Differences in the intracellular distribution of acid-sensitive doxorubicin-protein conjugates in comparison to free and liposomal formulated doxorubicin as shown by confocal microscopy

Liposomal Doxorubicin In vitro and In vivo Assays in Non-small Cell Lung Cancer: A Systematic Review

BACKGROUND

Liposomal Doxorubicin (Doxil®) was one of the first nanoformulations approved for the treatment of solid tumors. Although there is already extensive experience in its use for different tumors, there is currently no grouped evidence of its therapeutic benefits in non-small cell lung cancer (NSCLC). A systematic review of the literature was performed on the therapeutic effectiveness and benefits of Liposomal Doxil® in NSCLC.

METHODS

A total of 1022 articles were identified in publications up to 2020 (MEDLINE, Cochrane, Web of Science Core Collection and Scopus). After applying inclusion criteria, the number was restricted to 114, of which 48 assays, including in vitro (n=20) and in vivo (animals, n=35 and humans, n=6) studies, were selected.

RESULTS

The maximum inhibitory concentration (IC50), tumor growth inhibition rate, response and survival rates were the main indices for evaluating the efficacy and effectiveness of Liposomal DOX. These have shown clear benefits both in vitro and in vivo, improving the IC50 of free DOX or untargeted liposomes, depending on their size, administration, or targeting.

CONCLUSION

Doxil® significantly reduced cellular proliferation in vitro and improved survival in vivo in both experimental animals and NSCLC patients, demonstrating optimal safety and pharmacokinetic behavior indices. Although our systematic review supports its benefits for the treatment of NSCLC, additional clinical trials with larger sample sizes are necessary to obtain more precise clinical data on its activity and effects in humans.

In situ cellular hitchhiking of nanoparticles for drug delivery

Since the inception of the concept of "magic bullet", nanoparticles have evolved to be one of the most effective carriers in drug delivery. Nanoparticles improve the therapeutic efficacy of drugs offering benefits to treating various diseases. Unlike free drugs which freely diffuse and distribute through the body, nanoparticles protect the body from the drug by reducing non-specific interactions while also improving the drug's pharmacokinetics. Despite acquiring some FDA approvals, further clinical application of nanoparticles is majorly hindered by its limited ability to overcome biological barriers resulting in uncontrolled biodistribution and high clearance. The use of cell-inspired systems has emerged as a promising approach to overcome this challenge as cells are biocompatible and have improved access to tissues and organs. One of such is the hitchhiking of nanoparticles to circulating cells such that they are recognized as 'self' components evading clearance and resulting in site-specific drug delivery. In this review, we discuss the concept of nanoparticle cellular hitchhiking, highlighting its advantages, the principles governing the process and the challenges currently limiting its clinical translation. We also discuss in situ hitchhiking as a tool for overcoming these challenges and the considerations to be taken to guide research efforts in advancing this promising technology.

Doxorubicin Assisted by Microsecond Electroporation Promotes Irreparable Morphological Alternations in Sensitive and Resistant Human Breast Adenocarcinoma Cells

Electroporation increases the transmembrane transport of molecules. The combination of electric pulses with cytostatic compounds is beneficial for cancer treatment. Doxorubicin (DOX) is a commonly used chemotherapeutic anticancer drug. Its fluorescence properties enable the investigation of drug distribution and metabolism. In this study, doxorubicin was enhanced by electroporation to eliminate cancer cells more effectively. The influence of electroporation on the drug uptake was evaluated in two cell lines: MCF-7/WT and MCF-7/DOX. The intracellular localization of doxorubicin and its impact on the intracellular structure organization were examined under a confocal microscope. Cellular effects were examined with the 3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test that estimates the rate of metabolism in viable cells. The ultrastructure (TEM) of tumor cells subjected to the electric field was analyzed. An enhanced doxorubicin efficacy was observed in MCF-7/DOX cells after combination with electroporation. The response of the resistant cell line was revealed to be more sensitive to electric pulses. Electroporation-based methods may be attractive for cancer treatment in human breast adenocarcinoma, especially with acquired resistance. Electroporation enables a reduction of the effective dose of the drugs and the exposure time in this type of cancer, diminishing side effects of the systemic therapy.

Carnosic Acid, Tangeretin, and Ginkgolide-B Anti-neoplastic Cytotoxicity in Dual Combination with Dexamethasone-[anti-EGFR] in Pulmonary Adenocarcinoma (A549)

Background:

Traditional chemotherapeutics of low-molecular weight diffuse passively across intact membrane structures of normal healthy cells found in tissues and organ systems in a non-specific unrestricted manner which largely accounts for the induction of most sequelae which restrict dosage, administration frequency, and duration of therapeutic intervention. Molecular strategies that offer enhanced levels of potency, greater efficacy and broader margins-of-safety include the discovery of alternative candidate therapeutics and development of methodologies capable of mediating properties of selective “targeted” delivery.

Materials and Methods:

The covalent immunopharmaceutical, dexamethasone-(C21-phosphoramidate)-[anti- EGFR] was synthesized utilizing organic chemistry reactions that comprised a multi-stage synthesis regimen. Multiple forms of analysis were implemented to vadliate the successful synthesis (UV spectrophotometric absorbance), purity and molar-incorporation-index (UV spectrophotometric absorbance, chemical-based protein determination), absence of fragmentation/polymerization (SDS-PAGE/chemiluminescent autoradiography), retained selective binding-avidity of IgG-immunoglobulin (cell-ELISA); and selectively “targeted” antineoplastic cytotoxicity (biochemistry-based cell vitality/viability assay).

Results:

The botanicals carnosic acid, ginkgolide-B and tangeretin, each individually exerted maximum antineoplastic cytotoxicity levels of 58.1%, 5.3%, and 41.1% respectively against pulmonary adenocarcinoma (A549) populations. Dexamethasone-(C21-phosphoramidate)-[anti-EGFR] formulated at corticosteroid/ glucocorticoid equivalent concentrations produced anti-neoplastic cytotoxicity at levels of 7.7% (10-9 M), 26.9% (10-8 M), 64.9% (10-7 M), 69.9% (10-6 M) and 73.0% (10-5 M). Ccarnosic acid, ginkgolide-B and tangeretin in simultaneous dual-combination with dexamethasone-(C21-phosphoramidate)-[anti-EGFR] exerted maximum anti-neoplastic cytotoxicity levels of 70.5%, 58.6%, and 69.7% respectively.

Discussion:

Carnosic acid, ginkgolide-B and tangeretin botanicals exerted anti-neoplastic cytotoxicity against pulmonary adenocarcinoma (A549) which additively contributed to the anti-neoplastic cytotoxic potency of the covalent immunopharmaceutical, dexamethasone-(C21-phosphoramidate)-[anti-EGFR]. Carnosic acid and tangeretin were most potent in this regard both individually and in dual-combination with dexamethasone-(C21- phosphoramidate)-[anti-EGFR]. Advantages and attributes of carnosic acid and tangeretin as potential monotherapeutics are a wider margin-of-safety of conventional chemotherapeutics which would readily complement the selective “targeted” delivery properties of dexamethasone-(C21-phosphoramidate)-[anti-EGFR] and possibly other covalent immunopharmaceuticals in addition to providing opportunities for the discovery of combination therapies that provide heightened levels of anti-neoplastic efficacy.

Spotlight on aldoxorubicin (INNO-206) and its potential in the treatment of soft tissue sarcomas: evidence to date

Anthracyclines, and doxorubicin in particular, remain a mainstay of sarcoma therapy. Despite modest activity and significant toxicities, no cytotoxic monotherapy has yet yielded superior overall survival over doxorubicin for therapy of advanced soft tissue sarcomas in a randomized trial. Similarly, combination regimens have also been unable to overcome doxorubicin in terms of overall survival. Strategies to ameliorate the most prominent side effect of doxorubicin, cardiotoxicity, are available, but their use in sarcoma patients has been limited. Aldoxorubicin is a prodrug consisting of doxorubicin with a covalent linker. It binds rapidly after intravenous infusion to cysteine-34 of human serum albumin. The drug-albumin conjugate is preferentially retained in tumor tissue, with uptake into tumoral cells. At physiologic pH, the complex is stable. Hydrolysis can occur under the acidic conditions of the endocytic lysosome, releasing doxorubicin. Doxorubicin then distributes to various cellular compartments, including Golgi, mitochondrion, and nucleus, with subsequent cytotoxic effects. Aldoxorubicin has demonstrated in vitro and in vivo activities in both cancer model systems and human xenografts. Preclinical models also support its decreased cardiac effects vs doxorubicin, although such promising results require formal comparison at efficacy equivalent doses of the two drugs. Phase I studies confirmed the tolerability of aldoxorubicin in humans. Clinical cardiotoxicity was not observed, but molecular and subclinical cardiac effects could be demonstrated. A Phase II study in treatment-naïve, advanced sarcoma patients demonstrated improved progression-free survival and response rate over doxorubicin, although no survival benefit was evident. A Phase III study of aldoxorubicin vs investigator's choice from a panel of chemotherapy regimens in the salvage setting was unable to demonstrate a benefit in progression-free or overall survival in the entire population. Progression-free survival in L-sarcomas (leiomyosarcomas and liposarcomas) was documented. While evidence of subclinical cardiac effects was seen in a small proportion of aldoxorubicin-treated patients, data from both the Phase II and III studies indicated a favorable cardiotoxicity profile vs doxorubicin. Despite the negative results from this Phase III study, the importance of anthracycline therapy in sarcoma management merits further investigation of the potential role of aldoxorubicin in this indication. Other avenues for progress include identification of sensitive histologies and biomarkers of activity, exploration of clinical niches without proven standard therapies, and exploration of alternate dosing strategies.

