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

Topotecan is a topoisomerase (topo) I inhibitor with promising activity in preclinical studies. We hypothesized that low-dose intratumoral delivery of topotecan would be highly effective for gliomas. Human glioma cell lines (U87, U138 and U373) displayed different sensitivities to topotecan (IC50 range: 0.037 microM to 0.280 microM) in cell culture. The most resistant of the glioma cell lines (U87) was implanted stereotactically into the brains of nude rats. Twelve days later, at which time tumor diameter measured 2 to 2.5 mm, animals were randomized to three groups: group I, intratumoral topotecan infused via osmotic pump (n = 12); group II, intratumoral saline infusion (n = 7); and group III, no treatment (n = 10). Animals were sacrificed when signs of deterioration developed, or at 60 days. Animals in group I had a mean survival time (MST) of > 55 days (range = 40-60); whereas, those in groups II and III had MST of 26.1 (range = 21-31) and 26.5 (range = 20-30) days, respectively. The differences in survival between group I and each of the other groups were statistically significant (p < 0.0001; Logrank Mantel-Cox). None of the animals that survived 60 days had histological evidence of residual tumor at sacrifice. Measurement of topotecan levels in normal brain revealed cytotoxic concentrations up to 4.5 mm from the site of infusion. This study demonstrates that intratumoral topotecan delivered via an osmotic pump prolongs survival in the U87 human glioma model.
 ...
PMID:Intratumoral infusion of topotecan prolongs survival in the nude rat intracranial U87 human glioma model. 982 Nov 7

The topoisomerase I inhibitor topotecan had demonstrated good antitumor activity in several murine tumor systems and in human clonogenic assays by 1993. In that year, the Cancer and Leukemia Group B (CALGB) began a phase II trial to determine its activity in patients with breast cancer who had previously received one course of chemotherapy for advanced breast cancer. Between April 1993 and June 1994, 53 patients of performance status 0-2 entered the study, of whom 47 were eligible and 40 were evaluable. Topotecan was given at a dose of 1.5 mg/m2 over 30 minutes daily for 5 days every 21 days. In the absence of progression or withdrawal of consent, therapy was continued indefinitely. The median age was 58 years (range 30-79). There were no complete responses and four partial responses, resulting in an objective response rate of 10% (95% CI: 3-24%). Responses were noted in lymph nodes, liver, and skin. The median duration of response was 5 months. The median survival was 12 months. Life-threatening toxicities were almost exclusively hematologic. However, myelosuppression was not cumulative. It was concluded that topotecan has only modest activity among women with advanced breast cancer who have previously received one course of chemotherapy. Given its modest activity and predominant hematologic toxicity, it does not appear to be a promising drug for either single-agent or combination chemotherapy in the salvage setting of advanced breast cancer.
 ...
PMID:Phase II trial of topotecan in advanced breast cancer: a Cancer and Leukemia Group B study. 1036 25

Topoisomerase I inhibitors are a new class of anticancer agents with a mechanism of action aimed at interrupting DNA replication in cancer cells, the result of which is cell death. Most if not all Topoisomerase I inhibitors are derivatives of the plant extract camptothecin. Irinotecan (CPT-11), a semi-synthetic derivative of camptothecin, is approved in the United States for the treatment of colorectal cancer. Ongoing clinical trials with CPT-11 show a 13% to 32% response rate when it is used singly or in combination with other chemotherapeutic agents such as 5-fluorouracil. The major dose-limiting toxicities of CPT-11 are myelosuppression and a dual phase diarrhea. Topotecan is another semi-synthetic analogue of camptothecin. It is approved for use in the United States for the treatment of cisplatin refractory ovarian carcinoma. Current clinical trials suggest antitumor activity against a variety of human tumor types. There is significant interindividual variability in the plasma disposition of this drug. The main dose-limiting toxicity is myelosuppression. There are other derivatives of camptothecin, as well as new formulations of the parent plant extract, that are in various stages of clinical trials. Some of these clinical trials are aimed at increasing the therapeutic benefits of the agents when used singly or in combination with other chemotherapeutic agent(s) or treatment modalities. The dose-limiting toxicity observed in most of these clinical trials is myelosuppression.
 ...
PMID:Topoisomerase I Inhibitors. 1038 70

