Piperlongumine Suppresses Growth and Sensitizes Pancreatic Tumors to Gemcitabine in a Xenograft Mouse Model by Modulating the NF-kappa B Pathway

Delivery of piperlongumine via hyaluronic acid/phenylboronic acid-mediated dual targetable polymersome for enhanced anticancer functionality against pancreatic tumor

Pancreatic cancer cells highly resistance to conventional chemo drugs, resulting low survival rates. The aim of the study was to design and develop dual targeting polymersomes (DTPS) loaded with phyto alkaloid agent i.e., piperlongumine (PL) for effective pancreatic cancer treatment. Here, hyaluronic acid (HA) was functionalized with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene glycol)-2000] (DSPEPEG-NH2), poly(ethylene glycol) bis (amine) (PEG), and phenylboronic acid (PBA) moieties. The designed DTPS could selectively recognize CD44/sialic acid (SA) and deliver PL to MIA PaCa-2 pancreatic cancer cells, facilitated via HA-CD44 and PBA-SA interactions. Drug release and stability results implied sustained PL release profile and pH sensitivity. DTPS could be more efficiently bound with SA than other sugars based on fluorescence spectroscopy. The anticancer efficacy of designed polymersomes was tested with H6C7 normal pancreas cells and SA/CD44-overexpressed MIA PaCa-2 pancreatic cancer cells. DTPS showed both SA and CD44-mediated higher cellular uptake while single-targeted polymersomes showed CD44-mediated cellular uptake. The PL-loaded DTPS efficiently uptake by MIA PaCa-2 cancer cells, causing up to 80 % cell growth inhibition, reduced cell spheroids volume and increased dead cells by 58.3 %. These results indicate that the newly developed DTPS can effectively serve as a pH-responsive drug delivery system for efficient treatment of cancer.

Inhibition of the thioredoxin system for radiosensitization therapy of cancer

Radiotherapy (RT) stands as a cornerstone in the clinical armamentarium against various cancers due to its proven efficacy. However, the intrinsic radiation resistance exhibited by cancer cells, coupled with the adverse effects of RT on normal tissues, often compromises its therapeutic potential and leads to unwanted side effects. This comprehensive review aims to consolidate our understanding of how radiosensitizers inhibit the thioredoxin (Trx) system in cellular contexts. Notable radiosensitizers, including gold nanoparticles (GNPs), gold triethylphosphine cyanide ([Au(SCN) (PEt3)]), auranofin, ceria nanoparticles (CONPs), curcumin and its derivatives, piperlongamide, indolequinone derivatives, micheliolide, motexafin gadolinium, and ethane selenide selenidazole derivatives (SeDs), are meticulously elucidated in terms of their applications in radiotherapy. In this review, the sensitization mechanisms and the current research progress of these radiosensitizers are discussed in detail, with the overall aim of providing valuable insights for the judicious application of Trx system inhibitors in the field of cancer radiosensitization therapy.

Phytochemicals for the prevention and treatment of pancreatic cancer: Current progress and future prospects

Pancreatic cancer is the third leading cause of cancer-related deaths in the United States, owing to its aggressive nature and suboptimal treatment options, emphasizing the need for novel therapeutic approaches. Emerging studies have exhibited promising results regarding the therapeutic utility of plant-derived compounds (phytochemicals) in pancreatic cancer. The purpose of this review is to evaluate the potential of phytochemicals in the treatment and prevention of pancreatic cancer. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses was applied to collect articles for this review. Scholarly databases, including PubMed, Scopus and ScienceDirect, were queried for relevant studies using the following keywords: phytochemicals, phenolics, terpenoids, alkaloids, sulfur-containing compounds, in vitro, in vivo, clinical studies, pancreatic cancer, tumour, treatment and prevention. Aggregate results pooled from qualified studies indicate phytochemicals can inhibit pancreatic cancer cell growth or decrease tumour size and volume in animal models. These effects have been attributed to various mechanisms, such as increasing proapoptotic factors, decreasing antiapoptotic factors, or inducing cell death and cell cycle arrest. Notable signalling pathways modulated by phytochemicals include the rat sarcoma/mitogen activated protein kinase, wingless-related integration site/β-catenin and phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin signal transduction pathways. Clinically, phytochemicals have been found to increase survival while being well-tolerated and safe, though research is scarce. While these promising results have produced great interest in this field, further in-depth studies are required to characterize the anticancer activities of phytochemicals before they can be utilized to prevent or treat pancreatic cancer in clinical practice.

Umbelliprenin induces autophagy and apoptosis while inhibits cancer cell stemness in pancreatic cancer cells

BACKGROUND

Umbelliprenin is a sesquiterpene coumarin isolated from Artemisia absinthium L. and shows antitumor effects in various cancers by inducing apoptosis. However, the antitumor effect of umbelliprenin in human pancreatic cancer has not been clarified.

METHODS

The antitumor effects were determined by MTT and AnnexinV/PI double staining assay in vitro and xenograft mice in vivo. Autophagy was determined via immunofluorescence analysis. Apoptotic or autophagic related proteins were measured by immunoblotting. The pancreatic cancer cell stemness were determined by mammosphere formation and ALDEFLUOR assay.

RESULTS

It revealed that umbelliprenin inhibited pancreatic cancer cell proliferation in vitro and pancreatic cancer tumor growth in vivo. Moreover, umbelliprenin induced pancreatic cancer cell BxPC3 apoptosis and autophagy as evidenced by upregulated apoptosis and autophagy- related protein expression (p < 0.01). Blocking autophagy by 3-MA or Atg7 knockout enhanced umbelliprenin-induced apoptosis (p < 0.05). Umbelliprenin also reduced pancreatic cancer cell stemness by reducing Oct4, Nanog, and Sox2 mRNA levels (p < 0.01). Mechanistically, umbelliprenin greatly inhibited Akt/mTOR and Notch1 signal pathway.

CONCLUSION

Umbelliprenin may be a novel therapeutic approach for pancreatic cancer treatment.

Therapeutic Approaches in Pancreatic Cancer: Recent Updates

Cancer is a significant challenge for effective treatment due to its complex mechanism, different progressing stages, and lack of adequate procedures for screening and identification. Pancreatic cancer is typically identified in its advanced progression phase with a low survival of ~5 years. Among cancers, pancreatic cancer is also considered a high mortality-causing casualty over other accidental or disease-based mortality, and it is ranked seventh among all mortality-associated cancers globally. Henceforth, developing diagnostic procedures for its early detection, understanding pancreatic cancer-linked mechanisms, and various therapeutic strategies are crucial. This review describes the recent development in pancreatic cancer progression, mechanisms, and therapeutic approaches, including molecular techniques and biomedicines for effectively treating cancer.

