A Pralidoxime Nanocomplex Formulation Targeting Transferrin Receptors for Reactivation of Brain Acetylcholinesterase After Exposure of Mice to an Anticholinesterase Organophosphate

Introduction

Organophosphates are among the deadliest of known chemicals based on their ability to inactivate acetylcholinesterase in neuromuscular junctions and synapses of the central and peripheral nervous systems. The consequent accumulation of acetylcholine can produce severe acute toxicities and death. Oxime antidotes act by reactivating acetylcholinesterase with the only such reactivator approved for use in the United States being 2-pyridine aldoxime methyl chloride (a.k.a., pralidoxime or 2-PAM). However, this compound does not cross the blood-brain barrier readily and so is limited in its ability to reactivate acetylcholinesterase in the brain.

Methods

We have developed a novel formulation of 2-PAM by encapsulating it within a nanocomplex designed to cross the blood-brain barrier via transferrin receptor-mediated transcytosis. This nanocomplex (termed scL-2PAM) has been subjected to head-to-head comparisons with unencapsulated 2-PAM in mice exposed to paraoxon, an organophosphate with anticholinesterase activity.

Results and Discussion

In mice exposed to a sublethal dose of paraoxon, scL-2PAM reduced the extent and duration of cholinergic symptoms more effectively than did unencapsulated 2-PAM. The scL-2PAM formulation was also more effective than unencapsulated 2-PAM in rescuing mice from death after exposure to otherwise-lethal levels of paraoxon. Improved survival rates in paraoxon-exposed mice were accompanied by a higher degree of reactivation of brain acetylcholinesterase.

Conclusion

Our data indicate that scL-2PAM is superior to the currently used form of 2-PAM in terms of both mitigating paraoxon toxicity in mice and reactivating acetylcholinesterase in their brains.

TP53 Gene Therapy as a Potential Treatment for Patients with COVID-19

SGT-53 is a novel investigational agent that comprises an immunoliposome carrying a plasmid vector driving expression of the human TP53 gene that encodes wild-type human p53. SGT-53 is currently in phase II human trials for advanced pancreatic cancer. Although p53 is best known as a tumor suppressor, its participation in both innate and adaptive immune responses is well documented. It is now clear that p53 is an important component of the host response to various viral infections. To facilitate their viral life cycles, viruses have developed a diverse repertoire of strategies for counteracting the antiviral activities of host immune system by manipulating p53-dependent pathways in host cells. Coronaviruses reduce endogenous p53 levels in the cells they infect by enhancing the degradation of p53 in proteasomes. Thus, interference with p53 function is an important component in viral pathogenesis. Transfection of cells by SGT-53 has been shown to transiently produce exogenous p53 that is active as a pleiotropic transcription factor. We herein summarize the rationale for repurposing SGT-53 as a therapy for infection by SARS-CoV-2, the pathogen responsible for the COVID-19 pandemic. Because p53 regulation was found to play a crucial role in different infection stages of a wide variety of viruses, it is rational to believe that restoring p53 function based on SGT-53 treatment may lead to beneficial therapeutic outcomes for infectious disease at large including heretofore unknown viral pathogens that may emerge in the future.

A phase II trial combining tumor-targeting TP53 gene therapy with gemcitabine/nab-paclitaxel as a second-line treatment for metastatic pancreatic cancer

4139

Background: Nearly all stage IV pancreatic adenocarcinoma (PAC) patients progress after first-line treatment, and second-line options are limited. SGT-53 is an investigational product for tumor-targeted TP53 gene therapy that has completed phase Ia/Ib trials [Senser et al (2013), Mol Ther 21:1096; Pirollo et al (2016) Mol Ther 24:1697]. Methods: Here we provide an interim analysis of a Phase II trial (SGT53-02-1; NCT02340117) combining SGT-53 with gemcitabine/nab-paclitaxel (GEM/ABX). Eligible were first-line patients or those who had progressed after FOLFIRINOX (FFX) and/or gemcitabine-based therapy (second-line). In a 7-week treatment cycle, SGT-53 (3.6 mg DNA) was given once or twice weekly with GEM/ABX (1000 mg/m2/wk and 125 mg/m2/wk, respectively, for 3 of 4 weeks). Progression-free survival (PFS) and objective response rate (ORR) are primary endpoints.Overall survival (OS) and PFS are estimated by Kaplan-Meier analysis. Results: Of all evaluable patients (n=20), best response in 7 patients was determined to be partial response (PR) and 13 had stable disease (SD); none had progressive disease. In the second-line patients (n=11) there were 5 PR and 6 SD after 9 had failed FFX treatment, 3 had failed gemcitabine-based treatment and 1 had failed both. For patients with elevated CA19-9, SGT-53 + GEM/ABX resulted in marked reductions in the tumor marker. Published data for patients with PAC after therapy failure [Mita et al (2019) J Clin Med 8: 761; Portal et al (2015) Br J Cancer 113:989; Wang-Gillam et al (2016) Lancet 387:545] are shown for comparison. Notably, mPFS in our second-line patients was 7.4 months versus 3.1 months for the approved second-line therapy [Wang-Gillam et al (2016)]. This improvement in PFS exceeds the benchmark proposed to predict a clinically meaningful Phase III trial [Rahib et al (2016) Lancet Oncol 2:1209]. Conclusions: Our data suggest a clinically meaningful benefit of adding SGT-53 to GEM/ABX particularly for second-line PAC patients, most of whom had failed prior FFX treatment. Clinical trial information: NCT02340117. [Table: see text]

