metallothionein and propargylglycine

The platinum-based chemotherapeutic agent cisplatin is involved in a broad spectrum of activities against human systemic malignancies. However, acquired resistance to cisplatin reduces its clinical efficacy. Elucidation of the molecular basis of cisplatin resistance is required to improve the effectiveness of cisplatin. In the present study, the mechanism of acquired resistance to cisplatin was studied in C3H mice inoculated with MBT-2 murine bladder tumor cells.. C3H mice were subcutaneously inoculated with 1.0 x 10(6) MBT-2 cells/mouse on day 0. The mice were given intraperitoneal injections of 10 micro mol/kg cisplatin and subcutaneous injections of 1000 micro mol/kg propargylglycine, an inhibitor of gamma-cystathionase, once a day for 10 consecutive days from day 11 to day 20.. The metallothionein content of the tumors was increased to twice the control level by repeated administration of cisplatin. Co-administration of propargylglycine reduced metallothionein induction in the tumors and markedly enhanced the antitumor activity of cisplatin. In contrast, the glutathione content in the tumors did not change from the control level after cisplatin administration. The platinum accumulation in tumors treated with cisplatin alone was 1.7-fold greater than when propargylglycine was administered concomitantly. The platinum concentrations changed in accordance with the metallothionein contents.. These observations suggest that metallothionein, but not glutathione or reduced platinum accumulation, might play a role in the acquired resistance to cisplatin of C3H mice inoculated with MBT-2. Moreover, reversal of this resistance might be possible by biochemical modulation of metallothionein.

Topics: Alkynes; Animals; Antineoplastic Agents; Carcinoma, Transitional Cell; Cisplatin; Cystathionine gamma-Lyase; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Enzyme Inhibitors; Female; Glutathione; Glycine; Injections, Intraperitoneal; Metallothionein; Mice; Mice, Inbred C3H; Neoplasm Transplantation; Urinary Bladder Neoplasms

Reactive oxygen species (ROS)-specific mechanisms of drug resistance were explored in paraquat (PQ)-resistant acute myelogenous leukemia cell (OCI/AML-2) sublines. For this, PQ-resistant AML sublines, AML-2/PQ100 and AML-2/PQ400, were selected in the presence of PQ concentrations of 100 microg/ml and 400 microg/ml, respectively. They showed a moderate level of cross resistance to cisplatin and doxorubicin. They were also slightly more resistant than the parental cell (AML-2/WT) to etoposide, camptothecin and daunorubicin. The resistance of PQ-resistant AML-2 sublines to cisplatin seemed to be due to increased amounts of metallothionein, which was not only supported by reversal of resistance to cisplatin by propargylglycin (an inhibitor of metallothionein synthesis) but also confirmed by Western blot analysis and reverse transcription-PCR assay. In addition, both AML-PQ100 and /PQ400 sublines showed increased activities of Cu-, Zn-containing superoxide dismutase (Cu,Zn-SOD) and Mn-containing superoxide dismutase (Mn-SOD), whereas AML-2/PQ400, but not AML-2/PQ100, showed increased glutathione S-transferase activity as compared to that of AML-2/WT. However, there was no difference in other ROS-related cellular antioxidants between AML-2/WT and its PQ-resistant sublines. Taken together, these results strongly suggest that increases in levels of metallothionein, glutathione S-transferase, Cu,Zn-SOD and Mn-SOD play important roles in protective mechanisms against toxicity of PQ or ROS in AML cells.

