Docosahexaenoic acid-acylated phloridzin, a novel polyphenol fatty acid ester derivative, is cytotoxic to breast cancer cells

Phlorizin, an Important Glucoside: Research Progress on Its Biological Activity and Mechanism

Phlorizin, as a flavonoid from a wide range of sources, is gradually becoming known for its biological activity. Phlorizin can exert antioxidant effects by regulating the IL-1β/IKB-α/NF-KB signaling pathway. At the same time, it exerts its antibacterial activity by reducing intracellular DNA agglutination, reducing intracellular protein and energy synthesis, and destroying intracellular metabolism. In addition, phlorizin also has various pharmacological effects such as antiviral, antidiabetic, antitumor, and hepatoprotective effects. Based on domestic and foreign research reports, this article reviews the plant sources, extraction, and biological activities of phlorizin, providing a reference for improving the clinical application of phlorizin.

Phloridzin Docosahexaenoate Inhibits Spheroid Formation by Breast Cancer Stem Cells and Exhibits Cytotoxic Effects against Paclitaxel-Resistant Triple Negative Breast Cancer Cells

The eradication of cancer stem cells (CSCs) is vital to successful cancer treatment and overall disease-free survival. CSCs are a sub-population of cells within a tumor that are defined by their capacity for continuous self-renewal and recapitulation of new tumors, demonstrated in vitro through spheroid formation. Flavonoids are a group of phytochemicals with potent anti-oxidant and anti-cancer properties. This paper explores the impact of the flavonoid precursor phloridzin (PZ) linked to the ω-3 fatty acid docosahexaenoate (DHA) on the growth of MCF-7 and paclitaxel-resistant MDA-MB-231-TXL breast cancer cell lines. Spheroid formation assays, acid phosphatase assays, and Western blotting were performed using MCF-7 cells, and the cell viability assays, Annexin-V-488/propidium iodide (PI) staining, and 7-aminoactinomycin D (7-AAD) assays were performed using MDA-MB-231-TXL cells. PZ-DHA significantly reduced spheroid formation, as well as the metabolic activity of MCF-7 breast cancer cells in vitro. Treatment with PZ-DHA also suppressed the metabolic activity of MDA-MB-231-TXL cells and led to apoptosis. PZ-DHA did not have an observable effect on the expression of the drug efflux transporters ATP-binding cassette super-family G member 2 (ABCG2) and multidrug resistance-associated protein 1 (MRP1). PZ-DHA is a potential treatment avenue for chemo-resistant breast cancer and a possible novel CSC therapy. Future pre-clinical studies should explore PZ-DHA as a chemo-preventative agent.

Polyphenols and Fish Oils for Improving Metabolic Health: A Revision of the Recent Evidence for Their Combined Nutraceutical Effects

Polyphenols and omega-3 polyunsaturated fatty acids from fish oils, i.e., eicosapentaenoic and docosahexaenoic acids, are well-recognized nutraceuticals, and their single antioxidant and anti-inflammatory properties have been demonstrated in several studies found in the literature. It has been reported that the combination of these nutraceuticals can lead to three-fold increases in glutathione peroxidase activity, two-fold increases in plasma antioxidant capacity, decreases of 50-100% in lipid peroxidation, protein carbonylation, and urinary 8-isoprotanes, as well as 50-200% attenuation of common inflammation biomarkers, among other effects, as compared to their individual capacities. Therefore, the adequate combination of those bioactive food compounds and their single properties should offer a powerful tool for the design of successfully nutritional interventions for the prevention and palliation of a plethora of human metabolic diseases, frequently diet-induced, whose etiology and progression are characterized by redox homeostasis disturbances and a low-grade of chronic inflammation. However, the certain mechanisms behind their biological activities, in vivo interaction (both between them and other food compounds), and their optimal doses and consumption are not well-known yet. Therefore, we review here the recent evidence accumulated during the last decade about the cooperative action between polyphenols and fish oils against diet-related metabolic alterations, focusing on the mechanisms and pathways described and the effects reported. The final objective is to provide useful information for strategies for personalized nutrition based on these nutraceuticals.

