Doris Mayer

Calcium-Binding Proteins S100A8 and S100A9 as Novel Diagnostic Markers in Human Prostate Cancer

Purpose: S100 proteins comprise a family of calcium-modulated proteins that have recently been associated with epithelial tumors. We examined the expression of two members of this family, S100A8 and S100A9, together with the S100 receptor RAGE (receptor for advanced glycation end products) in human prostate adenocarcinomas and in prostatic intraepithelial neoplasia. Experimental Design: Tissue specimens of 75 patients with organ-confined prostate cancer of different grades were analyzed by immunohistochemistry for expression of S100A8, S100A9, and RAGE. In addition, in situ hybridization of S100A8 and S100A9 was done for 20 cases. An ELISA was applied to determine serum concentrations of S100A9 in cancer patients compared with healthy controls or to patients with benign prostatic hyperplasia (BPH). Results: S100A8, S100A9, and RAGE were up-regulated in prostatic intraepithelial neoplasia and preferentially in high-grade adenocarcinomas, whereas benign tissue was negative or showed weak expression of the proteins. There was a high degree of overlap of S100A8 and S100A9 expression patterns and of S100A8 or S100A9 and RAGE, respectively. Frequently, a gradient within the tumor tissue with an increased expression toward the invaded stroma of the prostate was observed. S100A9 serum levels were significantly elevated in cancer patients compared with BPH patients or healthy individuals. Conclusion: Our data suggest that enhanced expression of S100A8, S100A9, and RAGE is an early event in prostate tumorigenesis and may contribute to development and progression or extension of prostate carcinomas. Furthermore, S100A9 in serum may serve as useful marker to discriminate between prostate cancer and BPH.

Differences of expression of cytoskeletal proteins in cultured rat hepatocytes and hepatoma cells

Abstract Cytoskeletal elements, enriched in intermediate-sized filaments and insoluble in buffers of high salt concentrations and Triton X-100, were isolated from various cultures of rat hepatocytes and hepatoma cells, and their proteins were studied by one- and two-dimensional gel electrophoresis and immunofluorescence microscopy. The cells examined included several permanent cell lines (MH1C1, HTC, hepatoma 72 22 , clone 12 from Gunn rat hepatocytes, and cell clones from normal rat hepatocytes), as well as freshly dissociated hepatocytes that were cultured and allowed to attach to substratum for increasing periods of time, beginning at 24 h after removal of the liver from the animal. Filaments containing vimentin, which were not found in hepatocytes grown in liver tissue, were detected in most of the cultured hepatocytes and hepatoma cells, except in MH1C1 cells, and were shown to be newly synthesized during the first days of primary culture. Maintenance of expression of filaments containing proteins immunologically related to epidermal prekeratin (‘cytokeratins’) was observed in all cells examined but HTC cells. Detailed comparison of the cytokeratin polypeptides present in various hepatocyte and hepatoma cell cultures showed that, in some of the cultured epithelial liver cells, cytokeratins are expressed which are identical with, or similar to, those of normal hepatocytes grown in the liver. On the other hand, differences in cytokeratin polypeptides were also found among different hepatocyte-derived cell cultures. Changes of expression of cytoskeletal proteins were found to occur even in cloned cell populations, and cells positive for certain cytokeratins could be seen next to other cells that were negative. The results demonstrate that profound changes of cytoskeletal composition, especially concerning intermediate filament protein patterns, can occur during culturing in vitro. Moreover, we show that different intermediate filament proteins can be expressed in different hepatocyte-derived cell cultures and that changes of cytoskeletal composition can occur in a given cell population, without obvious effects on cell growth rate and cell morphology. During culturing of hepatocytes and hepatoma cells, there seems to be a general tendency to induce the production of vimentin filaments as well as to maintain the production of cytokeratins similar to the hepatocyte-specific cytokeratins in liver tissue. However, the demonstrated exceptions speak against a role of these filament proteins as prerequisites for the growth of an epithelial cell in vitro. Rather, the presence of filaments containing certain cytokeratins and of desmosomes in epithelial cells growing in vitro seems to reflect the synthesis of specific differentiation markers which may be lost, independently, in some cells during culturing.

