Cancer biochemistry biophysics最新文献

The nitrosoureas including BCNU are potent chemotherapeutic drugs and have been used extensively for treatment of brain tumors and other neoplasias but the mechanisms of action for the DNA lesions created and their repair are still unclear. We have recently determined the in vitro repair of BCNU-treated DNA with cellular extracts and with DNA modifying enzymes. BCNU not only caused an increase in breaks in plasmid DNA, but an increase in cross-linked DNA was also observed after restriction enzyme digestion followed by gel electrophoresis. When HeLa cell-extracts were incubated with BCNU-treated DNA, 5-10 fold increases in DNA repair synthesis were observed as compared with untreated control. Substantial increases in 5'OH and 3'OH sites of the breaks were also found in BCNU-treated DNA as determined by the 10-20 fold increases in labeling with T4-DNA kinase and by endogenous polymerases, while the amount of ligatable sites were at a minimal. When the repair capacity of two glioma cell lines (UWR1 and UWR3) with differential BCNU sensitivity, and cells from a chromosomal breakage disease, Bloom's syndrome (BS), were assessed, the activities of the two glioma cells were about 20-30% of the normal lymphoblastoid cells and HeLa cells, whereas no difference was observed in BS cells. However, differential patterns of DNA bands were observed in the glioma samples suggesting cell-type specific capacities of repair synthesis. These data are in accordance with the concept that BCNU creates multiple DNA lesions and suggests different cell types may develop a variety of repair capabilities.

We have investigated the efficacy of the Photodynamic Therapy (PDT) from 5-aminolevulinic acid (ALA) in combination with an antineoplastic agent using an in vitro-in vivo model developed in our laboratory. The alkylant cyclophosphamide (CY) was chosen because there is evidence of the porphyrinogenic properties of this drug. Male BALB/c mice bearing a transplantable mammary adenoarcinoma were given two doses of 35 mg de CY/kg wt. i.p. and 9 mg/kg wt intratumorally. At 16, 22 and 40 hrs after the last injection of CY the animals were sacrificed and explants of 2 mg of tumor were incubated 2 hrs in a medium containing 0.6 mM ALA; and then irradiated with a He-Ne laser. Innocula of 1 mm3 of irradiated and non-irradiated tissue were then injected subcutaneously under the right and left flanks of a normal mouse, respectively. The efficacy of the treatment was determined following the growth of the tumor from day 10 after tumor implantation. Under the present conditions a 30% increased efficacy was observed in the case of the explants treated with CY 40 hrs after the last i.p. injection. Porphyrins in the liver and tumor and other tissues of the injected mice were also determined; except for a slight increase in tumor and liver, 40 and 22 hrs after CY i.p. injection respectively, no other changes were observed in any tissue, as compared with not CY treated mice. These results indicate that future treatment, combining the tumor localizing properties of endogenously formed porphyrins from ALA and antineoplasic drugs such as cyclophosphamide, should be encouraged.

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.

Our findings indicate that sialic acid and fibronectin levels in breast tumors are higher than those in normal tissues. The mean tissue fibronectin and sialic acid concentrations for patients with breast cancer were 30.90 +/- 9.68 microg/mg protein and 21.60 +/- 9.35 microg/mg protein, respectively, and for normal controls were 12.47 +/- 5.69 microg/mg protein, respectively. Tissue fibronectin and sialic acid can be important markers for human breast cancer.

The combined effect of cyclophosphamide and ascorbic acid on plasma lipids and lipoprotein profiles are important since, ascorbic acid encumbered the lipid abnormalities initiated by cyclophosphamide during cancer chemotherapy. Hence, the study was launched to appraise the salutary role of ascorbic acid in cyclophosphamide administered fibrosarcoma bearing rats. Fibrosarcoma cell line induced rats were treated with cyclophosphamide (10 mg/kg body weight) and ascorbic acid (200 mg/kg body weight) individually and in combination for 28 days. The concentration of plasma lipids and lipoprotein profiles were determined in control and experimental animals. The untreated, as well as cyclophosphamide administered fibrosarcoma bearing rats, divulged significantly increased levels of plasma total cholesterol, triglycerides, phospholipids, VLDL- and LDL-cholesterol, as compared with their respective control animals. In contrast, ester and HDL-cholesterol levels exhibited a marked decrease in these animals. Similar observations were also noticed in liver lipid values, as well. However, these lipid abnormalities were corrected by the co-administration of ascorbic acid. These results suggested, that some clinical entanglement of cyclophosphamide was refrained by co-administration of ascorbic acid in tumor stress condition.

