Molecular Targeting of BCL2 and BCLXL Proteins by Synthetic BCL2 Homology 3 Domain Peptide Enhances the Efficacy of Chemotherapy

Gonadotropin-Dependent Neuregulin-1 Signaling Regulates Female Rat Ovarian Granulosa Cell Survival

Mammalian ovarian follicular development and maturation of an oocyte competent to be fertilized and develop into an embryo depends on tightly regulated, spatiotemporally orchestrated crosstalk among cell death, survival, and differentiation signals through extra- and intraovarian signals, as well as on a permissive ovarian follicular microenvironment. Neuregulin-1 (NRG1) is a member of the epidermal growth factor-like factor family that mediates its effects by binding to a member of the erythroblastoma (ErbB) family. Our experimental results suggest gonadotropins promote differential expression of NRG1 and erbB receptors in granulosa cells (GCs), and NRG1 in theca cells during follicular development, and promote NRG1 secretions in the follicular fluid (FF) of rat ovaries. During the estrous cycle of rat, NRG1 and erbB receptors are differentially expressed in GCs and correlate positively with serum gonadotropins and steroid hormones. Moreover, in vitro experimental studies suggest that the protein kinase C inhibitor staurosporine (STS) causes the physical destruction of GCs by the activation of caspase-3. Exogenous NRG1 treatment of GCs delayed onset of STS-induced apoptosis and inhibited cleaved caspase-3 expressions. Moreover, exogenous NRG1 treatment of GCs alters STS-induced death by maintaining the expression of ErbB2, ErbB3, pAkt, Bcl2, and BclxL proteins. Taken together, these studies demonstrate that NRG1 is gonadotropin dependent, differentially regulated in GCs and theca cells, and secreted in ovarian FF as an intracellular survival factor that may govern follicular maturation.

Precision targeted therapy of ovarian cancer

The review is aimed at describing modern approaches to detection as well as precision and personalized treatment of ovarian cancer. Modern methods and future directions of nanotechnology-based targeted and personalized therapy are discussed.

Enhanced efficacy of chemotherapy for breast cancer stem cells by simultaneous suppression of multidrug resistance and antiapoptotic cellular defense

While chemotherapy is universally recognized as a frontline treatment strategy for breast cancer, it is not always successful; among the leading causes of treatment failure is existing and/or acquired multidrug resistance. Cancer stem cells (CSCs), which constitute a minority of the cells of a tumor, are acknowledged to be responsible for increased resistance to chemo-drugs through a combination of increased expression of ATP-binding cassette transporters (ABC transporters), an increased anti-apoptotic defense, and/or the ability for extensive DNA repair like normal stem cells. Consequently, more effective therapy, especially targeted to CSCs, is urgently required. We studied the characteristics of 231-CSCs (CD44+/CD24-) sorted from human MDA-MB-231 breast cancer cells and demonstrated that 231-CSCs exhibited enhanced capacities for proliferation, migration, tumorigenesis and chemotherapy resistance. To address these multifunctional facets of CSCs, we devised a non-ionic surfactant-based vesicle (niosome) co-delivery system to simultaneously deliver siRNAs, targeted to both the ABC transporter (ABCG2) and the anti-apoptosis defense gene (BCL2), and doxorubicin (DOX) to CSCs. The rationale is to sensitize CSCs to DOX by down regulating the drug-resistance gene ABCG2 and simultaneously induce apoptosis by lowering BCL2 expression. The co-delivery system (CDS) successfully delivered siRNAs and DOX to the cytoplasm and nuclei, respectively, and resulted in a down-regulation of ABCG2- and BCL2 mRNAs in CSCs by 60% and 65%, respectively, compared to the control. A corresponding decrease in protein expression was observed using Western blotting. The IC50 of DOX in CSCs concurrently decreased significantly. Our result established CDS as a promising multi-drug delivery platform for cancer treatment.

