F14512, a polyamine-vectorized anti-cancer drug, currently in clinical trials exhibits a marked preclinical anti-leukemic activity

Polyamine-containing natural products: structure, bioactivity, and biosynthesis

Covering: 2005 to August, 2023Polyamine-containing natural products (NPs) have been isolated from a wide range of terrestrial and marine organisms and most of them exhibit remarkable and diverse activities, including antimicrobial, antiprotozoal, antiangiogenic, antitumor, antiviral, iron-chelating, anti-depressive, anti-inflammatory, insecticidal, antiobesity, and antioxidant properties. Their extraordinary activities and potential applications in human health and agriculture attract increasing numbers of studies on polyamine-containing NPs. In this review, we summarized the source, structure, classification, bioactivities and biosynthesis of polyamine-containing NPs, focusing on the biosynthetic mechanism of polyamine itself and representative polyamine alkaloids, polyamine-containing siderophores with catechol/hydroxamate/hydroxycarboxylate groups, nonribosomal peptide-(polyketide)-polyamine (NRP-(PK)-PA), and NRP-PK-long chain poly-fatty amine (lcPFAN) hybrid molecules.

Biosynthesis and engineering of the nonribosomal peptides with a C-terminal putrescine

The broad bioactivities of nonribosomal peptides rely on increasing structural diversity. Genome mining of the Burkholderiales strain Schlegelella brevitalea DSM 7029 leads to the identification of a class of dodecapeptides, glidonins, that feature diverse N-terminal modifications and a uniform putrescine moiety at the C-terminus. The N-terminal diversity originates from the wide substrate selectivity of the initiation module. The C-terminal putrescine moiety is introduced by the unusual termination module 13, the condensation domain directly catalyzes the assembly of putrescine into the peptidyl backbone, and other domains are essential for stabilizing the protein structure. Swapping of this module to another two nonribosomal peptide synthetases leads to the addition of a putrescine to the C-terminus of related nonribosomal peptides, improving their hydrophilicity and bioactivity. This study elucidates the mechanism for putrescine addition and provides further insights to generate diverse and improved nonribosomal peptides by introducing a C-terminal putrescine.

Doxorubicin and other anthracyclines in cancers: Activity, chemoresistance and its overcoming

Anthracyclines have been important and effective treatments against a number of cancers since their discovery. However, their use in therapy has been complicated by severe side effects and toxicity that occur during or after treatment, including cardiotoxicity. The mode of action of anthracyclines is complex, with several mechanisms proposed. It is possible that their high toxicity is due to the large set of processes involved in anthracycline action. The development of resistance is a major barrier to successful treatment when using anthracyclines. This resistance is based on a series of mechanisms that have been studied and addressed in recent years. This work provides an overview of the anthracyclines used in cancer therapy. It discusses their mechanisms of activity, toxicity, and chemoresistance, as well as the approaches used to improve their activity, decrease their toxicity, and overcome resistance.

Polyamine-Drug Conjugates: Do They Boost Drug Activity?

Over the past two decades, the strategy of conjugating polyamine tails with bioactive molecules such as anticancer and antimicrobial agents, as well as antioxidant and neuroprotective scaffolds, has been widely exploited to enhance their pharmacological profile. Polyamine transport is elevated in many pathological conditions, suggesting that the polyamine portion could improve cellular and subcellular uptake of the conjugate via the polyamine transporter system. In this review, we have presented a glimpse on the polyamine conjugate scenario, classified by therapeutic area, of the last decade with the aim of highlighting achievements and fostering future developments.

Nanomicelle-Microsphere Composite as a Drug Carrier to Improve Lung-Targeting Specificity for Lung Cancer

Lung cancer is the second-most common cancer and has the highest mortality among all cancer types. Nanoparticle (NP) drug delivery systems have been used to improve the therapeutic effectiveness of lung cancer, but rapid clearance and poor targeting limit their clinical utility. Here, we developed a nanomicelle-microsphere composite, in which doxorubicin (DOX) was loaded with spermine (Spm) modified poly (ethylene glycol)-poly(ε-caprolactone) (PEG-PCL) micelles, and then the nanomicelles were noncovalently adsorbed on the surface of poly (lactic-co-glycolic acid) (PLGA) microspheres. The attachment was confirmed by scanning electron microscopy and confocal microscopy. In vitro cell experiments, MTT assays and intracellular uptake assays were used to demonstrate the cytotoxicity and the cellular uptake of micelles in A549 cells. In vivo biodistribution studies were conducted, an orthotopic lung cancer implantation model based on C57BL/6 mice was established, and then real-time fluorescence imaging analysis was used to study the targeted efficacy of the complex. A nanomicelle-microsphere composite was successively constructed. Moreover, Spm-modified micelles significantly enhanced cytotoxicity and displayed more efficient cellular uptake. Notably, an orthotopic lung cancer implantation model based on C57BL/6 mice was also successively established, and in vivo biodistribution studies confirmed that the complex greatly improved the distribution of DOX in the lungs and displayed notable tumor targeting. These results suggested that the nanomicelle-microsphere composite has potential application prospects in the targeted treatment of lung cancer.

The Role of p53-Mediated Signaling in the Therapeutic Response of Colorectal Cancer to 9F, a Spermine-Modified Naphthalene Diimide Derivative

Colorectal cancer (CRC) is one of the most prevalent cancers due to its frequency and high rate of mortality. Polyamine-vectorized anticancer drugs possess multiple biological properties. Of these drugs, 9F has been shown to inhibit tumor growth and the metastasis of hepatocellular carcinoma. This current study aims to investigate the effects of 9F on CRC and determine its molecular mechanisms of action. Our findings demonstrate that 9F inhibits CRC cell growth by inducing apoptosis and cell cycle arrest, and suppresses migration, invasion and angiogenesis in vitro, resulting in the inhibition of tumor growth and metastasis in vivo. Based on RNA-seq data, further bioinformatic analyses suggest that 9F exerts its anticancer activities through p53 signaling, which is responsible for the altered expression of key regulators of the cell cycle, apoptosis, the epithelial-to-mesenchymal transition (EMT), and angiogenesis. In addition, 9F is more effective than amonafide against CRC. These results show that 9F can be considered as a potential strategy for CRC treatment.

Randomized, double-blind trial of F14512, a polyamine-vectorized anticancer drug, compared with etoposide phosphate, in dogs with naturally occurring lymphoma

Purpose: F14512 is an epipodophyllotoxin derivative from etoposide, combined with a spermine moiety introduced as a cell delivery vector. The objective of this study was to compare the safety and antitumor activity of F14512 and etoposide phosphate in dogs with spontaneous non-Hodgkin lymphoma (NHL) and to investigate the potential benefit of F14512 in P-glycoprotein (Pgp) overexpressing lymphomas.

Experimental Design: Forty-eight client-owned dogs with intermediate to high-grade NHL were enrolled into a randomized, double-blind trial of F14512 versus etoposide phosphate. Endpoints included safety and therapeutic efficacy.

Results: Twenty-five dogs were randomized to receive F14512 and 23 dogs to receive etoposide phosphate. All adverse events (AEs) were reversible, and no treatment-related death was reported. Hematologic AEs were more severe with F14512 and gastrointestinal AEs were more frequent with etoposide phosphate. F14512 exhibited similar response rate and progression-free survival (PFS) as etoposide phosphate in the global treated population. Subgroup analysis of dogs with Pgp-overexpressing NHL showed a significant improvement in PFS in dogs treated with F14512 compared with etoposide phosphate.

Conclusion: F14512 showed strong therapeutic efficacy against spontaneous NHL and exhibited a clinical benefice in Pgp-overexpressing lymphoma superior to etoposide phosphate. The results clearly justify the evaluation of F14512 in human clinical trials.

