Ursula Valentiner

The cytotoxic effect of mistletoe lectins I, II and III on sensitive and multidrug resistant human colon cancer cell lines in vitro

Multidrug resistance glycoprotein1 (MDR-1) eliminates amphiphilic chemotherapeutic agents out of tumour cells leading to therapeutic failures. The aim of this study was to investigate the cytotoxic effect of mistletoe lectins (MLs) I, II and III on the sensitive human colon cancer cell line HT 29(mdr-), its multidrug resistant variant HT 29(mdr+), the variant HT 29(SF1m) transfected with the MDR-1 gene and its sensitive control cell line HT 29(deltaSF). Both cell proliferation and ML binding pattern were analysed. Marked quantitative differences concerning the cytotoxic effect of the three MLs on the different cell lines were observed. All MLs showed the greatest cytotoxicity towards the HT 29(mdr+) cells, in which multidrug resistance (MDR) was induced by increasing concentrations of a MDR inducing agent. In contrast, MDR-1 and mock-transfected cells showed almost the same sensitivity towards the three MLs as the control cells (HT 29(mdr-)). FACS analysis showed that the HT 29(mdr+) cells were the cells with the highest density of ML binding sites. Thus, higher sensitivity of HT 29(mdr+) cells are not caused by the overexpression of MDR-1, but are caused by the general changes of the cellular glycosylation during the acquisition of the MDR phenotype.

Expression of the neural cell adhesion molecule and polysialic acid in human neuroblastoma cell lines

The neural cell adhesion molecule NCAM is a cell surface glycoprotein of the immunoglobulin superfamily and is widely expressed in tumours of neuroectodermal origin such as neuroblastoma. NCAM can be decorated by the carbohydrate polymer polysialic acid (polySia), which attenuates NCAM-mediated cell adhesion and increases cellular motility. The key enzymes in the biosynthesis of polySia are the two polysialyltransferases ST8SiaII and ST8SiaIV. In the present study, expression of NCAM, polySia-NCAM, ST8SiaII and ST8SiaIV was investigated in five human neuroblastoma cell lines before and after xenografting into SCID mice by immunohistochemistry, Western blot analysis and real-time PCR. Results were correlated with the metastatic potential. In vitro, three cell lines (LAN-1, LAN-5 and SH-SY5Y) were positive for polySia attached to the transmembrane isoforms NCAM-140 and NCAM-180, whereas Kelly and SK-N-SH cells were negative for NCAM and polySia. In the presence of NCAM, the level of polySia correlated with the amount of polysialyltransferase transcripts, which were highest in LAN-1, LAN‑5 and SH-SY5Y cells. In the respective primary tumours grown in SCID mice, the expression patterns of NCAM, polySia and polysialyl-transferases were similar to those observed in vitro. After subcutaneous engraftment, polySia-NCAM-positive neuroblastoma developed disseminated micrometastases, a metastatic pattern that was not observed for tumours derived from NCAM-negative cell lines. Together, this indicates that the presence of polySia reduces the adhesiveness of tumour cells and promotes dissemination.

Expression of CD44 is associated with a metastatic pattern of human neuroblastoma cells in a SCID mouse xenograft model.

Expression of CD44, a transmembrane glycoprotein involved in cell-cell and cell-matrix interactions, has been associated with growth and metastatic behavior in several malignant tumors. In contrast to most other malignancies, in which up-regulation of CD44 is related to tumor progression, the absence of CD44 expression characterizes the aggressiveness of neuroblastomas in clinical studies. In this study, cells of human neuroblastoma cell lines (IMR-32, Kelly, LAN-1, LAN-5, LS, SH-SY5Y and SK-N-SH) were injected subcutaneously into SCID mice, and their growth behavior and CD44 expression were analyzed. All neuroblastoma cells engrafted in the SCID mouse, but primary tumor growth and metastatic potential varied considerably. Expression of CD44 was associated with a metastatic pattern of the neuroblastoma cell lines. CD44-positive neuroblastomas produced multicellular metastases predominantly located in the intra- and periarterial space of the lung. CD44-negative neuroblastomas developed numerous micrometastases in the lung interstitium. In conclusion, the entire spectrum of metastatic patterns can be modeled in SCID mice using the human neuroblastoma cell lines employed in this study. Our xenograft model provides a platform for investigating the complex processes involved in metastasis formation and for testing new anti-metastatic drugs. In particular, the role of CD44 in the formation of metastasis can be evaluated.

