Effects of ascorbic and dehydroascorbic acid on the multiplication of tumor ascites cells in vitro

High-Dose Vitamin C in Advanced-Stage Cancer Patients

High-dose intravenously administered vitamin C (IVC) is widely used in cancer patients by complementary and alternative medicine practitioners. The most frequent indications for IVC therapy result from the belief in its effectiveness as a potent anti-cancer agent which additionally enhances chemosensitivity of cancer cells and reduces chemotherapy-related toxicities and fatigue intensity. In this narrative review, we decided to deal with this issue, trying to answer the question whether there is any scientific evidence supporting the rationale for application of high-dose IVC therapy in advanced-stage cancer patients. Although results obtained from preclinical studies demonstrated that millimolar ascorbate plasma concentrations achievable only after IVC administration were cytotoxic to fast-growing malignant cells and inhibited tumor growth as well as prolonged the survival of laboratory animals, such positive effects were not found in human studies with advanced-stage cancer patients. We also have not found the rationale for the use of IVC to increase the effectiveness of chemotherapy and to reduce the chemotherapy-induced toxicity in the above mentioned group. Nevertheless, in palliative care, high-dose IVC might be considered as a therapy improving the quality of life and reducing cancer-related symptoms, such as fatigue and bone pain. However, because of the absence of placebo-controlled randomized trials on IVC efficacy in advanced-stage cancer patients, the placebo effect cannot be excluded.

Cell damage and death by autoschizis in human bladder (RT4) carcinoma cells resulting from treatment with ascorbate and menadione

A human bladder carcinoma cell line RT4 was sham-treated with buffer or treated with ascorbate (VC) alone, menadione alone (VK(3)), or a combination of ascorbate:menadione (VC+VK(3)) for 1, 2, and 4 h. Cytotoxic damage was found to be treatment-dependent in this sequence: VC+VK(3)>VC>VK(3)>sham. The combined treatment induced the greatest oxidative stress, with early tumor cell injury affecting the cytoskeletal architecture and contributing to the self-excisions of pieces of cytoplasm freed from organelles. Additional damage, including a reduction in cell size, organelle alterations, nuclear damage, and nucleic acid degradation as well as compromised lysosome integrity, is caused by reactivation of DNases and the redox cycling of VC or VC+VK(3). In addition, cell death caused by VC+VK(3) treatment as well as by prolonged VC treatment is consistent with cell demise by autoschizis, not apoptosis. This report confirms and complements previous observations about this new mode of tumor cell death. It supports the contention that a combination of VC+VK(3), also named Apatone, could be co-administered as a nontoxic adjuvant with radiation and/or chemotherapies to kill bladder tumor cells and other cancer cells without any supplementary risk or side effects for patients.

Cell Death by Autoschizis in TRAMP Prostate Carcinoma Cells as a Result of Treatment by Ascorbate: Menadione Combination

A prostate carcinoma cell line derived from the transgenic murine prostate cancer model (TRAMP) was treated with ascorbate (VC) alone, menadione (VK(3)) alone, or a combination of ascorbate:menadione (VC + VK(3)) for 1, 2, and 4 h. Cytotoxic cell alterations examined by light and electron microscopy were treatment-dependent with VC + VK(3) > VC > VK(3). Induced by oxidative stress, these alterations included cytokeletal changes conducive to cytoplasmic blebbing, self-excisions, and progressive nuclear alterations. While the excised parts contained ribosomes, they were devoid of nuclear fragments or other organelles. The organelle-free self-excisions caused an extreme reduction in cell size as well as chromatolysis and karyolysis that were consistent with cell death by autoschizis, but not with apoptosis.

Effect of ascorbic acid on bone marrow-derived mesenchymal stem cell proliferation and differentiation

Mesenchymal stem cells (MSCs) derived from bone marrow are an important tool in tissue engineering and cell-based therapies because of their multipotent capacity. Majority of studies on MSCs have investigated the roles of growth factors, cytokines, and hormones. Antioxidants such as ascorbic acid can be used to expand MSCs while preserving their differentiation ability. Moreover, ascorbic acid can also stimulate MSC proliferation without reciprocal loss of phenotype and differentiation potency. In this study, we evaluated the effects of ascorbic acid on the proliferation, differentiation, extracellular matrix (ECM) secretion of MSCs. The MSCs were cultured in media containing various concentrations (0-500 microM) of L-ascorbate-2-phosphate (Asc-2-P) for 2 weeks, following which they were differentiated into adipocytes and osteoblasts. Ascorbic acid stimulated ECM secretion (collagen and glycosaminoglycan) and cell proliferation. Moreover, the phenotypes of the experimental groups as well as the differentiation potential of MSCs remained unchanged. The apparent absence of decreased cell density or morphologic change is consistent with the toxicity observed with 5-250 microM concentrations of Asc-2-P. The results demonstrate that MSC proliferation or differentiation depends on ascorbic acid concentration.

Morphology and DNA degeneration during autoschizic cell death in bladder carcinoma T24 cells induced by ascorbate and menadione treatment

Feulgen and actin-phalloidin staining as well as gel electrophoresis have been employed in conjunction with cell ultrastructure to describe the effects of 1-, 2-, and 4-hr ascorbate (VC), menadione (VK(3)), and ascorbate:menadione (VC:VK(3)) treatments on the T24 human bladder carcinoma cell line. T24 cells exposed to VC alone display blebs and other superficial membrane defects related to membrane alterations and to superficial cytoskeleton changes. VK(3) treatment damages the cell nucleus and organelles, leads to the redistribution of the organelles in the perikaryon as a consequence of cytoskeletal damage, and results in cytoplasmic self-excisions. After VC:VK(3) treatment, the cells show exaggerated alterations characteristic of each vitamin treatment alone, including damaged mitochondria, self-excision of organelle-free pieces of cytoplasm, and extrusion of the perikaryon containing a nucleus surrounded by the damaged organelles. The nuclear envelope appears intact and contains chromatin that decondenses and dissipates. During the cellular demise that concludes with apparent karyolysis, the cells significantly decrease their size and alter their shape. However, the cisterns of rough endoplasmic reticulum are undamaged, but may become dilated. Since the cellular phenomena leading to cell death differ morphologically from apoptosis and necrosis, but entail self-cutting without nuclear bodies, this new form of cell death was called autoschizis. In addition, gel electrophoresis and Feulgen staining demonstrate that autoschizis is accompanied by random DNA degeneration.

Inhibition of the development of metastases by dietary vitamin C:K3 combination

The tumor growth-inhibiting and chemo-potentiating effects of vitamin C and K(3)combinations have been demonstrated both in vitro and in vivo. The purpose of this study was to investigate the influence of orally administered vitamin C and K(3) on the metastasis of mouse liver tumor (T.L.T.) cells implanted in C3H mice. Adult male C3H mice were given water containing vitamin C and K3 (15 g/0.15 g dissolved in 1000 ml) beginning 2 weeks before tumor transplantation until the end of the experiment. T.L.T. cells (106) were implanted intramuscularly in the right thigh of mice. All mice were sacrificed 42 days after tumor transplantation. Primary tumor, lungs, lymph nodes and other organs or tissues suspected of harboring metastases were macroscopically examined. Samples of primary tumors, their local lymph nodes, lungs and main organs such as liver, kidneys, spleen were taken for histological examination. Forty-two percent of control mice exhibited lung metastases and 27% possessed metastases in local lymph nodes whereas 24% of vitamin-treated mice exhibited lung metastases and 10% possessed local lymph nodes metastases. The total number of lung metastases was 19 in control group and 10 in vitamin C and K(3)-treated mice. Histopathological examination of the metastatic tumors from the vitamin-treated mice revealed the presence of many tumor cells undergoing autoschizic cell death. These results demonstrate that oral vitamin C and K(3) significantly inhibited the metastases of T.L.T. tumors in C3H mice. At least a portion of this inhibition was due to tumor cell death by autoschizis.