Activating p53 family member TAp63: A novel therapeutic strategy for targeting p53-altered tumors

BACKGROUND

Over 96% of high-grade ovarian carcinomas and 50% of all cancers are characterized by alterations in the p53 gene. Therapeutic strategies to restore and/or reactivate the p53 pathway have been challenging. By contrast, p63, which shares many of the downstream targets and functions of p53, is rarely mutated in cancer.

METHODS

A novel strategy is presented for circumventing alterations in p53 by inducing the tumor-suppressor isoform TAp63 (transactivation domain of tumor protein p63) through its direct downstream target, microRNA-130b (miR-130b), which is epigenetically silenced and/or downregulated in chemoresistant ovarian cancer.

RESULTS

Treatment with miR-130b resulted in: 1) decreased migration/invasion in HEYA8 cells (p53 wild-type) and disruption of multicellular spheroids in OVCAR8 cells (p53-mutant) in vitro, 2) sensitization of HEYA8 and OVCAR8 cells to cisplatin (CDDP) in vitro and in vivo, and 3) transcriptional activation of TAp63 and the B-cell lymphoma (Bcl)-inhibitor B-cell lymphoma 2-like protein 11 (BIM). Overexpression of TAp63 was sufficient to decrease cell viability, suggesting that it is a critical downstream effector of miR-130b. In vivo, combined miR-130b plus CDDP exhibited greater therapeutic efficacy than miR-130b or CDDP alone. Mice that carried OVCAR8 xenograft tumors and were injected with miR-130b in 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) liposomes had a significant decrease in tumor burden at rates similar to those observed in CDDP-treated mice, and 20% of DOPC-miR-130b plus CDDP-treated mice were living tumor free. Systemic injections of scL-miR-130b plus CDDP in a clinically tested, tumor-targeted nanocomplex (scL) improved survival in 60% and complete remissions in 40% of mice that carried HEYA8 xenografts.

CONCLUSIONS

The miR-130b/TAp63 axis is proposed as a new druggable pathway that has the potential to uncover broad-spectrum therapeutic options for the majority of p53-altered cancers.

Targeted nanocomplex carrying siRNA against MALAT1 sensitizes glioblastoma to temozolomide

Intrinsic therapeutic resistance especially in cancer stem cells (CSCs) together with extensive tumor cell infiltration and restricted permeation of the blood-brain barrier (BBB) by drugs may all contribute to the treatment failure in patients with glioblastoma multiforme (GBM). Accumulating evidence suggests that long non-coding RNA (lncRNA), metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) plays a role in tumor cell infiltration and therapeutic resistance of GBM. Using our tumor-targeted nanocomplex, we have modulated the expression of MALAT1 and investigated its impact on GBM cells. Importantly, our nanocomplex is able to target CSCs that are considered to be the prime culprits in therapeutic resistance and recurrence of GBM. Attenuation of MALAT1 by RNA interference significantly lowered the growth, motility and stemness of GBM cells. In addition, silencing of MALAT1 clearly improved the sensitivity of GBM cells to chemotherapeutic agents including the current first-line therapy of GBM [temozolomide (TMZ)]. In animal models of GBM, tumor involution with a modest but statistically significant survival benefit was achieved with concurrent treatment of TMZ and nanocomplex-mediated silencing of MALAT1. These results suggest that combining standard TMZ treatment with lncRNA-targeting therapies using our nanocomplex could substantially enhance the very poor prognosis for GBM patients.

Integrated Genomic and Functional microRNA Analysis Identifies miR-30-5p as a Tumor Suppressor and Potential Therapeutic Nanomedicine in Head and Neck Cancer

PURPOSE

To identify deregulated and inhibitory miRNAs and generate novel mimics for replacement nanomedicine for head and neck squamous cell carcinomas (HNSCC).

