Involvement of AKT/PI3K Pathway in Sanguinarine's Induced Apoptosis and Cell Cycle Arrest in Triple-negative Breast Cancer Cells

BACKGROUND/AIM

Chemotherapy resistance in triple-negative breast cancer (TNBC) cells is well documented. Therefore, it is necessary to develop safer and more effective therapeutic agents to enhance the outcomes of chemotherapeutic agents. The natural alkaloid sanguinarine (SANG) has demonstrated therapeutic synergy when coupled with chemotherapeutic agents. SANG can also induce cell cycle arrest and trigger apoptosis in various cancer cells.

MATERIALS AND METHODS

In this study, we investigated the molecular mechanism underlying SANG activity in MDA-MB-231 and MDA-MB-468 cells as two genetically different models of TNBC. We employed various assays including Alamar Blue to measure the effect of SANG on cell viability and proliferation rate, flow cytometry analysis to study the potential of the compound to induce apoptosis and cell cycle arrest, quantitative qRT PCR apoptosis array to measure the expression of different genes mediating apoptosis, and the western system was used to analyze the impact of the compound on AKT protein expression.

RESULTS

SANG lowered cell viability and disrupted cell cycle progression in both cell lines. Furthermore, S-phase cell cycle arrest-mediated apoptosis was found to be the primary contributor to cell growth inhibition in MDA-MB-231 cells. SANG-treated TNBC cells showed significantly up-regulated mRNA expression of 18 genes associated with apoptosis, including eight TNF receptor superfamily (TNFRSF), three members of the BCL2 family, and two members of the caspase (CASP) family in MDA-MB-468 cells. In MDA-MB-231 cells, two members of the TNF superfamily and four members of the BCL2 family were affected. The western study data showed the inhibition of AKT protein expression in both cell lines concurrent with up-regulated BCL2L11 gene. Our results point to the AKT/PI3K signaling pathway as one of the key mechanisms behind SANG-induced cell cycle arrest and death.

CONCLUSION

SANG shows anticancer properties and apoptosis-related gene expression changes in the two TNBC cell lines and suggests AKT/PI3K pathway implication in apoptosis induction and cell cycle arrest. Thus, we propose SANG's potential as a solitary or supplementary treatment agent against TNBC.

Sanguinarine Inhibition of TNF-α-Induced CCL2, IKBKE/NF-κB/ERK1/2 Signaling Pathway, and Cell Migration in Human Triple-Negative Breast Cancer Cells

Angiogenesis is a process that drives breast cancer (BC) progression and metastasis, which is linked to the altered inflammatory process, particularly in triple-negative breast cancer (TNBC). In targeting inflammatory angiogenesis, natural compounds are a promising option for managing BC. Thus, this study was designed to determine the natural alkaloid sanguinarine (SANG) potential for its antiangiogenic and antimetastatic properties in triple-negative breast cancer (TNBC) cells. The cytotoxic effect of SANG was examined in MDA-MB-231 and MDA-MB-468 cell models at a low molecular level. In this study, SANG remarkably inhibited the inflammatory mediator chemokine CCL2 in MDA-MB-231 and MDA-MB-468 cells. Furthermore, qRT-PCR confirmed with Western analysis studies showed that mRNA CCL2 repression was concurrent with reducing its main regulator IKBKE and NF-κB signaling pathway proteins in both TNBC cell lines. The total ERK1/2 protein was inhibited in the more responsive MDA-MB-231 cells. SANG exhibited a higher potential to inhibit cell migration in MDA-MB-231 cells compared to MDA-MB-468 cells. Data obtained in this study suggest a unique antiangiogenic and antimetastatic effect of SANG in the MDA-MB-231 cell model. These effects are related to the compound’s ability to inhibit the angiogenic CCL2 and impact the ERK1/2 pathway. Therefore, SANG use may be recommended as a component of the therapeutic strategy for TNBC.

Polyphenols Modulating Effects of PD-L1/PD-1 Checkpoint and EMT-Mediated PD-L1 Overexpression in Breast Cancer

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.

Rosmarinic acid-induced apoptosis and cell cycle arrest in triple-negative breast cancer cells

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 G0/G1 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.

