title: Identification of valid reference genes for gene expression studies of human stomach cancer by reverse transcription-qPCR.
abstract: BACKGROUND
  Reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) is a powerful method for the analysis of gene expression. Target gene expression levels are usually normalized to a consistently expressed reference gene also known as internal standard, in the same sample. However, much effort has not been expended thus far in the search for reference genes suitable for the study of stomach cancer using RT-qPCR, although selection of optimal reference genes is critical for interpretation of results.
  
  
  METHODS
  We assessed the suitability of six possible reference genes, beta-actin (ACTB), glyceraldehydes-3-phosphate dehydrogenase (GAPDH), hypoxanthine phosphoribosyl transferase 1 (HPRT1), beta-2-microglobulin (B2M), ribosomal subunit L29 (RPL29) and 18S ribosomal RNA (18S rRNA) in 20 normal and tumor stomach tissue pairs of stomach cancer patients and 6 stomach cancer cell lines, by RT-qPCR. Employing expression stability analyses using NormFinder and geNorm algorithms we determined the order of performance of these reference genes and their variation values.
  
  
  RESULTS
  This RT-qPCR study showed that there are statistically significant (p < 0.05) differences in the expression levels of HPRT1 and 18S rRNA in 'normal-' versus 'tumor stomach tissues'. The stability analyses by geNorm suggest B2M-GAPDH, as best reference gene combination for 'stomach cancer cell lines'; RPL29-HPRT1, for 'all stomach tissues'; and ACTB-18S rRNA, for 'all stomach cell lines and tissues'. NormFinder also identified B2M as the best reference gene for 'stomach cancer cell lines', RPL29-B2M for 'all stomach tissues', and 18S rRNA-ACTB for 'all stomach cell lines and tissues'. The comparisons of normalized expression of the target gene, GPNMB, showed different interpretation of target gene expression depend on best single reference gene or combination.
  
  
  CONCLUSIONS
  This study validated RPL29 and RPL29-B2M as the best single reference genes and combination, for RT-qPCR analysis of 'all stomach tissues', and B2M and B2M-GAPDH as the best single reference gene and combination, for 'stomach cancer cell lines'. Use of these validated reference genes should provide more exact interpretation of differential gene expressions at transcription level in stomach cancer.
authors.affiliation: Research institute, National Cancer Center, 809 Madu-dong, Goyang, Gyeonggi-do 410-769, Republic of Korea.
authors.forename: Hyun-Wook
authors.initials: HW
authors.lastname: Rho
authors.forename: Byoung-Chan
authors.initials: BC
authors.lastname: Lee
authors.forename: Eun-Seok
authors.initials: ES
authors.lastname: Choi
authors.forename: Il-Ju
authors.initials: IJ
authors.lastname: Choi
authors.forename: Yeon-Su
authors.initials: YS
authors.lastname: Lee
authors.forename: Sung-Ho
authors.initials: SH
authors.lastname: Goh
mesh_terms: D000465:Algorithms; D001779:Blood Coagulation Factors / Q000235:genetics*; D045744:Cell Line, Tumor; D020869:Gene Expression Profiling / Q000592:standards; D015972:Gene Expression Regulation, Neoplastic; D005819:Genetic Markers; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics*; D006801:Humans; D020871:RNA Stability; D016601:RNA-Binding Proteins; D012015:Reference Standards; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000592:standards; D012269:Ribosomal Proteins; D013274:Stomach Neoplasms / Q000235:genetics*; D001613:beta 2-Microglobulin / Q000235:genetics*
chemical_list: D001779:Blood Coagulation Factors; D005819:Genetic Markers; D016601:RNA-Binding Proteins; C104946:RPL29 protein, human; D012269:Ribosomal Proteins; D001613:beta 2-Microglobulin; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases