Vitamin C induces human melanoma A375 cell apoptosis via Bax- and Bcl-2-mediated mitochondrial pathways

Antioxidative and Anti-Inflammatory Activity of Ascorbic Acid

Ascorbic acid, as a one of the basic exogenous vitamins, occurs in the body in the form of ascorbate, known for its strong antioxidant and anti-inflammatory properties. The presented review shows not only the importance of ascorbate as a free radical scavenger but also summarizes its antioxidant action based on other mechanisms, including the activation of intracellular antioxidant systems and its effect on the NFκB/TNFα pathway and apoptosis. Ascorbate interacts with small-molecule antioxidants, including tocopherol, glutathione, and thioredoxin; it can also stimulate biosynthesis and the activation of antioxidant enzymes, such as superoxide dismutase, catalase, or glutathione peroxidase. Moreover, ascorbate promotes the activity of transcription factors (Nrf2, Ref-1, AP-1), which enables the expression of genes encoding antioxidant proteins. Additionally, it supports the action of other exogenous antioxidants, mainly polyphenols. In this regard, both DNA, proteins, and lipids are protected against oxidation, leading to an inflammatory reaction and even cell death. Although ascorbate has strong antioxidant properties, it can also have pro-oxidant effects in the presence of free transition metals. However, its role in the prevention of DNA mutation, inflammation, and cell apoptosis, especially in relation to cancer cells, is controversial.

Drug repurposing-an emerging strategy in cancer therapeutics

Cancer is a complex disease affecting millions of people around the world. Despite advances in surgical and radiation therapy, chemotherapy continues to be an important therapeutic option for the treatment of cancer. The current treatment is expensive and has several side effects. Also, over time, cancer cells develop resistance to chemotherapy, due to which there is a demand for new drugs. Drug repurposing is a novel approach that focuses on finding new applications for the old clinically approved drugs. Current advances in the high-dimensional multiomics landscape, especially proteomics, genomics, and computational omics-data analysis, have facilitated drug repurposing. The drug repurposing approach provides cheaper, effective, and safe drugs with fewer side effects and fastens the process of drug development. The review further delineates each repurposed drug's original indication and mechanism of action in cancer. Along with this, the article also provides insight upon artificial intelligence and its application in drug repurposing. Clinical trials are vital for determining medication safety and effectiveness, and hence the clinical studies for each repurposed medicine in cancer, including their stages, status, and National Clinical Trial (NCT) identification, are reported in this review article. Various emerging evidences imply that repurposing drugs is critical for the faster and more affordable discovery of anti-cancerous drugs, and the advent of artificial intelligence-based computational tools can accelerate the translational cancer-targeting pipeline.

Polymeric Iron Chelators Enhancing Pro-Oxidant Antitumor Efficacy of Vitamin C by Inhibiting the Extracellular Fenton Reaction

Intravenously injected high-dose vitamin C (VC) induces extracellular H₂O₂, which can penetrate into the tumor cells and suppress tumor growth. However, extracellular labile iron ions in the tumor decompose H₂O₂ via the Fenton reaction, limiting the therapeutic effect. In this regard, we recently developed a polymeric iron chelator that can inactivate the intratumoral labile iron ions. Here, we examined the effect of our polymeric iron chelator on the high-dose VC therapy in in vitro and in vivo. In the in vitro study, the polymeric iron chelator could inactivate the extracellular labile iron ions and prevent the unfavorable decomposition of VC-induced H₂O₂, augmenting pro-oxidative damage to DNA and inducing apoptosis in cultured cancer cells. Even in the in vivo study, the polymeric iron chelator significantly improved the antitumor effect of VC in subcutaneous DLD-1 and CT26 tumors in mice, while conventional iron chelators could not. This work indicates the importance of modulating tumor-associated iron ions in the high-dose VC therapy and should contribute to a better understanding of its mechanism.

High-dose intravenous vitamin C, a promising multi-targeting agent in the treatment of cancer

Mounting evidence indicates that vitamin C has the potential to be a potent anti-cancer agent when administered intravenously and in high doses (high-dose IVC). Early phase clinical trials have confirmed safety and indicated efficacy of IVC in eradicating tumour cells of various cancer types. In recent years, the multi-targeting effects of vitamin C were unravelled, demonstrating a role as cancer-specific, pro-oxidative cytotoxic agent, anti-cancer epigenetic regulator and immune modulator, reversing epithelial-to-mesenchymal transition, inhibiting hypoxia and oncogenic kinase signalling and boosting immune response. Moreover, high-dose IVC is powerful as an adjuvant treatment for cancer, acting synergistically with many standard (chemo-) therapies, as well as a method for mitigating the toxic side-effects of chemotherapy. Despite the rationale and ample evidence, strong clinical data and phase III studies are lacking. Therefore, there is a need for more extensive awareness of the use of this highly promising, non-toxic cancer treatment in the clinical setting. In this review, we provide an elaborate overview of pre-clinical and clinical studies using high-dose IVC as anti-cancer agent, as well as a detailed evaluation of the main known molecular mechanisms involved. A special focus is put on global molecular profiling studies in this respect. In addition, an outlook on future implications of high-dose vitamin C in cancer treatment is presented and recommendations for further research are discussed.

