Pre-targeting and direct immunotargeting of liposomal drug carriers to ovarian carcinoma

Background

Epidermal growth factor receptor (EGFR) is overexpressed in many solid tumor types, such as ovarian carcinoma. Immunoliposome based drug targeting has shown promising results in drug delivery to the tumors. However, the ratio of tumor-to-normal tissue concentrations should be increased to minimize the adverse effects of cytostatic drugs.

Methodology/Principal Findings

We studied the EGFR-targeted doxorubicin immunoliposomes using pre-targeting and local intraperitoneal (i.p.) administration of the liposomes. This approach was used to increase drug delivery to tumors as compared to direct intravenous (i.v.) administration of liposomes. EGFR antibodies were attached on the surface of PEG coated liposomes using biotin-neutravidin binding. Receptor mediated cellular uptake and cytotoxic efficacy of EGFR-targeted liposomes were investigated in human ovarian adenocarcinoma (SKOV-3 and SKOV3.ip1) cells. In vivo distribution of the liposomes in mice was explored using direct and pre-targeting approaches and SPECT/CT imaging. Targeted liposomes showed efficient and specific receptor-mediated binding to ovarian carcinoma cells in vitro, but the difference in cytotoxicity between targeted and non-targeted liposomes remained small. The relatively low cytotoxic efficacy is probably due to insufficient doxorubicin release from the liposomes rather than lack of target binding. Tumor uptake of targeted liposomes in vivo was comparable to that of non-targeted liposomes after both direct and pre-targeting administration. For both EGFR-targeted and non-targeted liposomes, the i.p. administration increased liposome accumulation to the tumors compared to i.v. injections.

Conclusions/Significance

Intraperitoneal administration of liposomes may be a beneficial approach to treat the tumors in the abdominal cavity. The i.p. pre-targeting method warrants further studies as a potential approach in cancer therapy.     

Low Dose Focused Ultrasound Induces Enhanced Tumor Accumulation of Natural Killer Cells

Natural killer (NK) cells play a vital antitumor role as part of the innate immune system. Efficacy of adoptive transfer of NK cells depends on their ability to recognize and target tumors. We investigated whether low dose focused ultrasound with microbubbles (ldbFUS) could facilitate the targeting and accumulation of NK cells in a mouse xenograft of human colorectal adenocarcinoma (carcinoembryonic antigen (CEA)-expressing LS-174T implanted in NOD.Cg-Prkdc^scidIl2rg^tm1Wjl/SzJ (NSG) mice) in the presence of an anti-CEA immunocytokine (ICK), hT84.66/M5A-IL-2 (M5A-IL-2). Human NK cells were labeled with an FDA-approved ultra-small superparamagnetic iron oxide particle, ferumoxytol. Simultaneous with the intravenous injection of microbubbles, focused ultrasound was applied to the tumor. In vivo longitudinal magnetic resonance imaging (MRI) identified enhanced accumulation of NK cells in the ensonified tumor, which was validated by endpoint histology. Significant accumulation of NK cells was observed up to 24 hrs at the tumor site when ensonified with 0.50 MPa peak acoustic pressure ldbFUS, whereas tumors treated with at 0.25 MPa showed no detectable NK cell accumulation. These clinically translatable results show that ldbFUS of the tumor mass can potentiate tumor homing of NK cells that can be evaluated non-invasively using MRI.     

Peptide-Mediated Liposomal Doxorubicin Enhances Drug Delivery Efficiency and Therapeutic Efficacy in Animal Models

Lung cancer ranks among the most common malignancies, and is the leading cause of cancer-related mortality worldwide. Chemotherapy for lung cancer can be made more specific to tumor cells, and less toxic to normal tissues, through the use of ligand-mediated drug delivery systems. In this study, we investigated the targeting mechanism of the ligand-mediated drug delivery system using a peptide, SP5-2, which specifically binds to non-small cell lung cancer (NSCLC) cells. Conjugation of SP5-2 to liposomes enhanced the amount of drug delivered directly into NSCLC cells, through receptor-mediated endocytosis. Functional SP5-2 improved the therapeutic index of Lipo-Dox by enhancing therapeutic efficacy, reducing side effects, and increasing the survival rate of tumor-bearing mice in syngenic, metastatic and orthotopic animal models. Accumulation of SP5-2-conjugated liposomal doxorubicin (SP5-2-LD) in tumor tissues was 11.2-fold higher than that of free doxorubicin, and the area under the concentration-time curve (AUC_{0–72 hours}) was increased 159.2-fold. Furthermore, the experiment of bioavailability was assessed to confirm that SP5-2 elevates the uptake of the liposomal drugs by the tumor cells in vivo. In conclusion, the use of SP5-2-conjugated liposomes enhances pharmacokinetic properties, improves efficacy and safety profiles, and allows for controlled biodistribution and drug release.     