EXPERIMENTAL DESIGN

We integrated miRNA and mRNA expression, copy number variation, and DNA methylation results from The Cancer Genome Atlas (TCGA), with a functional genome-wide screen.

RESULTS

We reveal that the miR-30 family is commonly repressed, and all 5 members sharing these seed sequence similarly inhibit HNSCC proliferation in vitro. We uncover a previously unrecognized inverse relationship with overexpression of a network of important predicted target mRNAs deregulated in HNSCC, that includes key molecules involved in proliferation (EGFR, MET, IGF1R, IRS1, E2F7), differentiation (WNT7B, FZD2), adhesion, and invasion (ITGA6, SERPINE1). Reexpression of the most differentially repressed family member, miR-30a-5p, suppressed this mRNA program, selected signaling proteins and pathways, and inhibited cell proliferation, migration, and invasion in vitro. Furthermore, a novel miR-30a-5p mimic formulated into a targeted nanomedicine significantly inhibited HNSCC xenograft tumor growth and target growth receptors EGFR and MET in vivo. Significantly decreased miR-30a/e family expression was related to DNA promoter hypermethylation and/or copy loss in TCGA data, and clinically with decreased disease-specific survival in a validation dataset. Strikingly, decreased miR-30e-5p distinguished oropharyngeal HNSCC with poor prognosis in TCGA (P = 0.002) and validation (P = 0.007) datasets, identifying a novel candidate biomarker and target for this HNSCC subset.

CONCLUSIONS

We identify the miR-30 family as an important regulator of signal networks and tumor suppressor in a subset of HNSCC patients, which may benefit from miRNA replacement nanomedicine therapy.

Abstract 4401: Integrated genomic and functional microRNA analysis identifies miR-30-5p as a tumor suppressor and novel therapeutic nanomedicine in head and neck cancer

We have developed an integrative approach to elucidate the functional role of deregulated microRNAs (miRs) and identify candidates for miR replacement therapy in cancer, applied here to head and neck squamous cell carcinomas (HNSCC). Our method involves integration of results from TCGA and other validation databases of genetic and expression data, including: miR expression, mRNA expression, copy number variation, DNA methylation. This data is then intersected with functional in vitro genome-wide miR screening for anti-proliferative miR mimics. We report that the miR-30-5p family is commonly repressed and correlates with overexpression of a broad network of proliferative and metastasis-related oncogenic mRNAs, including the growth receptors EGFR, MET and IGF1R. We show that re-expression of miR-30a-5p repressed this gene program, downstream signaling, proliferation, migration, and invasion in vitro. We have developed a chemically modified mimic of miR-30-5p with 50x improved stability in human serum, and 5X improvement in IC50 in vitro by XTT assay. We have formulated our novel miR-30a-5p mimic into Transferrin Receptor targeted nanoparticles which strongly inhibited HNSCC xenograft tumor growth, and regulated miR-30-5p family targets in vivo. Together with data linking decreased miR-30 family expression with DNA copy loss and promoter hypermethylation, and clinical disease-specific survival, for the first time, we have reported a more global picture of the function of this important tumor suppressor and identified a subset of patients that may benefit from miR replacement therapy with our novel miR-30-5p based nanomedicine.

This research was supported by NIDCD intramural projects ZIA-DC-000073, 74, and NCI grant U43CA22156701.

Citation Format: Anthony D. Saleh, Robert F. Place, Hui Cheng, Rita Das, Thomas M. Harris, Geoffrey Childs, Gordon A. Robertson, Kathleen F. Pirollo, Esther H. Chang, Zhong Chen, Carter Van Waes. Integrated genomic and functional microRNA analysis identifies miR-30-5p as a tumor suppressor and novel therapeutic nanomedicine in head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4401.

Nanotherapeutics for Gene Modulation that Prevents Apoptosis in the Brain and Fatal Neuroinflammation

The failure of therapeutic agents to cross the blood-brain barrier (BBB) has been a major impediment in the treatment of neurological disorders and brain tumors. We have addressed this issue using an immunoliposome nanocomplex (designated scL) that delivers therapeutic nucleic acids across the BBB into the deep brain via transcytosis mediated by transferrin receptors. We validated brain delivery of payloads after systemic administration by monitoring uptake of fluorescently labeled payloads and by confirming up- or down-modulation of specific target gene expression in the brain, mainly in neuronal cells. As proof of concept for the therapeutic potential of our delivery system, we employed scL delivering an siRNA targeting tumor necrosis factor alpha to suppress neuroinflammation and neuronal apoptosis and to protect mice in lethal endotoxemia triggered by bacterial lipopolysaccharide. Brain delivery of therapeutic payloads via scL has major implications for the development of treatments for neurological disorders and brain tumors.

