Abstract LB-172: Transgene presence in patients’ tumors following tumor-targeted nanodelivery

Discussant: William F. Benedict, UT M. D. Anderson Center, Houston, TX.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-172.

Physical characterization methods for iron oxide contrast agents encapsulated within a targeted liposome-based delivery system

Intact liposome-based targeted nanoparticle delivery systems (NDS) are immobilized by non-selective binding and characterized by scanning probe microscopy (SPM) in a fluid imaging environment. The size, size distribution, functionality, and stability of an NDS with a payload consisting of a super-paramagnetic iron oxide contrast agent for magnetic resonance imaging are determined. SPM results are combined with information obtained by more familiar techniques such as superconducting quantum interference device (SQUID) magnetometry, dynamic light scattering, and electron microscopy. By integrating the methods presented in this work into the NDS formulation and manufacturing process, size-dependent statistical properties of the complex can be obtained and the structure-function relationship of individual, multi-component nanoscale entities can be assessed in a reliable and reproducible manner.

Tumor-targeting nanocomplex delivery of novel tumor suppressor RB94 chemosensitizes bladder carcinoma cells in vitro and in vivo

PURPOSE

RB94, a truncated form of RB110, has enhanced tumor suppressor potency and activity against all tumor types tested to date including bladder carcinoma. However, efficient, systemic delivery of the gene encoding RB94 specifically to tumors, is an obstacle to clinical application as an anticancer therapeutic. We have developed a systemically given, nanosized liposome DNA delivery system that specifically targets primary and metastatic disease. The ability of RB94, delivered via this nanocomplex, to sensitize bladder carcinoma to chemotherapy in vitro and in vivo was assessed.

EXPERIMENTAL DESIGN

The nanocomplex is an RB94 plasmid encapsulated by a cationic liposome, the surface of which is decorated with a tumor-targeting moiety, either transferrin (Tf/Lip/RB94) or an antitransferrin receptor single-chain antibody fragment (TfRScFv/Lip/RB94). The ability of the complex to sensitize human bladder carcinoma HTB-9 cells to chemotherapeutics was assessed in vitro by XTT assay. In vivo tumor specificity and efficacy were tested in mice carrying HTB-9 tumors by PCR and tumor growth inhibition, respectively.

RESULTS

Transfection with Tf/Lip/RB94 significantly sensitized HTB-9 cells to chemotherapeutic agents in vitro. Tumor specificity of the complex was shown in an orthotopic bladder tumor model by immunohistochemistry and PCR. Moreover, in mice bearing subcutaneous HTB-9 tumors, the combination of systemically given Tf/Lip/RB94 or TfRScFv/Lip/RB94 plus gemcitabine resulted in significant (P<0.0005) tumor growth inhibition/regression and induction of apoptosis.

CONCLUSIONS

Use of our tumor-targeting nanocomplex to specifically deliver the potent tumor suppressor RB94 efficiently to tumors has potential as a more effective treatment modality for genitourinary and other cancers.

Tumor-targeting nanodelivery enhances the anticancer activity of a novel quinazolinone analogue

GMC-5-193 (GMC) is a novel anticancer small-molecule quinazolinone analogue with properties that include antimicrotubule activity and inherent fluorescence. The aim of this study was to produce and optimize a systemically administered liposomal formulation for tumor-targeting delivery of GMC to enhance the anticancer effect of this compound and evaluate its bioefficacy. GMC was encapsulated within a cationic liposome, which was decorated on the surface with an anti-transferrin receptor single-chain antibody fragment (TfRscFv) as the tumor-targeting moiety to form a nanoscale complex (scL/GMC). Confocal imaging of fluorescent GMC uptake in a human melanoma cell line, MDA-MB-435, showed higher cellular uptake of GMC when delivered via the liposome complex compared with free GMC. Delivery of GMC by the tumor-targeting liposome nanoimmunocomplex also resulted in a 3- to 4-fold decrease in IC(50) values in human cancer cells [DU145 (prostate) and MDA-MB-435] compared with the effects of GMC administered as free GMC. In addition, the GMC nanoimmunocomplex increased the sensitivity of cancer cells to doxorubicin, docetaxel, or mitoxantrone by approximately 3- to 30-fold. In the MDA435/LCC6 athymic nude mice xenograft lung metastases model, GMC was specifically delivered to tumors by the nanoimmunocomplex. These data show that incorporation of small-molecule therapeutic GMC within the tumor-targeting liposome nanocomplex enhances its anticancer effect.