STATEMENT OF SIGNIFICANCE

Cancer stem cells (CSCs) are acknowledged to be responsible for increased resistance to chemo-drugs through a combination of increased expression of ABC transporters, an increased anti-apoptotic defense, and/or the ability for extensive DNA repair like normal stem cells. Consequently, effective therapy, especially to CSCs, is urgently required. In current study, we studied the characteristics of 231-CSCs sorted from human MDA-MB-231 breast cancer cells and found that 231-CSCs possessed enhanced proliferation, migration, tumorigenesis, and DOX resistance. We employed a non-ionic surfactant-based vesicle (niosome) delivery system to simultaneously deliver siRNAs targeted to multi-drug resistance genes, and DOX to kill 231-CSCs. The CDS showed an enhanced therapeutic effect by resensitizing 231-CSCs to DOX and may constitute a promising candidate for cancer chemotherapy.

A multifunctional peptide for targeted imaging and chemotherapy for nasopharyngeal and breast cancers

The L-peptide plays a role as a universal ligand binding specifically to nasopharyngeal carcinoma (NPC) and other cancers but not normal cells. It was used to link iron oxide nanoparticles, and injected intravenously to SCID mice bearing NPC and breast cancer xenografts for MR analysis, and showed significant change of MR signal intensity in the xenograft regions. Using this conjugate as a ligand to localize the L-peptide targeted protein in the cancer surgical specimens, a clear reaction product was identified in the tumor cells of both cancer types. If the L-peptide-linked-liposomal doxorubicin was used to treat the SCID mice bearing other NPC or breast cancer xenograft, a high efficacy of chemotherapy with minimal adverse effect was observed. In conclusion, the L-peptide has a considerable potential for clinical usage for targeted imaging, peptide histochemical localization of targeted protein, and targeted chemotherapy for different cancer types.

FROM THE CLINICAL EDITOR

Targeted chemotherapy to cancer cells will enable maximum drug delivery but minimal systemic side effects. In this article, the authors identified a protein, L-peptide, on tumor cells. They also subsequently confirmed the specificity of this protein in animal experiments using iron oxide nanoparticles. The discovery of this marker could lead to future development of better chemotherapy.

Prohibitin (PHB) inhibits apoptosis in rat granulosa cells (GCs) through the extracellular signal-regulated kinase 1/2 (ERK1/2) and the Bcl family of proteins

Mammalian ovarian follicular development is tightly regulated by crosstalk between cell death and survival signals, which include both endocrine and intra-ovarian regulators. Whether the follicle ultimately ovulates or undergoes atresia is dependent on the expression and actions of factors promoting follicular cell proliferation, differentiation or apoptosis. Prohibitin (PHB) is a highly conserved, ubiquitous protein that is abundantly expressed in granulosa cells (GCs) and associated with GC differentiation and apoptosis. The current study was designed to characterize the regulation of anti-apoptotic and pro-apoptotic factors in undifferentiated rat GCs (gonadotropin independent phase) governed by PHB. Microarray technology was initially employed to identify potential apoptosis-related genes, whose expression levels within GCs were altered by either staurosporine (STS) alone or STS in presence of ectopically over-expressed PHB. Next, immunoblot studies were performed to examine the expression patterns of selective Bcl-2 family members identified by the microarray analysis, which are commonly regulated in the intrinsic-apoptotic pathway. These studies were designed to measure protein levels of Bcl2 family in relation to expression of the acidic isoform (phosphorylated) PHB and the components of MEK-Erk1/2 pathway. These studies indicated that over-expression of PHB in undifferentiated GCs inhibit apoptosis which concomitantly results in an increased level of the anti-apoptotic proteins Bcl2 and Bclxl, reduced release of cytochrome c from mitochondria and inhibition of caspase-3 activity. In contrast, silencing of PHB expression resulted in change of mitochondrial morphology from the regular reticular network to a fragmented form, which enhanced sensitization of these GCs to the induction of apoptosis. Collectively, these studies have provided new insights on the PHB-mediated anti-apoptotic mechanism, which occurs in undifferentiated GCs through a PHB → Mek-Erk1/2 → Bcl/Bcl-xL pathway and may have important clinical implications.

