Therapeutic Efficacy Of Anticancer Drugs Research Articles

Assessment and optimization of electroporation-assisted tumoral nanoparticle uptake in a nude mouse model of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a particularly lethal form of cancer. In 2012, the incidence of PDAC was 43,920. Five-year survival for patients with PDAC is around 6%, regardless of staging, making PDAC one of the deadliest forms of cancer. One reason for this dismal prognosis is chemoresistance to the current first-line therapy, gemcitabine. There are multiple factors that contribute to the chemoresistance observed in pancreatic cancer. Among them, desmoplasia has been increasingly seen as a significant contributor to chemoresistance. To overcome desmoplastic chemoresistance, several novel methods of treatment have been developed. Electroporation is one such novel treatment. High electrical fields are applied to cells to create pores that increase cell permeability. It has been previously demonstrated that electroporation enhances the therapeutic efficacy of anticancer drugs in pancreatic tumor models. Nanoparticle-based drug delivery systems constitute a second novel method to overcome desmoplastic chemoresistance. Due to their intrinsic design advantages, nanoparticles have been shown to increase the effectiveness of chemotherapeutic agents, while further reducing or even eliminating side effects. To date, there have been no studies evaluating the cumulative effect of combining both nanoparticle and electroporation strategies to overcome chemoresistance in PDAC. Our preliminary studies assessed the in vitro and in vivo uptake of doxorubicin-loaded iron oxide nanoparticles as a function of electroporation voltage and timing of administration in pancreatic adenocarcinoma cells. Our studies demonstrated that addition of electroporation to administration of nanoparticles significantly increased the amount of intracellular iron oxide nanoparticle uptake by a PANC-1 cell line in an athymic nude mouse model of PDAC. Further, electroporation-assisted nanoparticle uptake could be significantly altered by changing the timing of application of electroporation.

ATP-triggered anticancer drug delivery

Stimuli-triggered drug delivery systems have been increasingly used to promote physiological specificity and on-demand therapeutic efficacy of anticancer drugs. Here we utilize adenosine-5'-triphosphate (ATP) as a trigger for the controlled release of anticancer drugs. We demonstrate that polymeric nanocarriers functionalized with an ATP-binding aptamer-incorporated DNA motif can selectively release the intercalating doxorubicin via a conformational switch when in an ATP-rich environment. The half-maximal inhibitory concentration of ATP-responsive nanovehicles is 0.24 μM in MDA-MB-231 cells, a 3.6-fold increase in the cytotoxicity compared with that of non-ATP-responsive nanovehicles. Equipped with an outer shell crosslinked by hyaluronic acid, a specific tumour-targeting ligand, the ATP-responsive nanocarriers present an improvement in the chemotherapeutic inhibition of tumour growth using xenograft MDA-MB-231 tumour-bearing mice. This ATP-triggered drug release system provides a more sophisticated drug delivery system, which can differentiate ATP levels to facilitate the selective release of drugs.

Nanodrug Delivery Systems: A Promising Technology for Detection, Diagnosis, and Treatment of Cancer

Nanotechnology has enabled the development of novel therapeutic and diagnostic strategies, such as advances in targeted drug delivery systems, versatile molecular imaging modalities, stimulus responsive components for fabrication, and potential theranostic agents in cancer therapy. Nanoparticle modifications such as conjugation with polyethylene glycol have been used to increase the duration of nanoparticles in blood circulation and reduce renal clearance rates. Such modifications to nanoparticle fabrication are the initial steps toward clinical translation of nanoparticles. Additionally, the development of targeted drug delivery systems has substantially contributed to the therapeutic efficacy of anti-cancer drugs and cancer gene therapies compared with nontargeted conventional delivery systems. Although multifunctional nanoparticles offer numerous advantages, their complex nature imparts challenges in reproducibility and concerns of toxicity. A thorough understanding of the biological behavior of nanoparticle systems is strongly warranted prior to testing such systems in a clinical setting. Translation of novel nanodrug delivery systems from the bench to the bedside will require a collective approach. The present review focuses on recent research efforts citing relevant examples of advanced nanodrug delivery and imaging systems developed for cancer therapy. Additionally, this review highlights the newest technologies such as microfluidics and biomimetics that can aid in the development and speedy translation of nanodrug delivery systems to the clinic.

