Rosmarinic acid (RA) is a polyphenolic compound with various pharmacological properties, including, anti-inflammatory, immunomodulatory, and neuroprotective, as well as having antioxidant and anticancer activities. This study evaluated the effects and mechanisms of RA in two racially different triple-negative breast cancer (TNBC) cell lines. Results obtained show that RA significantly caused cytotoxic and antiproliferative effects in both cell lines in a dose- and time-dependent manner. Remarkably, RA induced cell cycle arrest-related apoptosis and altered the expression of many apoptosis-involved genes differently. In MDA-MB-231 cells, RA arrested the cells in the G 0 /G 1 phase. In contrast, the data suggest that RA causes S-phase arrest in MDA-MB-468 cells, leading to a 2-fold increase in the apoptotic effect compared to MDA-MB-231 cells. Further, in MDA-MB-231 cells, RA significantly upregulated the mRNA expression of three genes: harakiri ( HRK ), tumor necrosis factor receptor superfamily 25 ( TNFRSF25 ), and BCL-2 interacting protein 3 ( BNIP3 ). In contrast, in the MDA-MB-468 cell line, the compound induced a significant transcription activation in three genes, including TNF , growth arrest and DNA damage-inducible 45 alpha ( GADD45A ), and BNIP3 . Furthermore, RA repressed the expression of TNF receptor superfamily 11B ( TNFRSF11B ) in MDA-MB-231 cells in comparison to the ligand TNF superfamily member 10 ( TNFSF10) and baculoviral IAP repeat-containing 5 (BIRC5) in MDA-MB-468 cells. In conclusion, the data suggest that the polyphenol RA may have a potential role in TNBC therapies, particularly in MDA-MB-468 cells.

Apoptosis is a gene‐directed mechanism that regulates cell proliferation and maintains homeostasis. However, the uncontrolled apoptotic process can lead to several pathological conditions such as tumorigenesis, and cancer metastasis. In the current study, the apoptotic effect of the natural polyphenol compound gossypol (GOSS) was investigated in the triple negative breast cancer (TNBC) cells. The effect of GOSS was evaluated in two cell lines representing Caucasian Americans and African Americans: MDA‐MB‐231 (MM‐231) and MDA‐MB‐468 (MM‐468), respectively. In both cell lines, a similar response was noticed in both cytotoxicity and proliferation studies. However, MM‐468 cells were 3‐fold more sensitive to the apoptotic effect of the compound that was accompanied by a longer delay in the colony formation. Furthermore, GOSS was found to alter the expression of many apoptosis‐related genes in our mRNA expression investigation. The compound significantly upregulated GADD45A, TNFRSF9, and BNIP3 in MM‐231 cells. Similarly, GADD45A and BNIP3 were upregulated in MM‐468. A significant finding observed in this study is the profound 159‐fold increase in the TNF gene expression that was found in MM‐468 cells. Moreover, the apoptosis‐suppressor gene, BIRC5 was significantly repressed by more than 90% in both cell lines as well as DAPK1 in MM‐231 and TP73 in MM‐468 cells. In conclusion, the data obtained in this study can provide a more understanding of the GOSS‐induced apoptosis effect and enhance the importance of this polyphenol compound as targeted towards BC treatment, particularly in African American women. Support or Funding Information This research was supported by NIH NIMHD Grants G12 MD007582 and P20 MD 006738 This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Monoamine oxidases inhibitors (MAOIs) are effective therapeutic drugs for managing Parkinson's disease (PD) and depression. However, their irreversibility may lead to rare but serious side effects. As finding safer and reversible MAOIs is our target, we characterized the recombinant human (h) MAO-A and MAO-B inhibition potentials of two common natural isoflavones, genistein (GST) and daidzein (DZ) using luminescence assay. The results obtained showed that DZ exhibits partial to no inhibition of the isozymes examined while GST inhibited hMAO-B (IC50 of 6.81 μM), and its hMAO-A inhibition was more potent than the standard deprenyl. Furthermore, the reversibility, mode of inhibition kinetics, and tyramine oxidation of GST were examined. GST was a time-independent reversible and competitive hMAO-A and hMAO-B inhibitor with a lower K i of hMAO-B (1.45 μM) than hMAO-A (4.31 μM). GST also inhibited hMAO-B tyramine oxidation and hydrogen peroxide production more than hMAO-A. Docking studies conducted indicated that the GST reversibility and hMAO-B selectivity of inhibition may relate to C5-OH effects on its orientation and its interactions with the threonine 201 residue of the active site. It was concluded from this study that the natural product GST has competitive and reversible MAOs inhibitions and may be recommended for further investigations as a useful therapeutic agent for Parkinson's disease.

