Enhanced anti-tumor efficacy and mechanisms associated with docetaxel-piperine combination- in vitro and in vivo investigation using a taxane-resistant prostate cancer model

Synergistic enhancement: Exploring the potential of piperine in cancer therapeutics through chemosensitization and combination therapies

Despite significant advancements in chemotherapy, effective treatments for advanced cancer stages remain largely elusive due to chemoresistance. Resistance to anticancer agents in cancer cells can arise through various mechanisms, including multi-drug resistance, inhibition of apoptosis, modification of drug targets, and enhancement of DNA repair capabilities. Consequently, there is a critical need for agents that can suppress the molecular signatures responsible for drug resistance. Piperine, an active alkaloid extracted from Piper nigrum L. (black pepper), is one such agent that has been extensively studied for its potential in addressing chronic diseases, including cancer. Piperine's antineoplastic properties are mediated through the regulation of numerous key cellular signaling pathways and the modulation of various biological processes. Its capability to enhance drug bioavailability and counteract mechanisms of drug resistance, such as the inhibition of P-glycoprotein (P-gp) and multidrug resistance-associated protein 1 (MRP-1), emphasizes its potential as an adjunct in cancer therapy. Research across various cancer types has demonstrated piperine's role in chemosensitization by targeting P-gp and MRP-1 and altering drug-metabolizing enzymes. This review provides a comprehensive analysis of piperine's pharmacological characteristics and its capacity to modulate several cellular signaling pathways involved in drug resistance. Furthermore, the review emphasizes how piperine, when used in conjunction with other chemotherapeutic agents or natural compounds, can enhance therapeutic effects, leading to improved outcomes in cancer treatment.

Synthesis and characterization of piperine-modified mesoporous silica nanoparticles for biomedical applications

Mesoporous silica nanoparticles (MSNs) have displayed high-potential prospects in biomedical use, especially for drug delivery due to large surface area, tunable pore size and simple surface functionalization. The objective behind the present research is to synthesize and profile piperine-modified MSNs for their preparation due to antioxidative anticarcinogenic, anti-inflammatory properties of the alkaloid chosen as a modifier. In the study, silica piperine nanoparticles (SPN) were fabricated based on a modified Stöber method. Characterization techniques including SEM, TEM, AFM, FTIR, XRD, and DSC showed significant differences of incorporated piperine in the production process to plain MSN properties. Piperine was observed to inhibit nanoparticles' growth so that they became smaller, heterogeneous, with a changed morphology and surface chemistry. As a strong confirmation of covalent incorporation, spectroscopic data showed the presence of electrons in the piperine's functional group that were exchanged into some silanol groups and removed excessive surface energy. The antioxidant activity of SPNs revealed that the silica matrix, and moreover bioactive piperine combination resulted to significant increase in enhanced antioxidant potential. In general, the results of this study offer meaningful lessons about the utilization and manipulation of piperine to suit MSN in a bid to optimize them for biomedical uses such as drug delivery applications where its antioxidant characteristics may bring therapeutic benefits. This holistic characterization and standardization of piperine-modified MSNs sets the solid stage for further project practice and advance adjustment in aluminosilicate nanostructures designed for biomedical application.

Enhancing Paclitaxel Efficacy with Piperine-Paclitaxel Albumin Nanoparticles in Multidrug-Resistant Triple-Negative Breast Cancer by Inhibiting P-Glycoprotein