Clinical Efficacy and Safety of Traditional Medicine Preparations Combined With Chemotherapy for Advanced Pancreatic Cancer: A Systematic Review and Meta-Analysis

Background

Traditional medicine preparations (TMPs) combined with chemotherapy is widely used for patients with advanced pancreatic cancer (APC); however, its efficacy and safety are still unclear. The purpose of this meta-analysis was to evaluate the clinical efficacy and safety of TMPs combined with chemotherapy for the treatment of APC.

Methods

A systematic search of eight electronic databases for randomized controlled trials (RCTs) was conducted from inception to October 15, 2021. Tumor response was identified as primary outcome, whereas quality of life (QoL), cancer biomarkers, and adverse drug reactions (ADRs) were identified as secondary outcomes. Quality of the evidence for each outcome was evaluated by GRADE profiler.

Results

In total, 31 RCTs involving 1,989 individuals were included. This meta-analysis showed that TMPs combined with chemotherapy significantly improved the objective response rate (ORR) (RR=1.64, 95% CI [1.43 to 1.88], p <0.00001), disease control rate (DCR) (RR=1.29, 95% CI [1.21 to 1.38], p <0.00001), and QoL (continuous data: SMD=0.81, 95% CI [0.44 to 1.18], p <0.0001, dichotomous data: RR=1.44, 95% CI [1.22 to 1.70], p<0.0001), compared to those with chemotherapy alone. In addition, the combined treatment group also had lower levels of CA19-9 (SMD=-0.46, 95% CI [-0.90 to -0.02], p=0.04) and CEA (SMD=-0.55, 95% CI [-0.93 to -0.17], p=0.004). Moreover, TMPs reduced the ADRs during chemotherapy.

Conclusion

This systematic review suggests that TMPs combined with chemotherapy might be a potential option to enhance therapeutic effects and reduce ADRs during the treatment of APC. However, more high-quality randomized controlled trials with more participants are needed.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=209825, identifier PROSPERO Number: CRD42021264938.

Modulation of TLR/NF-κB/NLRP Signaling by Bioactive Phytocompounds: A Promising Strategy to Augment Cancer Chemotherapy and Immunotherapy

Background

Tumors often progress to a more aggressive phenotype to resist drugs. Multiple dysregulated pathways are behind this tumor behavior which is known as cancer chemoresistance. Thus, there is an emerging need to discover pivotal signaling pathways involved in the resistance to chemotherapeutic agents and cancer immunotherapy. Reports indicate the critical role of the toll-like receptor (TLR)/nuclear factor-κB (NF-κB)/Nod-like receptor pyrin domain-containing (NLRP) pathway in cancer initiation, progression, and development. Therefore, targeting TLR/NF-κB/NLRP signaling is a promising strategy to augment cancer chemotherapy and immunotherapy and to combat chemoresistance. Considering the potential of phytochemicals in the regulation of multiple dysregulated pathways during cancer initiation, promotion, and progression, such compounds could be suitable candidates against cancer chemoresistance.

Objectives

This is the first comprehensive and systematic review regarding the role of phytochemicals in the mitigation of chemoresistance by regulating the TLR/NF-κB/NLRP signaling pathway in chemotherapy and immunotherapy.

Methods

A comprehensive and systematic review was designed based on Web of Science, PubMed, Scopus, and Cochrane electronic databases. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed to include papers on TLR/NF-κB/NLRP and chemotherapy/immunotherapy/chemoresistance by phytochemicals.

Results

Phytochemicals are promising multi-targeting candidates against the TLR/NF-κB/NLRP signaling pathway and interconnected mediators. Employing phenolic compounds, alkaloids, terpenoids, and sulfur compounds could be a promising strategy for managing cancer chemoresistance through the modulation of the TLR/NF-κB/NLRP signaling pathway. Novel delivery systems of phytochemicals in cancer chemotherapy/immunotherapy are also highlighted.

Conclusion

Targeting TLR/NF-κB/NLRP signaling with bioactive phytocompounds reverses chemoresistance and improves the outcome for chemotherapy and immunotherapy in both preclinical and clinical stages.

Piperlongumine induces ROS mediated apoptosis by transcriptional regulation of SMAD4/P21/P53 genes and synergizes with doxorubicin in osteosarcoma cells

Piperlongumine is a herbal drug, with well-known anti-microbial and anti-neoplastic properties. The anti-carcinogenic potential of piperlongumine has been extensively explored for breast, colorectal, lungs, pancreatic, prostate, and oral carcinoma. However, a few numbers of studies are available on its bio-activity in osteosarcoma. Therefore, the present study aimed at exploring the therapeutic potential and possible mechanisms of action of piperlongumine in three human osteosarcoma cell lines in-vitro. The cytotoxicity of piperlongumine was determined by MTT assay, which shows dose and time-dependent inhibition of MG-63, 143B and KHOS/NP cells. Piperlongumine arrest the cells in G2/M phase of cell cycle and increases reactive oxygen species production, which possibly leads to lethal oxidative stress and apoptosis. Piperlongumine treatment significantly upregulated the expression of genes BAX, P21, P53, and SMAD4; while the BCL-2, SURVIVIN, TNFA, and NFKB genes expression was found down-regulated. Furthermore, piperlongumine exposure inhibited the migration of osteosarcoma cells as the expression of migration marker genes CDH2, CTNNB1, FN1, and TWIST were found to be down-regulated. The drug combination studies show the synergistic effect of piperlongumine with the conventional chemotherapeutic drug doxorubicin in osteosarcoma cells. Taken together, the above results suggest that PL displays anticancer properties against osteosarcoma and can be used as a therapeutic agent for osteosarcoma treatment in clinical settings.

A Derivative of Piperlongumine and Ligustrazine as a Potential Thioredoxin Reductase Inhibitor in Drug-Resistant Hepatocellular Carcinoma

The natural products piperlongumine (1) and ligustrazine (2) have been reported to exert antiproliferative effects against various types of cancer cells by up-regulating the level of reactive oxidative species (ROS). However, the moderate activities of 1 and 2 limit their application. To improve their potential antitumor activity, novel piperlongumine/ligustrazine derivatives were designed and prepared, and their potential pharmacological effects were determined in vitro and in vivo. Among the derivatives obtained, 11 exerted more prominent inhibitory activities against proliferation of drug-sensitive/-resistant cancer cells with lower IC50 values than 1. Particularly, the IC50 value of 11 against drug-resistant Bel-7402/5-FU cells was 0.9 μM, which was about 9-fold better than that of 1 (IC50 value of 8.4 μM). Mechanistic studies showed that 11 demonstrated thioredoxin reductase (TrxR) inhibitory activity, increase of ROS levels, decrease of mitochondrial transmembrane potential levels, and occurrence of DNA damage and autophagy, in a dose-dependent manner, via regulation of DNA damage protein H2AX and autophagy-associated proteins LC3, beclin-1, and p62 in drug-resistant Bel-7402/5-FU cells. Finally, compound 11 at 5 mg/kg displayed potent antitumor activity in vivo with tumor suppression of 76% (w/w). Taken together, compound 11 may represent a promising candidate drug for the chemotherapy of drug-resistant hepatocellular carcinoma and warrant more intensive study.

