues. The present study attempted to elucidate the in vitro conversion efficiency in human plasma, and to examine possible inter-individual variability and its clinical significance. Plasma samples were taken from 57 patients with lung cancer, 3 patients with benign pulmonary diseases and 9 healthy volunteers. After addition of 157 mM irinotecan to plasma, time courses of SN-38 concentration, measured by high-performance liquid chromatography (HPLC), were investigated. All subjects showed linear increase in SN-38 concentration during the first 60-min period, followed by a plateau. Mean and standard deviation of the conversion rate in the first 60 min were 515.9 +/- 50.1 pmol/ml/h (n = 69), with a coefficient of variation of 0.097. Although most of the subjects showed comparable conversion rates, 3 subjects had significantly higher conversion rates. In conclusion, the results of this study suggest that the enzyme activity of CCE in human plasma may show inter-individual variability.
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PMID:In vitro conversion of irinotecan to SN-38 in human plasma. 1518 36

Breast cancer resistance protein (BCRP), also called ABCG2, confers resistance to anticancer agents such as 7-ethyl-10-hydroxycamptothecin (SN-38), mitoxantrone, and topotecan. We found previously that sulfated estrogens are physiologic substrates of BCRP. Flavonoids with weak estrogenic activities are called phytoestrogens. In this study, we show that phytoestrogens/flavonoids, such as genistein, naringenin, acacetin, and kaempferol, potentiated the cytotoxicity of SN-38 and mitoxantrone in BCRP-transduced K562 (K562/BCRP) cells. Some glycosylated flavonoids, such as naringenin-7-glucoside, also effectively inhibited BCRP. These flavonoids showed marginal effect on the drug sensitivity of K562 cells. Genistein and naringenin reversed neither P-glycoprotein-mediated vincristine resistance nor multidrug resistance-related protein 1-mediated VP-16 resistance. Genistein and naringenin increased cellular accumulation of topotecan in K562/BCRP cells. K562/BCRP cells also accumulated less [(3)H]genistein than K562 cells. [(3)H]genistein transport in the basal-to-apical direction was greater in BCRP-transduced LLC-PK1 (LLC/BCRP) cells, which express exogenous BCRP in the apical membrane, than in parental cells. Fumitremorgin C abolished the increased transport of [(3)H]genistein in LLC/BCRP cells compared with parental cells. TLC analysis revealed that genistein was transported in its native form but not in its metabolized form. These results suggest that genistein is among the natural substrates of BCRP and competitively inhibits BCRP-mediated drug efflux. The results have two important clinical implications: (a) flavonoids and glycosylated flavonoids may be useful in overcoming BCRP-mediated drug resistance in tumor cells; and (b) coadministration of flavonoids with BCRP-substrate antitumor agents may alter the pharmacokinetics and consequently increase the toxicity of specific antitumor agents in cancer patients.
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PMID:Phytoestrogens/flavonoids reverse breast cancer resistance protein/ABCG2-mediated multidrug resistance. 1520 50

Due to the emergence of new anticancer agents for the treatment of ovarian cancer, methods to determine which agents will be most effective in individual patients are required. In order to investigate the potential for tailor-made chemotherapy, the drug sensitivities of various ovarian cancers were examined using collagen gel droplet embedded culture drug sensitivity testing (CD-DST), and the results were correlated with clinical outcomes. Sensitivities to paclitaxel, cisplatin, doxorubicin, etoposide, and SN-38, which is an active metabolite of irinotecan, were examined. Eight out of 22 samples failed to grow colonies and thus, their cell sensitivities could not be determined. Out of the 14 cases from which CD-DST results were obtained, seven patients then received chemotherapy aimed at inducing remission, while four received adjuvant, and three did not receive any chemotherapy. Three of the four tumors subsequently treated with adjuvant chemotherapy showed sensitivity to TXL and CDDP on CD-DST analysis, while one did not. None of these patients experienced recurrent disease from 24 to 36 months. Five of the seven tumors subsequently treated with chemotherapy aimed at inducing remission showed sensitivity to the relevant anticancer agents upon CD-DST analysis, while two did not. Among the five cases that showed tumor cell sensitivity, three experienced complete responses, one achieved a partial response and one had progressive disease. For the remaining two cases that demonstrated tumor cell resistance, one had stable disease and one had progressive disease following chemotherapy. Thus, six out of the seven cases (85.7%) that received chemotherapy aimed at inducing remission had clinical outcomes in keeping with the results of CD-DST. In conclusion, CD-DST results reflect clinical outcomes and may be a useful means by which to select drugs to which ovarian cancer cells are chemosensitive.
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PMID:Usefulness of collagen gel droplet embedded culture drug sensitivity testing in ovarian cancer. 1525 94

As a single agent the ERBB1 inhibitor, gefitinib (Iressa; ZD1839) showed minimal activity against a panel of 10 pediatric tumor xenografts that do not express the ERBB1 receptor. However, combined with irinotecan (CPT-11), significantly greater than additive activity was observed in four of eight models (P < 0.05), and the combination showed enhanced activity against three additional tumor lines. Breast cancer resistance protein (ABCG2), a transporter that confers resistance to SN-38 (the active metabolite of irinotecan), was readily detected in six of nine xenograft models examined by immunohistochemistry. In vitro gefitinib potently reversed resistance to SN-38 only in a cell line that overexpressed functional ABCG2. However, overexpression of ABCG2 did not decrease accumulation nor increase the rate of efflux of [(14)C]gefitinib. On the basis of these results and the distribution of Abcg2 in mouse tissues, we assessed the ability of gefitinib to modulate irinotecan pharmacokinetics. Oral gefitinib coadministration resulted in no change in clearance of intravenously administered irinotecan. However, gefitinib treatment dramatically increased the oral bioavailability of irinotecan after simultaneous oral administration. It is concluded that gefitinib may modulate SN-38 activity at the cellular level to reverse tumor resistance mediated by ABCG2 through inhibiting drug efflux and may be used potentially in humans to modulate the oral bioavailability of a poorly absorbed camptothecin such as irinotecan.
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PMID:Gefitinib enhances the antitumor activity and oral bioavailability of irinotecan in mice. 1549 75

SN-38 is an active metabolite of CPT-11. The poor solubility of SN-38 in any pharmaceutically acceptable solvent and pH-dependent activity has limited its clinical use. Our objective was to evaluate an easy-to-use liposome-based formulation of SN-38 (LE-SN38) and compare the antitumor activity with its pro-drug CPT-11 against cancer cell lines and human xenograft tumor models. The cytotoxicity of LE-SN38 and CPT-11 was determined in four human cancer cell lines using the sulforhodamine B assay. The therapeutic efficacy was tested against human colon (HT-29) and breast (MX-1) xenograft tumor models in SCID mice. LE-SN38 with greater than 95% drug entrapment was found to be highly cytotoxic against four different cell lines with GI50 values of less than 0.1 microM. In the HT-29 tumor model, LE-SN38 (q x d5) at 2, 4 or 8 mg/kg resulted in 33, 81 and 91% tumor growth inhibition, respectively, compared to the drug-free liposome group. In contrast, similar dose levels of CPT-11 treatment led to only 2, 36 and 46% growth inhibition. For the MX-1 model, LE-SN38 (q x d5) regressed tumor growth by 44 and 88% at 4 and 8 mg/kg dose, respectively, whereas no regression was observed in the CPT-11-treated group. We conclude that LE-SN38 is a novel liposome-based formulation with enhanced therapeutic efficacy against human tumor models.
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PMID:Enhanced therapeutic efficacy of a novel liposome-based formulation of SN-38 against human tumor models in SCID mice. 1549 39


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