Molecular expression and functional activity of vitamin C specific transport system (SVCT2) in human breast cancer cells

Abstract

The main goal of this study is to investigate the expression of sodium dependent vitamin C transport system (SVCT2). Moreover this investigation has been carried out to define uptake mechanism and intracellular regulation of ascorbic acid (AA) in human breast cancer cells (MDA-MB231, T47D and ZR-75-1). Uptake of [14C] AA was studied in MDA-MB231, T47D and ZR-75-1 cells. Functional parameters of [14C] AA uptake were delineated in the presence of different concentrations of unlabeled AA, pH, temperature, metabolic inhibitors, substrates and structural analogs. Molecular identification of SVCT2 was carried out with reverse transcription–polymerase chain reaction (RT-PCR). Uptake of [14C] AA was studied and found to be sodium, chloride, temperature, pH and energy dependent in all breast cancer cell lines. [14C] AA uptake was found to be saturable, with Km values of 53.85±6.24, 49.69±2.83 and 45.44±3.16 μM and Vmax values of 18.45±0.50, 32.50±0.43 and 33.25±0.53 pmol/min/mg protein, across MDA-MB231, T47D and ZR-75-1, respectively. The process is inhibited by structural analogs (L-AA and D-Iso AA) but not by structurally unrelated substrates (glucose and PAHA). Ca++/calmodulin and protein kinase pathways appeared to play a crucial role in modulating AA uptake. A 626 bp band corresponding to a vitamin C transporter (SVCT2) based on the primer design was detected by RT-PCR analysis in all breast cancer cell lines. This research article describes AA uptake mechanism, kinetics, and regulation by sodium dependent vitamin C transporter (SVCT2) in MDA-MB231, T47D and ZR-75-1 cells. Also, MDA-MB231, T47D and ZR-75-1 cell lines can be utilized as a valuable in vitro model to investigate absorption and permeability of AA-conjugated chemotherapeutics.

Ascorbic acid analogue 6-Deoxy-6-[18F] fluoro-L-ascorbic acid as a tracer for identifying human colorectal cancer with SVCT2 overexpression

“…Consistent with these results, the study of Varun et al. [35] showed that radiolabeled AA uptake in breast cancer cells was significantly inhibited in the presence of unlabeled AA, whereas no substantial alteration in the uptake was observed with unlabeled DHA.…”

Selective Targeting of Cancerous Mitochondria and Suppression of Tumor Growth Using Redox-Active Treatment Adjuvant

“…The higher susceptibility of cancer cells to M/A could be also explained by the higher ascorbate and/or menadione uptake compared to normal cells [ 67 , 87 , 88 ]. It is well known that vitamin C transporters are overexpressed on the plasmatic and outer mitochondrial membranes of many types of cancer cells [ 67 , 87 , 88 ].…”

Metabolomic alterations in human cancer cells by vitamin C-induced oxidative stress

“…Chen et al 6 reported no correlations between vitamin C-induced cell death and GSH, catalase, or GPx activities. Meanwhile, the vitamin C transporter was involved in the sensitivity of breast cancer cells to vitamin C 21 22 . Furthermore, hypoxic conditions (1% O 2 ) suppressed the cytotoxicity of vitamin C more in 60 cancer cell lines than normoxic conditions (21% O 2 ) did 23 .…”