Identification of Novel Drug Candidate for Epithelial Ovarian Cancer via In Silico Investigation and In Vitro Validation

Epithelial ovarian cancer (EOC) has a poor prognosis and high mortality rate; patients are easy to relapse with standard therapies. So, there is an urgent need to develop novel drugs. In this study, differentially expressed genes (DEGs) of EOC were identified in The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Enrichment and protein–protein interaction (PPI) analyses were performed. The drug candidate which has the possibility to treat EOC was predicted by Connectivity Map (CMAP) databases. Moreover, molecular docking was selected to calculate the binding affinity between drug candidate and hub genes. The cytotoxicity of drug candidates was assessed by MTT and colony formation analysis, the proteins coded by hub genes were detected by Western blots, and apoptosis analysis was evaluated by flow cytometry. Finally, 296 overlapping DEGs (|log 2 fold change|>1; q-value <0.05), which were principally involved in the cell cycle (p < 0.05), and cyclin-dependent kinase 1 (CDK1) were screened as the significant hub gene from the PPI network. Furthermore, the 21 drugs were extracted from CMAPs; among them, piperlongumine (PL) showed a lower CMAP score (-0.80, -62.92) and was regarded as the drug candidate. Furthermore, molecular docking results between PL and CDK1 with a docking score of –8.121 kcal/mol were close to the known CDK1 inhibitor (–8.24 kcal/mol). Additionally, in vitro experiments showed that PL inhibited proliferation and induced apoptosis via targeting CDK1 in EOC SKOV3 cells. Our results reveal that PL may be a novel drug candidate for EOC by inhibiting cell cycle.

Natural Products for Pancreatic Cancer Treatment: From Traditional Medicine to Modern Drug Discovery

Pancreatic cancer, the seventh most lethal cancer around the world, is considered complicated cancer due to poor prognosis and difficulty in treatment. Despite all the conventional treatments, including surgical therapy and chemotherapy, the mortality rate is still high. Therefore, the possibility of using natural products for pancreatic cancer is increasing. In this study, 68 natural products that have anti-pancreatic cancer effects reported within five years were reviewed. The mechanisms of anti-cancer effects were divided into four types: apoptosis, anti-metastasis, anti-angiogenesis, and anti-resistance. Most of the studies were conducted for natural products that induce apoptosis in pancreatic cancer. Among them, plant extracts such as Eucalyptus microcorys account for the major portion. Some natural products, including Moringa, Coix seed, etc., showed multi-functional properties. Natural products could be beneficial candidates for treating pancreatic cancer.

The promising potential of piperlongumine as an emerging therapeutics for cancer

In spite of the immense advancement in the diagnostic and treatment modalities, cancer continues to be one of the leading causes of mortality across the globe, responsible for the death of around 10 million patients every year. The foremost challenges faced in the treatment of this disease are chemoresistance, adverse effects of the drugs, and the high cost of treatment. Though scientific studies over the past few decades have foreseen and are focusing on the cancer-preventive and therapeutic potential of natural products and their underlying mechanism of action, many more of these agents are not still explored. Piperlongumine (PL), or piplartine, is one such alkaloid isolated from Piper longum Linn. which is shown to be safe and has significant potential in the prevention and therapy of cancer. Numerous shreds of evidence have established the ability of this alkaloid and its analogs and nanoformulations in modulating various complex molecular pathways such as phosphatidylinositol-3-kinase/protein kinase B /mammalian target of rapamycin, nuclear factor kappa-B, Janus kinases/signal transducer and activator of transcription 3, etc. and inhibit different hallmarks of cancer such as cell survival, proliferation, invasion, angiogenesis, epithelial-mesenchymal-transition, metastases, etc. In addition, PL was also shown to inhibit radioresistance and chemoresistance and sensitize the cancer cells to the standard chemotherapeutic agents. Therefore, this compound has high potential as a drug candidate for the prevention and treatment of different cancers. The current review briefly reiterates the anti-cancer properties of PL against different types of cancer, which permits further investigation by conducting clinical studies.

Piperlongumine inhibits the progression of osteosarcoma by downregulating the SOCS3/JAK2/STAT3 pathway via miR-30d-5p

AIMS

The present study evaluated the functions of Piperlongumine (PL) in osteosarcoma (OS) cell growth and metastasis both in vitro and in vivo.

MAIN METHODS

MTT assay was conducted to test the cytotoxic effects of PL on the human osteoblasts line HFOB1.19 and the human normal chondrocyte line C28/I2T. FITC-Annexin V and propidium iodide (PI) were used to examine cell apoptosis. The migration, invasion and relative epithelial-mesenchymal transition were examined by Transwell assay and Western blotting. Reverse transcription-quantitative PCR (RT-qPCR) was performed to analyze the cytokine signaling 3 (SOCS3) mRNA expression. TargetScan database was used to predict the target of SOCS3. The binding association between miR-30d-5p and SOCS3 in U2OS and MG63 cells was evaluated by the dual-luciferase reporter assay. A xenograft model was constructed to evaluate the effect of PL on OS cell growth in vivo.

KEY FINDINGS

The results revealed that PL inhibited the growth, migration, invasion, epithelial-mesenchymal transition, and promoted the apoptosis of OS cells dose-dependently. In addition, PL upregulated the protein levels of suppressor of SOCS3, while it inactivated the JAK2/STAT3 pathway, which was accompanied by a decreased level of microRNA (miR)-30d-5p. Furthermore, SOCS3was confirmed as a novel target of miR-30d-5p. Overexpression of miR-30d-5p not only led to decreased expression of SOCS3, but also dampened the antitumor effect of PL on OS.

SIGNIFICANCE

The present data demonstrated that PL inhibited the progression of OS via downregulation of the SOCS3-mediated JAK2/STAT3 pathway by inhibiting miR-30d-5p.

Protective Effect of Piplartine against LPS-Induced Sepsis through Attenuating the MAPKs/NF-κB Signaling Pathway and NLRP3 Inflammasome Activation

Piplartine (or Piperlongumine) is a natural alkaloid isolated from Piper longum L., which has been proposed to exhibit various biological properties such as anti-inflammatory effects; however, the effect of piplartine on sepsis has not been examined. This study was performed to examine the anti-inflammatory activities of piplartine in vitro, ex vivo and in vivo using murine J774A.1 macrophage cell line, peritoneal macrophages, bone marrow-derived macrophages and an animal sepsis model. The results demonstrated that piplartine suppresses iNOS and COX-2 expression, reduces PGE₂, TNF-α and IL-6 production, decreases the phosphorylation of MAPKs and NF-κB and attenuates NF-κB activity by LPS-activated macrophages. Piplartine also inhibits IL-1β production and suppresses NLRP3 inflammasome activation by LPS/ATP- and LPS/nigericin-activated macrophages. Moreover, piplartine reduces the production of nitric oxide (NO) and TNF-α, IL-6 and IL-1β, decreases LPS-induced tissue damage, attenuates infiltration of inflammatory cells and enhances the survival rate. Collectively, these results demonstrate piplartine exhibits anti-inflammatory activities in LPS-induced inflammation and sepsis and suggest that piplartine might have benefits for sepsis treatment.

