Ana Salomé Pires

Quercetin in Cancer Treatment, Alone or in Combination with Conventional Therapeutics?

Cancer is a problem of global importance, since the incidence is increasing worldwide and therapeutic options are generally limited. Thus, it becomes imperative to find new therapeutic targets as well as new molecules with therapeutic potential for tumors. Flavonoids are polyphenolic compounds that may be potential therapeutic agents. Several studies have shown that these compounds have a higher anticancer potential. Among the flavonoids in the human diet, quercetin is one of the most important. In the last decades, several anticancer properties of quercetin have been described, such as cell signaling, pro-apoptotic, anti-proliferative and anti-oxidant effects, growth suppression. In fact, it is now well known that quercetin has diverse biological effects, inhibiting multiple enzymes involved in cell proliferation, as well as, in signal transduction pathways. On the other hand, there are also studies reporting potential synergistic effects when combined quercetin with chemotherapeutic agents or radiotherapy. In fact, several studies which aim to explore the anticancer potential of these combined treatments have already been published, the majority with promising results. Actually it is well known that quercetin can act on the chemosensitization and radiosensitization but also as chemoprotective and radioprotective, protecting normal cells of the side effects that results from chemotherapy and radiotherapy, which obviously provides notable advantages in their use in anticancer treatment. Thus, all these data indicate that quercetin may have a key role in anticancer treatment. In this context, this review is focused on the relationship between flavonoids and cancer, with special emphasis on the role of quercetin.

Revisit dietary fiber on colorectal cancer: butyrate and its role on prevention and treatment.

Colorectal cancer is still a major health problem worldwide. Based on the most recent released data by the World Health Organization GLOBOCAN in 2012, colorectal cancer is the third most prevalent type of cancer in males and the second in females. In 1999, it was published the first report showing evidence of a strong correlation between diet and cancer incidence, being its positive or negative impact intimately linked to dietary patterns. A diet rich in fiber is associated with a low risk of developing colorectal cancer. The fermentation of the dietary fiber by intestinal microflora results in production of butyrate, which plays a plurifunctional role on the colonocytes, and it has also been reported as a chemopreventive agent. However, there are limited studies focusing its anti-cancer potential. Here, we review the recent new insights that focus butyrate and its role in colorectal cancer prevention and treatment, from its synthesis, metabolism, and transport, through its involvement on several cancer-related signaling pathways, to the novel existing approaches for its clinical use.

Cytotoxicity of Ascorbic Acid in a Human Colorectal Adenocarcinoma Cell Line (WiDr): In Vitro and In Vivo Studies

Vitamin C, available in its reduced form (ascorbic acid; AA) and in its oxidized form (dehydroascorbic acid; DHA), may act in physiological conditions as an antioxidant or pro-oxidant. The aim of this study is to evaluate the cytotoxic effects of pharmacological doses of AA in a human colorectal adenocarcinoma cell line (WiDr) in vitro, through spectrophotometry, clonogenic assays and flow cytometry, and in vivo with xenotransplanted Balb/c nu/nu mice. The results show that the reduced form of vitamin C induces an anti-proliferative and cytotoxic effect in adenocarcinoma colorectal cells under study. The results obtained in vivo after treatment with AA showed a large reduction in the rate of tumor growth. Such understanding can guide decisions about which colorectal cancer patients might potentially benefit from vitamin C pharmacologic therapy.

Ascorbic acid and colon cancer: an oxidative stimulus to cell death depending on cell profile

Colorectal cancer is a major health problem worldwide with urgent need for new and effective anti-cancer approaches that allow treating, increasing survival and improving life quality of patients. At pharmacological concentrations, ascorbic acid (AA) exerts a selective cytotoxic effect, whose mechanism of cytotoxicity remains unsolved. It has been suggested that it depends on the production of extracellular hydrogen peroxide, using ascorbate radical as an intermediate. The aim of this study was to evaluate the effects induced by AA in three colon cancer cell lines, as well as, possible cell death mechanisms involved. Our results showed that pharmacological concentrations of AA induce anti-proliferative, cytotoxic and genotoxic effects on three colon cancer cell lines under study. We also found that AA can induce cell death by an increment of oxidative stress, but also mediating a ROS-independent mechanism, as observed in LS1034 cells. This work explores AA anti-tumoral effects and highlights its applicability in the treatment of CC, underlying the importance of proceeding to clinical trials.