Current methodologies to refine bioavailability, delivery, and therapeutic efficacy of plant flavonoids in cancer treatment

Over the last two decades, several advancements have been made to improve the therapeutic efficacy of plant flavonoids, especially in cancer treatment. Factors such as low bioavailability, poor flavonoid stability and solubility, ineffective targeted delivery, and chemo-resistance hinder the application of flavonoids in anti-cancer therapy. Many anti-cancer compounds failed in the clinical trials because of unexpected altered clearance of flavonoids, poor absorption after administration, low efficacy, and/or adverse effects. Hence, the current research strategies are focused on improving the therapeutic efficacy of plant flavonoids, especially by enhancing their bioavailability through combination therapy, engineering gut microbiota, regulating flavonoids interaction with adenosine triphosphate binding cassette efflux transporters, and efficient delivery using nanocrystal and encapsulation technologies. This review aims to discuss different methodologies with examples from reported dietary flavonoids that showed an enhanced anti-cancer efficacy in both in vitro and in vivo models. Further, the review discusses the recent progress in biochemical modifications of flavonoids to improve bioavailability, solubility, and therapeutic efficacy.

Assessing the Impact of Phytochemicals on Immune Checkpoints: Implications for Cancer Immunotherapy

Phytochemicals are the basis for many anticancer drugs currently in clinical use, as well as a potential source of future cancer treatments. Some phytochemicals have been found to modify the expression of checkpoint inhibitors of the immune response, as well as kill cancer cells. Cancer cells, in turn, may evade detection by the immune system by expressing molecules such as programmed death ligand 1 (PD-L1) that interacts with programmed cell death 1 (PD-1) on T cells to inhibit T cell activation and effector function. Phytochemicals have direct effects on cancer cells and/or T cells that may impact PD-L1/PD1 interactions, although this may vary depending on the phytochemical in question. Flow cytometric analysis of cancer cells stained with anti-PD-L1 antibodies following treatment with a given phytochemical enables the detection of any alteration in PD-L1 expression. The effect of the phytochemical on T cell function can be assessed using proliferation assays (e.g., tritiated thymidine incorporation, flow cytometric analysis of Oregon Green 488-stained cells) and enzyme-linked immunosorbent assay of interleukin-2 content in culture supernatants. Additional study is needed to better understand the impact of phytochemicals on cancer immunotherapy.

Metabolism and pharmacokinetics of a novel polyphenol fatty acid ester phloridzin docosahexaenoate in Balb/c female mice

Flavonoids are known to undergo phase II metabolism and produce metabolites with similar or stronger biological effects compared to the parent flavonoids. However, the limited cellular uptake and bioavailability restrict their clinical use. We synthesized phloridzin docosahexaenoate (PZ-DHA), a novel fatty acid ester of polyphenol, through an acylation reaction with the aim of increasing the cellular availability and stability of the parent biomolecules, phloridzin (PZ) and docosahexaenoic acid (DHA). Here, we report metabolites and pharmacokinetic parameters of PZ-DHA, determined using ultra-high-performance liquid chromatography-electrospray ionization tandem mass spectrometry. PZ-DHA was taken-up by human (MDA-MB-231, MDA-MB-468, and MCF-7) and mouse (4T1) mammary carcinoma and human non-malignant mammary epithelial cells (MCF-10A) in cellular uptake assays. Our results suggested that the acylation improves the cellular uptake of PZ and stability of DHA within cells. In mouse hepatic microsomal assays, two major glucuronides of PZ-DHA, PZ-DHA-4-O-glucuronide and PZ-DHA-4'-O-glucuronide (MW = 923.02 g/mol), were detected. One tri-methylated- (4,4',6'-O-trimethyl-PZ-DHA) (MW = 788.88 g/mol) and one di-sulphated- (PZ-DHA-4,4'-O-disulphide) PZ-DHA metabolite (MW = 906.20 g/mol) were also identified. Intraperitoneal injections of PZ-DHA (100 mg/kg) into Balb/c female mice was rapidly absorbed with a serum C_max and T_max of 23.7 µM and 60 min, respectively, and rapidly eliminated (t_1/2 = 28.7 min). PZ-DHA and its metabolites are readily distributed throughout the body (V_d = 57 mL) into many organs. We identified in vitro and in vivo metabolites of PZ-DHA, which could be tested for potential use to treat diseases such as cancer in multiple organ systems.