Spermine modified polymeric micelles with pH-sensitive drug release for targeted and enhanced antitumor therapy

Tumor targeting delivery of chemotherapeutic drugs by nanocarriers has been demonstrated to be a promising strategy for cancer therapy with improved therapeutic efficacy. In this work, we reported a novel type of active targeting micelle with pH-responsive drug release by using biodegradable poly(lactide)-poly(2-ethyl-2-oxazoline) di-block copolymers functionalized with spermine (SPM). SPM has been considered as a tumor binding ligand through its specific interaction with the polyamine transport system (PTS), a transmembrane protein overexpressed on various types of cancer cell, while its application in nano-drug delivery systems has rarely been explored. The micelles with spherical shape (∼110 nm) could load hydrophobic paclitaxel (PTX) with high capacity, and release the payload much faster at acidic pH (4.5–6.5) than at pH 7.4. This pH-responsive property assisted the rapid escape of drug from the endo/lysosome after internalization as demonstrated by confocal laser scanning microscopy images using coumarin-6 (Cou-6) as a fluorescent probe. With surface SPM modification, the micelles displayed much higher cellular uptake than SPM lacking micelles in various types of cancer cells, demonstrating tumor targeting ability. The uptake mechanism of SPM modified micelles was explored by flow cytometry, which suggested an energy-consuming sag vesicle-mediated endocytosis pathway. As expected, the micelles displayed significantly enhanced anti-cancer activity. This work demonstrates that SPM modified pH-sensitive micelles may be potential drug delivery vehicles for targeting and effective cancer therapy.

Tumor targeting delivery of SPM functionalized micelles via PTS binding and their endocytosis and pH-triggered endo/lysosome drug release for anti-cancer therapy.

Polyamine-containing etoposide derivatives as poisons of human type II topoisomerases: Differential effects on topoisomerase IIα and IIβ

Etoposide is an anticancer drug that acts by inducing topoisomerase II-mediated DNA cleavage. Despite its wide use, etoposide is associated with some very serious side-effects including the development of treatment-related acute myelogenous leukemias. Etoposide targets both human topoisomerase IIα and IIβ. However, the contributions of the two enzyme isoforms to the therapeutic vs. leukemogenic properties of the drug are unclear. In order to develop an etoposide-based drug with specificity for cancer cells that express an active polyamine transport system, the sugar moiety of the drug has been replaced with a polyamine tail. To analyze the effects of this substitution on the specificity of hybrid molecules toward the two enzyme isoforms, we analyzed the activity of a series of etoposide-polyamine hybrids toward human topoisomerase IIα and IIβ. All of the compounds displayed an ability to induce enzyme-mediated DNA cleavage that was comparable to or higher than that of etoposide. Relative to the parent drug, the hybrid compounds displayed substantially higher activity toward topoisomerase IIβ than IIα. Modeling studies suggest that the enhanced specificity may result from interactions with Gln778 in topoisomerase IIβ. The corresponding residue in the α isoform is a methionine.

Polyamines and Cancer

This chapter provides an overview of how the polyamine pathway has been exploited as a target for the treatment and prevention of multiple forms of cancer, since this pathway is disrupted in all cancers. It is divided into three main sections. The first explores how the polyamine pathway has been targeted for chemotherapy, starting from the first drug to target it, difluoromethylornithine (DFMO) to the large variety of polyamine analogues that have been synthesised and tested throughout the years with all their potentials and pitfalls. The second section focuses on the use of polyamines as vectors for drug delivery. Knowing that the polyamine transport system is upregulated in cancers and that polyamines naturally bind to DNA, a range of polyamine analogues and polyamine-like structures have been synthesised to target epigenetic regulators, with encouraging results. Furthermore, the use of polyamines as transport vectors to introduce toxic/bioactive/fluorescent agents more selectively to the intended target in cancer cells is discussed. The last section concentrates on chemoprevention, where the different strategies that have been undertaken to interfere with polyamine metabolism and function for antiproliferative intervention are outlined and discussed.

The role of VDR and BIM in potentiation of cytarabine-induced cell death in human AML blasts

Acute Myeloid Leukemia (AML) has grave prognosis due to aggressive nature of the disease, the toxicity of standard treatment, and overall low cure rates. We recently showed that AML cells in established culture treated with cytarabine (AraC) and a differentiation agent combination show enhancement of AraC cytotoxicity. Here we elucidate molecular changes which underlie this observation with focus on AML blasts in primary culture. The cells were treated with AraC at concentrations achievable in clinical settings, and followed by the addition of Doxercalciferol, a vitamin D2 derivative (D2), together with Carnosic acid (CA), a plant-derived antioxidant. Importantly, although AraC is also toxic to normal bone marrow cell population, the enhanced cell kill by D2/CA was limited to malignant blasts. This enhancement of cell death was associated with activation of the monocytic differentiation program as shown by molecular markers, and the increased expression of vitamin D receptor (VDR). Apoptosis elicited by this treatment is caspase-dependent, and the optimal blast killing required the increased expression of the apoptosis regulator Bim. These data suggest that testing of this regimen in the clinic is warranted.