Effects of gossypol on apoptosis‑related gene expression in racially distinct triple‑negative breast cancer cells

Apoptosis is a gene‑directed mechanism that regulates cell proliferation and maintains homeostasis. Moreover, an aberrant apoptotic process can lead to several pathological conditions, such as tumorigenesis and cancer metastasis. In the present study, the apoptotic effect of the natural polyphenol compound gossypol GOSS) was investigated in triple‑negative breast cancer TNBC) cells. The effect of GOSS was evaluated in two cell lines representative of a Caucasian‑American and African‑American origin, MDA‑MB‑231 MM‑231) and MDA‑MB‑468 MM‑468), respectively. A similar response to both cytotoxicity and proliferation was observed in the two cell lines. However, MM‑468 cells were 2‑fold more sensitive to the apoptotic effect of the compound, which was accompanied by a longer delay in colony formation. Furthermore, GOSS was found to alter the mRNA expression of many apoptosis‑related genes. The compound significantly upregulated growth arrest and DNA damage‑inducible 45 alpha protein (GADD45A), tumor necrosis factor receptor superfamily 9 (TNFRSF9) and BCL2 interacting protein 3 BNIP3) in MM‑231 cells. Similarly, GADD45A and BNIP3 were upregulated in MM‑468 cells. A significant finding in this study is the profound 159‑fold increase in TNF gene expression that was observed in MM‑468 cells. Moreover, the apoptosis‑suppressor gene baculoviral IAP repeat containing 5 BIRC5) was significantly repressed (by more than 90%) in both cell lines, as well as death‑associated protein kinase 1 (DAPK1) in MM‑231 cells and tumor protein 73 (TP73) in MM‑468 cells. In conclusion, the data obtained in this study provide a molecular understanding of the GOSS‑induced apoptosis effect and suggest the importance of this polyphenol compound targeted towards TNBC treatment, particularly in African‑American women.

The inhibitory effects of plumbagin on the NF-қB pathway and CCL2 release in racially different triple-negative breast cancer cells

Breast cancer (BC) is the second leading cause of death among women in the US, and its subtype triple-negative BC (TNBC) is the most aggressive BC with poor prognosis. In the current study, we investigated the anticancer effects of the natural product plumbagin (PL) on racially different TNBC cells. The PL effects were examined in two TNBC cell lines: MDA-MB-231 (MM-231) and MDA-MB-468 (MM-468), representing Caucasian Americans and African Americans, respectively. The results obtained indicate that PL inhibited cell viability and cell proliferation and induced apoptosis in both cell lines. Notably, MM-468 cells were 5-fold more sensitive to PL than MM-231 cells were. Testing PL and Taxol® showed the superiority of PL over Taxol® as an antiproliferative agent in MM-468 cells. PL treatment resulted in an approximately 20-fold increase in caspase-3 activity with 3 μM PL in MM-468 cells compared with an approximately 3-fold activity increase in MM-231 cells with 8 μM PL. Moreover, the results indicate a higher sensitivity to PL in MM-468 cells than in MM-231 cells. The results also show that PL downregulated CCL2 cytokine expression in MM-468 cells by 30% compared to a 90% downregulation in MM-231 cells. The ELISA results confirmed the array data (35% vs. 75% downregulation in MM-468 and MM-231 cells, respectively). Moreover, PL significantly downregulated IL-6 and GM-CSF in the MM-231 cells. Indeed, PL repressed many NF-қB-regulated genes involved in the regulation of apoptosis, proliferation, invasion, and metastasis. The compound significantly downregulated the same genes (BIRC3, CCL2, TLR2, and TNF) in both types of cells. However, PL impacted five more genes in MM-231 cells, including BCL2A1, ICAM1, IKBKE, IL1β, and LTA. In conclusion, the data obtained in this study indicate that the quinone compound PL could be a novel cancer treatment for TNBC in African American women.

The attenuating effects of plumbagin on pro-inflammatory cytokine expression in LPS-activated BV-2 microglial cells

Activated microglial cells produce the pro-inflammatory mediators such as nitric oxide (NO) and cytokines. The excessive release of these mediators can lead to neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD). Inhibition of the release of these pro-inflammatory molecules may prevent or halt the progression of these diseases. Plumbagin (PL), a naphthoquinone compound in the roots of the traditional medicinal plant Plumbago zeylanica L., showed anti-inflammatory effects on macrophages. However, PL effects on activated microglia remain unknown. In the present study, PL has been examined for its anti-inflammatory effect on LPS - activated microglial BV-2 cells. In this study, NO and iNOS expression were investigated in BV-2 microglial cells in the presence of PL or the selective iNOS inhibitor L-N6-(1-iminoethyl) lysine (L-NIL). The results obtained indicate that PL was >30-fold potent than L-NIL in inhibiting NO production with an IC₅₀ of 0.39μM. Our immunofluorescence study confirmed the ability of PL to significantly inhibit iNOS expression in the activated microglia. Furthermore, the extracellular microglial pro-inflammatory cytokine expression in the presence of 2μM of PL was detected, quantified, and validated using cytokine antibody protein arrays and quantitative ELISA. The results obtained showed that PL significantly downregulated the expression of many cytokines including IL-1α, G-CSF, IL-12 p40/p70, MCP-5, MCP-1, and IL-6. In conclusion, PL potency in attenuating multiple pro-inflammatory agents indicates its potential to be used for neurodegenerative diseases.

The Benzopyrone Biochanin-A as a reversible, competitive, and selective monoamine oxidase B inhibitor

Background

Monoamine 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.

Methods

In 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.

Results

The 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 (K_i) 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.

