Plumbagin enhances TRAIL-induced apoptosis of human leukemic Kasumi-1 cells through upregulation of TRAIL death receptor expression, activation of caspase-8 and inhibition of cFLIP

Maximizing arsenic trioxide's anticancer potential: Targeted nanocarriers for solid tumor therapy

Arsenic trioxide (ATO) has gained significant attention due to its promising therapeutic effects in treating different diseases, particularly acute promyelocytic leukemia (APL). Its potent anticancer mechanisms have been extensively studied. Despite the great efficacy ATO shows in fighting cancers, drawbacks in the clinical use are obvious, especially for solid tumors, which include rapid renal clearance and short half-life, severe adverse effects, and high toxicity to normal cells. Recently, the emergence of nanomedicine offers a potential solution to these limitations. The enhanced biocompatibility, excellent targeting capability, and desirable effectiveness have attracted much interest. Therefore, we summarized various nanocarriers for targeted delivery of ATO to solid tumors. We also provided detailed anticancer mechanisms of ATO in treating cancers, its clinical trials and shortcomings as well as the combination therapy of ATO and other chemotherapeutic agents for reduced drug resistance and synergistic effects. Finally, the future study direction and prospects were also presented.

Natural quinones induce ROS-mediated apoptosis and inhibit cell migration in PANC-1 human pancreatic cancer cell line

Pancreatic cancer is one of the most devastating of all malignancies with poor prognosis and high mortality rates worldwide. Thymoquinone, plumbagin and juglone, which are naturally occurring quinones, have been reported for their promising anticancer effect on different cancer cells. However, their mechanism of action and antimetastatic effects are largely unknown against the human pancreatic cancer cell line (PANC-1). In this study, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assay revealed a dose-dependent decrease of viability in quinone-treated PANC-1 cells. In addition, the assessment of changes in cells has demonstrated an occurrence of typical apoptotic morphology in treated PANC-1 cells compared with control. Besides this, the apoptosis induction was further quantitatively confirmed through flow cytometry analysis. Furthermore, thymoquinone, plumbagin and juglone were evaluated for their influence on reactive oxygen species (ROS) generation through 2,7-dichlorofluorescein diacetate (DCFDA) staining and they dramatically increased the intracellular ROS level in treated PANC-1 cells, suggesting the critical role of ROS in their apoptosis induction. This study also demonstrated the wound healing potential of these compounds and inhibited PANC-1 cell migration in a time-dependent manner compared with control. This inhibition was correlated with reduced expression of matrix metalloproteinase-9 (MMP-9) in juglone-treated cells detected through gelatin zymography. In conclusion, thymoquinone, plumbagin and juglone significantly inhibited cell growth and induced ROS-mediated apoptosis in PANC-1 cells. In addition, they could be potent antimetastatic agents due to their anti-migratory effect against PANC-1 human pancreatic cancer cells.

CSC-3436 sensitizes triple negative breast cancer cells to TRAIL-induced apoptosis through ROS-mediated p38/CHOP/death receptor 5 signaling pathways

Tumor necrosis factor-related apoptosis-induced ligand (TRAIL) shows little or no toxicity in most normal cells and preferentially induces apoptosis in a variety of malignant cells. However, patients develop resistance to TRAIL, therefore, sensitizing agents that can sensitize the tumor cells to TRAIL-mediated apoptosis are necessary. In this study, we investigated the effect of 2-(3-hydroxyphenyl)-5-methylnaphthyridin-4-one (CSC-3436), an useful flavonoid, to overcome the TRAIL-resistant triple negative breast cancer (TNBC) cells. We found that CSC-3436 potentiated TRAIL-induced apoptosis in TRAIL-resistant TNBC cells and this correlated with the upregulation of death receptors (DR)-5 and down-regulation of decreased decoy receptor (DcR)-1 expression. When examined for its mechanism, we found that the decreased expression of anti-apoptotic proteins c-FLIPS/L, Bcl-Xl, Bcl-2, Survivin, and XIAP. CSC-3436 would increase the expression of Bax and promoted the cleavage of bid. In addition, the induction of DR5 by CSC-3436 was found to be dependent on the modulation of reactive oxygen species (ROS)/p38/C/EBP-homologous protein (CHOP) signaling pathways. Overall, our results indicated that CSC-3436 could potentiate the apoptotic effects of TRAIL through down-regulation of cell survival proteins and upregulation of DR5 via the ROS-mediated upregulation of CHOP protein.

