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.
- SourceAvailable from: Manabu Yamamoto[show abstract] [hide abstract]
ABSTRACT: Growth factor receptor-mediated signal transduction has been implicated in conferring resistance to conventional chemotherapy on cancer cells. We describe a pathway that involves AKT/PI3K to mediate chemoresistance in gastric cancer patients. Primary gastric carcinoma tissues and corresponding normal mucosa were obtained from 76 gastric cancer patients who underwent surgery in the Department of Surgery II in Kyushu University Hospital from the years 1996-2000. AKT activation was investigated by immunostaining with a phosphorylation-specific antibody, and LOH (loss of heterozygosity) of PTEN was studied in the same samples. AKT was phosphorylated in 22 cases (28.9%) of gastric cancer cases. AKT and phosphorylated AKT were not correlated with any clinicopathological factor. We found that the gastric cancer patients who had higher AKT phosphorylation (activated AKT) seemed to have LOH of PTEN (p = 0.0008). When the chemotherapeutic sensibilities of these patients were studied in an MTT assay, it was found that the activated AKT was associated with increased resistance to multiple chemotherapeutic agents (5-fluorouracil, adriamycin, mitomycin C and cis-platinum). The results of our study indicate that AKT activation and LOH of PTEN plays an important role in conferring a broad-spectrum chemoresistance in gastric cancer patients. It also indicates that AKT may therefore be a novel molecular target for therapies or chemosensitivity tests that improve the outcomes of gastric cancer patients.International Journal of Cancer 12/2005; 117(3):376-80. · 6.20 Impact Factor
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ABSTRACT: The aim of this study was to evaluate serum midkine (S-MK) concentrations as a prognostic tumour marker in oral squamous cell carcinoma (OSCC). We measured S-MK concentrations in patients with OSCC and healthy volunteers. In addition, we performed real-time quantitative reverse transcription-PCR analysis and immunohistochemistry with fresh tumour samples. To determine whether S-MK concentrations have prognostic value, we performed survival analyses with clinical information by using the log-rank test. Serum midkine concentrations were significantly higher in patients with OSCC than in healthy controls (P<0.001). Serum midkine concentrations were also significantly increased in early-stage OSCC compared with those of healthy individuals (P<0.001). In addition, immunohistochemistry allowed identification of overexpressed MK protein in OSCC tissues. MK mRNA showed higher expression in OSCC samples compared with normal mucosal samples. Patients in high S-MK groups showed a significantly lower 5-year survival rate compared with patients in low S-MK groups (P<0.05). The increased S-MK concentrations in early-stage OSCC were strongly associated with poor survival. Serum midkine concentrations may thus be a useful marker not only for cancer screening but also for predicting prognosis of OSCC patients.British Journal of Cancer 09/2008; 99(4):655-62. · 5.08 Impact Factor
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ABSTRACT: To evaluate the in vivo antitumor effects of antisense oligonucleotides targeting midkine (MK-AS). An in situ human hepatocellular carcinoma (HCC) model was established in mice livers orthotopically. The MK-AS and 5- fluorouracil (5-Fu) were administered intravenously. The tumor sizes and plasma alpha-fetoprotein (AFP) were measured by calipers and radiation immunoassay respectively. The morphology of tumors was evaluated by hematoxylin-eosin staining of histological sections. Human MK, p53, Bax, Bcl-2, and caspase-3 protein content were detected by Western blotting. MK-AS significantly inhibited in situ human HCC growth in mice compared with the saline group in a dose-dependent manner. After the treatment with MK-AS or with 5-Fu, the plasma AFP concentration decreased in a dose-dependent manner. Interestingly, MK-AS also clearly downregulated the protein level of Bcl-2, and upregulated p53, Bax, and caspase-3 in the hepatocellular carcinoma tissue. These results demonstrated that MK-AS was an effective antitumor antisense oligonucleotide in vivo in mice; its antitumor effect is associated with the increase of pro-apoptotic proteins, such as p53, Bax, and caspase-3, and the decrease of the anti-apoptotic protein, Bcl-2.Acta Pharmacologica Sinica 04/2007; 28(3):453-8. · 2.35 Impact Factor