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.
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.
Kok
Stanton Hon Lung
SH
Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, P.R. China.
Gambari
Roberto
R
Chui
Chung Hin
CH
Lau
Fung Yi
FY
Cheng
Gregory Yin Ming
GY
Lai
Paul Bo San
PB
Lam
Wing Sze
WS
Chan
Albert Sun Chi
AS
Cheng
Chor Hing
CH
Teo
Ivy Tuang Ngo
IT
Yu
Michael Wing Yiu
MW
Tang
Johnny Cheuk On
JC
Cheung
Filly
F
Wong
Raymond Siu Ming
RS
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
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