Differential tissue-specific protein markers of vaginal carcinoma

The objective was to identify proteins differentially expressed in vaginal cancer to elucidate relevant cancer-related proteins. A total of 16 fresh-frozen tissue biopsies, consisting of 5 biopsies from normal vaginal epithelium, 6 from primary vaginal carcinomas and 5 from primary cervical carcinomas, were analysed using two-dimensional gel electrophoresis (2-DE) and MALDI-TOF mass spectrometry. Of the 43 proteins identified with significant alterations in protein expression between non-tumourous and tumourous tissue, 26 were upregulated and 17 were downregulated. Some were similarly altered in vaginal and cervical carcinoma, including cytoskeletal proteins, tumour suppressor proteins, oncoproteins implicated in apoptosis and proteins in the ubiquitin–proteasome pathway. Three proteins were uniquely altered in vaginal carcinoma (DDX48, erbB3-binding protein and biliverdin reductase) and five in cervical carcinoma (peroxiredoxin 2, annexin A2, sarcomeric tropomyosin kappa, human ribonuclease inhibitor and prolyl-4-hydrolase beta). The identified proteins imply involvement of multiple different cellular pathways in the carcinogenesis of vaginal carcinoma. Similar protein alterations were found between vaginal and cervical carcinoma suggesting common tumourigenesis. However, the expression level of some of these proteins markedly differs among the three tissue specimens indicating that they might be useful molecular markers.

Protein expression patterns in primary carcinoma of the vagina

Protein patterns in six samples from primary vaginal cancers, in five from normal vaginal tissue and in five primary cervical cancers, were analysed using two-dimensional polyacrylamide gel electrophoresis (2-DE). Protein expression profile was evaluated by computer-assisted image analysis (PDQUEST) and proteins were subsequently identified using matrix-assisted laser desorption/ionisation mass spectrometry. The aim was to analyse the protein expression profiles using the hierarchical clustering method in vaginal carcinoma and to compare them with the protein pattern in cervical carcinoma in order to find a helpful tool for correct classification and for increased biomedical knowledge. Protein expression data of a distinct set of 33 protein spots were differentially expressed. These differences were statistically significant (Mann-Whitney signed-Ranked Test, P<0.05) between normal tissue, vaginal and cervical cancer. Furthermore, protein profiles of pairs of primary vaginal and cervical cancers were found to be very similar. Some of the protein spots that have so far been identified include Tropomyosin 1, cytokeratin 5, 15 and 17, Apolipoprotein A1, Annexin V, Glutathione-S-transferase. Others are the stress-related proteins, calreticulin, HSP 27 and HSP 70. We conclude that cluster analysis of proteomics data allows accurate discrimination between normal vaginal mucosa, primary vaginal and primary cervical cancer. However, vaginal and cervical carcinomas also appear to be relatively homogeneous in their gene expression, indicating similar carcinogenic pathways. There might, further, be a possibility to identify tumour-specific markers among the proteins that are differentially expressed. The results from this study have to be confirmed by more comprehensive studies in the future.

Proteome analysis enables separate clustering of normal breast, benign breast and breast cancer tissues

We have used proteomics with cluster analysis for the classification of breast tumour tissues. In our approach, we can distinguish between normal breast, benign breast and breast cancer tissues on the basis of the protein expression profiles. We propose an objective method for the classification of breast tumour specimens.

Identification of proteins in human prostate tumor material by two-dimensional gel electrophoresis and mass spectrometry

Protein patterns in cells collected from benign prostatic tissues and prostate carcinomas were analyzed using two-dimensional polyacrylamide gel electrophoresis and mass spectrometry. Polypeptide expression was evaluated by computer-assisted image analysis (PDQUEST). Proteins expressed by prostate tumors were identified via in-gel digestion and subsequent matrix-assisted laser desorption/ionization mass spectrometry. In addition to cytoskeletal and mitochondrial proteins, a 40-kDa protein was identified as prostatic acid phosphatase (PAP). PAP expression decreased approximately twofold between benign and malignant tissue. Increased expression of heat shock protein 70 and decreased expression of tropomyosin 1 were also observed in the malignant tissue. The analysis of prostate material by two-dimensional gel electrophoresis and mass spectrometry shows that particular proteins are of interest as markers of disease.

Identification of foetal brain proteins by two-dimensional gel electrophoresis and mass spectrometry comparison of samples from individuals with or without chromosome 21 trisomy

Protein expression in foetal brain with or without chromosome 21 trisomy (Down's syndrome) was analyzed by two-dimensional gel electrophoresis and mass spectrometry. Data generated by in-gel digestion and matrix-assisted laser desorption/ionization mass spectrometry allowed identification of 40 proteins. Most of these are common to syndrome and healthy subjects and represent different types of protein. However, a few proteins, identified as truncated structural proteins (tubulin, actin), were present in part of the trisomy samples but absent from the controls. This is interpreted to indicate increased proteolysis in the syndrome samples but could also reflect some altered expression or processing. Independent of the apparently increased proteolysis in the syndrome samples, and in spite of the use of total brain tissues, the results show that two-dimensional protein separation patterns are largely similar between the syndrome and control samples upon silver-staining, but that differences associated with structural components can be detected and identified.

Inhibition of extracellular signal-regulated kinase 1/2 activity of the breast cancer cell line MDA-MB-231 leads to major alterations in the pattern of protein expression

Biochemical and genetic strategies have implied that aberrant signaling in the extracellular signal-regulated kinase (ERK)/mitogen-activated protein (MAP) kinase pathway contributes significantly to transformed phenotypes. Using PD98059, an inhibitor of the ERK-kinase MEK1, we have here assessed the effects of ERK inhibition on the pattern of protein expression in the metastatic human breast cancer cell line MDA-MB-231. At a concentration of inhibitor which did not significantly affect cell growth, PD98059 induced large changes in the expression of MDA-MB-231 polypeptides. The majority of these changes were due to decreased expression of low-abundance proteins. Decreases of more abundant proteins such as glutathione-S-transferase pi, hsp80 and hsp100 were also recorded. The levels of a few proteins increased, among them cytokeratin 8. We conclude that PD98059 treatment of MDA-MB-231 cells induces large changes in protein expression.

Cancer proteomics: from identification of novel markers to creation of artifical learning models for tumor classification

Studies of global protein expression in human tumors have led to the identification of various polypeptide markers, potentially useful as diagnostic tools. Many changes in gene expression recorded between benign and malignant human tumors are due to post-translational modifications, not detected by analyses of RNA. Proteome analyses have also yielded information about tumor heterogeneity and the degree of relatedness between primary tumors and their metastases. Results from our own studies have shown a similar pattern of changes in protein expression in different epithelial tumors, such as decreases in tropomyosin and cytokeratin expression and increases in proliferating cell nuclear antigen (PCNA) and heat shock protein expression. Such information has been used to create artificial learning models for tumor classification. The artificial learning approach has potential to improve tumor diagnosis and cancer treatment prediction.

Cancer proteomics: from identification of novel markers to creation of artifical learning models for tumor classification

Studies of global protein expression in human tumors have led to the identification of various polypeptide markers, potentially useful as diagnostic tools. Many changes in gene expression recorded between benign and malignant human tumors are due to post-translational modifications, not detected by analyses of RNA. Proteome analyses have also yielded information about tumor heterogeneity and the degree of relatedness between primary tumors and their metastases. Results from our own studies have shown a similar pattern of changes in protein expression in different epithelial tumors, such as decreases in tropomyosin and cytokeratin expression and increases in proliferating cell nuclear antigen (PCNA) and heat shock protein expression. Such information has been used to create artificial learning models for tumor classification. The artificial learning approach has potential to improve tumor diagnosis and cancer treatment prediction.

