Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The outcome of cancer metastasis depends on the interaction of metastatic cells with various host factors. The implantation of human cancer cells into anatomically correct (orthotopic) sites in nude mice can be used to ascertain their metastatic potential. While it is clear that vascularity and local immunity can retard or facilitate tumor growth, we have found that the organ environment also influences tumor cell functions such as production of degradative enzymes. The organ microenvironment can also influence the response of metastases to chemotherapy. It is not uncommon to observe the regression of cancer metastases in one organ and their continued growth in other sites after systemic chemotherapy. We demonstrated this effect in a series of experiments using a murine fibrosarcoma, a murine colon carcinoma, and a human colon carcinoma. The tumor cells were implanted subcutaneously or into different visceral organs. Subcutaneous tumors were sensitive to doxorubicin (DXR), whereas lung or liver metastases were not. In contrast, sensitivity to 5-FU did not differ between these sites of growth. The differences in response to DXR between s.c. tumors (sensitive) and lung or liver tumors (resistant) were not due to variations in DXR potency or DXR distribution. The expression of the multidrug resistance-associated P-glycoprotein as determined by flow cytometric analysis of tumor cells harvested from lesions in different organs correlated inversely with their sensitivity to DXR: increased P-glycoprotein was associated with overexpression of mdr1 mRNA. However, the organ-specific mechanism for upregulating mdr1 and P-glycoprotein has yet to be elucidated.
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PMID:Modulation of tumor cell response to chemotherapy by the organ environment. 792 51

In this study we report detection of mdr1 gene expression in the liver metastases of 7/11 patients with colon carcinoma and characterise the MDR phenotype associated with a panel of 19 human colon carcinoma cell lines. Within this panel, mdr1 mRNA biosynthesis and surface localisation of Pgp were assessed with respect to MDR functionality where the cell lines are representative of different clinical stages of tumour progression, metastatic potential and differentiation. The data indicates that constitutive levels of mdr1 mRNA/Pgp expression may not necessarily result in the functional expression of the MDR phenotype. While low levels of mdr1 mRNA/Pgp were detected in 5/8 well differentiated colon cell lines, only 2/8 were functionally MDR. In contrast, 10/11 moderate and poorly differentiated lines expressed mdr1 mRNA/Pgp and of these, 9/11 were functionally MDR. The phosphorylation status of the mature 170 kD P-glycoprotein and the surface localisation of this glycoprotein showed the strongest correlation with functionality. Analysis of cell lines for cross-resistance and chemosensitivity profiles against a battery of chemotherapeutic drugs suggests multiple mechanisms, in addition to Pgp, contribute to the overall resistance of colorectal cancer.
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PMID:Constitutive expression of multidrug resistance in human colorectal tumours and cell lines. 809 14

Differences in therapeutic outcomes after regional chemotherapy or chemo-immunotherapy in liver metastases from colorectal carcinoma cannot be explained only by variations in the regimens of treatment. This study was undertaken to assess the potential of several tumor-associated markers of biological behavior (biomarkers) to predict therapeutic response in order to pre-select the best candidates for this demanding treatment. In a group of 21 patients, flow cytometric DNA ploidy provided the most accurate prediction, with a response rate of 88% in 8 DNA diploid tumors compared to 31% in 13 DNA aneuploid cases (P = 0.017) and a difference in overall survival of nine months (20.4 vs 11.3, P = 0.041). Only a slight trend towards improved response rate was observed when we immunohistochemically detected p53 anti-oncoprotein expression in 11 (52%) p53-positive tumors (P = 0.063). Other immunohistochemical biomarkers as P-glycoprotein (p170), p21/WAF, mdm2, c-erbB-2, and proliferative activity of tumor (detected either by anti-PCNA and anti-Ki67 monoclonal antibodies or as a flow cytometric proliferation index) were unrelated to the outcome of treatment. DNA ploidy and expression of p53 protein are potential biomarkers for predicting the response to regional chemotherapy of liver metastases from colorectal carcinoma.
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PMID:Biomarkers for predicting response to regional chemo-immunotherapy in liver metastases from colorectal carcinoma. 963 42

