Original Contribution
Enhanced antitumor activity of vitamin C via p53 in Cancer cells
Highlights
► One of the reasons for differing ascorbate cytotoxicity may be the presence of p53. ► The modification of p53 expression changed ascorbate cytotoxicity. ► Ascorbate overcame the threshold level of oxidative stress, causing cell death via p53. ► p53 and MDM2 are differentially regulated by ascorbate. ► In vivo antitumor activity is enhanced by the presence of p53.
Introduction
Ascorbate (also known as vitamin C), which is generally regarded as an antioxidant, has been known as an essential micronutrient and as an unorthodox therapy for cancer treatment. Initial ascorbate treatment of cancer patients conducted by Pauling and Cameron [1] showed conflicting results with regard to efficacy [2], [3]. Despite these uncertainties, ascorbate recently has been reevaluated as a potential cancer treatment. For effective cytotoxicity, the ascorbate concentration must reach a pharmacological level that varies depending on the cancer cell line. Emerging evidence indicates that high concentrations of ascorbate can be easily achieved by intravenous or intraperitoneal injection but not by oral dosing [3], [4]. Furthermore, pharmacological concentrations of ascorbate selectively kill cancer cells but not normal cells, a characteristic of an ideal cancer drug [5].
It is still questionable, however, to apply ascorbate for clinical uses, because it has been reported that ascorbate has quite different anticancer effects on various cancer cell lines [4], [6], [7], [8]. These data demonstrate that the concentration of ascorbate that can kill one cancer cell line does not have same effect on others. This relatively different cytotoxicity of ascorbate may have caused inconsistent therapeutic outcomes. Although a major cell death pattern can be shown, it has been reported that ascorbate-mediated cell death shows a mixed pattern between apoptosis, necrosis, and cell cycle arrest [9], [10], [11]. Because ascorbate cytotoxicity differs among cancer cell lines, the cell death mechanism can be also different among cell lines. This can make it difficult for researchers or clinics to analyze or anticipate results.
According to many studies, ascorbate at pharmacological concentrations can act as a DNA-damaging stress and pro-oxidant on cancer cells [9], [12], [13]. Based on these studies, we propose that a factor(s) that regulates DNA-damaging stress and oxidative stress might be extensively involved in ascorbate cytotoxicity. Because it was shown that ascorbate exerts its cytotoxicity via hydrogen peroxide (H2O2) generation [9], an element that can modify the balance between oxidants and antioxidants in cancer cells may be very helpful in explaining the differences in ascorbate cytotoxicity. So we focused on p53, which is a major tumor suppressor and transcription factor that responds to various DNA-damaging stresses and orchestrates the transcription of genes involved in cell cycle arrest, senescence, and apoptosis [14]. It has been shown that cellular oxidative stress can be related to one of several p53-related functions that are oxidative stress-generating phenomena [15]. However, it is still debated as to what mechanisms are involved in influencing p53 to promote intracellular oxidative stress or vice versa.
An ideal anticancer agent should be toxic to malignant cells but only minimally toxic to normal cells. In this regard, ascorbate might be a good cancer therapeutic agent. However, more basic work should be done before using it as a common anticancer drug, because the mechanism of action is not fully understood. Therefore, our study has focused on the conditions providing for a more consistent therapeutic effect of ascorbate. We have examined the role of p53 as a sensitizer for ascorbate cytotoxicity and hypothesize that p53 renders cells more sensitive to ascorbate-induced oxidative stress. We found that the presence of p53 can influence ascorbate cytotoxicity, and reactivation of p53 in cancer cells enhances anticancer activity of ascorbate by increasing reactive oxygen species (ROS) generation via the p53 transcriptional network. Furthermore, ascorbate-mediated p53 activation was achieved by ubiquitination of MDM2 and activation by p38MAPK. Finally, we identified that ascorbate had similar preferential cytotoxicity on wild-type p53-bearing tumors over p53-deficient tumors in vivo, which result was similar to the in vitro p53 effect on ascorbate cytotoxicity.
Section snippets
Cell lines
Human cancer cells HCT116+/+, MCF7, HeLa, HCT116−/−, and SKOV3 were grown in Dulbecco's modified Eagle's medium (WelGene, Seoul, South Korea), and A549 and H1299 cells were maintained in RPMI 1640 medium containing 20 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid and 2 mM glutamine. All media were supplemented with 10% fetal bovine serum, 100 μg/ml penicillin, and 100 U/ml streptomycin. Cultures were grown at 37 °C in a 5% CO2 atmosphere. HCT116+/+ and HCT116−/− cells were a kind gift from
The presence of p53 influences the pharmacological concentration of ascorbate cytotoxicity
We initially examined ascorbate cytotoxicity by dose–response assays in seven cancer cell lines. The cancer cell lines we used can be classified into two groups, those expressing wild-type p53 (HCT116+/+, MCF7, A549, and HeLa) and those that are p53-deficient (HCT116−/−, H1299, and SKOV3). Our results suggest a spectrum of effective cytotoxic doses of ascorbate in the cancer cell lines with differing p53 status (Fig. 1A and Supplementary Table 1). To examine the question of p53 influence on
Discussion
A purpose of this study was to investigate a factor for improving the consistent cytotoxicity of ascorbate. Ascorbate can influence various signaling pathways that regulate the cancer microenvironment [26], [27], which can complicate comparisons that use cell lines with different genetic backgrounds to examine the mechanisms of ascorbate cytotoxicity. As already reported in many studies, p53 has been used as one of targets for effective cancer therapy [28], [29], [30]. It has been shown that
Acknowledgment
This work was supported by a National Research Foundation of Korea grant funded by the Korean government (MEST, 2011-0001381 and 2011–0030701).