Harnessing albumin as a carrier for cancer therapies

Serum albumin, a natural ligand carrier that is highly concentrated and long-circulating in the blood, has shown remarkable promise as a carrier for anti-cancer agents. Albumin is able to prolong the circulation half-life of otherwise rapidly cleared drugs and, importantly, promote their accumulation within tumors. The applications for using albumin as a cancer drug carrier are broad and include both traditional cancer chemotherapeutics and new classes of biologics. Strategies for leveraging albumin for drug delivery can be classified broadly into exogenous and in situ binding formulations that utilize covalent attachment, non-covalent association, or encapsulation in albumin-based nanoparticles. These methods have shown remarkable preclinical and clinical successes that are examined in this review.

Gemcitabine-(5'-phosphoramidate)-[anti-IGF-1R]: molecular design, synthetic organic chemistry reactions, and antineoplastic cytotoxic potency in populations of pulmonary adenocarcinoma (A549)

One molecular-based approach that increases potency and reduces dose-limited sequela is the implementation of selective 'targeted' delivery strategies for conventional small molecular weight chemotherapeutic agents. Descriptions of the molecular design and organic chemistry reactions that are applicable for synthesis of covalent gemcitabine-monophosphate immunochemotherapeutics have to date not been reported. The covalent immunopharmaceutical, gemcitabine-(5'-phosphoramidate)-[anti-IGF-1R] was synthesized by reacting gemcitabine with a carbodiimide reagent to form a gemcitabine carbodiimide phosphate ester intermediate which was subsequently reacted with imidazole to create amine-reactive gemcitabine-(5'-phosphorylimidazolide) intermediate. Monoclonal anti-IGF-1R immunoglobulin was combined with gemcitabine-(5'-phosphorylimidazolide) resulting in the synthetic formation of gemcitabine-(5'-phosphoramidate)-[anti-IGF-1R]. The gemcitabine molar incorporation index for gemcitabine-(5'-phosphoramidate)-[anti-IGF-R1] was 2.67:1. Cytotoxicity Analysis - dramatic increases in antineoplastic cytotoxicity were observed at and between the gemcitabine-equivalent concentrations of 10-9  M and 10-7  M where lethal cancer cell death increased from 0.0% to a 93.1% maximum (100.% to 6.93% residual survival), respectively. Advantages of the organic chemistry reactions in the multistage synthesis scheme for gemcitabine-(5'-phosphoramidate)-[anti-IGF-1R] include their capacity to achieve high chemotherapeutic molar incorporation ratios; option of producing an amine-reactive chemotherapeutic intermediate that can be preserved for future synthesis applications; and non-dedicated organic chemistry reaction scheme that allows substitutions of either or both therapeutic moieties, and molecular delivery platforms.

Dexamethasone-(C21-phosphoramide)-[anti-EGFR]: molecular design, synthetic organic chemistry reactions, and antineoplastic cytotoxic potency against pulmonary adenocarcinoma (A549)

PURPOSE

Corticosteroids are effective in the management of a variety of disease states, such as several forms of neoplasia (leukemia and lymphoma), autoimmune conditions, and severe inflammatory responses. Molecular strategies that selectively "target" delivery of corticosteroids minimize or prevents large amounts of the pharmaceutical moiety from passively diffusing into normal healthy cell populations residing within tissues and organ systems.

MATERIALS AND METHODS

The covalent immunopharmaceutical, dexamethasone-(C21-phosphoramide)-[anti-EGFR] was synthesized by reacting dexamethasone-21-monophosphate with a carbodiimide reagent to form a dexamethasone phosphate carbodiimide ester that was subsequently reacted with imidazole to create an amine-reactive dexamethasone-(C21-phosphorylimidazolide) intermediate. Monoclonal anti-EGFR immunoglobulin was combined with the amine-reactive dexamethasone-(C21-phosphorylimidazolide) intermediate, resulting in the synthesis of the covalent immunopharmaceutical, dexamethasone-(C21-phosphoramide)-[anti-EGFR]. Following spectrophotometric analysis and validation of retained epidermal growth factor receptor type 1 (EGFR)-binding avidity by cell-ELISA, the selective anti-neoplasic cytotoxic potency of dexamethasone-(C21-phosphoramide)-[anti-EGFR] was established by MTT-based vitality stain methodology using adherent monolayer populations of human pulmonary adenocarcinoma (A549) known to overexpress the tropic membrane receptors EGFR and insulin-like growth factor receptor type 1.

RESULTS

The dexamethasone:IgG molar-incorporation-index for dexamethasone-(C21-phosphoramide)-[anti-EGFR] was 6.95:1 following exhaustive serial microfiltration. Cytotoxicity analysis: covalent bonding of dexamethasone to monoclonal anti-EGFR immunoglobulin did not significantly modify the ex vivo antineoplastic cytotoxicity of dexamethasone against pulmonary adenocarcinoma at and between the standardized dexamethasone equivalent concentrations of 10(-9) M and 10(-5) M. Rapid increases in antineoplastic cytotoxicity were observed at and between the dexamethasone equivalent concentrations of 10(-9) M and 10(-7) M where cancer cell death increased from 7.7% to a maximum of 64.9% (92.3%-35.1% residual survival), respectively, which closely paralleled values for "free" noncovalently bound dexamethasone.

DISCUSSION

Organic chemistry reaction regimens were optimized to develop a multiphase synthesis regimen for dexamethasone-(C21-phosphoramide)-[anti-EGFR]. Attributes of dexamethasone-(C21-phosphoramide)-[anti-EGFR] include a high dexamethasone molar incorporation-index, lack of extraneous chemical group introduction, retained EGFR-binding avidity ("targeted" delivery properties), and potential to enhance long-term pharmaceutical moiety effectiveness.

Selective delivery of doxorubicin by novel stimuli-sensitive nano-ferritins overcomes tumor refractoriness

Human ferritin heavy chain (HFt) has been demonstrated to possess considerable potential for targeted delivery of drugs and diagnostic agents to cancer cells. Here, we report the development of a novel HFt-based genetic construct (HFt-MP-PAS) containing a short peptide linker (MP) between each HFt subunit and an outer shielding polypeptide sequence rich in proline (P), serine (S) and alanine (A) residues (PAS). The peptide linker contains a matrix-metalloproteinases (MMPs) cleavage site that permits the protective PAS shield to be removed by tumor-driven proteolytic cleavage within the tumor microenvironment. For the first time HFt-MP-PAS ability to deliver doxorubicin to cancer cells, subcellular localization, and therapeutic efficacy on a xenogeneic mouse model of a highly refractory to conventional chemotherapeutics type of cancer were evaluated. HFt-MP-PAS-DOXO performance was compared with the novel albumin-based drug delivery system INNO-206, currently in phase III clinical trials. The results of this work provide solid evidence indicating that the stimuli-sensitive, long-circulating HFt-MP-PAS nanocarriers described herein have the potential to be exploited in cancer therapy.

Fludarabine- (C2-methylhydroxyphosphoramide)- [anti-IGF-1R]: Synthesis and Selectively "Targeted"Anti-Neoplastic Cytotoxicity against Pulmonary Adenocarcinoma (A549)

INTRODUCTION

Many if not most conventional small molecular weight chemotherapeutics are highly potent against many forms of neoplastic disease. Unfortunately, majority of an administered dose unintentionally diffuses passively into normal tissues and healthy organ systems following intravenous administration. One strategy for both increasing potency and reducing dose-limited sequela is the selective "targeted" delivery of conventional chemotherapeutic agents.

MATERIALS AND METHODS

The fludarabine-(C₂- methylhydroxyphosphoramide)-[anti-IGF-1R] was synthesized by initially reacting fludarabine with a carbodiimide to form a fludarabine carbodiimide phosphate ester intermediate that was subsequently reacted with imidazole to create an amine-reactive fludarabine- (C₂-phosphorylimidazolide) intermediate. Monoclonal anti-IGF-1R immunoglobulin was combined with the amine-reactive fludarabine- (C₂-phosphorylimidazolide) intermediate resulting in the synthesis of covalent fludarabine-(C₂-methylhydroxyphosphoramide)- [anti-IGF-1R] immunochemotherapeutic. Residual fludarabine and un-reacted reagents were removed by serial microfiltration (MWCO 10,000) and monitored by analytical-scale HP-TLC. Retained IGF-1R binding-avidity of fludarabine-(C₂- methylhydroxyphosphoramide)-[anti-IGF-1R] was established by cell-ELISA using pulmonary adenocarcinoma cell (A549) which over-expresses IGF-1R and EGFR. Anti-neoplastic cytotoxic potency of fludarabine-(C₂-methylhydroxyphosphoramide)-[anti- IGF-1R] was determined against pulmonary adenocarcinoma (A549) using an MTT-based vitality stain methodology.