Abstract CT059: Systemic administration using targeted gene delivery with SGT-RB94 shows evidence of tumor targeting and anticancer activity: a phase I first-in-man trial

Background: Development of gene therapy has been limited by our inability to systemically administer treatment which selectively targets tumor tissue. We developed an SGT-RB94 nanocomplex composed of cationic liposome encapsulating plasmid DNA encoding the RB94 gene which had previously been shown to selectively kill cancer cells but not non-transformed human cells. The surface of the liposome is decorated with a single chain antibody fragment to the transferrin receptor to target the nanocomplex to cancer cells.

Methods: We performed a phase I trial of single agent SGT-RB94 in patients with previously treated metastatic cancer. Treatment with SGT-RB94 was administered twice a week for 3 weeks out of four using a fixed at a fixed DNA dose of 0.6, 1.2, or 2.4 mg pDNA. Radiographic imaging was performed every 2 cycles to evaluate for response. When possible, a biopsy of a metastatic site was performed, after beginning treatment to evaluate for targeting of the gene product. PCR was performed to show expression of SGT-94 in RB+ tumors, RB94 protein production was confirmed using Western blotting.

Results: Thirteen patients were treated with 11 clinically evaluable for response. Dose-limiting toxicity was not observed at the 2.4 mg dose. A total of 181 doses of SGT-94 were administered. The treatment was well tolerated with the most frequent treatment related toxicities being Grade 1-2 fever and chills (27%), thrombocytopenia (45%), neutropenia (18%), and hypotension (18%). The only grade 3-4 toxicity were lymphopenia (9%), and neutropenia (9%). The fever/chills and hypotension most typically occurred after the first dose, and responding with steroids. The neutropenia and thrombocytopenia were also transient and improved with continued dosing.

There was evidence of clinical activity with a complete response in a lung metastases; this patient was retreated upon progression, and had a partial response in his peritoneal implants. Two patients continued to have stable disease after 4-5 cycles of treatment. Two patients had RB- tumors by immunohistochemistry. One had a post-treatment biopsy showing evidence of cytoplasmic staining for the RB protein with extensive tumor necrosis following treatment, but this tumor ultimately progressed. One patient with stable disease had surgical consolidation with wedge resection of his lung metastases which showed RB94 expression by PCR, and protein production by Western blot in two separate tumors, but not in his normal lung tissue.

Conclusions: Systemic delivery of SGT-RB94 was well tolerated with evidence of clinical activity and selective targeting of tumor tissue, overcoming a major limitation to current gene therapy strategies. Further development of SGT-RB94 as a treatment modality is warranted.

Citation Format: Arlene Siefker-Radtke, Xin-qiao Zhang, Kathleen F. Pirollo, Esther H. Chang, Chris P. Leung, Charles Guo, Randall E. Millikan, William F. Benedict. Systemic administration using targeted gene delivery with SGT-RB94 shows evidence of tumor targeting and anticancer activity: a phase I first-in-man trial. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT059.

Safety and Efficacy in Advanced Solid Tumors of a Targeted Nanocomplex Carrying the p53 Gene Used in Combination with Docetaxel: A Phase 1b Study

Loss of p53 suppressor function, through mutations or inactivation of the p53 pathway, occurs in most human cancers. SGT-53 is a liposomal nanocomplex designed for systemic, tumor-targeting delivery of the wt p53 gene. In this nanodelivery system, an anti-transferrin receptor single-chain antibody fragment serves as the targeting moiety. In an initial phase 1 trial in patients with advanced solid tumors, SGT-53 demonstrated tumor-specific targeting, was shown to be well tolerated, and was associated with an antitumor effect in several patients. Our preclinical studies have also demonstrated enhanced antitumor activity with the combination of SGT-53 and docetaxel. Thus, this dose-escalation trial was undertaken to assess the combination of SGT-53 and docetaxel for safety and potential efficacy in 14 advanced cancer patients. Results reveal that the combination of SGT-53 (maximum dose, 3.6 mg DNA/infusion) and docetaxel (75 mg/m(2)/infusion) was well tolerated. Moreover, clinical activity involving 12 evaluable patients was observed. Three of these patients achieved RECIST-verified partial responses with tumor reductions of -47%, -51%, and -79%. Two others had stable disease with significant shrinkage (-25% and -16%). These results support phase 2 testing of SGT-53 in combination with docetaxel.

