Ramentaceone, a Naphthoquinone Derived from Drosera sp., Induces Apoptosis by Suppressing PI3K/Akt Signaling in Breast Cancer Cells

Allyl ether of mansonone G as a potential anticancer agent for colorectal cancer

Mansonone G (MG), a 1,2-naphthoquinone isolated from the heartwood of Mansonia gagei Drumm, exhibited several pharmacological activities such as anti-bacterial, anti-estrogenic and anti-adipogenic effect. This study evaluated the cytotoxicity of MG and its derivatives as well as determined the mechanism(s) underlying the cytotoxic activity of the most potent MG derivative on two CRC cell lines, HCT-116 cells carrying p53 wild-type and HT-29 cells carrying p53 mutant. We found that MG and its derivatives could inhibit viability of HCT-116 and HT-29 cells in a concentration-dependent manner. Of all semi-synthetic derivatives of MG, allyl ether mansonone G (MG7) was the most potent cytotoxic agent toward cancer cells and less toxic to normal cells. MG7 could induce ROS generation which was associated with cytotoxicity and apoptosis in both HCT-116 and HT-29 cells. Western blot analysis revealed that MG7 downregulated the expression of Bcl-2 and Bcl-xL proteins in both CRC cell lines and upregulated the expression of BAK protein in HT-29 cells. Moreover, MG7 inhibited AKT signaling pathway in both CRC cell lines and modulated ERK1/2 signaling pathway by inhibiting ERK1/2 phosphorylation in HCT-116 cells and activating ERK1/2 phosphorylation in HT-29 cells. Molecular docking revealed that MG7 could bind to the ATP-binding pocket of AKT and ERK1 via hydrophobic interactions.

Promoting Apoptosis, a Promising Way to Treat Breast Cancer With Natural Products: A Comprehensive Review

Breast cancer is one of the top-ranked malignant carcinomas associated with morbidity and mortality in women worldwide. Chemotherapy is one of the main approaches to breast cancer treatment. Breast cancer initially responds to traditional first- and second-line drugs (aromatase inhibitor, tamoxifen, and carboplatin), but eventually acquires resistance, and certain patients relapse within 5 years. Chemotherapeutic drugs also have obvious toxic effects. In recent years, natural products have been widely used in breast cancer research because of their low side effects, low toxicity, and good efficacy based on their multitarget therapy. Apoptosis, a programmed cell death, occurs as a normal and controlled process that promotes cell growth and death. Inducing apoptosis is an important strategy to control excessive breast cancer cell proliferation. Accumulating evidence has revealed that natural products become increasingly important in breast cancer treatment by suppressing cell apoptosis. In this study, we reviewed current studies on natural product–induced breast cancer cell apoptosis and summarized the proapoptosis mechanisms including mitochondrial, FasL/Fas, PI3K/AKT, reactive oxygen species, and mitogen-activated protein kinase–mediated pathway. We hope that our review can provide direction in the search for candidate drugs derived from natural products to treat breast cancer by promoting cell apoptosis.

Naphthoquinone Derivatives Isolated from Plants: Recent Advances in Biological Activity

Naturally occurring naphthoquinones (NQs) comprising highly reactive small molecules are the subject of increasing attention due to their promising biological activities such as antioxidant, antimicrobial, apoptosis-inducing activities, and especially anticancer activity. Lapachol, lapachone, and napabucasin belong to the NQs and are in phase II clinical trials for the treatment of many cancers. This review aims to provide a comprehensive and updated overview on the biological activities of several new NQs isolated from different species of plants reported from January 2013 to January 2020, their potential therapeutic applications and their clinical significance.

