title: Expression and significance of hypoxia-inducible factor-1 alpha and MDR1/P-glycoprotein in human colon carcinoma tissue and cells.
abstract: OBJECTIVE
  Hypoxia in tumors is generally associated with chemoresistance and radioresistance. However, the correlation between the heterodimeric hypoxia-inducible factor-1 (HIF-1) and the multidrug resistance (MDR1) gene/transporter P-glycoprotein (P-gp) has not been clearly investigated. This study aims at examining the expression levels of HIF-1α and MDR1/P-gp in human colon carcinoma tissues and cell lines (HCT-116, HT-29, LoVo, and SW480) and ascertaining whether HIF-1α plays an important role in tumor multidrug resistance with MDR1/P-gp.
  
  
  METHODS
  The expression and distribution of HIF-1α and P-gp proteins were detected in human colon carcinoma tissues and cell lines by immunohistochemistry and immunocytochemistry using streptavidin/peroxidase (SP) and double-label immunofluorescence methods. HIF-1α and MDR1 mRNA expression levels in cell lines were analyzed using RT-PCR under normoxic and hypoxic conditions, respectively.
  
  
  RESULTS
  The immunohistochemical method shows that HIF-1α and P-gp expression were not correlated with gender, age, location, and differentiation degree (P > 0.05). However, the expression of HIF-1α and P-gp at different Dukes' stages and whether involved in lymphatic invasion shows a significant difference (P < 0.05). Correlation analysis displays that HIF-1α protein expression was correlated significantly with P-gp expression (P < 0.01). Double-label immunofluorescence demonstrates that coexpression of HIF-1α and P-gp does exist in human colon carcinoma tissues. The mRNA expression of HIF-1α and MDR1 was detected in the four human colon carcinoma cell lines under both normoxia and hypoxia. Optical density values representing mRNA expression levels of HIF-1α and MDR1 were found to be significantly higher in the same type cells under hypoxic conditions than that under normoxic conditions, respectively (P < 0.01). However, no significant differences of HIF-1α or MDR1 mRNA expression were found among these cell lines, which exposed under the same PaO(2) cultural conditions (P > 0.05). And the immunocytochemistry results were corresponding with the analysis of mRNA expression.
  
  
  CONCLUSIONS
  These results suggest that hypoxia induce the expression of HIF-1α and MDR1/P-gp in colon carcinoma and HIF-1α expression may be associated with the gene MDR1 (P-gp) and interactively involved in the occurrence of tumor multidrug resistance.
authors.affiliation: Department of Oncology, Southwest Hospital, Third Military Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing 400038, China.
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Ding
authors.forename: Li
authors.initials: L
authors.lastname: Yang
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Xie
authors.forename: Fangwei
authors.initials: F
authors.lastname: Xie
authors.forename: Feng
authors.initials: F
authors.lastname: Pan
authors.forename: Jianjun
authors.initials: J
authors.lastname: Li
authors.forename: Jianming
authors.initials: J
authors.lastname: He
authors.forename: Houjie
authors.initials: H
authors.lastname: Liang
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics*; D000368:Aged; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000235:genetics* / Q000473:pathology; D017931:DNA Primers; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics*; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D017931:DNA Primers; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit