Intratumoral delivery of beta-lapachone via polymer implants for prostate cancer therapy

Human NQO1 as a Selective Target for Anticancer Therapeutics and Tumor Imaging

Human NAD(P)H-quinone oxidoreductase1 (HNQO1) is a two-electron reductase antioxidant enzyme whose expression is driven by the NRF2 transcription factor highly active in the prooxidant milieu found in human malignancies. The resulting abundance of NQO1 expression (up to 200-fold) in cancers and a barely detectable expression in body tissues makes it a selective marker of neoplasms. NQO1 can catalyze the repeated futile redox cycling of certain natural and synthetic quinones to their hydroxyquinones, consuming NADPH and generating rapid bursts of cytotoxic reactive oxygen species (ROS) and H2O2. A greater level of this quinone bioactivation due to elevated NQO1 content has been recognized as a tumor-specific therapeutic strategy, which, however, has not been clinically exploited. We review here the natural and new quinones activated by NQO1, the catalytic inhibitors, and the ensuing cell death mechanisms. Further, the cancer-selective expression of NQO1 has opened excellent opportunities for distinguishing cancer cells/tissues from their normal counterparts. Given this diagnostic, prognostic, and therapeutic importance, we and others have engineered a large number of specific NQO1 turn-on small molecule probes that remain latent but release intense fluorescence groups at near-infrared and other wavelengths, following enzymatic cleavage in cancer cells and tumor masses. This sensitive visualization/quantitation and powerful imaging technology based on NQO1 expression offers promise for guided cancer surgery, and the reagents suggest a theranostic potential for NQO1-targeted chemotherapy.

Augmented Concentration of Isopentyl-Deoxynyboquinone in Tumors Selectively Kills NAD(P)H Quinone Oxidoreductase 1-Positive Cancer Cells through Programmed Necrotic and Apoptotic Mechanisms

Lung and breast cancers rank as two of the most common and lethal tumors, accounting for a substantial number of cancer-related deaths worldwide. While the past two decades have witnessed promising progress in tumor therapy, developing targeted tumor therapies continues to pose a significant challenge. NAD(P)H quinone oxidoreductase 1 (NQO1), a two-electron reductase, has been reported as a promising therapeutic target across various solid tumors. β-Lapachone (β-Lap) and deoxynyboquinone (DNQ) are two NQO1 bioactivatable drugs that have demonstrated potent antitumor effects. However, their curative efficacy has been constrained by adverse effects and moderate lethality. To enhance the curative potential of NQO1 bioactivatable drugs, we developed a novel DNQ derivative termed isopentyl-deoxynyboquinone (IP-DNQ). Our study revealed that IP-DNQ treatment significantly increased reactive oxygen species generation, leading to double-strand break (DSB) formation, PARP1 hyperactivation, and catastrophic energy loss. Notably, we discovered that this novel drug induced both apoptosis and programmed necrosis events, which makes it entirely distinct from other NQO1 bioactivatable drugs. Furthermore, IP-DNQ monotherapy demonstrated significant antitumor efficacy and extended mice survival in A549 orthotopic xenograft models. Lastly, we identified that in mice IP-DNQ levels were significantly elevated in the plasma and tumor compared with IB-DNQ levels. This study provides novel preclinical evidence supporting IP-DNQ efficacy in NQO1+ NSCLC and breast cancer cells.

Enhanced Chemodynamic Therapy Mediated by a Tumor-Specific Catalyst in Synergy with Mitophagy Inhibition Improves the Efficacy for Endometrial Cancer

Chemodynamic therapy (CDT) relies on the tumor microenvironment (e.g., high H2 O2 level) responsive Fenton-like reactions to produce hydroxyl radicals (·OH) against tumors. However, endogenous H2 O2 is insufficient for effective chemodynamic responses. An NAD(P)H: quinone oxidoreductase 1 (NQO1)high catalase (CAT)low therapeutic window for the use of NQO1 bioactive drug β-lapachone (β-Lap) is first identified in endometrial cancer (EC). Accompanied by NADH depletion, NQO1 catalyzes β-Lap to produce excess H2 O2 and initiate oxidative stress, which selectively suppress NQO1high EC cell proliferation, induce DNA double-strand breaks, and promote apoptosis. Moreover, shRNA-mediated NQO1 knockdown or dicoumarol rescues NQO1high EC cells from β-Lap-induced cytotoxicity. Arginine-glycine-aspartic acid (RGD)-functionalized iron-based metal-organic frameworks (MOF(Fe)) further promote the conversion of the accumulated H2 O2 into highly oxidative ·OH, which in turn, exacerbates the oxidative damage to RGD-positive target cells. Furthermore, mitophagy inhibition by Mdivi-1 blocks a powerful antioxidant defense approach, ultimately ensuring the anti-tumor efficacy of stepwise-amplified reactive oxygen species signals. The tumor growth inhibition rate (TGI) is about 85.92%. However, the TGI of MOF(Fe)-based synergistic antitumor therapy decreases to only 50.46% in NQO1-deficient KLE tumors. Tumor-specific chemotherapy and CDT-triggered therapeutic modality present unprecedented therapeutic benefits in treating NQO1high EC.

Inclusion complex of O-allyl-lawsone with 2-hydroxypropyl-β-cyclodextrin: Preparation, physical characterization, antiparasitic and antifungal activity

The subclass naphthoquinone represents a substance group containing several compounds with important activities against various pathogenic microorganisms. Accordingly, we evaluated O-allyl-lawsone (OAL) antiparasitic and antifungal activity free and encapsulated in 2-hydroxypropyl-β-cyclodextrin (OAL MKN) against Trypanosoma cruzi and Sporothrix spp. OAL and OAL MKN were synthesized and characterized by physicochemical methods. The IC₅₀ values of OAL against T. cruzi were 2.4 µM and 96.8 µM, considering epimastigotes and trypomastigotes, respectively. At the same time, OAL MKN exhibited a lower IC₅₀ value (0.5 µM) for both trypanosome forms and low toxicity for mammalian cells. Additionally, the encapsulation showed a selectivity index approximately 240 times higher than that of benznidazole. Regarding antifungal activity, OAL and OAL MKN inhibited Sporothrix brasiliensis growth at 16 µM, while Sporothrix schenckii was inhibited at 32 µM. OAL MKN also exhibited higher selectivity toward fungus than mammalian cells. In conclusion, we described the encapsulation of O-allyl-lawsone in 2-hydroxypropyl-β-cyclodextrin, increasing the antiparasitic activity compared with the free form and reducing the cytotoxicity and increasing the selectivity towardSporothrix yeasts and the T. cruzi trypomastigote form. This study highlights the potential development of this inclusion complex as an antiparasitic and antifungal agent to treat neglected diseases.

Expanding Transition Metal-Mediated Bioorthogonal Decaging to Include C-C Bond Cleavage Reactions

The ability to control the activation of prodrugs by transition metals has been shown to have great potential for controlled drug release in cancer cells. However, the strategies developed so far promote the cleavage of C-O or C-N bonds, which limits the scope of drugs to only those that present amino or hydroxyl groups. Here, we report the decaging of an ortho-quinone prodrug, a propargylated β-lapachone derivative, through a palladium-mediated C-C bond cleavage. The reaction's kinetic and mechanistic behavior was studied under biological conditions along with computer modeling. The results indicate that palladium (II) is the active species for the depropargylation reaction, activating the triple bond for nucleophilic attack by a water molecule before the C-C bond cleavage takes place. Palladium iodide nanoparticles were found to efficiently trigger the C-C bond cleavage reaction under biocompatible conditions. In drug activation assays in cells, the protected analogue of β-lapachone was activated by nontoxic amounts of nanoparticles, which restored drug toxicity. The palladium-mediated ortho-quinone prodrug activation was further demonstrated in zebrafish tumor xenografts, which resulted in a significant anti-tumoral effect. This work expands the transition-metal-mediated bioorthogonal decaging toolbox to include cleavage of C-C bonds and payloads that were previously not accessible by conventional strategies.

Implantable Devices for the Treatment of Breast Cancer

Breast cancer is one of the leading causes of death in the female population worldwide. Standard treatments such as chemotherapy show noticeable results. However, along with killing cancer cells, it causes systemic toxicity and apoptosis of the nearby healthy cells, therefore patients must endure side effects during the treatment process. Implantable drug delivery devices that enhance therapeutic efficacy by allowing localized therapy with programmed or controlled drug release can overcome the shortcomings of conventional treatments. An implantable device can be composed of biopolymer materials, nanocomposite materials, or a combination of both. This review summarizes the recent research and current state-of-the art in these types of implantable devices and gives perspective for future directions.

β-Lapachone Selectively Kills Hepatocellular Carcinoma Cells by Targeting NQO1 to Induce Extensive DNA Damage and PARP1 Hyperactivation

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death globally. Currently there is a lack of tumor-selective and efficacious therapies for hepatocellular carcinoma. β-Lapachone (ARQ761 in clinical form) selectively kill NADPH: quinone oxidoreductase 1 (NQO1)-overexpressing cancer cells. However, the effect of β-Lapachone on HCC is virtually unknown. In this study, we found that relatively high NQO1 and low catalase levels were observed in both clinical specimens collected from HCC patients and HCC tumors from the TCGA database. β-Lapachone treatment induced NQO1-selective killing of HCC cells and caused ROS formation and PARP1 hyperactivation, resulting in a significant decrease in NAD+ and ATP levels and a dramatic increase in double-strand break (DSB) lesions over time in vitro. Administration of β-Lapachone significantly inhibited tumor growth and prolonged survival in a mouse xenograft model in vivo. Our data suggest that NQO1 is an ideal potential biomarker, and relatively high NQO1:CAT ratios in HCC tumors but low ratios in normal tissues offer an optimal therapeutic window to use β-Lapachone. This study provides novel preclinical evidence for β-Lapachone as a new promising chemotherapeutic agent for use in NQO1-positive HCC patients.

Imaging and Characterization of Sustained Gadolinium Nanoparticle Release from Next Generation Radiotherapy Biomaterial

Smart radiotherapy biomaterials (SRBs) present a new opportunity to enhance image-guided radiotherapy while replacing routinely used inert radiotherapy biomaterials like fiducials. In this study the potential of SRBs loaded with gadolinium-based nanoparticles (GdNPs) is investigated for magnetic resonance imaging (MRI) contrast. GdNP release from SRB is quantified and modelled for accurate prediction. SRBs were manufactured similar to fiducials, with a cylindrical shell consisting of poly(lactic-co-glycolic) acid (PLGA) and a core loaded with GdNPs. Magnetic resonance imaging (MRI) contrast was investigated at 7T in vitro (in agar) and in vivo in subcutaneous tumors grown with the LLC1 lung cancer cell line in C57/BL6 mice. GdNPs were quantified in-phantom and in tumor and their release was modelled by the Weibull distribution. Gd concentration was linearly fitted to the R₁ relaxation rate with a detection limit of 0.004 mmol/L and high confidence level (R² = 0.9843). GdNP loaded SRBs in tumor were clearly visible up to at least 14 days post-implantation. Signal decrease during this time showed GdNP release in vivo, which was calculated as 3.86 ± 0.34 µg GdNPs release into the tumor. This study demonstrates potential and feasibility for SRBs with MRI-contrast, and sensitive GdNP quantification and release from SRBs in a preclinical animal model. The feasibility of monitoring nanoparticle (NP) concentration during treatment, allowing dynamic quantitative treatment planning, is also discussed.

Bioanalytical method development and validation of a liquid chromatography-tandem mass spectrometry method for determination of β-lapachone in human plasma

The purpose of this work was to develop and validate a rapid, sensitive and robust liquid chromatography tandem mass spectrometric method for the quantification of β-lapachone in human plasma and to use that method to analyze human clinical samples. Sample preparation for the developed method involved liquid-liquid extraction using ethyl acetate for extraction of β-lapachone and cryptotanshinone (internal standard) from human plasma. Chromatographic resolution was achieved on a Kinetex C18 column using a gradient elution and a chromatographic flow rate of 0.5 mL/min. The retention times of β-lapachone and cryptotanshinone were 1.98 and 2.28 min, respectively, and the method had a total run time of 4 min. Bioanalytical method validation was conducted in accordance with the United States Food and Drug Administration regulatory guidelines. The method was validated over 2 calibration ranges in order to support high- and low-dose clinical studies. Calibration curve-1 covered the range of 0.25-50 ng/mL and calibration curve-2 covered the range of 50-2000 ng/mL. The method was determined to be accurate (percent relative errors between -1.07 to 5.36 %), precise (percent relative standard deviations less than 7.4), and sensitive (LLOQ 0.25 ng/mL). β-lapachone was determined to be stable (% change from time = 0 between -11.6 and 12.6 %) across the autosampler, benchtop, freeze/thaw and long-term (63 days) stability studies. The validated bioanalytical method was employed to determine β-lapachone concentrations in human plasma samples from a clinical study.

Synthesis and biological evaluation of β-lapachone and nor-β-lapachone complexes with 2-hydroxypropyl-β-cyclodextrin as trypanocidal agents

We study βLAP and its derivative nor-β-Lapachone (NβL) complexes with 2-hydroxypropyl-β-cyclodextrin to increase the solubility and bioavailability. The formation of true inclusion complexes between βLAP or NβL in 2-HP-β-CD in solid solution was characterization by FT-IR, DSC, powder X-ray was and was confirmed by one- and two-dimensional ¹H NMR experiments. Additionally, the biological activities of βLAP, NβL, ICβLAP, and ICNβL were investigated through trypanocidal assays with T. cruzi and cytotoxicity studies with mouse peritoneal macrophages. Originally, we tested these complexes against T. cruzi viability and observed higher biological activities and lower cytotoxicity when compared to βLAP and NβL. Thus, the complexation of βLAP and NβL with 2-HP-β-CD increases the drug solubility, in addition vectorization was observed, increasing the biological activity against epimastigotes and trypomastigotes T. cruzi forms. Reduced the toxicity of the compounds against mammalian cells. In addition, the selectivity indices higher of the inclusion complexes comparing to substance free and those of benznidazole.