Milk Thistle’s Active Components Silybin and Isosilybin: Novel Inhibitors of PXR-Mediated CYP3A4 Induction

Because cancer is often treated with combination therapy, unexpected pharmacological effects can occur because of drug-drug interactions. Several drugs are able to cause upregulation or downregulation of drug transporters or cytochrome P450 enzymes, particularly CYP3A4. Induction of CYP3A4 may result in decreased plasma levels and therapeutic efficacy of anticancer drugs. Since the pregnane X receptor (PXR) is one of the major transcriptional regulators of CYP3A4, PXR antagonists can possibly prevent CYP3A4 induction. Currently, a limited number of PXR antagonists are available. Some of these antagonists, such as sulphoraphane and coumestrol, belong to the so-called complementary and alternative medicines (CAM). Therefore, the aim was to determine the potential of selected CAM (β-carotene, Echinacea purpurea, garlic, Ginkgo biloba, ginseng, grape seed, green tea, milk thistle, saw palmetto, valerian, St. John's Wort, and vitamins B6, B12, and C) to inhibit PXR-mediated CYP3A4 induction at the transcriptional level, using a reporter gene assay and a real-time polymerase chain reaction assay in LS180 colon adenocarcinoma cells. Furthermore, computational molecular docking and a LanthaScreen time-resolved fluorescence resonance energy transfer (TR-FRET) PXR competitive binding assay were performed to explore whether the inhibiting CAM components interact with PXR. The results demonstrated that milk thistle is a strong inhibitor of PXR-mediated CYP3A4 induction. The components of milk thistle responsible for this effect were identified as silybin and isosilybin. Furthermore, computational molecular docking revealed a strong interaction between both silybin and isosilybin and PXR, which was confirmed in the TR-FRET PXR assay. In conclusion, silybin and isosilybin might be suitable candidates to design potent PXR antagonists to prevent drug-drug interactions via CYP3A4 in cancer patients.

Abstract LB-95: Construction and application of elastin-like polypeptide containing IL-4 receptor targeting peptide.

Abstract Cancer cells express a number of cell surface and matrix proteins that mediate tumor growth, migration, invasion, and metastasis. Screening for ligands that specifically target these molecules represents an excellent cancer therapy strategy. AP1 is a recently discovered peptide, homing onto atherosclerotic plaques and breast tumor tissues through selective binding to the interleukin 4 receptor (IL-4R). IL-4Rs are highly expressed in a variety of human tumors and it has been reported that IL-4/IL-4R interactions amplify the expression of some anti-apoptotic proteins thereby preventing drug-induced cancer cell death. Thus, targeting the IL-4R could possibly increase the therapeutic efficacy of anticancer drugs. Even though AP1 peptide possesses high target specificity and efficient tumor-homing, it has limitation due to easy elimination from the circulation and short half-life. To improve the binding affinity of AP1 and its avidity towards the IL-4R as well as its half-life, we incorporated multiple AP1 peptides into the elastin-like polypeptides (ELPs). Tandem repeats of ELP polymers containing AP1 peptide (AP1-ELPs) were prepared by using recursive directional ligation (RDL) method. The fluorescence-labeled A6V72, an AP1-ELP containing six AP1 units displayed superior binding ability to the IL-4R expressing cancer cell lines, H226 and MDA-MB-231. Surface plasmon resonance analysis showed that multivalent presentation of the targeting ligand AP1 in the ELP polymer backbone increased binding affinity to IL-4R approximately ~10, 000-fold compared to the free AP1 peptide, which is important for tumor targeting approach. The binding of AP1-ELPs was remarkably reduced when IL-4Rs were blocked with antibody against IL-4 receptor. Confocal microscopic imaging revealed the increased accumulation and uptake of A6V72 than V84 control ELP by H226 cells. Furthermore, the Cy5.5-labeled AP1-ELP showed excellent homing and longer retention in xenografted tumor tissues in mouse model. Immunohistological analysis of excised tumor tissues further verified the targeting of AP1-ELP to tumor. The present results imply that the AP1-ELPs can serve as novel carriers for effective delivery of therapeutic drugs to tumors. Citation Format: Sarangthem Vijaya Devi, Rang-Woon Park. Construction and application of elastin-like polypeptide containing IL-4 receptor targeting peptide. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-95. doi:10.1158/1538-7445.AM2013-LB-95