Plumbagin inhibited AKT signaling pathway in HER-2 overexpressed-endocrine resistant breast cancer cells

The important mechanism of endocrine resistance is the crosstalk between estrogen receptor (ER) and HER2 signaling pathways. Aside from ER downregulation, there was an increase in HER2 expression and increased activation of the downstream AKT/ERK pathways in endocrine-resistant cells (MCF-7/LCC2 and MCF-7/LCC9) which is similar to HER2-overexpressed (SKBR3) cells. However, nuclear receptor coactivator 3 (NCOA3), the important ER-coactivator, that upregulated in endocrine-resistant cells did not express in HER2-overexpressed (SKBR3) cells. NCOA3 was able to activate AKT/ERK signalling pathway. Our previous study reported that plumbagin (PLB), a naphthoquinone compound, had a potent cytotoxic activity against endocrine-resistant cells. This study aimed to further investigate the mechanism of anti-cancer effects of PLB on ER and HER-2 signaling. PLB can inhibit estradiol (E₂)-induced cell proliferation in MCF-7 wild-type cells but had no effect in the resistant cells. It also inhibited HER2 expression in both endocrine-resistant and HER-2 overexpressed cells. Therefore, the mechanism of PLB may be regulated through HER-2 signaling. PLB inhibited the phosphorylation of AKT (pAKT) and pERK1/2 and induced apoptosis and reduced the expression of anti-apoptotic genes Bcl-2 and pro-caspase 3 and Cleaved Caspase 3 protein in both endocrine-resistant and HER-2 overexpressed cells. However, the inhibitory effect of PLB was more obvious when pre-treated the cells with AKT inhibitor only in HER-2 overexpressed cells. In addition, the inhibitory effect of PLB on pAKT was attenuated when NCOA3 was downregulated. Our finding suggested that the inhibitory effect of PLB on AKT signaling pathways regulated through NCOA3 in HER2-overexpressed endocrine-resistant cells.

Butoxy Mansonone G Inhibits STAT3 and Akt Signaling Pathways in Non-Small Cell Lung Cancers: Combined Experimental and Theoretical Investigations

Epidermal growth factor receptor (EGFR) is the key molecular target for non-small cell lung cancer (NSCLC) due to its major contribution to complex signaling cascades modulating the survival of cancer cells. Targeting EGFR-mediated signaling pathways has been proved as a potential strategy for NSCLC treatment. In the present study, mansonone G (MG), a naturally occurring quinone-containing compound, and its semi-synthetic ether derivatives were subjected to investigate the anticancer effects on human NSCLC cell lines expressing wild-type EGFR (A549) and mutant EGFR (H1975). In vitro cytotoxicity screening results demonstrated that butoxy MG (MG3) exhibits the potent cytotoxic effect on both A549 (IC₅₀ of 8.54 μM) and H1975 (IC₅₀ of 4.21 μM) NSCLC cell lines with low toxicity against PCS201-010 normal fibroblast cells (IC₅₀ of 21.16 μM). Western blotting and flow cytometric analyses revealed that MG3 induces a caspase-dependent apoptosis mechanism through: (i) inhibition of p-STAT3 and p-Akt without affecting upstream p-EGFR and (ii) activation of p-Erk. The 500-ns molecular dynamics simulations and the molecular mechanics combined with generalized Born surface area (MM/GBSA)-based binding free energy calculations suggested that MG3 could possibly interact with STAT3 SH2 domain and ATP-binding pocket of Akt. According to principal component analysis, the binding of MG3 toward STAT3 and Akt dramatically altered the conformation of proteins, especially the residues in the active site, stabilizing MG3 mainly through van der Waals interactions.

Paris polyphylla 26 triggers G2/M phase arrest and induces apoptosis in HepG2 cells via inhibition of the Akt signaling pathway

Objectives

Paris polyphylla 26 (PP-26) is a monomer purified from Paris polyphylla, which has traditionally been used as an antimicrobial, hemostatic, and anticancer agent in China. The anti-proliferation effect and underlying molecular mechanism of PP-26 were investigated in vitro.

Methods

The effects of PP-26 on various tumor cells were detected by MTT assay. PP-26-affected cell cycle and cell cycle-related proteins in HepG2 cells were detected by flow cytometry and western blotting, respectively. Apoptosis in response to PP-26 was assessed by Hoechst 33258 staining and flow cytometry. PP-26-affected apoptosis-related proteins and Akt signaling were detected by western blotting. The inhibitory effect of PP-26 on HepG2 cells, when combined with 5-fluorouracil (5-FU), was also assessed.

