Midkine confers Adriamycin resistance in human gastric cancer cells.
ABSTRACT Midkine (MDK) is a heparin-binding molecule involved in the regulation of growth and differentiation during embryogenesis, which is overexpressed in most of human malignant tumors and may act as an oncoprotein. The aim of the current study was to investigate the mechanism of MDK involved in the Adriamycin (ADR) resistance in human gastric cancer cells in vitro. We found that Adriamycin-resistant SGC7901 (SGC7901/ADR) exhibited 58.6-fold greater resistance to ADR compared with Adriamycin-sensitive SGC7901 cell line. MDK mRNA and protein expression levels were significantly higher in SGC7901/ADR than in SGC7901. To gain a deeper insight into the role of MDK in SGC7901/ADR, we stably transfected Adriamycin-sensitive SGC7901 with viral vector expressing MDK. Our result showed that multidrug resistance type I (MDR1) was found in SGC7901/ADR, not in SGC7901 by RT-PCR regardless of MDK transfection. P-Glycoprotein, which is the MDR1-coded protein, was found in SGC7901/ADR, not in SGC7901 by Western blot regardless of MDK transfection. We investigated whether an activation of the tyrosine kinase pathway would change the drug resistance phenotype with MDK transfection. Western blot results showed the upregulation of phosphorylated protein kinase B (AKT) and phosphorylated extracellular signal-regulated protein kinase (ERK) in Adriamycin-sensitive SGC7901 cell by MDK transfection accompanied with drug resistance to ADR, although the level of AKT and ERK protein expression did not change, so our results suggested that MDK, which can activate AKT and ERK by phosphorylation, induced the Adriamycin resistance in gastric cancer cells. Understanding the molecular mechanisms, driving MDK-induced ADR resistance, will provide benefits in developing new therapies for gastric cancer.
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ABSTRACT: Midkine is highly expressed in various cancers, including neuroblastoma, one of the most malignant pediatric solid tumors, and it has been shown to be useful as a tumor marker, a prognosis factor, and a target of molecular therapy. In order to establish a midkine-targetting therapy, several molecular tools (e.g., siRNA, antibodies, and RNA aptamer) have been used. In neuroblastoma, the involvement of midkine in tumorigenesis has been revealed in vivo by model mice, and its targetting by RNA aptamer has been shown to be effective toward xenografted tumors. Chemoresistance is one of the notable phenotypes regulated by midkine in various cancer cell types. In pancreatic tumor and glioma cells, midkine is expressed in chemoresistant cells and plays a role in the survival against drugs. In contrast to those tumors, midkine was expressed in every tested neuroblastoma cell line and the knockdown of midkine alone was sufficient to suppress their growth. These results indicate that neuroblastoma cells are so highly dependent on midkine that a midkine-targetting therapy could exert a greater effect in these cells. In order to achieve a midkine-targetting therapy for high-risk neuroblastoma patients, the further refinement of the RNA aptamer or antibody as tools and the elucidation of midkine signalling would be the immediate issues. Regarding the latter, although it has been indicated that Notch2 functions as a receptor in neuroblastoma cells, it remains likely that other receptors (e.g., ALK) are also involved in MK signalling.British Journal of Pharmacology 10/2013; · 5.07 Impact Factor
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ABSTRACT: CRKL encodes an adaptor protein that has been recently reported to be overexpressed in various cancers and associate with the malignant behavior of cancer cells. However, the expression pattern of CRKL protein and its clinical significance in human bladder cancer have not been well characterized to date. In the present study, CRKL expression was analyzed in 82 archived bladder cancer specimens using immunohistochemistry, and the correlations between CRKL expression and clinicopathological parameters were evaluated. We found that CRKL was overexpressed in 31 of 82 (37.8 %) bladder cancer specimens. A significant association was observed between CRKL overexpression and tumor status (p = 0.019). To further explore the biological functions of CRKL in bladder cancer, we overexpressed CRKL in BIU-87 and 5637 cell lines. Using CCK8 assay and colony formation assay, we showed that CRKL upregulation increased cell proliferation. In addition, transwell assay showed that CRKL could also facilitate invasion. Further study demonstrated that CRKL upregulation increased cyclin D1 expression and ERK phosphorylation. In conclusion, CRKL is overexpressed in bladder cancer and regulates malignant cell growth and invasion, which makes CRKL a candidate therapeutic target for bladder cancer.Tumor Biology 12/2013; · 2.52 Impact Factor