Stealth properties to improve therapeutic efficacy of drug nanocarriers.

Over the last few decades, nanocarriers for drug delivery have emerged as powerful tools with unquestionable potential to improve the therapeutic efficacy of anticancer drugs. Many colloidal drug delivery systems are underdevelopment to ameliorate the site specificity of drug action and reduce the systemic side effects. By virtue of their small size they can be injected intravenously and disposed into the target tissues where they release the drug. Nanocarriers interact massively with the surrounding environment, namely, endothelium vessels as well as cells and blood proteins. Consequently, they are rapidly removed from the circulation mostly by the mononuclear phagocyte system. In order to endow nanosystems with long circulation properties, new technologies aimed at the surface modification of their physicochemical features have been developed. In particular, stealth nanocarriers can be obtained by polymeric coating. In this paper, the basic concept underlining the “stealth” properties of drug nanocarriers, the parameters influencing the polymer coating performance in terms of opsonins/macrophages interaction with the colloid surface, the most commonly used materials for the coating process and the outcomes of this peculiar procedure are thoroughly discussed.

P03.13 - Green Tea Polyphenols Enhance Therapeutic Efficacy of Anticancer Drugs as to Drug-Resistant Experimental Tumors

P03.13 - Green Tea Polyphenols Enhance Therapeutic Efficacy of Anticancer Drugs as to Drug-Resistant Experimental Tumors

Toward the Next-Generation Nanomedicines: Design of Multifunctional Multiblock Polyurethanes for Effective Cancer Treatment

Specific accumulation of therapeutics at tumor sites to improve in vivo biodistribution and therapeutic efficacy of anticancer drugs is a major challenge for cancer therapy. Herein, we demonstrate a new generation of intelligent nanosystem integrating multiple functionalities in a single carrier based on multifunctional multiblock polyurethane (MMPU). The smart nanocarriers equipped with stealth, active targeting, and internalizable properties can ferry paclitaxel selectively into tumor tissue, rapidly enter cancer cells, and controllably release their payload in response to an intracellular acidic environment, thus resulting in an improved biodistribution and excellent antitumor activity in vivo. Our work provides a facile and versatile approach for the design and fabrication of smart intracellular targeted nanovehicles for effective cancer treatment, and opens a new era in the development of biodegradable polyurethanes for next-generation nanodelivery systems.

Improving Drug Uptake and Penetration into Tumors: Current and Forthcoming Opportunities

Improving Drug Uptake and Penetration into Tumors: Current and Forthcoming Opportunities

Increasing the antitumor efficacy of doxorubicin-loaded liposomes with peptides anchored via a chelator lipid

The therapeutic efficacy of anticancer drugs like doxorubicin can be significantly increased by their incorporation into liposomes, but an ability to actively target the drug-containing liposomes to tumors could well provide an even greater curative effect. In this work, a commercial preparation of doxorubicin-loaded liposomes (Caelyx) was modified by incorporation of the metal chelator lipid 3(nitrilotriacetic acid)-ditetradecylamine (NTA3-DTDA) to enable engraftment of histidine-tagged targeting molecules. Our results show that when engrafted with p15-RGR, a His-tagged peptide containing a sequence purported to bind platelet-derived growth factor receptor β (PDGFRβ), NTA3-DTDA-containing Caelyx (3NTA-Caelyx) can be targeted to NIH-3T3 cells in vitro, leading to increased cytotoxicity compared with non-targeted 3NTA-Caelyx. PDGFRβ is known to be expressed on pericytes in the tumor vasculature; however, when radiolabeled p15-RGR liposomes were administered to mice bearing subcutaneous B16-F1 tumors, minimal accumulation into tumors was observed. In contrast, an alternative targeting peptide, p46-RGD, was found to actively direct liposomes to tumors (4.7 %ID/g). Importantly, when injected into tumor-bearing mice, p46-RGD-engrafted 3NTA-Caelyx significantly decreased the tumor growth rate compared with controls. These results indicate that the incorporation of NTA3-DTDA into liposomal drugs could represent a simple modification to the drug to allow engraftment of targeting molecules and to increase its efficacy.

