title: Serum availability affects expression of common house-keeping genes in colon adenocarcinoma cell lines: implications for quantitative real-time PCR studies.
abstract: Careful selection of housekeeping genes (HKG) is prerequisite to yield sound qPCR results. HKG expression varies in response to hypoxia but the effect of manipulations of serum availability, a common experimental procedure, remains unknown. Also, no data on HKG expression stability across colon adenocarcinoma lines that would aid selection of normalizers suitable for studies involving several lines are available. Thus, we evaluated the effect of serum availability on the expression of commonly used HKG (ACTB, B2M, GAPDH, GUSB, HPRT1, IPO8, MRPL19, PGK1, PPIA, RPLP0, RPS23, SDHA, TBP, UBC, and YWHAZ) in seven colon adenocarcinoma cell lines (Caco-2, DLD-1, HCT116, HT29, Lovo, SW480, and SW620). Sets of stably expressed line-specific and pan-line HKG were validated against absolutely quantified CDKN1A, TP53, and MDK transcripts. Both serum availability and line type affected HKG expression. UBC was fourfold down-regulated and HPRT1 1.75-fold up-regulated in re-fed HT29 cultures. Line-to-line variability in HKG expression was more pronounced than that caused by altering serum availability and could be found even between isogenic cell lines. PPIA, RPLP0, YWHAZ, and IPO8 were repeatedly highly ranked while ACTB, B2M, UBC, and PGK1 were ranked poorly. Normalization against PPIA/RPLP0/SDHA was found optimal for studies involving various colon adenocarcinoma cell lines subjected to manipulations of serum availability. We found HKG expression to vary, more pronouncedly by line type than growth conditions with significant differences also between isogenic cell lines. Although using line-specific normalizers remains optimal, a set of pan-line HKG that yields good estimation of relative expression of target genes was proposed.
authors.affiliation: Department of Medical Biochemistry, Wroclaw Medical University, ul. Chalubinskiego 10, 50-368, Wroclaw, Poland. malgorzata.krzystek-korpacka@umed.wroc.pl.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Krzystek-Korpacka
authors.affiliation: Department of Medical Biochemistry, Wroclaw Medical University, ul. Chalubinskiego 10, 50-368, Wroclaw, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Hotowy
authors.affiliation: Department of Medical Biochemistry, Wroclaw Medical University, ul. Chalubinskiego 10, 50-368, Wroclaw, Poland.
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Czapinska
authors.affiliation: Department of Food Hygiene and Consumer Health, Wroclaw University of Environmental and Life Sciences, Wroclaw, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Podkowik
authors.affiliation: Department of Food Hygiene and Consumer Health, Wroclaw University of Environmental and Life Sciences, Wroclaw, Poland.
authors.forename: Jacek
authors.initials: J
authors.lastname: Bania
authors.affiliation: Department of Medical Biochemistry, Wroclaw Medical University, ul. Chalubinskiego 10, 50-368, Wroclaw, Poland.|Wroclaw Research Center EIT+, Wroclaw, Poland.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Gamian
authors.affiliation: Department of Medical Biochemistry, Wroclaw Medical University, ul. Chalubinskiego 10, 50-368, Wroclaw, Poland.
authors.forename: Iwona
authors.initials: I
authors.lastname: Bednarz-Misa
keywords: Housekeeping genes (HKG); NormFinder; Reference genes; Serum induction; Serum starvation; geNorm