Liposome-aided metabolic engineering of tumor surface immunogenicity

Approaches to increase tumor immunogenicity are of therapeutic potentials. We herein reported the use of liposomes for covalent incorporation of neoantigen on tumor surfaces with DNP-conjugated sialic acid (^DNPSia). Relative to free ^DNPSia, sugar-encapsulated biotinylated liposomes (^DNPSia@LP@biotin) enables effective cell surface expression of ^DNPSia on biotin receptor (BR)-expressing cells over BR-free cells in vitro, and on tumor cell surfaces with high tumor-to-normal tissue contrast in a mice model. These findings suggest the potentials of targetable liposomes for modulating tumor surface immunity via metabolic oligosaccharide engineering.     

Ex Vivo and In Vivo Imaging and Biodistribution of Aptamers Targeting the Human Matrix MetalloProtease-9 in Melanomas

The human Matrix MetalloProtease-9 (hMMP-9) is overexpressed in tumors where it promotes the release of cancer cells thus contributing to tumor metastasis. We raised aptamers against hMMP-9, which constitutes a validated marker of malignant tumors, in order to design probes for imaging tumors in human beings. A chemically modified RNA aptamer (F3B), fully resistant to nucleases was previously described. This compound was subsequently used for the preparation of F3B-Cy5, F3B-S-acetylmercaptoacetyltriglycine (MAG) and F3B-DOTA. The binding properties of these derivatives were determined by surface plasmon resonance and electrophoretic mobility shift assay. Optical fluorescence imaging confirmed the binding to hMMP-9 in A375 melanoma bearing mice. Quantitative biodistribution studies were performed at 30 min, 1h and 2 h post injection of ^99mTc-MAG-aptamer and ¹¹¹In-DOTA-F3B. ^99mTc radiolabeled aptamer specifically detected hMMP-9 in A375 melanoma tumors but accumulation in digestive tract was very high. Following i.v. injection of ¹¹¹In-DOTA-F3B, high level of radioactivity was observed in kidneys and bladder but digestive tract uptake was very limited. Tumor uptake was significantly (student t test, p<0.05) higher for ¹¹¹In-DOTA-F3B with 2.0%ID/g than for the ¹¹¹In-DOTA-control oligonucleotide (0.7%ID/g) with tumor to muscle ratio of 4.0. Such difference in tumor accumulation has been confirmed by ex vivo scintigraphic images performed at 1h post injection and by autoradiography, which revealed the overexpression of hMMP-9 in sections of human melanomas. These results demonstrate that F3B aptamer is of interest for detecting hMMP-9 in melanoma tumor.     

Inhibition and eradication of human glioma with tumor-targeting Salmonella typhimurium in an orthotopic nude-mouse model

Malignant glioma tumors are the most common primary central nervous system tumors. Despite the multidisciplinary approach to treatment, prognosis remains poor. In this study, we demonstrated that the Salmonella typhimurium A1-R tumor-targeting strain can inhibit and eradicate human glioma in an orthotopic nude-mouse model. S. typhimurium A1-R was administered by injection through a craniotomy open-window or intravenously in nude mice. To establish the model, 2 × 10⁵ U87-RFP human glioma cells were injected stereotactically into the mouse brain through the craniotomy open window. Two weeks after glioma-cell implantation, mice were treated with S. typhimurium A1-R [2 × 10⁷ CFU/200 µl intravenous injection (i.v.) or 1 × 10⁶ CFU/1 µl intracranial injection (i.c.)] once a week for 3 weeks. Brain tumors were observed by fluorescence imaging through the craniotomy open window over time. S. typhimurium A1-R, administered i.c., inhibited brain tumor growth 7.6-fold compared with untreated mice (p = 0.009) and improved survival 73% (p = 0.001). Two of ten mice appeared to have their tumors eradicated. Intravenous administration of S. typhimurium A1-R was not effective. The craniotomy open window enabled observation of tumor growth in the brain in real time in both treated and untreated mice. The results of the present study demonstrate that bacterial therapy of brain cancer is a novel, effective and safe treatment strategy in a highly treatment-resistance cancer.Key words: Salmonella typhimurium A1-R, fluorescent proteins, brain cancer, mouse model, in vivo imaging     

Nanodrug-Enhanced Radiofrequency Tumor Ablation: Effect of Micellar or Liposomal Carrier on Drug Delivery and Treatment Efficacy

Purpose

To determine the effect of different drug-loaded nanocarriers (micelles and liposomes) on delivery and treatment efficacy for radiofrequency ablation (RFA) combined with nanodrugs.