Scope of nanotechnology in ovarian cancer therapeutics

This review describes the use of polymer micelle nanotechnology based chemotherapies for ovarian cancer. While various chemotherapeutic agents can be utilized to improve the survival rate of patients with ovarian cancer, their distribution throughout the entire body results in high normal organ toxicity. Polymer micelle nanotechnology aims to improve the therapeutic efficacy of anti-cancer drugs while minimizing the side effects. Herein, different types of polymer micelle technology based nanotherapies such as PLGA, polymerosomes, acid cleavable, thermosensitive, pH sensitive, and cross-linked micelles are introduced and structural differences are explained. Additionally, production methods, stability, sustainability, drug incorporation and drug release profiles of various polymer micelle based nanoformulations are discussed. An important feature of polymer micelle nanotechnology is the small size (10-100 nm) of particles which improves circulation and enables superior accumulation of the therapeutic drugs at the tumor sites. This review provides a comprehensive evaluation of different types of polymer micelles and their implications in ovarian cancer therapeutics.

Advances in Novel Drug Delivery Strategies for Breast Cancer Therapy

Breast cancer remains one of the world's most devastating diseases. However, better understanding of tumor biology and improved diagnostic devices could lead to improved therapeutic outcomes. Nanotechnology has the potential to revolutionize cancer diagnosis and therapy. Various nanocarriers have been introduced to improve the therapeutic efficacy of anticancer drugs, including liposomes, polymeric micelles, quantum dots, nanoparticles, and dendrimers. Recently, targeted drug delivery systems for anti-tumor drugs have demonstrated great potential to lower cytotoxicity and increase therapeutic effects. Various ligands/approaches have been explored for targeting breast cancer. This paper provides an overview of breast cancer, conventional therapy, potential of nanotechnology in management of breast cancer, and rational approaches for targeting breast cancer.

A novel approach to deliver anticancer drugs to key cell types in tumors using a PDGF receptor-binding cyclic peptide containing carrier

Tumor stromal cells have been recently recognized to contribute to tumor growth. Therefore, we hypothesized that delivery of anticancer drugs to these cells in addition to the tumor cells might treat cancer more effectively. Stromal cells abundantly expressed Platelet-Derived Growth Factor Receptor-beta (PDGFR-β) in different human tumors as shown with immunohistochemistry. To achieve targeting through PDGFR-β, we developed a carrier by modifying albumin with a PDGFR-β recognizing cyclic peptide (pPB-HSA). pPB-HSA specifically bound to PDGFR-β-expressing 3T3 fibroblasts, C26 and A2780 cancer cells in vitro. Subsequently, doxorubicin was conjugated to pPB-HSA through an acid-sensitive hydrazone linkage. In vitro, Dox-HSA-pPB was taken up by fibroblasts and tumor cells and a short exposure of the conjugate induced cell death in these cells. In vivo, the conjugate rapidly accumulated into PDGFR-β expressing cells in C26 tumors. Treatment with Dox-HSA-pPB significantly reduced the C26 tumor growth in mice while free doxorubicin treated mice had lower response to the therapy. Furthermore, in contrast to free doxorubicin the conjugate did not induce loss in body weight. In conclusion, the present study reveals a novel approach to target key cell types in tumors through PDGFR-β, which can be applied to enhance the therapeutic efficacy of anticancer drugs.

