Cancer biochemistry biophysics最新文献

The urokinase plasminogen activator (uPA) and tissue plasminogen activator (tPA) are very similar serine proteases with the same physiological function, the activation of plasminogen. An increased amount or activity of uPA but not tPA has been detected in human cancers. The PAs are weak proteolytic enzymes, but they activate plasminogen to plasmin, a strong proteolytic enzyme largely responsible for the malignant properties of cancers. It has been shown recently that the administration of uPA inhibitors can reduce tumor size. Inhibitors of uPA could therefore be used as anti-cancer and anti-angiogenesis agents. It has been found that amiloride competitively inhibits the catalytic activity of uPA but not tPA. Modification of this chemical could therefore produce a new class of uPA specific inhibitors and a new class of anti-cancer agents. The X-ray structure of the uPA complex with amiloride is not known. There are structural differences in the specificity pocket of uPA and tPA. However, the potential energy of binding amiloride is lower outside this cavity in the case of tPA. A region responsible for binding amiloride to tPA has been proposed as the loop B93-B101, reached in negatively charged amino acids present in tPA but not uPA.

In our previous work (Alexandrov et al., 1996) was reported that the rat sarcoma cells induced by SR-RSV express two tumor associated antigens (TAA). The one TAA has a molecular weight of 52 kD and is detected by the help of a monoclonal antibody 2C2 only on the outer side of the plasma membrane of the sarcoma cells. The other antigen, with molecular weight of 28 kD, is expressed on the outher and inner side of the membrane. The antigens were isolated as a pure fraction by polyacrylamide electrophoresis and prepared for aminoacid analysis after that. The consisting 16 bound aminoacids were in different amounts. Both antigens are rich in glycine and poor in aromatic and sulphur-containing aminoacids. The presence of glucosamine and galactosamine in the antigens proves their glycoprotein nature. The received data show that the both TAA-s differ not only in molecular weights, place of expression and functional activity, but also in the amount of the bound aminoacids which constitute their proteins.

Morbidity resulting from the toxicity of chemotherapeutic drugs suggests that novel approaches are worthy of investigation. Development of the use of low intensity magnetic fields as an adjuvant to current treatment regimens to prevent metastatic disease may prove to be efficacious. Using a cell culture model, we have developed a magnetic field (MF) treatment that offers the possibility of lowering the therapeutic dose of these drugs and thereby reducing morbidity. Our studies have found that a low intensity (approximately 2 gauss) MF signal and a relatively low dose (0.1 microg/ml) of Adriamycin (ADR) inhibited proliferation of human osteosarcoma cells by 82%, whereas the MF and ADR acting individually caused only 19% and 44% inhibition, respectively.

Chemically induced and spontaneous liver tumors share some metabolic alterations. The decline in hemoprotein levels during hepatocarcinogenesis may result from a diminution of the intracellular heme pool. To elucidate if the onset of the pre-initiation stage alters the natural regulation mechanism of heme pathway, animals were fed with p-dimethylaminoazobenzene (DAB) and treated or not with 2-allylisopropylacetamide (AIA). The induction of 6-Aminolevulinic acid synthase (ALA-S) activity and the diminution in microsomal heme oxygenase (MHO) did not change when DAB fed animals were treated with AIA. Cytochrome P-450 (P-450) levels and glutathione S-transferase activity were increased in all the groups tested. Tryptophan pyrrolase, sulphatase and beta-glucuronidase activities were altered in DAB fed animals but AIA treatment did not produce any effect. Changes in drug metabolizing enzymes in livers of DAB fed animals could be the result of a primary deregulation of heme metabolism. These results give additional support to our hypothesis about a mechanism for the onset of hepatocarcinogenesis.

The arginase activity and ornithine level were determined in tissue obtained from patients with non-small cell lung carcinoma (NSLC). The arginase activity and ornithine level in tumor tissues were 1.89 +/- 1.28 U/mg protein and 42.32 +/- 25.82 nmol/mg protein, respectively versus 0.67 +/- 0.19 U/mg protein and 10.12 +/- 3.69 nmol/mg protein for normal tissues (p < 0.01).