Nanotechnology approaches for personalized treatment of multidrug resistant cancers

The efficacy of chemotherapy is substantially limited by the resistance of cancer cells to anticancer drugs that fluctuates significantly in different patients. Under identical chemotherapeutic protocols, some patients may receive relatively ineffective doses of anticancer agents while other individuals obtain excessive amounts of drugs that induce severe adverse side effects on healthy tissues. The current review is focused on an individualized selection of drugs and targets to suppress multidrug resistance. Such selection is based on the molecular characteristics of a tumor from an individual patient that can potentially improve the treatment outcome and bring us closer to an era of personalized medicine.

KHC-4 anti-cancer effects on human PC3 prostate cancer cell line

A bicyclic chemical structure, such as that found in flavonoids, was discovered to have anti-cancer activity. Further synthetic structural modification created a series of 2-phenyl-4-quinolone analogs, especially KHC-4, with the same bicyclic chemical structure. This new structure was reported to have stronger anti-cancer activity. In KHC-4 treatments for 72 h on human prostate cancer PC3 cells, cytotoxic effects (IC(50) =0.1 μM) increased dose dependently, causing Cdk1/cyclin B1 complex activity mannered cell cycle and proliferation. KHC-4 treatments suppressed Bcl-2 and Bcl-xL protein levels and upregulated Bax. At the same concentration, pro-caspase 9 protein was cleaved to an activated form, leading to cell apoptosis. Furthermore, the MMP-2 protein levels also decreased through KHC-4 treatment in PC3. In conclusion, KHC-4 presents great prostate cancer therapeutic effects for cell proliferation inhibition, induction of apoptosis and protection against tumor migration.

Two-in-one: combined targeted chemo and gene therapy for tumor suppression and prevention of metastases

Aims: To develop an approach for the effective treatment of ovarian tumor, prevention of metastases and limitation of side effects. Materials & Methods: In order to combine chemotherapy with genotherapy, we constructed a nanoscale-based tumor-targeted system containing two anticancer drugs, two antisense oligonucleotides (suppressors of cellular resistance) and a ligand specific to receptors overexpressed in cancer cells. The system was tested in a mouse metastatic xenograft model using tumor isolates from patients with ovarian carcinoma. Results: Treatment with the proposed nanosystem decreased primary tumor, prevented intraperitoneal metastases and limited adverse side effects. Conclusions: The advantages of the proposed targeted complex treatment of primary aggressive ovarian tumor and prevention of metastases make the proposed approach promising for clinical applications.

Chemotherapy dosing schedule influences drug resistance development in ovarian cancer

Drug resistance leads to chemotherapy failure and is responsible for the death of a great majority of patients with metastatic, late-stage ovarian cancer. The present study addressed whether changes in the chemotherapy dosing schedule affect the development, further worsening, or circumvention of drug resistance in chemosensitive and chemoresistant ovarian cancer. Severe combined immunodeficient mice bearing HeyA8 and HeyA8-MDR xenografts were treated with docetaxel intermittently (1×/wk or 3×/wk) or continuously for 21 days. Tumor mRNA expression of genes implicated in docetaxel resistance was measured by quantitative real-time-PCR. Analyzed genes included those encoding for the drug efflux transporters mdr1 and mrp7 and for molecules that interfere with or overcome the effects of docetaxel, including β-tubulinIII, actinin4, stathmin1, bcl2, rpn2, thoredoxin, and akt2. In both models, continuous docetaxel resulted in greater antitumor efficacy than 1×/wk or 3×/wk dosing and did not induce upregulation of any analyzed genes. Once weekly dosing caused upregulation of various drug resistance-related genes, especially in chemoresistant xenografts. More frequent, 3×/wk dosing diminished this effect, although levels of various genes were higher than for continuous chemotherapy. Drug efflux transporter expression was further examined by Western blotting, confirming that intermittent, but not continuous, docetaxel induced significant upregulation. Overall, our results show that the presence and length of treatment-free intervals contribute to the development of drug resistance. Elimination of these intervals by continuous dosing resulted in superior antitumor efficacy and prevented drug resistance induction in chemosensitive and chemoresistant disease. These results encourage the clinical implementation of continuous chemotherapy to overcome and/or prevent drug resistance in newly diagnosed and recurrent, refractory ovarian cancer.