RESULTS

The fludarabine molar-incorporation-index for fludarabine- (C₂-methylhydroxyphosphoramide)-[anti-IGF-R1] was 3.67:1 while non-covalently bound fludarabine was not detected by analytical scale HP-TLC following serial micro-filtration. Size-separation fludarabine-(C₂-methylhydroxyphosphoramide)-[anti- IGF-1R] by SDS-PAGE with chemo luminescent autoradiography detected only a single 150-kDa band. Cell-ELISA of fludarabine- (C₂-methylhydroxyphosphoramide)-[anti-IGF-1R] measuring total immunoglobulin bound to exterior surface membranes of pulmonary adenocarcinoma (A549) increased with elevations in immunoglobulin-equivalent concentrations of the covalent fludarabine immunochemotherapeutic. Between the fludarabine-equivalent concentrations of 10^-10 M and 10^-5 M both fludarabine-(C₂- methylhydroxyphosphoramide)-[anti-IGF-1R] and fludarabine had ex-vivo anti-neoplastic cytotoxic potency levels that increased rapidly between the fludarabine-equivalent concentrations of 10^-6 M and 10^-5 M where cancer cell death percentages increased from 24.4% to a maximum of 94.7% respectively.

CONCLUSION

The molecular design and organic chemistry reaction schemes were developed for synthesizing fludarabine-(C₂- methylhydroxyphosphoramide)-[anti-IGF-1R] which possessed both properties of selective "targeted" delivery and anti-neoplastic cytotoxic potency equivalent to fludarabine chemotherapeutic.

Nanotherapeutics With Anthracyclines: Methods of Determination and Quantification of Anthracyclines in Biological Samples

Anthracyclines, e.g. doxorubicin, pirarubicin, are widely used as cytostatic agents in the polymer nanotherapeutics designed for the highly effective antitumor therapy with reduced side effects. However, their precise dosage scheme needs to be optimized, which requires an accurate method for their quantification on the cellular level in vitro during nanocarrier development and in body fluids and tissues during testing in vivo. Various methods detecting the anthracycline content in biological samples have already been designed. Most of them are highly demanding and they differ in exactness and reproducibility. The cellular uptake and localization is predominantly observed and determined by microscopy techniques, the anthracycline content is usually quantified by chromatographic analysis using fluorescence detection. We reviewed and compared published methods concerning the detection of anthracycline nanocarriers.

Simultaneous Dual Selective Targeted Delivery of Two Covalent Gemcitabine Immunochemotherapeutics and Complementary Anti-Neoplastic Potency of [Se]-Methylselenocysteine

The anti-metabolite chemotherapeutic, gemcitabine is relatively effective for a spectrum of neoplastic conditions that include various forms of leukemia and adenocarcinoma/carcinoma. Rapid systemic deamination of gemcitabine accounts for a brief plasma half-life but its sustained administration is often curtailed by sequelae and chemotherapeutic-resistance. A molecular strategy that diminishes these limitations is the molecular design and synthetic production of covalent gemcitabine immunochemotherapeutics that possess properties of selective "targeted" delivery. The simultaneous dual selective "targeted" delivery of gemcitabine at two separate sites on the external surface membrane of a single cancer cell types represents a therapeutic approach that can increase cytosol chemotherapeutic deposition; prolong chemotherapeutic plasma half-life (reduces administration frequency); minimize innocent exposure of normal tissues and healthy organ systems; and ultimately enhance more rapid and thorough resolution of neoplastic cell populations.

MATERIALS AND METHODS

A light-reactive gemcitabine intermediate synthesized utilizing succinimidyl 4,4-azipentanoate was covalently bound to anti-EGFR or anti-HER2/neu IgG by exposure to UV light (354-nm) resulting in the synthesis of covalent immunochemotherapeutics, gemcitabine-(C₄-amide)-[anti-EGFR] and gemcitabine-(C₄-amide)-[anti-HER2/neu]. Cytotoxic anti-neoplastic potency of gemcitabine-(C₄-amide)-[anti-EGFR] and gemcitabine-(C₄-amide)-[anti-HER2/neu] between gemcitabine-equivalent concentrations of 10^-12 M and 10^-6 M was determined utilizing chemotherapeutic-resistant mammary adenocarcinoma (SKRr-3). The organoselenium compound, [Se]-methylselenocysteine was evaluated to determine if it complemented the anti-neoplastic potency of the covalent gemcitabine immunochemotherapeutics.

RESULTS

Gemcitabine-(C₄-amide)-[anti-EGFR], gemcitabine-(C₄-amide)-[anti-HER2/neu] and the dual simultaneous combination of gemcitabine-(C₄-amide)-[anti-EGFR] with gemcitabine-(C₄-amide)-[anti-HER2/neu] all had anti-neoplastic cytotoxic potency against mammary adenocarcinoma. Gemcitabine-(C₄-amide)-[anti-EGFR] and gemcitabine-(C₄-amide)-[anti-HER2/neu] produced progressive increases in anti-neoplastic cytotoxicity that were greatest between gemcitabine-equivalent concentrations of 10^-9 M and 10^-6 M. Dual simultaneous combinations of gemcitabine-(C₄-amide)-[anti-EGFR] with gemcitabine-(C₄-amide)-[anti-HER2/neu] produced levels of anti-neoplastic cytotoxicity intermediate between each of the individual covalent gemcitabine immunochemotherapeutics. Total anti-neoplastic cytotoxicity of the dual simultaneous combination of gemcitabine-(C₄-amide)-[anti-EGFR] and gemcitabine-(C₄-amide)-[anti-HER2/neu] against chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) was substantially higher when formulated with [Se]-methylsele-nocysteine.

Virus-like particle-mediated intracellular delivery of mRNA cap analog with in vivo activity against hepatocellular carcinoma

Adenovirus dodecahedron (Dd), a nanoparticulate proteinaceous biodegradable virus-like particle (VLP), was used as a vector for delivery of an oncogene inhibitor to hepatocellular carcinoma (HCC) rat orthotopic model. Initiation factor eIF4E is an oncogene with elevated expression in human cancers. Cell-impermeant eIF4E inhibitor, cap structure analog (cap) and anti-cancer antibiotic doxorubicin (Dox) were delivered as Dd conjugates. Dd-cap and Dd-dox inhibited cancer cell culture proliferation up to 50 and 84%, respectively, while with free Dox similar results could be obtained only at a 5 times higher concentration. In animal HCC model the combination treatment of Dd-cap/Dd-dox caused 40% inhibition of tumor growth. Importantly, the level of two pro-oncogenes, eIF4E and c-myc, was significantly diminished in tumor sections of treated rats. Attachment to Dd, a virus-like particle, permitted the first demonstration of cap analog intracellular delivery and resulted in improved doxorubicin delivery leading to statistically significant inhibition of HCC tumor growth.

Anti-Neoplastic Cytotoxicity of Gemcitabine-(C4-amide)-[anti-EGFR] in Dual-combination with Epirubicin-(C3-amide)-[anti-HER2/neu] against Chemotherapeutic-Resistant Mammary Adenocarcinoma (SKBr-3) and the Complementary Effect of Mebendazole

AIMS

Delineate the feasibility of simultaneous, dual selective "targeted" chemotherapeutic delivery and determine if this molecular strategy can promote higher levels anti-neoplastic cytotoxicity than if only one covalent immunochemotherapeutic is selectively "targeted" for delivery at a single membrane associated receptor over-expressed by chemotherapeutic-resistant mammary adenocarcinoma.

METHODOLOGY

Gemcitabine and epirubicin were covalently bond to anti-EGFR and anti-HER2/neu utilizing a rapid multi-phase synthetic organic chemistry reaction scheme. Determination that 96% or greater gemcitabine or epirubicin content was covalently bond to immunoglobulin fractions following size separation by micro-scale column chromatography was established by methanol precipitation analysis. Residual binding-avidity of gemcitabine-(C4-amide)-[anti-EG-FR] applied in dual-combination with epirubicin-(C3-amide)-[anti-HER2/neu] was determined by cell-ELIZA utilizing chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) populations. Lack of fragmentation or polymerization was validated by SDS-PAGE/immunodetection/chemiluminescent autoradiography. Anti-neoplastic cytotoxic potency was determined by vitality stain analysis of chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) monolayers known to uniquely over-express EGFR (2 × 105/cell) and HER2/neu (1 × 106/cell) receptor complexes. The covalent immunochemotherapeutics gemcitabine-(C4-amide)-[anti-EGFR] and epirubicin-(C3-amide)-[anti-HER2/neu] were applied simultaneously in dual-combination to determine their capacity to collectively evoke elevated levels of anti-neoplastic cytotoxicity. Lastly, the tubulin/microtubule inhibitor mebendazole evaluated to determine if it's potential to complemented the anti-neoplastic cytotoxic properties of gemcitabine-(C4-amide)-[anti-EGFR] in dual-combination with epirubicin-(C3-amide)-[anti-HER2/neu].

RESULTS

Dual-combination of gemcitabine-(C4-amide)-[anti-EGFR] with epirubicin-(C3-amide)-[anti-HER2/neu] produced greater levels of anti-neoplastic cytotoxicity than either of the covalent immunochemotherapeutics alone. The benzimidazole microtubule/tubulin inhibitor, mebendazole complemented the anti-neoplastic cytotoxicity of gemcitabine-(C4-amide)-[anti-EGFR] in dual-combination with epirubicin-(C3-amide)-[anti-HER2/neu].