This issue of The Oncologist provides the reader with two useful reviews of the new chemotherapeutic agent topotecan, one of a class of topoisomerase I inhibitors that is being studied and incorporated into the treatment of various malignancies. Topotecan was approved for the treatment of refractory ovarian cancer in 1996, and has shown promising activity against a variety of solid tumors, as well as hematologic malignancies. One paper discusses clinical guidelines for managing topotecan-related hematologic toxicities, and centers on data derived from ovarian cancer studies. The other focuses on the role of topotecan in the treatment of small cell lung cancer (SCLC), where it has consistently shown encouraging results and for which definitive trials are now being conducted. As front-line therapy for ovarian cancer and small cell lung cancer is dominated by platinum-based regimens, the dosing guidelines and management issues discussed are pertinent for both tumor types.
 ...
PMID:Topotecan: Incorporating It Into the Treatment of Solid Tumors. 1038 78

Topotecan (Hycamtin(R)) is a topoisomerase I inhibitor which demonstrated a wide spectrum of antitumor activity in preclinical models. During phase I assessment, evidence of activity was most promising when topotecan was administered on an i.v. daily x 5 schedule and a dose of 1.5 mg/m(2)/day was selected for phase II/III evaluation. This regimen has been shown to have activity in a wide range of tumor types, including recurrent ovarian cancer, relapsed small cell lung cancer (SCLC), non-small cell lung cancer, colon cancer, and breast cancer, as well as hematological malignancies. In patients with ovarian cancer who had failed standard therapy, topotecan demonstrated response rates of 13% to 25%, with median times to progression of 12 to 19 weeks. Compared with paclitaxel, the response rates were similar, 20.5% and 14.0%, respectively, as were median times to progression (19 weeks for topotecan versus 15 weeks for paclitaxel). Results in recurrent SCLC have also been encouraging. Patients sensitive to previous chemotherapy have shown response rates of 19% and 39%, and even patients resistant or refractory to previous chemotherapy have had responses of 3% and 7%. Survival ranged from 20 weeks in refractory disease to 12 months in both sensitive and resistant/refractory disease combined. The safety profile of topotecan is well established. The principal toxicity is noncumulative myelosuppression, and serious sequelae are uncommon. Nonhematological toxicities are generally mild. The use of topotecan in combination regimens is promising, although clinical results are currently at an early stage. To date, topotecan has demonstrated its activity in recurrent ovarian cancer and offers a valuable addition to treatment options in relapsed SCLC.
 ...
PMID:Topotecan: An Oncologist's View. 1038 30

Mxi1 is thought to negatively regulate Myc function and may therefore be a potential tumor suppressor gene. Little effort has yet been made to find alterations involving this gene in human solid tumors. We screened 31 human gastric cancers, 7 esophageal cancers, 85 bone and soft tissue tumors of various types, including 4 neurofibrosarcomas. We also examined 29 human tumor cell lines consisting of 12 esophageal cancers, 7 glioma/glioblastomas and 10 others for Mxi1 mutations in exons 1, 2, 4 (HLH domain), 5 and 6. Polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and subsequent sequencing revealed three distinct polymorphisms in the intron-exon boundary upstream from exon 6. We discovered a missense mutation, GCA to GTA (Ala 54 Val), in exon 2 in a neurofibrosarcoma patient (case 1), two missense mutations, AAA to CAA (Lys 118 Gln) and GAA to GGA (Glu 154 Gly) in exon 5 of another neurofibrosarcoma patient (case 2), and 3 amino acid substitutions, GTG to GCG (Val 179 Ala), GTT to GCT (Val 181 Ala) and TTC to CTC (Phe 186 Leu), in a third neurofibrosarcoma patient (case 3). In case 3, loss of heterozygosity was also demonstrated by informative (TTC)3/(TTC)2 polymorphism. Our data demonstrate that mutations occur in the Mxi1 gene in neurofibrosarcoma. Missense mutations in the functional domain of Mxi1 in these cases may be involved in the pathogenesis of neurofibrosarcoma.
 ...
PMID:Mxi1 mutations in human neurofibrosarcomas. 1047 Feb 86

