ABSTRACT
The data presented in this article are related to the research paper entitled "Increased expression of mitochondrial sodium-coupled ascorbic acid transporter-2 (mitSVCT2) as a central feature in breast cancer", available in Free Radical Biology and Medicine Journal [1]. In this article, we examined the SVCT2 transporter expression in various breast cancer cell lines using RT-PCR and Western blot assays. In addition, we analyzed the subcellular localization of SVCT2 by immunofluorescence colocalization assays and cellular fractionation experiments. Finally, an analysis of different cancer tissue microarrays immunostained for SVCT2 and imaged by The Human Protein Atlas (https://www.proteinatlas.org) is presented.
ABSTRACT
The potential role of vitamin C in cancer prevention and treatment remains controversial. While normal human cells obtain vitamin C as ascorbic acid, the prevalent form of vitamin C in vivo, the uptake mechanisms by which cancer cells acquire vitamin C has remained unclear. The aim of this study is to characterize how breast cancer cells acquire vitamin C. For this, we determined the expression of vitamin C transporters in normal and breast cancer tissue samples, and in ZR-75, MCF-7, MDA-231 and MDA-468 breast cancer cell lines. At the same time, reduced (AA) and oxidized (DHA) forms of vitamin C uptake experiments were performed in all cell lines. We show here that human breast cancer tissues differentially express a form of SVCT2 transporter, that is systematically absent in normal breast tissues and it is increased in breast tumors. In fact, estrogen receptor negative breast cancer tissue, exhibit the most elevated SVCT2 expression levels. Despite this, our analysis in breast cancer cell lines showed that these cells are not able to uptake ascorbic acid and depend on glucose transporter for the acquisition of vitamin C by a bystander effect. This is consistent with our observations that this form of SVCT2 is completely absent from the plasma membrane and is overexpressed in mitochondria of breast cancer cells, where it mediates ascorbic acid transport. This work shows that breast cancer cells acquire vitamin C in its oxidized form and are capable of accumulated high concentrations of the reduced form. Augmented expression of an SVCT2 mitochondrial form appears to be a common hallmark across all human cancers and might have implications in cancer cells survival capacity against pro-oxidant environments.
Subject(s)
Breast Neoplasms/genetics , Mitochondria/genetics , Mitochondrial Membrane Transport Proteins/genetics , Sodium-Coupled Vitamin C Transporters/genetics , Ascorbic Acid/metabolism , Breast Neoplasms/pathology , Bystander Effect , Female , Gene Expression Regulation, Neoplastic/genetics , Humans , MCF-7 Cells , Mitochondria/pathology , Oxidation-Reduction , Reactive Oxygen Species/metabolism , Sodium/metabolismABSTRACT
El objetivo de este estudio fue evaluar el efecto de la radiación ultravioleta (UV) B sobre la expresión del factor de crecimiento transformante (TGF) ß1 por fibroblastos de mucosa oral, con el objetivo de dilucidar si este tipo celular puede contribuir a la expresión de TGFß1 en bermellón labial sobreexpuesto a la radiación UV. Se obtuvieron cultivos primarios de fibroblastos desde explantes de mucosa bucal, los que fueron irradiados con una dosis única de luz UVB (60 mJ/cm2). Se midió proliferación celular con el método MTT, y la expresión de TGFß1, a nivel de ARN mensajero (normalizado a GAPDH) por RT-PCR y a nivel de proteína mediante inmunofluorescencia. Se observó una disminución de la proliferación celular de los fibroblastos de mucosa oral a las 24 hrs post-irradiación en relación a los fibroblastos no irradiados (P<0,05, Mann Whitney). No se encontraron diferencias entre los fibroblastos control y los irradiados en la expresión de TGFß-1 ni a nivel de mensajero (0,5 y 6 h post-irradiación), ni de proteína (24 h post-irradiación). Los resultados sugieren que los fibroblastos de mucosa oral presentan una disminución de su proliferación en respuesta a una dosis única de radiación UVB, sin que se afecte la expresión de TGFß-1, la que fue similar a los fibroblastos no irradiados. Esto sugiere que los fibroblastos contribuirían a la producción de TGFß-1 en respuesta a la exposición crónica a UVB del bermellón labial.
The objective of this study was to characterize the effect of Ultraviolet (UV) B irradiation on the expression of transforming growth factor (TGF) ß1 by oral mucosa fibroblasts, in order to assess if these cells contribute to the production of TGFß-1 in UV-irradiated lip vermillion. Primary cultures of fibroblasts were obtained from oral mucosa explants, and were irradiated with a single dose of UVB light (60 mJ/cm2). The effects of UVB radiation on cell proliferation was evaluated by the MTT method. The effects of UVB on the expression of TGF-ß1 was analyzed by RT-PCR (normalized to GAPDH) and by immunofluorescence. The results showed a decrease in the proliferation of UVB-irradiated fibroblasts as compared to controls at 24h post-irradiation (p<0.05). No variations in the expression of TGFß1, both at the mRNA and protein level, were observed between control and UVB-irradiated fibroblasts during the first 24 h after irradiation. Oral mucosa fibroblasts have reduced proliferation in response to a single dose of UVB, but their expression of TGFß1 was not affected. This suggests that oral mucosa fibroblasts may contribute to the production of TGFß1 in the lip vermillion independent of UVB exposure.