Topics: Alkynes; Antineoplastic Agents; Camptothecin; Cell Survival; Cisplatin; Daunorubicin; Dose-Response Relationship, Drug; Doxorubicin; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Etoposide; Glutathione Transferase; Glycine; Humans; Leukemia, Myeloid, Acute; Metallothionein; Paraquat; Proto-Oncogene Proteins c-bcl-2; Reactive Oxygen Species; Superoxide Dismutase; Tumor Cells, Cultured; Vincristine

Effect of propargylglycine (2-Amino-4-pentynoic acid, PPG) on invasive property of human fibrosarcoma HT-1080 cell was investigated. PPG treatment of HT-1080 significantly reduced the total cellular metallothioneins (MTs) contents, and the resistance of HT-1080 against heavy metals toxicity decreased with the decrease of the MTs contents. The HT-1080 cell invasion to reconstituted basement membrane Matrigel (MG) was inhibited by the PPG treatment in a PPG concentration-dependent fashion. The inhibition was due to the lowering of HT-1080 cells attachment to MG and degradation activity of matrix metalloproteinases (MMPs) secreted from HT-1080 by the PPG treatment. However, the chemotactic ability of the PPG treated HT-1080 was enhanced. Our results suggest that MTs concentration levels in a malignant tumor cell are closely related to its invasiveness, and if MTs level of tumor cell can be controlled, cancer metastasis may be able to be controlled.

Topics: Alkynes; Cadmium; Chemotaxis; Collagen; Copper; Dose-Response Relationship, Drug; Drug Combinations; Fibronectins; Fibrosarcoma; Glycine; Humans; Laminin; Metallothionein; Neoplasm Invasiveness; Platinum; Proteoglycans; Time Factors; Tumor Cells, Cultured

A protective role for metallothionein (MT) in cellular injury caused by ionizing radiation has been proposed. To elucidate the role of MT in the sensitivity of tumors to radiation, we examined the effectiveness of radiation treatment of tumors with altered synthesis of MT after injection of tumor-bearing mice with zinc and/or propargyl glycine (PPG). The mice were inoculated with Meth-A fibrosarcoma cells and the antitumor activity of X radiation was tested in mice with and without induced synthesis of MT. Exposure to X radiation decreased the tumor weight markedly. In mice pretreated with zinc to induce MT, the tumor weight did not change compared to the controls. However, injection of PPG, an inhibitor of cystathionase, decreased the zinc-induced MT synthesis in the tumors and also decreased the tumor weight after exposure to X radiation. These results suggest that in radiation therapy one of the factors involved in radiosensitivity may be the expression of MT in certain tumors.

Topics: Alkynes; Animals; Enzyme Inhibitors; Fibrosarcoma; Glycine; Male; Metallothionein; Mice; Mice, Inbred BALB C; Mice, Inbred Strains; Radiotherapy Dosage; X-Rays; Zinc Sulfate

The expression of metallothionein (MT) in certain tumor cells has been associated with resistance to anticancer drugs. In the present study, we examined the effects of inhibition of MT synthesis on resistance to anticancer drugs of human bladder tumor which were inoculated in nude mice. The results show that pretreatment of tumor-bearing mice with zinc salts increased MT content, both in normal and tumor tissues, with a marked reduction in the antitumor activity of cisplatin, Adriamycin, and melphalan. Injection of propargylglycine, an inhibitor of cystathionase, decreased MT induction by zinc in the tumor and diminished the resistance to these drugs. These results suggest a role for MT in drug resistance in tumors, and injection of propargylglycine may provide a potential means to overcome drug resistance caused by elevation of MT levels in certain tumors.

Topics: Alkynes; Animals; Cisplatin; Colonic Neoplasms; Cysteine; Doxorubicin; Drug Resistance; Female; Fibrosarcoma; Glycine; Humans; Male; Melphalan; Metallothionein; Mice; Mice, Inbred BALB C; Mice, Inbred ICR; Mice, Nude; Pargyline; Sulfates; Tumor Cells, Cultured; Urinary Bladder Neoplasms; Zinc Compounds; Zinc Sulfate

Metallothionein (MT) shows a protective effect against toxic actions of some antitumor drugs and gamma-irradiation in animals. Preadministration of bismuth subnitrate, an MT inducing drug, significantly reduced side effects of antitumor drugs without affecting antitumor activity of the drugs. This specific effect of bismuth on the toxicity of antitumor drugs appears to be attributable to its specific induction of MT in normal tissues, but not in tumor tissue. Preinduction of MT synthesis in the lung also prevented mice from carcinogenesis caused by cisplatin and melphalan in the lung. On the other hand, zinc compound induced MT synthesis in the tumor, and significantly suppressed the antitumor activity of some antitumor drugs. Propargylglycine (PPG), an inhibitor of cystathionine pathway, significantly inhibited MT induction by zinc in the tumor inoculated in mice, and, consequently, PPG could diminish cisplatin resistance acquired by an increase in the tumor MT levels.