Topotecan- or mitoxantrone-selected cell lines (T8 and MX3, respectively), derived from the human IGROV1 ovarian cancer cell line, were resistant to the topoisomerase I inhibitors topotecan, SN-38 (the active metabolite of irinotecan), and 9-aminocamptothecin, as well as to the topoisomerase II drug mitoxantrone. In both resistant cell lines, decreased accumulation of topotecan and mitoxantrone was observed, caused by enhanced energy-dependent efflux of the drugs involved. In both cell lines, we found that the breast cancer resistance protein/mitoxantrone resistance/placenta-specific ATP binding cassette (BCRP/MXR/ABCP) gene was overexpressed. Furthermore, BCRP/MXR/ABCP expression levels in various partially revertant T8 cells correlated with the levels of resistance to topotecan, SN-38, and mitoxantrone, strongly suggesting BCRP/MXR/ABCP to be the transporter responsible for the enhanced efflux. Pharmacodynamic analysis demonstrated that BCRP/MXR/ABCP is a very efficient transporter of topotecan; in vitro, 70% of the intracellular topotecan pool was transported out of the T8 or MX3 cells within 30 s. In conclusion, we report for the first time that BCRP/MXR/ABCP can also be up-regulated upon exposure of tumor cells to the clinically important drug topotecan, and that BCRP-mediated efflux of topotecan is very efficient. This highly efficient efflux of topotecan by BCRP/MXR/ABCP may have clinical relevance for patients being treated with topotecan.
 ...
PMID:Overexpression of the BCRP/MXR/ABCP gene in a topotecan-selected ovarian tumor cell line. 1049 7

DX-8951f, which shows great therapeutic potential, was tested in the human tumor cloning system in adult and pediatric tumor types against which topotecan has been active. In 47 tumors from adults, DX-8951f had definite cytotoxic activity in a concentration-dependent manner with both 1 h and continuous exposures. Topotecan was minimally effective using a 1 h exposure and showed concentration-dependent inhibition with continuous exposure. In head-to-head comparisons at 1 h exposure against adult tumors, DX-8951f was significantly more effective at 0.1 and 1.0 microg/ml than topotecan. In head-to-head comparisons (continuous exposure), 1.0 microg/ml DX-8951f was more effective than topotecan at 1.0 microg/ml in adult tumors, including three of four head and neck, one of two kidney, two of five liver, six of 10 non-small cell lung, five of eight ovarian, four of eight prostate tumors, and in single specimens of breast, mesothelioma, colon and small cell lung tumors. With continuous exposure, DX-8951f and topotecan were equally effective at equimolar concentrations. The maximum tolerated dose for DX-8951f is 3 times that of topotecan, so higher doses of DX-8951f could be administered to patients. DX-8951f is a promising new antineoplastic agent with significant activity against tumors taken directly from patients.
 ...
PMID:Comparison of DX-8951f and topotecan effects on tumor colony formation from freshly explanted adult and pediatric human tumor cells. 1050 15