Materials/Methods

Fischer 344 rats were used (n = 196). First, single subcutaneous R3230 tumors or normal liver underwent RFA followed by immediate administration of IV fluorescent beads (20, 100, and 500 nm), with fluorescent intensity measured at 4–24 hr. Next, to study carrier type on drug efficiency, RFA was combined with micellar (20 nm) or liposomal (100 nm) preparations of doxorubicin (Dox; targeting HIF-1α) or quercetin (Qu; targeting HSP70). Animals received RFA alone, RFA with Lipo-Dox or Mic-Dox (1 mg IV, 15 min post-RFA), and RFA with Lipo-Qu or Mic-Qu given 24 hr pre- or 15 min post-RFA (0.3 mg IV). Tumor coagulation and HIF-1α orHSP70 expression were assessed 24 hr post-RFA. Third, the effect of RFA combined with IV Lipo-Dox, Mic-Dox, Lipo-Qu, or Mic-Qu (15 min post-RFA) compared to RFA alone on tumor growth and animal endpoint survival was evaluated. Finally, drug uptake was compared between RFA/Lipo-Dox and RFA/Mic-Dox at 4–72 hr.

Results

Smaller 20 nm beads had greater deposition and deeper tissue penetration in both tumor (100 nm/500 nm) and liver (100 nm) (p<0.05). Mic-Dox and Mic-Qu suppressed periablational HIF-1α or HSP70 rim thickness more than liposomal preparations (p<0.05). RFA/Mic-Dox had greater early (4 hr) intratumoral doxorubicin, but RFA/Lipo-Dox had progressively higher intratumoral doxorubicin at 24–72 hr post-RFA (p<0.04). No difference in tumor growth and survival was seen between RFA/Lipo-Qu and RFA/Mic-Qu. Yet, RFA/Lipo-Dox led to greater animal endpoint survival compared to RFA/Mic-Dox (p<0.03).

Conclusion

With RF ablation, smaller particle micelles have superior penetration and more effective local molecular modulation. However, larger long-circulating liposomal carriers can result in greater intratumoral drug accumulation over time and reduced tumor growth. Accordingly, different carriers provide specific advantages, which should be considered when formulating optimal combination therapies.     

Imaging of rats with mammary cancer with two 2-deoxy-2-[18F]fluoro-d-hexoses

Rats with mammary cancer were imaged by scintigraphy: 10 rats with 2-deoxy-2-[¹⁸F]fluoro-d-glucose ([¹⁸F]FDG) and 10 rats with [¹⁸F]F-d-galactose. The uptake of both tracers was similar in the tumors—the tumor-to-normal tissue ratio was 2.7 ± 1.1 for [¹⁸F]FDG and 2.3 ± 0.9 for [¹⁸F]FDGal at 120 min after injection. In addition to the tumors [¹⁸F]FDG accumulated in the brain, bladder and heart, [¹⁸F]FDGal in the brain, bladder and liver. [¹⁸F]FDGal may be useful for tumor imaging in man; further studies should be addressed to elucidate the mechanism of [¹⁸F]FDGal uptake into tumors.     

A New Brain Drug Delivery Strategy: Focused Ultrasound-Enhanced Intranasal Drug Delivery