Autoschizis of human ovarian carcinoma cells: scanning electron and light microscopy of a new cell death induced by sodium ascorbate: menadione treatment

Human ovarian carcinoma (MDAH 2774) cells were treated with sodium ascorbate (VC), menadione (VK3), or a combination of both in a ratio 100:1 for 1h and then examined with scanning electron microscopy (SEM) and light microscopy (LM). Light microscopy data corroborated SEM observations, which demonstrated that death of VC+VK3-treated tumor cells occurred primarily by autoschizis. This type of cell death is characterized by a decrease in cell size, cytoplasmic self-excisions, and nuclear and nucleolar morphologic degradations without the formation of apoptotic bodies. Ultimately, cell death results from karyorrhexis and karyolysis. This study illustrates that plasma membrane damage (branching filopodia, blisters, blebs) results from VC treatment; cytoskeletal damage and self-morsellation are caused by VC, VK3 and VC+VK, treatments. The VC treatment results in a 23% decrease in cell diameter while VK3-treated cells decrease cell diameter by 66%. After 1h of VC+VK3 treatment, a heterogenous cell population is found. This population can be resolved into one population whose diameters are 23% smaller than those of sham-treated cells, and a second population whose diameters are approximately twice those of sham-treated cells. This second population is indicative of doublet formation in which the cells appear to be dividing (an early stage of autoschizic cell death). One half of the doublet contains the cell nucleus while the other half consists of cytoplasm and membrane only. The enucleate portion of this doublet will then be excised. When the types of cell death are enumerated following VC+VK3 treatment, 43% of the cells die by autoschizis, 3% by apoptosis, and 1.9% by oncosis. These results confirm that autoschizis is the principal form of cell death that results from the in vitro treatment of human ovarian carcinoma cells with the vitamin combination.

Autoschizis: a novel cell death

Vitamin C (VC) and vitamin K(3) (VK(3)) administered in a VC:VK(3) ratio of 100:1 exhibit synergistic antitumor activity and preferentially kill tumor cells by autoschizis, a novel type of necrosis characterized by exaggerated membrane damage and progressive loss of organelle-free cytoplasm through a series of self-excisions. During this process, the nucleus becomes smaller, cell size decreases one-half to one-third of its original size, and most organelles surround an intact nucleus in a narrow rim of cytoplasm. While the mitochondria are condensed, tumor cell death does not result from ATP depletion. However, vitamin treatment induces a G(1)/S block, diminishes DNA synthesis, increases H(2)O(2) production, and decreases cellular thiol levels. These effects can be prevented by the addition of catalase to scavenge the H(2)O(2). There is a concurrent 8- to 10-fold increase in intracellular Ca(2+) levels. Electrophoretic analysis of DNA reveals degradation due to the caspase-3-independent reactivation of deoxyribonuclease I and II (DNase I, DNase II). Redox cycling of the vitamins is believed to increase oxidative stress until it surpasses the reducing ability of cellular thiols and induces Ca(2+) release, which triggers activation of Ca(2+)-dependent DNase and leads to degradation of DNA. Recent experiments indicate that oral VC:VK(3) increases the life-span of tumor-bearing nude mice and significantly reduces the growth rate of solid tumors without any significant toxicity by reactivating DNase I and II and inducing autoschizis. This report discusses the mechanisms of action employed by these vitamins to induce tumor-specific death by autoschizis.

Antioxidant nutrients and lipid peroxide levels in Thai preeclamptic pregnant women

OBJECTIVE

To compare the antioxidant nutrients and lipid peroxide levels in preeclampsia and normal pregnant women.

METHODS

Antioxidant nutrients (vitamin A and E) were measured by high-pressure liquid chromatography, vitamin C was measured by the dinitrophenyl hydrazine method, lipid peroxides were measured by the malondialdehyde method in 20 severe preeclampsia, 30 mild preeclampsia and 60 normal pregnant women as controls.

RESULTS

Vitamin C levels in severe and mild preeclampsia were significantly less than those in control group. The corrected vitamin E and vitamin A levels were significantly decreased only in severe preeclampsia. While the lipid peroxide levels in both mild and severe preeclampsia were significantly increased when compared with the nomal pregnancy.

CONCLUSIONS

Preeclampsia is associated with the imbalance between lipid peroxides and antioxidant nutrients (vitamin C and E). The imbalances favour lipid peroxides with the increasing severity of preeclampsia.

The role of ascorbic acid in oral cancer and carcinogenesis

L-ascorbic acid is an essential dietary vitamin in humans, primates and certain mammals and is endogenously synthesised in some species. Epidemiological and ecological studies have shown that L-ascorbic acid has a protective effect against cancer, in particular non-hormone-dependent malignancies, such as oropharyngeal neoplasms. Experimental in vivo and in vitro studies, however, have yielded more controversial results, suggesting that the effects of L-ascorbic acid are dose- and perhaps, time-dependent with different effects depending on the species or organ studied. An update of the epidemiological and experimental evidence linking L-ascorbic acid to oral cancer and carcinogenesis is discussed together with a brief review of the possible mechanisms of action of L-ascorbic acid.

