Ergül Eyol

Identification and characterization of riproximin, a new type II ribosome-inactivating protein with antineoplastic activity from Ximenia americana

The aim of this study was to identify and characterize the active component(s) of Ximenia americana plant material used to treat cancer in African traditional medicine. By a combination of preextraction, extraction, ion exchange and affinity chromatography, a mixture of two cytotoxic proteins was isolated. Using degenerated primers designed on the de novo sequence of two tryptic peptides from one of these proteins, a DNA fragment was amplified and the sequence obtained was used to determine the complete cDNA sequence by the RACE method. Sequence analysis and molecular modeling showed that the new protein, riproximin, belongs to the family of type II ribosome inactivating proteins. These results are in good agreement with the ability of riproximin to inhibit protein synthesis in a cell‐free system, as well as with the cytotoxicity of riproximin, as demonstrated by its IC50 value of 0.5 pM in MCF7, 1.1 pM in HELA and 0.6 pM in CC531‐lacZ cells. To assess the antineoplastic efficacy of the purified riproximin in vivo, the CC531‐lacZ colorectal cancer rat metastasis model was used. Significant anticancer activity was found after administration of total dosages of 100 (perorally) and 10 (intraperitoneally) pmol riproximin/kg. These results suggest that riproximin has distinct potential for cancer treatment. —Voss, C., Eyol, E., Frank, M., von der Lieth, C.‐W., Berger, M. R. Identification and characterization of riproximin, a new type II ribosome‐inactivating protein with antineoplastic activity from Ximenia americana. FASEB J. 20, E334–E345 (2006)

Osteopontin but not osteonectin favors the metastatic growth of pancreatic cancer cell lines.

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer- related death in Western countries and among the malignancies with the worst prognosis. Osteonectin and osteopontin, two proteins of the extracellular matrix, have been found to be up-regulated in PDAC. In the present study the expression of osteopontin mRNA as determined in a panel of 14 human pancreatic cancer cell lines was significantly related to the growth these cell lines in the liver of nude rats (p=0.001) whereas osteonectin showed a trend of being negatively related to pancreatic cancer cell growth in vivo (p=0.10). In an in vitro co-culture model of human Suit2-007 and rat AsML PDAC cells with rat hepatocytes, a clearly increased expression of OPN mRNA was found in the tumor cells. In addition both, down-regulation of osteopontin with specific antisense oligonucleotides and treatment with exogenous rh-osteonectin were associated with reduced cell proliferation. In accordance with the latter finding down-regulation of osteonectin was coupled with increased proliferation. This evidence supports a protumorigenic role of osteopontin and points to an anti-tumorigenic role of osteonectin in PDAC.

Sequential biphasic changes in claudin1 and claudin4 expression are correlated to colorectal cancer progression and liver metastasis

Terminal progression of colorectal cancer (CRC) culminates in liver metastasis. To identify genes that are involved in the metastatic phenotype, cDNA microarrays were used to analyse mRNA expression profiles of colorectal carcinoma (CC)531 rat colon adenocarcinoma cells for changes related to their homing into the liver. Briefly, CC531 cells were intraportally implanted into the liver of Wag‐Rij rats and re‐isolated after 3, 6, 9, 14 and 21 days. Compared to control CC531 cells, claudin1 and claudin4 were among the ≥8‐fold initially down‐regulated genes. The co‐culture of tumour cells with isolated rat hepatocytes and Kupffer cells did not induce down‐regulation of either claudin1 or 4. When the environment effective on circulating tumour cells was simulated by cell culture conditions favouring their adhesion, only claudin4 showed augmented expression. Knockdown of claudin1 and claudin4 mediated by small interfering RNA caused significantly increased migration and decreased clonogenic growth of tumour cells (P < 0.05), but had no effect on their proliferation. These experimental results were paralleled by increased claudin1 and claudin4 expression in human CRC samples in Union for International Cancer Control (UICC) stages I–III, as evaluated by real‐time PCR. Increased claudin4 levels were correlated with significantly reduced overall survival (log‐rank test, P= 0.018). Further, significantly (P < 0.05) reduced expression of claudin1 and claudin4 was observed in stage IV and liver metastasis by immunohistochemistry. In conclusion, sequential biphasic changes in claudin1 and claudin4 expression occur during the homing of rat CC531 CRC cells to the liver. This modulation is reflected by significant changes in claudin expression in human primary and metastatic CRC.