Multifunctional tumor-targeted polymer-peptide-drug delivery system for treatment of primary and metastatic cancers

PURPOSE

In order to improve drug delivery to drug-resistant ovarian tumors, we constructed a multifunctional polymer-peptide-drug conjugate (PPDC) system for effective treatment of primary and metastatic ovarian cancers.

METHODS

The PPDC consists of the poly(Ethylene Glycol) (PEG) polymeric carrier conjugated via citric acid spacers to anticancer drug (Camptothecin, CPT), tumor targeting moiety (LRHR, a synthetic analog of luteinizing hormone-releasing hormone) and a suppressor of cellular antiapoptotic defense (BH3 peptide). To test the conjugates in vitro and in vivo, cancer cells were isolated from tissue samples obtained from patients with ovarian primary tumor and metastatic malignant ascites.

RESULTS

It was found that cells isolated from malignant ascites were more aggressive in terms of tumor growth and more resistant to chemotherapy when compared with those isolated from primary tumors. PPDC containing two copies of drugs and peptides was most efficient in treatment of primary tumors and intraperitoneal metastases. Multiple treatments with this PPDC led to almost complete regression of primary tumor and prevented growth of malignant ascites.

CONCLUSION

The proposed multifunctional polymeric delivery system which consists of multiple copies of the drug and peptides demonstrated significantly higher antitumor activity in primary and metastatic cancers when compared with drug alone and PEG-CPT conjugate.

Inhibition of lung tumor growth by complex pulmonary delivery of drugs with oligonucleotides as suppressors of cellular resistance

Development of cancer cell resistance, low accumulation of therapeutic drug in the lungs, and severe adverse treatment side effects represent main obstacles to efficient chemotherapy of lung cancer. To overcome these difficulties, we propose inhalation local delivery of anticancer drugs in combination with suppressors of pump and nonpump cellular resistance. To test this approach, nanoscale-based delivery systems containing doxorubicin as a cell death inducer, antisense oligonucleotides targeted to MRP1 mRNA as a suppressor of pump resistance and to BCL2 mRNA as a suppressor of nonpump resistance, were developed and examined on an orthotopic murine model of human lung carcinoma. The experimental results show high antitumor activity and low adverse side effects of proposed complex inhalatory treatment that cannot be achieved by individual components applied separately. The present work potentially contributes to the treatment of lung cancer by describing a unique combinatorial local inhalation delivery of drugs and suppressors of pump and nonpump cellular resistance.

Therapeutic peptides for cancer therapy. Part II - cell cycle inhibitory peptides and apoptosis-inducing peptides

BACKGROUND

Therapeutic peptides have great potential as anticancer agents owing to their ease of rational design and target specificity. However, their utility in vivo is limited by low stability and poor tumor penetration.

OBJECTIVE

The authors review the development of peptide inhibitors with potential for cancer therapy. Peptides that arrest the cell cycle by mimicking CDK inhibitors or induce apoptosis directly are discussed.

METHODS

The authors searched Medline for articles concerning the development of therapeutic peptides and their delivery.

RESULTS/CONCLUSION

Inhibition of cancer cell proliferation directly using peptides that arrest the cell cycle or induce apoptosis is a promising strategy. Peptides can be designed that interact very specifically with cyclins and/or cyclin-dependent kinases and with members of apoptotic cascades. Use of these peptides is not limited by their design, as a rational approach to peptide design is much less challenging than the design of small molecule inhibitors of specific protein-protein interactions. However, the limitations of peptide therapy lie in the poor pharmacokinetic properties of these large, often charged molecules. Therefore, overcoming the drug delivery hurdles could open the door for effective peptide therapy, thus making an entirely new class of molecules useful as anticancer drugs.