Special Issue "Flavonoids and Their Disease Prevention and Treatment Potential": Recent Advances and Future Perspectives

In recent years, the interest in flavonoids as dietary bioactives to prevent human diseases, as well as their candidacy as pharmaceutical leads, has exponentially expanded [...].

Hydroxytyrosol and Oleuropein Inhibit Migration and Invasion of MDA-MB-231 Triple-Negative Breast Cancer Cell via Induction of Autophagy

BACKGROUND

Breast Cancer (BC) is the leading cause of cancer-related deaths among women. As such, novel chemotherapeutic agents are urgently needed, especially for Triple-Negative Breast Cancer (TNBC). Hydroxytyrosol (HT) and Oleuropein (OL) are rich in olive oil, which is associated with a low occurrence of BC. However, the effects and mechanisms of action of HT and OL in BC cells are still unclear. This study aimed to explore the molecular mechanisms underlying the antitumor effect of HT and OL in TNBC.

METHODS

TNBC MDA-MB-231 cells were treated with HT and OL in combination with Hepatocyte Growth Factor (HGF), rapamycin (Rapa, an inducer of autophagy) or 3-methyladenine (3-MA, an inhibitor of autophagy). Cell viability, migration, invasion, and autophagy signaling were analyzed by scratch assays, transwell migration assays, and Western blot analysis.

RESULTS

Treatment with HT or OL reduced MDA-MB-231 cell viability in a dose-dependent manner. MDAMB- 231 cells were more sensitive to HT treatment than OL treatment. Rapa treatment could significantly block HGF-induced MDA-MB-231 cell migration and invasion, suggesting that inhibition of autophagy could promote migration and invasion. Moreover, HT or OL treatment significantly suppressed HGF or 3-MA induced cell migration and invasion by reversing LC3-II/LC3-I and Beclin-1 downregulation and reversing p62 upregulation.

CONCLUSION

These data indicated that HT and OL may inhibit migration and invasion of TNBC cells by activating autophagy. These findings provide potential therapeutic strategies that target autophagy to limit the pathogenesis and progression of BC.

Phloridzin docosahexaenoate, a novel fatty acid ester of a plant polyphenol, inhibits mammary carcinoma cell metastasis

Triple-negative breast cancer (TNBC) tends to recur and metastasize following initial chemotherapy, which presents a treatment challenge. Here, we detail the anti-metastatic activity of phloridzin docosahexaenoate (PZ-DHA), synthesized from the natural polyphenol, phloridzin, and the ω-3 fatty acid, docosahexaenoic acid. Sub-cytotoxic PZ-DHA suppressed the migration of MDA-MB-231, SUM149, and 4T1 cells, as well as invasion by MDA-MB-231 and 4T1 cells. Sub-cytotoxic PZ-DHA also inhibited MDA-MB-231 expression of matrix metalloproteinase 2, and expression of epithelial-to-mesenchymal transition-associated transcription factors by MDA-MB-231 and SUM149 cells. Transforming growth factor-β-induced Rho GTPase signaling in MDA-MB-231 cells and non-malignant MCF-10A mammary epithelial cells was suppressed by sub-cytotoxic PZ-DHA, which also inhibited Akt/phosphoinositide 3-kinase and extracellular signal-regulated kinase 1 and 2 signaling in MDA-MB-231 cells. Finally, intraperitoneal administration of PZ-DHA suppressed the metastasis of 4T1 and GFP-transfected MDA-MB-231 cells from the mammary fat pad to the lungs of BALB/c and NOD-SCID female mice, respectively, which was unrelated to any inhibition of primary tumor growth. There was no evidence of toxicity as PZ-DHA treatment did not affect liver or kidney function. We conclude that PZ-DHA might prevent or inhibit the progression of TNBC.