Growth suppression of malignant leukemia cell line in vitro by ascorbic acid (vitamin C) and its derivatives

In recent years there has been a growing interest in the therapeutic application of L-ascorbic acid (AA) and its derivatives as anticancer agents. AA is a gamma-crotonolactone derivative with reactive hydroxyl groups at the 2- and 3-positions and an ethylene glycol substitution at the 4-position. Despite the various reports on AA toxicity, no work has been reported underlying the critical chemical structural features for its activity. The present study addresses this question. We tested in vivo, using malignant leukemia cell line P388D1, (i) L-AA and its isomers, (ii) substitution at the 2-position: -PO4, -SO4, O-Me, O-octadecyl, (iii) substitution at the 6-position: -PO4, -SO4, -palmitate, -stearate, (iv) substitution at the 2,6-position: dipalmitate, (v) 6-deoxy derivative: -Cl, -Br, -NH2 and (vi) dihydroxy gamma-crotonolactone with substitutions at the 4-position: -H, -CH3, -CH2-CH3 and -CH=CH2. L-AA and its isomers were very cytotoxic even at very low concentration. All 6-substituted and 6-deoxy derivatives were as toxic as AA. However, 2-substituted and 2,6-disubstituted AA derivatives were non-toxic. Interestingly, dihydroxy gamma-crotonolactone with or without substitution at the 5-position also exhibited toxicity. These results suggest that the underlying criterion for AA toxicity resides in dihydroxy gamma-crotonolactone moiety. Either substitution in the hydroxy groups or saturating the double bond render the molecule inactive.

Effect of vitamin C on prostate cancer cells in vitro: effect on cell number, viability, and DNA synthesis

BACKGROUND

Many studies describe the protective role of vitamin C (ascorbic acid) against cancer development and in treatment of established cancer. The present study investigated whether ascorbic acid demonstrates a therapeutic benefit for prostate cancer.

METHODS

Androgen-independent (DU145) and androgen-dependent (LNCaP) human prostate cancer cell lines were both treated in vitro with vitamin C (0-10 mM). Cell counts, cell viability, and thymidine incorporation into DNA were determined.

RESULTS

Treatment of DU145 and LNCaP cells with vitamin C resulted in a dose- and time-dependent decrease in cell viability and thymidine incorporation into DNA. Vitamin C induced these changes through the production of hydrogen peroxide; addition of catalase (100-300 units/ml), an enzyme that degrades hydrogen peroxide, inhibited the effects of ascorbic acid. Superoxide dismutase, an enzyme that dismutates superoxide and generates hydrogen peroxide, did not prevent decreases in cell number and DNA synthesis, suggesting further the involvement of hydrogen peroxide in vitamin C-induced changes. These results clearly indicate that reactive oxygen species (ROS) are involved in vitamin C-induced cell damage. However, that singlet oxygen scavengers such as sodium azide and hydroquinone and hydroxyl radical scavengers such as D-mannitol and DL-alpha-tocopherol did not counteract the effects of ascorbic acid on thymidine incorporation suggests that vitamin C-induced changes do not occur through the generation of these ROS.

CONCLUSIONS

Vitamin C inhibits cell division and growth through production of hydrogen peroxide, which damages the cells probably through an as yet unidentified free radical(s) generation/mechanism. Our results also suggest that ascorbic acid is a potent anticancer agent for prostate cancer cells.

Flow cytometric and ultrastructural aspects of the synergistic antitumor activity of vitamin C-vitamin K3 combinations against human prostatic carcinoma cells