Central nervous system (CNS) diseases are difficult to treat because of the blood-brain barrier (BBB), which prevents most drugs from entering into the brain. Intranasal (IN) administration is a promising approach for drug delivery to the brain, bypassing the BBB; however, its application has been restricted to particularly potent substances and it does not offer localized delivery to specific brain sites. Focused ultrasound (FUS) in combination with microbubbles can deliver drugs to the brain at targeted locations. The present study proposed to combine these two different platform techniques (FUS+IN) for enhancing the delivery efficiency of intranasally administered drugs at a targeted location. After IN administration of 40 kDa fluorescently-labeled dextran as the model drug, FUS targeted at one region within the caudate putamen of mouse brains was applied in the presence of systemically administered microbubbles. To compare with the conventional FUS technique, in which intravenous (IV) drug injection is employed, FUS was also applied after IV injection of the same amount of dextran in another group of mice. Dextran delivery outcomes were evaluated using fluorescence imaging of brain slices. The results showed that FUS+IN enhanced drug delivery within the targeted region compared with that achieved by IN only. Despite the fact that the IN route has limited drug absorption across the nasal mucosa, the delivery efficiency of FUS+IN was not significantly different from that of FUS+IV. As a new drug delivery platform, the FUS+IN technique is potentially useful for treating CNS diseases.     

Evaluation of Efficacy of Radioimmunotherapy with 90Y-Labeled Fully Human Anti-Transferrin Receptor Monoclonal Antibody in Pancreatic Cancer Mouse Models

Objective

Pancreatic cancer is an aggressive tumor and the prognosis remains poor. Therefore, development of more effective therapy is needed. We previously reported that ⁸⁹Zr-labeled TSP-A01, an antibody against transferrin receptor (TfR), is highly accumulated in a pancreatic cancer xenograft, but not in major normal organs. In the present study, we evaluated the efficacy of radioimmunotherapy (RIT) with ⁹⁰Y-TSP-A01 in pancreatic cancer mouse models.

Methods

TfR expression in pancreatic cancer cell lines (AsPC-1, BxPC-3, MIAPaCa-2) was evaluated by immunofluorescence staining. ¹¹¹In-labeled anti-TfR antibodies (TSP-A01, TSP-A02) were evaluated in vitro by cell binding assay with the three cell lines and by competitive inhibition assay with MIAPaCa-2. In vivo biodistribution was evaluated in mice bearing BxPC-3 and MIAPaCa-2 xenografts. Tumor volumes of BxPC-3 and MIAPaCa-2 were sequentially measured after ⁹⁰Y-TSP-A01 injection and histological analysis of tumors was conducted.

Results

MIAPaCa-2 cells showed the highest TfR expression, followed by AsPC-1 and BxPC-3 cells. ¹¹¹In-TSP-A01 and ¹¹¹In-TSP-A02 bound specifically to the three cell lines according to TfR expression. The dissociation constants for TSP-A01, DOTA-TSP-A01, TSP-A02, and DOTA-TSP-A02 were 0.22, 0.28, 0.17, and 0.22 nM, respectively. ¹¹¹In-TSP-A01 was highly accumulated in tumors, especially in MIAPaCa-2, but this was not true of ¹¹¹In-TSP-A02. The absorbed dose for ⁹⁰Y-TSP-A01 was estimated to be 8.3 Gy/MBq to BxPC-3 and 12.4 Gy/MBq to MIAPaCa-2. MIAPaCa-2 tumors treated with 3.7 MBq of ⁹⁰Y-TSP-A01 had almost completely disappeared around 3 weeks after injection and regrowth was not observed. Growth of BxPC-3 tumors was inhibited by 3.7 MBq of ⁹⁰Y-TSP-A01, but the tumor size was not reduced.

Conclusion

⁹⁰Y-TSP-A01 treatment achieved an almost complete response in MIAPaCa-2 tumors, whereas it merely inhibited the growth of BxPC-3 tumors. ⁹⁰Y-TSP-A01 is a promising RIT agent for pancreatic cancer, although further investigation is necessary to improve the efficacy for the radioresistant types like BxPC-3.     

Monoclonal antibody 2C5-modified doxorubicin-loaded liposomes with significantly enhanced therapeutic activity against intracranial human brain U-87 MG tumor xenografts in nude mice

Liposomes, modified with monoclonal antibodies, are suitable carriers for targeted delivery of chemotherapeutic drugs into brain tumors. Here, we investigate the therapeutic efficacy of monoclonal anticancer antibody 2C5-modified long-circulating liposomes (LCL) loaded with doxorubicin (2C5-DoxLCL) for the treatment of U-87 MG human brain tumors in an intracranial model in nude mice. In vitro, 2C5-DoxLCL is significantly more effective in killing the U-87 MG tumor cells than Doxil (commercial doxorubicin-loaded PEGylated LCL) or DoxLCL modified with a non-specific IgG. 2C5-immunoliposomes also demonstrate a significantly higher accumulation in U-87 MG tumors compared to all controls in a subcutaneous model. The treatment of intracranial U-87 MG brain tumors in nude mice with 2C5-DoxLCL provides a significant therapeutic benefit over control formulations, substantially reducing the tumor size and almost doubling the survival time. Thus, monoclonal antibody 2C5-modified LCL can specifically target the anticancer drugs to brain tumors, leading to improved therapeutic treatment of brain tumor in an intracranial model, in vivo.     

