Prophylactic vs. Therapeutic Treatment With P2Et Polyphenol-Rich Extract Has Opposite Effects on Tumor Growth

Assessment of Acute and Chronic Toxicity in Wistar Rats (Rattus norvegicus) and New Zealand Rabbits (Oryctolagus cuniculus) of an Enriched Polyphenol Extract Obtained from Caesalpinia spinosa

Although herbal drugs are often considered safe for consumption, there is increasing evidence that some can generate undesirable health effects. However, polyphenols found in certain plants have been shown to provide a range of benefits for human health. In previous work, a standardized and quantified extract (P2Et) obtained from Caesalpinia spinosa (Dividivi) plant showed promising antioxidant, immunomodulatory, and anti-inflammatory properties in animal models of cancer and COVID-19 patients. The extract has also been subjected to genotoxicity, mutagenicity, and 28-day oral chronic toxicity evaluations, demonstrating a good safety profile. To advance preclinical and clinical development, further acute and chronic toxicity evaluations of the P2Et extract were performed. Acute toxicity tests were performed orally in Wistar rats at a dose of 2000 mg/kg, indicating that the lethal dose 50% (LD50) value exceeded 2000 mg/kg and classifying the P2Et extract as category 5 according to the Globally Harmonized System of Classification (GHS). In this work, chronic toxicity tests were conducted for 180 days on Wistar rats and New Zealand rabbits at a dose of 1000 mg/kg under Good Laboratory Practice (GLP) conditions. No weight loss or alterations in biochemical and hematological parameters associated with treatment were observed in the animals, suggesting the absence of toxicity in the assessed parameters. These results indicate that the P2Et extract is safe for oral administration at doses up to 1000 mg/kg body weight over a six-month period.

Piper nigrum extract suppresses tumor growth and enhances the antitumor immune response in murine models of breast cancer and melanoma

Although the antitumor effect of P. nigrum has been widely studied, research related to its possible immunomodulatory effects is relatively scarce. Here, the antitumor and immunomodulatory activity of an ethanolic extract of P. nigrum were evaluated in the murine models of 4T1 breast cancer and B16-F10 melanoma. In vitro evaluations showed that the P. nigrum extract has cytotoxic activity, induces apoptotic cell death, and has a pro-oxidant effect in both cell lines, but it regulates glucose uptake differently in both lines, decreasing it in 4T1 but not in B16-F10. P. nigrum extract significantly reduced tumor size in both models and decreased the occurrence of macrometastases in 4T1 model. Evaluation of immune subpopulations by flow cytometry revealed that the P. nigrum extract significantly increases the frequency of dendritic cells and activated CD8+ T cells and decreases the frequency of myeloid-derived suppressor like cells and Tregs in the tumor microenvironment of both models but with different dynamics. Our findings strongly suggest that the P. nigrum extract exerts immunomodulatory functions, slightly related to the modulation of cellular energy metabolism, which could ultimately contribute to the promising antitumor effect of P. nigrum.

Plant-derived extracts and metabolic modulation in leukemia: a promising approach to overcome treatment resistance

Leukemic cells acquire complex and often multifactorial mechanisms of resistance to treatment, including various metabolic alterations. Although the use of metabolic modulators has been proposed for several decades, their use in clinical practice has not been established. Natural products, the so-called botanical drugs, are capable of regulating tumor metabolism, particularly in hematopoietic tumors, which could partly explain the biological activity attributed to them for a long time. This review addresses the most recent findings relating to metabolic reprogramming-Mainly in the glycolytic pathway and mitochondrial activity-Of leukemic cells and its role in the generation of resistance to conventional treatments, the modulation of the tumor microenvironment, and the evasion of immune response. In turn, it describes how the modulation of metabolism by plant-derived extracts can counteract resistance to chemotherapy in this tumor model and contribute to the activation of the antitumor immune system.