Materializing the potential of small interfering RNA via a tumor-targeting nanodelivery system

The field of small interfering RNA (siRNA) as potent sequence-selective inhibitors of transcription is rapidly developing. However, until now, low transfection efficiency, poor tissue penetration, and nonspecific immune stimulation by in vivo administered siRNAs have delayed their therapeutic application. Their potential as anticancer therapeutics hinges on the availability of a vehicle that can be systemically administered, safely and repeatedly, and will deliver the siRNA specifically and efficiently to the tumor, both primary tumors and metastases. We have developed a nanosized immunoliposome-based delivery complex (scL) that, when systemically administered, will preferentially target and deliver molecules useful in gene medicine, including plasmid DNA and antisense oligonucleotides, to tumor cells wherever they occur in the body. This tumor-targeting nanoparticle delivery vehicle can also deliver siRNA to both primary and metastatic disease. We have also enhanced the efficiency of this complex by the inclusion of a pH-sensitive histidine-lysine peptide in the complex (scL-HoKC) and by delivery of a modified hybrid (DNA-RNA) anti-HER-2 siRNA molecule. Scanning probe microscopy confirms that this modified complex maintains its nanoscale size. More importantly, we show that this nanoimmunoliposome anti-HER-2 siRNA complex can sensitize human tumor cells to chemotherapeutics, silence the target gene and affect its downstream pathway components in vivo, and significantly inhibit tumor growth in a pancreatic cancer model. Thus, this complex has the potential to help translate the potent effects of siRNA into a clinically viable anticancer therapeutic.

Chemically modified short interfering hybrids (siHYBRIDS): nanoimmunoliposome delivery in vitro and in vivo for RNAi of HER-2

A blunt-ended 19-mer short interfering hybrid (siHybrid) (H) comprised of sense-DNA/antisense-RNA targeting HER-2 mRNA was encapsulated in a liposomal nanoplex with anti-transferrin receptor single-chain antibody fragment (TfRscFv) as the targeting moiety for clinically relevant tumor-specific delivery. In vitro delivery to a human pancreatic cell line (PANC-1) was shown to exhibit sequence-specific inhibition of 48-h cell growth with an IC50 value of 37 nM. The inhibitory potency of this siHybrid was increased (IC50 value of 7.8 nM) using a homologous chemically modified siHybrid (mH) in which the 19-mer sense strand had the following pattern of 2 '-deoxyinosine (dI) and 2 '-O-methylribonucleotide (2 '-OMe) residues: 5'-d(TITIT)-2'OMe(GCGGUGGUU)-d(GICIT). These modifications were intended to favor antisense strand-mediated RNAi while mitigating possible sense strand-mediated off-target effects and RNase H-mediated cleavage of the antisense RNA strand. The presently reported immunoliposomal delivery system was successfully used in vivo to inhibit HER-2 expression, and thus induce apoptosis in human breast carcinoma tumors (MDA-MB-435) in mice upon repeated i.v. treatment at a dose of 3 mg/kg of H or mH. The in vivo potency of modified siHybrid mH appeared to be qualitatively greater than that of H, as was the case in vitro.