Cytotoxic pentacyclic triterpenoids from Combretum sundaicum and Lantana camara as inhibitors of Bcl-xL/BakBH3 domain peptide interaction

In an effort to discover potent inhibitors of the antiapoptotic protein Bcl-xL, a systematic in vitro evaluation was undertaken on extracts prepared from various parts of Vietnamese plants. The ethyl acetate extracts obtained from the leaves and flowers of Combretum sundaicum and the leaves of Lantana camara were selected for their interaction with the Bcl-xL/Bak association. Bioassay-guided purification of these species led to the isolation of 15 pentacyclic triterpenoids (1-15) possessing olean-12-en-28-oic acid and olean-12-en-29-oic acid aglycons, of which compounds 1-6 and 8-10 are new. Five compounds exhibited binding activity with K(i) values between 5.3 and 17.8 microM. The cytotoxic activity of 1-15 was also evaluated on various cancer cell lines.

Co-delivery of siRNA and an anticancer drug for treatment of multidrug-resistant cancer

AIMS

To develop a novel nanomedicine approach for the treatment of multidrug-resistant (MDR) cancer by combining an anticancer drug and suppressors of cellular resistance within one multifunctional nanocarrier-based delivery system (NDS).

MATERIALS & METHODS

The NDS consisted of cationic liposomes (carrier, 100-140 nm), doxorubicin (DOX, anticancer drug), siRNA targeted to MRP1 and BCL2 mRNA (suppressors of pump and nonpump cellular-resistance, respectively). The resulting approximately 500 nm complex has a zeta potential of +4 mV.

RESULTS & DISCUSSION

The NDS provides an effective co-delivery of DOX and siRNA as well as cell-death induction and suppression of cellular resistance in MDR lung cancer cells.

CONCLUSION

We demonstrate NDS-enhanced efficiency of chemotherapy to a level that cannot be achieved by applying its components separately.

Targeted therapies in gynecologic cancers and melanoma

The article reviews the main molecular pathology alterations of endometrial and ovarian carcinomas and melanoma. Several promising drugs targeting the genes most frequently altered in these tumors are under consideration. The most promising signaling pathways to be targeted for therapies in these tumors are the tyrosine kinase receptor (EGFR, HER2, c-KIT), the RAS/B-RAF/MAPK, the PI3K-mTOR, and apoptosis signaling pathways.

Antitumor activity of new liposomal prodrug of mitomycin C in multidrug resistant solid tumor: Insights of the mechanism of action

The antitumor activity of a novel thiolytically cleavable lipid-based prodrug of mitomycin C (MMC) delivered by STEALTH liposomes (SL) was studied in drug resistant human ovarian carcinoma A2780/AD model and compared with free MMC and both free and SL forms of an established anticancer drug--doxorubicin (DOX). It was found that SL-prodrug (SL-pMMC) possessed enhanced antitumor activity when compared with the parent MMC, free DOX, and SL-DOX. An observance of the high antitumor efficiency of SL-pMMC was a result of its preferential accumulation in the tumor by the enhanced permeability and retention (EPR) effect, suppression of multidrug resistance (MDR) associated with P-glycoprotein and MRP drug efflux pumps, activation of caspase-dependent apoptosis signaling pathways and suppression of antiapoptotic cellular defense by increasing the BAX/BCL2 ratio. Consequently, the described SL-pMMC formulations can be considered good candidates for the chemotherapy of multidrug resistant tumors.

Nonviral nanoscale-based delivery of antisense oligonucleotides targeted to hypoxia-inducible factor 1 alpha enhances the efficacy of chemotherapy in drug-resistant tumor

PURPOSE

To enhance the efficacy of cancer treatment, we propose a complex approach: simultaneous delivery to the tumor of a chemotherapeutic agent and a suppressor of hypoxia-inducible factor 1 alpha (HIF1A).

EXPERIMENTAL DESIGN

The novel complex liposomal drug delivery system was developed and evaluated in vitro and in vivo on nude mice bearing xenografts of multidrug-resistant human ovarian carcinoma. The proposed novel complex drug delivery system consists of liposomes as a nanocarrier, a traditional anticancer drug (doxorubicin) as a cell death inducer, and antisense oligonucleotides targeted to HIF1A mRNA as a suppressor of cellular resistance and angiogenesis.