Down-regulation of insulin-like growth factor-I receptor and insulin receptor substrate-1 expression in advanced human breast cancer.

The ligands, receptors and related signaling proteins of the insulin‐like growth factor family are involved in the regulation of breast‐cancer cell growth. We investigated the expression pattern of insulin‐like growth factor‐I receptor (IGF‐IR), insulin receptor (IR) and insulin receptor substrate‐1 (IRS‐1), a core downstream signaling protein, in 69 primary breast‐cancer specimens of different grades and in 21 control tissues by immunohistochemistry. In addition, cell proliferation (percentage of Ki67+ nuclei) and estrogen receptor (ER) expression were determined. IGF‐IR, IRS‐1 and IR were expressed mainly in epithelial cells. IRS‐1 and IGF‐IR were expressed at high levels in control tissues and in well and moderately differentiated carcinomas but at low levels in poorly differentiated breast cancers. IR expression did not show a significant correlation with the differentiation grade of the tissues investigated. Statistical analysis (ROC analysis for tumor grade) demonstrated that down‐regulation of IGF‐IR and IRS‐1 correlated better with tumor progression than reduction of ER expression or increase in cell proliferation, IGF‐IR showing the best correlation, followed by IRS‐1 and, less significant, ER and Ki67. Our findings clearly show that progression of breast cancer is accompanied by a reduction of IGF‐IR/IRS‐1 expression and that IGF‐IR/IRS‐1 expression inversely correlates with high proliferation rate in dedifferentiated breast cancers. The strong correlation of IGF‐IR and IRS‐1 down‐regulation with tumor progression suggests the use of IGF‐IR and IRS‐1 as a novel set of marker proteins for tumor grading. Int. J. Cancer 89:506–513, 2000.

Hepatocellular glycogenosis and related pattern of enzymatic changes during hepatocarcinogenesis

Systematic studies of the sequence of cellular changes during hepatocarcinogenesis induced predominantly in rats by stop experiments with N-nitrosomorpholine (NNM) led to the following main results and conclusions: The development of hepatocellular tumors is preceded by a multifocal hepatic glycogen storage disease (glycogenosis). Cytomorphological and cytochemical findings suggest a sequence of focal changes leading from clear and acidophilic glycogen storage foci through mixed cell foci and neoplastic nodules to hepatocellular carcinomas. The clear and acidophilic glycogen storage cells persisting after withdrawal of the carcinogen apparently represent a preneoplastic cell population, the neoplastic transformation of which is accompanied by a gradual reduction of glycogen and a concomitant increase in ribosomes (basophilia). The first appearance and frequency of the different liver lesions investigated was shown to depend on the dose of carcinogen administered. With increasing dose of NNM, the number of focal lesions considerably increased, and this was accompanied by an earlier development of mixed and basophilic cell populations. There was no indication of any reversibility of pronounced focal lesions under the experimental conditions chosen. On the contrary, the foci became larger and acquired phenotypic markers closer to neoplasia independent of further action of the carcinogen. Enzyme histochemically, the majority of the pronounced glycogen storage foci showed a reduction in the activities of glycogen phosphorylase and glucose-6-phosphatase while the activity of glucose-6-phosphate dehydrogenase, a key enzyme for the pentose phosphate pathway, was increased. The mixed cell foci, neoplastic nodules and carcinomas which emerged at later stages were characterized by a progressive shift away from glycogen metabolism towards glycolysis and the pentose phosphate pathway. as indicated by an increase in glyceraldehyde-3-phosphate dehydrogenase and glucose-6-phosphate dehydrogenase activities. These changes in enzyme pattern are in keeping with a developmental sequence leading from glycogen storage foci through mixed cell foci and neoplastic nodules to hepatocellular carcinomas. Biochemical microanalysis of dissected glycogen storage foci and mixed cell foci revealed that the foci composed exclusively of storage cells contained on an average 100% more glycogen than the normal liver tissue. The overall glycogen content of the mixed cell foci, which were composed of both glycogenotic and glycogen-poor basophilic cells, was not distinguishable from that of normal tissue.(ABSTRACT TRUNCATED AT 400 WORDS)

Glycogen synthase kinase-3 interacts with and phosphorylates estrogen receptor alpha and is involved in the regulation of receptor activity.