The role of immune system exhaustion on cancer cell escape and anti-tumor immune induction after irradiation.

Immune surveillance seems to represent an effective tumor suppressor mechanism. However, some cancer cells survive and become variants, being poorly immunogenic and able to enter a steady-state phase. These cells become functionally dormant or remain hidden clinically throughout. Neoplastic cells seem to be able to instruct immune cells to undergo changes promoting malignancy. Radiotherapy may act as a trigger of the immune response. After radiotherapy a sequence of reactions occurs, starting in the damage of oncogenic cells by multiple mechanisms, leading to the immune system positive feedback against the tumor. The link between radiotherapy and the immune system is evident. T cells, macrophages, Natural Killer cells and other immune cells seem to have a key role in controlling the tumor. T cells may be dysfunctional and remain in a state of T cell exhaustion, nonetheless, they often retain a high potential for successful defense against cancer, being able to be mobilized to become highly functional. The lack of clinical trials on a large scale makes data a little robust, in spite of promising information, there are still many variables in the studies relating to radiation and immune system. The clarification of the mechanisms underlying immune response to radiation exposure may contribute to treatment improvement, gain of life quality and span of patients.

Beyond the limits of oxygen: effects of hypoxia in a hormone-independent prostate cancer cell line.

Prostate cancer (PCa) has a high incidence worldwide. One of the major causes of PCa resistance is intratumoral hypoxia. In solid tumors, hypoxia is strongly associated with malignant progression and resistance to therapy, which is an indicator of poor prognosis. The antiproliferative effect and induced death caused by doxorubicin, epirubicin, cisplatin, and flutamide in a hormone-independent PCa cell line will be evaluated. The hypoxia effect on drug resistance to these drugs, as well as cell proliferation and migration, will be also analyzed. All drugs induced an antiproliferative effect and also cell death in the cell line under study. Hypoxia made the cells more resistant to all drugs. Moreover, our results reveal that long time cell exposure to hypoxia decreases cellular proliferation and migration. Hypoxia can influence cellular resistance, proliferation, and migration. This study shows that hypoxia may be a key factor in the regulation of PCa.

Butyrate, a dietary fiber derivative that improves irinotecan effect in colon cancer cells

A diet rich in fiber is associated with a low risk of developing colorectal cancer. Dietary fiber fermentation by intestinal microflora results in the production of butyrate, which has been reported as a chemopreventive agent and a histone deacetylase inhibitor (HDACi). Irinotecan is used as second-line treatment and induces adverse effects with serious life-threatening toxicities in at least 36% of patients. Our study intends to find a synergy that could improve the efficacy and decrease the toxicity of chemotherapy. Results demonstrate that milimolar concentrations of butyrate has an anti-proliferative effect in all three colon cancer cell lines under study, leading to a decrease on cell viability, expression of P21, P53 and β-catenin, being able to modulate P-glycoprotein activity and to induce apoptosis by modulation of BAX/BCL-2 ratio. Combined therapy has a cytotoxic potential, resulting in a synergistic effect, and allows a reduction in irinotecan concentration needed to reduce IC50. This potential was verified in terms of cell viability and death, cell cycle and expression of P21 and P53. Butyrate and irinotecan act synergistically in the three cancer cell lines, despite the different genetic background and location, and inhibited tumor growth in a xenograft model. Butyrate is able to influence the mechanism of LS1034 cell line chemoresistance. Butyrate in combination with chemotherapeutic agents has an important role for the treatment of colorectal cancer. Such understanding can guide decisions about which patients with colorectal cancer may benefit from therapy with butyrate demonstrating the important role of diet in colorectal cancer treatment.

Radiotherapy Effects on Immune System of Patients with Solid and Hematopoietic Tumors

