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Synergistic effects of ascorbate and sorafenib in hepatocellular carcinoma: New insights into ascorbate cytotoxicity.

ABSTRACT: We investigated the mechanism of selective ascorbate-induced cytotoxicity in tumor cells, including Hep G2 cells, compared to primary hepatocytes. H2O2 formation was required for ascorbate cytotoxicity, as extracellular catalase treatment protected tumor cells. H2O2 generated by glucose oxidase treatment also caused cell killing, but treatment with a pharmacologic dose (5-20mM) of ascorbate was significantly more cytotoxic at comparable rates of H2O2 production, suggesting that ascorbate enhanced H2O2 cytotoxicity. This was further supported by the finding that ascorbate at a non-cytotoxic dose (1mM) enhanced cell killing caused by glucose oxidase. Consistent with this conclusion, ascorbate treatment caused deregulation of cellular calcium homeostasis, resulting in massive mitochondrial calcium accumulation. Ascorbate acted synergistically with the chemotherapeutic sorafenib in killing Hep G2 cells, but not primary hepatocytes, suggesting adjuvant ascorbate treatment can broaden sorafenib's therapeutic range. Sorafenib caused mitochondrial depolarization and prevented mitochondrial calcium sequestration. Subsequent ascorbate addition further deregulated cellular calcium homeostasis promoting cell death. Additionally, we present the case of a patient with hepatocellular carcinoma (HCC) who had prolonged regression of a rib metastasis upon combination treatment with ascorbate and sorafenib, indicating that these studies have direct clinical relevance.

SUBMITTER: Rouleau L

PROVIDER: S-EPMC4867251 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

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Synergistic effects of ascorbate and sorafenib in hepatocellular carcinoma: New insights into ascorbate cytotoxicity.

Rouleau Lauren L Antony Anil Noronha AN Bisetto Sara S Newberg Andrew A Doria Cataldo C Levine Mark M Monti Daniel A DA Hoek Jan B JB

Free radical biology & medicine 20160330

We investigated the mechanism of selective ascorbate-induced cytotoxicity in tumor cells, including Hep G2 cells, compared to primary hepatocytes. H2O2 formation was required for ascorbate cytotoxicity, as extracellular catalase treatment protected tumor cells. H2O2 generated by glucose oxidase treatment also caused cell killing, but treatment with a pharmacologic dose (5-20mM) of ascorbate was significantly more cytotoxic at comparable rates of H2O2 production, suggesting that ascorbate enhance ...[more]

PMID: 27036367

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Project description:BackgroundHepatocellular carcinoma (HCC) is a challenging malignancy of global importance, it is the third most common cause of cancer-related mortality worldwide. In the last years the multikinase inhibitor sorafenib has been used for advanced HCC, but some patients do not benefit from this therapy; thus, novel therapeutic options based on molecular approaches are urgently needed. microRNAs are short non coding RNAs involved in several physiological and pathological conditions including HCC and increasing evidence describes miRs as good tools for the molecular targeted therapies in HCC. The purpose of this study was to identify novel approaches to sensitize the HCC cells to sorafenib by microRNAs targeting urokinase-type plasminogen activator (uPA).MethodsThe miR-193a was validated as negative regulator of urokinase-type plasminogen activator (uPA) in 2 HCC undifferentiated cell lines by transient transfection of miR and anti-miR molecules. The molecular interaction between miR-193a and uPA mRNA target was verified by luciferase reporter assay. The miR-193a expression level was evaluated by stem-loop real time PCR in tumoral tissues from 39 HCC patients. The HCC cells were co-treated with sorafenib and miR-193a and the effects on cellular proliferation, apoptosis were tested. The effect of sorafenib on c-met expression levels was assessed by western blotting.ResultsThe miR-193a has resulted a negative regulator of uPA in both the HCC cell lines tested. The miR-193a expression has resulted dysregulated in tumoral tissues from 39 HCC patients. We found miR-193a down-regulation in HCC respect to peritumoral (PT) tissues and more in the cirrhotic HCCs than in non-cirrhotic ones. Transfection of HA22T/VGH HCC cells with miR-193a decreased proliferation and increased apoptosis, and combined treatment with miR-193a and sorafenib led to further proliferation inhibition.ConclusionsOur results present new advances in the post-transcriptional miR-mediated mechanisms of uPA and they suggest a new strategy to impair the aggressive behavior of HCC cells. Our findings could be helpful to explore novel approaches for multi-target and multi-agent therapies of the HCC.

Project description:BackgroundPhase III trials show sorafenib improves survival in advanced hepatocellular carcinoma (HCC). Because of narrow trial eligibility, results may not be generalizable to a broader HCC population. We sought to evaluate the effectiveness of initial sorafenib versus no treatment among Medicare beneficiaries with advanced HCC.Materials and methodsPatients with advanced HCC diagnosed from 2008 to 2011 were identified from the Surveillance, Epidemiology, and End Results-Medicare database. Eligible patients received initial sorafenib or no therapy and were covered by Medicare parts A, B, and D. Sorafenib use and outcomes were described in this population. Using a propensity score (PS)-matched sample, we compared the effectiveness of sorafenib versus no treatment by Cox proportional hazards and binomial regression, using a landmark requiring all patients to survive ?60 days after diagnosis.ResultsOf 1,532 patients, 27% received initial sorafenib. Median duration of sorafenib use was 60 days (interquartile range [IQR], 30-107 days), and median survival from first prescription was 3 months (IQR, 1-8 months). In the PS-matched cohort, median survival was 3 months from the 60-day landmark in sorafenib-treated (n = 223) and 2 months in untreated (n = 223) patients (adjusted hazard ratio, 0.95 [95% confidence interval (CI), 0.78-1.16]). Sorafenib was associated with a nonsignificant reduction in mortality at 3 months (44% versus 51%; adjusted risk ratio, 0.88 [95% CI, 0.72-1.07]), but no reduction thereafter.ConclusionSurvival after sorafenib initiation in newly diagnosed Medicare beneficiaries with HCC is exceptionally short, suggesting trial results are not generalizable to all HCC patients. The downsides of sorafenib use-high drug-related symptom burden and high drug cost-must be considered in light of this minimal benefit.Implications for practiceThe findings of a median survival of only 3 months in Medicare beneficiaries with HCC prescribed sorafenib as first-line therapy highlight the questionable value of sorafenib in this population. Patients should be cautioned that outside of the narrow confines of randomized trials, their life expectancy may be very short, and any benefit of sorafenib is likely to be quite small. Given that sorafenib causes considerable adverse effects and offers no symptom palliation, supportive care should be discussed as a reasonable alternative to sorafenib, particularly for patients who have a poor performance status or advanced cirrhosis.

Dataset Information

Synergistic effects of ascorbate and sorafenib in hepatocellular carcinoma: New insights into ascorbate cytotoxicity.

Publications

Synergistic effects of ascorbate and sorafenib in hepatocellular carcinoma: New insights into ascorbate cytotoxicity.

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