Phloridzin Docosahexaenoate, an Omega-3 Fatty Acid Ester of a Flavonoid Precursor, Inhibits Angiogenesis by Suppressing Endothelial Cell Proliferation, Migration, and Differentiation.

Angiogenesis is a normal physiological process that also contributes to diabetic retinopathy-related complications and facilitates tumor metastasis by promoting the hematogenic dissemination of malignant cells from solid tumors. Here, we investigated the in vitro, ex vivo, and in vivo anti-angiogenic activity of phloridzin docosahexaenoate (PZ-DHA), a novel ω-3 fatty acid ester of a flavonoid precursor. Human umbilical vein endothelial cells (HUVEC) and human dermal microvascular endothelial cells (HMVEC) treated with a sub-cytotoxic concentration of PZ-DHA to assess in vitro anti-angiogenic activity showed impaired tubule formation on a Matrigel matrix. Ex vivo angiogenesis was measured using rat thoracic aortas, which exhibited reduced vessel sprouting and tubule formation in the presence of PZ-DHA. Female BALB/c mice bearing VEGF165- and basic fibroblast growth factor-containing Matrigel plugs showed a significant reduction in blood vessel development following PZ-DHA treatment. PZ-DHA inhibited HUVEC and HMVEC proliferation, as well as the migration of HUVECs in gap closure and trans-well cell migration assays. PZ-DHA inhibited upstream and downstream components of the Akt pathway and vascular endothelial growth factor (VEGF165)-induced overexpression of small molecular Rho GTPases in HUVECs, suggesting a decrease in actin cytoskeletal-mediated stress fiber formation and migration. Taken together, these findings reveal the potential of combined food biomolecules in PZ-DHA to inhibit angiogenesis.

Informed by Cancer Stem Cells of Solid Tumors: Advances in Treatments Targeting Tumor-Promoting Factors and Pathways.

Cancer stem cells (CSCs) represent a subpopulation within tumors that promote cancer progression, metastasis, and recurrence due to their self-renewal capacity and resistance to conventional therapies. CSC-specific markers and signaling pathways highly active in CSCs have emerged as a promising strategy for improving patient outcomes. This review provides a comprehensive overview of the therapeutic targets associated with CSCs of solid tumors across various cancer types, including key molecular markers aldehyde dehydrogenases, CD44, epithelial cellular adhesion molecule, and CD133 and signaling pathways such as Wnt/ß-catenin, Notch, and Sonic Hedgehog. We discuss a wide array of therapeutic modalities ranging from targeted antibodies, small molecule inhibitors, and near-infrared photoimmunotherapy to advanced genetic approaches like RNA interference, CRISPR/Cas9 technology, aptamers, antisense oligonucleotides, chimeric antigen receptor (CAR) T cells, CAR natural killer cells, bispecific T cell engagers, immunotoxins, drug-antibody conjugates, therapeutic peptides, and dendritic cell vaccines. This review spans developments from preclinical investigations to ongoing clinical trials, highlighting the innovative targeting strategies that have been informed by CSC-associated pathways and molecules to overcome therapeutic resistance. We aim to provide insights into the potential of these therapies to revolutionize cancer treatment, underscoring the critical need for a multi-faceted approach in the battle against cancer. This comprehensive analysis demonstrates how advances made in the CSC field have informed significant developments in novel targeted therapeutic approaches, with the ultimate goal of achieving more effective and durable responses in cancer patients.

ALDH1A3 promotes invasion and metastasis in triple-negative breast cancer by regulating the plasminogen activation pathway.