CONCLUSIONS

The dual-combination of gemcitabine-(C4-amide)-[anti-EGFR] with epirubicin-(C3-amide)-[anti-HER2/neu] produced higher levels of selectively "targeted" anti-neoplastic cytotoxicity against chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) than either covalent immunochemotherapeutic alone. The benzimidazole tubulin/microtubule inhibitor, mebendazole also possessed anti-neoplastic cytotoxicity against chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) and complemented the potency and efficacy of gemcitabine-(C4-amide)-[anti-EGFR] in dual-combination with epirubicin-(C3-amide)-[anti-HER2/neu].

Gene transfection in high serum levels: case studies with new cholesterol based cationic gemini lipids

Background

Six new cationic gemini lipids based on cholesterol possessing different positional combinations of hydroxyethyl (-CH₂CH₂OH) and oligo-oxyethylene -(CH₂CH₂O)_n- moieties were synthesized. For comparison the corresponding monomeric lipid was also prepared. Each new cationic lipid was found to form stable, clear suspensions in aqueous media.

Methodology/Principal Findings

To understand the nature of the individual lipid aggregates, we have studied the aggregation properties using transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential measurements and X-ray diffraction (XRD). We studied the lipid/DNA complex (lipoplex) formation and the release of the DNA from such lipoplexes using ethidium bromide. These gemini lipids in presence of a helper lipid, 1, 2-dioleoyl phophatidyl ethanol amine (DOPE) showed significant enhancements in the gene transfection compared to several commercially available transfection agents. Cholesterol based gemini having -CH₂-CH₂-OH groups at the head and one oxyethylene spacer was found to be the most effective lipid, which showed transfection activity even in presence of high serum levels (50%) greater than Effectene, one of the potent commercially available transfecting agents. Most of these geminis protected plasmid DNA remarkably against DNase I in serum, although the degree of stability was found to vary with their structural features.

Conclusions/Significance

-OH groups present on the cationic headgroups in combination with oxyethylene linkers on cholesterol based geminis, gave an optimized combination of new genera of gemini lipids possessing high transfection efficiency even in presence of very high percentage of serum. This property makes them preferential transfection reagents for possible in vivo studies.

Anti-Neoplastic Cytotoxicity of Gemcitabine-(C4-amide)-[anti-HER2/neu] in Combination with Griseofulvin against Chemotherapeutic-Resistant Mammary Adenocarcinoma (SKBr-3)

Introduction

Gemcitabine is a pyrimidine nucleoside analog that becomes triphosphorylated and in this form it competitively inhibits cytidine incorporation into DNA strands. Diphosphorylated gemcitabine irreversibly inhibits ribonucleotide reductase thereby preventing deoxyribonucleotide synthesis. Functioning as a potent chemotherapeutic, gemcitabine decreases neoplastic cell proliferation and induces apoptosis which accounts for its effectiveness in the clinical treatment of several leukemia and carcinoma cell types. A brief plasma half-life due to rapid deamination, chemotherapeuticresistance and sequelae restricts gemcitabine utility in clinical oncology. Selective “targeted” gemcitabine delivery represents a molecular strategy for prolonging its plasma half-life and minimizing innocent tissue/organ exposure.

Methods

A previously described organic chemistry scheme was applied to synthesize a UV-photoactivated gemcitabine intermediate for production of gemcitabine-(C₄-amide)-[anti-HER2/neu]. Immunodetection analysis (Western-blot) was applied to detect the presence of any degradative fragmentation or polymerization. Detection of retained binding-avidity for gemcitabine-(C₄-amide)-[anti-HER2/neu] was determined by cell-ELISA using populations of chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) that highly over-express the HER2/neu trophic membrane receptor. Anti-neoplastic cytotoxicity of gemcitabine-(C₄-amide)-[anti-HER2/neu] and the tubulin/microtubule inhibitor, griseofulvin was established against chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3). Related investigations evaluated the potential for gemcitabine-(C₄-amide)-[anti-HER2/neu] in dual combination with griseofulvin to evoke increased levels of anti-neoplastic cytotoxicity compared to gemcitabine-(C₄-amide)-[anti-HER2/neu].

Results

Covalent gemcitabine-(C₄-amide)-[anti-HER2/neu] immunochemotherapeutic and griseofulvin exerted anti-neoplastic cytotoxicity against chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3). Covalent gemcitabine-(C₄-amide)-[anti-HER2/neu] immunochemotherapeutic or gemcitabine in dual combination with griseofulvin created increased levels of anti-neoplastic cytotoxicity that were greater than was attainable with gemcitabine-(C₄-amide)-[anti-HER2/neu] or gemcitabine alone.

Conclusion

Gemcitabine-(C₄-amide)-[anti-HER2/neu] in dual combination with griseofulvin can produce enhanced levels of anti-neoplastic cytotoxicity and potentially provide a basis for treatment regimens with a wider margin-of-safety. Such benefits would be possible through the collective properties of; [i] selective “targeted” gemcitabine delivery; [ii] relatively lower toxicity of griseofulvin compared to many if not most conventional chemotherapeutics; [iii] reduced total dosage requirements faciliated by additive or synergistic anti-cancer properties; and [iv] differences in sequelae for gemcitabine-(C₄-amide)-[anti-HER2/neu] compared to griseofulvin functioning as a tubulin/microtubule inhibitor.

Influence of Alternative Tubulin Inhibitors on the Potency of a Epirubicin-Immunochemotherapeutic Synthesized with an Ultra Violet Light-Activated Intermediate: Influence of incorporating an internal/integral disulfide bond structure and Alternative Tubulin/Microtubule Inhibitors on the Cytotoxic Anti-Neoplastic Potency of Epirubicin-(C3-amide)-Anti-HER2/neu Synthesized Utilizing a UV-Photoactivated Anthracycline Intermediate

Immunochemotherapeutics, epirubicin-(C₃-amide)-SS-[anti-HER2/neu] with an internal disulfide bond, and epirubicin-(C₃-amide)-[anti-HER2/neu] were synthesized utilizing succinimidyl 2-[(4,4'-azipentanamido) ethyl]-1,3'-dithioproprionate or succinimidyl 4,4-azipentanoate respectively. Western blot analysis was used to determine the presence of any immunoglobulin fragmentation or IgG-IgG polymerization. Retained HER2/neu binding characteristics of epirubicin-(C₃-amide)-[anti-HER2/neu] and epirubicin-(C₃-amide)-SS-[anti-HER2/neu] were validated by cell-ELISA using a mammary adenocarcinoma (SKBr-3) population that highly over-expresses trophic HER2/neu receptor complexes. Cytotoxic anti-neoplastic potency of epirubicin-(C₃-amide)-[anti-HER2/neu] and epirubicin-(C₃-amide)-SS-[anti-HER2/neu] between epirubicin-equivalent concentrations of 10^-10 M and 10^-6 M was determined by measuring the vitality/proliferation of chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3 cell type). Cytotoxic anti-neoplastic potency of benzimidazoles (albendazole, flubendazole, membendazole) and griseofulvin were assessed between 0-to-2 μg/ml and 0-to-100 μg/ml respectively while mebendazole and griseofulvin were analyzed at fixed concentrations of 0.35 μg/ml and 35 g/ml respectively in dual combination with gradient concentrations of epirubicin-(C₃-amide)-[anti-HER2/neu] and epirubicin-(C₃-amide)-SS-[anti-HER2/neu]. Cytotoxic anti-neoplastic potency for epirubicin-(C₃-amide)-[anti-HER2/neu] and epirubicin-(C₃-amide)-SS-[anti-HER2/neu] against chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3) was nearly identical at epirubicin-equivalent concentrations of 10^-10 M and 10^-6 M. The benzimadazoles also possessed cytotoxic anti-neoplastic activity with flubendazole and albendazole being the most and least potent respectively. Similarly, griseofulvin had cytotoxic anti-neoplastic activity and was more potent than methylselenocysteine. Both mebendazole and griseofulvin when applied in dual combination with either epirubicin-(C₃-amide)-[anti-HER2/neu] or epirubicin-(C₃-amide)-SS-[anti-HER2/neu] produced enhanced levels of cytotoxic anti-neoplatic potency.

Synthesis of Gemcitabine-(C4-amide)-[anti-HER2/neu] Utilizing a UV-Photoactivated Gemcitabine Intermediate: Cytotoxic Anti-Neoplastic Activity against Chemotherapeutic-Resistant Mammary Adenocarcinoma SKBr-3

Gemcitabine is a pyrimidine nucleoside analog that becomes triphosphorylated intracellularly where it competitively inhibits cytidine incorporation into DNA strands. Another mechanism-of-action of gemcitabine (diphosphorylated form) involves irreversible inhibition of the enzyme ribonucleotide reductase thereby preventing deoxyribonucleotide synthesis. Functioning as a potent chemotherapeutic gemcitabine promote decreases in neoplastic cell proliferation and apoptosis which is frequently found to be effective for the treatment of several leukemias and a wide spectrum of carcinomas. A brief plasma half-life in part due to rapid deamination and chemotherapeutic-resistance restricts the utility of gemcit-abine in clinical oncology. Selective "targeted" delivery of gemcitabine represents a potential molecular strategy for simultaneously prolonging its plasma half-life and minimizing innocient tissues and organ systems exposure to chemotherapy. The molecular design and an organic chemistry based synthesis reaction is described that initially generates a UV-photoactivated gemcitabine intermediate. In a subsequent phase of the synthesis method the UV-photoactivated gemcitabine intermediate is covalently bonded to a monoclonal immunoglobulin yielding an end-product in the form of gemcitabine-(C₄-amide)-[anti-HER2/neu]. Analysis by SDS-PAGE/chemiluminescent auto-radiography did not detect evidence of gemcitabine-(C₄-amide)-[anti-HER2/neu] polymerization or degradative fragmentation while cell-ELISA demonstrated retained binding-avidity for HER2/neu trophic membrane receptor complexes highly over-expressed by chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3). Compared to chemotherapeutic-resistant mammary adenocarcinoma (SKBr-3), the covalent immunochemotherapeutic, gemcitabine-(C₄-amide)-[anti-HER2/neu] is anticipated to exert greater levels of cytotoxic anti-neoplastic potency against other neoplastic cell types like pancreatic carcinoma, small-cell lung carcinoma, neuroblastoma, glioblastoma, oral squamous cell carcinoma, cervical epitheliod carcinoma, or leukemia/lymphoid neoplastic cell types based on their reported sensitivity to gemcitabine and gemcitabine covalent conjugates.