Like other steroid hormone receptors, estrogen receptor-α (ERα) is a substrate for protein kinases, and phosphorylation has profound effects on the function and activity of this receptor. A number of different kinases have been implicated in ERα regulation. In this report we show by mutational analysis and in vitro kinase assays that ERα is a substrate for glycogen synthase kinase-3 (GSK-3) in vitro and is phosphorylated on two sites, the Ser-102, -104, and -106 motif and Ser-118, both located in the N-terminal transcription activation function (AF-1) domain. GSK-3 forms a complex with ERα in vivo as demonstrated by co-immunoprecipitation from cell lysates. The GSK-3 inhibitor lithium chloride was used to determine the role of GSK-3 in phosphorylation of Ser-102, -104, and -106 and Ser-118 in vivo and to explore the role of these serines in the regulation of ERα function. Treatment of cells with lithium chloride resulted in dephosphorylation of Ser-104 and -106 and Ser-118, which suggests these serine residues as targets for GSK-3 in vivo. Our results further suggest that ERα phosphorylation by GSK-3 stabilizes ERα under resting conditions and modulates ERα transcriptional activity upon ligand binding. Inhibition and constitutive activation of GSK-3, both, resulted in inhibition of ERα transcriptional activity, indicating a function of active as well as inactive GSK-3 in ERα regulation. These findings uncover a novel mechanism for the regulation of ERα-mediated estrogen signaling controlled by a dual action of GSK-3.

Analysis of signaling pathways related to cell proliferation stimulated by insulin analogs in human mammary epithelial cell lines

Insulin and insulin analogs stimulate proliferation of human mammary epithelial cells. We identified and analyzed the signaling pathways related to cell proliferation induced by regular insulin and by four insulin analogs presently approved for therapeutical use. Benign and malignant mammary cell lines showing different insulin receptor (IR) and IGF-I receptor (IGF-IR) expression patterns were studied. Cell proliferation was studied by crystal violet staining (BrdU-FACS analysis). Activation of insulin and IGF signaling pathways was studied by analysis of the phosphorylation status of IGF-IR and of key signaling proteins of the phosphoinositide 3-kinase (PI3K)/Akt and MAP kinase pathways, by the use of specific PI3K and MAP kinase inhibitors, and by silencing of IR and IGF-IR. Lantus stimulated the growth of MCF7 cells, which show high IGF-IR/IR ratio, significantly at 0.3 nmol/l, while regular insulin (Actrapid and bovine insulin) and other insulin analogs (Novorapid, Humalog, and Levemir) stimulated cell growth at 1.5-15 nmol/l concentrations. No difference between Lantus and the other insulin analogs was observed regarding growth stimulation of MCF10A cells showing low IGF-IR/IR ratio. Growth stimulation of MCF7 cells by Lantus was mainly due to strong activation of the IGF-IR and the MAP kinase pathway. Regular insulin and other insulin analogs tested activated mainly the IR and the PI3K/Akt pathway. We conclude that unlike regular insulin and other insulin analogs, Lantus strongly activates the IGF-IR and the MAP kinase pathway in MCF7 cells and is a strong mitogen for cells characterized by a high-IGF-IR/IR ratio.

Preparation of tetramethylrhodaminyl-phalloidin and uptake of the toxin into short-term cultured hepatocytes by endocytosis

A fluorescent phallotoxin with high photostability, tetramethylrhodaminyl-phalloidin (Rh-phalloidin), has been prepared. The affinity of this compound to rabbit muscle actin has been determined to be about 6 times lower than that of phalloidin. In freshly isolated hepatocytes the internalized fluorescent toxin stains the cellular actin. In contrary, there is no actin staining visible in cultured hepatocytes. Short-term cultured hepatocytes (5 h of culturing) incorporate the toxin by endocytosis; it is kept sealed in the endocytotic vesicles, which are usually found accumulated at the sites where cells touch after reaggregation.