Delivery of Nanoparticle-Based Radiosensitizers for Radiotherapy Applications

Nanoparticle-based radiosensitization of cancerous cells is evolving as a favorable modality for enhancing radiotherapeutic ratio, and as an effective tool for increasing the outcome of concomitant chemoradiotherapy. Nevertheless, delivery of sufficient concentrations of nanoparticles (NPs) or nanoparticle-based radiosensitizers (NBRs) to the targeted tumor without or with limited systemic side effects on healthy tissues/organs remains a challenge that many investigators continue to explore. With current systemic intravenous delivery of a drug, even targeted nanoparticles with great prospect of reaching targeted distant tumor sites, only a portion of the administered NPs/drug dosage can reach the tumor, despite the enhanced permeability and retention (EPR) effect. The rest of the targeted NPs/drug remain in systemic circulation, resulting in systemic toxicity, which can decrease the general health of patients. However, the dose from ionizing radiation is generally delivered across normal tissues to the tumor cells (especially external beam radiotherapy), which limits dose escalation, making radiotherapy (RT) somewhat unsafe for some diseased sites despite the emerging development in RT equipment and technologies. Since radiation cannot discriminate healthy tissue from diseased tissue, the radiation doses delivered across healthy tissues (even with nanoparticles delivered via systemic administration) are likely to increase injury to normal tissues by accelerating DNA damage, thereby creating free radicals that can result in secondary tumors. As a result, other delivery routes, such as inhalation of nanoparticles (for lung cancers), localized delivery via intratumoral injection, and implants loaded with nanoparticles for local radiosensitization, have been studied. Herein, we review the current NP delivery techniques; precise systemic delivery (injection/infusion and inhalation), and localized delivery (intratumoral injection and local implants) of NBRs/NPs. The current challenges, opportunities, and future prospects for delivery of nanoparticle-based radiosensitizers are also discussed.

Enzyme responsive drug delivery systems in cancer treatment

Recent technological approaches in drug delivery have attracted scientist interest for improving therapeutic index of medicines and drug compliance. One of the powerful strategies to control the transportation of drugs is implementation of intelligent stimuli-responsive drug delivery system (DDS). In this regard, tumor tissues with unique characteristics including leaky vasculature and diverse enzyme expression profiles facilitate the development of efficient enzyme-responsive nanoscale delivery systems. Based on the stimuli nature (physical, chemical and biological), these systems can be categorized into three groups according to the nature of trigger initiating the drug release. Enzymes are substantial constituents of the biotechnology toolbox offering promising capabilities and ideal characteristics to accelerate chemical reactions. Nanoparticles which have the ability to trigger their cargo release in the presence of specific enzymes are fabricated implementing fascinating physico-chemical properties of different materials in a nanoscale dimension. In order to reduce the adverse effects of the therapeutic agents, nanocarriers can be utilized and modified with enzyme-labile linkages to provide on-demand enzyme-responsive drug release. In the current review, we give an overview of drug delivery systems which can deliver drugs to the tumor microenvironment and initiate the drug release in response to specific enzymes highly expressed in particular tumor tissues. This strategy offers a versatile platform for intelligent drug release at the site of action.

The improved antitumor efficacy of continuous intratumoral chemotherapy with cisplatin-loaded implants for the treatment of sarcoma 180 tumor-bearing mice

Cisplatin is the most commonly used antitumor drug in the chemotherapy of a variety of malignancies. However, the severe side effects and drug resistance limit its clinical application. The aim of this study was to develop PLGA-based cisplatin-loaded implants and evaluate the antitumor efficacy of continuous intratumoral chemotherapy with the implants. The cisplatin-loaded implants were prepared by the direct compression method and characterized regarding drug content, micromorphology, in vitro and in vivo drug release profiles. Furthermore, the antitumor activity of the implants was conducted in sarcoma 180 tumor-bearing mice. The SEM images showed smooth surface of the implants and the mean drug content of the tested implants was (37.7% ± 0.5%, w/w). Both in vitro and in vivo release profiles of the implants were characterized by initial burst release followed by the sustained-release of cisplatin. Intratumoral implantation of the cisplatin-loaded implants could effectively inhibit the tumor growth. Additionally, intratumoral chemotherapy with the implants significantly reduced the systemic toxicity compared with intravenous injection of cisplatin. It is worth noting that an increase in the dose of the implants led to a higher tumor suppression rate without additional systemic toxicity. These results demonstrated that cisplatin-loaded implants enhanced the antitumor efficacy and reduced the dose-related side effects in sarcoma 180 tumor-bearing mice.

NQO1-dependent, Tumor-selective Radiosensitization of Non-small Cell Lung Cancers

PURPOSE

Development of tumor-specific therapies for the treatment of recalcitrant non-small cell lung cancers (NSCLC) is urgently needed. Here, we investigated the ability of β-lapachone (β-lap, ARQ761 in clinical form) to selectively potentiate the effects of ionizing radiation (IR, 1-3 Gy) in NSCLCs that overexpress NAD(P)H:Quinone Oxidoreductase 1 (NQO1).

EXPERIMENTAL DESIGN

The mechanism of lethality of low-dose IR in combination with sublethal doses of β-lap was evaluated in NSCLC lines in vitro and validated in subcutaneous and orthotopic xenograft models in vivo. Pharmacokinetics and pharmacodynamics (PK/PD) studies comparing single versus cotreatments were performed to validate therapeutic efficacy and mechanism of action.

RESULTS

β-Lap administration after IR treatment hyperactivated PARP, greatly lowered NAD⁺/ATP levels, and increased double-strand break (DSB) lesions over time in vitro. Radiosensitization of orthotopic, as well as subcutaneous, NSCLCs occurred with high apparent cures (>70%), even though 1/8 β-lap doses reach subcutaneous versus orthotopic tumors. No methemoglobinemia or long-term toxicities were noted in any normal tissues, including mouse liver that expresses the highest level of NQO1 (∼12 units) of any normal tissue. PK/PD responses confirm that IR + β-lap treatments hyperactivate PARP activity, greatly lower NAD⁺/ATP levels, and dramatically inhibit DSB repair in exposed NQO1⁺ cancer tissue, whereas low NQO1 levels and high levels of catalase in associated normal tissue were protective.

CONCLUSIONS

Our data suggest that combination of sublethal doses of β-lap and IR is a viable approach to selectively treat NQO1-overexpressing NSCLC and warrant a clinical trial using low-dose IR + β-lap against patients with NQO1⁺ NSCLCs.