Triple-negative breast cancer (TNBC) is a highly aggressive disease with rapid progression and poor prognosis due to multidrug resistance (MDR). Piperine (PIP) shows promise as a P-gp inhibitor, capable of sensitizing chemotherapeutic drugs and exhibiting antitumor properties. This study explores the inhibitory mechanism of PIP on P-glycoprotein (P-gp) and its capacity to enhance the sensitivity of paclitaxel (PTX). We subsequently evaluated the efficacy and safety of albumin nanoparticles that co-encapsulate PTX and PIP (PP@AN). The results demonstrated that PIP enhanced the accumulation of PTX intracellularly, as determined with HPLC/MS/MS analysis. PIP was also found to increase cell sensitivity to PTX. Furthermore, we explored the inhibitory mechanism of PIP on P-gp, utilizing molecular docking simulations, RT-qPCR, and Western blot analysis. PIP appears to compete with the active paclitaxel binding site on P-gp, affecting ATPase activity and downregulating the MDR1 gene and P-gp expression. In summary, PIP could inhibit P-gp and act as a sensitizer in the treatment of TNBC with PTX. Moreover, stable and uniform PP@AN was successfully formulated, resulting in a significant increase in drug accumulation within cells as well as the downregulation of P-gp in tumors at the optimal ratio (PTX:PIP = 1:2). This led to an improvement in the antitumor effect in vivo while also reducing hepatotoxicity and hemototoxicity following chemotherapy. This study comprehensively investigated PIP's inhibitory effect and mechanism on P-gp. We present a new approach for co-delivering PIP and PTX using albumin nanoparticles, which reduced toxicity and improved therapeutic efficacy both in vivo and in vitro.

Extraction, Characterization, and Evaluation of the Cytotoxic Activity of Piperine in Its Isolated form and in Combination with Chemotherapeutics against Gastric Cancer

Gastric cancer is one of the most frequent types of neoplasms worldwide, usually presenting as aggressive and difficult-to-manage tumors. The search for new structures with anticancer potential encompasses a vast research field in which natural products arise as promising alternatives. In this scenario, piperine, an alkaloid of the Piper species, has received attention due to its biological activity, including anticancer attributes. The present work proposes three heating-independent, reliable, low-cost, and selective methods for obtaining piperine from Piper nigrum L. (Black pepper). Electronic (SEM) and optical microscopies, X-ray diffraction, nuclear magnetic resonance spectroscopies (¹³C and ¹H NMR), and optical spectroscopies (UV-Vis, photoluminescence, and FTIR) confirm the obtention of piperine crystals. The MTT assay reveals that the piperine samples exhibit good cytotoxic activity against primary and metastasis models of gastric cancer cell lines from the Brazilian Amazon. The samples showed selective cytotoxicity on the evaluated models, revealing higher effectiveness in cells bearing a higher degree of aggressiveness. Moreover, the investigated piperine crystals demonstrated the ability to act as a good cytotoxicity enhancer when combined with traditional chemotherapeutics (5-FU and GEM), allowing the drugs to achieve the same cytotoxic effect in cells employing lower concentrations. These results establish piperine as a promising molecule for therapy investigations in aggressive gastric cancer, both in its isolated form or as a bioenhancer.

Paclitaxel and docetaxel resistance in prostate cancer: Molecular mechanisms and possible therapeutic strategies

Prostate cancer is among most malignant tumors around the world and this urological tumor can be developed as result of genomic mutations and their accumulation during progression towards advanced stage. Due to lack of specific symptoms in early stages of prostate cancer, most cancer patients are diagnosed in advanced stages that tumor cells display low response to chemotherapy. Furthermore, genomic mutations in prostate cancer enhance the aggressiveness of tumor cells. Docetaxel and paclitaxel are suggested as well-known compounds for chemotherapy of prostate tumor and they possess a similar function in cancer therapy that is based on inhibiting depolymerization of microtubules, impairing balance of microtubules and subsequent delay in cell cycle progression. The aim of current review is to highlight mechanisms of paclitaxel and docetaxel resistance in prostate cancer. When oncogenic factors such as CD133 display upregulation and PTEN as tumor-suppressor shows decrease in expression, malignancy of prostate tumor cells enhances and they can induce drug resistance. Furthermore, phytochemicals as anti-tumor compounds have been utilized in suppressing chemoresistance in prostate cancer. Naringenin and lovastatin are among the anti-tumor compounds that have been used for impairing progression of prostate tumor and enhancing drug sensitivity. Moreover, nanostructures such as polymeric micelles and nanobubbles have been utilized in delivery of anti-tumor compounds and decreasing risk of chemoresistance development. These subjects are highlighted in current review to provide new insight for reversing drug resistance in prostate cancer.