Transmission and scanning electron microscopy and flow cytometry were employed to characterize the cytotoxic effects of vitamin C (VC), vitamin K3 (VK3), or VC-VK3 combinations on a human prostate carcinoma cell line (DU145) following a 1-h vitamin treatment and a 24-h incubation in culture medium. Cells exposed to VC exhibited membranous blebs, aberrant microvillar morphology, mitochondria with swollen cristae and intramitochondrial deposits, as well as nucleoli with segregated components. VK3-treated cells displayed a damaged cytoskeleton and membranes, a cytoplasm which contained large lumen, condensed polysomes, and severely damaged mitochondria with residual bodies, and nuclei which exhibited chromatic condensation, pyknosis, and karyolysis. VC-VK3-treated cells exhibited characteristics consistent with necrosis, i.e. swollen mitochondria and swollen, achromatic nuclei with marginated chromatin and intact envelopes, while other cells displayed characteristics consistent with apoptosis, i.e. expulsion of organelle-containing blebs, margination of nuclear chromatin, and segregation of nucleolar components. Vitamin treatment also decreased DNA synthesis, induced a S/G2 block in the cell cycle, and resulted in the accumulation of fragmented DNA. These results suggested that increased oxidative stress, subsequent membrane damage, and DNA fragmentation were responsible for enhanced cytotoxicity of the vitamin combination.

Synergistic antitumor activity of vitamins C and K3 on human urologic tumor cell lines

A micro-tetrazolium assay was employed to evaluate vitamin C (VC), vitamin K3 (VK3) and vitamin C/vitamin K3 combinations (VC/VK3) for their antitumor activity against eight human urologic tumor cell lines. While the individual vitamins exhibited antitumor activity at high concentrations, co-administration of the vitamins in a VC : VK3 ratio of 100 : 1 potentiated antitumor activity 4- to 61-fold even when exposure times were as short as 1 hour. Administration of exogenous catalase destroyed the antitumor activity of the vitamins and suggested that hydrogen peroxide and perhaps other reactive oxygen species were involved in the antitumor mechanism of these vitamins. Electron micrographs taken in a previous study demonstrated that vitamin treatment damaged mitochondria and may have impaired ATP synthesis. Analysis of cellular ATP and thiol levels as well as DNA and protein synthesis during the first five hours following a one hour VC/VK3 treatment, revealed: a transient increase in ATP production, a substantial decrease in DNA synthesis, an increase in protein synthesis and a decrease in thiol levels. These results suggested that redox cycling of the vitamin combination increased oxidative stress until it surpassed the reducing ability of the cellular thiols and cellular or genetic damage ensued.

6-Amino-6-deoxyascorbic acid induces apoptosis in human tumor cells

6-Amino-6-deoxyascorbic acid was found to inhibit human tumor cell growth. The antitumor effect depends on the tumor type and concentration of the acid. After cell treatment with 6-amino-6-deoxyascorbic acid, drastic morphological changes were found. Although image analysis did not show a difference in p53 and c-myc gene expression, the appearance of chromatin aggregation and DNA fragmentation points to apoptosis or programmed cell death.

Ascorbate on cell growth and differentiation

Ascorbate, an essential nutrient in humans, primates, and guinea pig, is involved in many cellular functions. Ascorbate also modulates cell growth and differentiation. Ascorbate can reduce or stimulate the growth of tumor cells, depending on the cell type. The inhibitory effect is not specific for the biological active isomer L-ascorbate, and isoascorbate and D-ascorbate are more effective in reducing cell growth than L-ascorbate. These results indicate that ascorbate has a cytotoxic effect by killing cells directly, rather a cytostatic one. However, only L-ascorbate is able to stimulate cell growth, but the mechanism of this stimulation is still unknown. L-Ascorbate stimulates the in vitro differentiation of several mesenchyme-derived cell types by altering the expression of multiple genes as the cell progresses through specific differentiation programs. Stimulation of collagen matrix at gene transcription, mRNA stabilization, hydroxylation, and secretion is a key role for L-ascorbate. L-Ascorbate also prevents cell transformation by stabilization of the differentiated state and cooperates with other agents to induce differentiation in a leukemia cell line.

Preeclampsia and antioxidant nutrients: decreased plasma levels of reduced ascorbic acid, alpha-tocopherol, and beta-carotene in women with preeclampsia

OBJECTIVE

Our purpose was to investigate the plasma levels of three potent antioxidant nutrients in women with preeclampsia.

STUDY DESIGN

Fasting venous blood samples were collected from 30 women with preeclampsia and from 44 women with uncomplicated pregnancies. The criteria for recruitment included age 15 to 35 years, gestational age 28 to 42 weeks, singleton pregnancy, intact membranes, absence of labor contractions, and absence of any other medical complication concurrent with preeclampsia. Reduced ascorbic acid, alpha-tocopherol, and beta-carotene levels were assayed with high-pressure liquid chromatography.