Conclusions

The 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.

Natural Products Screening for the Identification of Selective Monoamine Oxidase-B Inhibitors

Aims

Monoamine oxidase-B inhibitors (MAO-BIs) are used for the initial therapy of Parkinson’s disease. Also, MAO-BIs have shown to be effective neuroprotective agents in several neurodegenerative diseases. However, some concerns exist regarding the long-term use of these compounds. Meanwhile, natural compounds showed potential MAO-B selective inhibitions. To date, few selective natural MAO-BIs have been identified. Therefore, the current study is designed to identify plants with potent and specific MAO-B inhibition.

Study Design

In this work, we utilized high throughput screening to evaluate the different plants ethanolic extract for their effectiveness to inhibit recombinant human (h)MAO-A and hMAO-B and to determine the relative selectivity of the top MAO-BI.

Methodology

Recombinant human isozymes were verified by Western blotting, and the 155 plants were screened. A continuous fluorometric screening assay was performed followed by two separate hMAO-A and hMAO-B microtiter screenings and IC₅₀ determinations for the top extracts.

Results

In the screened plants, 9% of the extracts showed more than 1.5-fold relative inhibition of hMAO-B (RI_B) and another 9% showed more than 1.5-fold relative inhibition of hMAO-A. The top extracts with the most potent RI_Bs were Psoralea corylifolia seeds, Phellodendron amurense bark, Glycyrrhiza uralensis roots, and Ferula assafoetida roots, with the highest RI_B of 5.9-fold. Furthermore, extensive maceration of the promising extracts led to increase inhibitory effects with a preserved RI_B as confirmed with luminescence assay. The top four extracts hMAO-BIs were equally potent (IC₅₀= 1.3 to 3.8 μg/mL) with highly significant relative selectivities to inhibit hMAO-B (4.1- to 13.4-fold).

Conclusion

The obtained results indicate that Psoralea corylifolia seeds, Ferula assafoetida, Glycyrrhiza uralensis roots, and Phellodendron amurense ethanolic extracts have selective inhibitions for human MAO-B. Investigating these plant extracts as natural resources for novel selective MAO-BIs may lead to the development of molecules that can be used in the therapeutic management of neurodegenerative diseases including Parkinson’s disease.

The Role of Monocarboxylate Transporters and Their Chaperone CD147 in Lactate Efflux Inhibition and the Anticancer Effects of Terminalia chebula in Neuroblastoma Cell Line N2-A

AIMS

In the presence of oxygen, most of the synthesized pyruvate during glycolysis in the cancer cell of solid tumors is released away from the mitochondria to form lactate (Warburg Effect). To maintain cell homeostasis, lactate is transported across the cell membrane by monocarboxylate transporters (MCTs). The major aim of the current investigation is to identify novel compounds that inhibit lactate efflux that may lead to identifying effective targets for cancer treatment.

STUDY DESIGN

In this study, 900 ethanol plant extracts were screened for their lactate efflux inhibition using neuroblastoma (N2-A) cell line. Additionally, we investigated the mechanism of inhibition for the most potent plant extract regarding monocarboxylate transporters expression, and consequences effects on viability, growth, and apoptosis.

METHODOLOGY

The potency of lactate efflux inhibition of ethanol plant extracts was evaluated in N2-A cells by measuring extracellular lactate levels. Caspase 3- activity and acridine orange/ethidium bromide staining were performed to assess the apoptotic effect. The antiproliferative effect was measured using WST assay. Western blotting was performed to quantify protein expression of MCTs and their chaperone CD147 in treated cells lysates.

RESULTS

Terminalia chebula plant extract was the most potent lactate efflux inhibitor in N2-A cells among the 900 - tested plant extracts. The results obtained show that extract of Terminalia chebula fruits (TCE) significantly (P = 0.05) reduced the expression of the MCT1, MCT3, MCT4 and the chaperone CD147. The plant extract was more potent (IC₅₀ of 3.59 ± 0.26 μg/ml) than the MCT standard inhibitor phloretin (IC₅₀ 76.54 ± 3.19 μg/ml). The extract also showed more potency and selective cytotoxicity in cancer cells than DI-TNC1 primary cell line (IC₅₀ 7.37 ± 0.28 vs. 17.35 ± 0.19 μg/ml). Moreover, TCE Inhibited N2-A cell growth (IG₅₀ = 5.20 ± 0.30 μg/ml) and induced apoptosis at the 7.5 μg/ml concentration.

CONCLUSION

Out of the 900 plant extracts screened, Terminalia chebula ethanol extract was found to be the most potent lactate efflux inhibitor with the ability to inhibit chaperone CD147 expression and impact the function of monocarboxylate transporters. Furthermore, TCE was found to have growth inhibition and apoptotic effects. The results obtained indicate that Terminalia chebula constituent(s) may contain promising compounds that can be useful in the management of neuroblastoma cancer.