Encapsulation of temozolomide in a tumor-targeting nanocomplex enhances anti-cancer efficacy and reduces toxicity in a mouse model of glioblastoma

Although temozolomide (TMZ) is the current first-line chemotherapy for glioblastoma multiforme (GBM), most patients either do not respond or ultimately fail TMZ treatment. Both intrinsic tumor resistance and limited access of TMZ to brain tumors as a result of the blood-brain barrier (BBB) contribute to poor response and ultimately to poor prognosis for GBM patients. We have developed a "dual-targeting" nanomedicine that both actively crosses the BBB and actively targets cancer cells once in the brain parenchyma. This nanomedicine (termed scL-TMZ) is sized ~40 nm and comprised of a cationic liposome (DOTAP:DOPE) encapsulating TMZ. The surface of liposome is decorated with anti-transferrin receptor single-chain antibody fragments to facilitate the crossing of the BBB by the scL-TMZ in addition to targeting GBM in the brain. This novel formulation was found to be markedly more effective than standard TMZ in both TMZ-resistant and TMZ-sensitive GBM. Encapsulation of TMZ also markedly enhanced its efficacy in killing a variety of non-GBM tumor cells. The scL-TMZ nanocomplex was shown to target cancer stem cells, which have been linked to both drug resistance and recurrence in GBM. Most significantly, systemically administered scL-TMZ significantly prolonged survival in mice bearing intracranial GBM tumors. The improved efficacy of scL-TMZ compared to standard TMZ was accompanied by reduced toxicity, so we conclude that the scL-TMZ nanomedicine holds great promise as a more effective therapy for GBM and other tumor types.

Effective treatment of glioblastoma requires crossing the blood-brain barrier and targeting tumors including cancer stem cells: The promise of nanomedicine

Glioblastoma multiforme (GBM) is the most aggressive and lethal type of brain tumor. Both therapeutic resistance and restricted permeation of drugs across the blood-brain barrier (BBB) play a major role in the poor prognosis of GBM patients. Accumulated evidence suggests that in many human cancers, including GBM, therapeutic resistance can be attributed to a small fraction of cancer cells known as cancer stem cells (CSCs). CSCs have been shown to have stem cell-like properties that enable them to evade traditional cytotoxic therapies, and so new CSC-directed anti-cancer therapies are needed. Nanoparticles have been designed to selectively deliver payloads to relevant target cells in the body, and there is considerable interest in the use of nanoparticles for CSC-directed anti-cancer therapies. Recent advances in the field of nanomedicine offer new possibilities for overcoming CSC-mediated therapeutic resistance and thus significantly improving management of GBM. In this review, we will examine the current nanomedicine approaches for targeting CSCs and their therapeutic implications. The inhibitory effect of various nanoparticle-based drug delivery system towards CSCs in GBM tumors is the primary focus of this review.

Isolation and Culturing of Glioma Cancer Stem Cells

In many human cancers including malignant glioblastoma multiforme (GBM), cancer stem cells (CSCs) are thought to be responsible for tumor initiation, metastasis and resistance to conventional anti-cancer therapies. Therefore, a CSC-targeted drug delivery strategy to eliminate CSCs is a desirable approach for developing a more effective therapeutic. Moreover, isolated CSCs will provide an invaluable tool for studying the underlying cellular mechanisms of tumor development and provide insight into therapeutic options for successful eradication of CSCs. This unit describes a method for the isolation and culture of CSCs from human GBM tumor tissue.

A tumor-targeting p53 nanodelivery system limits chemoresistance to temozolomide prolonging survival in a mouse model of glioblastoma multiforme

Development of temozolomide (TMZ) resistance contributes to the poor prognosis for glioblastoma multiforme (GBM) patients. It was previously demonstrated that delivery of exogenous wild-type tumor suppressor gene p53 via a tumor-targeted nanocomplex (SGT-53) which crosses the blood-brain barrier could sensitize highly TMZ-resistant GBM tumors to TMZ. Here we assessed whether SGT-53 could inhibit development of TMZ resistance. SGT-53 significantly chemosensitized TMZ-sensitive human GBM cell lines (U87 and U251), in vitro and in vivo. Furthermore, in an intracranial GBM tumor model, two cycles of concurrent treatment with systemically administered SGT-53 and TMZ inhibited tumor growth, increased apoptosis and most importantly, significantly prolonged median survival. In contrast TMZ alone had no significant effect on median survival compared to a single cycle of TMZ. These results suggest that combining SGT-53 with TMZ appears to limit development of TMZ resistance, prolonging its anti-tumor effect and could be a more effective therapy for GBM.

