title: Paradoxical proliferative potential of iron (II) sulphate on cancer cells after the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay.
abstract: There are several scientific approaches for the determination of cellular growth influences of known or novel substances under in vitro conditions, among which colourimetric absorption measurement is considered to be one of the convenient methods. [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] (MTS) assay is one of the commonly used colourimetric absorption assays based on the ability of dehydrogenase from viable cells to produce the brown soluble formazan detectable at 490 nm. Here we have tested the possible growth influence of iron (II) sulphate on two human cancer cell lines, the K562 chronic myelogenous leukaemia and T47D breast carcinoma cells, based on the MTS assay. We found that iron (II) sulphate possessed an inhibitory effect when added at 16- to 125-microM concentrations, but iron (II) sulphate became growth stimulatory when its concentration was further increased to 1000 microM. In addition, a dose-dependent increase in absorbance at the same wavelength was observed when we repeated the experiments without the addition of MTS and phenazine methosulfate. When we further repeated the cell growth determinations using adenosine triphosphate content assay for K562 and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for T47D, iron (II) sulphate showed a consistent dose-dependent growth inhibitory effect. Morphological investigation after methylene blue staining clearly demonstrated that iron (II) sulphate, at a concentration of 1000 microM, is cytotoxic to T47D cells. Interestingly, a consistent increment for the absorbance at 490 nm was further observed with increased iron (II) sulphate concentration either in the presence or absence of MTS even in a cell-free environment. Thus we conclude that iron (II) sulphate is actually growth inhibitory and even cytotoxic at high concentrations towards the K562 and T47D cancer cells and the paradoxical proliferative activity of iron (II) sulphate on these two cancer cell lines using the MTS assay was solely due to the oxidation of initial pale green iron (II) to brownish iron (III) during incubation in the aqueous condition.
authors.affiliation: Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, P.R. China.
authors.forename: Stanton Hon Lung
authors.initials: SH
authors.lastname: Kok
authors.forename: Roberto
authors.initials: R
authors.lastname: Gambari
authors.forename: Chung Hin
authors.initials: CH
authors.lastname: Chui
authors.forename: Fung Yi
authors.initials: FY
authors.lastname: Lau
authors.forename: Gregory Yin Ming
authors.initials: GY
authors.lastname: Cheng
authors.forename: Paul Bo San
authors.initials: PB
authors.lastname: Lai
authors.forename: Wing Sze
authors.initials: WS
authors.lastname: Lam
authors.forename: Albert Sun Chi
authors.initials: AS
authors.lastname: Chan
authors.forename: Chor Hing
authors.initials: CH
authors.lastname: Cheng
authors.forename: Ivy Tuang Ngo
authors.initials: IT
authors.lastname: Teo
authors.forename: Michael Wing Yiu
authors.initials: MW
authors.lastname: Yu
authors.forename: Johnny Cheuk On
authors.initials: JC
authors.lastname: Tang
authors.forename: Filly
authors.initials: F
authors.lastname: Cheung
authors.forename: Raymond Siu Ming
authors.initials: RS
authors.lastname: Wong
mesh_terms: D001943:Breast Neoplasms / Q000473:pathology; D002277:Carcinoma / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects*; D003114:Colony-Forming Units Assay; D006801:Humans; D058085:Iron Compounds / Q000494:pharmacology*; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000473:pathology; D009369:Neoplasms / Q000473:pathology*; D013431:Sulfates / Q000494:pharmacology*; D013778:Tetrazolium Salts / Q000494:pharmacology*; D013844:Thiazoles / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D058085:Iron Compounds; D013431:Sulfates; D013778:Tetrazolium Salts; D013844:Thiazoles; C070380:3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium