title: [Function of death associated protein kinase(DAPK) in colorectal cancer chemoresistance].
abstract: OBJECTIVE
  To investigate the role of death associated protein kinase(DAPK) in colon cancer drug-resistance.
  
  
  METHODS
  Immunohistochemistry was used to detect DAPK expression in colon carcinoma tissues of 61 cases and adjacent tissues of 32 cases. 5-fluorouracil (5-FU)-induced drug-resistant colon cancer cell lines HCT116/5-FU model was established. DAPK-siRNA was transfected into cells to down-regulate the DAPK gene expression (DAPK-siRNA grouyp), FAM-siRNA was transfected as control group, and DAPK over-expression plasmid vectors were constructed to up-regulate the DAPK gene expression(DAPK over-expression group). Real-time quantitative PCR and Western blotting were used to examine the mRNA and protein expression levels of DAPK, multidrug resistance protein (MRP) and P- glycoprotein (P-gp). MTT and flow cytometry were used to detect cell proliferation and apoptosis for cells treated with 5-FU (8 mg/L) and cells without treatment of 5-FU in 3 groups respectively.
  
  
  RESULTS
  Positive expression rate of DAPK in colon cancer tissues was significantly lower than that in adjacent normal tissues [18.0% (11/61) vs. 90.6% (29/32), P < 0.05]. Compared with FAM-siRNA group, DAPK mRNA and protein expression levels were significantly lower in DAPK-siRNA group, but significantly higher in DAPK over-expression group (P<0.05). After treatment of 5-FU, cell proliferation was significantly inhibited, but cell apoptosis was significantly increased in DAPK over-expression group compared to FAM-siRNA group (P < 0.05). Cell proliferation and apoptosis were not significantly different between DAPK siRNA and FAM-siRNA groups (all P < 0.05). Compared with FAM-siRNA group, DAPK over-expression could significantly reduce the mRNA and protein levels of MRP and P-gp, whereas DAPK siRNA had no obvious such effects.
  
  
  CONCLUSIONS
  DAPK can inhibit the proliferation and promote the apoptosis in drug-resistant colon cancer cells, and it probably enhances the sensitivity of cancer cells to drugs by down-regulating the mRNA and protein levels of MRP and P-gp.
authors.affiliation: Department of General Surgery, Henan Tumor Hospital, Zhengzhou 450008, China. huanghai598@163.com.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Fu
authors.forename: Yonglei
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Cheng
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Chen
authors.forename: Jianguo
authors.initials: J
authors.lastname: Xie
authors.forename: Suxia
authors.initials: S
authors.lastname: Luo
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D017209:Apoptosis; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000201:enzymology*; D064550:Death-Associated Protein Kinases / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm; D005472:Fluorouracil; D005822:Genetic Vectors; D045325:HCT116 Cells; D006801:Humans; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014162:Transfection
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D064550:Death-Associated Protein Kinases; D005472:Fluorouracil