FROM THE CLINICAL EDITOR

Using human glioblastoma multiforma cell lines, this research team demonstrated that the delivery of exogenous wild-type tumor suppressor gene p53 via a tumor-targeted nanocomplex limited the development of temozolomide resistance and prolonged its anti-tumor effect, which may enable future human application of this or similar techniques.

A nanoparticle carrying the p53 gene targets tumors including cancer stem cells, sensitizes glioblastoma to chemotherapy and improves survival

Temozolomide (TMZ)-resistance in glioblastoma multiforme (GBM) has been linked to upregulation of O(6)-methylguanine-DNA methyltransferase (MGMT). Wild-type (wt) p53 was previously shown to down-modulate MGMT. However, p53 therapy for GBM is limited by lack of efficient delivery across the blood brain barrier (BBB). We have developed a systemic nanodelivery platform (scL) for tumor-specific targeting (primary and metastatic), which is currently in multiple clinical trials. This self-assembling nanocomplex is formed by simple mixing of the components in a defined order and a specific ratio. Here, we demonstrate that scL crosses the BBB and efficiently targets GBM, as well as cancer stem cells (CSCs), which have been implicated in recurrence and treatment resistance in many human cancers. Moreover, systemic delivery of scL-p53 down-modulates MGMT and induces apoptosis in intracranial GBM xenografts. The combination of scL-p53 and TMZ increased the antitumor efficacy of TMZ with enhanced survival benefit in a mouse model of highly TMZ-resistant GBM. scL-p53 also sensitized both CSCs and bulk tumor cells to TMZ, increasing apoptosis. These results suggest that combining scL-p53 with standard TMZ treatment could be a more effective therapy for GBM.

Transferrin receptor targeting nanomedicine delivering wild-type p53 gene sensitizes pancreatic cancer to gemcitabine therapy

To overcome gene therapy barriers such as low transfection efficiency and nonspecific delivery, liposomal nanoparticles targeted by a single-chain antibody fragment to the transferrin receptor (TfRscFv) delivering wild-type (wt) human p53 (SGT-53) were developed for tumor-specific targeting. We hypothesize that SGT-53 in combination with gemcitabine will demonstrate enhanced therapeutic benefit in an in vivo metastatic pancreatic cancer model. Intrasplenic injection of 1 × 10(6) Panc02 murine pancreatic cancer cells was used to generate in vivo hepatic metastatic tumors. Nanoparticle localization was assessed by tail vein injection of TfRscFv with fluorescently labeled oligonucleotides (6-carboxyfluorescein phosphoramidite (6FAM) ODN) imaged by Xenogen IVIS 200 scan. SGT-53 (equivalent to 30 μg of p53 intravenously) and gemcitabine (20 mg/kg intraperitoneally) alone and in combination were administered biweekly and compared with untreated mice. Survival was determined by blinded daily assessment of morbidity. Human wtp53 expression and transferrin levels in the tumors were assessed by western blot analysis. Tumor burden was quantified by liver weight. Xenogen imaging demonstrated tumor-specific uptake of TfRscFv-6FAM ODN. Exogenous human wtp53 protein was detected in the SGT-53-treated tumors compared with control. Compared with untreated mice with metastatic tumors demonstrating median survival of 20 days, SGT-53, gemcitabine and the combination demonstrated improved median survival of 29, 30 and 37 days, respectively. The combination treatment prolonged median survival when compared with single drug treatment and decreased tumor burden. The tumor targeting liposomal-based SGT-53 nanoparticle is capable of sensitizing pancreatic cancer to conventional chemotherapy in pancreatic cancer models. This approach has the potential to be translated into a new, more effective therapy for pancreatic cancer. Further optimization is ongoing, moving towards a Phase 1B/2 clinical trial.

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.

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.

Tp53 gene therapy: a key to modulating resistance to anticancer therapies?

Abnormalities in the p53 tumor suppressor have been identified in over 60% of human cancers. The status of p53 within tumor cells has been proposed to be one of the major determinants of the response to anticancer therapies. In this review we examine the relationship between functional p53 and sensitivity, or resistance, to chemotherapy and radiotherapy. We also discuss the potential of current gene-therapy approaches to restore functional p53 to tumors as a means of modulating the effects of radiation and chemotherapy.

Does p53 status influence tumor response to anticancer therapies?

Abnormalities in the tumor suppressor gene p53 have been identified in over 60% of human cancers. Since it plays such a pivotal role in cell growth regulation and apoptosis, the status of the p53 gene has been proposed as one of the major determinants of a tumor's response to anticancer therapies. In this review we examine the relationship between functional p53 and sensitivity/resistance to both chemotherapy and radiotherapy, and discuss the potential use of some of the current gene therapy approaches to restore functional p53 to tumors as a means of modulating the effects of radiation and chemotherapy.