Increase of AKT/PKB expression correlates with gleason pattern in human prostate cancer

AKT/PKB is a central signaling molecule related to stimulation of cell proliferation and inhibition of apoptosis. Perturbations of AKT expression and function play an important role in tumor development and progression. We wanted to determine (a) whether AKT is overexpressed in human prostatic tumors, (b) whether AKT expression is correlated with tumor grade, and (c) whether AKT expression correlates with clinicopathological parameters. AKT expression was investigated by immunohistochemistry in sections from 56 paraffin‐embedded prostate specimens displaying benign prostatic tissue (BPT), prostatic intraepithelial neoplasia (PIN), and primary tumors graded 2–5 according to Gleason. The staining intensity for AKT was significantly more pronounced in tumors compared to BPT, with PIN ranging between BPT and carcinomas. Similarly, the fraction of AKT‐positive cells was higher in tumors than in BPT. A score of AKT expression (calculated as product from intensity and fraction of positive cells) ranging from 0–6 was also significantly higher in tumors than in BPT. Furthermore, the intensity of AKT expression in tumors showed a positive correlation with high preoperative serum levels of prostate specific antigen (PSA ≥ 10 ng/ml, p = 0.0325). These data show that AKT is upregulated in prostate cancer and that expression is correlated with tumor progression.

Detection and identification of tumor-associated protein variants in human hepatocellular carcinomas

The proteomic approach is a valuable tool to detect and identify proteins that are associated with cancer. In previous investigations on experimentally induced rat hepatomas, we detected aldose reductase‐like protein (ARLP) as a highly significant marker protein. Our present study was intended to look for the presence of similar tumor‐associated marker proteins on human hepatocellular carcinomas (HCC). We found several novel tumor‐associated protein variants that represent members of the aldo‐keto reductase (AKR) superfamily. Human aldose reductase‐like protein‐1 (hARLP‐1) was the most prominent tumor‐associated AKR member detected in HCC by 2‐dimensional electrophoresis (2‐DE) and identified by mass spectrometric fingerprinting. The enzyme was found in 4 distinct forms (hARLP‐1, 36/7.4 (kd/pI); hARLP‐2, 36/7.2; hARLP‐3, 36/6.4; and hARLP‐4, 33/7.35). In addition, a human aldose reductase‐like protein (hARLP‐5, 36/7.6) was identified that differed from hARLP‐1 by 1 amino acid (D313N), indicating 2 allelic forms of the human aldose reductase‐like gene. A novel antibody directed against common parts of the hARLPs revealed hARLP reactivity in human HCC by immunohistochemistry. Furthermore, aldose reductase (AR) was identified and characterized as a tumor‐associated variant. In conclusion, in all investigated human HCCs at least one of the various types of the described tumor‐associated proteins of the AKR superfamily was clearly present. Of these HCC samples, 95% were positive for hARLPs as proven by 2‐DE analysis and/or by use of the antibody directed against hARLP. Thus, hARLP is a strong candidate for use as an immunohistochemical diagnostic marker of human HCC. (HEPATOLOGY 2004;39:540–549.)

Proliferative effects of insulin analogues on mammary epithelial cells.

Abstract Structural modification of insulin results in the generation of insulin analogues that show altered binding affinities to the insulin receptor and/or IGF-I receptor. As a consequence these insulin analogues may have increased mitogenic potency. Nine benign or malignant human mammary epithelial cells, which show different insulin receptor and IGF-I receptor expression patterns, were studied regarding mitogenicity of insulin and insulin analogues. Only insulin glargine showed a significantly higher proliferative effect on MCF-7 breast cancer cells compared to regular insulin among a panel of short- or long-acting insulin analogues, that are in clinical use.