To assess the therapeutic efficacy in the combination of mitomycin C (MMC), 5'-deoxy-5-fluorouridine (5'-DFUR), etoposide (VP-16) and medroxyprogesterone acetate (MPA) (McVD-MPA) to anthracycline-resistant tumor as a salvage chemotherapy, a phase II trial was conducted in patients with relapsed breast cancer. Fifty-five patients were enrolled in this trial and 54 were assessable, who had all previously been treated with an anthracycline regimen. The treatment schedule was designed with the intravenous administration of MMC (6 mg/m2) on day 1 followed by peroral administration of VP-16 (75 mg/m2) on day 2, 4, 6 and the peroral administration of 5'-DFUR (600 mg/m2) and MPA (400 mg/m2) on day 1 through 21 in one cycle. The overall tumor response rate was 40.7% (22/54) including 16.6% (9 cases) in complete response and 24.0% (13 cases) in partial response, and the long no change (NC) was observed in 18.5% (10/54) out of 44.4% (24/54) in NC. Of the patients with primary resistance to anthracycline 30.0% responded to McVD-MPA therapy. Bone and liver metastases responded in 50.0% and 50.0%, whereas soft tissue and lung metastases responded in 36.8% and 35.2%, respectively. The mean time to response and response duration were 2.7 and 15.6 months, respectively. The overall survival of the patient treated with the McVD-MPA was superior to the non-treatment of second line therapy, and the median survival between McVD-MPA and non-treatment was 86 days and 50 days, respectively. The major adverse effect was observed in hematological toxicity (31.7%) such as leukopenia and thrombocytopenia and non-hematological toxicity of gastrointestinal events (31.7%), the toxicity was less than grade 2, and was tolerable during the treatment. In the experiment of MDA-MB-231 breast cancer cell line that was overexpressed with P-glycoprotein (P-gp) and multidrug resistance associated protein (MRP), the mechanism(s) by which McVD-MPA induces the antitumor effect to anthracycline-resistant tumor may be explained at least in part as follows: i) The treatment of MMC suppressed the expression of P-gp and MRP in a dose-and time-dependent manner, connecting the increase of the intracellular concentration of VP-16; ii) The treatment of MMC enhanced the expression of thymidine phosphorylase to increase the production of 5-FU from 5'-DFUR in the antiangiogenic effect of MPA. These results indicate that the combination chemotherapy of the McVD-MPA may be an effective regimen to anthracycline-resistant tumor as a salvage chemotherapy to prolong the survival in the patient with relapsed breast cancer.
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PMID:A phase II trial of mitomycin C, 5'-deoxy-5-fluorouridine, etoposide and medroxyprogesterone acetate (McVD-MPA) as a salvage chemotherapy to anthracycline-resistant tumor in relapsed breast cancer and its mechanism(s) of antitumor action. 1129 87

Relevant drawbacks of the molecular structure and mechanism of the action of camptothecins are the instability of the E ring lactone and the reversibility of drug-target interaction. Such features are expected to limit the clinical efficacy of conventional camptothecins. In an attempt to overcome these limitations and to improve the pharmacological profile of camptothecins, a novel series of seven modified lipophilic analogues was synthesized based on the hypothesis that lipophilicity could promote a rapid cellular accumulation and stabilization of drug-target interaction. A novel analogue (ST1481) of the series, characterized by a potent antitopoisomerase and cytotoxic activity, was selected for preclinical development. A detailed preclinical study of ST1481 was performed in the H460 non-small cell lung tumor model using oral administration and various treatment schedules. Under all of the conditions, ST1481 exhibited an impressive efficacy in terms of tumor growth inhibition (tumor volume inhibition percentage > 99%), log(10) cell kill, rate of complete responses (including "cures"), and an improvement of the therapeutic index compared with topotecan (used as the reference drug). The cytotoxic potency was also reflected by the in vivo potency, because the drug activity was observed at doses as low as 0.25 mg/kg with the daily schedule. In contrast to topotecan, no cross-resistance to ST1481 was found in ovarian carcinoma cells overexpressing P-glycoprotein (A2780/DX). A similar trend in the improvement of activity was also observed in the same tumor model growing in vivo with a 100% rate of complete tumor regressions. A rapid intestinal absorption and good oral bioavailability were supported by in vivo distribution studies, because the peak values of drug accumulation were found from 1 to 2 h after administration. The relevant liver accumulation may account for a marked effect of ST1481 against liver metastases induced by the ovarian carcinoma IGROV-1. In conclusion, the results support the hypothesis that a potent lipophilic camptothecin with a proper substituent at the position 7 may have therapeutic advantages likely related to a rapid intracellular uptake and tissue distribution, stabilization of the drug-target complex, and good oral bioavailability. Overall, the results support the preclinical interest of ST1481 in terms of efficacy, potency, toxicity profile, and ability to overcome multidrug resistance.
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PMID:Potent antitumor activity and improved pharmacological profile of ST1481, a novel 7-substituted camptothecin. 1158 54

The purpose of the study was to determine whether the organ environment can influence the response of colon cancer cells to chemotherapy. The highly metastatic human colon cancer cell line KM12L4, previously selected for production of liver metastases in nude mice, was injected into the cecal wall and into the spleen to produce liver metastases, and into the subcutis of nude mice. Doxorubicin (DOX) at 10 mg/kg or saline (control) was injected intravenously on days 7 and 16 after tumor cell injection. The in vivo response of tumors growing in the cecum, liver, and subcutaneous (s.c.) sites as well as the DOX sensitivity of cell lines established from liver and s.c. tumors were compared. Colon cancers growing s.c. were more sensitive to DOX than tumors growing in the cecal wall or liver of nude mice. The difference in response to DOX between s.c. tumors (sensitive) and liver tumors (resistant) was not due to selection of cell populations with different sensitivity to DOX, or differences in DOX distribution. PKC activity was lower in tumors of the liver and the cecum than in s.c. tumors. The expression of P-glycoprotein as determined by flow cytometric analysis of tumor cells harvested from lesions in different organs correlated inversely with their sensitivity to DOX. Increased levels of P-glycoprotein correlated with mdr-1, mdr-3 mRNA expression as determined by Northern analysis. Collectively, the data show that the organ environment influences the response of human colon carcinoma cells to DOX and recommend that animal models of this disease for experimental therapeutic studies employ orthotopic implantation of tumor cells.
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PMID:Modulation of Doxorubicin sensitivity and level of p-glycoprotein expression in human colon-carcinoma cells by ectopic and orthotopic environments in nude-mice. 2157 80