NQO1 is Required for β-Lapachone-Mediated Downregulation of Breast-Cancer Stem-Cell Activity

Cancer stem cells (CSCs) exhibit self-renewal activity and give rise to other cell types in tumors. Due to the infinite proliferative potential of CSCs, drugs targeting these cells are necessary to completely inhibit cancer development. The β-lapachone (bL) compound is widely used to treat cancer development; however, its effect on cancer stem cells remain elusive. Thus, we investigated the effect of bL on mammosphere formation using breast-cancer stem-cell (BCSC) marker-positive cells, MDA-MB-231. MDA-MB-231 cells, which are negative for reduced nicotinamide adenine dinucleotide phosphate (NAD(P)H):quinone oxidoreductase (NQO1) expression, were constructed to stably express NQO1 (NQO1 stable cells). The effect of bL on these cells was evaluated by wound healing and Transwell cell-culture chambers, ALDEFLUOR assay, and mammosphere formation assay. Here, we show that bL inhibited the proliferative ability of mammospheres derived from BCSC marker-positive cells, MDA-MB-231, in an NQO1-dependent manner. The bL treatment efficiently downregulated the expression level of BCSC markers cluster of differentiation 44 (CD44), aldehyde dehydrogenase 1 family member A1 (ALDH1A1), and discs large (DLG)-associated protein 5 (DLGAP5) that was recently identified as a stem-cell proliferation marker in both cultured cells and mammosphered cells. Moreover, bL efficiently downregulated cell proliferation and migration activities. These results strongly suggest that bL could be a therapeutic agent for targeting breast-cancer stem-cells with proper NQO1 expression.

Phase 1 study of ARQ 761, a β-lapachone analogue that promotes NQO1-mediated programmed cancer cell necrosis

BACKGROUND

NAD(P)H:quinone oxidoreductase 1 (NQO1) is a two-electron oxidoreductase expressed in multiple tumour types. ARQ 761 is a β-lapachone (β-lap) analogue that exploits the unique elevation of NQO1 found in solid tumours to cause tumour-specific cell death.

METHODS

We performed a 3+3 dose escalation study of 3 schedules (weekly, every other week, 2/3 weeks) of ARQ 761 in patients with refractory advanced solid tumours. Tumour tissue was analysed for NQO1 expression. After 20 patients were analysed, enrolment was restricted to patients with NQO1-high tumours (H-score ≥ 200).

RESULTS

A total of 42 patients were treated. Median number of prior lines of therapy was 4. Maximum tolerated dose was 390 mg/m² as a 2-h infusion every other week. Dose-limiting toxicity was anaemia. The most common treatment-related adverse events were anaemia (79%), fatigue (45%), hypoxia (33%), nausea (17%), and vomiting (17%). Transient grade 3 hypoxia, reflecting possible methemoglobinaemia, occurred in 26% of patients. Among 32 evaluable patients, best response was stable disease (n = 12); 6 patients had tumour shrinkage. There was a trend towards improved efficacy in NQO1-high tumours (P = 0.06).

CONCLUSIONS

ARQ 761 has modest single-agent activity, which appears associated with tumour NQO1 expression. Principal toxicities include anaemia and possible methemoglobinaemia.

Characterization and antitumor efficacy of poly(L-lactid acid)-based etoposide-loaded implants

Etoposide is widely used in the chemotherapy of a variety of malignancies. But the strong lipophilicity, poor bioavailability, and severe side effects of etoposide limit its clinical application. The aim of this study was to develop sustained-release etoposide-loaded implants and evaluate antitumor activity of the implants after intratumoral implantation. We prepared the implants containing etoposide, poly(L-lactid acid) and polyethylene glycol 4000 by the direct compression method. The implants were characterized regarding drug-excipient compatibility, content uniformity, morphology, sterility, in vitro, and in vivo release profiles. Then the antitumor activity of the implants was tested in xenograft model of A549 human non-small cell lung cancer. SEM images displayed smooth surface of the implant and indicated that etoposide was homogeneously dispersed in the polymeric matrix. The results of content uniformity met the requirements of the Chinese Pharmacopoeia. Both in vitro and in vivo release profiles of the implants were characterized by high burst release followed by sustained release of etoposide. Intratumoral implantation of etoposide-loaded implants could efficiently delay the tumor growth. Furthermore, increasing the dose of implants led to higher tumor suppression rate without adding systemic toxicity. These results indicated that etoposide-loaded implants have significant antitumor efficacy in xenograft model without dose-limiting side effects and they possess a strong potential to be used as an intratumoral chemotherapy option for lung cancer treatment.

Enhanced antitumor efficacy of poly(D,L-lactide-co-glycolide)-based methotrexate-loaded implants on sarcoma 180 tumor-bearing mice

Purpose

Methotrexate is widely used in chemotherapy for a variety of malignancies. However, severe toxicity, poor pharmacokinetics, and narrow safety margin of methotrexate limit its clinical application. The aim of this study was to develop sustained-release methotrexate-loaded implants and evaluate antitumor activity of the implants after intratumoral implantation.

Materials and methods

We prepared the implants containing methotrexate, poly(D,L-lactide-co-glycolide), and polyethylene glycol 4000 with the melt-molding technique. The implants were characterized with regards to drug content, morphology, in vitro, and in vivo release profiles. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were carried out to investigate the physicochemical properties of the implants. Furthermore, the antitumor activity of the implants was tested in a sarcoma 180 mouse model.

Results

The implants were prepared as solid rods. Scanning electron microscopy images showed a smooth surface of the implant, suggesting that methotrexate was homogeneously dispersed in the polymeric matrix. The results of DSC and FTIR indicated that no significant interaction between methotrexate and the polymer was observed in the implants. Both in vitro and in vivo release profiles of the implants were characterized by burst release followed by sustained release of methotrexate. Intratumoral implantation of methotrexate-loaded implants could efficiently delay tumor growth. Moreover, an increase in the dose of implants led to a higher tumor suppression rate without additional systemic toxicity.

Conclusion

These results demonstrate that methotrexate-loaded implants had significant antitumor efficacy in a sarcoma 180 mouse model without dose-limiting side effects, and suggest that the implants could be potentially applied as an intratumoral delivery system to treat cancer.

Using a novel NQO1 bioactivatable drug, beta-lapachone (ARQ761), to enhance chemotherapeutic effects by metabolic modulation in pancreatic cancer

Novel, tumor-selective therapies are needed to increase the survival rate of pancreatic cancer patients. K-Ras-mutant-driven NAD(P)H:quinone oxidoreductase 1 (NQO1) is over-expressed in pancreatic tumor versus associated normal tissue, while catalase expression is lowered compared to levels in associated normal pancreas tissue. ARQ761 undergoes a robust, futile redox cycle in NQO1+ cancer cells, producing massive hydrogen peroxide (H2 O2 ) levels; normal tissues are spared by low NQO1 and high catalase expression. DNA damage created by ARQ761 in pancreatic cancer cells "hyperactivates" PARP1, causing metabolic catastrophe and NAD ± keresis cell death. NQO1: catalase levels (high in tumor, low in normal tissue) are an attractive therapeutic window to treat pancreatic cancer. Based on a growing body of literature, we are leading a clinical trial to evaluate the combination of ARQ761 and chemotherapy in patients with pancreatic cancer.