Vitamin C Cytotoxicity and Its Effects in Redox Homeostasis and Energetic Metabolism in Papillary Thyroid Carcinoma Cell Lines

High-dose of vitamin C (L-ascorbic acid, ascorbate) exhibits anti-tumoral effects, primarily mediated by pro-oxidant mechanisms. This cytotoxic effect is thought to affect the reciprocal crosstalk between redox balance and cell metabolism in different cancer types. Vitamin C also inhibits the growth of papillary thyroid carcinoma (PTC) cells, although the metabolic and redox effects remain to be fully understood. To shed light on these aspects, PTC-derived cell lines harboring the most common genetic alterations characterizing this tumor were used. Cell viability, apoptosis, and the metabolome were explored by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test (MTT), flow cytometry, and UHPLC/MS. Changes were observed in redox homeostasis, with increased reactive oxygen species (ROS) level and perturbation in antioxidants and electron carriers, leading to cell death by both apoptosis and necrosis. The oxidative stress contributed to the metabolic alterations in both glycolysis and TCA cycle. Our results confirm the pro-oxidant effect of vitamin C as relevant in triggering the cytotoxicity in PTC cells and suggest that inhibition of glycolysis and alteration of TCA cycle via NAD⁺ depletion can play an important role in this mechanism of PTC cancer cell death.

Phycocyanin from Arthrospira platensis as Potential Anti-Cancer Drug: Review of In Vitro and In Vivo Studies

The application of cytostatic drugs or natural substances to inhibit cancer growth and progression is an important and evolving subject of cancer research. There has been a surge of interest in marine bioresources, particularly algae, as well as cyanobacteria and their bioactive ingredients. Dried biomass products of Arthrospira and Chlorella have been categorized as “generally recognized as safe” (GRAS) by the US Food and Drug Administration (FDA). Of particular importance is an ingredient of Arthrospira: phycocyanin, a blue-red fluorescent, water-soluble and non-toxic biliprotein pigment. It is reported to be the main active ingredient of Arthrospira and was shown to have therapeutic properties, including anti-oxidant, anti-inflammatory, immune-modulatory and anti-cancer activities. In the present review, in vitro and in vivo data on the effects of phycocyanin on various tumor cells and on cells from healthy tissues are summarized. The existing knowledge of underlying molecular mechanisms, and strategies to improve the efficiency of potential phycocyanin-based anti-cancer therapies are discussed.

Vitamin C Transporters and Their Implications in Carcinogenesis

Vitamin C is implicated in various bodily functions due to its unique properties in redox homeostasis. Moreover, vitamin C also plays a great role in restoring the activity of 2-oxoglutarate and Fe²⁺ dependent dioxygenases (2-OGDD), which are involved in active DNA demethylation (TET proteins), the demethylation of histones, and hypoxia processes. Therefore, vitamin C may be engaged in the regulation of gene expression or in a hypoxic state. Hence, vitamin C has acquired great interest for its plausible effects on cancer treatment. Since its conceptualization, the role of vitamin C in cancer therapy has been a controversial and disputed issue. Vitamin C is transferred to the cells with sodium dependent transporters (SVCTs) and glucose transporters (GLUT). However, it is unknown whether the impaired function of these transporters may lead to carcinogenesis and tumor progression. Notably, previous studies have identified SVCTs’ polymorphisms or their altered expression in some types of cancer. This review discusses the potential effects of vitamin C and the impaired SVCT function in cancers. The variations in vitamin C transporter genes may regulate the active transport of vitamin C, and therefore have an impact on cancer risk, but further studies are needed to thoroughly elucidate their involvement in cancer biology.