Modulation of Myeloid-Derived Suppressor Cells in the Tumor Microenvironment by Natural Products

During carcinogenesis, the microenvironment plays a fundamental role in tumor progression and resistance. This tumor microenvironment (TME) is characterized by being highly immunosuppressive in most cases, which makes it an important target for the development of new therapies. One of the most important groups of cells that orchestrate immunosuppression in TME is myeloid-derived suppressor cells (MDSCs), which have multiple mechanisms to suppress the immune response mediated by T lymphocytes and thus protect the tumor. In this review, we will discuss the importance of modulating MDSCs as a therapeutic target and how the use of natural products, due to their multiple mechanisms of action, can be a key alternative for modulating these cells and thus improve response to therapy in cancer patients.

Encapsulated Phytomedicines against Cancer: Overcoming the "Valley of Death"

P2Et is the standardized extract of Caesalpinia spinosa (C. spinosa), which has shown the ability to reduce primary tumors and metastasis in animal models of cancer, by mechanisms involving the increase in intracellular Ca++, reticulum stress, induction of autophagy, and subsequent activation of the immune system. Although P2Et has been shown to be safe in healthy individuals, the biological activity and bioavailability can be increased by improving the dosage form. This study investigates the potential of a casein nanoparticle for oral administration of P2Et and its impact on treatment efficacy in a mouse model of breast cancer with orthotopically transplanted 4T1 cells. Animals were treated with either free or encapsulated oral P2Et orally or i.p. Tumor growth and macrometastases were evaluated. All P2Et treatments significantly delayed tumor growth. The frequency of macrometastasis was reduced by 1.1 times with P2Et i.p., while oral P2Et reduced it by 3.2 times and nanoencapsulation reduced it by 3.57 times. This suggests that nanoencapsulation led to higher doses of effective P2Et being delivered, slightly improving bioavailability and biological activity. Therefore, the results of this study provide evidence to consider P2Et as a potential adjuvant in the treatment of cancer, while the nanoencapsulation of P2Et provides a novel perspective on the delivery of these functional ingredients.

Tillandsia usneoides Extract Decreases the Primary Tumor in a Murine Breast Cancer Model but Not in Melanoma

The main limits of current antitumor therapies are chemoresistance, relapses, and toxicity that impair patient quality of life. Therefore, the discovery of therapeutic alternatives, such as adjuvants to conventional therapy that modulate the intracellular oxidation state or the immune response, remains a challenge. Owing to traditional medicine, several uses of plants are known, indicating a promising antitumor and immunomodulatory effect. We evaluated the effect of ethanolic extract of T. usneoides in vitro and in vivo in models of 4T1 breast cancer and B16-F10 melanoma. In vitro evaluations with both cell lines showed that the extract has cytotoxic activity and induces apoptotic cell death. However, its effect on ROS production and glucose uptake was opposite. In vivo, only in the 4T1 model, a significant decrease in tumor size was found in animals treated with the extract, accompanied by an increase in dendritic cells and activated CD8⁺ T cells, and a decrease in myeloid-derived suppressor-like cells (MDSC-LC) and Tregs in the tumor microenvironment. These results suggest that T. usneoides extract antagonistically regulates tumor metabolism of 4T1 vs. B16-F10, impacting the tumor microenvironment and effective antitumor immune response, leading to a reduction in 4T1 tumor size but not on B16-F10.

Safety Evaluation in Healthy Colombian Volunteers of P2Et Extract Obtained from Caesalpinia spinosa: Design 3+3 Phase I Clinical Trial

The polyphenol-enriched extract called P2Et derived from Caesalpinia spinosa (C. spinosa) had antitumor and immunomodulatory activities reported in breast cancer, leukemia, and melanoma. The aim of this study was to evaluate the safety and maximum tolerated dose of P2Et extract in Colombian healthy volunteers in a phase 1 clinical trial, open labelled, single-arm, dose-escalation design 3 + 3. Seven healthy volunteers were included; P2Et was administrated in capsules of 600 mg/d for 28 days. Analysis by intention to treat was performed. 4 volunteers showed adverse events and discontinued the intervention. 94.6% of AE were grade 1, and most of AE had a reasonable possibility of a relationship with the P2Et (83.8%). We found that the oral administration of P2Et is safe in healthy humans with a maximum tolerated dose of 600 mg/d. There was no severe toxicity; most of the adverse events were mild, without significant changes in the safety parameters evaluated.