References (37)
- et al.
Pharmacologic concentrations of ascorbate are achieved by parenteral administration and exhibit antitumoral effects
Free Radic. Biol. Med.
(2009) Modulation of the effects of tumor therapeutic agents by vitamin C
Life Sci.
(1980)- et al.
Cell death by oxidative stress and ascorbic acid regeneration in human neuroectodermal cell lines
Eur. J. Cancer
(1995) - et al.
High dose of ascorbic acid induces cell death in mesothelioma cells
Biochem. Biophys. Res. Commun.
(2010) - et al.
Ascorbate and H2O2 induced oxidative DNA damage in Jurkat cells
Free Radic. Biol. Med.
(2006) - et al.
A rapid colorimetric assay for the determination of IL-2-producing helper T cell frequencies
J. Immunol. Methods
(1985) - et al.
An in vitro procedure for evaluation of early stage oxidative stress in an established fish cell line applied to investigation of PHAH and pesticide toxicity
Nat. Environ. Res.
(2004) - et al.
ROS and p53: a versatile partnership
Free Radic. Biol. Med.
(2008) - et al.
The p53–Mdm2 module and the ubiquitin system
Semin. Cancer Biol.
(2003) - et al.
Differential modulation of normal and tumor cell proliferation by reactive oxygen species
Biomed. Pharmacother.
(2005)
Supplemental ascorbate in the supportive treatment of cancer: prolongation of survival times in terminal human cancer
Proc. Natl. Acad. Sci. USA
Failure of high-dose vitamin C (ascorbic acid) therapy to benefit patients with advanced cancer: a controlled trial
N. Engl. J. Med.
Vitamin C pharmacokinetics: implications for oral and intravenous use
Ann. Intern. Med.
Ascorbate in pharmacologic concentrations selectively generates ascorbate radical and hydrogen peroxide in extracellular fluid in vivo
Proc. Natl. Acad. Sci. USA
Pharmacologic doses of ascorbate act as a pro-oxidant and decrease growth of aggressive tumor xenograft in mice
Proc. Natl. Acad. Sci. USA
Pharmacologic ascorbic acid concentrations selectively kill cancer cells: action as a pro-drug to deliver hydrogen peroxide to tissues
Proc. Natl. Acad. Sci. USA
p53 enhances ascorbyl stearate-induced G2/M arrest of human ovarian cancer cells
Anticancer Res.
Sodium 5,6-benzylidene-L-ascorbate induces oxidative stress, autophagy, and growth arrest in human colon cancer HT-29 cells
J. Cell. Biochem.
Cited by (34)
-
Vitamin C-induced competitive binding of HIF-1α and p53 to ubiquitin E3 ligase CBL contributes to anti-breast cancer progression through p53 deacetylation
2022, Food and Chemical ToxicologyCitation Excerpt :VC functions as a cofactor for prolyl-hydroxylase, which is responsible for HIF-1α hydroxylation and degradation (Gan et al., 2019; Li et al., 2010; Nytko et al., 2011; Fischer and Miles, 2017). In addition, VC promotes cancer cell apoptosis by regulating p53 (Lee et al., 2015; Gong et al., 2016; Rubis et al., 2019; Kim et al., 2012). In the current study, we identified that Casitas B Cell lymphoma (CBL), as an E3 ligase of HIF-1α and p53, could balance the two genes under VC treatment.
-
Cellular landscaping of cisplatin resistance in cervical cancer
2022, Biomedicine and Pharmacotherapy -
The potential role of vitamin C in empowering cancer immunotherapy
2022, Biomedicine and PharmacotherapyCitation Excerpt :Another study has also reported that PD-L1 and p53 protein levels are correlated in patients with lung adenocarcinoma [107]. It has been shown that vitamin C treatment induces an up-regulation of p53 [108]. The mechanisms by which vitamin C modulates cytokines expression is mostly unknown.
-
Ascorbate kills breast cancer cells by rewiring metabolism via redox imbalance and energy crisis
2021, Free Radical Biology and MedicineCitation Excerpt :Several recent studies probed the molecular and cellular mechanisms, through which high levels of ascorbate damage cancer cells [22,25–27]. It has been shown that ascorbate induces oxidative stress selectively in cancer cells while normal cells are spared due to higher reductive capacity and more robust redox homeostasis [22,25,28]. Multiple reports also showed that the ascorbate-associated oxidative stress resulted in inhibited glucose uptake and glycolysis [22,29,30].
-
Antitumor and antiviral activities of 4-substituted 1,2,3-triazolyl-2,3-dibenzyl-L-ascorbic acid derivatives
2019, European Journal of Medicinal ChemistryCitation Excerpt :Even though l-ascorbic acid (L-ASA) cancer therapy has a controversial history [1], interest in L-ASA has been renewed due to its recently demonstrated ability to selectively kill cancer cells [2–5].
-
Retinol palmitate and ascorbic acid: Role in oncological prevention and therapy
2019, Biomedicine and Pharmacotherapy