Activities of adenosine deaminase, 5'-nucleotidase, xanthine oxidase, superoxide dismutase, glutathione peroxidase and catalase enzymes were measured in cancerous and non-cancerous adjacent colorectal tissues from 10 patients. Activities of DNA turn-over enzymes (ADA, 5'NT and XO) were found increased and those of free-radical metabolizing enzymes (SOD, GSH-Px and CAT) decreased in cancerous tissues compared with those of non-cancerous adjacent ones. Malondialdehyde (MDA) concentrations in cancerous tissues were also found higher than those of non-cancerous tissues, which indicated accelerated lipid peroxidation in the cancerous tissues. In the correlation analysis, disordered enzymatical relations were observed between the enzymes of both metabolic pathways. Results suggest that activities of purine metabolizing enzymes increase to cope with accelerated purine metabolism in cancerous tissues and, enzymatic antioxidant defense potential of cancerous tissues decreases due to carcinogenic processes in the tissues. Reduced antioxidant defense system makes the cancerous tissue more vulnerable to toxic effects of some free-radical species.

The activity of uridine kinase (ATP: uridine 5'-phosphotransferase; EC 2.7.1.48), the rate-limiting enzyme of the UMP salvage pathway, was measured in human ovaries and ovarian carcinomas, in a spectrum of six rat hepatomas of different growth rates and in eleven normal rat tissues of high and low cell renewal rates. In a standard isotopic method developed for the 100,000 x g fraction, uridine kinase activity was linear for 20 min and proportional with protein concentration over a range of 0.1 to 0.8 mg per 0.1 ml reaction mixture. The apparent Kms for uridine, ATP and Mg++ in normal rat liver were 5.0, 3.4 and 1.5 mM and in the rapidly growing hepatoma 3924A, 0.8, 2.1 and 1.1 mM, respectively. In normal control ACl/N and Buffalo strain rat livers, kinase activity ranged from 159 to 180 nmol/h/mg protein. In hepatomas of slow and intermediate growth rates, kinase activity increased to 1.5- to 2.6-fold, and in hepatomas of rapid growth rates, to 5.1- to 5.8-fold over that of the relevant control, normal livers. When hepatoma 3924A tissue culture cells were plated and expressed their proliferative program, kinase activity increased to 2.1-fold in early log phase. To further clarify the linkage between uridine kinase and cell replicating capacity, the enzyme activity was measured in rat organs of high and low cell renewal. The kinase activity in liver of adult male Wistar rats was 176 +/- 6 nmol/h/mg protein. Activities in thymus, spleen and bone marrow were 4.7-, 2.1-, and 1.8-fold, respectively, of rat liver values; in adipose tissue, the activities were low. The decay rates of uridine kinase were examined in rats injected with a high dose of cycloheximide, which inhibits protein biosynthesis by 90%. The t(1/2) of the kinase in rat bone marrow was 0.64 h, in rat liver longer than 6 h. In human ovary and ovarian carcinoma, the apparent Kms for uridine were 11.5 and 0.5 mM, respectively. In human ovary (n = 3), kinase activity was 38 nmol/hr/mg protein; in ovarian carcinoma (n = 6), the activity increased to 5- to 13-fold over that in ovary. The positive linkage of uridine kinase activity with proliferation and transformation is apparent in human ovarian carcinomas and in rat hepatomas of different growth rates. Therefore, the increased uridine kinase activity should be an interesting target for anticancer chemotherapy.

This study was to determine the extent of alteration of enolase specific activities in chicken embryo retina primary cells in culture when exposed to an ELF (extremely low frequency) electric field at 60 Hz. Results showed no alteration of enolase activity and enolase mRNA levels. In this study, sham vs. control experiments were also conducted to neutralize ambient AC magnetic fields, stray magnetic fields and variations in field uniformity. Under similar conditions, the specific activity of enolase is decreased in neuroblastoma cell line (NG108). It is apparent from this study that primary cells either are not affected by these exposure conditions or the effect is transient and warrants no damage.

Cultured P388 (murine) and CEM (human) leukemia cells were exposed to medium including either 5-fluorouracil (5-FU) or methotorexate (MTX). The level of drug was less than the ID50 value obtained in RPMI 1640 medium (control). Enhancement of drug cytotoxicity was determined with medium in which asparagine or glutamine level had been reduced to 60% of the level of the control. Proliferation of both types of cells for 3 days showed the cytotoxicities of the drugs. Asparagine reduced medium showed no enhancement of cytotoxicity in comparison with control, while glutamine reduced medium enhanced the cytotoxicity of 5-FU, but not that of MTX. Regulation of extracellular glutamine level seemed to affect stage G1 of the cell cycle, as found in the previous result with adriamycin.