Synthesis of an amphiphilic tetrazine derivative and its application as a liposomal component to accelerate release of encapsulated drugs

Tetrazine irreversibly reacts with dienophiles, and its derivatives find wide applications in the fields of biochemistry and biophysics. We have synthesized an amphiphilic tetrazine derivative (2-hexadecyl-N-(6-(6-(pyridin-2-yl)-1,2,4,5-tetrazine-3-yl)pyridin-3-yl)octadecanamide; 1), which has a hydrophilic tetrazine structure and hydrophobic alkyl chains. Liposomes composed of compound 1 and 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) (PTz-liposome) were prepared. In search of a new drug delivery system (DDS), we investigated the viability of inverse electron-demand Diels-Alder, a reaction between tetrazine and 2-norbornene, on the surface of the liposomes to change membrane fluidity and promote spatial and temporal controlled release of the encapsulated drugs. Compound 1 was synthesized with a yield of 71%. MS analysis after incubation of 2-norbornene with PTz-liposome revealed the binding of 2-norbornene to tetrazine. Indium-111-labeled diethylenetriaminepentaacetic acid (¹¹¹In-DTPA) was encapsulated inside PTz-liposome to evaluate the leakage of free ¹¹¹In-DTPA from the liposomes quantitatively. After 24 h of adding 2-norbornene, the release percentage for PTz-liposome was significantly higher than that for the control liposome (without tetrazine structure). Furthermore, the membrane fluidity of the PTz-liposome was increased by adding 2-norbornene. These results suggested that the combination of dienophile and liposome containing a newly synthesized tetrazine derivative can be used as a controlled release DDS carrier.     

Inducing Controlled Release and Increased Tumor-Targeted Delivery of Chlorambucil via Albumin/Liposome Hybrid Nanoparticles

Liposomes possess good biocompatibility and excellent tumor-targeting capacity. However, the rapid premature release of lipophilic drugs from the lipid bilayer of liposomes has negative effect on the tumor-targeted drug delivery of liposomes. In this study, a lipophilic antitumor drug—chlorambucil (CHL)—was encapsulated into the aqueous interior of liposomes with the aid of albumin to obtain the CHL-loaded liposomes/albumin hybrid nanoparticles (CHL-Hybrids). The in vitro accumulative release rate of CHL from CHL-Hybrids was less than 50% within 48 h, while the accumulative CHL release was more than 80% for CHL-loaded liposomes (CHL-Lip). After intravenous injection into rats, the half-life (t _1/2β = 5.68 h) and maximum blood concentration (C _max = 4.58 μg/mL) of CHL-Hybrids were respectively 1.1 times and 3.5 times higher than that of CHL-Lip. In addition, CHL-Hybrids had better tumor-targeting capacity for it significantly increased the drug accumulation in B16F10 tumors, which contributed to the significantly control of tumor growth compared with CHL-Lip. Furthermore, CHL-Hybrid-treated B16F10 melanoma-bearing mice displayed the longest median survival time of 30.0 days among all the treated groups. Our results illustrated that the proposed hybrids drug delivery system would be a promising strategy to maintain the controlled release of lipophilic antitumor drugs from liposomes and simultaneously facilitate the tumor-targeted drug delivery.     

Targeting of Drugs to Solid Tumors Using Anti-Her2 Immunoliposomes

Abstract

Cancer therapy would clearly benefit from a carrier system capable of intracellular delivery of systemically administered drugs to cancer cells in solid tumors. Sterically stabilized immunoliposomes specific to the cells expressing HER2 protooncogene (anti-HER2 SIL), were designed by conjugating Fab’ fragments of a recombinant humanized anti-HER2 MAb to the distal termini of poly(ethylene glycol) chains on the surface of unilamellar liposomes (size 90–100 nm) of phosphatidylcholine, cholesterol, and poly (ethylene glycol)—derivatized phosphatidylethanolamine. Anti-HER2 SIL avidly and specifically bound to cultured HER2-overexpressing cancer cells (8,000–23,000 vesicles per cell) and became endocytosed (k_e = 0.022–0.033 min.^?1) via the coated pit pathway. Anti-HER2 SIL showed prolonged circulation lifetime in rats (blood MRT approx. 24 hours) and significantly increased antitumor activity of encapsulated doxorubicin against HER2-overexpressing human breast cancer xenografts in nude mice. Although the accumulation of anti-HER2 SIL in HER2-overexpressing tumor xenografts was not increased over that of non-targeted sterically stabilized liposomes (SL), microscopic examination revealed abundance of anti-HER2 SIL in the interstitial spaces, as well as within the cytoplasm of cancer cells, while identical liposomes lacking anti-HER2 Fab’ were located predominantly within tumor-resident macrophages. Anti-HER2 SIL, a targeted vehicle capable of in vivo intracellular delivery of substances to HER2-overexpressing solid cancers, enhances the potential for tumor targeting and opens new avenues for better treatment of cancer.     

Therapeutic Efficacy of Combining PEGylated Liposomal Doxorubicin and Radiofrequency (RF) Ablation: Comparison between Slow-Drug-Releasing,Non-Thermosensitive and Fast-Drug-Releasing,Thermosensitive Nano-Liposomes

Aims

To determine how the accumulation of drug in mice bearing an extra-hepatic tumor and its therapeutic efficacy are affected by the type of PEGylated liposomal doxorubicin used, treatment modality, and rate of drug release from the liposomes, when combined with radiofrequency (RF) ablation.

Materials and Methods

Two nano-drugs, both long-circulating PEGylated doxorubicin liposomes, were formulated: (1) PEGylated doxorubicin in thermosensitive liposomes (PLDTS), having a burst-type fast drug release above the liposomes’ solid ordered to liquid disordered phase transition (at 42°C), and (2) non-thermosensitive PEGylated doxorubicin liposomes (PLDs), having a slow and continuous drug release. Both were administered intravenously at 8 mg/kg doxorubicin dose to tumor-bearing mice. Animals were divided into 6 groups: no treatment, PLD, RF, RF+PLD, PLDTS, and PLDTS+RF, for intra-tumor doxorubicin deposition at 1, 24, and 72 h post-injection (in total 41, mice), and 31 mice were used for randomized survival studies.

Results

Non-thermosensitive PLD combined with RF had the least tumor growth and the best end-point survival, better than PLDTS+RF (p<0.005) or all individual therapies (p<0.001). Although at 1 h post-treatment the greatest amount of intra-tumoral doxorubicin was seen following PLDTS+RF (p<0.05), by 24 and 72 h the greatest doxorubicin amount was seen for PLD+RF (p<0.05); in this group the tumor also has the longest exposure to doxorubicin.

Conclusion

Optimizing therapeutic efficacy of PLD requires a better understanding of the relationship between the effect of RF on tumor microenvironment and liposome drug release profile. If drug release is too fast, the benefit of changing the microenvironment by RF on tumor drug localization and therapeutic efficacy may be much smaller than for PLDs having slow and temperature-independent drug release. Thus the much longer circulation time of doxorubicin from PLD than from PLDTS may be beneficial in many therapeutic instances, especially in extra-hepatic tumors.     

Inhibition and eradication of human glioma with tumor-targeting Salmonella typhimurium in an orthotopic nude-mouse model

Malignant glioma tumors are the most common primary central nervous system tumors. Despite the multidisciplinary approach to treatment, prognosis remains poor. In this study, we demonstrated that the Salmonella typhimurium A1-R tumor-targeting strain can inhibit and eradicate human glioma in an orthotopic nude-mouse model. S. typhimurium A1-R was administered by injection through a craniotomy open-window or intravenously in nude mice. To establish the model, 2 x 105 U87-RFP human glioma cells were injected stereotactically into the mouse brain through the craniotomy open window. Two weeks after glioma-cell implantation, mice were treated with S. typhimurium A1-R [2 x 10⁷ CFU/200 μl intravenous injection (i.v.) or 1 x 10⁶ CFU/1 μl intracranial injection (i.c.)] once a week for 3 weeks. Brain tumors were observed by fluorescence imaging through the craniotomy open window over time. S. typhimurium A1-R, administered i.c., inhibited brain tumor growth 7.6-fold compared with untreated mice (p = 0.009) and improved survival 73% (p = 0.001). Two of ten mice appeared to have their tumors eradicated. Intravenous administration of S. typhimurium A1-R was not effective. The craniotomy open window enabled observation of tumor growth in the brain in real time in both treated and untreated mice. The results of the present study demonstrate that bacterial therapy of brain cancer is a novel, effective and safe treatment strategy in a highly treatment-resistance cancer.     