Piperlongumine promotes death of retinoblastoma cancer cells

Retinoblastoma is the most common pediatric intraocular malignant tumor. While retinoblastoma initiation is triggered by the inactivation of both alleles of the retinoblastoma tumor suppressor gene (RB1) in the developing retina, tumor progression requires additional epigenetic changes, retinoblastoma genomes being quite stable. Although the management of RB has recently improved, new therapeutic agents are necessary to improve the treatment of advanced forms of retinoblastoma.

In this report, we analyzed the pro-death effect of piperlongumine (PL), a natural compound isolated from Piper longum L., on two human retinoblastoma cell lines, WERI-Rb and Y79. The effects of PL on cell proliferation, cell death and cell cycle were investigated. PL effectively inhibited cell growth, impacted the cell cycle by decreasing the level of cyclins and CDK1 and increasing CDKN1A and triggered a caspase-3 independant cell death process in which reactive oxygen species (ROS) production is a major player. Indeed, PL toxicity in retinoblastoma cell lines was inhibited by a ROS scavenger N-acetyl-l-cysteine (NAC) treatment. These findings suggest that PL reduces tumor growth and induces cell death by regulating the cell cycle.

Piperlongumine targets NF-κB and its downstream signaling pathways to suppress tumor growth and metastatic potential in experimental colon cancer

NF-κB is the principle transcription factor and plays the central role in orchestrating chronic inflammation by regulating levels of cytokines, chemokines and growth factors. Piperlongumine (PL), a major alkaloid in the fruit of Piper longum Linn. has gained worldwide attention for its anticancer properties, however, its mechanism of action in the chemoprevention of colon cancer has not been investigated yet. Therefore, the present study was designed to elucidate the underlying molecular mechanism of PL in preventing DMH/DSS induced experimental colon cancer in mice. In the current study well established DMH/DSS induced experimental colon cancer mouse model was used to demonstrate the chemopreventive potential of PL. The expression of NF-κB and its downstream target proteins was evaluated mainly through western blotting. In addition, CAM assay, immunohistochemical staining and gelatin zymography was used to show anti-angiogenic and anti-invasive potential of PL. Additionally, important tumor biomarkers such as TSA, LASA, LDH and IL-6 levels were also estimated. The results of current study showed that PL was capable to inhibit NF-κB activation as well as its nuclear translocation. PL administration to DMH/DSS treated mice also inhibited the NF-κB downstream signaling cascades such as including COX-2 pathway, JAK/STAT pathway, β-catenin, Notch signaling pathway, angiogenesis and epithelial to mesenchymal transition pathway. The findings of the present study have claimed PL as promising chemopreventive agent for colon cancer with pleiotropic action. The current study emphasizes that regular consumption of PL can be an effective approach in the prevention of colon cancer in humans.

Effect of nanoemulsion modification with chitosan and sodium alginate on the topical delivery and efficacy of the cytotoxic agent piplartine in 2D and 3D skin cancer models

Due to the limited options for topical management of skin cancer, this study aimed at developing and evaluating nanoemulsions (NE) for topical delivery of the cytotoxic agent piplartine (piperlongumine). NEs were modified with chitosan or sodium alginate, and the effects on the physicochemical properties, piplartine delivery and formulation efficacy were evaluated. The nanoemulsion droplets displayed similar size (96-112 nm), but opposite charge; the polysaccharides improved piplartine penetration into and across the skin (1.3-1.9-fold) in a similar manner, increasing the ratio "drug in the skin/receptor phase" by 1.4-1.5-fold compared to the plain NE and highlighting their relevance for cutaneous localization. Oleic acid addition to the chitosan-containing NE further increased drug penetration (~1.9-2.0-fold), as did increases in drug content from 0.5 to 1%. The cytotoxicity of piplartine was ~2.8-fold higher when the drug was incorporated in the chitosan-containing NE compared to its solution (IC50 = 14.6 μM) against melanoma cells. The effects of this nanocarrier on 3D melanoma tissues were concentration-related; at 1%, piplartine elicited marked epidermis destruction. These results support the potential applicability of the chitosan-modified nanoemulsion containing piplartine as a new strategy for local management of skin cancer.

Piperlongumine induces ROS mediated cell death and synergizes paclitaxel in human intestinal cancer cells

Piperlongumine (PL), a herbal drug extracted from long pepper (Piper longum L), is known for its anti-inflammatory and anti-cancer properties. Although, its anti-cancer potential has been evaluated in cancer models like breast, pancreatic, gastric, hepatocellular and lung carcinoma, there is no report on its bio-activity evaluation in intestinal cancers. Here, we report the anti-neoplastic potential of PL against human intestinal carcinoma in-vitro and its possible mechanisms of action. Cytotoxicity studies demonstrate that PL inhibits cell proliferation of INT-407 and HCT-116 cells in a concentration and time-dependent manner. Also, PL elevated the levels of intracellular reactive oxygen species, which may lead to lethal oxidative stress, mitochondrial dysfunction, and nuclear fragmentation. Remarkably, P53, P21, BAX, and SMAD4 were significantly upregulated after PL treatment whereas; BCL2 and SURVIVIN were down-regulated. Moreover, the combination study also shows the synergistic effect of PL with the current chemotherapeutic drug paclitaxel. These findings suggest that PL possesses anti-neoplastic properties in intestinal cancer cells.

Deoxyelephantopin induces apoptosis via oxidative stress and enhances gemcitabine sensitivity in vitro and in vivo through targeting the NF-κB signaling pathway in pancreatic cancer

Pancreatic cancer is a highly invasive malignant tumor of the digestive system with an unfavorable prognosis worldwide. This trait is thought to be largely attributed to chemoresistance. Chemotherapy is the only hope for patients with advanced pancreatic cancer. Therefore, seeking new effective chemotherapy drugs has become an urgent need. The purpose of our study was to explore whether deoxyelephantopin (DET), a sesquiterpene lactone, has a potential antitumor effect in pancreatic cancer. Additionally, the antitumor effects of DET alone or in combination with gemcitabine (GEM) and the potential mechanism of this combination were revealed. In vitro experiments showed that DET suppressed the proliferation, invasion and metastasis of pancreatic cancer cells, induced cell apoptosis via oxidative stress, and enhanced GEM sensitivity by inhibiting the NF-κB signaling pathway. Beyond that, in vivo experiments showed that DET not only inhibited pancreatic tumor growth and metastasis but also amplified the antitumor capacity of GEM, which was related to the downregulation of NF-κB and its downstream gene products. In summary, it is possible that DET could be developed as a single agent or combined with conventional chemotherapy drugs to improve the treatment of pancreatic cancer.