Aldehyde dehydrogenase 1A3 (ALDH1A3) is a cancer stem cell marker that promotes metastasis. Triple-negative breast cancer (TNBC) progression has been linked to ALDH1A3-induced gene expression changes. To investigate the mechanism of ALDH1A3-mediated breast cancer metastasis, we assessed the effect of ALDH1A3 on the expression of proteases and the regulators of proteases that degrade the extracellular matrix, a process that is essential for invasion and metastasis. This revealed that ALDH1A3 regulates the plasminogen activation pathway; it increased the levels and activity of tissue plasminogen activator (tPA) and urokinase plasminogen activator (uPA). This resulted in a corresponding increase in the activity of serine protease plasmin, the enzymatic product of tPA and uPA. The ALDH1A3 product all-trans-retinoic acid similarly increased tPA and plasmin activity. The increased invasion of TNBC cells by ALDH1A3 was plasminogen-dependent. In patient tumours, ALDH1A3 and tPA are co-expressed and their combined expression correlated with the TNBC subtype, high tumour grade and recurrent metastatic disease. Knockdown of tPA in TNBC cells inhibited plasmin generation and lymph node metastasis. These results identify the ALDH1A3-tPA-plasmin axis as a key contributor to breast cancer progression.

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.

Iron Withdrawal with DIBI, a Novel 3-Hydroxypyridin-4-One Chelator Iron-Binding Polymer, Attenuates Macrophage Inflammatory Responses.

Purpose: Iron is an essential trace element for the inflammatory response to infection. In this study, we determined the effect of the recently developed iron-binding polymer DIBI on the synthesis of inflammatory mediators by RAW 264.7 macrophages and bone marrow-derived macrophages (BMDMs) in response to lipopolysaccharide (LPS) stimulation. Methods: Flow cytometry was used to determine the intracellular labile iron pool, reactive oxygen species production, and cell viability. Cytokine production was measured by quantitative reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay. Nitric oxide synthesis was determined by the Griess assay. Western blotting was used to assess signal transducer and activator of transcription (STAT) phosphorylation. Results: Macrophages cultured in the presence of DIBI exhibited a rapid and significant reduction in their intracellular labile iron pool. DIBI-treated macrophages showed reduced expression of proinflammatory cytokines interferon-ß, interleukin (IL)-1ß, and IL-6 in response to LPS. In contrast, exposure to DIBI did not affect LPS-induced expression of tumor necrosis factor-α (TNF-α). The inhibitory effect of DIBI on IL-6 synthesis by LPS-stimulated macrophages was lost when exogenous iron in the form of ferric citrate was added to culture, confirming the selectivity of DIBI for iron. DIBI-treated macrophages showed reduced production of reactive oxygen species and nitric oxide following LPS stimulation. DIBI-treated macrophages also showed a reduction in cytokine-induced activation of STAT 1 and 3, which potentiate LPS-induced inflammatory responses. Conclusion: DIBI-mediated iron withdrawal may be able to blunt the excessive inflammatory response by macrophages in conditions such as systemic inflammatory syndrome.

The Expanding Role of Cancer Stem Cell Marker ALDH1A3 in Cancer and Beyond.

Aldehyde dehydrogenase 1A3 (ALDH1A3) is one of 19 ALDH enzymes expressed in humans, and it is critical in the production of hormone receptor ligand retinoic acid (RA). We review the role of ALDH1A3 in normal physiology, its identification as a cancer stem cell marker, and its modes of action in cancer and other diseases. ALDH1A3 is often over-expressed in cancer and promotes tumor growth, metastasis, and chemoresistance by altering gene expression, cell signaling pathways, and glycometabolism. The increased levels of ALDH1A3 in cancer occur due to genetic amplification, epigenetic modifications, post-transcriptional regulation, and post-translational modification. Finally, we review the potential of targeting ALDH1A3, with both general ALDH inhibitors and small molecules specifically designed to inhibit ALDH1A3 activity.

Isolation of cancer stem cells from cultured breast cancer cells and xenografted breast tumors based on aldehyde dehydrogenase activity.

The heterogeneity of breast tumors is a major factor in the development, progression, and therapeutic response of breast cancer. In terms of therapy resistance, a subset of tumor cells commonly referred to as cancer stem cells (CSCs) or tumor initiating cells (TICs) have a prominent role. These cells have inherent increased tumorigenicity, self-renewal and differentiation capacity, and mechanisms for chemotherapy and radiation resistance. The importance of CSCs/TICs in cancer makes isolating and studying these cells via reliable methods critical. CSCs/TICs can be enriched for by discrete markers. Increased aldehyde dehydrogenase (ALDH) activity as detected by the AldefluorTM assay is a commonly used method. In this chapter, we describe the detailed methods for identification and isolation of putative CSCs/TICs from cultured cells and xenografted breast tumors using the AldefluorTM assay and describe the importance of the ALDH isoforms in breast cancer.