Tumor-Targeting Nanoimmunoliposome Complex for Short Interfering RNA Delivery

The potential of short interfering RNA (siRNA) to be developed for therapeutic use against cancer depends on the availability of an efficient tumor-specific delivery vehicle. We have previously shown that a nanoscale nonviral liposome-based complex that includes an anti-transferrin receptor single-chain antibody fragment as the targeting moiety can, when systemically administered, specifically and efficiently target primary and metastatic tumors and deliver molecules useful in gene medicine, including plasmid DNA and antisense oligonucleotides. Here we explore the ability of this complex to deliver a fluorescein-labeled siRNA to tumor cells in vivo and examine the intracellular localization in vitro by confocal microscopy. We show that the immunoliposome--siRNA complex maintains its nanoscale size and, using three separate tumor models, can efficiently and specifically deliver siRNA to both primary and metastatic disease after systemic delivery, thus increasing the possibility for translating the potent effects of siRNA observed in vitro into clinically useful therapeutics.

A tumor-targeted nanodelivery system to improve early MRI detection of cancer

The development of improvements in magnetic resonance imaging (MRI) that would enhance sensitivity, leading to earlier detection of cancer and visualization of metastatic disease, is an area of intense exploration. We have devised a tumor-targeting, liposomal nanodelivery platform for use in gene medicine. This systemically administered nanocomplex has been shown to specifically and efficiently deliver both genes and oligonucleotides to primary and metastatic tumor cells, resulting in significant tumor growth inhibition and even tumor regression. Here we examine the effect on MRI of incorporating conventional MRI contrast agent Magnevist into our anti-transferrin receptor single-chain antibody (TfRscFv) liposomal complex. Both in vitro and in an in vivo orthotopic mouse model of pancreatic cancer, we show increased resolution and image intensity with the complexed Magnevist. Using advanced microscopy techniques (scanning electron microscopy and scanning probe microscopy), we also established that the Magnevist is in fact encapsulated by the liposome in the complex and that the complex still retains its nanodimensional size. These results demonstrate that this TfRscFv-liposome-Magnevist nanocomplex has the potential to become a useful tool in early cancer detection.

Antisense oligonucleotides targeted to the human alpha folate receptor inhibit breast cancer cell growth and sensitize the cells to doxorubicin treatment

Folates are essential for cell survival and are required for numerous biochemical processes. The human alpha isoform folate receptor (alphahFR) has a very high affinity for folic acid and is considered an essential component in the cellular accumulation of folates and folate analogues used in chemotherapy. The expression of alphahFR is not detected inmost normal tissues. In contrast, high levels of the expression of alphahFR have been reported in a variety of cancer cells. The significance of alphahFR overexpression in malignant tissues has not been elucidated, but it is possible that it promotes cell proliferation not only by mediating folate uptake but also by generating other regulatory signals. The purpose of the present study was to evaluate alphahFR as a potential target for the treatment of breast cancer. Initial studies were done in nasopharyngeal carcinoma (KB) cells, which express high levels of alphahFR. In KB cells, antisense oligodeoxyribonucleotides (ODN) complementary to the alphahFR gene sequences were found to reduce newly synthesized alphahFR protein up to 60%. To examine the effect of alphahFR antisense ODNs in a panel of cultured human breast cancer cell lines, we used a tumor cell-targeted, transferrin-liposome-mediated delivery system. The data show that alphahFR antisense ODNs induced a dose-dependent decrease in cell survival. Finally, we determined that alphahFR antisense ODNs sensitized MDA-MB-435 breast cancer cells by 5-fold to treatment with doxorubicin. The data support the application of alphahFR antisense ODNs as a potential anticancer agent in combination with doxorubicin.