Lysosomal cysteine proteinases (cathepsins) are considered to play a role in bone degradation mediated by metastatic breast cancers. To evaluate which cathepsin contributes to the osteolysis, we quantitatively determined the expression levels of four cathepsins in two breast cancer cell lines, MCF-7 and MDA-MB-231, by competitive RT-PCR. Cathepsin K, which is the most abundant cathepsin in osteoclasts, was not detected in either cell lines. We also failed to detect cathepsin H mRNA. By contrast, we found significant expression of cathepsins B and L in both cell lines. By Northern blot analysis cathepsin B mRNA was detected in a single form in these cells, whereas osteoclasts contained multiple forms of the mRNA. Cathepsin B protein was also detected by Western blotting as a single immunoreactive band corresponding to its mature enzyme. These findings suggest that osteolysis associated with metastatic breast cancers takes place in a different way from osteoclast-mediated bone resorption.

We analyzed lactoferrin expression in 78 samples from patients with sporadic breast cancer and found 31/78 negative for mRNA expression. Similar results were obtained by immuno-histochemical localization of the lactoferrin protein. We did not find relationship between lactoferrin expression and clinical parameters. We investigated for the absent lactoferrin expression in some cases of breast cancer. In 68 of the samples analyzed, we found an inverse correlation between estrogen receptor expression and lactoferrin expression (P < 0,0001), thus indicating that regulation by the estrogen receptor is not the main element responsible for the expression of lactoferrin in breast cancer. Analysis of methylation of the lactoferrin genomic DNA extracted from the same patients revealed that the degree of methylation does not explain the observed absence of lactoferrin. The 937 bp lactoferrin promoter was investigated for possible mutations. By single-strand conformation polymorphism analysis one polymorphic site was found and characterized.

The expression of mdm-2 oncoprotein (p90) was determined in a human breast tumor xenograft line (GI-101) that was derived from a 57 year old female cancer patient with recurrent, infiltrating ductal adenocarcinoma (Stage IIIa, T3N2MX). Immunoprecipitation coupled western blot analysis of the primary tumors that have been obtained from xenograft implanted athymic nude mice, using mdm-2 (Ab-1) mouse monoclonal antibody, primarily revealed high level expression of a 90 kD full length mdm-2 protein. In the GI-101 tumor the level of full length mdm-2 (p90) protein expression increased with the increase in the size of the tumor (100 to 2,000 mm(3)) and a maximum expression was detected in 2,000 mm(3) size tumors. In addition to the expression in the primary site, a significantly high level expression of mdm-2 protein (p90) was detected in the lung and liver tissues also, which are the known metastatic sites for GI-101 xenograft tumors. However, the level of mdm-2 protein expression was undetectable in the lung and liver tissues obtained from control mice. A cell line (GI-101A) derived from the GI-101 xenograft tumor also showed a high level expression of mdm-2 protein after several generations of cell passage. When the GI-101A cells were treated with DES (Diethylstilbestrol) the mdm-2 protein expression increased after 10 min treatment and reached a peak level at 40 min. Interestingly, DES (10 and 20 microM) treatment increased the total cell number also after 96 hr treatment compared to the non-treated cells. It appears that mdm-2 (p90) may have a significant role in supporting the tumor cell growth as well as the metastatic process of the GI-101A cells.

MUC1 is a glycoprotein and its expression is altered in breast cancer. Mucin protects epithelia from the external hostile environment. The expression of mucin changes when epithelia come in contact with toxic agents such as ethanol. Previously, we characterized the expression and regulation of tracheo-bronchial mucin (TBM) gene. In the present study, we studied the effect of ethanol on the gene encoding mammary gland mucin MUC1 and observed that ethanol regulates MUC1 expression at the transcription level. Ethanol enhanced the expression of MUC1 mRNA in a dose- and time-dependent manner in MCF-7 cells. At 100 mM concentration (a concentration reported to be present in alcoholics), ethanol induced a three to five-fold increase in mucin transcription as determined by nuclear run on analysis. This concentration of ethanol does not affect the half-life of MUC1 mRNA.

The modulating effect of newly synthesized alkylating spin labeled triazene and spin labeled nitrosourea derivatives on the DOPA-oxidase activity of mushroom tyrosinase has been investigated by Bumett's spectrophotometric method (Burnett et al., 1967). All spin labeled triazenes have exhibited activating effect on DOPA-oxidase activity of tyrosinase, whereas clinically used triazene (DTIC), which does not contain nitroxide moiety, have showed inhibiting effect. At the same experimental conditions the spin labeled aminoacid nitrosoureas have showed dual effect - activating, in the beginning of the enzyme reaction and inhibiting later on. It is deduced that the activating effect of the spin labeled compounds is due to the nitroxide moiety and the inhibiting effect of all compounds depends on their half-life time. This study might contribute to make more clear the mechanism of action of the new compounds and on the other hand would come in quite useful as a preliminary prognosis for their antimelanomic activity.