The DNA-Binding Polyamine Moiety in the Vectorized DNA Topoisomerase II Inhibitor F14512 Alters Reparability of the Consequent Enzyme-Linked DNA Double-Strand Breaks

Poisons of topoisomerase II (TOP2) kill cancer cells by preventing religation of intermediate DNA breaks during the enzymatic process and thus by accumulating enzyme-drug-DNA complexes called TOP2 cleavage-complex (TOP2cc). F14512 is a highly cytotoxic polyamine-vectorized TOP2 inhibitor derived from etoposide and currently in clinical trials. It was shown in vitro that F14512 has acquired DNA-binding properties and that the stability of TOP2cc was strongly increased. Paradoxically, at equitoxic concentrations in cells, F14512 induced less DNA breaks than etoposide. Here, we directly compared etoposide and F14512 for their rates of TOP2cc production and resolution in human cells. We report that targeting of TOP2α and not TOP2β impacts cell killing by F14512, contrary to etoposide that kills cells through targeting both isoforms. Then, we show that despite being more cytotoxic, F14512 is less efficient than etoposide at producing TOP2α cleavage-complex (TOP2αcc) in cells. Finally, we report that compared with TOP2αcc mediated by etoposide, those generated by F14512 persist longer in the genome, are not dependent on TDP2 for cleaning break ends from TOP2α, are channeled to a larger extent to resection-based repair processes relying on CtIP and BRCA1 and promote RAD51 recruitment to damaged chromatin. In addition to the addressing of F14512 to the polyamine transport system, the properties uncovered here would be particularly valuable for a therapeutic usage of this new anticancer compound. More generally, the concept of increasing drug cytotoxicity by switching the repair mode of the induced DNA lesions via addition of a DNA-binding moiety deserves further developments. Mol Cancer Ther; 16(10); 2166-77. ©2017 AACR.

Dose escalation study to evaluate safety, tolerability and efficacy of intravenous etoposide phosphate administration in 27 dogs with multicentric lymphoma

Comparative oncology has shown that naturally occurring canine cancers are of valuable and translatable interest for the understanding of human cancer biology and the characterization of new therapies. This work was part of a comparative oncology project assessing a new, clinical-stage topoisomerase II inhibitor and comparing it with etoposide in dogs with spontaneous lymphoma with the objective to translate findings from dogs to humans. Etoposide is a topoisomerase II inhibitor widely used in various humans' solid and hematopoietic cancer, but little data is available concerning its potential antitumor efficacy in dogs. Etoposide phosphate is a water-soluble prodrug of etoposide which is expected to be better tolerated in dogs. The objectives of this study were to assess the safety, the tolerability and the efficacy of intravenous etoposide phosphate in dogs with multicentric lymphoma. Seven dose levels were evaluated in a traditional 3+3 phase I design. Twenty-seven owned-dogs with high-grade multicentric lymphoma were enrolled and treated with three cycles of etoposide phosphate IV injections every 2 weeks. Adverse effects were graded according to the Veterinary Cooperative Oncology Group criteria. A complete end-staging was realized 45 days after inclusion. The maximal tolerated dose was 300 mg/m2. At this dose level, the overall response rate was 83.3% (n = 6, 3 PR and 2 CR). Only a moderate reversible gastrointestinal toxicity, no severe myelotoxicity and no hypersensitivity reaction were reported at this dose level. Beyond the characterization of etoposide clinical efficacy in dogs, this study underlined the clinical and therapeutic homologies between dog and human lymphomas.