Antisense oligonucleotides targeted to the human α folate receptor inhibit breast cancer cell growth and sensitize the cells to doxorubicin treatment

Folates are essential for cell survival and are required for numerous biochemical processes. The human α isoform folate receptor (αhFR) has a very high affinity for folic acid and is considered an essential component in the cellular accumulation of folates and folate analogues used in chemotherapy. The expression of αhFR is not detected inmost normal tissues. In contrast, high levels of the expression of αhFR have been reported in a variety of cancer cells. The significance of αhFR overexpression in malignant tissues has not been elucidated, but it is possible that it promotes cell proliferation not only by mediating folate uptake but also by generating other regulatory signals. The purpose of the present study was to evaluate αhFR as a potential target for the treatment of breast cancer. Initial studies were done in nasopharyngeal carcinoma (KB) cells, which express high levels of αhFR. In KB cells, antisense oligodeoxyribonucleotides (ODN) complementary to the αhFR gene sequences were found to reduce newly synthesized αhFR protein up to 60%. To examine the effect of αhFR antisense ODNs in a panel of cultured human breast cancer cell lines, we used a tumor cell–targeted, transferrin-liposome–mediated delivery system. The data show that αhFR antisense ODNs induced a dose-dependent decrease in cell survival. Finally, we determined that αhFR antisense ODNs sensitized MDA-MB-435 breast cancer cells by 5-fold to treatment with doxorubicin. The data support the application of αhFR antisense ODNs as a potential anticancer agent in combination with doxorubicin.

A sterically stabilized immunolipoplex for systemic administration of a therapeutic gene

A sterically stabilized immunolipoplex (TsPLP), containing an antitransferrin receptor single-chain antibody fragment (TfRscFv)-PEG molecule, has been developed to specifically and efficiently deliver a therapeutic gene to tumor cells. A postcoating preparation strategy was employed in which a DNA/lipid complex (lipoplex) was formed first and then sequentially conjugated with PEG and TfRscFv. The complex prepared by this method was shown to be superior in ability to deliver genes to tumor cells than when prepared by a common precoating strategy, in which DNA is mixed with TfRscFv-PEG conjugated liposome. Using prostate cancer cell line DU145, a comparison was made between the in vitro and in vivo gene delivery efficiencies of four complexes, Lipoplex (LP), PEG-Lipoplex (PLP), TfRscFv-PEG-Lipoplex (TsPLP) and our standard TfRscFv-Lipoplex (TsLP). In vitro, the order of transfection efficiency was TsLP>LP approximately TsPLP>PLP. However, in vivo the order of transfection efficiency, after systemic administration via the tail vein, was TsPLP>TsLP>LP or PLP with TsPLP-mediated exogenous gene expression in tumor being two-fold higher than when mediated by TsLP. This suggests that the in vitro transfection efficiency of TsPLP was not indicative of its in vivo efficiency. In addition, it was found that the level of exogenous gene expression in the tumor mediated by TsPLP was higher than that mediated by TsLP and did not decrease over the time. More importantly, high exogenous gene expression in tumor, but low expression in liver, was observed after an i.v. delivery of TsPLP carrying either the GFP reporter gene or the p53 gene, indicating that tumor preferential targeting was maintained by this complex in the presence of PEG. These findings show that incorporation of PEG into our targeted lipoplex results in a more efficient delivery of the complex to the tumor cells, possibly by inhibiting the first pass clearance observed with non-PEG containing liposomes. Therefore, these data demonstrate that TsPLP is a improvement over our previously established tumor targeted gene delivery complex for systemic gene therapy of cancer.

HER-2-targeted antisense oligonucleotide results in sensitization of head and neck cancer cells to chemotherapeutic agents