Resibufogenin suppresses growth and metastasis through inducing caspase-1-dependent pyroptosis via ROS-mediated NF-κB suppression in non-small cell lung cancer

The purpose of this study is to explore the antitumor properties of resibufogenin (RB) in non-small cell lung cancer (NSCLC) and elucidate its underlying mechanism. A549 and H520 cells were treated with various concentrations of RB with or without NLRP3 inhibitor (MCC950), caspase-1 inhibitor (VX765), or N-acetyl-l-cysteine (an ROS scavenger). Cell counting kit-8 and colony formation assays were conducted to determine cell viability. Cell invasion was detected by using the transwell assay. The release of lactate dehydrogenase (LDH) was determined by the LDH detection assay. The protein expression levels of related genes were measured by western blotting and immunohistochemistry. The reactive oxygen species (ROS) level was detected by using a 2,7-dichlorodihydrofluorescein diacetate ROS Assay Kit. The in vivo effects of RB were evaluated in a xenograft mouse model. RB treatment reduced cell viability and invasion in a dose-dependent manner. Furthermore, RB also enhanced pyroptosis levels in A549 and H520 cells, as indicated by the increased release of LDH and pyroptosis-related proteins. Interestingly, we also found that the antiproliferative and antimetastatic effects of RB were alleviated by the blockade of pyroptosis using NLRP3 inhibitor MCC950. Further study demonstrated that RB induced pyroptosis in a caspase-1-dependent manner, as evidenced by the finding that VX765 effectively reversed the effects of RB on A549 and H520 cells. We also found that RB could trigger caspase-1-dependent pyroptosis through ROS-mediated NF-κB suppression. In summary, our findings provide a potential antitumor agent and a novel insight into the mechanism of RB treatment of NSCLC.

Piperlongumine, a potent anticancer phytotherapeutic: Perspectives on contemporary status and future possibilities as an anticancer agent

Piperlongumine, a white to beige biologically active alkaloid/amide phytochemical, has high pharmacological relevance as an anticancer agent. Piperlongumine has several biological activities, including selective cytotoxicity against multiple cancer cells of different origins at a preclinical level. Several preclinical studies have documented the anticancer potential of piperlongumine through its targeting of multiple molecular mechanisms, such as cell cycle arrest, anti-angiogenesis, anti- invasive and anti-metastasis pathways, autophagy pathways, and intrinsic apoptotic pathways in vitro and in vivo. Mechanistically, piperlongumine inhibits cancer growth by resulting in the accumulation of intracellular reactive oxygen species, decreasing glutathione and chromosomal damage, or modulating key regulatory proteins, including PI3K, AKT, mTOR, NF-kβ, STATs, and cyclin D1. Furthermore, combined treatment with piperlongumine potentiates the anticancer activity of conventional chemotherapeutics and overcomes resistance to chemo- and radio- therapy. Nanoformulation of piperlongumine has been associated with increased aqueous solubility and bioavailability and lower toxicity, thus enhancing therapeutic efficacy in both preclinical and clinical settings. The current review highlights anticancer studies on the occurrence, chemical properties, chemopreventive mechanisms, toxicity, bioavailability, and pharmaceutical relevance of piperlongumine in vitro and in vivo.

Small Molecule Inhibitor C188-9 Synergistically Enhances the Demethylated Activity of Low-Dose 5-Aza-2'-Deoxycytidine Against Pancreatic Cancer

Aberrant DNA methylation, especially hypermethylation of tumor suppressor genes, has been associated with many cancers' progression. 5-Aza-2′-deoxycytidine (DAC) can reverse hypermethylation-induced gene silencing via regulating DNA methyltransferases (DNMTs) activity, In addition, low-dose of DAC was proved to exert durable antitumor effects against solid tumor cells. Nevertheless, no clinical effect of DAC has been made when fighting against pancreatic cancer. Hence, it is necessary to raise a novel therapeutic strategy that further enhance the efficacy of DAC but not increase side effect, which impede the utilization of DAC. In the present study, we have discovered that C188-9, a novel signal transduction activator of transcription (STAT) inhibitor, could improve the antitumor effects of low-dose DAC in vivo and in vitro. Further study demonstrated that such improvement was attributed to re-expression of Ras association domain family member 1A (RASSF1A), a well-known tumor suppressor gene. Bisulfite sequencing PCR (BSP) assay showed that C188-9 combined with DAC treatment could significantly reverse the hypermethylation status of RASSF1A promoter, which indicated that C188-9 could enhance the demethylation efficacy of DAC. Our data demonstrated that DNA methyltransferase 1 (DNMT1) was the underlying mechanism that C188-9 regulates the demethylation efficacy of DAC. Overall, these findings provide a novel therapeutic strategy combining low-dose DAC and C188-9 to improve therapeutic efficacy by inhibiting DNMT1-inducing promoter methylation.

Molecular Mechanisms of Anticancer Activities of Puerarin

Medicinal plants are a vital source of natural products (NPs) that can cure cancer through modulation of different pathways, including oxidative stress, extrinsic and intrinsic apoptosis, cell cycle, inflammation, NF-kB, PI3K/AKT/mTOR, AMPK (JNK), MEK/ERK (Raf)-MEK-ERK and autophagy. Puerarin (Pue), an important NP belonging to the isoflavone glycoside group, is derived from Pueraria lobata (Willd.) Ohwi, Pueraria thomsonii Benth, and Pueraria tuberosa (Willd.). This NP was approved by the Chinese Ministry of Health for the treatment of different diseases in 1993, but it was also later reported to exhibit anticancer activity. Pue causes cancer cells death through modulation of different mechanisms including oxidative stress, intrinsic and extrinsic, Survivin and XIAP, PI3K/AKT/mTOR, Ras-Raf-MEK-ERK, JNK, cell cycle, AMPK, NF-kB, inflammation and autophagy pathways. Therefore, this review compiles for the first time the studies about the anticancer mechanism of Pue and provides comprehensive information about the anticancer effects of Pue. This review may serve as a basis for future research and clinical treatment.