JKST6, a novel multikinase modulator of the BCR-ABL1/STAT5 signaling pathway that potentiates direct BCR-ABL1 inhibition and overcomes imatinib resistance in chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) is a hematological malignancy that highly depends on the BCR-ABL1/STAT5 signaling pathway for cell survival. First-line treatments for CML consist of tyrosine kinase inhibitors that efficiently target BCR-ABL1 activity. However, drug resistance and intolerance are still therapeutic limitations in Ph+ cells. Therefore, the development of new anti-CML drugs that exhibit alternative mechanisms to overcome these limitations is a desirable goal. In this work, the antitumoral activity of JKST6, a naphthoquinone-pyrone hybrid, was assessed in imatinib-sensitive and imatinib-resistant human CML cells. Live-cell imaging analysis revealed JKST6 potent antiproliferative activity in 2D and 3D CML cultures. JKST6 provoked cell increase in the subG1 phase along with a reduction in the G0/G1 phase and altered the expression of key proteins involved in the control of mitosis and DNA damage. Rapid increases in Annexin V staining and activation/cleavage of caspases 8, 9 and 3 were observed after JKST6 treatment in CML cells. Of interest, JKST6 inhibited BCR-ABL1/STAT5 signaling through oncokinase downregulation that was preceded by rapid polyubiquitination. In addition, JKST6 caused a transient increase in JNK and AKT phosphorylation, whereas the phosphorylation of P38-MAPK and Src was reduced. Combinatory treatment unveiled synergistic effects between imatinib and JKST6. Notably, JKST6 maintained its antitumor efficacy in BCR-ABL1-T315I-positive cells and CML cells that overexpress BCR-ABL and even restored imatinib efficacy after a short exposure time. These findings, together with the observed low toxicity of JKST6, reveal a novel multikinase modulator that might overcome the limitations of BCR-ABL1 inhibitors in CML therapy.

Plumbagin Enhances the Radiosensitivity of Tongue Squamous Cell Carcinoma Cells via Downregulating ATM

This study was designed to investigate whether plumbagin (PL) could sensitize ionizing radiation (IR) in tongue squamous cell carcinoma (TSCC) cells and its possible mechanisms. Cell proliferation and combination index analysis was based on MTT and colony formation assay. Flow cytometry was applied to analyze the cell cycle distribution and apoptosis after the treatment of PL and/or IR. RT-PCR was used to examine the gene expression level of ataxia telangiegatasiata muted (ATM) and nuclear factor kappa beta (NF-κB) after various treatment groups. Western blot was used to examine the protein level of ATM and NF-κB as well as their phosphorylation level. PL enhances the cytotoxicity of IR in TSCC cells. Combination index was <1 which represents a synergistic effect. Combined PL and IR promoted G2/M arrest and apoptosis which could be reversed by ATM activator chloroquine phosphate. ATM and NF-κB were both inhibited by PL and IR combination. PL can efficiently enhance the radiosensitivity of TSCC cells by inducing G2/M arrest and apoptosis via downregulating ATM.