Existing HER-2 targeted therapies for human head and neck cancers, usually administered in combination with chemotherapeutic drugs or irradiation, include monoclonal antibodies to HER-2, receptor tyrosine kinase inhibitors and HER-2 specific immunotoxins. Instead of targeting the existing protein, interference with HER-2 mRNA translation by antisense oligonucleotides may be a more efficient method to downregulate levels of HER-2 protein for combination therapy. To test this hypothesis we have used a phosphorothioate pentadecamer, complementary to the HER-2 mRNA initiation codon region (AS HER-2 ODN), to increase sensitivity to four chemotherapeutic agents in human head and neck cancer cell lines, all of which express low levels of the HER-2 protein. To improve delivery into tumor cells, the AS HER-2 ODN was complexed with our previously established folate-liposome delivery system. Cell survival assays and Western blot analysis data demonstrated that folate-liposome mediated AS HER-2 oligonucleotide treatment inhibited cell growth and HER-2 expression, and induced apoptosis in SCC-25CP cells. Moreover, there was a synergistic effect on the percent of apoptotic cells. Additionally, the combination of folate-liposome-AS HER-2 ODN and CDDP had a synergistic effect on the induction of apoptosis. Using confocal microscopy, FITC labeled ODN (FITC-ODN) in complex with folate-liganded, rhodamine (Rh) labeled, cationic liposomes was observed to enter SCC-25CP head and neck tumor cells within 3 to 6 h. Intracellularly, the FITC-ODN separated from the Rh-folate-liposomes, and FITC-ODN accumulated in the nucleus while Rh-liposomes remained in punctate cytoplasmic structures. Thus, folate-liposome-mediated delivery of AS HER-2 ODN has potential as a new means of increasing the responsiveness of head and neck cancer to conventional chemotherapy.

Enhanced transfection efficiency of a systemically delivered tumor-targeting immunolipoplex by inclusion of a pH-sensitive histidylated oligolysine peptide

Successful cancer gene therapy depends on the development of non-toxic, efficient, tumor cell- specific systemic gene delivery systems. Our laboratory has developed a systemically administered, ligand-liposome complex that can effectively and preferentially deliver its therapeutic payload to both primary and metastatic tumors. To further improve the transfection efficiency of this targeting complex, a synthetic pH-sensitive histidylated oligolysine K[K(H)KKK]5-K(H)KKC (HoKC), designed to aid in endosomal escape and condensation of DNA, was included in the complex. The presence of HoKC increased the in vitro transfection efficiency over that of the original complex. Moreover, no increase in cytotoxicity was observed due to the presence of the HoKC peptide. In a DU145 human prostate cancer xenograft tumor model in athymic nude mice, inclusion of the HoKC peptide did not interfere with the tumor targeting specificity of the i.v. administered ligand/liposome/DNA complex. Most importantly, the level of transgene expression was significantly elevated in the tumors, but not in the normal tissue in those animals receiving the complex incorporating HoKC. The in vivo enhancement of transfection efficiency by this modified gene delivery vehicle could lead to a reduction in the number of administrations required for antitumor efficacy.

Antisense therapeutics: from theory to clinical practice

The use of antisense (AS) oligonucleotides as therapeutic agents was proposed as far back as the 1960s/1970s when the AS strategy was initially developed. However, it has taken almost a quarter of a century for this potential to be realized. The last few years has seen a rapid increase in the number of AS molecules progressing past Phase I in clinical trials, due in part to our increased knowledge of their structure and chemistry. Here, we describe the most prominent of these modifications with respect to clinical applicability. However, the main focus of this review is clinical application, with a focus on cancer. We will discuss in detail both the status of the current AS clinical trials and the molecules that are likely to be the targets of the next group of AS molecules entering the clinic.

Tumor-targeting, systemically delivered antisense HER-2 chemosensitizes human breast cancer xenografts irrespective of HER-2 levels

BACKGROUND

The failure to respond to chemotherapy is a major obstacle in the successful treatment of breast cancer. We have previously shown that anti-HER-2 antisense oligonucleotide (AS HER-2 ODN) treatment was able to sensitize breast cancer cells to various chemotherapeutic agents in vitro irrespective of their HER-2 status, indicating that the use of AS HER-2 ODN therapy for breast cancer is not limited to tumors overexpressing the protein. One of the main drawbacks to the use of antisense therapy in the clinical setting is the lack of an efficient, tumor-targeting, systemic delivery method. We have developed a tumor-specific, ligand-targeting, cationic liposome delivery system designed for systemic gene therapy of cancer. In this study we employ this ligand-liposome strategy to enhance the delivery of the AS Her-2 ODN to breast cancer cells, including those that do not overexpress HER-2, in vitro and in vivo.