Breast Cancer Xenograft Murine Models.

Mice are used as model organisms to understand the pathological basis of a variety of human diseases, including breast cancer. Both immunocompetent and immunocompromised mouse models are used depending on the scope of the study. Immunocompetent models allow the study of the impact of the immune system in murine models of mammary cancer, while immunodeficient mice serve as ideal host organisms to understand the behavior of human breast cancers within a biological system. Xenografting of human breast cancer cells into immunocompromised mouse models continues to be the most used fundamental animal model in preclinical breast cancer research. These in vivo models allow critical understanding of tumor biology and assessment of novel treatments, a necessary prelude to testing new drugs in the clinic. In this chapter, we provide detailed methodology for the use of non-obese diabetic (NOD) severe combined immunodeficient (SCID) mice in several breast cancer xenografting procedures, including established cell lines and patient-derived xenografts (PDXs).

Metabolite profiling reveals a connection between aldehyde dehydrogenase 1A3 and GABA metabolism in breast cancer metastasis.

INTRODUCTION: Aldehyde dehydrogenase 1A3 (ALDH1A3) is a cancer stem cell (CSC) marker and in breast cancer it is associated with triple-negative/basal-like subtypes and aggressive disease. Studies on the mechanisms of ALDH1A3 in cancer have primarily focused on gene expression changes induced by the enzyme; however, its effects on metabolism have thus far been unstudied and may reveal novel mechanisms of pathogenesis. OBJECTIVE: Determine how ALDH1A3 alters the metabolite profile in breast cancer cells and assess potential impacts. METHOD: Triple-negative MDA-MB-231 tumors and cells with manipulated ALDH1A3 levels were assessed by HPLC-MS metabolomics and metabolite data was integrated with transcriptome data. Mice harboring MDA-MB-231 tumors with or without altered ALDH1A3 expression were treated with γ-aminobutyric acid (GABA) or placebo. Effects on tumor growth, and lungs and brain metastasis were quantified by staining of fixed thin sections and quantitative PCR. Breast cancer patient datasets from TCGA, METABRIC and GEO were used to assess the co-expression of GABA pathway genes with ALDH1A3. RESULTS: Integrated metabolomic and transcriptome data identified GABA metabolism as a primary dysregulated pathway in ALDH1A3 expressing breast tumors. Both ALDH1A3 and GABA treatment enhanced metastasis. Patient dataset analyses revealed expression association between ALDH1A3 and GABA pathway genes and corresponding increased risk of metastasis. CONCLUSION: This study revealed a novel pathway affected by ALDH1A3, GABA metabolism. Like ALDH1A3 expression, GABA treatment promotes metastasis. Given the clinical use of GABA mimics to relieve chemotherapy-induced peripheral nerve pain, further study of the effects of GABA in breast cancer progression is warranted.

Datasets exploring putative lncRNA-miRNA-mRNA axes in breast cancer cell lines.

Long non-coding RNA (lncRNA)/microRNA (miRNA)/messenger RNA (mRNA) interactions regulate oncogenesis and tumour suppression in breast cancer. Oncogenic lncRNA/miRNA/mRNA axes may offer novel therapeutic targets; therefore, identifying such axes is a clinically relevant undertaking. To explore miRNAs regulated by oncogenic lncRNAs, we queried the NCBI Gene Expression Omnibus (GEO) database to find datasets that profiled gene expression changes upon lncRNA knockdown in breast cancer. We identified four microarray datasets that permitted our interrogation of genes regulated by lncRNAs LincK, LincIN, SPRY4-IT1 and AC009283.1. We specifically analysed changes in miRNA transcripts within these datasets to study miRNAs regulated by each of the four lncRNAs. We subsequently identified the predicted mRNA targets for these miRNAs to uncover possible lncRNA/miRNA/mRNAs axes in breast cancer. These axes may be candidates for future investigation of gene regulation in breast cancer.

