Proteomic analysis of cervical cancer cells treated with suberonylanilide hydroxamic acid.

Suberonylanilide hydroxamic acid (SAHA)is an orally administered histone deacetylase inhibitor (HDACI) that has shown significant antitumour activity in a variety of tumour cells.To identify proteins involved in its antitumour activity,we utilized a proteomic approach to reveal protein expression changes in the human cervical cancer cell line HeLa following SAHA treatment.Protein expression profiles were analysed by 2-dimensional polyacrylamide gel electrophoresis (2-DE) and protein identification was performed on a MALDI-Q-TOF MS/MS instrument.As a result,a total of nine differentially expressed proteins were visualized by 2-DE and Coomassie brilliant blue (CBB) staining.Further,all the changed proteins were positively identified via mass spectrometry (MS)/MS analysis. Of these,PGAM1 was significantly downregulated in HeLa cells after treatment with SAHA. Moreover,PGAM1 has been proven to be downregulated in another cervical cancer cell line (CaSki) by western blot analysis.Together,using proteomic tools,we identified several differentially expressed proteins that underwent SAHA-induced apoptosis. These changed proteins may provide some clues to a better understanding of the molecular mechanisms underlying SAHA-induced apoptosis in cervical cancer.

La telomerasa: una enzima con múltiples aplicaciones en la investigación del cáncer / Telomerase: an enzyme with multiple applications in cancer research

The telomerase is a ribonucleoprotein enzyme to which multiple functions have been attributed, the most important of these is the maintenance of the telomere which is related with cellular immortalization and cancer. 85 of human tumors have telomerase activity, that in normal cells goes undetected. These characteristics make the telomerase an attractive target for chemotherapy.

Effects of antiproliferative protein [APP] on modulation of cytosolic protein phosphorylation of prostatic carcinoma cell line LNCaP

Antiproliferative protein [APP] isolated from conditioned media of two androgen-independent prostatic carcinoma cell lines, PC3 and Du-145 was shown to inhibit selectively cell proliferation of androgen-dependent prostate cancer cell line LNCaP in a dose dependent manner. This protein was further purified with HPLC using hydrophobic interaction column [phenyl 5PW] and was used to study the modulation of protein phosphorylation of LNCaP cells. The data indicated that antiproliferative protein could partially change the cytosolic protein phosphorylation. When compared with control LNCaP cells, in APP-treated cells 4 new proteins [88, 46, 30 and 18 kDa] were phosphorylated, while a 72 kDa phosphoprotein was de-phosphorylated. The same results were obtained when two types of protein kinase activators were used. Protein kinase activators showed that the above changes of protein phosphorylation are not due to the protein kinase C or DNA protein kinase activity. These data may indicate the inhibition of LNCaP cell's proliferation by APP may be is due to the modulation of protein kinases and as a result due to interference on second messenger pathway

A novel 200 kDa plasma membrane glycoprotein with high basal tyrosine kinase activity in tumour cells.

We have detected a tyrosine phosphorylated 200 kDa glycoprotein (gp200) on the surface of two tumour cells of neural origin, namely A1235 glioma and A172 glioblastoma. gp200 (polypeptide mass of 165-170 kDa) has all the structural features of a growth factor receptor and it appears to display high basal tyrosine kinase activity, a characteristic associated with transforming proteins. Another interesting feature of gp200 is that it is immunologically highly related to the EGF receptor (polypeptide mass of 135 kDa), a member of the erb-B family of proteins; however, it lacks EGF binding activity. gp200 also differs from all other EGF-receptor-related oncogenic proteins, namely erb-B-2, erb-B-3 and erb-B-4 gene products, and hence appears to be yet another member of the erb-B family of proteins. This is further strengthened by the fact that both gp200 and the EGF receptor are also recognized by a conformation-specific anti-peptide antibody to the cytoplasmic domain of the beta-type PDGF receptor. In the EGF- and the PDGF receptors, this peptide epitope is cryptic and receptor phosphorylation unmasks this site [Panneerselvam K, Reitz H, Khan S A, and Bishayee S (1995) J Biol Chem 270, 7975-7979] indicating that this epitope might be important in biological message transmission. In this context, the expression of a novel EGF-receptor-related 200 kDa protein with high basal kinase activity in certain tumour cells of neural origin and the fact that it contains an important peptide epitope suggest its possible role in normal and abnormal cell growth.

Properties of single-stranded DNA-binding proteins (SSB-proteins) from chromatin and nonchromatin fractions of Ehrlich ascites tumour: phosphorylation enhances the affinity of SSB-proteins for single-stranded DNA.

To assess the possible functional role of single-strand DNA-binding (SSB) proteins in eucaryotic cell, a comparative study was made of SSB-proteins isolated from chromatin and the nonchromatin fractions of Ehrlich ascites tumour (EAT) cells. No appreciable differences between the two groups could be found either in SDS-gel electrophoretic patterns or in the ssDNA-binding capacity and stimulation of DNA replication in permeable EAT cells. However, the chromatin SSB-proteins incorporated 1.4-times more labelled phosphate in vivo; phosphate assays in the isolated chromatin and nonchromatin SSB-proteins yielded ca. 3 and 2 moles Pi/mole protein, respectively. Both preparations could be further phosphorylated in vitro with Ca-phospholipid-dependent protein kinase and the catalytic subunit of cAMP-dependent protein kinase, but the non-chromatin proteins were phosphorylated to a greater degree. In parallel with phosphorylation, the SSB-proteins displayed stronger binding to ssDNA cellulose. Phosphorylation may thus be a means of regulating the functions of SSB-proteins, in particular their interaction with chromatin.

Mechanism of host cell membrane modification by tumour: a model for paraneoplastic syndromes.

A not well-appreciated but clinically important aspect of malignant tumours is their effects on distantly located host cells. The effects, termed paraneoplastic syndromes, also pose an intriguing mechanistic problem: how do malignant cells influence properties of host cells not in contact with them? Erythrocytes from the circulation of rats bearing intraperitoneal Yoshida ascites sarcoma exhibit higher agglutinability with concanavalin A (Con A) than the cells from normal animals. Since the tumour and the red cells are not in contact, the enhanced agglutinability of the latter is a paraneoplastic effect. The mechanism by which the tumour brings about this effect is investigated as a model for paraneoplastic syndromes. The cell-free ascites fluid is able to impart high agglutinability on cells from normal animals in vitro. Also, when injected intraperitoneally in normal animals, the ascites fluid is able to enhance the agglutinability of erythrocytes in circulation. Apparently the tumour produces a substance(s) that appears in the ascites fluid and is able to diffuse into circulation, explaining the mechanism by which it can reach distant sites. From the cell-free ascites fluid three fractions have been isolated that are active in vitro. Of these, only one showed activity in vivo. From this fraction, a glycoprotein has been purified to homogeneity that confers maximal Con A-agglutinability on normal erythrocytes at 8 x 10(-7)M, at which concentration 6,400 molecules bind per cell. The protein has a molecular weight of 600 kDa in the native state and a pI of 5.35. It is made up of 4 identical subunits of Mr 170,000. It is detected in the plasma of tumour-bearing but not normal rats.(ABSTRACT TRUNCATED AT 250 WORDS)