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The ROS-induced cytotoxicity of ascorbate is attenuated by hypoxia and HIF-1alpha in the NCI60 cancer cell lines.

ABSTRACT: Intravenous application of high-dose ascorbate is used in complementary palliative medicine to treat cancer patients. Pharmacological doses of ascorbate in the mM range induce cytotoxicity in cancer cells mediated by reactive oxygen species (ROS), namely hydrogen peroxide and ascorbyl radicals. However, little is known about intrinsic or extrinsic factors modulating this ascorbate-mediated cytotoxicity. Under normoxia and hypoxia, ascorbate IC50 values were determined on the NCI60 cancer cells. The cell cycle, the influence of cobalt chloride-induced hypoxia-inducible factor-1? (HIF-1?) and the glucose transporter 1 (GLUT-1) expression (a pro-survival HIF-1?-downstream-target) were analysed after ascorbate exposure under normoxic and hypoxic conditions. The amount of ascorbyl radicals increased with rising serum concentrations. Hypoxia (0.1% O2 ) globally increased the IC50 of ascorbate in the 60 cancer cell lines from 4.5 ± 3.6 mM to 10.1 ± 5.9 mM (2.2-fold increase, P < 0.001, Mann-Whitney t-test), thus inducing cellular resistance towards ascorbate. This ascorbate resistance depended on HIF-1?-signalling, but did not correlate with cell line-specific expression of the ascorbate transporter GLUT-1. However, under normoxic and hypoxic conditions, ascorbate treatment at the individual IC50 reduced the expression of GLUT-1 in the cancer cells. Our data show a ROS-induced, HIF-1?- and O2 -dependent cytotoxicity of ascorbate on 60 different cancer cells. This suggests that for clinical application, cancer patients should additionally be oxygenized to increase the cytotoxic efficacy of ascorbate.

SUBMITTER: Sinnberg T

PROVIDER: S-EPMC3955158 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature

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The ROS-induced cytotoxicity of ascorbate is attenuated by hypoxia and HIF-1alpha in the NCI60 cancer cell lines.

Sinnberg Tobias T Noor Seema S Venturelli Sascha S Berger Alexander A Schuler Paul P Garbe Claus C Busch Christian C

Journal of cellular and molecular medicine 20131214 3

Intravenous application of high-dose ascorbate is used in complementary palliative medicine to treat cancer patients. Pharmacological doses of ascorbate in the mM range induce cytotoxicity in cancer cells mediated by reactive oxygen species (ROS), namely hydrogen peroxide and ascorbyl radicals. However, little is known about intrinsic or extrinsic factors modulating this ascorbate-mediated cytotoxicity. Under normoxia and hypoxia, ascorbate IC50 values were determined on the NCI60 cancer cells. ...[more]

PMID: 24330097

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Project description:BACKGROUND: Hypoxia-inducible factor 1 (HIF-1) is a master transcriptional regulator of genes regulating oxygen homeostasis. The HIF-1 protein is composed of two HIF-1alpha and HIF-1beta/aryl hydrocarbon receptor nuclear translocator (ARNT) subunits. The prognostic relevance of HIF-1alpha protein overexpression has been shown in breast cancer. The impact of HIF-1alpha alternative splice variant expression on breast cancer prognosis in terms of metastasis risk is not well known. METHODS: Using real-time quantitative reverse transcription PCR assays, we measured mRNA concentrations of total HIF-1alpha and 4 variants in breast tissue specimens in a series of 29 normal tissues or benign lesions (normal/benign) and 53 primary carcinomas. In breast cancers HIF-1alpha splice variant levels were compared to clinicopathological parameters including tumour microvessel density and metastasis-free survival. RESULTS: HIF-1alpha isoforms containing a three base pairs TAG insertion between exon 1 and exon 2 (designated HIF-1alphaTAG) and HIF-1alpha736 mRNAs were found expressed at higher levels in oestrogen receptor (OR)-negative carcinomas compared to normal/benign tissues (P = 0.009 and P = 0.004 respectively). In breast carcinoma specimens, lymph node status was significantly associated with HIF-1alphaTAG mRNA levels (P = 0.037). Significant statistical association was found between tumour grade and HIF-1alphaTAG (P = 0.048), and total HIF-1alpha (P = 0.048) mRNA levels. HIF-1alphaTAG mRNA levels were also inversely correlated with both oestrogen and progesterone receptor status (P = 0.005 and P = 0.033 respectively). Univariate analysis showed that high HIF-1alphaTAG mRNA levels correlated with shortened metastasis free survival (P = 0.01). CONCLUSIONS: Our results show for the first time that mRNA expression of a HIF-1alphaTAG splice variant reflects a stage of breast cancer progression and is associated with a worse prognosis.See commentary: http://www.biomedcentral.com/1741-7015/8/45.

Dataset Information

The ROS-induced cytotoxicity of ascorbate is attenuated by hypoxia and HIF-1alpha in the NCI60 cancer cell lines.

Publications

The ROS-induced cytotoxicity of ascorbate is attenuated by hypoxia and HIF-1alpha in the NCI60 cancer cell lines.

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