Nepenthes Ethyl Acetate Extract Provides Oxidative Stress-Dependent Anti-Leukemia Effects

Several kinds of solvents have been applied to Nepenthes extractions exhibiting antioxidant and anticancer effects. However, they were rarely investigated for Nepenthes ethyl acetate extract (EANT), especially leukemia cells. The purpose of the present study was to evaluate the antioxidant properties and explore the antiproliferation impact and mechanism of EANT in leukemia cells. Five standard assays demonstrated that EANT exhibits antioxidant capability. In the cell line model, EANT dose-responsively inhibited cell viabilities of three leukemia cell lines (HL-60, K-562, and MOLT-4) based on 24 h MTS assays, which were reverted by pretreating oxidative stress and apoptosis inhibitors (N-acetylcysteine and Z-VAD-FMK). Due to similar sensitivities among the three cell lines, leukemia HL-60 cells were chosen for exploring antiproliferation mechanisms. EANT caused subG1 and G1 cumulations, triggered annexin V-detected apoptosis, activated apoptotic caspase 3/7 activity, and induced poly ADP-ribose polymerase expression. Moreover, reactive oxygen species, mitochondrial superoxide, and mitochondrial membrane depolarization were generated by EANT, which was reverted by N-acetylcysteine. The antioxidant response to oxidative stress showed that EANT upregulated mRNA expressions for nuclear factor erythroid 2-like 2 (NFE2L2), catalase (CAT), thioredoxin (TXN), heme oxygenase 1 (HMOX1), and NAD(P)H quinone dehydrogenase 1 (NQO1) genes. Moreover, these oxidative stresses led to DNA damage (γH2AX and 8-hydroxy-2-deoxyguanosine) and were alleviated by N-acetylcysteine. Taken together, EANT demonstrated oxidative stress-dependent anti-leukemia ability to HL-60 cells associated with apoptosis and DNA damage.

Plumbagin suppresses non-small cell lung cancer progression through downregulating ARF1 and by elevating CD8+ T cells

Non-small cell lung cancer (NSCLC) is one of the most frequently diagnosed cancers and the leading causes of cancer death worldwide. Therefore, new therapeutic agents are urgently needed to improve patient outcomes. Plumbagin (PLB), a natural sesquiterpene present in many Chinese herbal medicines, has been reported for its anti-cancer activity in various cancer cells. In this study, the effects and underlying mechanisms of PLB on the tumorigenesis of NSCLC were investigated. PLB dose-dependently inhibited the growth of NSCLC cell lines. PLB promoted ROS production, activated the endoplasmic reticulum (ER) stress pathway, and induced cell apoptosis, accompanied by the decreased expression level of ADP-ribosylation factor 1 (ARF1) in NSCLC cancer cells, and those effects of PLB could be reversed by the pretreatment with N-acetyl-L-cysteine (NAC). More importantly, the calcium chelator (BM) significantly reversed PLB-induced cell apoptosis. Furthermore, PLB significantly inhibited the growth of both H1975 xenograft and LLC1 tumors and exhibited antitumor activity by enhancing the number and the effector function of CD8+ T cells in KRASLA2 mice model and the LLC1 xenograft. Our findings suggest that PLB exerts potent antitumor activity against NSCLC in vitro and in vivo through ARF1 downregulation and induction of antitumor immune response, indicating that PLB is a new novel therapeutic candidate for the treatment of patients with NSCLC.

Bioactive compounds and their libraries: An insight into prospective phytotherapeutics approach for oral mucocutaneous cancers

Oral mucocutaneous cancers (OMCs) are cancers that affect both the oral mucosa and perioral cutaneous structures. Common OMCs are squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and malignant melanoma (MM). Anatomical similarities and conventions which categorizes these lesions blur the magnitude of OMCs in diverse populations. The burden of OMC is high in the sub-Saharan Africa and Indian subcontinents, and the cost of management is prohibitive in the resource-limited, developing world. Hence, there is a pressing demand for the use of cost-effective in silico approaches to identify diagnostic tools and treatment targets for diseases with high burdens in these regions. Due to their ubiquitousness and accessibility, the use of therapeutic efficacy of plant bioactive compounds in the management of OMC is both appropriate and plausible. Furthermore, screening known mechanistic disease targets with well annotated plant bioactive compound libraries is poised to improve the routine management of OMCs provided that the requisite access to database resources are available and accessible. Using natural products minimizes the side effects and morbidities associated with conventional therapies. The development of innovative treatments approaches would tremendously benefit the African and Indian populace and reduce the mortalities associated with OMCs in the developing world. Hence, we discuss herein, the potential benefits, opportunities and challenges of using bioactive compound libraries in the management of OMCs.