Use of liposomes as carriers for radiation synovectomy

Using [^99mTc]pertechnetate as an aqueous space marker, the permeability of liposomes composed of seven different mixtures of distearoylphosphatidylcholine (DSPC) and sphingomyelin (SM) was determined. Liposomes containing 20–33% SM were the least permeable in the presence of rheumatoid synovial fluid. Following injection of ^99mTc-containing liposomes into the knee joints of rabbits, retention of ^99mTc in the knee was more than 200 times greater than following injection of nonencapsulated [^99mTc]pertechnetate. The knee clearance biologic half time of ^99mTe with DSPC/SM (4:1) liposomes was 64 h. Most of the activity that had leaked from the knee was not found in extra-articular tissues, suggesting rapid excretion. When DSPC/SM (4:1) liposomes were labeled with ¹¹¹In(oxine), a knee clearance biologic half time of greater than 1200 h was observed.     

Formation of transition metal-doxorubicin complexes inside liposomes

Doxorubicin complexation with the transition metal manganese (Mn²⁺) has been characterized, differentiating between the formation of a doxorubicin-metal complex and doxorubicin fibrous-bundle aggregates typically generated following ion gradient-based loading procedures that rely on liposome encapsulated citrate or sulfate salts. The physical and chemical characteristics of the encapsulated drug were assessed using cryo-electron microscopy, circular dichroism (CD) and absorbance spectrophotometric analysis. In addition, in vitro and in vivo drug loading and release characteristics of the liposomal formulations were investigated. Finally, the internal pH after drug loading was measured with the aim of linking formation of the Mn²⁺ complex to the presence or absence of a transmembrane pH gradient. Doxorubicin was encapsulated into either 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/cholesterol (Chol) or 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)/Chol liposomes, where the entrapped salts were citrate, MnSO₄ or MnCl₂. In response to a pH gradient or a Mn²⁺ ion gradient, doxorubicin accumulated inside to achieve a drug-to-lipid ratio of approximately 0.2:1 (wt/wt). Absorbance and CD spectra of doxorubicin in the presence of Mn²⁺ suggested that there are two distinct structures captured within the liposomes. In the absence of added ionophore A23187, drug loading is initiated on the basis of an established pH gradient; however, efficient drug uptake is not dependent on maintenance of the pH gradient. Drug release from DMPC/Chol is comparable regardless of whether doxorubicin is entrapped as a citrate-based aggregate or a Mn²⁺ complex. However, in vivo drug release from DSPC/Chol liposomes indicate less than 5% or greater than 50% drug loss over a 24-h time course when the drug was encapsulated as an aggregate or a Mn²⁺ complex, respectively. These studies define a method for entrapping drugs possessing coordination sites capable of complexing transition metals and suggest that drug release is dependent on lipid composition, internal pH, as well as the nature of the crystalline precipitate, which forms following encapsulation.     

In vivo assessment of 111in-labeled hematoporphyrin derivative in breast tumor-bearing animals

The biological behavior of ¹¹¹In-labeled HPD has been investigated in tumor-bearing animals. Mice mammary adenocarcinomas and 7,12-dimethylbenz(a)anthracine induced breast tumors in Sprague-Dawley female rats were clearly visualized by ¹¹¹In-HPD nuclear scintigraphy. Optimal scans were obtained after a 48 h delay. In normal and tumor-bearing animals, the highest uptake of ¹¹¹In-HPD 72 h post-injection was found in the liver, the spleen and the kidneys. Depending on the size and the extent of necrosis, the uptake of ¹¹¹In-HPD by malignant breast tumors varied from 2.5% injected dose (ID) (range 0.14–5.3% ID) in mice to 1% ID (range 0.22–8.1% ID) in rats. Benign breast tumor uptake of ¹¹¹In-HPD was less that 1%ID. No significant amount of the radiopharmaceutical was found in pulmonary abscesses and abdominal cysts (< 0.1 % ID). Scintigrams of these infectious or inflammatory lesions were normal. Malignant tumor to blood, heart and lung ratios averaged 50:1, 10:1 and 3:1 respectively. Tumor to brain ratio ranged from 72 to 444:1.