The role of AKR1 family in tamoxifen resistant invasive lobular breast cancer based on data mining

Background

Tamoxifen (TAM) resistance to invasive lobular cell carcinoma is a challenge for breast cancer treatment. This study explored the role of Aldo-keto reductase family 1 (AKR1) family in tamoxifen-resistant aggressive lobular breast cancer based on data mining.

Methods

TAM-resistant invasive lobular breast cancer gene chip was downloaded from the Gene Expression Omnibus (GEO) database (accession-numbered as GSE96670). The online analytical tool GEO2R was used to screen for differentially expressed genes in TAM-resistant invasive lobular breast cancer cells and TAM-sensitive counterparts. A protein-protein interaction (PPI) networks were constructed using the STRING online platform and the Cytoscape software. GeneMANIA and GSCALite online tools were used to reveal the potential role of these hub genes in breast cancer progression and TAM resistance development. And the used the GSE67916 microarray data set to verify the differentially expression of these hub genes in breast cancer. The protein expression levels of AKR1C1, AKR1C2 and AKR1C3 in TAM-sensitive and resistant breast cancer cells were compared. The TAM sensitivity of breast cancer cells with or without AKR1C1, AKR1C2 or AKR1C3 gene manipulation was evaluated by cell viability assay.

Results

A total of 184 differentially expressed genes were screened. Compared with TAM sensitive breast cancer cells, 162 were up-regulated and 22 were down-regulated. The study identified several hub genes in the PPI network that may be involved in the development of TAM resistance of breast cancer, including signal transducer and activator of transcription 1 (STAT1), estrogen receptor alpha (ESR1), fibronectin1 (FN1), cytochrome P4501B1 (CYP1B1), AKR1C1, AKR1C2, AKR1C3 and uridine diphosphate glucuronosyltransferase (UGT) 1A family genes (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A7, UGT1A8, UGT1A9, UGT1A10). Compared with TAM-sensitive counterparts, the expression levels of AKR1C1, AKR1C2, and AKR1C3 were up-regulated in TAM-resistant breast cancer cells.

Conclusions

Overexpression of each of these three genes significantly increased the resistance of breast cancer cells to TAM treatment, while their knockdown showed opposite effects, indicating that they are potential therapeutic target for the treatment of TAM-resistant breast cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-09040-8.

Modulation of inflammation by phytochemicals to enhance efficacy and reduce toxicity of cancer chemotherapy

Treatment of cancer with chemotherapeutic drugs is associated with numerous adverse effects as well as the eventual development of resistance to chemotherapy. There is a great need for complementary therapies such as botanicals and nutritional supplements with little or no side effects that prevent resistance to chemotherapy and reduce its adverse effects. Inflammation plays a major role in the development of chemoresistance and the adverse effects of chemotherapy. Phytochemicals have well-established anti-inflammatory effects; thus, they could be used as complementary therapies along with chemotherapy to increase its efficacy and reduce its toxicity. Botanical compounds inhibit the NF-κB signaling pathway, which plays an important role in the generation of inflammation, chemotherapy resistance, and modulation of cell survival and apoptosis. Botanicals have previously been studied extensively for their cancer chemopreventive activities and are generally considered safe for human consumption. The present review focuses on the modulation of inflammation by phytochemicals and their role in increasing the efficacy and reducing the toxicity of cancer chemotherapy.