Knockdown of Enhancer of Zeste Homolog 2 Affects mRNA Expression of Genes Involved in the Induction of Resistance to Apoptosis in MOLT-4 Cells

BACKGROUND

The Enhancer of Zeste Homolog 2 (EZH2) is a subunit of the polycomb repressive complex 2 that silences the gene transcription via H3K27me3. Previous studies have shown that EZH2 has an important role in the induction of the resistance against the Tumor necrosis factor-Related Apoptosis-Inducing Ligand (TRAIL)-Induced Apoptosis (TIA) in some leukemia cells.

OBJECTIVE

The aim of this study was to determine the effect of silencing EZH2 gene expression using RNA interference on the expression of death receptors 4 and 5 (DR4/5), Preferentially expressed Antigen in Melanoma (PRAME), and TRAIL human lymphoid leukemia MOLT-4 cells.

METHODS

Quantitative RT-PCR was used to detect the EZH2 expression and other candidate genes following the siRNA knockdown in MOLT-4 cells. The toxicity of the EZH2 siRNA was evaluated using Annexin V/PI assay following the transfection of the cells by 80 pM EZH2 siRNA at 48 hours.

RESULTS

Based on the flow-cytometry results, the EZH2 siRNA had no toxic effects on MOLT-4 cells. Also, the EZH2 inhibition increased the expression of DR4/5 but reduced the PRAME gene expression at the mRNA levels. Moreover, the EZH2 silencing could not change the TRAIL mRNA in the transfected cells.

CONCLUSION

Our results revealed that the down-regulation of EZH2 in MOLT-4 cells was able to affect the expression of important genes involved in the induction of resistance against TIA. Hence, we suggest that the silencing of EZH2 using RNA interference can be an effective and safe approach to help defeat the MOLT-4 cell resistance against TIA.

Anticancer Effects and Mechanisms of Action of Plumbagin: Review of Research Advances

Plumbagin (PLB), a natural naphthoquinone constituent isolated from the roots of the medicinal plant Plumbago zeylanica L., exhibited anticancer activity against a variety of cancer cell lines including breast cancer, hepatoma, leukemia, melanoma, prostate cancer, brain tumor, tongue squamous cell carcinoma, esophageal cancer, oral squamous cell carcinoma, lung cancer, kidney adenocarcinoma, cholangiocarcinoma, gastric cancer, lymphocyte carcinoma, osteosarcoma, and canine cancer. PLB played anticancer activity via many molecular mechanisms, such as targeting apoptosis, autophagy pathway, cell cycle arrest, antiangiogenesis pathway, anti-invasion, and antimetastasis pathway. Among these signaling pathways, the key regulatory genes regulated by PLB were NF-kβ, STAT3, and AKT. PLB also acted as a potent inducer of reactive oxygen species (ROS), suppressor of cellular glutathione, and novel proteasome inhibitor, causing DNA double-strand break by oxidative DNA base damage. This review comprehensively summarizes the anticancer activity and mechanism of PLB.

Analysis of the Mechanisms of Action of Naphthoquinone-Based Anti-Acute Myeloid Leukemia Chemotherapeutics

Acute myeloid leukemia (AML) is a neoplastic disorder resulting from clonal proliferation of poorly differentiated immature myeloid cells. Distinct genetic and epigenetic aberrations are key features of AML that account for its variable response to standard therapy. Irrespective of their oncogenic mutations, AML cells produce elevated levels of reactive oxygen species (ROS). They also alter expression and activity of antioxidant enzymes to promote cell proliferation and survival. Subsequently, selective targeting of redox homeostasis in a molecularly heterogeneous disease, such as AML, has been an appealing approach in the development of novel anti-leukemic chemotherapeutics. Naphthoquinones are able to undergo redox cycling and generate ROS in cancer cells, which have made them excellent candidates for testing against AML cells. In addition to inducing oxidative imbalance in AML cells, depending on their structure, naphthoquinones negatively affect other cellular apparatus causing neoplastic cell death. Here we provide an overview of the anti-AML activities of naphthoquinone derivatives, as well as analysis of their mechanism of action, including induction of reduction-oxidation imbalance, alteration in mitochondrial transmembrane potential, Bcl-2 modulation, initiation of DNA damage, and modulation of MAPK and STAT3 activity, alterations in the unfolded protein response and translocation of FOX-related transcription factors to the nucleus.