Topotecan and vincristine were evaluated alone or in combination against 13 independent xenografts and 1 vincristine-resistant derivative, representing childhood neuroblastoma (n = 6), rhabdomyosarcoma (n = 5), or brain tumors (n = 3). Topotecan was given by i.v. bolus on a schedule found previously to be optimal. Drug was administered daily for 5 days on 2 consecutive weeks with cycles repeated every 21 days over a period of 8 weeks. Doses of topotecan ranged from 0.16 to 1.5 mg/kg to simulate clinically achievable topotecan lactone plasma systemic exposures. Vincristine was administered i.v. every 7 days at a fixed dose of 1 mg/kg. Given as a single agent, vincristine induced complete responses (CRs) in all mice bearing two rhabdomyosarcomas (Rh28 and Rh30) and some CRs in Rh12-bearing mice (57%) but relatively few CRs (<29%) in other tumors. As a single agent, topotecan induced CR in a low proportion of tumor lines. A dose-response model with a logit link function was used to investigate whether the combination of topotecan and vincristine resulted in greater than expected responses compared with the activity of the agents when administered alone. Only CR was used to evaluate tumor responses. The combination resulted in significantly greater than expected CRs than individual agents in nine tumor lines (four neuroblastoma, three brain tumors, and two rhabdomyosarcomas). Similar event-free (failure) distributions were shown in SJ-GBM2 glioblastoma xenografts, whether vincristine was administered on day 1 or day 5 of each topotecan course. To determine whether the increased antitumor activity with the combination was attributable to a change in drug disposition, extensive pharmacokinetic studies were performed. However, little or no interaction between these two agents was determined. Toxicity of the combination was marked by prolonged thrombocytopenia and decreased hemoglobin. However, approximately 75 and 80% of the maximum tolerated dose of each single agent, topotecan (1.5 mg/kg) or vincristine (1 mg/kg), could be given in combination, resulting in a combination toxicity index of approximately 1.5. These results show that the therapeutic effect of combining topotecan with vincristine was greater than additive in most tumor models of childhood solid tumors, and toxicity data suggest that this can be administered to mice with only moderate reduction in the dose levels for each agent.
 ...
PMID:Synergy of topotecan in combination with vincristine for treatment of pediatric solid tumor xenografts. 1058 79

Based on experimental and epidemiological evidence it is hypothesized that estrogen increases breast cancer risk by increasing mitotic activity in breast epithelial cells. Aromatase is crucial to the biosynthesis of estrogens and may therefore play a role in breast cancer development. Supporting data for an etiological role of aromatase in breast tumor biology are several-fold. First, the association between weight and postmenopausal breast cancer risk may be mediated by aromatase. Secondly, a pilot study found a higher aromatase expression in normal breast adipose tissue from breast cancer cases as opposed to healthy women. Thirdly, experimental data in animals suggest that aromatase activity predisposes mammary tissue to preneoplastic and neoplastic changes. In a multiethnic cohort study conducted in Los Angeles and on Hawaii we investigated (i) whether the plasma estrone to androstenedione (E1/A) ratio in different ethnic groups was associated with ethnic differences in breast cancer incidence, and (ii) whether genetic variation in the CYP19 gene encoding the P450 aromatase protein was associated with breast cancer risk. The age- and weight-adjusted ethnic specific E1/A ratios x 100 among women without oophorectomy were 7.92 in African-Americans, 8.22 in Japanese, 10.73 in Latinas and 9.29 in non-Latina Whites (P=0.09). The high E1/A ratio in Latina women was not associated with a high breast cancer incidence; in fact Latina women had the lowest breast cancer incidence in the cohort observed so far. We found no consistent association of an intronic (TTTA)n repeat polymorphism with breast cancer risk in different ethnic groups. This polymorphism was not associated with differences in the plasma E1/A ratio in a way that would predict its functional relevance. We describe a newly identified TTC deletion in intron 5 of the CYP19 gene that is associated with the (TTTA)n repeat polymorphism. Neither this polymorphism, nor a polymorphism at codon 264 in exon VII of the CYP19 gene, was associated with breast cancer. We did not identify any genetic variation in exon VIII in 54 African-American subjects. We identified rare genetic variants of unknown functional relevance in the promoter 1.4 of the CYP19 gene in 3 out of 24 Latina women. Further investigation into the role of aromatase in breast cancer etiology is important, given that the potential use of aromatase inhibitors as breast cancer chemopreventives depends on these results.
 ...
PMID:Aromatase and breast cancer susceptibility. 1073 Nov 5


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>