Natural Compounds as Anticancer Agents Targeting DNA Topoisomerases

DNA topoisomerases are important cellular enzymes found in almost all types of living cells (eukaryotic and prokaryotic). These enzymes are essential for various DNA metabolic processes e.g. replication, transcription, recombination, chromosomal decatenation etc. These enzymes are important molecular drug targets and inhibitors of these enzymes are widely used as effective anticancer and antibacterial drugs. However, topoisomerase inhibitors have some therapeutic limitations and they exert serious side effects during cancer chemotherapy. Thus, development of novel anticancer topoisomerase inhibitors is necessary for improving cancer chemotherapy. Nature serves as a repertoire of structurally and chemically diverse molecules and in the recent years many DNA topoisomerase inhibitors have been identified from natural sources. The present review discusses anticancer properties and therapeutic importance of eighteen recently identified natural topoisomerase inhibitors (from the year 2009 to 2015). Structural characteristics of these novel inhibitors provide backbones for designing and developing new anticancer drugs.

Cancer cell targeting driven by selective polyamine reactivity with glycine propargyl esters

Glycine propargyl ester reactivity shows evidence for selective polyamine reactivity, leading to a new strategy for cancer cell targeting.

Synthesis and Biological Evaluation of Novel Aromatic Imide-Polyamine Conjugates

Three types of conjugates in which aromatic imide scaffolds were coupled to diverse amine/polyamine motifs were synthesized, and their antitumor activities were evaluated in vitro and in vivo. Results showed that the conjugate 11e of 1,8-naphthilimide with spermine had pronounced effects on inhibiting tumor cell proliferation and inducing tumor cell apoptosis via ROS-mediated mitochondrial pathway. The in vivo assays on three H22 tumor transplant models revealed that compound 11e exerted potent ability in preventing lung cancer metastasis and extending lifespan. Furthermore, the efficacy of 11e in inhibiting tumor growth and improving body weight index were better than that of positive control, amonafide. Our study demonstrates that compound 11e is a valuable lead compound for further investigation.

Discovery bioanalysis and in vivo pharmacology as an integrated process: a case study in oncology drug discovery

Background: A bioanalytical team dedicated to in vivo pharmacology was set up to accelerate the selection and characterization of compounds to be evaluated in animal models in oncology. Results: A DBS-based serial microsampling procedure was optimized from sample collection to extraction to obtain a generic procedure. UHPLC–high-resolution mass spectrometer configuration allowed for fast quantitative and qualitative analysis. Using an optimized lead compound, we show how bioanalysis supported in vivo pharmacology by generating blood and tumor exposure, drug monitoring and PK/PD data. Conclusion: This process provided unique opportunities for the characterization of drug properties, selection and assessment of compounds in animal models and to support and expedite proof-of-concept studies in oncology.

Strategies for the Optimization of Natural Leads to Anticancer Drugs or Drug Candidates

Natural products have made significant contribution to cancer chemotherapy over the past decades and remain an indispensable source of molecular and mechanistic diversity for anticancer drug discovery. More often than not, natural products may serve as leads for further drug development rather than as effective anticancer drugs by themselves. Generally, optimization of natural leads into anticancer drugs or drug candidates should not only address drug efficacy, but also improve absorption, distribution, metabolism, excretion, and toxicity (ADMET) profiles and chemical accessibility associated with the natural leads. Optimization strategies involve direct chemical manipulation of functional groups, structure-activity relationship directed optimization and pharmacophore-oriented molecular design based on the natural templates. Both fundamental medicinal chemistry principles (e.g., bioisosterism) and state-of-the-art computer-aided drug design techniques (e.g., structure-based design) can be applied to facilitate optimization efforts. In this review, the strategies to optimize natural leads to anticancer drugs or drug candidates are illustrated with examples and described according to their purposes. Furthermore, successful case studies on lead optimization of bioactive compounds performed in the Natural Products Research Laboratories at UNC are highlighted.

