Cancer biochemistry biophysics最新文献

P-glycoprotein (P-gp), a plasma membrane glycoprotein associated with the multidrug resistance phenotype, is responsible for the ATP-dependent efflux of various amphiphilic drugs. Using membrane vesicles prepared from the multidrug resistant cell line DC-3F/ADX, we studied the perturbation of the basal (i.e. in the absence of drug) and verapamil-dependent P-gp ATPase activities induced by various detergents, at non-solubilizing, as well as at solubilizing, concentrations. The progressive membrane solubilization with increasing detergent concentration was monitored by light scattering and centrifugation experiments. For non-solubilizing detergent concentrations, all tested detergents except DOC induced a partial inhibition of P-gp ATPase activity, which was not correlated with the amount of the various tested detergents incorporated in the membranes. Analysis of the verapamil-induced P-gp activation reveals that P-gp ATPase activity is differently modulated by the various detergents at non-solubilizing concentrations. Thus, specific interactions between P-gp and detergents are more likely to occur rather than a global membrane perturbation. After solubilization by the various tested detergents, the basal P-gp ATPase activity was virtually completely inhibited, except in the presence of CHAPS which was able to preserve this activity at a level comparable to that measured in native membranes. However, the verapamil-induced P-gp ATPase activation was lost during P-gp solubilization by CHAPS, but recovered after dilution of CHAPS below its critical micellar concentration. These observations indicate specific interactions between P-gp and CHAPS molecules within the mixed micelles. On the whole, our data evidencing specific interactions P-gp/detergents are consistent with the location of the drug transport sites on P-gp transmembrane domains.

The study was carried out on 25 women with breast cancer, 25 with fibrocystic breast disease and 19 healthy subjects. Antioxidant enzyme activities and total antioxidant status (AOX) were measured in erythrocyte and plasma of patients and healthies. Among the studied parameters, the erythrocyte Glutathione Peroxidase (GSH-Px) and Catalase (CAT) activities of patients with breast cancer were significantly different as compared to the control group values (p < 0.002 and p < 0.001) respectively. There was no correlation between total antioxidant status and any of these enzymes in erythrocyte and plasma activities of subjects. However, the positive correlation was found between erythrocyte and plasma Superoxide Dismutase [SOD(CuZn)] activities in all groups. Our results indicate that enzymatic and nonenzymatic antioxidants are differentially altered in human breast tumors. Since the total antioxidant status measurement isn't sufficient to evaluate the oxidant damage in breast disease, antioxidant enzymes must be measured separately in order to get additional information.

Using a method based on [3H]tamoxifenaziridine ([3H]TAZ) labeling, sequential immunoadsorption with anti-ER monoclonal antibodies, sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE) and fluorography, we observed a striking change inthe estrogen receptor (ER) electrophoresis pattern of the transplantable MXT mouse mammary tumor. Early, ER "rich" tumors (approximately 100 fmol/mg prot) displayed classical cytosolic 67 and 50 KDa bands. These bands disappeared in favor of a "cytosolic" 35 KDa band during progression towards undifferentiated ER "poor" tumors (approximately 25 fmol/mg prot). Although we can not rule out that this 35 KDa peptide results from in vivo ER proteolysis, it seems unique in view of the following: 1. It is immunoadsorbed not only by an anti-ER monoclonal antibody (H-222) directed to the hormone-binding domain, but also by an anti-ER monoclonal antibody (H-226) which interacts with an epitope in the A/B region close to the DNA-binding domain and is mainly exposed under activation conditions. 2. It does not bind [3H]estradiol([3H]E2) and a tentative to restore its [3H]E2 binding capacity with calmodulin and ATP was unsuccessful. The observation of similar approximately 35 KDa ERs in the nuclear fraction of early tumor transplants and in control uterus suggests that this peptide is already in an activated form. Structural alterations of ER and/or associated "anchorage" nuclear proteins may beat the origin of its cytosolic localization. Moreover, the fact that the addition of calmodulin and ATP to late MXT transplants cytosols fails to increase their [3H]E2 binding capacity indicates that the low ER content of these tumors does not result from a deficiency in the phosphorylation status of the receptor.