Lysosome-oriented, dual-stage pH-responsive polymeric micelles for β-Lapachone delivery

β-Lapachone (β-lap), a novel anticancer agent, is bioactivated by NADP(H):quinone oxidoreductase 1 (NQO1), an enzyme over-expressed in numerous tumors, including lung, pancreas, breast, and prostate cancers. Fast renal clearance and methemaglobinemia / hemolytic side-effects from the clinical formulation (β-lap-hydroxyl propyl-β-cyclodextrin complex) hindered its clinical translation. Here, we investigated a dual model pH responsive polymers for β-lap delivery. Three pH-sensitive linkages, including acylhydrazone, ketal and imine bonds for β-lap prodrug syntheses result in an aryl imine linkage the most optimal linkage. The conversion to β-lap was 2.8%, 4.5% and 100% at pH 7.4, 6.5 and 5.0 in 8 h, respectively. β-lap aryl imine prodrug conjugated ultra pH-sensitive (UPS) polymer reached high β-lap loading density (8.3%) and exhibited dual-stages responsiveness to pH variation. In pHs under pHt, at stage I, micelle immediately dissociation and subsequently entering stage II, micelles start quickly release β-lap. In vitro release study showed that the micelles constantly release β-lap (14.9 ± 0.1%) at pHs above pHt in 72 h, whereas boosted release of β-lap (79.4 ± 1.2%) at pH 5.0. Micelle intracellular distribution predominantly in the lysosome organelle guaranteed their pH responsive dissociation and subsequently β-lap controlled release. The M-P micelles retained NQO1-dependent cytotoxicity in A549 lung cancer cells, similar to free drug in both efficacy and mechanism of cell death. The lysosome-oriented dual-stage ultra pH responsive β-lap prodrug micelles potentially offer an alternative nanotherapeutic strategy for lung, as well as other NQO1+ cancer therapies.

PRX1 knockdown potentiates vitamin K3 toxicity in cancer cells: a potential new therapeutic perspective for an old drug

Background

Many promising anticancer molecules are abandoned during the course from bench to bedside due to lack of clear-cut efficiency and/or severe side effects. Vitamin K3 (vitK3) is a synthetic naphthoquinone exhibiting significant in vitro and in vivo anticancer activity against multiple human cancers, and has therapeutic potential when combined with other anticancer molecules. The major mechanism for the anticancer activity of vitK3 is the generation of cytotoxic reactive oxygen species (ROS). We thus reasoned that a rational redox modulation of cancer cells could enhance vitK3 anticancer efficiency.

Methods

Cancer cell lines with peroxiredoxin 1 (PRX1) gene transiently or stably knocked-down and corresponding controls were exposed to vitK3 as well as a set of anticancer molecules, including vinblastine, taxol, doxorubicin, daunorubicin, actinomycin D and 5-fluorouracil. Cytotoxic effects and cell death events were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)-based assay, cell clonogenic assay, measurement of mitochondrial membrane potential and annexin V/propidium iodide double staining. Global ROS accumulation and compartment-specific H₂O₂ generation were determined respectively by a redox-sensitive chemical probe and H₂O₂-sensitive sensor HyPer. Oxidation of endogenous antioxidant proteins including TRX1, TRX2 and PRX3 was monitored by redox western blot.

Results

We observed that the PRX1 knockdown in HeLa and A549 cells conferred enhanced sensitivity to vitK3, reducing substantially the necessary doses to kill cancer cells. The same conditions (combination of vitK3 and PRX1 knockdown) caused little cytotoxicity in non-cancerous cells, suggesting a cancer-cell-selective property. Increased ROS accumulation had a crucial role in vitK3-induced cell death in PRX1 knockdown cells. The use of H₂O₂-specific sensors HyPer revealed that vitK3 lead to immediate accumulation of H₂O₂ in the cytosol, nucleus, and mitochondrial matrix. PRX1 silencing significantly up-regulated mRNA and protein levels of NRH:quinone oxidoreductase 2, which was partially responsible for vitK3-induced ROS accumulation and consequent cell death.

Conclusion

Our data suggest that PRX1 inactivation could represent an interesting strategy to enhance cancer cell sensitivity to vitK3, providing a potential new therapeutic perspective for this old molecule. Conceptually, a combination of drugs that modulate intracellular redox states and drugs that operate through the generation of ROS could be a new therapeutic strategy for cancer treatment.

Implications of NQO1 in cancer therapy

NAD(P)H

quinone oxidoreductase (NQO1), an obligatory two-electron reductase, is a ubiquitous cytosolic enzyme that catalyzes the reduction of quinone substrates. The NQO1- mediated two-electron reduction of quinones can be either chemoprotection/detoxification or a chemotherapeutic response, depending on the target quinones. When toxic quinones are reduced by NQO1, they are conjugated with glutathione or glucuronic acid and excreted from the cells. Based on this protective effect of NQO1, the use of dietary compounds to induce the expression of NQO1 has emerged as a promising strategy for cancer prevention. On the other hand, NQO1-mediated two-electron reduction converts certain quinone compounds (such as mitomycin C, E09, RH1 and -lapachone) to cytotoxic agents, leading to cell death. It has been known that NQO1 is expressed at high levels in numerous human cancers, including breast, colon, cervix, lung, and pancreas, as compared with normal tissues. This implies that tumors can be preferentially damaged relative to normal tissue by cytotoxic quinone drugs. Importantly, NQO1 has been shown to stabilize many proteins, including p53 and p33ING1b, by inhibiting their proteasomal degradation. This review will summarize the biological roles of NQO1 in cancer, with emphasis on recent findings and the potential of NQO1 as a therapeutic target for the cancer therapy.

Preclinical Pharmacokinetic Evaluation of β-Lapachone: Characteristics of Oral Bioavailability and First-Pass Metabolism in Rats

β-Lapachone has drawn increasing attention as an anti-inflammatory and anti-cancer drug. However, its oral bioavailability has not been yet assessed, which might be useful to develop efficient dosage forms possibly required for non-clinical and clinical studies and future market. The aim of the present study was thus to investigate pharmacokinetic properties of β-lapachone as well as its first-pass metabolism in the liver, and small and large intestines after oral administration to measure the absolute bioavailability in rats. A sensitive HPLC method was developed to evaluate levels of β-lapachone in plasma and organ homogenates. The drug degradation profiles were examined in plasma to assess the stability of the drug and in liver and intestinal homogenates to evaluate first-pass metabolism. Pharmacokinetic profiles were obtained after oral and intravenous administration of β-lapachone at doses of 40 mg/kg and 1.5 mg/kg, respectively. The measured oral bioavailability of β-lapachone was 15.5%. The considerable degradation of β-lapachone was seen in the organ homogenates but the drug was quite stable in plasma. In conclusion, we suggest that the fairly low oral bioavailability of β-lapachone may be resulted from the first-pass metabolic degradation of β-lapachone in the liver, small and large intestinal tracts and its low aqueous solubility.

New potential for enhancing concomitant chemoradiotherapy with FDA approved concentrations of cisplatin via the photoelectric effect

We predict, for the first time, that by using United States Food and Drug Administration approved concentrations of cisplatin, major radiosensitization may be achieved via photoelectric mechanism during concomitant chemoradiotherapy (CCRT). Our analytical calculations estimate that radiotherapy (RT) dose to cancer cells may be enhanced via this mechanism by over 100% during CCRT. The results proffer new potential for significantly enhancing CCRT via an emerging clinical scenario, where the cisplatin is released in-situ from RT biomaterials loaded with cisplatin nanoparticles.