Antiproliferation for Breast Cancer Cells by Ethyl Acetate Extract of Nepenthes thorellii x (ventricosa x maxima)

Extracts from the Nepenthes plant have anti-microorganism and anti-inflammation effects. However, the anticancer effect of the Nepenthes plant is rarely reported, especially for breast cancer cells. Here, we evaluate the antitumor effects of the ethyl acetate extract of Nepenthesthorellii x (ventricosa x maxima) (EANT) against breast cancer cells. Cell viability and flow cytometric analyses were used to analyze apoptosis, oxidative stress, and DNA damage. EANT exhibits a higher antiproliferation ability to two breast cancer cell lines (MCF7 and SKBR3) as compared to normal breast cells (M10). A mechanistic study demonstrates that EANT induces apoptosis in breast cancer cells with evidence of subG1 accumulation and annexin V increment. EANT also induces glutathione (GSH) depletion, resulting in dramatic accumulations of reactive oxygen species (ROS) and mitochondrial superoxide (MitoSOX), as well as the depletion of mitochondrial membrane potential (MMP). These oxidative stresses attack DNA, respectively leading to DNA double strand breaks and oxidative DNA damage in γH2AX and 8-oxo-2′deoxyguanosine (8-oxodG) assays. Overall these findings clearly revealed that EANT induced changes were suppressed by the ROS inhibitor. In conclusion, our results have shown that the ROS-modulating natural product (EANT) has antiproliferation activity against breast cancer cells through apoptosis, oxidative stress, and DNA damage.

Cathepsin B mediated scramblase activation triggers cytotoxicity and cell cycle arrest by andrographolide to overcome cellular resistance in cisplatin resistant human hepatocellular carcinoma HepG2 cells

Andrographolide regimen in single or in combination with anticancer drugs is a promising new strategy to reverse chemoresistance in heaptocellular carcinoma. Apoptosis inducing factor (AIF) may regulate a complementary, cooperative or redundant pathway, along with caspase cascades. Despite these findings, mechanisms underlying caspase-dependent and-independent signaling pathways in andrographolide -induced apoptosis in cisplatin-resistant human hepatocellular carcinoma cell line (HepG2CR) remain unclear. Andrographolide treatment effectively reduced NF-κβ nuclear localization by modulating protein kinase A- protein phosphatase 2 A- Iκβ kinase (PKA/PP2 A/IKK) axis that in turn maintains initiator caspase8 activity. Lysosomal distribution of tBid stimulates cytosolic cathepsin B resulting accumulation of truncated-AIF with induction in scramblase mediated phosphatidylserine exposure in HepG2CR cells. Andrographolide treatment thereby switch on subG1 phase arrest by modulating cellular check points (cyclin A, B, cyclin dependent kinase-1) cueing to the apoptosis event. Collectively, this study suggested antineoplastic potential of andrographolide through PKA/PP2 A/IKK pathway in HepG2CR cells.

Emerging role of plumbagin: Cytotoxic potential and pharmaceutical relevance towards cancer therapy