BackgroundMonoamine oxidase-B (MAO-B) inhibitors are widely used in the treatment of Parkinson’s disease. They increase vital monoamine neurotransmitters in the brain. However, there is a need for safer natural reversible MAO inhibitors with MAO-B selectivity. Our previous studies showed that Psoralea corylifolia seeds (PCS) extract contains compounds that inhibit monoamine oxidase-B.MethodsIn this study, six of PCS constituents sharing a benzopyrone structure were investigated. The compounds Biochanin-A (BIO-A), isopsoralen, 6-prenylnaringenin, neobavaisoflavone, psoralen, and psoralidin, were tested for their ability to inhibit recombinant human MAO-A and B (hMAO-A and hMAO-B) isozymes. The ability of these compounds to inhibit MAO-A and MAO-B were compared to that of PCS ethanolic extract (PCSEE) using spectrophotometric assays and confirmed by luminescence assays. The highly potent and selective MAO-B inhibitor, BIO-A, was further investigated for both isozymes reversibility and enzyme kinetics. Molecular docking studies were used to predict the bioactive conformation and molecular interactions of BIO-A with both isozymes.ResultsThe data obtained indicate that benzopyrones inhibited hMAO-A and hMAO-B with different degrees as confirmed with the luminescence assay. BIO-A inhibited hMAO-B with high potency and selectivity in the present study (IC50 = 0.003 μg/mL) and showing 38-fold more selectivity than PCSEE (hMAO-B IC50 = 3.03 μg/mL, 17-fold selectivity) without affecting hydrogen peroxide. Furthermore, BIO-A reversibly and competitively inhibited both hMAOs with significantly lower inhibitory constant (Ki) in hMAO-B (3.8 nM) than hMAO-A (99.3 nM). Our docking studies indicated that the H-bonds and hydrophobic interactions at the human MAO-A and MAO-B active sites contributed to the reversibility and selectivity of BIO-A.ConclusionsThe data obtained indicate that BIO-A is a potent, reversible and selective MAO-B inhibitor and may be recommended for further investigation in its possible use in the therapeutic management of Parkinson’s and Alzheimer’s diseases.

Investigating dietary polyphenolic compounds as antitumor agents are rising due to the growing evidence of the close association between immunity and cancer. Cancer cells elude immune surveillance for enhancing their progression and metastasis utilizing various mechanisms. These mechanisms include the upregulation of programmed death-ligand 1 (PD-L1) expression and Epithelial-to-Mesenchymal Transition (EMT) cell phenotype activation. In addition to its role in stimulating normal embryonic development, EMT has been identified as a critical driver in various aspects of cancer pathology, including carcinogenesis, metastasis, and drug resistance. Furthermore, EMT conversion to another phenotype, Mesenchymal-to-Epithelial Transition (MET), is crucial in developing cancer metastasis. A central mechanism in the upregulation of PD-L1 expression in various cancer types is EMT signaling activation. In breast cancer (BC) cells, the upregulated level of PD-L1 has become a critical target in cancer therapy. Various signal transduction pathways are involved in EMT-mediated PD-L1 checkpoint overexpression. Three main groups are considered potential targets in EMT development; the effectors (E-cadherin and Vimentin), the regulators (Zeb, Twist, and Snail), and the inducers that include members of the transforming growth factor-beta (TGF-β). Meanwhile, the correlation between consuming flavonoid-rich food and the lower risk of cancers has been demonstrated. In BC, polyphenols were found to downregulate PD-L1 expression. This review highlights the effects of polyphenols on the EMT process by inhibiting mesenchymal proteins and upregulating the epithelial phenotype. This multifunctional mechanism could hold promises in the prevention and treating breast cancer.