F14512, a polyamine-vectorized inhibitor of topoisomerase II, exhibits a marked anti-tumor activity in ovarian cancer

Epithelial ovarian cancer is the fourth cause of death among cancer-bearing women and frequently associated with carboplatin resistance, underlining the need for more efficient and targeted therapies. F14512 is an epipodophylotoxin-core linked to a spermine chain which enters cells via the polyamine transport system (PTS). Here, we investigate this novel concept of vectorization in ovarian cancer. We compared the effects of etoposide and F14512 on a panel of five carboplatin-sensitive or resistant ovarian cancer models. We assessed the incorporation of F17073, a spermine-linked fluorescent probe, in these cells and in 18 clinical samples. We then showed that F14512 exhibits a high anti-proliferative and pro-apoptotic activity, particularly in cells with high levels of F17073 incorporation. Consistently, F14512 significantly inhibited tumor growth compared to etoposide, in a cisplatin-resistant A2780R subcutaneous model, at a dose of 1.25 mg/kg. In addition, ex vivo analysis indicated that 15 out of 18 patients presented a higher F17073 incorporation into tumor cells compared to normal cells. Overall, our data suggest that F14512, a targeted drug with a potent anti-tumor efficacy, constitutes a potential new therapy for highly PTS-positive and platinum-resistant ovarian cancer-bearing patients.

An optimized polyamine moiety boosts the potency of human type II topoisomerase poisons as quantified by comparative analysis centered on the clinical candidate F14512

Combined computational-experimental analyses explain and quantify the spermine-vectorized F14512's boosted potency as a topoII poison. We found that an optimized polyamine moiety boosts drug binding to the topoII/DNA cleavage complex, rather than to the DNA alone. These results provide new structural bases and key reference data for designing new human topoII poisons.

Phase I Clinical Pharmacology Study of F14512, a New Polyamine-Vectorized Anticancer Drug, in Naturally Occurring Canine Lymphoma

PURPOSE

F14512 is a new topoisomerase II inhibitor containing a spermine moiety that facilitates selective uptake by tumor cells and increases topoisomerase II poisoning. F14512 is currently in a phase I/II clinical trial in patients with acute myeloid leukemia. The aim of this study was to investigate F14512 potential in a new clinical indication. Because of the many similarities between human and dog lymphomas, we sought to determine the tolerance, efficacy, pharmacokinetic/pharmacodynamic (PK/PD) relationship of F14512 in this indication, and potential biomarkers that could be translated into human trials.

EXPERIMENTAL DESIGN

Twenty-three dogs with stage III-IV naturally occurring lymphomas were enrolled in the phase I dose-escalation trial, which consisted of three cycles of F14512 i.v. injections. Endpoints included safety and therapeutic efficacy. Serial blood samples and tumor biopsies were obtained for PK/PD and biomarker studies.

RESULTS

Five dose levels were evaluated to determine the recommended dose. F14512 was well tolerated, with the expected dose-dependent hematologic toxicity. F14512 induced an early decrease of tumoral lymph node cells, and a high response rate of 91% (21/23) with 10 complete responses, 11 partial responses, 1 stable disease, and 1 progressive disease. Phosphorylation of histone H2AX was studied as a potential PD biomarker of F14512.

CONCLUSIONS

This trial demonstrated that F14512 can be safely administered to dogs with lymphoma resulting in strong therapeutic efficacy. Additional evaluation of F14512 is needed to compare its efficacy with standards of care in dogs, and to translate biomarker and efficacy findings into clinical trials in humans.

Podophyllotoxin derivatives: a patent review (2012 - 2014)

INTRODUCTION

Podophyllotoxin (PPT) is a naturally occurring antimitotic agent and an interesting lead in the development of anticancer agents. Its optimization led to the development of etoposide and teniposide used in combination chemotherapy with other anticancer drugs; unlike PPT these drugs act by inhibiting topoisomerases. Clinical success and toxicity issues at later stages of etoposide usage inclined researchers to develop structurally modified PPT derivatives. Some of the compounds obtained are under clinical investigations and are anticipated to reach the market.

AREAS COVERED

The present review summarizes the attempts made by researchers across the globe to find out newer anticancer agents based on the PPT structure. It brings out the outline of the inventions filed in the form of patents during the years 2012 - 2014.

EXPERT OPINION

After the successful development of etoposide and teniposide there has been considerable interest in the PPT skeleton to develop newer chemotherapeutic agents. In this regard, several PPT derivatives such as TOP53, GL331, NK611, F11782, and so on, have been developed and are undergoing clinical trials. However, its low natural abundance is a major problem in carrying out research on PPT skeleton. This issue is expected to be addressed with the development of newer synthetic strategies to access structurally modified PPTs.