RESULTS

Plasma levels of reduced ascorbic acid were significantly decreased in patients with mild and severe preeclampsia (p < 0.01). Plasma alpha-tocopherol and beta-carotene levels were significantly decreased only in severe preeclampsia compared with controls (p < 0.05 and p < 0.05, respectively).

CONCLUSION

In patients with preeclampsia antioxidant nutrients may be utilized to a greater extent to counteract free radical-mediated cell disturbances, resulting in a reduction in antioxidant plasma levels. Water-soluble antioxidant nutrients may initially be consumed, followed by lipid-soluble antioxidants.

Inhibition of mitomycin C-induced sister chromatid exchanges by vitamin C in vivo

The aim of this experiment was to test the modulation of genotoxicity produced by vitamin C (V-C) challenged against mitomycin C (MMC) in vivo, by analyzing the sister chromatid exchanges (SCE) and cell proliferation kinetics. We used the mouse bone marrow cytogenetic method, and tested three dosages of V-C (3, 5, and 7 g/kg of body weight), along with the appropriate positive (2 mg MMC/kg body weight) and negative V-C controls. The results showed that V-C caused a strong inhibition of SCEs induced by MMC in the three dosages administered. The highest dose (7 g/kg) caused an SCE inhibition of 70.02%, while the lower ones caused an inhibition of 54.61% and 52.30%, respectively. It was also clear that V-C per se does not increase the level of SCEs in mouse bone marrow cells. On the other hand, V-C induced a slight decrease in cell proliferation that was stronger when combined with MMC. Our data suggest that V-C effectively inhibit the SCE damage in vivo, but caution must be taken because of the observed cytotoxicity.

Different behaviour of normal and neoplastic cells cultured in vitro in the presence of catalase and superoxide dismutase

Chicken embryo fibroblasts and hepatocytes were studied in the presence of catalase and superoxide dismutase in order to establish whether these enzymes had the capacity to favour cell multiplication as previously shown for in vitro tumour ascites cells (ATP C+). The results indicate that, unlike ATP C+ cells, both fibroblasts and hepatocytes are inhibited in their multiplication by superoxide dismutase. Similar effects are exerted on hepatocytes by catalase, whereas the multiplication of fibroblasts is favoured by high doses of this enzyme. Enzyme determinations revealed high levels of catalase and superoxide dismutase in hepatocytes, whereas both enzymes were poor in fibroblasts and ATP C+.

Antagonism between catalase and ascorbic acid in control of normal and neoplastic cell multiplication

The authors studied the effects of a treatment with ascorbic acid on in vitro multiplication of ascites tumour cells (ATP C+), of fibroblast-like cells and of hepatocytes from chick embryos, by measuring [3H]thymidine incorporation into DNA. The results obtained show that the ATP C+ cells are the most sensitive to the toxic effects of the experimental treatment, while the hepatocytes are the most resistant cell population. A treatment with catalase was able to greatly reduce the damage caused by ascorbic acid on the ATP C+ cells. It is hypothesized that ascorbic acid inhibits cell multiplication by the H2O2 formed by its oxidation and that the cells having the highest level of catalase are more resistant to its toxic effects.

Cell multiplication of an ascites tumour in the presence of superoxide dismutase and catalase

Superoxide dismutase and catalase were demonstrated to favour the multiplication of ascites tumour cells in vitro. It is proposed that these enzymes neutralize the O2-. and H2O2 that may accumulate in the neoplastic cell and that cell damage occurs because the cellular levels of both enzymes are low.

The role of ascorbic acid in carcinogenesis

Vitamin C is an essential nutrient whose protective role in carcinogenesis has been discussed for more than 50 years. Epidemiologic studies suggest that the consumption of vitamin C-rich foods is associated with a lower risk of cancers of the esophagus and stomach. The observation that cancer patients have low leukocyte vitamin C levels led to therapeutic trials the results of which are controversial; the hypothesis that vitamin C acts like a drug must be questioned. On the other hand, ascorbic acid interacts with various tumor-inducing compounds, such as the precursors of N-nitroso compounds, to prevent the formation of tumors. Experiments with animals and cell cultures indicate that ascorbic acid can interfere with the metabolism of tumor promoters. It has also been postulated that ascorbic acid helps to prevent cancer by enhancing cellular immunity. In general, evidence suggests that vitamin C can inhibit the formation of some carcinogens.