Results

PP-26 inhibited proliferation of HepG2 cells in a dose-dependent manner by triggering G2/M-phase arrest. Moreover, PP-26 induced apoptosis of HepG2 cells. Expression levels of apoptosis proteins caspase 9, caspase 3, PARP, Bcl-2, Bcl-xL, and Mcl-1 were downregulated, while the expression level of apoptosis protein Bax was upregulated. Expression levels of p-Akt, p-GSK-3β, and p-Foxo3 were downregulated. Combination with PP-26 enhanced 5-FU inhibition of HepG2 cell proliferation.

Conclusions

PP-26 triggers G2/M-phase arrest and induces apoptosis in HepG2 cells via inhibition of the Akt signaling pathway.

Novel 1,4‑naphthoquinone derivatives induce reactive oxygen species‑mediated apoptosis in liver cancer cells

Derivatives of 1,4-naphthoquinone have excellent anti-cancer effects, but their use has been greatly limited due to their serious side effects. To develop compounds with decreased side effects and improved anti-cancer activity, two novel types of 1,4-naphthoquinone derivatives, 2,3-dihydro-2,3-epoxy-2-propylsulfonyl-5,8-dimethoxy-1,4-naphthoquinone (EPDMNQ) and 2,3-dihydro-2,3-epoxy-2-nonylsulfonyl-5,8-dimethoxy-1,4-naphthoquinone (ENDMNQ) were synthesized and their anti-tumor activities were investigated. The effects of EPDMNQ and ENDMNQ on cell viability, apoptosis and accumulation of reactive oxygen species (ROS) in liver cancer cells were determined by MTT cell viability assay and flow cytometry. The expression levels of mitochondrial, mitogen activated protein kinase (MAPK) and signal transducer and activator of transcription 3 (STAT3) signaling pathway-associated proteins in Hep3B liver cancer cells were analyzed by western blot analysis. The results demonstrated that EPDMNQ and ENDMNQ inhibited the proliferation of liver cancer Hep3B, HepG2, and Huh7 cell lines but not that of normal liver L-02, normal lung IMR-90 and stomach GES-1 cell lines. The number of apoptotic cells and ROS levels were significantly increased following treatment with EPDMNQ and ENDMNQ, and these effects were blocked by the ROS inhibitor N-acetyl-L-cysteine (NAC) in Hep3B cells. EPDMNQ and ENDMNQ induced apoptosis by upregulating the protein expression of p38 MAPK and c-Jun N-terminal kinase and downregulating extracellular signal-regulated kinase and STAT3; these effects were inhibited by NAC. The results of the present study demonstrated that EPDMNQ and ENDMNQ induced apoptosis through ROS-modulated MAPK and STAT3 signaling pathways in Hep3B cells. Therefore, these novel 1,4-naphthoquinone derivatives may be useful as anticancer agents for the treatment of liver cancer.

The compound 2-(naphthalene-2-thio)-5,8-dimethoxy-1,4-naphthoquinone induces apoptosis via reactive oxygen species-regulated mitogen-activated protein kinase, protein kinase B, and signal transducer and activator of transcription 3 signaling in human gastric cancer cells