A polyamine-modified near-infrared fluorescent probe for selective staining of live cancer cells

A novel polyamine-modified near-infrared fluorescent probe has been developed that allows for selective labeling of living cancer cells in presence of non-cancer cells.

Activity of the polyamine-vectorized anti-cancer drug F14512 against pediatric glioma and neuroblastoma cell lines

The poor prognosis of children with high-grade glioma (HGG) and high-risk neuroblastoma, despite multidisciplinary therapeutic approaches, demands new treatments for these indications. F14512 is a topoisomerase II inhibitor containing a spermine moiety that facilitates selective uptake by tumor cells via the Polyamine Transport System (PTS) and increases topoisomerase II poisoning. Here, F14512 was evaluated in pediatric HGG and neuroblastoma cell lines. PTS activity and specificity were evaluated using a fluorescent spermine-coupled probe. The cytotoxicity of F14512, alone or in combination with ionizing radiation and chemotherapeutic agents, was investigated in vitro. The antitumor activity of F14512 was assessed in vivo using a liver-metastatic model of neuroblastoma. An active PTS was evidenced in all tested cell lines, providing a specific and rapid transfer of spermine-coupled compounds into cell nuclei. Competition experiments confirmed the essential role of PTS in the cell uptake and cytotoxicity of F14512. This cytotoxicity appeared greater in neuroblastoma cells compared with HGG cells but appeared independent of PTS activity levels. In vivo evaluation confirmed a marked and prolonged antitumoral effect in neuroblastoma cells. The combinations of F14512 with cisplatin and carboplatin were often found to be synergistic, and we demonstrated the significant radiosensitizing potential of F14512 in the MYCN-amplified Kelly cell line. Thus, F14512 appears more effective than etoposide in pediatric tumor cell lines, with greater efficacy in neuroblastoma cells compared with HGG cells. The synergistic effects observed with platinum compounds and the radiosensitizing effect could lead to a clinical development of the drug in pediatric oncology.

The antitumor drug F14512 enhances cisplatin and ionizing radiation effects in head and neck squamous carcinoma cell lines

BACKGROUND

Head and Neck Squamous Cell Carcinoma (HNSCC) is the sixth most common cancer worldwide. The treatment of advanced stages HNSCC is based on surgical treatment combined with radiotherapy and chemotherapy or concomitant chemo-radiotherapy. However, the 5-year survival remains poor for advanced stages HNSCC and the development of new targeted therapies is eagerly awaited. F14512 combines an epipodophyllotoxin core-targeting topoisomerase II with a spermine moiety introduced as a cell delivery vector. This spermine moiety facilitates selective uptake by tumor cells via the Polyamine Transport System (PTS) and reinforces topoisomerase II poisoning. Here we report the evaluation of F14512 toward HNSCC.

MATERIALS AND METHODS

Four cell lines representative of head and neck cancer localizations were used: Fadu (pharynx), SQ20B (larynx), CAL33 and CAL27 (base of the tongue). PTS activity and specificity were evaluated by confocal microscopy and flow cytometry using the fluorescent probe F17073 which contains the same spermine moiety as F14512. Cytotoxicity, alone or in association with standard chemotherapeutic agents (cisplatin, 5FU), and radio-sensitizing effects were investigated using MTS and clonogenic assays, respectively. F14512 efficiency and PTS activity were also measured under hypoxic conditions (1% O2).

RESULTS

In all 4 tested HNSCC lines, an active PTS was evidenced providing a specific and rapid transfer of spermine-coupled compounds into cell nuclei. Interestingly, F14512 presents a 1.6-11-fold higher cytotoxic effect than the reference compound etoposide (lacking the spermine chain). It appears also more cytotoxic than 5FU and cisplatin in all cell lines. Competition experiments with spermine confirmed the essential role of the PTS in the cell uptake and cytotoxicity of F14512. Hypoxia had almost no impact on the drug cytotoxicity. The combination of F14512 with cisplatin, but not 5FU, was found to be synergistic and, for the first time, we demonstrated the significant radio-sensitizing potential of F14512.

CONCLUSION

The spermine moiety of F14512 confers a targeted effect and a much better efficacy than etoposide in HNSCC lines. The synergistic effect observed in association with cisplatin and radiotherapy augurs well for the potential development of F14512 in HNSCC.