Current Advancements of Plant-Derived Agents for Triple-Negative Breast Cancer Therapy through Deregulating Cancer Cell Functions and Reprogramming Tumor Microenvironment

Triple-negative breast cancer (TNBC) is defined based on the absence of estrogen, progesterone, and human epidermal growth factor receptor 2 receptors. Currently, chemotherapy is the major therapeutic approach for TNBC patients; however, poor prognosis after a standard chemotherapy regimen is still commonplace due to drug resistance. Abnormal tumor metabolism and infiltrated immune or stromal cells in the tumor microenvironment (TME) may orchestrate mammary tumor growth and metastasis or give rise to new subsets of cancer cells resistant to drug treatment. The immunosuppressive mechanisms established in the TME make cancer cell clones invulnerable to immune recognition and killing, and turn immune cells into tumor-supporting cells, hence allowing cancer growth and dissemination. Phytochemicals with the potential to change the tumor metabolism or reprogram the TME may provide opportunities to suppress cancer metastasis and/or overcome chemoresistance. Furthermore, phytochemical intervention that reprograms the TME away from favoring immunoevasion and instead towards immunosurveillance may prevent TNBC metastasis and help improve the efficacy of combination therapies as phyto-adjuvants to combat drug-resistant TNBC. In this review, we summarize current findings on selected bioactive plant-derived natural products in preclinical mouse models and/or clinical trials with focus on their immunomodulatory mechanisms in the TME and their roles in regulating tumor metabolism for TNBC prevention or therapy.

Genotoxicity and mutagenicity assessment of a standardized extract (P2Et) obtained from Caesalpinia spinosa

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The P2Et extract was assessed for genotoxicity and mutagenicity activity.

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The P2Et extract showed no genotoxicity in Micronucleus assay.

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The P2Et extract showed no mutagenicity in Ames test.

The standardized P2Et extract obtained from Caesalpinia spinosa has shown antioxidant, and direct antitumor activity, but also activation of specific immune response through the induction of tumor immunogenic cell death in breast and melanoma cancer models. The present work evaluated the mutagenicity and genotoxicity profile of P2Et to continue the development of the P2Et. Genotoxicity was evaluated by OECD 1997 a guideline and mutagenicity by OECD 2016. At P2Et’s doses of 500, 1000, and 2000 mg/kg body weight in mice (Mus musculus), the difference between the number of micronuclei in PCE of the groups were not statistically significant (17 (negative control), 15 (500 mg/kg), 15 (1000 mg/kg), 19 (2000 mg/kg) and 271 (positive control). Similarly, P2Et did not induce gene mutations by base pair changes or frameshifts in the genome of Salmonella Typhimurium strains TA98, TA100, TA102, TA1535 and TA1537 at the tested range of concentrations up to 5000 μg/plate in the absence and presence of metabolic activation. Therefore, the P2Et was considered as non- mutagenic and non-genotoxic at the conditions of the tests.

Antioxidants for the Treatment of Breast Cancer: Are We There Yet?