Classification of human ovarian tumors using multivariate data analysis of polypeptide expression patterns

Large amounts of data on quantitative gene expression are generated by procedures such as 2-DE analysis of proteins or cDNA microarrays. Quantitative molecular variation may potentially be used for the development of methods for the classification of tumors. We used here the statistical concepts of principal components analysis (PCA) and partial least square analysis (PLS) in an attempt to type ovarian tumors. Using a set of 170 polypeptides, 22 tumors were used to establish a model ("learning set") for classification into 3 groups (benign/borderline/malignant). Eighteen tumors were then used to test the model. Six of 8 carcinomas and 3 of 4 borderline tumors were correctly classified. Two of 6 benign lesions were correctly classified, 3 were classified as borderline and 1 as carcinoma. We conclude that it may be possible to classify tumors according to their constitutive protein expression profile using multivariate analysis, thus making classification by artificial intelligence a future possibility.

Cancer proteomics: from identification of novel markers to creation of artifical learning models for tumor classification

Studies of global protein expression in human tumors have led to the identification of various polypeptide markers, potentially useful as diagnostic tools. Many changes in gene expression recorded between benign and malignant human tumors are due to post-translational modifications, not detected by analyses of RNA. Proteome analyses have also yielded information about tumor heterogeneity and the degree of relatedness between primary tumors and their metastases. Results from our own studies have shown a similar pattern of changes in protein expression in different epithelial tumors, such as decreases in tropomyosin and cytokeratin expression and increases in proliferating cell nuclear antigen (PCNA) and heat shock protein expression. Such information has been used to create artificial learning models for tumor classification. The artificial learning approach has potential to improve tumor diagnosis and cancer treatment prediction.

Napsin A, a member of the aspartic protease family, is abundantly expressed in normal lung and kidney tissue and is expressed in lung adenocarcinomas

A pair of 35 kDa polypeptides (TAO1/TAO2) are expressed in more than 90% of all primary lung adenocarcinomas but not in other major malignancies. Mass spectrometry of tryptic peptides showed that TAO1/TAO2 is identical to napsin A, a recently described member of the aspartic proteinase family. The site of processing of pronapsin A to the mature form was located. Napsin expression was detected in human lung adenocarcinoma tumors, compatible with the marker nature of TAO1/TAO2 in the diagnosis of primary lung adenocarcinoma. This is important since identification of markers which can distinguish primary lung adenocarcinomas from distant metastases is desirable. Northern blot analysis showed expression of napsin also in normal lung and kidney tissue, and in situ hybridization showed expression in type II alveolar cells of the lung. This protease is concluded to have a specific functional role in the normal alveolar epithelium and is a candidate protease for the proteolytic processing of surfactant precursors.

Two-dimensional gel analysis of protein expression in ovarian tumors shows a low degree of intratumoral heterogeneity

The process of tumor progression leads to the emergence of multiple clones, and to the development of tumor heterogeneity. One approach to the study of the extent of such heterogeneity is to examine the expression of marker proteins in different tumor areas. Two-dimensional gel electrophoresis (2-DE) is a powerful tool for such studies, since the expression of a large number of polypeptide markers can be evaluated. In the present study, tumor cells were prepared from human ovarian tumors and analyzed by 2-DE and PDQUEST. As judged from the analysis of two different areas in each of nine ovarian tumors, the intratumoral variation in protein expression was low. In contrast, large differences were observed when the protein profiles of different tumors were compared. The differences in gene expression between pairs of malignant carcinomas were slightly larger than the differences observed between pairs of benign tumors. We conclude that 2-DE analysis of intratumoral heterogeneity in ovarian cancer tissue indicates a low degree of heterogeneity.