Thermal targeting of an acid-sensitive doxorubicin conjugate of elastin-like polypeptide enhances the therapeutic efficacy compared with the parent compound in vivo

Elastin-like polypeptides (ELP) aggregate in response to mild hyperthermia, but remain soluble under normal physiologic conditions. ELP macromolecules can accumulate in solid tumors because of the enhanced permeability and retention effect. Tumor retention of ELPs can be further enhanced through hyperthermia-induced aggregation of ELPs by local heating of the tumor. We evaluated the therapeutic potential of ELPs in delivering doxorubicin in the E0771 syngeneic mouse breast cancer model. The ELP-Dox conjugate consisted of a cell-penetrating peptide at the N-terminus and the 6-maleimidocaproyl hydrazone derivative of doxorubicin at the C-terminus of ELP. The acid-sensitive hydrazone linker ensured release of doxorubicin in the lysosomes/endosomes after cellular uptake of the drug conjugate. ELP-Dox dosed at 5 mg doxorubicin equivalent/kg, extended the plasma half-life of doxorubicin to 5.5 hours. In addition, tumor uptake of ELP-Dox increased 2-fold when hyperthermia was applied, and was also enhanced compared to free doxorubicin. Although high levels of doxorubicin were found in the heart of animals treated with free doxorubicin, no detectable levels of doxorubicin were found in ELP-Dox-treated animals, indicating a correlation between tumor targeting and reduction of potential cardiac toxicity by ELP-Dox. At an optimal dose of 12 mg doxorubicin equivalent/kg, ELP-Dox in combination with hyperthermia induced a complete tumor growth inhibition, which was distinctly superior to free drug that only moderately inhibited tumor growth. In summary, our findings show that thermal targeting of ELP increases the potency of doxorubicin underlying the potential of exploiting ELPs to enhance the therapeutic efficacy of conventional anticancer drugs.

Synthesis of a covalent epirubicin-(C(3)-amide)-anti-HER2/neu immunochemotherapeutic utilizing a UV-photoactivated anthracycline intermediate

The C(3)-monoamine on the carbohydrate moiety (daunosamine -NH(2)-3') of epirubicin was reacted under anhydrous conditions with succinimidyl 4,4-azipentanoate to create a covalent UV-photoactivated epirubicin-(C(3)-amide) intermediate with primary amine-reactive properties. A synthetic covalent bond between the UV-photoactivated epirubicin-(C(3)-amide) intermediate and the ɛ-amine of lysine residues within the amino acid sequence of anti-HER2/neu monoclonal immunoglobulin was subsequently created by exposure to UV light (354 nm) for 15 minutes. Size-separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis combined with immunodetection analysis and chemiluminescent autoradiographic imaging revealed a lack of IgG-IgG polymerization or degradative protein fragmentation of the covalent epirubicin-(C(3)-amide)-[anti-HER2/neu] immunochemotherapeutic. Retained binding-avidity of epirubicin-(C(3)-amide)-[anti-HER2/neu] was validated by cell-ELISA utilizing monolayer populations of chemotherapeutic-resistant mammary adenocarcinoma SKBr-3 which highly overexpress membrane-associated HER2/neu complexes. Between epirubicin-equivalent concentrations of 10(-10) to 10(-6) M the covalent epirubicin-(C(3)-amide)-[anti-HER2/neu] immunochemotherapeutic consistently evoked levels of cytotoxic anti-neoplastic potency that were highly analogous to chemotherapeutic-equivalent concentrations of epirubicin. Cytotoxic anti-neoplastic potency of epirubicin-(C(3)-amide)-[anti-HER2/neu] against chemotherapeutic-resistant mammary adenocarcinoma SKBr-3 challenged with epirubicin-(C(3)-amide)-[anti-HER2/neu] at an epirubicin-equivalent concentration of 10(-6) M was 88.5% (e.g., 11.5% residual survival). Between final epirubicin-equivalent concentrations of 10(-8) and 10(-7) M there was a marked threshold increase in the mean cytotoxic anti-neoplastic activity for epirubicin-(C(3)-amide)-[anti-HER2/neu] from 9.9% to 66.9% (90.2% to 33.1% residual survival).

Evaluation of intracellular trafficking and clearance from HeLa cells of doxorubicin-bound block copolymers

New technologies are needed to deliver medicines safely and effectively. Polymeric nanoparticulate carriers are one such technology under investigation. We examined the intracellular trafficking of doxorubicin-bound block copolymers quantitatively and by imaging doxorubicin-derived fluorescence using confocal microscopy. The polymers were internalized by endocytosis and distributed in endosomal/lysosomal compartments and the endoplasmic reticulum; unlike free doxorubicin, the polymers were not found in the nucleus. Moreover, the ATP-binding cassette protein B1 (ABCB1) transporter may be involved in the efflux of the polymer from cells. This drug delivery system is attractive because the endogenous transport system is used for the uptake and delivery of the artificial drug carrier to the target as well as for its efflux from cells to medium. Our results show that a drug delivery system strategy targeting this endogenous transport pathway may be useful for affecting specific molecular targets.

Protein nanocapsules containing doxorubicin as a pH-responsive delivery system

The E2 component of pyruvate dehydrogenase is engineered to form a caged, hollow dodecahedral protein assembly, and the feasibility of this scaffold to be used as a drug delivery system is examined by introducing cysteines to the internal cavity (D381C). The fluorescent dye Alexa Fluor 532 (AF532M) and the antitumor drug doxorubicin are coupled to this internal cavity through maleimides on the guest molecules. The viruslike particle's structure and stability remain intact after binding of the molecules within the interior of the nanocapsule. The pH-dependent hydrolysis of a hydrazone linkage to doxorubicin allows 90% drug release from the D381C scaffold within 72 h at pH 5.0. Fluorescence microscopy of MDA-MB-231 breast cancer cells indicates significant uptake of the D381C scaffold incorporating AF532M and doxorubicin, and suggests internalization of the nanoparticles through endocytosis. It is observed that the protein scaffold does not induce cell death, but doxorubicin encapsulated in D381C is indeed cytotoxic, yielding an IC(50) of 1.3 ± 0.3 μM. While the majority of particulate-based drug delivery strategies encapsulates drugs within polymeric nanoparticles, these results show the potential for using macromolecular protein assemblies. This approach yields a promising new opportunity for designing highly defined nanomaterials for therapeutic delivery.

Epirubicin-[Anti-HER2/neu] Synthesized with an Epirubicin-(C13-imino)-EMCS Analog: Anti-Neoplastic Activity against Chemotherapeutic-Resistant SKBr-3 Mammary Carcinoma in Combination with Organic Selenium

PURPOSE

Discover the anti-neoplastic efficacy of epirubicin-(C₁₃-imino)-[anti-HER2/neu] against chemotherapeutic-resistant SKBr-3 mammary carcinoma and delineate the capacity of selenium to enhance it's cytotoxic anti-neoplastic potency.

METHODS

In molar excess, EMCH was combined with epirubicin to create a covalent epirubicin-(C₁₃-imino)-EMCH-maleimide intermediate with sulfhydryl-reactive properties. Monoclonal immunoglobulin selective for HER2/neu was then thiolated with 2-iminothiolane at the terminal ε-amine group of lysine residues. The sulfhydryl-reactive epirubicin-(C₁₃-imino)-EMCH intermediate was then combined with thiolated anti-HER2/neu monoclonal immunoglobulin. Western-blot analysis was utilized to characterize the molecular weight profiles while binding of epirubicin-(C₁₃-imino)-[anti-HER2/neu] to membrane receptors was determined by cell-ELISA utilizing populations of SKBr-3 mammary carcinoma that highly over-expresses HER2/neu complexes. Anti-neoplastic potency of epirubicin-(C₁₃-imino)-[anti-HER2/neu] between the epirubicin-equivalent concentrations of 10^-12 M and 10^-7 M was determined by vitality staining analysis with and without the presence of selenium (5 μM).