MATERIALS AND METHODS

A cationic liposome complex that includes folate as the targeting ligand was designed and optimized for more efficient delivery of AS HER-2 ODN to breast tumors cells in vitro, and more significantly, for systemic delivery with tumor-specific targeting in vivo. Human breast cancer cell line MDA-MB-435, which does not overexpress HER-2, was used to compare the degree of chemosensitization to the taxanes of AS HER-2 ODN delivered via the optimized folate-liposome versuscommercial Lipofectin. MDA-MB-435 xenograft tumors were also used to evaluate the anti-tumor effect of the combination of systemically delivered folate-liposome-AS HER-2 ODN and docetaxel (Taxotere).

RESULTS

The optimized folate-liposome-AS HER-2 ODN complex significantly increases the response of breast tumor cell lines to conventional chemotherapeutic agents in vitro as compared to AS HER-2 delivered via an unliganded commercially available reagent, Lipofectin. In vivo, the folate-liposome-AS HER-2 ODN complex has prolonged stability in blood and increased uptake in tumors. More significantly, the combination of intravenously administered ligand-liposome-AS HER-2 ODN and docetaxel resulted in a marked inhibition of xenograft growth in an aggressive breast cancer model that does not overexpress HER-2, even after treatment ended.

CONCLUSIONS

Although there are other reports of liposomal delivery of AS ODNs, this is the first report of in vivo efficacy against human cancer cells using a tumor-targeting liposome delivery system for systemic AS therapy. Moreover, the increased stability in circulation and anti-tumor efficacy observed were obtained without the need for continuous intravenous infusion. HER-2 is an integral component within a network of cell growth pathways that can affect many different types of tumors where HER-2 may be a contributing factor, such as ovarian, esophageal, and GI malignancies including colon and pancreatic cancers. Therefore, the effectiveness of this therapy with xenograft tumors that do not overexpress HER-2 has the potential to expand the clinical usefulness of this efficacious form of therapy.

Systemic tumor-targeted gene delivery by anti-transferrin receptor scFv-immunoliposomes

An ideal therapeutic for cancer would be one that selectively targets to tumor cells, is nontoxic to normal cells, and that could be systemically delivered, thereby reaching metastases as well as primary tumor. Immunoliposomes directed by monoclonal antibody or its fragments are promising vehicles for tumor-targeted drug delivery. However, there is currently very limited data on gene delivery using these vehicles. We have recently described a cationic immunoliposome system directed by a lipid-tagged, single-chain antibody Fv fragment (scFv) against the human transferrin receptor (TfR) that shows promising efficacy for systemic p53 tumor suppressor gene therapy in a human breast cancer metastasis model. However, the extremely low yield of this lipid-tagged scFv limited further downstream development and studies. Here we report a different expression strategy for the anti-TfR scFv, which produces high levels of protein without any tags, and a different approach for complexing the targeting scFv to the liposomes. This approach entails covalently conjugating the scFv to the liposome via a cysteine at the 3'-end of the protein and a maleimide group on the liposome. Our results show that this conjugation does not impair the immunological activity or targeting ability of the scFv. The scFv-cys targets the cationic liposome-DNA complex (lipoplex) to tumor cells and enhances the transfection efficiencies both in vitro and in vivo in a variety of human tumor models. This scFv-immunoliposome can deliver the complexed gene systemically to tumors in vivo, where it is efficiently expressed. In comparison with the whole antibody or transferrin molecule itself, the scFv has a much smaller size for better penetration into solid tumors. It is also a recombinant protein rather than a blood product; thus, large scale production and strict quality control are feasible. This new approach provides a promising system for tumor-targeted gene delivery that may have potential for systemic gene therapy of various human cancers.