Mechanistic studies of cancer cell mitochondria- and NQO1-mediated redox activation of beta-lapachone, a potentially novel anticancer agent

Beta-lapachone (beta-Lp) derived from the Lapacho tree is a potentially novel anticancer agent currently under clinical trials. Previous studies suggested that redox activation of beta-Lp catalyzed by

NAD(P)H

quinone oxidoreductase 1 (NQO1) accounted for its killing of cancer cells. However, the exact mechanisms of this effect remain largely unknown. Using chemiluminescence and electron paramagnetic resonance (EPR) spin-trapping techniques, this study for the first time demonstrated the real-time formation of ROS in the redox activation of beta-lapachone from cancer cells mediated by mitochondria and NQO1 in melanoma B16-F10 and hepatocellular carcinoma HepG2 cancer cells. ES936, a highly selective NQO1 inhibitor, and rotenone, a selective inhibitor of mitochondrial electron transport chain (METC) complex I were found to significantly block beta-Lp meditated redox activation in B16-F10 cells. In HepG2 cells ES936 inhibited beta-Lp-mediated oxygen radical formation by ~80% while rotenone exerted no significant effect. These results revealed the differential contribution of METC and NQO1 to beta-lapachone-induced ROS formation and cancer cell killing. In melanoma B16-F10 cells that do not express high NQO1 activity, both NOQ1 and METC play a critical role in beta-Lp redox activation. In contrast, in hepatocellular carcinoma HepG2 cells expressing extremely high NQO1 activity, redox activation of beta-Lp is primarily mediated by NQO1 (METC plays a minor role). These findings will contribute to our understanding of how cancer cells are selectively killed by beta-lapachone and increase our ability to devise strategies to enhance the anticancer efficacy of this potentially novel drug while minimizing its possible adverse effects on normal cells.

Tumor-selective, futile redox cycle-induced bystander effects elicited by NQO1 bioactivatable radiosensitizing drugs in triple-negative breast cancers

AIMS

β-Lapachone (β-lap), a novel radiosensitizer with potent antitumor efficacy alone, selectively kills solid cancers that over-express

NAD(P)H

quinone oxidoreductase 1 (NQO1). Since breast or other solid cancers have heterogeneous NQO1 expression, therapies that reduce the resistance (e.g., NQO1(low)) of tumor cells will have significant clinical advantages. We tested whether NQO1-proficient (NQO1(+)) cells generated sufficient hydrogen peroxide (H2O2) after β-lap treatment to elicit bystander effects, DNA damage, and cell death in neighboring NQO1(low) cells.

RESULTS

β-Lap showed NQO1-dependent efficacy against two triple-negative breast cancer (TNBC) xenografts. NQO1 expression variations in human breast cancer patient samples were noted, where ~60% cancers over-expressed NQO1, with little or no expression in associated normal tissue. Differential DNA damage and lethality were noted in NQO1(+) versus NQO1-deficient (NQO1(-)) TNBC cells and xenografts after β-lap treatment. β-Lap-treated NQO1(+) cells died by programmed necrosis, whereas co-cultured NQO1(-) TNBC cells exhibited DNA damage and caspase-dependent apoptosis. NQO1 inhibition (dicoumarol) or H2O2 scavenging (catalase [CAT]) blocked all responses. Only NQO1(-) cells neighboring NQO1(+) TNBC cells responded to β-lap in vitro, and bystander effects correlated well with H2O2 diffusion. Bystander effects in NQO1(-) cells in vivo within mixed 50:50 co-cultured xenografts were dramatic and depended on NQO1(+) cells. However, normal human cells in vitro or in vivo did not show bystander effects, due to elevated endogenous CAT levels. Innovation and Conclusions: NQO1-dependent bystander effects elicited by NQO1 bioactivatable drugs (β-lap or deoxynyboquinone [DNQ]) likely contribute to their efficacies, killing NQO1(+) solid cancer cells and eliminating surrounding heterogeneous NQO1(low) cancer cells. Normal cells/tissue are protected by low NQO1:CAT ratios.

Targeted radiotherapy with gold nanoparticles: current status and future perspectives

Radiation therapy (RT) is the treatment of cancer and other diseases with ionizing radiation. The ultimate goal of RT is to destroy all the disease cells while sparing healthy tissue. Towards this goal, RT has advanced significantly over the past few decades in part due to new technologies including: multileaf collimator-assisted modulation of radiation beams, improved computer-assisted inverse treatment planning, image guidance, robotics with more precision, better motion management strategies, stereotactic treatments and hypofractionation. With recent advances in nanotechnology, targeted RT with gold nanoparticles (GNPs) is actively being investigated as a means to further increase the RT therapeutic ratio. In this review, we summarize the current status of research and development towards the use of GNPs to enhance RT. We highlight the promising emerging modalities for targeted RT with GNPs and the corresponding preclinical evidence supporting such promise towards potential clinical translation. Future prospects and perspectives are discussed.

Review of poly (ADP-ribose) polymerase (PARP) mechanisms of action and rationale for targeting in cancer and other diseases

Poly (ADP-ribose) polymerases (PARPs) are a family of related enzymes that share the ability to catalyze the transfer of ADP-ribose to target proteins. PARPs play an important role in various cellular processes, including modulation of chromatin structure, transcription, replication, recombination, and DNA repair. The role of PARP proteins in DNA repair is of particular interest, in view of the finding that certain tumors defective in homologous recombination mechanisms, may rely on PARP-mediated DNA repair for survival, and are sensitive to its inhibition. PARP inhibitors may also increase tumor sensitivity to DNA-damaging agents. Clinical trials of PARP inhibitors are investigating the utility of these approaches in cancer. The hyperactivation of PARP has also been shown to result in a specific programmed cell death pathway involving NAD+/ATP depletion, mu-calpain activation, loss of mitochondrial membrane potential, and the release of apoptosis inducing factor. Hyperactivation of the PARP pathway may be exploited to selectively kill cancer cells. Other PARP forms, including tankyrase 1 (PARP 5a), which plays an important role in enhancing telomere elongation by telomerase, have been found to be potential targets in cancer therapy. The PARP pathway and its inhibition thus offers a number of opportunities for therapeutic intervention in both cancer and other disease states.

β-Lapachone: a naphthoquinone with promising antischistosomal properties in mice

The activity of β-lapachone (3,4-dihydro-2,2-dimethyl-2H-naphthol[1,2-b]pyran-5,6-dione, β-lap) against different stages of Schistosoma mansoni was investigated in mice. Mice infected with 50 cercariae (BH strain) were intraperitoneally treated at a dose of 50 mg/kg for 5 consecutive days, starting on the 1st, 14th, 28th and 45th days after infection, to evaluate the effect of β-lap on skin schistosomula, lung schistosomula, young worms (before oviposition) and adult worms (after oviposition), respectively. All animals were euthanized 60 days after infection. β-Lap significantly reduced (p<0.001) the number of worms in 29.78%, 37.2%, 24.2% and 40.22% when administered during the phases of skin schistosomula, lung schistosomula, young worms and adult worms, respectively. Significant reduction was also achieved in terms of female burden. In all groups, there was significant reduction in the number of eggs and granulomas in the hepatic tissue. When the intervention was performed during the phase of adult worms, β-lap reduced the size of hepatic granulomas and changed the oogram pattern, lowering the percentage of immature eggs and increasing the percentage of mature and dead eggs. Our data indicate that β-lap has moderate antischistosomal properties. Its molecule may also be used as a prototype for synthesis of new naphthoquinone derivatives with potential schistosomicidal properties. Further studies with different formulations containing β-lap are needed to clearly establish the best dose and route of administration and its mechanism of action against schistosomes.