Cell adhesion molecules in metastatic neuroblastoma models

Several cell adhesion molecules (CAMs) including selectins, integrins, cadherins and immunoglobulin-like CAMs are involved in leukocyte adhesion especially at sites of inflammation. In cancer cells, these CAMs have been associated with the growth and metastatic behavior in several malignant entities. In this study adhesion of LAN 1 and SK-N-SH neuroblastoma cells to selectins, hyaluronan and endothelial cells were determined under flow conditions. Furthermore cells were injected subcutaneously into wildtype and selectin deficient scid mice and their growth and metastatic behavior were analyzed. Under shear stress SK-N-SH cells firmly adhered to E-selectin-Fc-fusion protein, hyaluronan and endothelial cells, while LAN 1 cells showed less or hardly any adhesive events by comparison. In the SK-N-SH xenograft model metastasis formation was slightly dependent on the expression of selectins, while LAN 1 cells developed metastases completely independent of selectin expression. The different adhesive and metastatic properties of LAN 1 and SK-N-SH cells are reflected by a different expression profile of several CAMs. The results indicate that endothelial selectins are not essential for metastasis formation of human LAN 1 and SK-N-SH cells. However, other CAMs namely CD44, N-cadherin, NCAM and integrins were upregulated or downregulated, respectively, in SK-N-SH and LAN 1 cells and are potential adhesion molecules involved in the metastatic cascade of these cells.

The effect of the PPAR-gamma agonist rosiglitazone on neuroblastoma SK-N-SH cells in a metastatic xenograft mouse model.

Rosiglitazone, a peroxisome proliferator activated receptor-gamma (PPAR-gamma) agonist used in clinical practice to treat type 2 diabetes, has been shown to inhibit neuroblastoma cell proliferation in vitro. In the present study, SK-N-SH neuroblastoma cells were subcutaneously injected into SCID mice and their growth and metastatic behavior under the treatment with rosiglitazone was analyzed. Therapeutic effects were evaluated comparing primary tumor weight, cell proliferation, apoptosis, and number of pulmonary metastasis. Rosiglitazone significantly decreased cell proliferation of the SK-N-SH neuroblastomas from 57.0% in the solvent control to 45.0% and 47.0% in the two treatment groups, respectively. However, primary tumor weight, apoptosis, and metastasis were not considerably influenced. These results indicate that the PPAR-gamma agonist rosiglitazone has only slight antitumor effects on SK-N-SH neuroblastoma growth in vivo in contrast to in vitro.

In Vivo Xenograft Models of Breast Cancer Metastasis

If breast cancer patients are not cured, it is largely because of the fact that the cancer has spread beyond its primary site--the breast--to distant sites, such as, e.g., bone marrow, lung, brain, and/or liver. These secondary tumors are called metastases, and the underlying mechanisms leading to these secondary tumor deposits are complex and still ill understood. In this chapter, we report on how to develop clinically relevant human breast cancer cell line xenografts in severe combined immunodeficient mice. In severe combined immunodeficient mice, metastasizing human breast cancer cell lines were identified by their ability to bind the lectin Helix pomatia agglutinin, which was identified as a marker of metastasis in clinical studies. This model system was created to help to define the rate-limiting steps of the metastatic cascade.

Differential Proteome Analysis of Human Neuroblastoma Xenograft Primary Tumors and Matched Spontaneous Distant Metastases

Metastasis formation is the major cause for cancer-related deaths and the underlying mechanisms remain poorly understood. In this study we describe spontaneous metastasis xenograft mouse models of human neuroblastoma used for unbiased identification of metastasis-related proteins by applying an infrared laser (IR) for sampling primary tumor and metastatic tissues, followed by mass spectrometric proteome analysis. IR aerosol samples were obtained from ovarian and liver metastases, which were indicated by bioluminescence imaging (BLI), and matched subcutaneous primary tumors. Corresponding histology proved the human origin of metastatic lesions. Ovarian metastases were commonly larger than liver metastases indicating differential outgrowth capacities. Among ~1,900 proteins identified at each of the three sites, 55 proteins were differentially regulated in ovarian metastases while 312 proteins were regulated in liver metastases. There was an overlap of 21 and 7 proteins up- and down-regulated at both metastatic sites, respectively, most of which were so far not related to metastasis such as LYPLA2, EIF4B, DPY30, LGALS7, PRPH, and NEFM. Moreover, we established in vitro sublines from primary tumor and metastases and demonstrate differences in cellular protrusions, migratory/invasive potential and glycosylation. Summarized, this work identified several novel putative drivers of metastasis formation that are tempting candidates for future functional studies.