RESULTS

Epiribucin-(C₁₃-imino)-[anti-HER2/neu] between epirubicin-equivalent concentrations of 10^-8 M to 10^-7 M consistently evoked higher anti-neoplastic potency than "free" non-conjugated epirubicin which corresponded with previous investigations utilizing epirubicin-(C₃-amide)-[anti-HER2/neu] and epirubicin-(C₃-amide)-[anti-EGFR]. Selenium at 5 mM consistently enhanced the cytotoxic anti-neoplastic potency of epirubicin-(C13-imino)-[anti-HER2/neu] at epirubicin equivalent concentrations (10-12 to 10-7 M).

CONCLUSIONS

Epirubicin-(C₁₃-imino)-[anti-HER2/neu] is more potent than epirubicin against chemotherapeutic-resistant SKBr-3 mammary carcinoma and selenium enhances epirubicin-(C₁₃-imino)-[anti-HER2/neu] potency. The methodology applied for synthesizing epirubicin-(C₁₃-imino)-[anti-HER2/neu] is relatively time convenient and has low instrumentation requirements.

Synthesis of a covalent gemcitabine-(carbamate)-[anti-HER2/neu] immunochemotherapeutic and its cytotoxic anti-neoplastic activity against chemotherapeutic-resistant SKBr-3 mammary carcinoma

Gemcitabine is a potent chemotherapeutic that exerts cytotoxic activity against several leukemias and a wide spectrum of carcinomas. A brief plasma half-life in part due to rapid deamination and chemotherapeutic-resistance frequently limit the utility of gemcitabine in clinical oncology. Selective 'targeted' delivery of gemcitabine represents a potential molecular strategy for simultaneously prolonging its plasma half-life and minimizing exposure of innocent tissues and organ systems.

MATERIALS AND METHODS

Gemcitabine was combined in molar excess with N-[p-maleimidophenyl]-isocyanate (PMPI) so that the isocyanate moiety of PMPI which exclusively reacts with hydroxyl groups preferentially created a carbamate covalent bond at the terminal C(5)-methylhydroxy group of gemcitabine. Monoclonal immunoglobulin with binding-avidity specifically for HER2/neu was thiolated with 2-iminothiolane at the terminal ε-amine group of lysine amino acid residues. The gemcitabine-(carbamate)-PMPI intermediate with a maleimide moiety that exclusively reacts with reduced sulfhydryl groups was then combined with thiolated anti-HER2/neu monoclonal immunoglobulin. Western-blot analysis was utilized to delineate the molecular weight profile for gemcitabine-(carbamate)-[anti-HER2/neu] while cell binding characteristics were determined by cell-ELISA utilizing SKBr-3 mammary carcinoma which highly over-expresses HER2/neu receptors. Cytotoxic anti-neoplastic potency of gemcitabine-(carbamate)-[anti-HER2/neu] between the gemcitabine-equivalent concentrations of 10(-12) and 10(-6)M was determined utilizing vitality staining analysis of chemotherapeutic-resistant SKBr-3 mammary carcinoma.

RESULTS

Gemcitabine-(carbamate)-[anti-HER2/neu] was synthesized at a molar incorporation index of 1:1.1 (110%) and had a molecular weight of 150kDa that was indistinguishable from reference control immunoglobulin fractions. Cell-ELISA detected progressive increases in SKBr-3 mammary carcinoma associated immunoglobulin with corresponding increases in covalent gemcitabine immunochemotherapeutic concentrations. The in vitro cytotoxic anti-neoplastic potency of gemcitabine-(carbamate)-[anti-HER2/neu] was approximately 20% and 32% at 10(-7) and 10(-6)M (gemcitabine-equivalent concentrations) after a 182-h incubation period.

DISCUSSION

The investigations describes for the first time a methodology for synthesizing a gemcitabine anti-HER2/neu immunochemotherapeutic by creating a covalent bond structure between the C(5)-methylhydroxy group of gemcitabine and thiolated lysine amino acid residues of monoclonal antibody or other biologically active protein fractions. Gemcitabine-(carbamate)-[anti-HER2/neu] possessed binding-avidity at HER2/neu receptors highly over-expressed by chemotherapeutic-resistant SKBr-3 mammary carcinoma. Alternatively, gemcitabine can be covalently linked at its C(5)-methylhydroxy group to monoclonal immunoglobulin fractions that possess binding-avidity for other receptors and membrane complexes uniquely highly over-expressed by a variety of neoplastic cell types. Compared to chemotherapeutic-resistant SKBr-3 mammary carcinoma, gemcitabine-(carbamate)-[anti-HER2/neu] immunochemotherapeutic is anticipated to exert higher levels of cytotoxic anti-neoplastic potency against other neoplastic cell types like pancreatic carcinoma, small-cell lung carcinoma, neuroblastoma, glioblastoma, oral squamous cell carcinoma, cervical epithelioid carcinoma, or leukemia/lymphoid neoplastic cell types based on their reportedly greater sensitivity to gemcitabine and gemcitabine covalent conjugates.

Transferrin receptor-dependent cytotoxicity of artemisinin-transferrin conjugates on prostate cancer cells and induction of apoptosis

Artemisinin, a natural product isolated from Artemisia annua, contains an endoperoxide group that can be activated by intracellular iron to generate toxic radical species. Cancer cells over-express transferrin receptors (TfR) for iron uptake while most normal cells express nearly undetectable levels of TfR. We prepared a series of artemisinin-tagged transferrins (ART-Tf) where different numbers of artemisinin units are attached to the N-glycoside chains of transferrin (Tf). The Tf bearing approximately 16 artemisinins retains the functionality of both Tf and artemisinin. Reduction of TfRs by TfR siRNA transfection significantly impaired the ability of ART-Tf, but not dihydroartemisinin, to kill cells. We also demonstrate that the ART-Tf conjugate kills the prostate carcinoma cell line DU 145 by the mitochondrial pathway of apoptosis.

Genetically engineering transferrin to improve its in vitro ability to deliver cytotoxins

We previously demonstrated that decreasing the iron release rate of transferrin (Tf), by replacing the synergistic anion carbonate with oxalate, increases its in vitro drug carrier efficacy in HeLa cells. In the current work, the utility of this strategy has been further explored by generating two Tf mutants, K206E/R632A Tf and K206E/K534A Tf, exhibiting different degrees of iron release inhibition. The intracellular trafficking behavior of these Tf mutants has been assessed by measuring their association with HeLa cells. Compared to native Tf, the cellular association of K206E/R632A Tf and K206E/K534A Tf increased by 126 and 250%, respectively. Surface plasmon resonance studies clearly indicate that this increase in cellular association is due to a decrease in the iron release rate and not to differences in binding affinity of the mutants to the Tf receptor (TfR). Diphtheria toxin (DT) conjugates of K206E/R632A Tf and K206E/K534A Tf showed significantly increased cytotoxicity against HeLa cells with IC(50) values of 1.00 pM and 0.93 pM, respectively, compared to a value of 1.73 pM for the native Tf conjugate. Besides further validating our strategy of inhibiting iron release, these Tf mutants provide proof-of-principle that site-directed mutagenesis offers an alternative method for improving the drug carrier efficacy of Tf.

Actin disruption inhibits endosomal traffic of P-glycoprotein-EGFP and resistance to daunorubicin accumulation

Intracellular traffic of human P-glycoprotein (P-gp), a membrane transporter responsible for multidrug resistance in cancer chemotherapy, was investigated using a P-gp and enhanced green fluorescent fusion protein (P-gp-EGFP) in human breast cancer MCF-7 cells. The stably expressed P-gp-EGFP from a clonal cell population was functional as a drug efflux pump, as demonstrated by the inhibition of daunorubicin accumulation and the conferring of resistance of the cells to colchicine and daunorubicin. Colocalization experiments demonstrated that a small fraction of the total P-gp-EGFP expressed was localized intracellularly and was present in early endosome and lysosome compartments. P-gp-EGFP traffic was shown to occur via early endosome transport to the plasma membrane. Subsequent movement of P-gp-EGFP away from the plasma membrane occurred by endocytosis to the early endosome and lysosome. The component of the cytoskeleton responsible for P-gp-EGFP traffic was demonstrated to be actin rather than microtubules. In functional studies it was shown that in parallel with the interruption of the traffic of P-gp-EGFP, cellular accumulation of the P-gp substrate daunorubicin was increased after cells were treated with actin inhibitors, and cell proliferation was inhibited to a greater extent than in the presence of daunorubicin alone. The actin dependence of P-gp traffic and the parallel changes in cytotoxic drug accumulation demonstrated in this study delineates the pathways of P-gp traffic and may provide a new approach to overcoming multidrug resistance in cancer chemotherapy.

Inhibition of transferrin iron release increases in vitro drug carrier efficacy

Transferrin (Tf) conjugates of CRM107 are currently being tested in clinical trials for treatment of malignant gliomas. However, the rapid cellular recycling of Tf limits its efficiency as a drug carrier. We have developed a mathematical model of the Tf/TfR trafficking cycle and have identified the Tf iron release rate as a previously unreported factor governing the degree of Tf cellular association. The release of iron from Tf is inhibited by replacing the synergistic carbonate anion with oxalate. Trafficking patterns for oxalate Tf and native Tf are compared by measuring their cellular association with HeLa cells. The amount of Tf associated with the cells is an average of 51% greater for oxalate Tf than for native Tf over a two hour period at Tf concentrations of 0.1 nM and 1 nM. Importantly, diphtheria toxin (DT) conjugates of oxalate Tf are more cytotoxic against HeLa cells than conjugates of native Tf. Conjugate IC(50) values were determined to be 0.06 nM for the oxalate Tf conjugate vs. 0.22 nM for the native Tf conjugate. Thus, we show that inhibition of Tf iron release improves the efficacy of Tf as a drug carrier through increased association with cells expressing TfR.