Breast cancer is the most frequent cancer and the leading cause of cancer death in women. Oxidative stress and the generation of reactive oxygen species (ROS) have been related to cancer progression. Compared to their normal counterparts, tumor cells show higher ROS levels and tight regulation of REDOX homeostasis to maintain a low degree of oxidative stress. Traditionally antioxidants have been extensively investigated to counteract breast carcinogenesis and tumor progression as chemopreventive agents; however, there is growing evidence indicating their potential as adjuvants for the treatment of breast cancer. Aimed to elucidate whether antioxidants could be a reality in the management of breast cancer patients, this review focuses on the latest investigations regarding the ambivalent role of antioxidants in the development of breast cancer, with special attention to the results derived from clinical trials, as well as their potential use as plausible agents in combination therapy and their power to ameliorate the side effects attributed to standard therapeutics. Data retrieved herein suggest that antioxidants play an important role in breast cancer prevention and the improvement of therapeutic efficacy; nevertheless, appropriate patient stratification based on "redoxidomics" or tumor subtype is mandatory in order to define the dosage for future standardized and personalized treatments of patients.

Preliminary chemical characterization of ethanolic extracts from Colombian plants with promising anti - Trypanosoma cruzi activity

Chagas disease is caused by Trypanosoma cruzi, and it is an important cause of morbidity and mortality in Latin America. There are no vaccines, and the chemotherapy available to treat this infection has serious side effects. In a search for alternative treatments, we determined the in vitro susceptibility of epimastigote and trypomastigote forms of T. cruzi and the cytotoxic effects on peripheral blood mononuclear cells (PBMCs) of ethanolic extracts obtained from six different plant species. The ethanolic extracts of Ageratina vacciniaefolia, Clethra fimbriata and Siparuna sessiliflora showed antiprotozoal activity against epimastigotes and low cytotoxicity in mammalian cells. However, only the ethanolic extract of C. fimbriata showed activity against T. cruzi trypomastigotes, and it had low cytotoxicity in PBMCs. An analysis on the phytochemical composition of C. fimbriata extract showed that its metabolites were primarily represented by two families of compounds: flavonoids and terpenoids. Lastly, we analyzed whether the A. vacciniaefolia, C. fimbriata, or S. sessiliflora ethanolic extracts induced IFN-γ or TNF-α production. Significantly, ethanolic extracts of C. fimbriata induced TNF-α production and S. sessiliflora induced both cytokines. In addition, C. fimbriata and S. sessiliflora induced the simultaneous secretion of IFN-γ and TNF-α in CD8⁺ T cells. The antiprotozoal and immunomodulatory activity of C. fimbriata may be related to the presence of flavonoid and triterpene compounds in the extract. Thus, these findings suggest that C. fimbriata may represent a valuable source of new bioactive compounds for the therapeutic treatment of Chagas disease that combines trypanocidal activity with the capacity to boost the immune response.

Preferential Activity of Petiveria alliacea Extract on Primary Myeloid Leukemic Blast

The need for new therapeutic approaches to improve the response in acute leukemia (AL), either by directing therapy or with new therapeutic alternatives, has been a research and clinical interest topic. We evaluated whether blasts from AL patients were sensitive ex vivo to the induction chemotherapy and whether the extracts of Petiveria alliacea (Anamu SC) and Caesalpinia spinosa (P2Et) modulated the sensitivity of leukemic cells to death. Bone marrow samples were taken from 26 patients with de novo AL and 6 in relapse, and the cytotoxicity of the extracts alone or in combination with the chemotherapeutic was evaluated by XTT. Patients were classified as good (GR) and bad responders (BR) according to the ex vivo test. 70.5% of the GR patients to the ex vivo test achieved postinduction remission to induction chemotherapy with a median overall survival of 12.50 months versus 7.23 months in the two groups. Furthermore, it was found that the ex vivo response to extracts and chemotherapeutics is heterogeneous and shows an exclusive pattern between the extracts, Anamu being the more effective in inducing cell death. The combination of extracts with chemotherapeutic agents showed synergistic or antagonistic effects in the patients' blasts. These results show that the ex vivo evaluation of the sensitivity to induction drugs using primary blasts from patients exhibits a correlation with the response to induction chemotherapy in patients. These analyses would allow establishing a system to predict response to treatment and determine ex vivo susceptibility to new therapies under development, among which is phytotherapeutics.