Background: Radiotherapy (RT) recruits biological effectors outside the treatment field with systemic effects. Non-cancerous cells surrounding the tumor may play a pivotal role in cancer progression, as well as in metastasis. Local radiation triggers systemic effects, which in combination with immunotherapy may contribute to better treatment outcomes. Objective: The aim of this study was to evaluate RT effects on peripheral immune system (IS) in patients with lung cancer (LC) or diffuse large B cell lymphoma (DLBCL) after external beam radiotherapy. Methods: We studied a group of LC and DLBCL patients immediately before RT (T0), half-treatment (T1) and 30 days after the end of treatment (T2). Blood samples were analyzed by flow cytometry for CD3, CD4, CD8, CD19, CD56, CD25, CD127 FoxP3 expression. Procarta Cytokine Profiling kit was used to quantify cytokines and chemokines concentrations. Results: In LC patients, a decrease in B, Natural Killer (NK) and cytotoxic NK cells were observed during treatment, associated with an increase of interleukin (IL)-27 and IL-7 from T0 to T1 and followed by a decrease at T2. DLBCL patients showed increased levels of induced regulatory T cells from T1 to T2 and interferon gamma (INF-γ) over time. Comparing the two pathologies, we perceived that LC patients had increased cell subpopulation levels of IL-1β, IL-2, INF-γ, IL-5 and chemokine (C-C motif) ligand 5 compared to DLBCL patients. Conclusions: RT induces different IS responses between LC and DLBCL patients. Generally, the IS status of the patients at the beginning of the treatment can contribute to different RT treatment responses.

Radiolabelling of Ascorbic Acid: A New Clue to Clarify its Action as an Anticancer Agent?

Vitamin C exists in two forms: the reduced (ascorbic acid--AA) and oxidized form (dehydroascorbic acid--DHA). This is a nutrient whose benefits are long known and widely publicized, being most of them related to its antioxidant action. As an antioxidant, the main role of vitamin C is to neutralize free radicals, reducing oxidative stress. However, some controversial studies suggest that this nutrient may have a preventive and therapeutic role in cancer disease due to their possible pro-oxidant activity, promoting the formation of reactive oxygen species that can induce cell death in cancer cells. This factor, coupled with the decrease of antioxidant enzymes and increase of decompartmentalized transition metals in tumor cells may result in the selective cytotoxicity of vitamin C and the subsequent revelation of its therapeutic potential. In this way the first purpose of this work was radioactively label the reduced form of vitamin C with Tc-99m, its quality control by HPLC and the time stability. The second purpose was to use the radioactive complex 99mTc-AA in in vitro and in vivo studies in order to evaluate its uptake by colorectal cancer cells and biodistribution in mices, respectively. The results suggest that the pharmaceutical formulation developed, which was reproducible and stable over time, was residually taken up by colorectal cancer cells. Future studies are needed to deepen our understanding about the radioactive complex 99mTc-AA and clarify the mechanisms of action of vitamin C in oncologic disease.

Ascorbic Acid Chemosensitizes Colorectal Cancer Cells and Synergistically Inhibits Tumor Growth

Colorectal cancer (CRC) is continuously classified as one of the most incidental and mortal types of cancer worldwide. The positive outcomes of the conventional chemotherapy are frequently associated with high toxicity, which often leads to the suspension of the treatment. Growing evidences consider the use of pharmacological concentrations of ascorbic acid (AA), better known as vitamin C, in the treatment of cancer. The use of AA in a clinical context is essentially related to the adoption of new therapeutic strategies based on combination regimens, where AA plays a chemosensitizing role. The reduced sensitivity of some tumors to chemotherapy and the highly associated adverse effects continue to be some of the major obstacles in the effective treatment of CRC. So, this paper aimed to study the potential of a new therapeutic approach against this neoplasia with diminished side effects for the patient. This approach was based on the study of the combination of high concentrations of AA with reduced concentrations of drugs conventionally used in CRC patients and eligible for first and second line chemotherapeutic regimens, namely 5-fluorouracilo (5-FU), oxaliplatin (Oxa) or irinotecan (Iri). The evaluation of the potential synergy between the compounds was first assessed in vitro in three CRC cell lines with different genetic background and later in vivo using one xenograft animal model of CRC. AA and 5-FU act synergistically in vitro just for longer incubation times, however, in vivo showed no benefit compared to 5-FU alone. In contrast to the lack of synergy seen in in vitro studies with the combination of AA with irinotecan, the animal model revealed the therapeutic potential of this combination. AA also potentiated the effect of Oxa, since a synergistic effect was demonstrated, in almost all conditions and in the three cell lines. Moreover, this combined therapy (CT) caused a stagnation of the tumor growth rate, being the most promising tested combination. Pharmacological concentrations of AA increased the efficacy of Iri and Oxa against CRC, with promising results in cell lines with more aggressive phenotypes, namely, tumors with mutant or null P53 expression and tumors resistant to chemotherapy.