Correlation of the acid-sensitivity of polyethylene glycol daunorubicin conjugates with their in vitro antiproliferative activity

Polyethylene glycol conjugates with linkers of varying acid-sensitivity were prepared by reacting five maleimide derivatives of daunorubicin containing an amide bond (1) or acid-sensitive carboxylic hydrazone bonds (2-5) with alpha-methoxy-poly(ethylene glycol)-thiopropionic acid amide (MW 20000) or alpha,omega-bis-thiopropionic acid amide poly(ethylene glycol) (MW 20000). The polymer drug derivatives were designed to release daunorubicin inside the tumor cell by acid-cleavage of the hydrazone bond after uptake of the conjugate by endocytosis. In subsequent cell culture experiments, the order of antitumor activity of the PEG daunorubicin conjugates correlated with their acid-sensitivity as determined by HPLC (cell lines: BXF T24 bladder carcinoma and LXFL 529L lung cancer cell line; assay: propidium iodide fluorescence assay). The acid-sensitivity of the link between PEG and daunorubicin is therefore an important parameter for in vitro efficacy.

Targeting liposomes with protein drugs to the blood–brain barrier in vitro

In this study, we aim to target pegylated liposomes loaded with horseradish peroxidase (HRP) and tagged with transferrin (Tf) to the BBB in vitro. Liposomes were prepared with the post-insertion technique: micelles of polyethylene glycol (PEG) and PEG-Tf were inserted into pre-formed liposomes containing HRP. Tf was measured indirectly by measuring iron via atomic absorption spectroscopy. All liposomes were around 100 nm in diameter, contained 5-13 microg HRP per mumol phospholipid and 63-74 Tf molecules per liposome (lipo Tf) or no Tf (lipo C). Brain capillary endothelial cells (BCEC) were incubated with liposomes at 4 degrees C (to determine binding) or at 37 degrees C (to determine association, i.e. binding+endocytosis) and the HRP activity, rather than the HRP amount was determined in cell lysates. Association of lipo Tf was two- to three-fold higher than association of lipo C. Surprisingly, the binding of lipo Tf at 4 degrees C was four-fold higher than the association of at 37 degrees C. Most likely this high binding and low endocytosis is explained by intracellular degradation of endocytosed HRP. In conclusion, we have shown targeting of liposomes loaded with protein or peptide drugs to the BCEC and more specifically to the lysosomes. This is an advantage for the treatment of lysosomal storage disease. However, drug targeting to other intracellular targets also results in intracellular degradation of the drug. Our experiments suggest that liposomes release some of their content within the BBB, making targeting of liposomes to the TfR on BCEC an attractive approach for brain drug delivery.

Dinuclear platinum anticancer complexes with fluorescent N,N′-bis(aminoalkyl)-1,4-diaminoanthraquinones: cellular processing in two cisplatin-resistant cell lines reflects the differences in their resistance profiles

The biological activity of N,N'-bis(aminoalkyl)-1,4-diaminoanthraquinones (aminoalkyl is 2-aminoethyl, 3-aminoprop-1-yl and 4-aminobut-1-yl) and their dinuclear platinum complexes has been evaluated in the U2-OS human osteosarcoma cell line and its cisplatin-resistant U2-OS/Pt subline. All the compounds have been found to exhibit high cytotoxicity in the sensitive cell line, and to overcome cisplatin resistance in U2-OS/Pt cells. Cellular processing of N,N'-bis(2-aminoethyl)-1,4-diaminoanthraquinone and the respective dinuclear platinum complex in the sensitive and resistant U2-OS cells has been studied over time using digital fluorescence microscopy. Cellular processing of the compounds has been found to be similar in sensitive and resistant U2-OS cells, which is in agreement with the lack of cross-resistance in the U2-OS/Pt cell line. Both the platinum complex and the free ligand quickly enter the cell and accumulate in the nucleus. The platinum complex is excreted from the cell via the Golgi apparatus, while the weakly basic anthraquinone ligand accumulates in the Golgi complex, where it is taken up by lysosomes and then transported to the cell surface. The cellular distribution of the fluorescent anthraquinones and their dinuclear platinum complexes in the sensitive/resistant pair of U2-OS osteosarcoma cell lines is compared with the earlier studied cellular processing in the sensitive/resistant pair of A2780 ovarian carcinoma cell lines. In the A2780cisR cell line, the platinum complexes (and not the free ligands) are sequestered in lysosomes, which is not the case in A2780 sensitive cells. The differences in cellular distribution of the compounds in these two sensitive/resistant pairs of cell lines most likely result from different resistance profiles in A2780cisR and U2-OS/Pt cells. Lysosomes of A2780cisR cells are less acidic than lysosomes of A2780 sensitive cells, which is likely to be the cause of a defect in endocytosis. The disruption of normal endocytosis might facilitate sequestration of the platinum complexes in lysosomes, which partly confers the cross-resistance of these complexes with cisplatin in the A2780cisR cell line. In contrast, sequestration in acidic vesicles does not occur in U2-OS/Pt cells that do not exhibit enhanced lysosomal pH and which are likely to have normal endocytosis.

Selective Determination of the Doxorubicin Content of Individual Acidic Organelles in Impure Subcellular Fractions

Since organelle preparations often contain more than one organelle type (e.g., acidic organelles and mitochondria), techniques that measure the properties of a given organelle type while avoiding biases caused by ancillary subcellular compartments are highly desirable. We report here the use of capillary electrophoresis (CE) with laser-induced fluorescence (LIF) dual-channel detection to identify acidic organelles containing doxorubicin (DOX) in crude subcellular fractions from CCRF-CEM and CEM/C2 cell lines. As confirmed by confocal microscopy, acidic organelles are identified by their accumulation of fluorescently labeled nanospheres. Using CE-LIF analysis, individually detected organelles are classified into three kinds: acidic organelles containing only nanospheres, acidic organelles containing nanospheres and DOX, and other organelles containing DOX (e.g., mitochondria) with no detectable nanospheres. Electrophoretic mobility, DOX fluorescence intensity, and nanosphere fluorescence intensity distributions of individual acidic organelles and other organelles containing DOX are determined in the same CE-LIF run. The acidic organelle mobilities range from (-0.7 to -2.0) x 10(-4) cm(2) V(-1) s(-1) while those of the other organelles spread from (-0.6 to -3.5) x 10(-4) cm(2) V(-1) s(-1). In addition, by calibrating the detector response, DOX content in individual acidic organelles and other organelles can be estimated. The average amounts of DOX per acidic organelle in CEM/C2 and CCRF-CEM cells are 11.1 +/- 0.5 and 10.6 +/- 0.4 zmol, respectively. This first report of an analysis of the accumulation of DOX in individual acidic organelles presents a procedure for analyzing the accumulation of fluorescent compounds in acidic organelles that could be useful for investigating acidic organelle maturation and the role of these organelles in drug resistance.

Oligo-3-hydroxybutyrates as potential carriers for drug delivery

In the present paper we describe the synthesis and toxicity studies of well-defined tailor made oligo-[R,S]-3-hydroxybutyrates (OHBs). The results indicate potential applicability of these nano-polymers as drug delivery carriers. Several OHBs of number average molecular weight (M(n)) ranging from 800 to 2400 have been synthesized and tested on transformed hamster V79 fibroblasts and murine melanoma B16(F10) cells using the 3-[4,5-dimethylthiazol-2-yl]2,5-diphenyltetrazolium bromide (MTT) based drug resistance and clonogenic survival assays. We show that 96-h incubation of cells with 1-9 microg/ml of OHBs did not affect cell viability. Incubation of OHBs with rat hepatoma FTO-2B cells stably transfected with chloramphenicol acetyltransferase (CAT) gene ligated to heat-inducible hsp70i gene promoter demonstrated that OHBs did not induce cellular stress response. Finally, we demonstrate that doxorubicin conjugated with OHB is effectively taken up by murine melanoma B16(F10) cells in vitro and localizes in the cytoplasm. These data show for the first time that tailor-made biodegradable and biocompatible oligomers of 3-hydroxybutyric acid can be taken into consideration as effective, non-toxic vectors for delivery of drugs in a conjugated form.

Novel daunorubicin-carrier peptide conjugates derived from human calcitonin segments

Severe and often therapy-limiting side effects are a major obstacle in cancer chemotherapy. New delivery concepts reducing systemic side effects are needed in order to optimize anticancer therapies. Several approaches have been followed, most of them concentrating on macromolecular carriers like liposomes, monoclonal antibodies, serum proteins or polyethylene glycol. We present here a novel type of anthracycline conjugate, using a small carrier peptide derived from the peptide hormone human calcitonin (hCT). The carrier peptide hCT(9-32) has so far been shown to be capable of transporting fluorophores or proteins across cellular membranes. Two different carrier peptide-daunorubicin conjugates were prepared, one with an acid-stable amide bond, the second with an acid-labile hydrazone bond. In vitro studies with daunorubicin linked to the carrier peptide via an acid-labile hydrazone bond demonstrated comparable cytotoxicity to daunorubicin in various daunorubicin sensitive cell lines (neuroblastoma cell lines SK-N-MC and SMS-KAN; HEK 293 T cells). In addition, fluorescence microscopy provided further insight into the mechanism of uptake of the carrier peptide hCT(9-32), indicating that endosomal compartments with reduced pH are involved in the intracellular release of daunorubicin.