Antioxidant capacity and hepatoprotective activity of myristic acid acylated derivative of phloridzin

The antioxidant activities in vitro and hepatoprotective effects against carbon tetrachloride (CCl₄) induced acute liver injury in vivo of myristic acid acylated derivative of phloridzin (PZM) were investigated. The PZM was obtained by enzymatic acylation of myristic acid and phloridzin (PZ). The antioxidant capability of PZM in vitro was evaluated by the ferric reducing antioxidant power assay (FRAP), 2,2'-Azinobis- 3-ethylbenzthiazoline-6-sulphonate (ABTS⁺·) and 2,2-diphenyl-1-picrylhydrazyl (DPPH·) radical scavenging assay. Mice were intragastrically treated with control or PZM (20, 40, and 80 mg/kg) for 5 days and intra-peritoneal injection with CCl₄. The enzymatic acylated synthesis of myristic acid and phloridzin was region-selective taken place on 6″-OH of phloridzin glycoside moiety and achieved 93% yield. PZM had a significantly higher total antioxidant ability, same scavenging ABTS⁺· ability and weaker scavenging DPPH· ability when compared to the parent PZ. The of aminotransferase serum activity and malondialdehyde hepatic activity were elevated (P < 0.015) after treatment with CCl₄, while the related liver enzymatic activities and glutathione concentration were lower. These changes were enhanced by PZM. Further studies showed that PZM reduced the interleukin-6 expression and stimulated liver regeneration caused by CCl₄. PZM attained good antioxidant capacity in vitro and had excellent hepatoprotective effects in vivo and better bioactivity compared to the parent phloridzin. The significance of hepatoprotective effect of phloridzin derivative against CCl₄-induced hepatotoxicity in mice is an important and new finding.

Novel Docosahexaenoic Acid Ester of Phloridzin Inhibits Proliferation and Triggers Apoptosis in an In Vitro Model of Skin Cancer

Skin cancer is among the most common cancer types accompanied by rapidly increasing incidence rates, thus making the development of more efficient therapeutic approaches a necessity. Recent studies have revealed the potential role of decosahexaenoic acid ester of phloridzin (PZDHA) in suppressing proliferation of liver, breast, and blood cancer cell lines. In the present study, we investigated the cytotoxic potential of PZDHA in an in vitro model of skin cancer consisting of melanoma (A375), epidermoid carcinoma (A431), and non-tumorigenic (HaCaT) cell lines. Decosahexaenoic acid ester of phloridzin led to increased cytotoxicity in all cell lines as revealed by cell viability assays. However, growth inhibition and induction of both apoptosis and necrosis was more evident in melanoma (A375) and epidermoid carcinoma (A431) cells, whereas non-tumorigenic keratinocytes (HaCaT) appeared to be more resistant as detected by flow cytometry. More specifically, PZDHA-induced cell cycle growth arrest at the G2/M phase in A375 and A431 cells in contrast to HaCaT cells, which were growth arrested at the G0/G1 phase. Elevated intracellular generation of reactive oxygen species ROS was detected in all cell lines. Overall, our findings support the potential of PZDHA as a novel therapeutic means against human skin cancer.

Improvement of the Color Stability of Cyanidin-3-glucoside by Fatty Acid Enzymatic Acylation

Anthocyanins are water-soluble pigments with limited application in lipophilic matrices such as lipid-based foods and cosmetic formulations. In this work, the liposolubility improvement of cyanidin-3-glucoside (cy3glc) was performed by enzymatic esterification with saturated fatty acids with variable chain lengths, and their thermostabilities were evaluated at different pH values in a lipophilic medium (an aqueous sodium dodecyl sulfate solution) by means of UV-vis spectroscopy. Overall, lipophilic cy3glc derivatives showed improved color stability and lowered sensitivity to thermal degradation than nonmodified cy3glc in an SDS micellar solution between pH 3 and 7.

Polyphenolic Phytochemicals in Cancer Prevention and Therapy: Bioavailability versus Bioefficacy

Natural polyphenols are organic chemicals which contain phenol units in their structures. They show antitumor properties. However, a key problem is their short half-life and low bioavailability under in vivo conditions. Still, definitively demonstrating the human benefits of isolated polyphenolic compounds (alone or in combination) using modern scientific methodology has proved challenging. The most common discrepancy between experimental and clinical observations is the use of nonphysiologically relevant concentrations of polyphenols in mechanistic studies. Thus, it remains highly controversial how applicable underlying mechanisms are with bioavailable concentrations and biological half-life. The present Perspective analyses proposed antitumor mechanisms, in vivo reported antitumor effects, and possible mechanisms that may explain discrepancies between bioavailability and bioefficacy. Polyphenol metabolism and possible toxic side effects are also considered. Our main conclusion emphasizes that these natural molecules (and their chemical derivatives) indeed can be very useful, not only as cancer chemopreventive agents but also in oncotherapy.