Two Natural Alkaloids Synergistically Induce Apoptosis in Breast Cancer Cells by Inhibiting STAT3 Activation

Breast cancer has become a worldwide threat, and chemotherapy remains a routine treatment. Patients are forced to receive continuous chemotherapy and suffer from severe side effects and poor prognosis. Natural alkaloids, such as piperine (PP) and piperlongumine (PL), are expected to become a new strategy against breast cancer due to their reliable anticancer potential. In the present study, cell viability, flow cytometry, and Western blot assays were performed to evaluate the suppression effect of PP and PL, alone or in combination. Data showed that PP and PL synergistically inhibited breast cancer cells proliferation at lower doses, while only weak killing effect was observed in normal breast cells, indicating a good selectivity. Furthermore, apoptosis and STAT3 signaling pathway-associated protein levels were analyzed. We demonstrated that PP and PL in combination inhibit STAT3 phosphorylation and regulate downstream molecules to induce apoptosis in breast cancer cells. Taken together, these results revealed that inactivation of STAT3 was a novel mechanism with treatment of PP and PL, suggesting that combination application of natural alkaloids may be a potential strategy for prevention and therapy of breast cancer.

Piperlongumine analogue L50377 induces pyroptosis via ROS mediated NF-κB suppression in non-small-cell lung cancer

Natural products with potent activity and less toxicity provide major sources for development of novel anti-cancer drugs. Herein, we evaluated the effects and the underlying mechanisms of a novel piperlongumine (PL) analogue L50377 on non-small-cell lung cancer (NSCLC) cells. The results revealed that L50377 displayed greater potentials of suppressing cell growth than PL. In addition, L50377 promoted cell apoptosis and pyroptosis via stimulating reactive oxygen species (ROS) generation in NSCLC cells. More interestingly, ROS mediated NF-κB suppression might be implicated in the mechanisms of L50377-induced pyroptosis in NSCLC cells. Taken together, our results suggested that L50377 served as a novel chemical agent might have great potentials for NSCLC treatment.

Piperlongumine Induces Apoptosis and Synergizes with Doxorubicin by Inhibiting the JAK2-STAT3 Pathway in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) lacks major effective target molecules and chemotherapy remains the current main treatment. However, traditional chemotherapy drugs, such as doxorubicin (DOX), cause serious side effects and have a poor prognosis. Piperlongumine (PL), a natural alkaloid, has showed selective anticancer effects and is expected to become a new strategy against TNBC. In our research, cell viability, colony formation, flow cytometry, Western blot, and tumor xenograft model assays were established to evaluate the suppression effect of PL and DOX alone and in combination. Data showed that PL could effectively inhibit cell growth and induce apoptosis in two TNBC cell lines. We also demonstrated for the first time that the combination treatment of PL and DOX synergistically inhibited cell growth and induced apoptosis in TNBC cells. The suppression of STAT3 activation was indicated to be a mechanism of the anticancer effect. Moreover, the effectiveness of this combination was confirmed in a tumor xenograft model. These results revealed that inhibition of the JAK2-STAT3 pathway was a key anticancer mechanism when treated with PL alone or combined with DOX, suggesting that the combination of PL and chemotherapy drugs may be a potential strategy for the clinical treatment of TNBC.

Piperlongumine increases sensitivity of colorectal cancer cells to radiation: Involvement of ROS production via dual inhibition of glutathione and thioredoxin systems

Piperlongumine (PL), naturally synthesized in long pepper, is known to selectively kill tumor cells via perturbation of reactive oxygen species (ROS) homeostasis. ROS are the primary effector molecules of radiation, and increase of ROS production by pharmacological modulation is known to enhance radioresponse. We therefore investigated the radiosensitizing effect of PL in colorectal cancer cells (CT26 and DLD-1) and CT26 tumor-bearing mice. Firstly, we found that PL induced excessive production of ROS due to depletion of glutathione and inhibition of thioredoxin reductase. Secondly, PL enhanced both the intrinsic and hypoxic radiosensitivity of tumor cells, linked to ROS-mediated increase of DNA damage, G2/M cell cycle arrest, and inhibition of cellular respiration. Finally, the radiosensitizing effect of PL was verified in vivo. PL improved the tumor response to both single and fractionated radiation, resulting in a significant increase of survival rate of tumor-bearing mice, while it was ineffective on its own. In line with in vitro findings, enhanced radioresponse is associated with inhibition of antioxidant systems. In conclusion, our results suggest that PL could be a potential radiosensitizer in colorectal cancer.

Activity-based protein profiling reveals GSTO1 as the covalent target of piperlongumine and a promising target for combination therapy for cancer

Through systematic target identification for piperlongumine, a cancer-selective killing molecule, we identified GSTO1 as its major covalent target for cancer cell death induction. We also reveal that GSTO1 inhibition is a promising combination strategy with other anti-cancer agents by drug combination screening in which piperlongumine exhibits broad-spectrum synergistic effects with a large proportion of the tested anti-cancer agents, especially with PI3K/Akt/mTOR pathway inhibitors.

Repression of Hexokinases II-Mediated Glycolysis Contributes to Piperlongumine-Induced Tumor Suppression in Non-Small Cell Lung Cancer Cells

Deregulation of glycolysis is a common phenomenon in human non-small cell lung cancer (NSCLC). In the present study, we reported the natural compound, piperlongumine, has a profound anti-tumor effect on NSCLC via regulation of glycolysis. Piperlongumine suppressed the proliferation, colony formation and HK2-mediated glycolysis in NSCLC cells. We demonstrated that exposure to piperlongumine disrupted the interaction between HK2 and VDAC1, induced the activation of the intrinsic apoptosis signaling pathway. Moreover, our results revealed that piperlongumine down-regulated the Akt signaling, exogenous overexpression of constitutively activated Akt1 in HCC827 and H1975 cells significantly rescued piperlongumine-induced glycolysis suppression and apoptosis. The xenograft mouse model data demonstrated the pivotal role of suppression of Akt activation and HK2-mediated glycolysis in mediating the in vivo antitumor effects of piperlongumine. The expression of HK2 was higher in malignant NSCLC tissues than that of the paired adjacent tissues, and was positively correlated with poor survival time. Our results suggest that HK2 could be used as a potential predictor of survival and targeting HK2 appears to be a new approach for clinical NSCLC prevention or treatment.