Inhibition of caspase-3-mediated GSDME-derived pyroptosis aids in noncancerous tissue protection of squamous cell carcinoma patients during cisplatin-based chemotherapy

The side effects of platinum-based chemotherapy are important factors limiting the survival of oral squamous cell carcinoma (OSCC) patients. Current research suggests that pyroptosis is involved in this process. However, how this mechanism can be used to reduce side effects has not yet been elucidated. In this study, we reported that GSDME was expressed at higher levels in normal tissues than in cancerous tissues in OSCC patients and was the main cause of platinum-based side effects. In an OSCC xenograft model, the inflammatory status and GSDME expression were increased after cisplatin chemotherapy. Cellular experiments showed that higher expression of GSDME was associated with less chemoresistance to cisplatin. A subsequent study demonstrated that cisplatin treatment promotes the maturation of caspase-3, triggers GSDME-mediated pyroptosis and induces cell death. When the amino acid sequence of GSDME cleaved by caspase-3 was mutated, cellular death and pyroptosis induced by cisplatin were significantly inhibited. Moreover, application of vitamin D during cisplatin-based chemotherapy could successfully inhibit GSDME cleavage and pyroptotic cell death in vitro and in vivo. Taken together, our study revealed that vitamin D can inhibit caspase-3-mediated GSDME cleavage and thus reduce normal tissue pyroptosis, relieving chemotherapeutic side effects. Inhibition of systemic GSDME during chemotherapy is currently unachievable. Vitamin D supplementation during chemotherapy in OSCC patients might be able to reduce the process described above and benefit patients. However, additional follow-up clinical studies are needed.

Vitamin C as an Anticancer Agent: Regulation of Signaling Pathways

Treatment options for effective treatment of cancer with minimum off-target effects and maximum clinical outcomes have remained overarching goals in the clinical oncology. Vitamin C has remained in the shadows of controversy since the past few decades; burgeoning evidence has started to shed light on wide-ranging anticancer effects exerted by Vitamin C to induce apoptosis in drug-resistant cancer cells, inhibit uncontrolled proliferation of the cancer cells and metastatic spread. Landmark achievements in molecular oncology have ushered in a new era, and researchers have focused on the identification of oncogenic pathways regulated by Vitamin C in different cancers. However, there are visible knowledge gaps in our understanding related to the ability of Vitamin C to modulate a myriad of transduction cascades. There are scattered pieces of scientific evidence about promising potential of Vitamin C to regulate JAK-STAT, TGF/SMAD, TRAIL and microRNAs in different cancers. However, published data is insufficient and needs to be investigated comprehensively to enable basic and clinical researchers to reap full benefits and promote result-oriented transition of Vitamin C into various phases of clinical trials. In this review, we will emphasize on available evidence related to the regulation of oncogenic cell signaling pathways by Vitamin C in different cancers. We will also highlight the conceptual gaps, which need detailed and cutting-edge research.

Omega-3PUFA Attenuates MNU-Induced Colorectal Cancer in Rats by Blocking PI3K/AKT/Bcl-2 Signaling

Background

Omega 3 polyunsaturated fatty acid (Omega-3PUFA) is one of the essential nutrients for human body involved in intracellular metabolic regulation and cell signaling. Previous studies have shown that Omega-3PUFA is involved in the pathogenesis of digestive system tumors, including colorectal cancer (CRC), however, the effects of Omega-3PUFA on CRC has not been fully elucidated. In the current study, we evaluated whether Omega-3PUFA can alleviate N-methyl-N-nitrosourea(MNU) induced CRC in a rat model and illustrated the potential mechanism.

Methods

The effects of Omga-3PUFA on MNU-induced colorectal cancer in rats were analyzed by in vivo experiments. The viability, apoptosis, colony formation and invasion of CRC cells treated with Omga-3PUFA were detected by CCK8, flow cytometry, clone formation assay and transwell invasion assay. The expression of apoptosis-related proteins in CRC cells treated with Omga-3PUFA was detected by Western blotting. Finally, after adding PI3K activator, the viability, apoptosis and protein expression of CRC cells treated with Omga-3PUFA were detected by CCK8, flow cytometry and Western blotting.

Results

Our results showed that Omega-3PUFA attenuated MNU-induced CRC in rats and inhibited AKT/Bcl-2 signaling in rats. In addition, Omega-3PUFA inhibited CRC cell proliferation and induces CRC cell apoptosis. Moreover, Omega-3PUFA inhibited CRC cell colony formation and invasion, and inhibited PI3K/AKT/Bcl-2 signaling in CRC cells. Furthermore, The effects of Omega-3PUFA on cell proliferation and apoptosis were inhibited by blocking PI3K/AKT signaling.

Conclusion

Omega-3PUFA can attenuate MNU-induced colorectal cancer in rats by blocking PI3K/AKT/Bcl-2 signaling, which suggests that Omega-3PUFA may be a potent agent for CRC treatment.