Topics: Alkynes; Animals; Antineoplastic Agents; Bismuth; Cisplatin; Drug Resistance; Female; Glycine; Lung Neoplasms; Melphalan; Metallothionein; Mice; Neoplasms, Experimental; Pargyline

The role of metallothionein (MT) in cisplatin (cis-DDP) resistance and renal toxicity was investigated in C3H mice inoculated with mouse bladder tumor (MBT-2). C3H mice were inoculated s.c. with 1 x 10(6) MBT-2 cells/mouse on day 0. Mice were given injections of proparglyglycine (PPG) (500 mumol/kg s.c.) once a day for 3 days from day 7 to day 9 and with ZnSO4 (200 mumol/kg s.c.) once a day for 2 days from day 8 to day 9. cis-DDP (50 mumol/kg i.p.) was administered 10 days after MBT-2 cell inoculation. Since MT contents in the tumor and kidneys were significantly increased by administration of ZnSO4, both the antitumor activity of cis-DDP and its renal toxicity were reduced. However, coadministration of PPG reduced MT induction in tumor without affecting the level of renal MT. As a result, PPG could clearly overcome the MT-mediated cis-DDP resistance of tumors without compromising the protective effect exerted by renal MT on nephrotoxicity of the drug. It was suggested, therefore, that PPG may be a promising adjunct in cancer chemotherapy to overcome the drug resistance of tumors caused by the elevated level of MT.

Topics: Alkynes; Animals; Cisplatin; Cystathionine gamma-Lyase; Drug Resistance; Female; Glutathione; Glycine; Kidney; Metallothionein; Mice; Mice, Inbred C3H; Neoplasm Transplantation; Pargyline; Sulfates; Urinary Bladder Neoplasms; Zinc; Zinc Sulfate

Metallothionein (MT) and glutathione (GSH) both contain 30% cysteine and they have distinct developmental profiles in perinatal rat liver. The metabolic relationships between these two cysteine pools were investigated in newborn rats under various experimental conditions. Injection of 2-day-old rat pups with buthionine sulfoximine, phorone or diethylmaleate decreased hepatic GSH levels without any change in high basal levels of MT or zinc. Similarly injection of L-oxothiazolidine carboxylate increased hepatic GSH levels but no changes in MT or zinc levels were observed. Administration of buthionine sulfoximine in drinking water to pregnant rats from day 14 of gestation decreased hepatic GSH concentrations in both the dams and pups with little change observed in neonatal hepatic zinc and MT levels or in gamma-glutamyltranspeptidase activity. The induction of MT synthesis by zinc salts in newborn rats was not affected by the in utero reduction of GSH levels. Although maternal hepatic GSH levels can be decreased by a sulfhydryl-deficient diet, no changes were observed in GSH, MT or zinc levels in newborn rat liver. Reduction of perinatal hepatic MT levels by in utero zinc deficiency had little effect on GSH levels. However, inhibition of the cystathionase pathway in newborn rats with propargylglycine decreased hepatic levels of MT, zinc and GSH. The results suggest that whereas there is little interaction between these two pools of cysteine, inhibition of cystathionase activity can decrease hepatic concentrations of both GSH and MT.

Topics: Alkynes; Animals; Animals, Newborn; Buthionine Sulfoximine; Cysteine; Female; gamma-Glutamyltransferase; Glutathione; Glycine; Liver; Metallothionein; Methionine Sulfoximine; Pargyline; Pregnancy; Rats; Zinc