Synergistic anticancer activity of doxorubicin and piperlongumine on DU-145 prostate cancer cells - The involvement of carbonyl reductase 1 inhibition

One of the causes of therapeutic failure of chemotherapy is cancer cell resistance. In the case of anthracyclines, many resistance mechanisms have been described. One of them assumes the role of carbonyl reductase 1 (CBR1), a cytosolic enzyme that is responsible for the biotransformation process of anthracyclines to less active, undesirable metabolites. Therefore, CBR1 inhibitors are considered for use as a chemosensitizing agents. In the present study, piperlongumine (PL), a Piper longum L. alkaloid that has previously been described as a CBR1 inhibitor, was investigated for its chemosensitizing properties in co-treatment with doxorubicin (DOX). The biotransformation process of DOX in the presence of PL was tracked using human cytosol fraction and LC-MS, then a molecular modeling study was conducted to predict the interaction of PL with the active site of the CBR1. The biological interaction between DOX and PL was investigated using DU-145 prostate cancer cells. Cytotoxic and antiproliferative properties of DOX and PL were examined, and the type and potency of interaction was quantified by Combination Index. The mechanism of the cell death induced by the agents was investigated by flow cytometry and the anti-invasive properties of the drugs were determined by monitoring the movement of individual cells. PL showed dose-dependent inhibition of DOX metabolism in cytosol, which resulted in less doxorubicinol (DOXol) metabolite being formed. The possible mechanism of CBR1 inhibition was explained through molecular modeling studies by prediction of PL's binding mode in the active site of the enzyme's crystal structure-based model. DOX and PL showed a synergistic antiproliferative and proapoptotic effect on cancer cells. Significant anti-invasive properties of the combination of DOX and PL were found, but when the drugs were used separately they did not alter the cancer cells' motility. Cell motility inhibition was accompanied by significant changes in cytoskeleton architecture. DOX and PL used in co-treatment showed significant synergistic anticancer properties. Inhibition of DOX metabolism by PL was found to be a mechanism that was likely to be responsible for the observed interaction.

Targeted therapies in pancreatic cancer: Promises and failures

Pancreatic ductal adenocarcinoma (PDAC) is an incidence rate nearly equal to its mortality rate. The poor prognosis of the disease can be explained by the absence of effective biomarkers for screening and early detection, together with the aggressive behavior and resistance to the currently available chemotherapy. The therapeutic failure can also be attributed to the inter-/intratumor genetic heterogeneity and the abundance of tumor stroma that occupies the majority of the tumor mass. Gemcitabine is used in the treatment of PDAC; however, the response rate is less than 12%. A recent phase III trial revealed that the combination of oxaliplatin, irinotecan, fluorouracil, and leucovorin could be an option for the treatment of metastatic PDAC patients with good performance status, although these approaches can result in high toxicity level. Further investigations are required to develop innovative anticancer agents that either improve gemcitabine activity, within novel combinatorial approaches or acts with a better efficacy than gemcitabine. The aim of the current review is to give an overview of preclinical and clinical studies targeting key dysregulated signaling pathways in PDAC.

Piperlongumine and p53-reactivator APR-246 selectively induce cell death in HNSCC by targeting GSTP1

TP53 mutations frequently occur in head and neck squamous cell carcinoma (HNSCC) patients without human papillomavirus infection. The recurrence rate for these patients is distinctly high. It has been actively explored to identify agents that target TP53 mutations and restore wild-type (WT) TP53 activities in HNSCC. PRIMA-1 (p53-reactivation and induction of massive apoptosis-1) and its methylated analogue PRIMA-1Met (also called APR-246) were found to be able to reestablish the DNA-binding activity of p53 mutants and reinstate the functions of WT p53. Herein we report that piperlongumine (PL), an alkaloid isolated from Piper longum L., synergizes with APR-246 to selectively induce apoptosis and autophagic cell death in HNSCC cells, whereas primary and immortalized mouse embryonic fibroblasts and spontaneously immortalized non-tumorigenic human skin keratinocytes (HaCat) are spared from the damage by the co-treatment. Interestingly, PL-sensitized HNSCC cells to APR-246 are TP53 mutation-independent. Instead, we demonstrated that glutathione S-transferase pi 1 (GSTP1), a GST family member that catalyzes the conjugation of GSH with electrophilic compounds to fulfill its detoxification function, is highly expressed in HNSCC tissues. Administration of PL and APR-246 significantly suppresses GSTP1 activity, resulting in the accumulation of ROS, depletion of GSH, elevation of GSSG, and DNA damage. Ectopic expression of GSTP1 or pre-treatment with antioxidant N-acetyl-L-cysteine (NAC) abrogates the ROS elevation and decreases DNA damage, apoptosis, and autophagic cell death prompted by PL/APR-246. In addition, administration of PL and APR-246 impedes UMSCC10A xenograft tumor growth in SCID mice. Taken together, our data suggest that HNSCC cells are selectively sensitive to the combination of PL and APR-246 due to a remarkably synergistic effect of the co-treatment in the induction of ROS by suppression of GSTP1.

Piperlongumine rapidly induces the death of human pancreatic cancer cells mainly through the induction of ferroptosis

Pancreatic cancer is one of the most lethal types of cancer with a mortality rate of almost 95%. Treatment with current chemotherapeutic drugs has limited success due to poor responses. Therefore, the development of novel drugs or effective combination therapies is urgently required. Piperlongumine (PL) is a natural product with cytotoxic properties restricted to cancer cells by significantly increasing intracellular reactive oxygen species (ROS) levels. In the present study, we demonstrated that PL induced cancer cell death through, at least in part, the induction of ferroptosis, as the cancer cell-killing activity was inhibited by the antioxidant, N‑acetylcysteine, ferroptosis inhibitors (ferrostatin‑1 and liproxstatin‑1) and the iron chelator, deferoxamine (DFO), but not by the apoptosis inhibitor, Z-VAD-FMK, or the necrosis inhibitor, necrostatin‑1. Cotylenin A (CN‑A; a plant growth regulator) exhibits potent antitumor activities in several cancer cell lines, including pancreatic cancer cell lines. We found that CN‑A and PL synergistically induced the death of pancreatic cancer MIAPaCa‑2 and PANC‑1 cells for 16 h. CN‑A enhanced the induction of ROS by PL for 4 h. The synergistic induction of cell death was also abrogated by the ferroptosis inhibitors and DFO. The present results revealed that clinically approved sulfasalazine (SSZ), a ferroptosis inducer, enhanced the death of pancreatic cancer cells induced by PL and the combined effects were abrogated by the ferroptosis inhibitors and DFO. SSZ further enhanced the cancer cell-killing activities induced by combined treatment with PL plus CN‑A. On the other hand, the synergistic induction of cell death by PL and CN‑A was not observed in mouse embryonic fibroblasts (MEFs), and SSZ did not enhance the death of MEFs induced by PL plus CN‑A. These results suggest that the triple combined treatment with PL, CN‑A and SSZ is highly effective against pancreatic cancer.