Non-viral gene delivery for p53

Abnormality in the tumor suppressor gene p53 is one of the most common occurrences associated with human neoplasia. Consequently, restoration of wild-type p53 function is seen as a particularly promising approach for cancer gene therapy. In recent years, considerable research effort has centered upon developing and improving non-viral delivery systems as alternatives to viral vectors for gene delivery. These methods include the use of lipoplexes and polyplexes, and even delivery of naked DNA. Optimally effective cancer gene therapy requires treatment of metastatic as well as local disease, and to achieve this end, systemic delivery systems for therapeutic genes will be required. This review will discuss some of the recent advances in ways to improve targeting, transfection efficiency and stability for systemic, non-viral p53 gene therapy.

Transferrin-liposome-mediated systemic p53 gene therapy in combination with radiation results in regression of human head and neck cancer xenografts

The use of cationic liposomes as nonviral vehicles for the delivery of therapeutic molecules is becoming increasingly prevalent in the field of gene therapy. We have previously demonstrated that the use of the transferrin ligand (Tf) to target a cationic liposome delivery system resulted in a significant increase in the transfection efficiency of the complex [Xu, L., Pirollo, K.F., and Chang, E.H. (1997). Hum. Gene Ther. 8, 467-475]. Delivery of wild-type (wt) p53 to a radiation-resistant squamous cell carcinoma of the head and neck (SCCHN) cell line via this ligand-targeted, liposome complex was also able to revert the radiation resistant phenotype of these cells in vitro. Here we optimized the Tf/liposome/DNA ratio of the complex (LipT) for maximum tumor cell targeting, even in the presence of serum. The efficient reestablishment of wtp53 function in these SCCHN tumor cells in vitro, via the LipT complex, restored the apoptotic pathway, resulting in a significant increase in radiation-induced apoptosis that was directly proportional to the level of exogenous wtp53 in the tumor cells. More significantly, intravenous administration of LipT-p53 markedly sensitized established SCCHN nude mouse xenograft tumors to radiotherapy. The combination of systemic LipT-p53 gene therapy and radiation resulted in complete tumor regression and inhibition of their recurrence even 6 months after the end of all treatment. These results indicate that this tumor-specific, ligand-liposome delivery system for p53 gene therapy, when used in concert with conventional radiotherapy, can provide a new and more effective means of cancer treatment.

Restoration of the G1 checkpoint and the apoptotic pathway mediated by wild-type p53 sensitizes squamous cell carcinoma of the head and neck to radiotherapy

BACKGROUND

A significant number of squamous cell carcinomas of the head and neck (SCCHN) resist radiation treatment, the most common form of adjuvant therapy for this disease. The presence of a mutant form of the tumor suppressor gene p53 has been correlated with disruption of programmed cell death (apoptosis) and reduced cell cycle arrest, resulting in increased radiation resistance and survival.

METHODS AND RESULTS

We introduced by means of an adenoviral vector a functional p53 gene into a radiation-resistant SCCHN cell line that harbors mutant p53. Replacement of wild-type p53 restored the G1 block and apoptosis in these cells in vitro. Moreover, introduction of wild-type p53 sensitized SCCHN-induced mouse xenografts to radiotherapy in vivo.

CONCLUSION

The combination of p53 replacement gene therapy with conventional radiotherapy may treat SCCHN more effectively.

p53 mediated sensitization of squamous cell carcinoma of the head and neck to radiotherapy

Radiation resistant squamous cell carcinoma of the head and neck cell line JSQ-3 carries a mutant form of tumor suppressor gene p53. Treatment of these cells with an adenoviral vector containing wild-type p53 (Av1p53) was able to inhibit their growth in vitro and in vivo while having no effect on normal cells. More significantly, introduction of wtp53 also reduced the radiation-resistance level of this cell line in vitro, in a viral dose-dependent manner. Furthermore, this radiosensitization also carried over to the in vivo situation where the response of JSQ-3 cell-induced mouse xenografts to radiotherapy was markedly enhanced after treatment with Av1p53. Complete, long-term regression of the tumors for up to 162 days was observed when a single dose of Av1p53 was administered in combination with ionizing radiation, demonstrating the effectiveness of this combination of gene therapy and conventional radiotherapy. This sensitization of tumors to radiation therapy by replacement of wtp53 could significantly decrease the rate of recurrence after radiation treatment. Since radiation is one of the most prevalent forms of adjunctive therapy for a variety of cancers, these results have great relevance in moving toward an improved cancer therapy.