Self-assembly of a virus-mimicking nanostructure system for efficient tumor-targeted gene delivery

Molecular therapy, including gene therapy, is a promising strategy for the treatment of human disease. However, delivery of molecular therapeutics efficiently and specifically to the target tissue remains a significant challenge. A human transferrin (Tf)-targeted cationic liposome-DNA complex, Tf-lipoplex, has shown high gene transfer efficiency and efficacy with human head and neck cancer in vitro and in vivo (Xu, L., Pirollo, K.F., Tang, W.H., Rait, A., and Chang, E.H. Hum. Gene Ther. 1999;10:2941-2952). Here we explore the structure, size, formation process, and structure-function relationships of Tf-lipoplex. We have observed Tf-lipoplex to have a highly compact structure, with a relatively uniform size of 50-90 nm. This nanostructure is novel in that it resembles a virus particle with a dense core enveloped by a membrane coated with Tf molecules spiking the surface. More importantly, compared with unliganded lipoplex, Tf-lipoplex shows enhanced stability, improved in vivo gene transfer efficiency, and long-term efficacy for systemic p53 gene therapy of human prostate cancer when used in combination with conventional radiotherapy. On the basis of our observations, we propose a multistep self-assembly process and Tf-facilitated DNA cocondensation model that may provide an explanation for the resultant small size and effectiveness of our nanostructural Tf-lipoplex system.

Inhibitory effects of the combination of HER-2 antisense oligonucleotide and chemotherapeutic agents used for the treatment of human breast cancer

Poor response to chemotherapy in patients with breast cancer is often associated with overexpression of HER-2/neu. Interference with HER-2 mRNA translation by means of antisense oligonucleotides might improve the efficacy of chemotherapy. To test this hypothesis, eight breast cancer cell lines and a normal human fibroblast cell line were examined for their level of HER-2 expression, their sensitivity to phosphorothioate antisense oligonucleotides (AS HER-2 ODN), and to various chemotherapeutic agents, and the combination of the two. No correlation was found between the intrinsic HER-2 level and either the sensitivity to a particular chemotherapeutic agent alone, or the amount of growth inhibition observed with a specific AS HER-2 ODN concentration. Although sequence specificity and extent of AS HER-2 ODN inhibition of HER-2 synthesis were somewhat higher in the HER-2 overexpressing MDA-MB-453 and SK-BR-3 cells, we found that antisense treatment significantly sensitized all of the breast cancer cells, even MDA-MB-231 and MDA-MB-435 cells, with approximately basal levels of HER-2, to various chemotherapeutic agents. In addition, the combination of AS HER-2 ODN and taxol was shown to synergistically induce apoptosis in MDA-MB-435. These results demonstrate that overexpression of HER-2 would not be a prerequisite for the effective use of AS HER-2 ODN as a combination treatment modality for breast cancer and suggest that the use of AS HER-2 ODN, as part of a combination treatment modality, need not be limited to breast tumors that display elevated levels of HER-2.

Systemic p53 gene therapy of cancer with immunolipoplexes targeted by anti-transferrin receptor scFv

BACKGROUND

A long-standing goal in genetic therapy for cancer is a systemic gene delivery system that selectively targets tumor cells, including metastases. Here we describe a novel cationic immunolipoplex system that shows high in vivo gene transfer efficiency and anti- tumor efficacy when used for systemic p53 gene therapy of cancer.

MATERIALS AND METHODS

A cationic immunolipoplex incorporating a biosynthetically lipid-tagged, anti-transferrin receptor single-chain antibody (TfRscFv), was designed to target tumor cells both in vitro and in vivo. A human breast cancer metastasis model was employed to evaluate the in vivo efficacy of systemically administered, TfRscFv-immunolipoplex-mediated, p53 gene therapy in combination with docetaxel.