RESULTS

The system effectively delivers active ingredients into tumor cells, multiplies the cell death signal initiated by doxorubicin, and inhibits cellular defensive mechanisms and angiogenesis by down-regulating BCL2, HSP90, and vascular endothelial growth factor proteins. This, in turn, activates caspases, promotes apoptosis, necrosis, and tumor shrinkage. The proposed novel complex multipronged approach enhances the efficiency of chemotherapy.

CONCLUSIONS

The proposed combination therapy prevents the development of resistance in cancer cells, and thus, increases the efficacy of chemotherapy to an extent that cannot be achieved by individual components applied separately. It could form the foundation for a novel type of cancer therapy based on simultaneous delivery of an anticancer drug and a suppressor of HIF1A.

Releasable PEGylation of proteins with customized linkers

Releasable PEGylation employs customized linkers that reversibly tether a therapeutic moiety with polyethylene glycol polymers. The choice of releasable PEG linkers may have numerous applications that are insufficiently addressed by stable polymer attachment. Releasable PEGylation provides regeneration of authentic and fully active drug and allows tailored design of critical pharmacological parameters such as the maximal drug concentration and total drug exposure. This provides a prodrug format that combines beneficial attributes of PEGylation with controlled release. The linker release mechanisms are shown to be kinetically controlled by the design of a hydrolytically labile center and side chains for the steric modulation of the intramolecular elimination reactions and linker self-immolation. Recent reports have described both aromatic and aliphatic based customized linkers that release the unaltered original drug under physiological conditions and at therapeutically useful release rates. These studies have examined bioconjugates of cytokines, peptide hormones, immunotoxins, enzymes, and reporter proteins.

Targeted Proapoptotic Anticancer Drug Delivery System

A novel targeted proapoptotic anticancer drug delivery system (DDS) was developed and evaluated both in vitro and in vivo. The system contains poly(ethylene glycol) polymer (PEG) as a carrier, camptothecin (CPT) as an anticancer drug/cell death inducer, a synthetic analogue of luteinizing hormone-releasing hormone (LHRH) peptide as a targeting moiety/penetration enhancer, and a synthetic analogue of BCL2 homology 3 domain (BH3) peptide as a suppressor of cellular antiapoptotic defense. The design of the multicomponent DDS allowed for a conjugation of one or two copies of each active ingredient (CPT, LHRH, and BH3) to one molecule of PEG carrier. The complex structure of the PEG conjugates was visualized at nanometer resolution using atomic force microscopy. We found that the ligand-targeted DDS for cancer cells preferentially accumulated in the tumor and allowed the delivery of active ingredients into the cellular cytoplasm and nuclei of cancer cells. Simultaneous apoptosis induction through the caspase-dependent signaling pathway and inhibition of cellular antiapoptotic defense by the suppression of BCL2 protein enhanced cytotoxicity and antitumor activity of the entire DDS to a level which could not be achieved by individual components applied separately. The DDS containing two copies of each active component (CPT, LHRH, and BH3) per molecule of PEG polymer had the highest anticancer efficiency in vitro and in vivo.

Targeted Sialic Acid–Doxorubicin Prodrugs for Intracellular Delivery and Cancer Treatment

PURPOSE

To evaluate a novel targeted anticancer prodrug consisting of several copies of sialic acid (SA, targeting moiety), doxorubicin (DOX), citric acid (multifunctional spacer) and poly(ethylene glycol) (PEG, carrier).

METHODS

alpha, omega bis carboxyl PEG was covalently conjugated with multiple copies of SA and DOX through a citric acid spacer and characterized by proton nuclear magnetic resonance ((1)HNMR), matrix-assisted laser desorption/ionization-time of flight (MALDI/TOF), and high-performance liquid chromatography (HPLC). The molecular models of conjugates were established using ChemDraw software. Stability, spontaneous and esterase-stimulated drug release was analyzed by HPLC. Cellular internalization (fluorescence microscopy) and cytotoxicity [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay] of free DOX and prodrugs were evaluated.