Exploring new Horizons in overcoming P-glycoprotein-mediated multidrug-resistant breast cancer via nanoscale drug delivery platforms

The high probability (13%) of women developing breast cancer in their lifetimes in America is exacerbated by the emergence of multidrug resistance after exposure to first-line chemotherapeutic agents. Permeation glycoprotein (P-gp)-mediated drug efflux is widely recognized as the major driver of this resistance. Initial in vitro and in vivo investigations of the co-delivery of chemotherapeutic agents and P-gp inhibitors have yielded satisfactory results; however, these results have not translated to clinical settings. The systemic delivery of multiple agents causes adverse effects and drug-drug interactions, and diminishes patient compliance. Nanocarrier-based site-specific delivery has recently gained substantial attention among researchers for its promise in circumventing the pitfalls associated with conventional therapy. In this review article, we focus on nanocarrier-based co-delivery approaches encompassing a wide range of P-gp inhibitors along with chemotherapeutic agents. We discuss the contributions of active targeting and stimuli responsive systems in imparting site-specific cytotoxicity and reducing both the dose and adverse effects.

Prostate cancer: Therapeutic prospect with herbal medicine

Prostate cancer (PCa) is a major cause of morbidity and mortality in men worldwide. A geographic variation on the burden of the disease suggested that the environment, genetic makeup, lifestyle, and food habits modulate one's susceptibility to the disease. Although it has been generally thought to be an older age disease, and awareness and timely execution of screening programs have managed to contain the disease in the older population over the last decades, the incidence is still increasing in the population younger than 50. Existing treatment is efficient for PCa that is localized and responsive to androgen. However, the androgen resistant and metastatic PCa are challenging to treat. Conventional radiation and chemotherapies are associated with severe side effects in addition to being exorbitantly expensive. Many isolated phytochemicals and extracts of plants used in traditional medicine are known for their safety and diverse healing properties, including many with varying levels of anti-PCa activities. Many of the phytochemicals discussed here, as shown by many laboratories, inhibit tumor cell growth and proliferation by interfering with the components in the pathways responsible for the enhanced proliferation, metabolism, angiogenesis, invasion, and metastasis in the prostate cells while upregulating the mechanisms of cell death and cell cycle arrest. Notably, many of these agents simultaneously target multiple cellular pathways. We analyzed the available literature and provided an update on this issue in this review article.

Piperine Targets Different Drug Resistance Mechanisms in Human Ovarian Cancer Cell Lines Leading to Increased Sensitivity to Cytotoxic Drugs

Our goal was to examine the anticancer effects of piperine against the resistant human ovarian cancer cells and to explore the molecular mechanisms responsible for its anticancer effects. Our study used drug-sensitive ovarian cancer cell line W1 and its sublines resistant to paclitaxel (PAC) and topotecan (TOP). We analyzed the cytotoxic effect of piperine and cytostatic drugs using an MTT assay. The impact of piperine on protein expression was determined by immunofluorescence and Western blot. We also examined its effect on cell proliferation and migration. We noticed a different level of piperine resistance between cell lines. Piperine increases the cytotoxic effect of PAC and TOP in drug-resistant cells. We observed an increase in PTPRK expression correlated with decreased pTYR level after piperine treatment and downregulation of P-gp and BCRP expression. We also noted a decrease in COL3A1 and TGFBI expression in investigated cell lines and increased COL3A1 expression in media from W1PR2 cells. The expression of Ki67 protein and cell proliferation rate decreased after piperine treatment. Piperine markedly inhibited W1TR cell migration. Piperine can be considered a potential anticancer agent that can increase chemotherapy effectiveness in cancer patients.

[18F]-JK-PSMA-7 and [18F]-FDG tumour PET uptake in treated xenograft human prostate cancer model in mice

PURPOSE

This preclinical study aims to evaluate the extent to which a change in prostate-specific membrane antigen (PSMA) expression of castration-resistant prostate cancer (CRPC) following standard treatment is reflected in [¹⁸F]JK-PSMA-7 PET/CT.