Polymeric implants for the delivery of green tea polyphenols

Polymeric implants (millirods) have been tested for local delivery of chemotherapeutic agents in cancer treatment. Modeling of drug release profiles is critical as it may provide theoretical insights on rational implant design. In this study, a biodegradable poly (ε-caprolactone) (PCL) polymeric implant delivery system was tested to deliver green tea polyphenols (GTPs), both in vitro and in vivo. Factors including polymer compositions, supplements, drug loads, and surface area of implants were investigated. Our data showed that GTPs were released from PCL implants continuously for long durations, and drug load was the main determining factor of GTPs release. Furthermore, rates of in vitro release and in vivo release in the rat model followed similar kinetics for up to 16 months. A mathematical model was deduced and discussed. GTP implants have the potential to be used systemically and locally at the tumor site as an alternative strategy.

Administration of the optimized β-Lapachone-poloxamer-cyclodextrin ternary system induces apoptosis, DNA damage and reduces tumor growth in a human breast adenocarcinoma xenograft mouse model

β-Lapachone (β-Lap) is a 1,2-orthonaphthoquinone that selectively induces cell death in human cancer cells through NAD(P)H:quinone oxidoreductase-1 (NQO1). NQO1 is overexpressed in a variety of tumors, as compared to normal adjacent tissue. However, the low solubility and non-specific distribution of β-Lap limit its suitability for clinical assays. We formulated β-Lap in an optimal random methylated-β-cyclodextrin/poloxamer 407 mixture (i.e., β-Lap ternary system) and, using human breast adenocarcinoma MCF-7 cells and immunodeficient mice, performed in vitro and in vivo evaluation of its anti-tumor effects on proliferation, cell cycle, apoptosis, DNA damage, and tumor growth. This ternary system is fluid at room temperature, gels over 29 °C, and provides a significant amount of drug, thus facilitating intratumoral delivery, in situ gelation, and the formation of a depot for time-release. Administration of β-Lap ternary system to MCF-7 cells induces an increase in apoptosis and DNA damage, while producing no changes in cell cycle. Moreover, in a mouse xenograft tumor model, intratumoral injection of the system significantly reduces tumor volume, while increasing apoptosis and DNA damage without visible toxicity to liver or kidney. These anti-tumoral effects and lack of visible toxicity make this system a promising new therapeutic agent for breast cancer treatment.

Anticancer efficacy and subcellular site of action investigated by real-time monitoring of cellular responses to localized drug delivery in single cells

Subcellular-targeted drug delivery has much potential to defeat infectious diseases and cancers. Medical and/or biochemical effects of drugs/bioactive molecules delivered to subcellular compartments and their subcellular sites of action need to be investigated but have not been explored. Here the subcellular location-dependent biochemical responses of a potent anticancer drug, β-lapachone (β-lap), is investigated by a reduced graphene oxide (rGO)-functionalized optical nanoprobe, which can deliver and simultaneously monitor the drug effects at nanoscales. For the first time, distinct oxidative responses and calcium alterations in three selected subcellular domains are observed and clearly pinpoint that the perinuclear region is the optimal subcellular site for β-lap to have the best anticancer efficacy. The results presented here provide not only scientific insights of subcellular drug-cell interaction that is not obtainable from conventional methods, but they also provide valuable knowledge for rational design of subcellular-targeted delivery or spatially resolved signal intervention.

Endoplasmic reticulum stress-induced JNK activation is a critical event leading to mitochondria-mediated cell death caused by β-lapachone treatment

Background

β-lapachone (β-lap) is a bioreductive agent that is activated by the two-electron reductase NAD(P)H quinone oxidoreductase 1 (NQO1). Although β-lap has been reported to induce apoptosis in various cancer types in an NQO1-dependent manner, the signaling pathways by which β-lap causes apoptosis are poorly understood.

Methodology/Principal Findings

β-lap-induced apoptosis and related molecular signaling pathways in NQO1-negative and NQO1-overexpressing MDA-MB-231 cells were investigated. Pharmacological inhibitors or siRNAs against factors involved in β-lap-induced apoptosis were used to clarify the roles played by such factors in β-lap-activated apoptotic signaling pathways. β-lap leads to clonogenic cell death and apoptosis in an NQO1- dependent manner. Treatment of NQO1-overexpressing MDA-MB-231 cells with β-lap causes rapid disruption of mitochondrial membrane potential, nuclear translocation of AIF and Endo G from mitochondria, and subsequent caspase-independent apoptotic cell death. siRNAs targeting AIF and Endo G effectively attenuate β-lap-induced clonogenic and apoptotic cell death. Moreover, β-lap induces cleavage of Bax, which accumulates in mitochondria, coinciding with the observed changes in mitochondria membrane potential. Pretreatment with Salubrinal (Sal), an endoplasmic reticulum (ER) stress inhibitor, efficiently attenuates JNK activation caused by β-lap, and subsequent mitochondria-mediated cell death. In addition, β-lap-induced generation and mitochondrial translocation of cleaved Bax are efficiently blocked by JNK inhibition.

Conclusions/Significance

Our results indicate that β-lap triggers induction of endoplasmic reticulum (ER) stress, thereby leading to JNK activation and mitochondria-mediated apoptosis. The signaling pathways that we revealed in this study may significantly contribute to an improvement of NQO1-directed tumor therapies.

Light effect on the stability of β-lapachone in solution: pathways and kinetics of degradation

OBJECTIVES

The purpose of this work was to study the chemical stability of the new antitumoral β-lapachone (βLAP) to determine the degradation pathway/s of the molecule and the degradation kinetics in addition to identifying several degradation products.

METHOD

Samples of βLAP in solution were stored under conditions of darkness and illumination at 40°C at which the pseudo-first order rate constants for the βLAP degradation were determined. Furthermore, drug degraded solutions were concentrated and purified using Sephadex LH-20 and preparative thin-layer chromatography and degradation products were identified by nuclear magnetic resonance spectroscopy.

KEY FINDINGS

The results revealed that βLAP shows two different degradation routes: hydrolysis in the dark and photolysis under the light. The βLAP exposure to light accelerated the drug degradation about 140 fold, compared with the samples stored in the absence of light. The hydrolysis produced hydroxylapachol as the main degradation product. The photolysis yielded phthalic acid, 6-hydroxy-3methylene-3H-isobenzofuran-1-one and a benzomacrolactone together with a complex mixture of other phthalate-derivatives such as 2-(2-carboxy-acetyl)-benzoic acid.

CONCLUSIONS

This study provides useful information for the development of βLAP dosage forms, their storage, manipulation and quality control.