Piperlongumine decreases cell proliferation and the expression of cell cycle-associated proteins by inhibiting Akt pathway in human lung cancer cells

Piperlongumine (PL) is an alkaloid of a pepper plant found in Southeast Asia. PL is known to induce selective toxicity towards a variety of cancer cell types. To explore the possible anti-lung cancer effects of PL, A549 cells were treated with PL (0-40 μM) for 24 h. Alterations in the expression of cell cycle-associated proteins (cyclin D1, cyclin-dependent kinase 4 (CDK4), CDK6 and retinoblastoma (Rb)) and intracellular signaling molecules (extracellular signal receptor-activated kinase 1/2 (ERK1/2), Akt, p38 and nuclear factor-κB (NF-κB)) were examined in cells following treatment of PL using Western blot analysis. Results showed that proliferation of cells were significantly decreased by PL in a dose-dependent manner. Flow cytometry results demonstrated increased number of cells in G1 phase in PL (40 μM)-treated group. Reactive oxygen species was significantly increased in cells treated with PL at 20-40 μM. The expression of cyclin D1, CDK4, CDK6 and p-Rb were markedly decreased in cells treated with PL at 40 μM. Treatment of cells with PL suppressed phosphorylation of Akt but increased ERK1/2 phosphorylation. Treatment of PL significantly decreased nuclear translocation of NF-κB p65 in cells. These results suggest that PL possesses antiproliferative properties in A549 cells.

Piperlongumine potentiates the effects of gemcitabine in in vitro and in vivo human pancreatic cancer models

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers due to a late diagnosis and poor response to available treatments. There is a need to identify complementary treatment strategies that will enhance the efficacy and reduce the toxicity of currently used therapeutic approaches. We investigated the ability of a known ROS inducer, piperlongumine (PL), to complement the modest anti-cancer effects of the approved chemotherapeutic agent gemcitabine (GEM) in PDAC cells in vitro and in vivo. PDAC cells treated with PL + GEM showed reduced cell viability, clonogenic survival, and growth on Matrigel compared to control and individually-treated cells. Nude mice bearing orthotopically implanted MIA PaCa-2 cells treated with both PL (5 mg/kg) and GEM (25 mg/kg) had significantly lower tumor weight and volume compared to control and single agent-treated mice. RNA sequencing (RNA-Seq) revealed that PL + GEM resulted in significant changes in p53-responsive genes that play a role in cell death, cell cycle, oxidative stress, and DNA repair pathways. Cell culture assays confirmed PL + GEM results in elevated ROS levels, arrests the cell cycle in the G0/G1 phase, and induces PDAC cell death. We propose a mechanism for the complementary anti-tumor effects of PL and GEM in PDAC cells through elevation of ROS and transcription of cell cycle arrest and cell death-associated genes. Collectively, our results suggest that PL has potential to be combined with GEM to more effectively treat PDAC.

Novel piplartine-containing ruthenium complexes: synthesis, cell growth inhibition, apoptosis induction and ROS production on HCT116 cells

Piplartine (piperlongumine) is a plant-derived molecule that has been receiving intense interest due to its anticancer characteristics that target the oxidative stress. In the present paper, two novel piplartine-containing ruthenium complexes [Ru(piplartine)(dppf)(bipy)](PF₆)₂ (1) and [Ru(piplartine)(dppb)(bipy)](PF₆)₂ (2) were synthesized and investigated for their cellular and molecular responses on cancer cell lines. We found that both complexes are more potent than metal-free piplartine in a panel of cancer cell lines on monolayer cultures, as well in 3D model of cancer multicellular spheroids formed from human colon carcinoma HCT116 cells. Mechanistic studies uncovered that the complexes reduced the cell growth and caused phosphatidylserine externalization, internucleosomal DNA fragmentation, caspase-3 activation and loss of the mitochondrial transmembrane potential on HCT116 cells. Moreover, the pre-treatment with Z-VAD(OMe)-FMK, a pan-caspase inhibitor, reduced the complexes-induced apoptosis, indicating cell death by apoptosis through caspase-dependent and mitochondrial intrinsic pathways. Treatment with the complexes also caused a marked increase in the production of reactive oxygen species (ROS), including hydrogen peroxide, superoxide anion and nitric oxide, and decreased reduced glutathione levels. Application of N-acetyl-cysteine, an antioxidant, reduced the ROS levels and apoptosis induced by the complexes, indicating activation of ROS-mediated apoptosis pathway. RNA transcripts of several genes, including gene related to the cell cycle, apoptosis and oxidative stress, were regulated under treatment. However, the complexes failed to induce DNA intercalation. In conclusion, the complexes are more potent than piplartine against different cancer cell lines and are able to induce caspase-dependent and mitochondrial intrinsic apoptosis on HCT116 cells by ROS-mediated pathway.

Natural Products as Adjunctive Treatment for Pancreatic Cancer: Recent Trends and Advancements

Pancreatic cancer is a type of common malignant tumors with high occurrence in the world. Most patients presented in clinic had pancreatic cancer at advanced stages. Furthermore, chemotherapy or radiotherapy had very limited success in treating pancreatic cancer. Complementary and alternative medicines, such as natural products/herbal medicines, represent exciting adjunctive therapies. In this review, we summarize the recent advances of using natural products/herbal medicines, such as Chinese herbal medicine, in combination with conventional chemotherapeutic agents to treat pancreatic cancer in preclinical and clinical trials.

Piperlongumine (piplartine) and analogues: Antiproliferative microtubule-destabilising agents

Piperlongumine (piplartine, 1) is a small molecule alkaloid that is receiving intense interest due to its antiproliferative and anticancer activities. We investigated the effects of 1 on tubulin and microtubules. Using both an isolated tubulin assay, and a combination of sedimentation and western blotting, we demonstrated that 1 is a tubulin-destabilising agent. This result was confirmed by immunofluorescence and confocal microscopy, which showed that microtubules in MCF-7 breast cancer cells were depolymerized when treated with 1. We synthesised a number of analogues of 1 to explore structure-activity relationships. Compound 13 had the best cytotoxic profile of this series, showing potent effects in human breast carcinoma MCF-7 cells whilst being relatively non-toxic to non-tumorigenic MCF-10a cells. These compounds will be further developed as potential clinical candidates for the treatment of breast cancer.

Discovery of piperlongumine as a potential novel lead for the development of senolytic agents

Accumulating evidence indicates that senescent cells play an important role in many age-associated diseases. The pharmacological depletion of senescent cells (SCs) with a "senolytic agent", a small molecule that selectively kills SCs, is a potential novel therapeutic approach for these diseases. Recently, we discovered ABT-263, a potent and highly selective senolytic agent, by screening a library of rationally-selected compounds. With this screening approach, we also identified a second senolytic agent called piperlongumine (PL). PL is a natural product that is reported to have many pharmacological effects, including anti-tumor activity. We show here that PL preferentially killed senescent human WI-38 fibroblasts when senescence was induced by ionizing radiation, replicative exhaustion, or ectopic expression of the oncogene Ras. PL killed SCs by inducing apoptosis, and this process did not require the induction of reactive oxygen species. In addition, we found that PL synergistically killed SCs in combination with ABT-263, and initial structural modifications to PL identified analogs with improved potency and/or selectivity in inducing SC death. Overall, our studies demonstrate that PL is a novel lead for developing senolytic agents.