Plumbagin is a naphthoquinone derived yellow crystalline phytochemical. Plumbagin has a wide range of biological effects including cytotoxicity against cancer cells both in vitro and in vivo. Due to the pleiotropic nature of plumbagin, it shows the anticancer effect by targeting several molecular mechanisms including apoptosis and autophagic pathways, cell cycle arrest, anti-angiogenic pathways, anti-invasion and anti-metastasis pathways. Among many signaling pathways the key regulatory genes regulated by plumbagin are NF-kβ, STAT3, and AKT, etc. Plumbagin is also a potent inducer of ROS, suppressor of cellular glutathione, and causes DNA strand break by oxidative DNA base damages. In vivo studies suggested that plumbagin significantly reduces the tumor weight and volume in dose-dependent manner without any side effects in tested model organisms. Another exciting aspect of plumbagin is the ability to re-sensitize the chemo and radioresistant cancer cells when used in combination or alone. Nano encapsulation of plumbagin overcomes the poor water solubility and bioavailability obstacles, enhancing the pharmaceutical relevance with better therapeutic efficacy. Moreover, plumbagin can be introduced as a future phytotherapeutic anticancer drug after fully satisfied preclinical and clinical trials.

The role of XIAP in resistance to TNF-related apoptosis-inducing ligand (TRAIL) in Leukemia

The treatment for leukemic malignancies remains a challenge despite the wide use of conventional chemotherapies. Therefore, new therapeutic approaches are highly demanded. TNF-related apoptosis-inducing ligand (TRAIL) represents a targeted therapy against cancer because it induces apoptosis only in tumor cells. TRAIL is currently under investigation for the treatment of leukemia. Preclinical studies evaluated the potential therapeutic efficacy of TRAIL on cell lines and clinical samples and showed promising results. However, like most anti-cancer drugs, resistance to TRAIL-induced apoptosis may limit its clinical efficacy. It is critical to understand the molecular mechanisms of TRAIL. Therefore, rational therapeutic drug combinations for clinical trials of TRAIL-based therapies might be achieved. In a variety of leukemic cells, overexpression of X-linked inhibitor of apoptosis protein (XIAP), a negative regulator of apoptosis pathway, has been discovered. Implication of XIAP in the ineffective induction of cell death by TRAIL in leukemia has been explored in several resistant cell lines. XIAP inhibitors restored TRAIL sensitivity in resistant cells and primary leukemic blasts. Moreover, TRAIL resistance in leukemic cells could be overcome by the effects of several anti-leukemic agents via the mechanisms of XIAP downregulation. Here, we discuss targeting XIAP, a strategy to restore TRAIL sensitivity in leukemia to acquire more insights into the mechanisms of TRAIL resistance. The concluding remarks may lead to identify putative ways to resensitize tumors.

Arsenic trioxide and sorafenib combination therapy for human hepatocellular carcinoma functions via up-regulation of TNF-related apoptosis-inducing ligand

The survival benefits of sorafenib treatment for patients with hepatocellular carcinoma (HCC) are limited due to drug resistance and side effects. Therefore, combinations of sorafenib with other low toxicity drugs, including arsenic trioxide (As₂O₃) require investigation. The present study aimed to evaluate the potency of apoptosis-induction by As₂O₃/sorafenib treatment in HCC cell lines, Huh7, 97H and freshly-isolated HCC cells, and also to elucidate the underlying mechanism. A total of 10 patients with HCC were enrolled in the present study. Freshly-isolated HCC cells were purified from HCC tissues collected at surgery. HCC-cell apoptosis was measured by flow cytometry using proprium iodide/Annexin-V staining. The impacts of As₂O₃ and/or sorafenib on Huh7, 97H and fresh-isolated HCC-cell proliferation were evaluated by Cell Counting Kit-8 assay. The expression of TNF-related apoptosis-inducing ligand (TRAIL) was determined by reverse transcription-quantitative polymerase chain reaction and western blotting. The downregulation of TRAIL protein expression was achieved using small interfering RNA. The combination of As₂O₃ and sorafenib had anti-proliferative and pro-apoptotic effects in the liver cancer cell line, Huh7, via increased expression of TRAIL, but not in 97H cells. TRAIL-knockdown increased the drug-resistance of Huh7 cells. Freshly-isolated HCC cells were more sensitive to the As₂O₃ and sorafenib combination than the single drug treatments. Overall, the combination of As₂O₃ and sorafenib demonstrated potent anti-tumor activity in Huh7 and freshly-isolated HCC cells via a TRAIL-dependent pathway. This may be a potential therapeutic approach for advanced HCC treatment.