Blockade of the Extracellular Signal-Regulated Kinase Pathway Enhances the Therapeutic Efficacy of Microtubule-Destabilizing Agents in Human Tumor Xenograft Models

The extracellular signal-regulated kinase (ERK) pathway is upregulated in human cancers and represents a target for mechanism-based approaches to cancer treatment. However, specific blockade of the ERK pathway alone induces mostly cytostatic rather than proapoptotic effects, resulting in a limited therapeutic efficacy of inhibitors that target the mitogen-activated protein kinase/ERK kinase (MEK). Given the cytoprotective role of the ERK pathway, we examined whether its blockade by the MEK inhibitor PD184352 might enhance the therapeutic efficacy of anticancer drugs in human tumor xenograft models. We recently showed that blockade of the ERK pathway by MEK inhibitors enhances the induction of apoptosis by microtubule-destabilizing agents, including TZT-1027 and vinorelbine, in various tumor cells with aberrant activation of the ERK pathway in vitro. We here examined the therapeutic efficacy of the combination of PD184352 with TZT-1027 or vinorelbine in nude mice harboring HT-29 or HT1080 tumor xenografts, in which the ERK pathway is activated as a result of mutations of BRAF and NRAS, respectively. Coadministration of PD184352 markedly sensitized HT-29 or HT1080 tumor xenografts to TZT-1027-induced or vinorelbine-induced cytotoxicity. Low doses of TZT-1027 or vinorelbine that by themselves showed little or moderate cytotoxicity thus suppressed the growth of HT-29 xenografts almost completely and induced essentially complete regression of HT1080 xenografts when administered with PD184352. The enhanced therapeutic efficacy of the drug combinations was achieved by a relatively transient blockade of the ERK pathway. Administration of both a MEK inhibitor and a microtubule-destabilizing agent represents a promising chemotherapeutic strategy with improved safety for cancer patients.

Tumor‐targeted intracellular delivery of anticancer drugs through the mannose‐6‐phosphate/insulin‐like growth factor II receptor

Tumor-targeting of anticancer drugs is an interesting approach for the treatment of cancer since chemotherapies possess several adverse effects. In the present study, we propose a novel strategy to deliver anticancer drugs to the tumor cells through the mannose-6-phosphate/insulin-like growth factor receptor (M6P/IGF-IIR) which are abundantly expressed in several human tumors. We developed a drug carrier against M6P/IGF-II receptor by modifying human serum albumin (HSA) with M6P moieties. M6P-HSA specifically bound and internalized into M6P/IGF-IIR-expressing B16 melanoma cells as demonstrated with radioactive studies and anti-HSA immunostaining. In vivo, M6P-HSA rapidly accumulated in subcutaneous tumors in tumor and stromal components after an intravenous injection. To demonstrate the application of M6P-HSA as a drug carrier, we coupled doxorubicin to it. Dox-HSA-M6P conjugate could release doxorubicin at lysosomal pH and showed M6P-specific binding and uptake in tumor cells. In vitro, a short exposure with Dox-HSA-M6P induced killing of tumor cells, which could be blocked by excess M6P-HSA. In vivo, Dox-HSA-M6P distributed to tumors and some other organs while free doxorubicin distributed to all organs but slightly to tumors. In B16 tumor-bearing mice, Dox-HSA-M6P significantly inhibited the tumor growth whereas an equimolar dose of free doxorubicin did not show any anti-tumor effect. In addition, targeted doxorubicin did not show any side-effects on liver and kidney function tests, body weight and blood cell counts. In conclusion, M6P-HSA is a suitable carrier for delivery of anticancer drugs to tumors through M6P/IGF-IIR. Improved antitumor effects of the targeted doxorubicin by M6P-HSA suggest that this novel approach may be applied to improve the therapeutic efficacy of anticancer drugs.