An Immunomodulatory Gallotanin-Rich Fraction From Caesalpinia spinosa Enhances the Therapeutic Effect of Anti-PD-L1 in Melanoma

PD-1/PD-L1 pathway plays a role in inhibiting immune response. Therapeutic antibodies aimed at blocking the PD-1/PD-L1 interaction have entered clinical development and have been approved for a variety of cancers. However, the clinical benefits are reduced to a group of patients. The research in combined therapies, which allow for a greater response, is strongly encouraging. We previously characterized a polyphenol-rich extract from Caesalpinia spinosa (P2Et) with antitumor activity in both melanoma and breast carcinoma, as well as immunomodulatory activity. We hypothesize that the combined treatment with P2Et and anti-PD-L1 can improve the antitumor response through an additive antitumor effect. We investigated the antitumor and immunomodulatory activity of P2Et and anti-PD-L1 combined therapy in B16-F10 melanoma and 4T1 breast carcinoma. We analyzed tumor growth, hematologic parameters, T cell counts, cytokine expression, and T cell cytotoxicity. In the melanoma model, combined P2Et and anti-PD-L1 therapy has the following effects: decrease in tumor size; increase in the number of activated CD4⁺ and CD8⁺ T cells; decrease in the number of suppressor myeloid cells; increase in PD-L1 expression; decrease in the frequency of CD8⁺ T cell expressing PD-1; improvement in the cytotoxic activity of T cells; and increase in the IFN γ secretion. In the breast cancer model, P2Et and PD-L1 alone or in combination show antitumor effect with no clear additive effect. This study shows that combined therapy of P2Et and anti-PD-L1 can improve antitumor response in a melanoma model by activating the immune response and neutralizing immunosuppressive mechanisms.

Evaluation of chemotherapy and P2Et extract combination in ex-vivo derived tumor mammospheres from breast cancer patients

The main cause of death by cancer is metastasis rather than local complications of primary tumors. Recent studies suggest that breast cancer stem cells (BCSCs), retains the ability to self-renew and differentiate to repopulate the entire tumor, also, they have been associated with resistance to chemotherapy and tumor recurrence, even after tumor resection. Chemotherapy has been implicated in the induction of resistant phenotypes with highly metastatic potential. Naturally occurring compounds, especially phytochemicals such as P2Et, can target different populations of cancer cells as well as BCSC, favoring the activation of immune response via immunogenic tumor death. Here, we evaluated the presence of BCSC as well as markers related to drug resistance in tumors obtained from 78 patients who had received (or not) chemotherapy before surgery. We evaluated the ex vivo response of patient tumor-derived organoids (or mammospheres) to chemotherapy alone or in combination with P2Et. A xenotransplant model engrafted with MDA-MB-468 was used to evaluate in vivo the activity of P2Et, in this model P2Et delay tumor growth. We show that patients with luminal and TNBC, and those who received neoadjuvant therapy before surgery have a higher frequency of BCSC. Further, the treatment with P2Et in mammospheres and human breast cancer cell lines improve the in vitro tumor death and decrease its viability and proliferation together with the release of immunogenic signals. P2Et could be a good co-adjuvant in antitumor therapy in patients, retarding the tumor growth by enabling the activation of the immune response.

Immune system activation by natural products and complex fractions: a network pharmacology approach in cancer treatment

Natural products and traditional herbal medicine are an important source of alternative bioactive compounds but very few plant-based preparations have been scientifically evaluated and validated for their potential as medical treatments. However, a promising field in the current therapies based on plant-derived compounds is the study of their immunomodulation properties and their capacity to activate the immune system to fight against multifactorial diseases like cancer. In this review we discuss how network pharmacology could help to characterize and validate natural single molecules or more complex preparations as promising cancer therapies based on their multitarget capacities.