Nanospheres-incorporated implantable hydrogel as a trans-tissue drug delivery system

The objective of this study is to investigate the anticancer efficacy of a drug delivery system comprised of gelatin hydrogel (jelly) containing cisplatin (CDDP)-loaded gelatin/poly(acrylic acid) nanoparticles by peritumoral implantation and to compare the treatment response between the implantation administration of the jelly and intravenous (i.v.) administration of the nanoparticles. It is found that the implantation of the jelly containing CDDP-loaded nanoparticles on tumor tissue exhibited significantly superior efficacy in impeding tumor growth and prolonging the lifetime of mice than that of i.v. injection of CDDP-loaded nanoparticles in a murine hepatoma H(22) cancer model. An in vivo biodistribution assay performed on tumor-bearing mice demonstrated that the jelly implant caused much higher concentration and retention of CDDP in tumor and lower CDDP accumulation in nontarget organs than that of i.v. injected nanoparticles. Immunohistochemical analysis demonstrated that the nanoparticles from the jelly can be distributed in tumor tissue not only by their diffusion but also by the vasculature in the implantation region into tumor interior, enabling CDDP to efficiently reach more viable cells of tumor compared with i.v. injected nanoparticles. Thus, nanoparticles for peritumoral chemotherapy are promising for higher treatment efficacy due to increased tumor-to-normal organ drug uptake ratios and improved drug penetration in tumors.

Modulating endogenous NQO1 levels identifies key regulatory mechanisms of action of β-lapachone for pancreatic cancer therapy

PURPOSE

Pancreatic cancer is the fourth leading cause of cancer-related deaths, in which the 5-year survival rate is less than 5%. Current standard of care therapies offer little selectivity and high toxicity. Novel, tumor-selective approaches are desperately needed. Although prior work suggested that β-lapachone (β-lap) could be used for the treatment of pancreatic cancers, the lack of knowledge of the compound's mechanism of action prevented optimal use of this agent.

EXPERIMENTAL DESIGN

We examined the role of NAD(P)H:quinone oxidoreductase-1 (NQO1) in β-lap-mediated antitumor activity, using a series of MIA PaCa-2 pancreatic cancer clones varying in NQO1 levels by stable shRNA knockdown. The antitumor efficacy of β-lap was determined using an optimal hydroxypropyl-β-cyclodextran (HPβ-CD) vehicle formulation in metastatic pancreatic cancer models.

RESULTS

β-Lap-mediated cell death required ∼90 enzymatic units of NQO1. Essential downstream mediators of lethality were as follows: (i) reactive oxygen species (ROS); (ii) single-strand DNA breaks induced by ROS; (iii) poly(ADP-ribose)polymerase-1 (PARP1) hyperactivation; (iv) dramatic NAD(+)/ATP depletion; and (v) programmed necrosis. We showed that 1 regimen of β-lap therapy (5 treatments every other day) efficaciously regressed and reduced human pancreatic tumor burden and dramatically extended the survival of athymic mice, using metastatic pancreatic cancer models.

CONCLUSIONS

Because NQO1 enzyme activities are easily measured and commonly overexpressed (i.e., >70%) in pancreatic cancers 5- to 10-fold above normal tissue, strategies using β-lap to efficaciously treat pancreatic cancers are indicated. On the basis of optimal drug formulation and efficacious antitumor efficacy, such a therapy should be extremely safe and not accompanied with normal tissue toxicity or hemolytic anemia.

Dimeric naphthoquinones, a novel class of compounds with prostate cancer cytotoxicity

OBJECTIVES

• To evaluate the cytotoxicity of dimeric naphthoquinones (BiQs) in prostate cancer cells. • To assess the interaction of dimeric naphthoquinones with common therapies including radiation and docetaxel.

MATERIALS AND METHODS

• The cytotoxicity of 12 different dimeric naphthoquinones was assessed in androgen-independent (PC-3, DU-145) and androgen-responsive (LNCaP, 22RV1) prostate cancer cell lines and in prostate epithelial cells (PrECs). • BiQ2 and BiQ11 were selected for determination of dose response, effects on colony formation and initial exploration into mechanism of action. • Synergistic effects with radiation and docetaxel were explored using colony-forming and MTT assays.

RESULTS

• At concentrations of 15µM, BiQ2, BiQ3, BiQ11, BiQ12, and BiQ15 demonstrated cytotoxicity in all prostate cancer cell lines. • Treatment with BiQs limited the ability of prostate cancer cells to form colonies in clonogenic assays. • Exposure of prostate cancer to BiQs increased cellular reactive oxygen species (ROS), decreased ATP production, and promoted apoptosis. • BiQ cytotoxicity was independent of NADP(H):quinone oxidoreductase 1 (NQO1) activity in PrECs, PC-3 and 22RV1, but not DU-145 cells. • Exposure of prostate cancer cells to radiation before treatment with BiQs increased their activity allowing for inhibitory effects well below the IC(50) s of these compounds in PrECs. • Co-administration of BiQs with docetaxel had minimal additive effects.

CONCLUSIONS

• Dimeric naphthoquinones represent a new class of compounds with prostate cancer cytotoxicity and synergistic effects with radiation. The cytotoxic effect of these agents is probably contributed to by the accumulation of ROS and mitochondrial dysfunction. • Further studies are warranted to better characterize this class of potential chemo-therapeutics.

Prostate cancer radiosensitization through poly(ADP-Ribose) polymerase-1 hyperactivation

The clinical experimental agent, β-lapachone (β-lap; Arq 501), can act as a potent radiosensitizer in vitro through an unknown mechanism. In this study, we analyzed the mechanism to determine whether β-lap may warrant clinical evaluation as a radiosensitizer. β-Lap killed prostate cancer cells by NAD(P)H:quinone oxidoreductase 1 (NQO1) metabolic bioactivation, triggering a massive induction of reactive oxygen species, irreversible DNA single-strand breaks (SSB), poly(ADP-ribose) polymerase-1 (PARP-1) hyperactivation, NAD(+)/ATP depletion, and μ-calpain-induced programmed necrosis. In combination with ionizing radiation (IR), β-lap radiosensitized NQO1(+) prostate cancer cells under conditions where nontoxic doses of either agent alone achieved threshold levels of SSBs required for hyperactivation of PARP-1. Combination therapy significantly elevated SSB level, γ-H2AX foci formation, and poly(ADP-ribosylation) of PARP-1, which were associated with ATP loss and induction of μ-calpain-induced programmed cell death. Radiosensitization by β-lap was blocked by the NQO1 inhibitor dicoumarol or the PARP-1 inhibitor DPQ. In a mouse xenograft model of prostate cancer, β-lap synergized with IR to promote antitumor efficacy. NQO1 levels were elevated in ∼60% of human prostate tumors evaluated relative to adjacent normal tissue, where β-lap might be efficacious alone or in combination with radiation. Our findings offer a rationale for the clinical utilization of β-lap (Arq 501) as a radiosensitizer in prostate cancers that overexpress NQO1, offering a potentially synergistic targeting strategy to exploit PARP-1 hyperactivation.