Polyethylene glycol-complexed cationic liposome for enhanced cellular uptake and anticancer activity

Liposomes as one of the efficient drug carriers have some shortcomings such as their relatively short blood circulation time, fast clearance from human body by reticuloendothelial system (RES) and limited intracellular uptake to target cells. In this study, polyethylene glycol (PEG)-complexed cationic liposomes (PCL) were prepared by ionic complex of cationically charged liposomes with carboxylated polyethylene glycol (mPEG-COOH). The cationic liposomes had approximately 98.6 ± 1.0 nm of mean particle diameter and 45.5 ± 1.1 mV of zeta potential value. While, the PCL had 110.1 ± 1.2 nm of mean particle diameter and 18.4 ± 0.8 mV of zeta potential value as a result of the ionic complex of mPEG-COOH with cationic liposomes. Loading efficiency of model drug, doxorubicin, into cationic liposomes or PCL was about 96.0 ± 0.7%. Results of intracellular uptake evaluated by flow cytometry and fluorescence microscopy studies showed higher intracellular uptake of PCL than that of Doxil ®. In addition, in vitro cytotoxicity of PCL was comparable to cationic liposomes. In pharmacokinetic study in rats, PCL showed slightly lower plasma level of DOX than that of Doxil ®. In vivo antitumor activity of DOX-loaded PCL was comparable to that of Doxil ® against human SKOV-3 ovarian adenocarcinoma xenograft rat model. Consequently, the PCL, of which surface was complexed with PEG by ionic complex may be applicable as drug delivery carriers for increasing therapeutic efficacy of anticancer drugs.

Utility of antioncogene ribozymes and antisense oligonucleotides in reversing drug resistance.

The development of new anticancer drugs and the identification of novel targets are a major focus for pharmaceutical and biotech companies, universities, and research institutes worldwide (). However, the therapeutic efficacy of anticancer drugs against malignant diseases is limited because of the selection and regrowth of drug-resistant cells. The development of approaches to overcome and/or circumvent drug resistance will depend on a precise understanding of the mechanisms of resistance not only at the target tumor cell level but also in vivo. Resistance to treatment with anticancer drugs results from a variety of factors including individual variations in patients and genetic differences in somatic cells in tumors. We have focused on two anticancer drugs: cisplatin, which is exceptionally effective against testicular cancer, ovarian cancer, and others (); and Ara-C (1-β-d-arabinofuranosyl cytidine, cytosine arabinoside), now a standard for the treatment of acute and chronic leukemia ().

Selective modulation of the therapeutic efficacy of anticancer drugs by selenium containing compounds against human tumor xenografts.

Studies were carried out in athymic nude mice bearing human squamous cell carcinoma of the head and neck (FaDu and A253) and colon carcinoma (HCT-8 and HT-29) xenografts to evaluate the potential role of selenium-containing compounds as selective modulators of the toxicity and antitumor activity of selected anticancer drugs with particular emphasis on irinotecan, a topoisomerase I poison. Antitumor activity and toxicity were evaluated using nontoxic doses (0.2 mg/mouse/day) and schedule (14-28 days) of the selenium-containing compounds, 5-methylselenocysteine and seleno-L-methionine, administered orally to nude mice daily for 7 days before i.v. administration of anticancer drugs, with continued selenium treatment for 7-21 days, depending on anticancer drugs under evaluation. Several doses of anticancer drugs were used, including the maximum tolerated dose (MTD) and toxic doses. Although many chemotherapeutic agents were evaluated for toxicity protection by selenium, data on antitumor activity were primarily obtained using the MTD, 2 x MTD, and 3 x MTD of weekly x4 schedule of irinotecan. Selenium was highly protective against toxicity induced by a variety of chemotherapeutic agents. Furthermore, selenium increased significantly the cure rate of xenografts bearing human tumors that are sensitive (HCT-8 and FaDu) and resistant (HT-29 and A253) to irinotecan. The high cure rate (100%) was achieved in nude mice bearing HCT-8 and FaDu xenografts treated with the MTD of irinotecan (100 mg/kg/week x 4) when combined with selenium. Administration of higher doses of irinotecan (200 and 300 mg/kg/week x 4) was required to achieve high cure rate for HT-29 and A253 xenografts. Administration of these higher doses was possible due to selective protection of normal tissues by selenium. Thus, the use of selenium as selective modulator of the therapeutic efficacy of anticancer drugs is new and novel. We demonstrated that selenium is a highly effective modulator of the therapeutic efficacy and selectivity of anticancer drugs in nude mice bearing human tumor xenografts of colon carcinoma and squamous cell carcinoma of the head and neck. The observed in vivo synergic interaction is highly dependent on the schedule of selenium.