Protein kinase-dependent overexpression of the nuclear protein pirin in c-JUN and RAS transformed fibroblasts

Signalling via the protein kinase Raf-MEK-ERK pathway is of major importance for transformation by oncogenes. To identify genes affected by inhibition of this pathway, c-JUN transformed rat fibroblasts were treated with a MEK1 inhibitor (PD98059) and subjected to two-dimensional gel electrophoresis after cell lysis. Gene products with expression influenced by MEK1 inhibition were determined by mass spectrometry of fragments from in-gel tryptic digestions. The expression of pirin, a nuclear factor I-interacting protein, was lowered after inhibition of MEK1. Western blot analysis revealed increased expression of pirin in RAS and c-JUN transformed cells in the absence of PD98059. Inhibition of MEK1 also led to reduced expression of alpha-enolase, phosphoglycerate kinase, elongation factor 2 and heterogeneous nuclear ribonucleoprotein A3, the latter two being detected as truncated proteins. In contrast, the level of ornithine aminotransferase was increased. We conclude that inhibition of MEK1 results in major alterations of protein expression in c-JUN transformed cells, suggesting that this pathway is important for oncogene-induced phenotypic changes.

Phenotypic analysis of ovarian carcinoma: polypeptide expression in benign, borderline and malignant tumors

Studies of multiple markers in tumors are required for adequate biological characterization. We have characterized the expression of multiple proteins in human ovarian tumors using the technique of 2-dimensional gel electrophoresis (2-DE/PDQUEST). Tumor cells were prepared from the tissue of 22 ovarian tumors. Large variations were observed between tumors in the expression of various polypeptides, indicating heterogeneity in gene expression. An increase in the spot density of 2 cell-cycle-related proteins, PCNA and OP18/stathmin, was observed in carcinomas. Borderline tumors expressed low levels of these proteins. Significant increases in the levels of nm23, GST-pi, elongation factor 2 and triose phosphate isomerase were recorded in ovarian carcinomas. Furthermore, decreases in the levels of tropomyosin-2 and lamin C were observed in malignant as compared with benign tumors. The pattern of expression of 9 protein markers was examined in individual tumors. All malignant tumors showed simultaneous alterations in the expression of 5 or more of these proteins, whereas no benign tumor showed alterations in the expression of more than 3 polypeptides. Borderline tumors showed alterations in 0 to 6 markers. We conclude that the simultaneous analysis of multiple polypeptides, which can be achieved by 2-DE, is useful for characterization of gene expression and diagnostic studies in ovarian tumors.

Increased expression of alpha-enolase in c-jun transformed rat fibroblasts without increased activation of plasminogen

Two-dimensional gel electrophoresis was used to identify polypeptides differentially expressed between normal and c-jun transformed rat fibroblasts. The level of a 49 kDa polypeptide was 3-fold elevated in c-jun transformed cells. Sequence analysis by ion trap mass spectrometry identified the polypeptide as rat alpha-enolase. Enolase functions as a cell surface receptor for plasminogen, suggesting that upregulation may increase plasminogen activation and cell surface proteolysis important for tumor growth. However, no difference was observed between normal and transformed cells in formation of plasmin, suggesting that upregulation of alpha-enolase may contribute to an increased metabolic capacity, but not to increased plasminogen activation.

Biophysical and physiological properties of a modified porcine surfactant enriched with surfactant protein A