METHODS

Castrated mice supplemented with testosterone implant were xenografted with human LNCaP CRPC. After appropriate tumour growth, androgen deprivation therapy (ADT) was carried out by the removal of the implant followed by a single injection of docetaxel (400 μg/20-g mouse) 2 weeks later. [¹⁸F]JK-PSMA-7 PET/CT were performed before ADT, then before and at days 12, 26, 47 and 69 after docetaxel administration. The [¹⁸F]JK-PSMA-7 PET data were compared to corresponding unspecific metabolic [¹⁸F]FDG PET/CT and ex vivo quantification of PSMA expression estimated by flow cytometry on repeated tumour biopsies.

RESULTS

ADT alone had no early effect on LNCaP tumours that pursued their progression. Until day 12 post-docetaxel, the [¹⁸F]JK-PSMA7 uptake was significantly higher than that of [¹⁸F]FDG, indicating the persistence of PSMA expression at those time points. From day 26 onwards when the tumours were rapidly expanding, both [¹⁸F]JK-PSMA7 and [¹⁸F]FDG uptake continuously decreased although the decrease in [¹⁸F]JK-PSMA uptake was markedly faster. The fraction of PSMA-positive cells in tumour biopsies decreased similarly over time to reach a non-specific level after the same time period.

CONCLUSION

Applying PSMA-based imaging for therapy monitoring in patients with CRPC should be considered with caution since a reduction in [¹⁸F]JK-PSMA-7 PET uptake after successive ADT and chemotherapy may be related to downregulation of PSMA expression in dedifferentiated and rapidly proliferating tumour cells.

Overview of the Anticancer Potential of the "King of Spices" Piper nigrum and Its Main Constituent Piperine

The main limits of current anticancer therapy are relapses, chemoresistance, and toxic effects resulting from its poor selectivity towards cancer cells that severely impair a patient's quality of life. Therefore, the discovery of new anticancer drugs remains an urgent challenge. Natural products represent an excellent opportunity due to their ability to target heterogenous populations of cancer cells and regulate several key pathways involved in cancer development, and their favorable toxicological profile. Piper nigrum is one of the most popular spices in the world, with growing fame as a source of bioactive molecules with pharmacological properties. The present review aims to provide a comprehensive overview of the anticancer potential of Piper nigrum and its major active constituents-not limited to the well-known piperine-whose undeniable anticancer properties have been reported for different cancer cell lines and animal models. Moreover, the chemosensitizing effects of Piper nigrum in association with traditional anticancer drugs are depicted and its toxicological profile is outlined. Despite the promising results, human studies are missing, which are crucial for supporting the efficacy and safety of Piper nigrum and its single components in cancer patients.

BioPerine Encapsulated Nanoformulation for Overcoming Drug-Resistant Breast Cancers

The evolving dynamics of drug resistance due to tumor heterogeneity often creates impediments to traditional therapies making it a challenging issue for cancer cure. Breast cancer often faces challenges of current therapeutic interventions owing to its multiple complexities and high drug resistivity， for example against drugs like trastuzumab and tamoxifen. Drug resistance in the majority of breast cancer is often aided by the overtly expressed P-glycoprotein (P-gp) that guides in the rapid drug efflux of chemotherapy drugs. Despite continuous endeavors and ground-breaking achievements in the pursuit of finding better cancer therapeutic avenues, drug resistance is still a menace to hold back. Among newer therapeutic approaches, the application of phytonutrients such as alkaloids to suppress P-gp activity in drug-resistant cancers has found an exciting niche in the arena of alternative cancer therapies. In this work, we would like to present a black pepper alkaloid derivative known as BioPerine-loaded chitosan (CS)-polyethylene glycol (PEG) coated polylactic acid (PLA) hybrid polymeric nanoparticle to improve the bioavailability of BioPerine and its therapeutic efficacy in suppressing P-gp expression in MDA-MB 453 breast cancer cell line. Our findings revealed that the CS-PEG-BioPerine-PLA nanoparticles demonstrated a smooth spherical morphology with an average size of 316 nm, with improved aqueous solubility, and provided sustained BioPerine release. The nanoparticles also enhanced in vitro cytotoxicity and downregulation of P-gp expression in MDA-MB 453 cells compared to the commercial inhibitor verapamil hydrochloride, thus promising a piece of exciting evidence for the development of BioPerine based nano-drug delivery system in combination with traditional therapies as a crucial approach to tackling multi-drug resistance in cancers.