Hit, Lead & Candidate Discovery It is reported that 1,4-naphthoquinones and their derivatives have potent antitumor activity in various cancers, although their clinical application is limited by observed side effects. To improve the therapeutic efficacy of naphthoquinones in the treatment of cancer and to reduce side effects, we synthesized a novel naphthoquinone derivative, 2-(naphthalene-2-thio)-5,8-dimethoxy-1,4-naphthoquinone (NTDMNQ). In this study, we explored the effects of NTDMNQ on apoptosis in gastric cancer cells with a focus on reactive oxygen species (ROS) production. Our results demonstrated that NTDMNQ exhibited the cytotoxic effects on gastric cancer cells in a dose-dependent manner. NTDMNQ significantly induced mitochondrial-related apoptosis in AGS cells and increased the accumulation of ROS. However, pre-treatment with N-acetyl-L-cysteine (NAC), an ROS scavenger, inhibited the NTDMNQ-induced apoptosis. In addition, NTDMNQ increased the phosphorylation of p38 kinase and c-Jun N-terminal kinase (JNK) and decreased the phosphorylation of extracellular signal-regulated kinase (ERK), protein kinase B (Akt), and Signal Transducer and Activator of Transcription 3 (STAT3); these effects were blocked by mitogen-activated protein kinase (MAPK) inhibitor and NAC. Taken together, the present findings indicate that NTDMNQ-induced gastric cancer cell apoptosis via ROS-mediated regulation of the MAPK, Akt, and STAT3 signaling pathways. Therefore, NTDMNQ may be a potential treatment for gastric cancer as well as other tumor types.

microRNA‑630 promotes cell proliferation and inhibits apoptosis in the HCT116 human colorectal cancer cell line

Dysregulation of microRNAs (miRNAs) in colorectal cancer provides important opportunities for the development of future miRNA‑based therapies. The present study aimed to assess the role of miRNA‑630 (miR‑630) expression in colorectal cancer. HCT116 human colorectal cancer cells were transfected with miR‑630 inhibitor, mimic or control miRNA, and the effects of miR‑630 dysregulation on cell viability, proliferation and apoptosis were analyzed using MTT and bromodeoxyuridine assays, and an annexin V‑fluorescein isothiocyanate cell apoptosis kit, respectively. In addition, the changes in the protein expression of proliferation‑associated and AKT signaling pathway proteins were analyzed by western blot analysis. The results of the present study demonstrated that overexpression of miR‑630 significantly promoted HCT116 cell proliferation however inhibited apoptosis. Furthermore, miR‑630 overexpression reduced the protein expression of p27, BCL2‑associated X apoptosis regulator, procaspase‑3 and active caspase‑3, and increased the levels of phosphorylated‑AKT and BCL2 apoptosis regulator. The suppression of miR‑630 led to the opposite results. In conclusion, the present findings suggested that miR‑630 may function as an oncogenic miRNA in colorectal cancer, and may promote cellular proliferation and inhibit apoptosis, through the regulation of the expression of p27 and the AKT signaling pathway. The present study suggested that the inhibition of miR‑630 may have potential as an alternative therapeutic strategy for the treatment of patients with colorectal cancer.

Gelatin-albumin hybrid nanoparticles as matrix metalloproteinases-degradable delivery systems for breast cancer therapy

AIM

To develop matrix metalloproteinase-responsive gelatin-albumin hybrid nanoparticles encapsulating a selective tropomyosin receptor kinase A (TrkA) inhibitor GNF-5837 (Gel-Alb-GNF HNPs) and to demonstrate their anticancer effects in breast cancer.

METHODS

Gel-Alb-GNF HNPs were prepared using a pH-controlled complexation process from cationic gelatin, dextran sulfate and albumin-bound GNF-5837. The anticancer activities of Gel-Alb-GNF HNPs were tested in a panel of subtype-specific breast cancer cell lines.

RESULTS

Gel-Alb-GNF HNPs (∼130 nm) displayed excellent stability and matrix metalloproteinase-triggered drug release. Compared with GNF-5837 alone, Gel-Alb-GNF HNPs not only significantly enhanced the antiproliferative and anti-invasive effects but also restored the apoptosis of cancer cells.

CONCLUSION

Gel-Alb-GNF HNPs may be adaptable for stand-alone therapies or used in combination with traditional chemotherapies for breast cancer treatment.