Surfactant protein A (SP-A), a major protein component of natural pulmonary surfactant, is absent in exogenous surfactants currently used in clinical practice. We investigated the physical and physiological properties of one of these modified natural surfactants (Curosurf) after enrichment with 5% SP-A (SP-A-Curosurf). A pulsating bubble system was used for in vitro assessments and ventilated newborn rabbits for evaluation of in vivo effects. In the presence of various potential inhibitors (meconium 5 mg.mL-1, fibrinogen 5 mg.mL-1, albumin 25 mg.mL-1, or whole serum proteins 25 mg.mL-1), Curosurf at a concentration of 5 mg.mL-1 was inactivated while SP-A-Curosurf and natural porcine surfactant at the same concentration had normal maximum and minimum surface tension. This protective effect of SP-A was calcium dependent. In immature newborn rabbits, the improvement of lung-thorax compliance observed after treatment with 100 mg.kg-1 of SP-A-Curosurf was equivalent to that obtained with 200 mg.kg-1 of Curosurf. Similarly, in near-term newborn rabbits with respiratory failure induced by instillation of fibrinogen via the airways, the increase in compliance after administration of 100 mg.kg-1 of SP-A-Curosurf corresponded to that seen after treatment with 200 mg.kg-1 of Curosurf, whereas Curosurf at a dose of 100 mg.kg-1 had no substantial effect. Our data thus indicate that surfactant protein A increases the resistance of Curosurf to inactivation under in vivo conditions.

Analysis of polypeptide expression in benign and malignant human breast lesions

Results of two-dimensional electrophoresis (2-DE) analyses of human breast carcinoma are described. Tumor cells were extracted and purified from breast carcinomas with different proliferative indeces and degrees of genomic stability. Cells purified from fibroadenoma tissue served as controls for benign cells. The following results were observed: (i) Analysis of samples from different areas of the same tumor showed a high degree of similarity in the pattern of polypeptide expression. Similarly, analysis of two tumors and their metastases revealed similar 2-DE profiles. (ii) In contrast, large variations were observed between different lesions with comparable histological characteristics. Larger differences in polypeptide expression were observed between potentially highly malignant carcinomas compared to comparisons of less malignant lesions. These differences were in the same order of magnitude as those observed comparing a breast carcinoma to a lung carcinoma. (iii) The levels of all cytokeratin forms resolved (CK7, CK8, CK15, and CK18) were significantly lower in carcinomas compared to fibroadenomas. (iv) The levels of high molecular weight tropomyosins (1-3) were lower in carcinomas compared to fibroadenomas. The expression of tropomyosin-1 was found to be 1.7-fold higher in primary tumors with metastatic spread to axillar lymph nodes compared to primary tumors with no evidence of metastasis (p < 0.05). (v) The expression of proliferating cell nuclear antigen (PCNA) and some members of the stress protein family (pHSP60, HSP90, and calreticulin) were higher in carcinomas. We conclude that malignant progression of breast carcinomas results in large heterogeneity in polypeptide expression between different tumors, but that some common themes such as decreased expression of cytokeratin and tropomyosin polypeptides can be discerned.

Analysis of polypeptide expression in benign and malignant human breast lesions: down-regulation of cytokeratins

Malignant progression of tumour cells is caused by the accumulation of genetic defects, which when combined will generate a large phenotypic diversity. Simultaneous quantitation of a large number of gene products in tumour cells is desirable, but difficult to achieve. We have here quantitated the levels of a number of abundant polypeptides in human breast carcinoma cells using two-dimensional gel electrophoresis (2-DE; PDQUEST). For this purpose, tumour cells were prepared from the tissue of 17 breast carcinomas. Fibroadenoma tissue was used as reference for benign cells. An increase of the spot density of the PCNA polypeptide was observed in rapidly proliferating tumour cells, confirming the validity of the procedures used. In the set of 24 polypeptide spots with known identity, decreases in cytokeratin and tropomyosin levels were observed. The levels of all cytokeratin forms resolved (CK7, CK8, CK15 and CK18) were significantly lower in carcinomas than in fibroadenomas. The levels of tropomyosin 2 and 3 were lower in carcinomas than in fibroadenomas. In contrast, the levels of some members of the stress protein family (pHSP60, HSP90 and calreticulin) were higher in carcinomas. Furthermore, changes in the expression of lactate dehydrogenase and GT-pi, but not in nm23, were observed. We conclude that simultaneous analysis of multiple polypeptides in human carcinomas can be achieved by 2-DE and may be useful in prognostic studies, and that malignant progression of breast carcinomas results in the decreased expression of cytokeratin polypeptides. This phenomenon must be considered in studies where cytokeratins are used as markers to identify the epithelial cell compartment in breast carcinomas.