Molecular mechanisms linking environmental toxicants to cancer development: Significance for protective interventions with polyphenols

Human exposure to environmental toxicants with diverse mechanisms of action is a growing concern. In addition to well-recognized carcinogens, various chemicals in environmental and occupational settings have been suggested to impact health, increasing susceptibility to cancer by inducing genetic and epigenetic changes. Accordingly, in this review, we have discussed recent insights into the pathological mechanisms of these chemicals, namely their effects on cell redox and calcium homeostasis, mitochondria and inflammatory signaling, with a focus on the possible implications for multi-stage carcinogenesis and its reversal by polyphenols. Plant-derived polyphenols, such as epigallocatechin-gallate, resveratrol, curcumin and anthocyanins reduce the incidence of cancer and can be useful nutraceuticals for alleviating the detrimental outcomes of harmful pollutants. However, development of therapies based on polyphenol administration requires further studies to validate the biological efficacy, identifying effective doses, mode of action and new delivery forms. Innovative microphysiological testing models are presented and specific proposals for future trials are given. Merging the current knowledge of multifactorial actions of specific polyphenols and chief environmental toxicants, this work aims to potentiate the delivery of phytochemical-based protective treatments to individuals at high-risk due to environmental exposure.

Recent Advances on the Anti-Inflammatory and Antioxidant Properties of Red Grape Polyphenols: In Vitro and In Vivo Studies

In this review, special emphasis will be placed on red grape polyphenols for their antioxidant and anti-inflammatory activities. Therefore, their capacity to inhibit major pathways responsible for activation of oxidative systems and expression and release of proinflammatory cytokines and chemokines will be discussed. Furthermore, regulation of immune cells by polyphenols will be illustrated with special reference to the activation of T regulatory cells which support a tolerogenic pathway at intestinal level. Additionally, the effects of red grape polyphenols will be analyzed in obesity, as a low-grade systemic inflammation. Also, possible modifications of inflammatory bowel disease biomarkers and clinical course have been studied upon polyphenol administration, either in animal models or in clinical trials. Moreover, the ability of polyphenols to cross the blood-brain barrier has been exploited to investigate their neuroprotective properties. In cancer, polyphenols seem to exert several beneficial effects, even if conflicting data are reported about their influence on T regulatory cells. Finally, the effects of polyphenols have been evaluated in experimental models of allergy and autoimmune diseases. Conclusively, red grape polyphenols are endowed with a great antioxidant and anti-inflammatory potential but some issues, such as polyphenol bioavailability, activity of metabolites, and interaction with microbiota, deserve deeper studies.

Breast Tumor Cells Highly Resistant to Drugs Are Controlled Only by the Immune Response Induced in an Immunocompetent Mouse Model

Background: The tumor cells responsible for metastasis are highly resistant to chemotherapy and have characteristics of stem cells, with a high capacity for self-regeneration and the use of detoxifying mechanisms that participate in drug resistance. In vivo models of highly resistant cells allow us to evaluate the real impact of the immune response in the control of cancer. Materials and Methods: A tumor population derived from the 4T1 breast cancer cell line that was stable in vitro and highly aggressive in vivo was obtained, characterized, and determined to exhibit cancer stem cell (CSC) phenotypes (CD44⁺, CD24⁺, ALDH⁺, Oct4⁺, Nanog⁺, Sox2⁺, and high self-renewal capacity). Orthotopic transplantation of these cells allowed us to evaluate their in vivo susceptibility to chemo and immune responses induced after vaccination. Results: The immune response induced after vaccination with tumor cells treated with doxorubicin decreased the formation of tumors and macrometastasis in this model, which allowed us to confirm the immune response relevance in the control of highly chemotherapy-resistant ALDH⁺ CSCs in an aggressive tumor model in immunocompetent animals. Conclusions: The antitumor immune response was the main element capable of controlling tumor progression as well as metastasis in a highly chemotherapy-resistant aggressive breast cancer model.