LncRNA PART1 Promotes Proliferation and Migration, Is Associated with Cancer Stem Cells, and Alters the miRNA Landscape in Triple-Negative Breast Cancer.

Triple-negative breast cancers (TNBCs) are aggressive, lack targeted therapies and are enriched in cancer stem cells (CSCs). Novel therapies which target CSCs within these tumors would likely lead to improved outcomes for TNBC patients. Long non-coding RNAs (lncRNAs) are potential therapeutic targets for TNBC and CSCs. We demonstrate that lncRNA prostate androgen regulated transcript 1 (PART1) is enriched in TNBCs and in Aldefluorhigh CSCs, and is associated with worse outcomes among basal-like breast cancer patients. Although PART1 is androgen inducible in breast cancer cells, analysis of patient tumors indicates its androgen regulation has minimal clinical impact. Knockdown of PART1 in TNBC cell lines and a patient-derived xenograft decreased cell proliferation, migration, tumor growth, and mammosphere formation potential. Transcriptome analyses revealed that the lncRNA affects expression of hundreds of genes (e.g., myosin-Va, MYO5A; zinc fingers and homeoboxes protein 2, ZHX2). MiRNA 4.0 GeneChip and TaqMan assays identified multiple miRNAs that are regulated by cytoplasmic PART1, including miR-190a-3p, miR-937-5p, miR-22-5p, miR-30b-3p, and miR-6870-5p. We confirmed the novel interaction between PART1 and miR-937-5p. In general, miRNAs altered by PART1 were less abundant than PART1, potentially leading to cell line-specific effects in terms miRNA-PART1 interactions and gene regulation. Together, the altered miRNA landscape induced by PART1 explains most of the protein-coding gene regulation changes (e.g., MYO5A) induced by PART1 in TNBC.

An in vivo genome-wide shRNA screen identifies BCL6 as a targetable biomarker of paclitaxel resistance in breast cancer.

Paclitaxel is a common breast cancer drug; however, some tumors are resistant. The identification of biomarkers for paclitaxel resistance or sensitivity would enable the development of strategies to improve treatment efficacy. A genome-wide in vivo shRNA screen was performed on paclitaxel-treated mice with MDA-MB-231 tumors to identify genes associated with paclitaxel sensitivity or resistance. Gene expression of the top screen hits was associated with tumor response (resistance or sensitivity) among patients who received neoadjuvant chemotherapy containing paclitaxel. We focused our validation on screen hit B-cell lymphoma 6 (BCL6), which is a therapeutic target in cancer but for which no effects on drug response have been reported. Knockdown of BCL6 resulted in increased tumor regression in mice treated with paclitaxel. Similarly, inhibiting BCL6 using a small molecule inhibitor enhanced paclitaxel treatment efficacy both in vitro and in vivo in breast cancer models. Mechanism studies revealed that reduced BCL6 enhances the efficacy of paclitaxel by inducing sustained G1/S arrest, concurrent with increased apoptosis and expression of target gene cyclin-dependent kinase inhibitor 1A. In summary, the genome-wide shRNA knockdown screen has identified BCL6 as a potential targetable resistance biomarker of paclitaxel response in breast cancer.

LncRNA-miRNA axes in breast cancer: Novel points of interaction for strategic attack.

Therapeutic effectiveness in breast cancer can be limited by the underlying mechanisms of pathogenesis, including epithelial-mesenchymal transition (EMT), cancer stem cells (CSCs) and drug resistance. Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) are master regulators of gene expression and are functionally important mediators in these mechanisms of pathogenesis. Intricate crosstalks between these non-coding RNAs form complex regulatory networks of post-transcriptional gene regulation. Depending on the specific lncRNA/miRNA interaction, the lncRNA-miRNA axis can have tumor suppressor or oncogenic effects, thus defining the lncRNA-miRNA axis is important for determining targetability. Herein, we summarize the current literature describing lncRNA-miRNA interactions that are critical in the molecular mechanisms that regulate EMT, CSCs and drug resistance in breast cancer. Further, we review both the well-studied and potential novel mechanisms of lncRNA-miRNA interactions in breast cancer.