Anticancer bioactive peptide combined with docetaxel and its mechanism in the treatment of breast cancer

Breast cancer remains a worldwide public-health issue. Novel drugs that increase the sensitivity and reduce the toxic side effects of chemotherapeutic agents are urgently required. The present study investigated the effect and mechanism of the short-term intermittent administration of an anticancer bioactive peptide (ACBP), docetaxel (DTX), ACBP combined with DTX (MIX) and ACBP combined with low dose DTX (L-MIX) to nude mice bearing human breast cancer tumors. The body weight, tumor length, tumor diameter, diet and water consumption of the tumor-bearing nude mice were calculated. The protein and mRNA expression levels of p53, p21 and Ki67 were detected via immunohistochemistry and reverse transcription-quantitative PCR, respectively. The results revealed that the activity level of each group of mice was consistent. However, the food and water consumption of the ACBP group was significantly increased compared with the NS group. Compared with the normal saline group, the tumor weights and volumes of the treatment groups were significantly decreased, indicating an inhibitory effect of the treatment. However, the MIX group exhibited lower tumor weights and volumes compared with the ACBP and DTX groups. Furthermore, no significant cell necrosis, edema or inflammatory cell infiltration was observed upon hematoxylin & eosin staining of the liver and spleen in all groups. The results also revealed that the p21, p53 and Ki67 protein and mRNA levels were decreased in the ACBP, DTX and MIX groups compared with the control group. Additionally, when compared with those in the MIX and L-MIX groups, the p21 and Ki67 protein, and p53 and Ki67 mRNA levels in the ACBP and DTX groups were significantly increased. The results suggested that the short-term intermittent use of ACBP alone had an inhibitory effect on tumor growth and improved the food and water consumption of tumor-bearing nude mice. Furthermore, the combination of ACBP and DTX reduced toxic side effects and the dosage requirement of drugs to achieve therapeutic effects on the tumor-bearing nude mice. Therefore, the antitumor effect of ACBP may be associated with the improvement of immune function in tumor-bearing nude mice and ACBP may serve an antitumor role via the p53-p21 signaling pathway in breast cancer.

Piperine Inhibits TGF-β Signaling Pathways and Disrupts EMT-Related Events in Human Lung Adenocarcinoma Cells

Background: Piperine, an amide extracted from the Piper spices, exhibits strong anti-tumor properties. However, its effect on the epithelial–mesenchymal transition (EMT) process has never been investigated. Herein, we evaluate the toxic effect of piperine on lung adenocarcinoma (A549), breast adenocarcinoma (MDA-MB-231) and hepatocellular carcinoma (HepG2) cell lines, as well as its ability to inhibit EMT-related events induced by TGF-β1 treatment. Methods: The cell viability was investigated by MTT assay. Protein expression was evaluated by Western blot. Gene expression was monitored by real-time PCR. Zymography assay was employed to detect metalloproteinase (MMP) activity in conditioned media. Cell motility was assessed by the wound-healing and phagokinetic gold sol assays. Results: The results revealed that piperine was cytotoxic in concentrations over 100 µM, showing IC50 values for HepG2, MDA-MB-231 and A549 cell lines of 214, 238 and 198 µM, respectively. In order to investigate whether piperine would reverse the TGF-β1 induced-EMT, the A549 cell line was pretreated with sublethal concentrations of the natural amide followed by the addition of TGF-β1. Besides disrupting EMT-related events, piperine also inhibited both ERK 1/2 and SMAD 2 phosphorylation. Conclusions: These results suggest that piperine might be further used in therapeutic strategies for metastatic cancer and EMT-related disorders.