Studies have described the protective role of vitamin C (ascorbic acid) in certain types of cancer. In this study, we report the effects of vitamin C treatment of two androgen independent prostate cancer cell lines from human (PC3) and rat (Mat-Ly-Lu or MLL) sources. In vitro treatment of PC3 and MLL with sodium ascorbate acid (0-10 mM) resulted in a decrease in cell viability and thymidine incorporation into DNA. These effects of vit. C were dose and time dependent. Ascorbate induced these changes through the production of hydrogen peroxide since addition of catalase (100-300 units/ml), an enzyme that degrades hydrogen peroxide, inhibited the effects of ascorbate on these cell lines. In contrast, superoxide dismutase, an enzyme that dismutates superoxide and generates hydrogen peroxide did not prevent ascorbate-induced changes emphasizing the involvement of reactive oxygen species (ROS) in cellular damage. That singlet oxygen scavengers such as sodium azide and hydroquinone, hydroxyl radical scavengers such as D-mannitol and DL-alpha-tocopherol did not counteract the effects of ascorbate on thymidine incorporation suggests that these free radicals are not involved in cellular damage. In conclusion, these results suggest that vitamin C inhibits tumor growth by virtue of producing reactive oxygen species. These results suggest that ascorbate is a potent anticancer agent for prostate cancer cells.

While cancer drug resistance has been extensively studied in cell culture, little is known about more clinically relevant in vivo resistance. The in vivo resistance of a murine mammary carcinoma EMT-6 to alkylating agents was demonstrated in the present study to be associated with multiple biochemical changes. These included an up to 1.5-fold increase in activity of phase II drug metabolizing enzymes (DMEs), such as glutathione (GSH), glutathione reductase (GR), glutathione S-transferase (GST), glutathione peroxidase (GPX) and aldehyde dehydrogenase (ALDH), and an up to 88% decrease of phase I DME activity [7-ethoxycumarin O-deethylase (ECOD), P450 reductase (PR)] in the resistant tumors compared with the parental tumor. Transplant of either parental or resistant tumors to mice was accompanied by a decrease of both phase I and phase II DME activity in the livers of female Balb/C mice compared with the non-tumor mice. Moreover, at the protein level, while cytochrome P450 (CYP) IIB1/2 in the liver of mouse bearing both the sensitive and the resistant tumor was significantly diminished compared to that in the liver of non-tumor control mouse in Western analysis, there was actually an increase of this protein in the liver of the host bearing either of the two resistant tumors compared to that of the sensitive tumor-bearing animal. Although this in vivo resistance phenotype is not expressed in cell culture, the profile of most of the enzyme changes in the resistant tumors remained similar in in vitro culture of the isolated tumor cells. Collectively, these results demonstrate that this in vivo alkylating agent resistance is associated with multiple changes of both phase I and phase II DMEs in the resistant tumors, and some of these, such as CYP IIB1/2 protein are further altered in the resistant tumor-bearing mouse liver, suggesting a potential role of systemic factors in this resistance phenotype.

The present study describes the production of a synthetic hexapeptide (DTRPAP)-based anti-mucin (MUC-1) antibody, similar to those produced using either the intact mucin antigen or tumor extracts. This antibody was generated by immunization of rabbits with the synthetic peptide conjugated to bovine serum albumin as a carrier. Using both the ELISA and FACS analysis methods, we have shown that the antibody is reactive with human ovarian and breast cancer cells, but not with normal epithelial breast cells. This antibody is different from the previously reported anti-mucin HMFG-1, HMFG-2 and SM-3 monoclonal antibodies, since competitive experiments with the free synthetic peptide revealed only a 30% inhibition of HMFG-1 binding to the ovarian (OVCAR-3) cancer cells, as compared to 78% inhibition of the anti-synthetic peptide antibody. The peptide was non-inhibitory for HMFG-2, and induced a significant and reproducible stimulation of the SM-3 binding activity to the tumor cells.