RESULTS

(1)HNMR, MALDI/TOF, and HPLC showed the formation of the PEG prodrug conjugates. More than 40% of the drug was released from its conjugate in the presence of esterase enzyme, whereas the conjugate was stable at pH 7.4 in the absence of enzyme. Molecular modeling studies showed stable conformations of conjugates. The targeted prodrug conjugates with two copies of SA and DOX showed enhanced cytotoxicity when compared with non-targeted prodrugs and free DOX.

CONCLUSIONS

Targeting of the conjugate to cancer cells by SA with increased copies of targeting moiety and anticancer drug enhanced prodrug uptake by cancer cells and cytotoxicity of the prodrug.

(α/β+α)-Peptide Antagonists of BH3 Domain/Bcl-xL Recognition: Toward General Strategies for Foldamer-Based Inhibition of Protein−Protein Interactions

The development of molecules that bind to specific protein surface sites and inhibit protein-protein interactions is a fundamental challenge in molecular recognition. New strategies for approaching this challenge could have important long-term ramifications in biology and medicine. We are exploring the concept that unnatural oligomers with well-defined conformations ("foldamers") can mimic protein secondary structural elements and thereby block specific protein-protein interactions. Here, we describe the identification and analysis of helical peptide-based foldamers that bind to a specific cleft on the anti-apoptotic protein Bcl-xL by mimicking an alpha-helical BH3 domain. Initial studies, employing a fluorescence polarization (FP) competition assay, revealed that among several alpha/beta- and beta-peptide foldamer backbones only alpha/beta-peptides intended to adopt 14/15-helical secondary structure display significant binding to Bcl-xL. The most tightly binding Bcl-xL ligands are chimeric oligomers in which an N-terminal alpha/beta-peptide segment is fused to a C-terminal alpha-peptide segment ((alpha/beta + alpha)-peptides)). Sequence-affinity relationships were probed via standard and nonstandard techniques (alanine scanning and hydrophile scanning, respectively), and the results allowed us to construct a computational model of the ligand/Bcl-xL complex. Analytical ultracentrifugation with a high-affinity (alpha/beta + alpha)-peptide established 1:1 ligand:Bcl-xL stoichiometry under FP assay conditions. Binding selectivity studies with the most potent (alpha/beta + alpha)-peptide, conducted via surface plasmon resonance measurements, revealed that this ligand binds tightly to Bcl-w as well as to Bcl-xL, while binding to Bcl-2 is somewhat weaker. No binding could be detected with Mcl-1. We show that our most potent (alpha/beta + alpha)-peptide can induce cytochrome C release from mitochondria, an early step in apoptosis, in cell lysates, and that this activity is dependent upon inhibition of protein-protein interactions involving Bcl-xL.

In vitro and in vivo intracellular liposomal delivery of antisense oligonucleotides and anticancer drug

The specific aims of this investigation were (1) to show that conventional and PEGylated liposomes can penetrate cancer cells in vitro and in vivo; (2) to demonstrate that liposomes can be successfully used both for cytoplasmic and nuclear delivery of therapeutics, including anticancer drugs and antisense oligonucleotides; (3) to examine the specific activity of anticancer drugs and nucleotides delivered inside tumor cells by PEGylated liposomes; and (4) to confirm that simultaneous inhibition of pump and nonpump cellular resistance by liposomal ASO can substantially enhance the antitumor activity of traditional well established anticancer drugs in mice bearing xenografts of human multidrug resistant ovarian carcinoma. Experimental results show that PEGylated liposomes are capable of penetrating directly into tumor cells after systemic administration in vivo and do successfully provide cytoplasmic and nuclear delivery of encapsulated anticancer drug (doxorubicin, DOX) and antisense oligonucleotides (ASO). Encapsulation of DOX and ASO into liposomes substantially increased their specific activity. Simultaneous suppression of pump and nonpump resistance dramatically enhanced the ability of DOX for inducing apoptosis leading to higher in vitro cytotoxicity and in vivo antitumor activity.