Tumor targeting based on the effect of enhanced permeability and retention (EPR) and the mechanism of receptor-mediated endocytosis (RME)

This review is focused on the macromolecular drug carrier systems by the effect of enhanced permeability and retention (EPR) and the mechanism of receptor-mediated endocytosis (RME). The effect of EPR is thought to be useful for the targeting of the macromolecular drugs to the tumor tissues on a vasculolymphatic level. The RME reveals the selective recognition, high affinity binding, and immediate internalization for the ligand on a cellular level. In the receptor, recognizing transferrin, a level of expression on the tumor cells is higher than that on the normal cells. We have used serum albumin and transferrin as drug carriers to deliver mitomycin C (MMC) to the tumor tissues and into the tumor cells. The properties of the conjugates of MMC to serum albumin and transferrin were examined in vitro and in vivo. We concluded that MMC could be delivered to the tumor tissue and cells by the use of albumin and transferrin as drug carriers.

Dinuclear platinum complexes with N,N′-bis(aminoalkyl)-1,4-diaminoanthraquinones as linking ligands. Part I. Synthesis, cytotoxicity, and cellular studies in A2780 human ovarian carcinoma cells

A series of N, N'-bis(aminoalkyl)-1,4-diaminoanthraquinones (aminoalkyl=2-aminoethyl, 3-aminoprop-1-yl and 4-aminobut-1-yl) was functionalized with trans-platinum DNA-binding moieties. Cytotoxicity testing in A2780 human ovarian carcinoma cells revealed high anticancer activity of the formed cationic dinuclear platinum complexes. The cationic dinuclear platinum complexes with the shortest aminoalkyl chain were shown to be the most active, which agrees with the structure-activity relationship found for the corresponding free ligands without platinum. The N, N'-bis(aminoalkyl)-1,4-diaminoanthraquinones partly circumvent cisplatin resistance, whereas their dinuclear platinum complexes were found susceptible to the resistance mechanisms in A2780cisR. The platinum complexes have resistance factors comparable to the control dinuclear complex BBR3005 [(trans-PtCl(NH3)2)2)(micro-(NH2(CH2)6NH2))](NO3)2. The 1,4-diaminoanthraquinone moiety is fluorescent, and thus the cellular processing of the compounds could be monitored by time-lapse digital fluorescence microscopy. The intercalators without platinum were shown to enter the cells within minutes. The platinum complexes enter the cells more slowly. Most likely, the positive charges of the platinum complexes hamper the diffusion through the membrane. Interestingly, the platinum complexes are processed differently than the platinum-free compounds by the cells. After 24 hours the fluorescent platinum complexes are encapsulated in large vesicles in the cytosol. Co-localization of the anthraquinone fluorescence with Lysotracker Green DND-26 shows that these vesicles are acidic compartments, probably lysosomes.

Distribution of zeptomole-abundant doxorubicin metabolites in subcellular fractions by capillary electrophoresis with laser-induced fluorescence detection

Doxorubicin (DOX) treatment of NS-1 mouse hybridoma cells results in the formation of zeptomole amounts of metabolites per cell that are difficult to determine by confocal microscopy or HPLC. The native fluorescence of DOX and its metabolites together with laser-induced fluorescence detection (HF) has previously been used to detect a maximum of four components. In this study, we use capillary electrophoresis with postcolumn LIF (CE-LIF) to separate and detect 12 components attributed to DOX metabolism, resulting from treatment of NS-1 cells with 25 microM DOX for 8 h. The so-called metabolites 8 and 10 have been identified as doxorubicinone (DOXone) and 7-deoxydoxorubicinone (7-deoxyDOXone), respectively, by comigration with the corresponding synthetic standard. Due to comigration of DOX with doxorubicinol (DOXone), the presence of DOXone had to be determined separately by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The rest of the metabolites remain unidentified and are referred to by their number assignment. In comparison with the whole cell lysate, fractionation by differential centrifugation results in a better separation resolution of metabolites due to reduced amounts of metabolites in each fraction. This approach was chosen to compare the distribution of 13 metabolites in three subcellular fractions that form a pellet at < 1,400 g, 1,400-14,000 g, and > 14, 000 g and that generically are enriched in nuclei, organelles (mitochondria and lysosomes), and cytosolic components, respectively. The most abundant metabolite, DOXone, was estimated to be 90 +/- 15, 18 +/- 2, and 60 +/- 12 amol/cell (n = 5) in the nuclear-enriched, organelle-enriched, and cytosole-enriched fractions, respectively. In contrast, the total amount of other metabolites in a given fraction varied from 0 to 1,300 zmol. 7-DeoxyDOXone is the only metabolite that was present at similar levels in the three fractions. Other salient observations are metabolites 3, 7, and 11 are not detectable in the nuclear-enriched, organelle-enriched, and cytosole-enriched fractions, respectively; metabolite 9 and DOXone are more abundant in the nuclear-enriched fraction than in the other two fractions. The observations presented here suggest that subcellular fractionation followed by CE-LIF could be a powerful diagnostic for monitoring drug distribution, which is highly relevant to DOX cytoxicity studies.

Polyethylene glycol-liposomal doxorubicin: a review of its use in the management of solid and haematological malignancies and AIDS-related Kaposi's sarcoma

Polyethylene glycol (PEG)-liposomal doxorubicin is a formulation of the anthracycline doxorubicin in which the drug is encapsulated in PEG-coated liposomes. This alters the pharmacokinetic properties of doxorubicin, prolonging circulation time and enhancing localisation to tumours. In a large randomised trial, intravenous PEG-liposomal doxorubicin was at least as effective as topotecan in patients with ovarian cancer refractory or sensitive to first-line platinum-based chemotherapy. Overall response rates of patients with ovarian cancer refractory to platinum- and paclitaxel-based chemotherapy who received the drug ranged from 18.3 to 27.6% in noncomparative clinical trials. PEG-liposomal doxorubicin also has antitumour activity in patients with metastatic breast cancer pretreated with other chemotherapeutic agents. Overall response rates were similar in patients with pretreated metastatic breast cancer who had received PEG-liposomal doxorubicin or two comparator salvage chemotherapy regimens (vinorelbine or mitomycin C plus vinblastine) in an interim analysis of a large randomised study. In patients with advanced AIDS-related Kaposi's sarcoma, PEG-liposomal doxorubicin monotherapy produced overall response rates ranging from 46 to 77% in randomised trials. The drug was significantly more effective than bleomycin plus vincristine alone or in combination with standard doxorubicin, as measured by tumour response. As a replacement for standard doxorubicin in commonly used combination therapies, PEG-liposomal doxorubicin has shown activity in multiple myeloma and aggressive non-Hodgkin's lymphoma in small, preliminary trials. The most common adverse events associated with PEG-liposomal doxorubicin are myelosuppression, palmar-plantar erythrodysaesthesia, stomatitis and nausea. These can be managed by delaying or reducing dosages. Although preliminary trials are promising, the relative cardiotoxicity of PEG-liposomal doxorubicin compared with the standard formulation has not been clearly established.

CONCLUSIONS

Monotherapy with PEG-liposomal doxorubicin is effective as a second-line chemotherapy in patients with platinum-refractory ovarian cancer and in patients with metastatic breast cancer. However, as with all chemotherapeutic agents, the benefits of treatment need to be weighed against the agent's tolerability profile. Strong comparative data have helped to establish PEG-liposomal doxorubicin as the first-line treatment option in patients with advanced Kaposi's sarcoma. Anticancer activity has also been observed in studies conducted in small numbers of patients with multiple myeloma or non-Hodgkin's lymphoma receiving PEG-liposomal doxorubicin instead of standard doxorubicin in combination regimens, although further data are needed to confirm the clinical relevance of these findings.

Probing the cysteine-34 position of endogenous serum albumin with thiol-binding doxorubicin derivatives. Improved efficacy of an acid-sensitive doxorubicin derivative with specific albumin-binding properties compared to that of the parent compound

We have recently proposed a macromolecular prodrug strategy for improved cancer chemotherapy based on two features (Kratz, F.; et al. J. Med. Chem 2000, 43, 1253-1256.): (a) rapid and selective binding of thiol-reactive prodrugs to the cysteine-34 position of endogenous albumin after intravenous administration and (b) release of the albumin-bound drug in the acidic environment at the tumor site due to the incorporation of an acid-sensitive bond between the drug and the carrier. To investigate this therapeutic strategy in greater depth, four (maleinimidoalkanoyl)hydrazone derivatives of doxorubicin were synthesized differing in the length of the aliphatic spacer (1, -(CH(2))(2)-; 2, -(CH(2))(3)-; 3, -(CH(2))(5)-; 4, -(CH(2))(7)-). The albumin-binding doxorubicin prodrugs, especially the (6-maleimidocaproyl)hydrazone derivative of doxorubicin (3), are rapidly and selectively bound to the cysteine-34 position of endogenous albumin. 3 was distinctly superior to the parent compound doxorubicin in three animal tumor models (RENCA, MDA-MB 435, and MCF-7) with respect to antitumor efficacy and toxicity.