Dual Antimicrobial and Antiproliferative Activity of TcPaSK Peptide Derived from a Tribolium castaneum Insect Defensin.

Antimicrobial peptides (AMPs) found in the innate immune system of a wide range of organisms might prove useful to fight infections, due to the reported slower development of resistance to AMPs. Increasing the cationicity and keeping moderate hydrophobicity of the AMPs have been described to improve antimicrobial activity. We previously found a peptide derived from the Tribolium castaneum insect defensin 3, exhibiting antrimicrobial activity against several human pathogens. Here, we analyzed the effect against Staphyloccocus aureus of an extended peptide (TcPaSK) containing two additional amino acids, lysine and asparagine, flanking the former peptide fragment in the original insect defensin 3 protein. TcPaSK peptide displayed higher antimicrobial activity against S. aureus, and additionally showed antiproliferative activity against the MDA-MB-231 triple negative breast cancer cell line. A SWATH proteomic analysis revealed the downregulation of proteins involved in cell growth and tumor progression upon TcPaSK cell treatment. The dual role of TcPaSK peptide as antimicrobial and antiproliferative agent makes it a versatile molecule that warrants exploration for its use in novel therapeutic developments as an alternative approach to overcome bacterial antibiotic resistance and to increase the efficacy of conventional cancer treatments.

The Natural Alkaloid Piperlongumine Inhibits Metastatic Activity and Epithelial-to-Mesenchymal Transition of Triple-Negative Mammary Carcinoma Cells.

In this study, we determined the effect of low dose piperlongumine on the motility/invasive capacity and epithelial-to-mesenchymal transition (EMT) of MDA-MB-231 triple-negative breast cancer (TNBC) cells and the metastasis of 4T1 mouse mammary carcinoma cells. MTT assays measured the effect of piperlongumine on TNBC cell growth. Motility/invasiveness were determined by gap closure/transwell assays. Western blotting assessed ZEB1, Slug, and matrix metalloproteinase (MMP) 9 expression. Interleukin (IL) 6 was detected by ELISA. MMP2, E-cadherin, and miR-200c expression was determined by real-time quantitative polymerase chain reaction. Reactive oxygen species (ROS) were measured by flow cytometry. The orthotopic 4T1 mouse model of breast cancer was used to examine metastasis. Piperlongumine-treated MDA-MB-231 cells showed reduced motility/invasiveness, decreased MMP2 and MMP9 expression, increased miR-200c expression, reduced IL-6 synthesis, decreased expression of ZEB1 and Slug, increased E-cadherin expression, and epithelial-like morphology. Piperlongumine also inhibited transforming growth factor ß-induced ZEB1 and Slug expression. ROS accumulated in piperlongumine-treated cells, while changes in metastasis-associated gene expression were ablated by exogenous glutathione. Metastasis of 4T1 cells to the lungs of BALB/c mice was dramatically reduced in piperlongumine-treated animals. These findings reveal a previously unknown capacity of low dose piperlongumine to interfere with TNBC metastasis via an oxidative stress-dependent mechanism.

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 Cmax and Tmax of 23.7 µM and 60 min, respectively, and rapidly eliminated (t1/2 = 28.7 min). PZ-DHA and its metabolites are readily distributed throughout the body (Vd = 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.

DIBI, a novel 3-hydroxypyridin-4-one chelator iron-binding polymer, inhibits breast cancer cell growth and functions as a chemosensitizer by promoting S-phase DNA damage.