Wool fatty alcohols (WF-Alc; C10-C33), separated by esterolysis of wool grease secreted from sheep sebaceous gland, inhibited growth of mouse Ehrlich ascites carcinoma (EAC) cells in contrast to no inhibition by unesterolysed wool grease. WF-Alc was fractionated by molecular distillation and subsequent octadecylsilica (ODS) gel liquid chromatography, showing that most of the growth-inhibitory activity was found in the most hydrophilic fraction with the lowest boiling-point (MW 200-300; C12-C20), ODS-HPLC of the fraction showed that most of the activity resided in two homogeneous fractions identified by GC-MS and 13C-/1H-NMR as alpha, beta-dihydric saturated fatty alcohols such as 1,2-hexadecanediol (n-C16(OH)2) and 16-methyl-1,2-heptadecanediol (iso-C18(OH)2), respectively. EAC cells implanted into mice were inhibited markedly by n-C16(OH)2 possessing a cytolysing ability and slightly by iso-C18(OH)2, but hardly by other alkyl-alpha, beta-diols (C12-C24) contained in WF-Alc. Thus, the antitumor activity of WF-Alc was exhibited only after saponification of uncytotoxic wool grease, showing necessity of unesterified hydroxyl groups, and was dependent upon the molecular hydrophobicity balance attributed to both hydroxyl groups and n- or iso-alkyl moiety bulkiness specified out of diverse species of fatty alcohols contained in WF-Alc.

The precise excision of intervening sequences during RNA splicing is an interesting example of the high degree of specificity involved in biosynthesis processes. Self-splicing RNA precursors achieve this specificity primarily through intramolecular interactions whereas all other types of RNA splicing requires interaction between cellular factors and specific recognition signals in the RNA precursor. About twelve years ago, the in vitro splicing system was developed and a general scheme of the pre-mRNA was proposed (Hernandez and Keller, 1983; Krainer et al., 1984; Lin et al., 1985; Padgett et al., 1984; Ruskin et al., 1984). A fundamental question in the splicing field is how the 5' and 3' splice sites are recognized and paired during the splicing reaction. Recent work in the splicing field has established that a network of RNA interactions may form the structural foundation of the spliceosomes. Possible solutions to many unsolved puzzles are getting attention. RNA-RNA interactions now appear to underlie many aspects of substrate recognition, reaction partner juxtaposition and catalysis. In this article we have presented the latest mechanisms involved in the pre-mRNA splicing and their implication in applied research including cancer.

The effect of high pressure on the viability of Ehrlich ascites tumor cells was examined. The tumor cells were subjected to various pressures (0.1-150 MPa) for 30 min at 37 degrees C. The viability of pressure-treated cells was examined by the dye exclusion method. The number of stained cells increased significantly at pressures above 130 MPa. In addition, the pressure-treated cells were intraperitoneally inoculated into the mice. The tumor cells which were subjected to pressures below 110 MPa proliferated in the peritoneal cavity of the mice, so that the mice died. In contrast, the mice, which were inoculated with the tumor cells treated at pressures above 130 MPa, remained alive. These results suggest that the destruction of the tumor cells begins to occur at about 130 MPa.

Rhodanese (thiosulphate:cyanide sulphurtransferase) shows distinctive mitochondrial and cytoplasmic activities in several models of tumorigenesis. To investigate the basis for these differences, the enzyme was purified from mitochondrial and cytosolic liver fractions of mice treated with the carcinogen p-dimethyl-aminoazobenzene (DAB) and some inhibition kinetic studies were carried out. When both substrates were assayed at inhibitory levels, non-competitive inhibition was observed for the second substrate at variable concentrations, the reversible connection between both substrates was attained by the instability of the second enzyme form. It is suggested that the enzyme might be changing from an unstable ES form to a more stable sulphur substituted intermediate as a consequence of DAB treatment. Sulphite was a competitive inhibitor vs thiosulphate for rhodanese isolated from normal liver and a hyperbolic activator for the enzyme isolated from liver of DAB-treated animals.