RESULTS

The TfRscFv-targeting cationic immunolipoplex had a size of 60-100 nm, showed enhanced tumor cell binding, and improved targeted gene delivery and transfection efficiencies, both in vitro and in vivo. The p53 tumor suppressor gene was not only systemically delivered by the immunolipoplex to human tumor xenografts in nude mice but also functionally expressed. In the nude mouse breast cancer metastasis model, the combination of the p53 gene delivered by the systemic administration of the TfRscFv-immunolipoplex and docetaxel resulted in significantly improved efficacy with prolonged survival.

CONCLUSIONS

This is the first report using scFv-targeting immunolipoplexes for systemic gene therapy. The TfRscFv has a number of advantages over the transferrin (Tf) molecule itself: (1) scFv has a much smaller size than Tf producing a smaller immunolipoplex giving better penetration into solid tumors; (2) unlike Tf, the scFv is a recombinant protein, not a blood product; (3) large scale production and strict quality control of the recombinant scFv, as well as scFv-immunolipoplex, are feasible. The sensitization of tumors to chemotherapy by this tumor-targeted and efficient p53 gene delivery method could lower the effective dose of the drug, correspondingly lessening the severe side effects, while decreasing the possibility of recurrence. Moreover, this approach is applicable to both primary and recurrent tumors, and more significantly, metastatic disease. The TfRscFv-targeting of cationic immunolipoplexes is a promising method of tumor targeted gene delivery that can be used for systemic gene therapy of cancer with the potential to critically impact the clinical management of cancer.

Downmodulation of bFGF-binding protein expression following restoration of p53 function

Angiogenesis is a requirement for solid tumor growth. Therefore, inhibition of this neovascularization is one mechanism by which restoration of wtp53 function may lead to tumor regression. Here we report that adenoviral vector-mediated wild-type p53 transduction results in growth inhibition of squamous cell carcinoma of the head and neck tumor cells both in vitro and in a xenograft mouse model. This growth inhibition is associated with the down-regulation of the expression of fibroblast growth factor binding protein, a secreted protein required for the activation of angiogenic factor basic FGF. These findings suggest that wtp53-induced tumor regression is due, at least in part, to antiangiogenesis mediated by the downmodulation of fibroblast growth factor binding protein.

Tumor-targeted p53-gene therapy enhances the efficacy of conventional chemo/radiotherapy

A long-standing goal in gene therapy for cancer is a stable, low toxic, systemic gene delivery system that selectively targets tumor cells, including metastatic disease. Progress has been made toward developing non-viral, pharmaceutical formulations of genes for in vivo human therapy, particularly cationic liposome-mediated gene transfer systems. Ligand-directed tumor targeting of cationic liposome-DNA complexes (lipoplexes) is showing promise for targeted gene delivery and systemic gene therapy. Lipoplexes directed by ligands such as folate, transferrin or anti-transferrin receptor scFv, showed tumor-targeted gene delivery and expression in human breast, prostate, head and neck cancers. The two elements, ligand/receptor and liposome composition, work together to realize the goal of functional tumor targeting of gene therapeutics. The tumor suppressor gene, p53, has been shown to be involved in the control of DNA damage-induced apoptosis. Loss or malfunction of this p53-mediated apoptotic pathway has been proposed as one mechanism by which tumors become resistant to chemotherapy or radiation. The systemically delivered ligand-liposome-p53 gene therapeutics resulted in efficient expression of functional wild-type p53, sensitizing the tumors to chemotherapy and radiotherapy. This is a novel strategy combining current molecular medicine with conventional chemotherapy and radiotherapy for the treatment of cancer. The systemic delivery of normal tumor suppressor gene p53 by a non-viral, tumor-targeted delivery system as a new therapeutic intervention has the potential to critically impact the clinical management of cancer.