Polyphenol-rich extract induces apoptosis with immunogenic markers in melanoma cells through the ER stress-associated kinase PERK

Polyphenols elicit antitumor activities, in part, through the induction of anti- or pro-oxidant effects in cancer cells which promote priming of protective anti-tumor immunity. We recently characterized a polyphenol-rich extract from Caesalpinia spinosa (P2Et) that stimulates in vivo antitumor responses against breast and melanoma tumor models via the promotion of immunogenic cancer cell death (ICD). However, the primary mediators whereby P2Et promotes ICD remained unknown. Here, we sought to elucidate the role that severe endoplasmic reticulum (ER) stress plays in mediating P2Et-induced apoptosis and ICD in murine melanoma cells. Our findings demonstrate a substantial selective induction of specific ER-stress mediators in B16-F10 melanoma cells treated with P2Et. While knockout of the ER stress-associated PKR-like ER kinase (PERK) prevented induction of apoptosis and expression of ICD markers in P2Et-treated cells, deletion of X-box binding protein 1 (Xbp1) did not. P2Et-driven activation of PERK in melanoma cells was found to promote ER-calcium release, disrupt mitochondrial membrane potential, and trigger upregulation of ICD drivers, surface calreticulin expression, and extracellular release of ATP and HMGB1. Notably, calcium release inhibition, but not targeting of PERK-driven integrated stress responses, prevented P2Et-induced apoptosis. Collectively, these results underline the central role of PERK-directed calcium release in mediating the antitumor and immunogenic actions of P2Et in melanoma cells.

Polyphenols as Immunomodulatory Compounds in the Tumor Microenvironment: Friends or Foes?

Polyphenols are natural antioxidant compounds ubiquitously found in plants and, thus, ever present in human nutrition (tea, wine, chocolate, fruits and vegetables are typical examples of polyphenol-rich foods). Widespread evidence indicate that polyphenols exert strong antioxidant, anti-inflammatory, anti-microbial and anti-cancer activities, and thus, they are generally regarded to as all-purpose beneficial nutraceuticals or supplements whose use can only have a positive influence on the body. A closer look to the large body of results of years of investigations, however, present a more complex scenario where polyphenols exert different and, sometimes, paradoxical effects depending on dose, target system and cell type and the biological status of the target cell. Particularly, the immunomodulatory potential of polyphenols presents two opposite faces to researchers trying to evaluate their usability in future cancer therapies: on one hand, these compounds could be beneficial suppressors of peri-tumoral inflammation that fuels cancer growth. On the other hand, they might suppress immunotherapeutic approaches and give rise to immunosuppressive cell clones that, in turn, would aid tumor growth and dissemination. In this review, we summarize knowledge of the immunomodulatory effects of polyphenols with a particular focus on cancer microenvironment and immunotherapy, highlighting conceptual pitfalls and delicate cell-specific effects in order to aid the design of future therapies involving polyphenols as chemoadjuvants.

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In this review, we report on the complexity of breast cancer stem cells as key cells in the emergence of a chemoresistant tumor phenotype, and as a result, the appearance of distant metastasis in breast cancer patients. The search for mechanisms that increase sensitivity to chemotherapy and also allow activation of the tumor-specific immune response is of high priority. As we observed throughout this review, natural products isolated or in standardized extracts, such as P2Et or others, could act synergistically, increasing tumor sensitivity to chemotherapy, recovering the tumor microenvironment, and participating in the induction of a specific immune response. This, in turn, would lead to the destruction of cancer stem cells and the decrease in metastasis.

Source of Data: Relevant studies were found using the following keywords or medical subject headings (MeSH) in PubMed, and Google Scholar: “immune response” and “polyphenols” and “natural products” and “BCSC” and “therapy” and “metabolism” and “immunogenic cell death.” The focus was primarily on the most recent scientific publication.