Transferrin-liposome-mediated p53 sensitization of squamous cell carcinoma of the head and neck to radiation in vitro

Wild-type (wt) p53 DNA was transfected into the radioresistant human cell line JSQ-3, established from a squamous cell carcinoma of the head and neck (SCCHN), using a transferrin-liposome system, and the ability of the introduced wt p53 to sensitize the transfected JSQ-3 cells to ionizing radiation was examined. Transferrin increased the in vitro transfection efficiency of cationic liposomes up to 70-80% in JSQ-3 cells, representing a 6- to 10-fold increase over liposome transfection alone. The exogenous wt p53 was expressed at high levels in transferrin-liposome-DNA-transfected cells and resulted in the reversion of the radioresistant phenotype of the JSQ-3 cells in a DNA dose-dependent manner. The D10 values were reduced from 6.36 +/- 0.54 Gy to 4.13 +/- 0.06 Gy, a value in the radiosensitive range. In vivo, the intratumoral injection of the transferrin-liposome system resulted in a higher number of transfected tumor cells in the JSQ-3 induced nude mouse xenografts when compared with transfection by liposome alone. The results indicate that the combination of p53 replacement gene transduction, mediated by the relatively safe transferrin-liposome system, and conventional ionizing radiation may provide a more effective treatment for head and neck cancer.

Evidence supporting a signal transduction pathway leading to the radiation-resistant phenotype in human tumor cells

A signal transduction pathway, involving oncogenes and their normal counterparts the proto-oncogenes, analogous to that for cell growth and differentiation has been proposed to lead to the phenotype of cellular radioresistance (RR). In this report we provide evidence demonstrating the existence of such a pathway by using antisense oligonucleotides (ASO) to reverse the RR phenotype. Utilizing ASO directed against the raf-1 gene, a central component of this proposed pathway, we were able to reverse the RR phenotype of human tumor cell lines having elevated HER-2 expression or a mutant form of Ha-ras, two genes upstream of raf-1 in signal transduction. Additionally, anti-ras ASO were able to radiosensitize HER-2 overexpressing cells. These results, which verify the presence of a signaling pathway leading to cellular RR, also have possible clinical implications for the use of ASO as a means to sensitize radioresistant tumors to radiation therapy.

Cytogenetic response to G2-phase X irradiation in relation to DNA repair and radiosensitivity in a cancer-prone family with Li-Fraumeni syndrome

Noncancerous skin fibroblasts from six family members with Li-Fraumeni syndrome, five with cancer of diverse tissue origin and one with a premalignant neoplasm, showed a high frequency of chromatid aberrations, 94 to 119 breaks and 58 to 95 gaps per 100 metaphase cells arrested with colcemid 0.5 to 1.5 h after X irradiation (1.75 x 10(-2) C/kg). This response results from deficient repair of the radiation-induced DNA damage. In contrast, skin fibroblasts from two unrelated normal controls and a spouse showed 19 breaks and 17 to 19 gaps per 100 cells. Whereas all six members of the cancer-prone family had a radioresistant phenotype, only four had an inherited p53 mutation. Fibroblasts from a radioresistant family member showed the same extent of chromatid damage directly (0 to 0.5 h) after G2-phase X irradiation as those from the radiosensitive control spouse. We conclude, therefore, that radiosensitivity, as determined by cell killing in asynchronous populations of skin fibroblasts, is unrelated to chromosomal sensitivity to G2-phase X irradiation. However, the persistence of a high frequency of chromatid breaks and gaps at 0.5 to 1.5 h after G2-phase X irradiation, a manifestation of deficient DNA repair, is associated with proneness to cancer in this family.

Oncogene- transformed NIH 3T3 cells display radiation resistance levels indicative of a signal transduction pathway leading to the radiation-resistant phenotype

Oncogenes and their normal counterparts, proto-oncogenes, are functionally important cellular genes which interact with one another as components of signal transduction pathways leading to cell growth and differentiation. Numerous reports in the literature have also begun to link these genes to the phenomenon of cellular radiation resistance. In this report we examine the radiation resistance level of NIH 3T3 cells transformed by various oncogenes in an attempt to define the intracellular pathway to the radiation-resistant phenotype. The results demonstrate that an analogous signaling pathway is apparently involved in acquisition of radiation resistance. Serine/threonine protein kinase oncogenes such as raf, mos, and PKC play a central role in the pathway. Moreover, specific oncogenes upstream (sis, HER-2, met, trk, and ras) and downstream (ets and myc) of these important signaling mediators can also influence the radiation resistance level of the cells.