Current status of the molecular mechanisms of anticancer drug-induced apoptosis. The contribution of molecular-level analysis to cancer chemotherapy.

Apoptosis is an important phenomenon in cytotoxicity induced by anticancer drugs. Here, we review the current status of the molecular mechanisms of anticancer drug-induced apoptosis in order to assess the contribution of molecular-level analysis to cancer chemotherapy. It is apparent that the molecular mechanisms by which anticancer drugs induce apoptosis are mediated by death receptor-dependent and -independent pathways, which are related to the release of cytochrome c through voltage-dependent anion channels in the mitochondrial inner membrane. The release of cytochrome c is the central gate in turning on/off apoptosis, and is regulated by the interaction of proapoptotic proteins, including Bid, Bax and Bak, and antiapoptotic proteins including Bcl-2 and Bcl-X(L), and a specific class of inhibitors of apoptosis proteins (IAPs) including Akt, survivin, and heat-shock proteins. The caspase cascade is activated by the release of cytochrome c, which is initiated by the formation of apoptosomes consisting of procaspase-9, Apaf-1 and cytochrome c in the presence of dATP, and results in the activation of caspase-9 and caspase-3, thereby leading to apoptosis. Drug sensitivity can be enhanced by the introduction of proapoptotic genes and the inhibition of antiapoptotic proteins. The latter process is mediated by antisense oligonucleotides and is associated with apoptosis. The signal transduction pathways that are triggered by the central gate in mitochondria play a critical role in anticancer drug-induced apoptosis. The modulation of signal transduction pathways targeting the proteins involved in these signal transduction pathways using antisense IAPs, and growth factor antibodies may be a good strategy for enhancing therapeutic efficacy of anticancer drugs in cancer chemotherapy.

Synthesis and characterization of HPMA copolymer–aminopropylgeldanamycin conjugates

Geldanamycin (GDM) is a benzoquinone ansamycin antibiotic with anticancer activity. The use of drug delivery systems based on N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers containing lysosomally degradable oligopeptide (GFLG) spacers results in an increased therapeutic efficacy of anticancer drugs. The objective of this study was to synthesize HPMA copolymer–GDM conjugates with anticancer activity and reduced toxic side-effect of the compound. 17-(3-Aminopropylamino)-17-demethoxygeldanamycin (AP-GDM) was synthesized and converted into a polymerizable GDM derivative, N-methacryloylglycylphenylalanylglycyl-17-(3-aminopropylamino)-17-demethoxygeldanamycin [MA-GFLG-(AP-GDM)]. The structures of AP-GDM and MA-GFLG-(AP-GDM) were validated by mass spectroscopy, elemental analysis, and two-dimensional nuclear magnetic resonance. MA-GFLG-(AP-GDM) was copolymerized with HPMA and N-methacryloyglycylglycine p-nitrophenylester by radical precipitation polymerization. Water-soluble HPMA copolymer–AP-GDM conjugates ( M r=16 kDa) were obtained. Monoclonal antibody OV-TL16, which recognizes the OA-3 antigen expressed on the OVCAR-3 human ovarian carcinoma cell line, was optionally attached to the HPMA copolymer–AP-GDM conjugate. Cytotoxicity of polymer-bound AP-GDM (both targeted and non-targeted) was determined using OVCAR-3 and another human ovarian carcinoma cell line, A2780. The HPMA copolymer–AP-GDM conjugate was cytotoxic toward A2780 cells. Attachment of OV-TL16 antibody enhanced cytotoxicity of the conjugate toward OVCAR-3 cells.