MicroRNA-1284 Inhibits Cell Viability and Induces Apoptosis of Ovarian Cancer Cell Line OVCAR3

Ovarian cancer is a malignancy with high mortality among women. Multiple reports show that microRNAs (miRs) act as regulators in ovarian cancer inhibition, while the role of miR-1284 in ovarian cancer is still unknown. This study aimed to investigate the effects of miR-1284 on ovarian cancer cells. Human ovarian cancer cell line OVCAR3 was cultured and transfected with miR-1284 mimics, inhibitors, or control. Viability and apoptosis of transfected cells were then determined by MTT assay, BrdU assay, and flow cytometry. Expression changes of p27, p21, and PI3K/Akt pathway-related proteins were measured by Western blot. Results showed that miR-1284 overexpression suppressed cell viability while increasing the apoptosis in OVCAR3 cells. Moreover, the expression level of p27 was upregulated by miR-1284 overexpression. Furthermore, miR-1284 overexpression and Akt inhibitor GSK690693 downregulated the levels of p-Akt and Bcl-2 while upregulating the levels of Bax and caspase 3. However, miR-1284 suppression attenuated the regulatory effects of GSK690693 on these proteins. In conclusion, miR-1284 could inhibit cell viability via regulating the expression of p27 and induce apoptosis via regulating the PI3K/Akt pathway in OVCAR3 cells.

Plumbagin sensitizes breast cancer cells to tamoxifen-induced cell death through GRP78 inhibition and Bik upregulation

The glucose regulated protein 78 (GRP78) is a major chaperone of the endoplasmic reticulum, and a prosurvival component of the unfolded protein response. GRP78 is upregulated in many types of cancers, including breast cancer. Research has suggested that GRP78 overexpression confers chemoresistance to anti-estrogen agents through a mechanism involving the inhibition of a pro-apoptotic BH3-only protein, Bik. In the present research the role of plumbagin, a naturally occurring naphthoquinone, in GRP78-associated cell death inhibition was examined. The results demonstrated that plumbagin inhibits GRP78 activity and GRP78 inhibition contributes to plumbagin-mediated cell death induction. Furthermore, Bik upregulation was associated with plumbagin-induced cell death and an increase in plumbagin-mediated Bik induction was observed upon GRP78 downregulation. Plumbagin sensitized estrogen-positive breast cancer cells to tamoxifen and the association of GRP78 inhibition and Bik upregulation in plumbagin-mediated cell sensitization was shown. Collectively, the results of this research suggest that plumbagin inhibits the antiapoptotic activity of GRP78 leading to Bik upregulation and apoptosis induction, which contributes to the sensitization of breast cancer cells to tamoxifen.

Anti-tumor effect of evodiamine by inducing Akt-mediated apoptosis in hepatocellular carcinoma

BACKGROUND

Evodiamine is an alkaloid extracted from Euodia rutaecarpa (Juss.) Benth. There is little information about the mechanisms of evodiamine on the apoptosis of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

A xenograft model and CCK8 assay were used to investigate the anti-HCC effect of evodiamine. The effect of evodiamine on apoptosis was evaluated by DAPI staining and flow cytometry. Western blot analyses and immunohistochemistry were processed to assess the protein expressions of Akt and apoptotic proteins.

RESULTS

Evodiamine suppressed tumor growth, improved the expression of cleaved-caspase3 and decreased tumor specific growth factor (TSGF) and alpha fetoprotein (AFP) activities. Furthermore, evodiamine inhibited cell viability and induced cell cycle arrest. DAPI staining revealed nuclear condensation in evodiamine-treated groups. Meanwhile, evodiamine increased the number of apoptotic cells. Furthermore, evodiamine suppressed Akt and regulated apoptotic proteins in HepG2 cells. Evodiamine decreased p-Akt levels activated by SC79, which led to the increase of bax/bcl-2 and cleaved-caspase3.

CONCLUSIONS

Our findings suggested that evodiamine could exert anti-HCC effect through inducing Akt-mediated apoptosis. Evodiamine has the potential to be a therapeutic medicine for HCCs.

