title: Housekeeping gene variability in normal and cancerous colorectal, pancreatic, esophageal, gastric and hepatic tissues.
abstract: Careful normalization is essential for the accurate quantitation of mRNA levels in biopsy-sized tissue samples. Commonly, normalization of the target gene with an endogenous standard, mainly housekeeping genes (HKGs), is applied. However, differences in the expression levels of endogenous reference genes have been reported between different tissues and pathological states. Therefore, we were challenged to identify a set of endogenous reference genes whose mRNA expression levels would not change significantly between normal and cancerous tissues. Quantitative real-time PCR (Q-RT-PCR) analysis was applied to evaluate the variability in gene expression among 21 classical housekeeping genes in colorectal, pancreatic, esophageal and gastric cancer as well as in liver metastases in comparison to the corresponding normal tissue. Our results indicated that some housekeeping genes were candidates with relatively stable gene expression in several of the investigated tissues but for most of the HKGs under investigation our data have revealed distinct differences in the extent of variability in gene expression between the different tissues and pathological states. However, for each of the five tissues investigated we found a group of genes that were expressed at a constant level thus representing a panel of candidates that we can recommend as housekeeping genes in the respective tissue types. In summary, our results can be used as guidance for other scientists studying various carcinomas for tissue-specific selection of the optimal housekeeping gene (HKG) to be used in normalizing target gene expression.
authors.affiliation: Department of General, Vascular and Paediatric Surgery, University of the Saarland, Chirurgische Klinik, Gebäude 57, Homburg/Saar 66421, Germany. ca.labor@uniklinik-saarland.de
authors.forename: Claudia
authors.initials: C
authors.lastname: Rubie
authors.forename: Katja
authors.initials: K
authors.lastname: Kempf
authors.forename: Joachim
authors.initials: J
authors.lastname: Hans
authors.forename: Tiefen
authors.initials: T
authors.lastname: Su
authors.forename: Bettina
authors.initials: B
authors.lastname: Tilton
authors.forename: Thomas
authors.initials: T
authors.lastname: Georg
authors.forename: Brigitte
authors.initials: B
authors.lastname: Brittner
authors.forename: Bianca
authors.initials: B
authors.lastname: Ludwig
authors.forename: Martin
authors.initials: M
authors.lastname: Schilling
mesh_terms: D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism; D004938:Esophageal Neoplasms / Q000235:genetics / Q000378:metabolism; D004947:Esophagus / Q000378:metabolism; D005753:Gastric Mucosa / Q000378:metabolism; D005770:Gastrointestinal Neoplasms / Q000235:genetics* / Q000378:metabolism; D041981:Gastrointestinal Tract / Q000378:metabolism*; D020869:Gene Expression Profiling; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism; D010179:Pancreas / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D012015:Reference Standards; D013274:Stomach Neoplasms / Q000235:genetics / Q000378:metabolism
chemical_list: D012333:RNA, Messenger