Breast cancer is a leading cause of cancer-related death in women; however, chemotherapy of breast cancer is often hindered by dose-limiting toxicities, demonstrating the need for less toxic approaches to treatment. Since the rapid growth and metabolism of breast cancer cells results in an increased requirement for iron, withdrawal of bioavailable iron using highly selective iron chelators has been suggested to represent a new approach to breast cancer treatment. Here we show that the recently developed iron-binding polymer DIBI inhibited the growth of five different breast cancer cell lines (SK-BR3, MDA-MB-468, MDA-MB-231, MCF-7, and T47D). In cultures of MDA-MB-468 breast cancer cells, which were most sensitive to DIBI-mediated growth inhibition, iron withdrawal was associated with increased expression of transferrin receptor 1 and ferritin H mRNA but decreased expression of ferroportin mRNA. MDA-MB-468 cells that were exposed to DIBI experienced double-strand DNA breaks during the S phase of the cell cycle. DNA damage was not mediated by reactive oxygen species (ROS) since DIBI-treated MDA-MB-468 cells exhibited a reduction in intracellular ROS. DIBI-treated MDA-MB-468 cells also showed increased sensitivity to growth inhibition by the chemotherapeutic drugs cisplatin, doxorubicin, and 4-hydroperoxy cyclophosphamide (active metabolite of cyclophosphamide). Combination treatment of MDA-MB-468 cells with DIBI and cisplatin caused greater DNA damage than either treatment alone, which was also associated with an increase in apoptotic cell death. Taken together, these findings suggest that DIBI-mediated iron withdrawal may enhance the effect of chemotherapeutic agents used in breast cancer treatment.

Apple Peel Flavonoid Fraction 4 Suppresses Breast Cancer Cell Growth by Cytostatic and Cytotoxic Mechanisms.

Many dietary flavonoids possess anti-cancer activities. Here, the effect of apple peel flavonoid fraction 4 (AF4) on the growth of triple-negative (MDA-MB-231, MDA-MB-468), estrogen receptor-positive (MCF-7), and HER2-positive (SKBR3) breast cancer cells was determined and compared with the effect of AF4 on normal mammary epithelial cells and dermal fibroblasts. AF4 inhibited breast cancer cell growth in monolayer cultures, as well as the growth of MCF-7 spheroids, without substantially affecting the viability of non-malignant cells. A sub-cytotoxic concentration of AF4 suppressed the proliferation of MDA-MB-231 cells by inhibiting passage through the G0/G1 phase of the cell cycle. AF4-treated MDA-MB-231 cells also exhibited reduced in vitro migration and invasion, and decreased Akt (protein kinase B) signaling. Higher concentrations of AF4 were selectively cytotoxic for MDA-MB-231 cells. AF4 cytotoxicity was associated with the intracellular accumulation of reactive oxygen species. Importantly, intratumoral administration of AF4 suppressed the growth of MDA-MB-231 xenografts in non-obese diabetic severe combined immunodeficient (NOD-SCID) female mice. The selective cytotoxicity of AF4 for breast cancer cells, combined with the capacity of sub-cytotoxic AF4 to inhibit breast cancer cell proliferation, migration, and invasion suggests that flavonoid-rich AF4 (and its constituents) has potential as a natural therapeutic agent for breast cancer treatment.

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-ß-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.

Dietary phytochemicals with anti-oxidant and pro-oxidant activities: A double-edged sword in relation to adjuvant chemotherapy and radiotherapy?

Many advances have been made in the development and introduction of new anti-cancer drugs to the clinic. However, limited attention has been paid to improving the efficacy of currently available treatments through complementary phytochemical interventions that affect cellular reactive oxygen species (ROS) levels, which are important for the etiology of certain cancers and the effectiveness of radiotherapy and some chemotherapy. In this regard, the maintenance of redox homeostasis may be influenced by the intake of anti-oxidant and pro-oxidant compounds from dietary sources. Interestingly, certain dietary phytochemicals exhibit both anti-oxidant and pro-oxidant activities, depending on their concentration and cellular microenvironment. There is evidence that concurrent administration of some dietary phytochemicals enhances the efficacy of certain cancer treatments by increasing intracellular ROS accumulation. Paradoxically, consumption of the same dietary phytochemicals under conditions that result in the scavenging of ROS might also negatively affect the outcome of ROS-dependent cancer treatments. This review discusses the potential impact of consuming dietary phytochemicals with anti-oxidant and/or pro-oxidant activities on the effectiveness of concurrent chemotherapy and/or radiotherapy in cancer patients.