Plumbagin Suppresses the Invasion of HER2-Overexpressing Breast Cancer Cells through Inhibition of IKKα-Mediated NF-κB Activation

HER2-overexpressing breast cancers account for about 30% of breast cancer occurrences and have been correlated with increased tumor aggressiveness and invasiveness. The nuclear factor-κB (NF-κB) is overexpressed in a subset of HER2-positive breast cancers and its upregulation has been associated with the metastatic potential of HER2-overexpressing tumors. The present study aimed at determining the potential of plumbagin, a naturally occurring naphthoquinone, to inhibit the invasion of HER2-overexpressing breast cancer cells and determine the involvement of NF-κB inhibition in plumbagin-mediated cell invasion suppression. In the present research we showed that plumbagin inhibited the transcriptional activity of NF-κB in HER2-positive breast cancer cells. The suppression of NF-κB activation corresponded with the inhibition of NF-κB p65 phosphorylation and downregulation of NF-κB-regulated matrix metalloproteinase 9 (MMP-9) expression. Plumbagin suppressed the invasion of HER2-overexpressing breast cancer cells and the inhibition of cell invasion was associated with the ability of plumbagin to inhibit NF-κB transcriptional activity. The silencing of NF-κB p65 increased the sensitivity of HER2-overexpressing breast cancer cells to plumbagin-induced cell invasion inhibition. NF-κB inhibition was associated with IκB kinase α (IKKα) activity suppression and inhibition of IκBα phosphorylation and degradation. The knockdown of IKKα resulted in increased sensitivity of HER2-positive cells to plumbagin-induced suppression of NF-κB transcriptional activity and expression of MMP-9. In conclusion, plumbagin inhibits the invasion of HER2-overexpressing breast cancer cells through the inhibition of IKKα-mediated NF-κB activation and downregulation of NF-κB-regulated MMP-9 expression.

2-cyclohexylamino-5,8-dimethoxy-1,4-naphthoquinone inhibits LPS-induced BV2 microglial activation through MAPK/NF-kB signaling pathways

AIMS

To verify the effects of several 5,8-dimethoxy-1,4-naphthoquinone (DMNQ) derivatives on LPS-induced NO production, cellular ROS levels and cytokine expression in BV-2 microglial cells.

MAIN METHODS

An MTT assay and FACS flow cytometry were performed to assess the cellular viability and apoptosis and cellular ROS levels, respectively. To examine the expression of pro-inflammatory cytokines and cellular signaling pathways, semi-quantitative RT-PCR and Western blotting were also used in this study.

KEY FINDINGS

Among the six newly synthesized DMNQ derivatives, 2-cyclohexylamino-5,8-dimethoxy-1,4-naphthoquinone (R6) significantly inhibited the NO production, cellular ROS levels and the cytokines expression in BV-2 microglial cells, which stimulated by LPS. Signaling study showed that compound R6 treatment also significantly down-regulated the LPS-induced phosphorylation of MAPKs (ERK, JNK and p38) and decreased the degradation of IκB-α in BV2 microglial cells.

SIGNIFICANCE

Our findings demonstrate that our newly synthesized compound derived from DMNQ, 2-cyclohexylamino-5,8-dimethoxy-1,4-naphthoquinone (R6), might be a therapeutic agent for the treatment of glia-mediated neuroinflammatory diseases.

Biosynthesis and molecular actions of specialized 1,4-naphthoquinone natural products produced by horticultural plants

The 1,4-naphthoquinones (1,4-NQs) are a diverse group of natural products found in every kingdom of life. Plants, including many horticultural species, collectively synthesize hundreds of specialized 1,4-NQs with ecological roles in plant-plant (allelopathy), plant-insect and plant-microbe interactions. Numerous horticultural plants producing 1,4-NQs have also served as sources of traditional medicines for hundreds of years. As a result, horticultural species have been at the forefront of many basic studies conducted to understand the metabolism and function of specialized plant 1,4-NQs. Several 1,4-NQ natural products derived from horticultural plants have also emerged as promising scaffolds for developing new drugs. In this review, the current understanding of the core metabolic pathways leading to plant 1,4-NQs is provided with additional emphasis on downstream natural products originating from horticultural species. An overview on the biochemical mechanisms of action, both from an ecological and pharmacological perspective, of 1,4-NQs derived from horticultural plants is also provided. In addition, future directions for improving basic knowledge about plant 1,4-NQ metabolism are discussed.