Soluplus®/TPGS mixed micelles for co-delivery of docetaxel and piperine for combination cancer therapy

In this study, mixed micelles of Soluplus^® and TPGS were developed for co-administering docetaxel (DTX) and piperine (PIP) for exerting the synergistic effect, which increased the cytotoxicity and improved the anti-cancer activity in HepG2 cell lines compared to free DTX. These in vitro (MTT assay, intracellular uptake of micelles) and in vivo (pharmacokinetic study, immunostaining, TUNEL analysis) studies exhibited the advantages of co-delivery of anticancer drugs with Soluplus^®/TPGS by mixed micelles and furthermore established that co-delivery of DTX and PIP via the mixed micelles of Soluplus^®/TPGS could be a promising strategy for the treatment of liver cancer.

Piperine: role in prevention and progression of cancer

Cancer is among the leading causes of death worldwide. Several pharmacological protocols have been developed in order to block tumor progression often showing partial efficacy and severe counterproductive effects. It is now conceived that a healthy lifestyle coupled with the consumption of certain phytochemicals can play a protective role against tumor development and progression. According to this vision, it has been introduced the concept of "chemoprevention". This term refers to natural agents with the capability to interfere with the tumorigenesis and metastasis, or at least, attenuate the cancer-related symptoms. Piperine (1-Piperoylpiperidine), a main extract of Piper longum and Piper nigrum, is an alkaloid with a long history of medicinal use. In fact, it exhibits a variety of biochemical and pharmaceutical properties, including chemopreventive activities without significant cytotoxic effects on normal cells, at least at doses < of 250 µg/ml. The aim of this review is to discuss the relevant molecular and cellular mechanisms underlying the chemopreventive action of this natural alkaloid.

Ophiopogonin D', a Natural Product From Radix Ophiopogonis, Induces in Vitro and in Vivo RIPK1-Dependent and Caspase-Independent Apoptotic Death in Androgen-Independent Human Prostate Cancer Cells

Objective: The purpose of this study was to evaluate the anticancer effects of Ophiopogonin D′ (OPD′, a natural product extracted from a traditional Chinese medicine (Radix Ophiopogonis) against androgen-independent prostate cancer cells and to explore the underlying molecular mechanism(s) of action.

Methods: The CCK-8 assay was used to assess the viability of prostate cancer cells. The cell morphology was examined by an ultrastructural analysis via transmission electron microscopy. Cells in apoptosis (early and late stages) were detected using an Annexin V-FITC/propidium iodide kit with a FACSCaliber flow cytometer. JC-1, a cationic lipophilic probe, was employed to measure the mitochondrial membrane potential (MMP) of PC3 cells. Changes in the protein expression of RIPK1, C-RIPK1, caspase 8, cleaved-caspase 8, Bim, Bid, caspase 10, and cleaved-caspase 10 were evaluated by Western blotting. The mRNA expression of Bim was examined by quantitative real-time reverse transcription polymerase chain reaction. Z-VAD-FMK (a caspase inhibitor) and necrostatin-1 (a specific inhibitor of RIPK1) were utilized to determine whether the cell death was mediated by RIPK1 or caspases. PC3 and DU145 xenograft models in BALB/c nude mice were used to evaluate the anticancer activity of OPD′ in vivo.

Results: OPD′ was shown to exert potent anti-tumor activity against PC3 cells. It induced apoptosis via a RIPK1-related pathway, increased the protein expression levels of RIPK1 and Bim, and decreased the levels of cleaved-RIPK1, caspase 8, cleaved-caspase 8, Bid, caspase 10, and cleaved-caspase 10. OPD′ also increased the mRNA expression of Bim. The protein expression of Bim was decreased when cells were pre-treated with necrostatin-1. Treatment with OPD′ inhibited the growth of PC3 and DU145 xenograft tumors in BALB/c nude mice.

Conclusion: OPD′ significantly inhibited the in vitro and in vivo growth of prostate cells via RIPK1, suggesting that OPD′ may be developed as a potential anti-prostate cancer agent.