Assessment of homogeneity in polypeptide expression in breast carcinomas shows widely variable expression in highly malignant tumors

We describe the results from a protein-based approach to the study of heterogeneity in gene expression between human tumors. Cell preparations from 5 benign breast lesions, 5 potentially weakly malignant and 4 potentially highly malignant invasive ductal breast carcinomas were examined by 2-dimensional gel electrophoresis (2-DE) gels. Qualitative and quantitative differences were recorded by computerized analysis. Analysis of samples from different areas of the same tumor showed a high degree of similarity in the pattern of polypeptide expression. Analysis of 2 tumors and their metastases revealed similar 2-DE profiles. In contrast, variations between different lesions with comparable histological characteristics were considerable. Greater differences in polypeptide expression were observed between potentially highly malignant carcinomas compared with comparisons of less malignant lesions. Our results show that malignant human breast carcinomas may be highly heterogeneous in their patterns of gene expression.

Expression of tropomyosin isoforms in benign and malignant human breast lesions

High molecular weight tropomyosins (tms) are commonly down-regulated in fibroblasts transformed by oncogenes. Previous studies have also demonstrated that specific tm isoforms are down-regulated in human breast carcinoma cell lines. We examined tropomyosin isoforms in cells prepared from non-cancerous breast lesions and primary human breast carcinomas. The average level of expression of all three high molecular weight tm isoforms (tm 1-3) in carcinomas was generally found to be less than 25% of that observed in non-cancerous breast lesions. Interestingly, the expression of tm 1 was found to be 1.7-fold higher in primary tumours with metastatic spread to axillary lymph nodes compared with primary tumours with no evidence of metastasis (p<0.05). Similarly, tm 1 expression was higher in two 12V-H-ras transformed fibroblast cell lines capable of experimental metastasis compared with three weakly metastatic cell lines. We conclude from these studies that expression of high molecular weight tm isoforms is low in primary breast carcinomas, and that metastatic tumours express relatively high levels of tm 1.

Detection of polypeptides associated with the histopathological differentiation of primary lung carcinoma

Two-dimensional polyacrylamide gel electrophoresis combined with a non-enzymatic sample preparation technique is useful for analysing clinical tumour material. Using these techniques, we analysed the relationship between the histopathological findings in primary lung malignancies and the expression of a number of unidentified polypeptides that were detected in the molecular weight region 20-35 kDa. In this study 45 cases of primary lung cancer (PLC) (21 cases of adenocarcinoma, ten cases of squamous cell carcinoma, five cases of large-cell carcinoma, one case of adenosquamous cell carcinoma, five cases of small-cell carcinoma and three cases of carcinoid tumour) were examined. For reference, a human diploid fibroblast cell line (W138) and normal peripheral lymphocytes were used. Sixteen polypeptides were judged to be associated with histopathological features. These polypeptides seem to be valuable as differentiation markers. The simultaneous evaluation of these polypeptides and some other proliferation markers (e.g. PCNA, PCNA 'satellite', Numatin/protein B23 and lamin B) seems to clarify the characteristics of each case of PLC. Furthermore, it is possible to classify PLC based on the two-dimensional electrophoresis findings, and this classification of PLC is suggested to reflect the biological features of the tumour more precisely than that based only on morphology.

Sample preparation of human tumors prior to two-dimensional electrophoresis of proteins

Sample preparation procedures are critical for obtaining high quality two-dimensional electrophoresis (2-DE) separations from clinical tumor materials. In this communication, we describe procedures which we have found satisfactory for preparing various tumor samples for 2-DE. By these procedures, tumor cells are enriched from serum proteins and contaminating stromal cells. Tumors can be prepared with good reproducibility to obtain high resolution using these techniques.