title: Considerations for in vitro retinoid experiments: importance of protein interaction.
abstract: Retinoids, natural and synthetic substances structurally related to vitamin A, are important modulators of cell proliferation and differentiation, and have proven activity in cancer therapy. Experiments to reveal the mechanism of action of retinoids are routinely performed in in vitro models. As retinoids are relatively hydrophobic and unstable, we hypothesized that the composition of culture media is of critical importance for the stability and bioavailability of these compounds. Various culture media were incubated with all-trans-, 13-cis- and 9-cis-retinoic acid (RA). Without fetal calf serum (FCS) or bovine serum albumin (BSA) in the medium, the concentration of these retinoids was found to decrease to considerably low levels. This excessive loss of retinoids was due to absorption to culture plates, reaction tubes and pipet tips. Binding of retinoids to BSA was demonstrated to have attenuating effects on uptake and metabolism of all-trans-RA, as studied in oral keratinocytes and head and neck cancer cells, indicating that a balance exists between the bioavailability and the aspecific loss of retinoids. In this study we demonstrate that the type of culture medium and especially the presence of protein in the medium is of paramount importance to perform reproducible experiments with retinoids.
authors.affiliation: Section Tumor Biology, Department of Otolaryngology, University Hospital Vrije Universiteit, P.O. Box 7057, 1007 MB, Amsterdam, The Netherlands.
authors.forename: I
authors.initials: I
authors.lastname: Klaassen
authors.forename: R H
authors.initials: RH
authors.lastname: Brakenhoff
authors.forename: S J
authors.initials: SJ
authors.lastname: Smeets
authors.forename: G B
authors.initials: GB
authors.lastname: Snow
authors.forename: B J
authors.initials: BJ
authors.lastname: Braakhuis
mesh_terms: D003470:Culture Media / Q000737:chemistry*; D005312:Fetal Blood; D015603:Keratinocytes / Q000378:metabolism; D010969:Plastics / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D012176:Retinoids / Q000032:analysis / Q000737:chemistry*; D012710:Serum Albumin, Bovine; D014212:Tretinoin / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000378:metabolism
chemical_list: D003470:Culture Media; D010969:Plastics; D011506:Proteins; D012176:Retinoids; D012710:Serum Albumin, Bovine; D014212:Tretinoin