Yi-Yu Lin

Therapeutic Efficacy Evaluation of 111In-Labeled PEGylated Liposomal Vinorelbine in Murine Colon Carcinoma with Multimodalities of Molecular Imaging

In our previous studies using combined radioisotopes with chemotherapeutic liposomal drugs (i.e., 111In-labeled polyethylene glycol (PEG)ylated liposomal vinorelbine) we have reported possible therapeutic efficiency in tumor growth suppression. Nevertheless, the challenge remains as to whether this chemotherapy has a therapeutic effect as good as that of combination therapy. The goal of this study was to investigate the real therapeutic effectiveness of 6 mol% PEG 111In-vinorelbine liposomes via the elevation of the radiation dosage and reduction in the concentration of chemotherapeutic agents. Methods: Murine colon carcinoma cells transfected with dual-reporter genes (CT-26/tk-luc) were xenografted into BALB/c mice. The biodistribution was estimated to determine the drug profile and targeting efficiency of 111In-vinorelbine liposomes. Bioluminescence imaging and 18F-FDG small-animal PET were applied to monitor the therapeutic response after drug administration. The survival in vivo was estimated and linked with the toxicologic and histopathologic analyses to determine the preclinical safety and feasibility of the nanomedicine. Results: Effective long-term circulation of radioactivity in the plasma was achieved by 6 mol% PEG 111In-vinorelbine liposomes, and this dose showed significantly lower uptake in the reticuloendothelial system than that of 0.9 mol% PEG 111In-vinorelbine liposomes. Selective tumor uptake was represented by cumulative deposition, and the maximum accumulation was at 48 h after injection. The combination therapy exhibited an additive effect for tumor growth suppression as tracked by caliper measurement, bioluminescence imaging, and small-animal PET. Furthermore, an improved survival rate and reduced tissue toxicity were closely correlated with the toxicologic and histopathologic results. Conclusion: The results demonstrated that the use of 6 mol% PEG 111In-vinorelbine liposomes for passively targeted tumor therapy displayed an additive effect with combined therapy, not only by prolonging the circulation rate because of a reduction in the phagocytic effect of the reticuloendothelial system but also by enhancing tumor uptake. Thus, this preclinical study suggests that 6 mol% PEG 111In-vinorelbine liposomes have the potential to increase the therapeutic index and reduce the toxicity of the passively nanotargeted chemoradiotherapies.

Evaluation of Pharmacokinetics of 111In-Labeled VNB-PEGylated Liposomes After Intraperitoneal and Intravenous Administration in a Tumor/Ascites Mouse Model

Nanoliposomes are important drug carriers that can passively target tumor sites by the enhanced permeability and retention (EPR) effect in neoplasm lesions. This study evaluated the biodistribution and pharmacokinetics of 111In-labeled vinorelbine (VNB)-encapsulated PEGylated liposomes (IVNBPL) after intraperitoneal (i.p.) and intravenous (i.v.) administration in a C26/tk-luc colon carcinoma ascites mouse model. IVNBPL was prepared by labeling VNB-encapsulated PEGylated liposomes with 111In-oxine. BALB/c mice were i.p. inoculated with 2 x 10(5) C26/tk-luc cells in 500 muL of phosphate-buffered saline. Peritoneal tumor lesions were confirmed by 124I-FIAU/micro-PET (positron emission tomography) and bioluminescence imaging. Ascites production was examined by ultrasound imaging on day 10 after tumor cell inoculation. The pharmacokinetics and biodistribution studies of IVNBPL in a tumor/ascites mouse model were conducted. The labeling efficiency was more than 90%. The in vitro stability in human plasma at 37 degrees C for 72 hours was 83% +/- 3.5%. For i.p. administration, the areas under curves (AUCs) of ascites and tumor were 6.78- and 1.70-fold higher, whereas the AUCs of normal tissues were lower than those via the i.v. route. This study demonstrates that i.p. administration is a better approach than i.v. injection for IVNBPL, when applied to the treatment of i.p. malignant disease in a tumor/ascites mouse model.

Evaluation of EGFR-targeted radioimmuno-gold-nanoparticles as a theranostic agent in a tumor animal model

This study evaluated the tumor targeting and therapeutic efficacy of a novel theranostic agent (131)I-labeled immuno-gold-nanoparticle ((131)I-C225-AuNPs-PEG) for high epidermal growth factor receptor (EGFR)-expressed A549 human lung cancer. Confocal microscopy demonstrated the specific uptake of C225-AuNPs-PEG in A549 cells. (131)I-C225-AuNPs-PEG induced a significant reduction in cell viability, which was not observed when incubated with AuNPs-PEG and C225-AuNPs-PEG. MicroSPECT/CT imaging of tumor-bearing mice after intravenous injection of (123)I-C225-AuNPs-PEG revealed significant radioactivity retention in tumor suggested that (131)I-labeled C225-conjugated radioimmuno-gold-nanoparticles may provide a new approach of targeted imaging and therapy towards high EGFR-expressed cancers.

Biological characterization of cetuximab-conjugated gold nanoparticles in a tumor animal model

Gold nanoparticles (AuNPs) are widely applied to the diagnosis and treatment of cancer and can be modified to contain target-specific ligands via gold-thiolate bonding. This study investigated the pharmacokinetics and microdistribution of antibody-mediated active targeting gold nanoparticles in mice with subcutaneous lung carcinoma. We conjugated AuNPs with cetuximab (C225), an antibody-targeting epidermal growth factor receptor (EGFR), and then labeled with In-111, which created EGFR-targeted AuNPs. In vitro studies showed that after a 2 h incubation, the uptake of C225-conjugated AuNPs in high EGFR-expression A549 cells was 14.9-fold higher than that of PEGylated AuNPs; furthermore, uptake was also higher at 3.8-fold when MCF7 cells with lower EGFR-expression were used. MicroSPECT/CT imaging and a biodistribution study conducted by using a A549 tumor xenograft mouse model provided evidence of elevated uptake of the C225-conjugated AuNPs into the tumor cells as a result of active targeting. Moreover, the microdistribution of PEGylated AuNPs revealed that a large portion of AuNPs remained in the tumor interstitium, whereas the C225-conjugated AuNPs displayed enhanced internalization via antibody-mediated endocytosis. Our findings suggest that the anti-EGFR antibody-conjugated AuNPs are likely to be a plausible nano-sized vehicle for drug delivery to EGFR-expressing tumors.

Tumor Burden Talks in Cancer Treatment with PEGylated Liposomal Drugs

Purpose PEGylated liposomes are important drug carriers that can passively target tumor by enhanced permeability and retention (EPR) effect in neoplasm lesions. This study demonstrated that tumor burden determines the tumor uptake, and also the tumor response, in cancer treatment with PEGylated liposomal drugs in a C26/tk-luc colon carcinoma-bearing mouse model. Methods Empty PEGylated liposomes (NanoX) and those encapsulated with VNB (NanoVNB) were labeled with In-111 to obtain InNanoX and InVNBL in high labeling yield and radiochemical purity (all >90%). BALB/c mice bearing either small (58.4±8.0 mm3) or large (102.4±22.0 mm3) C26/tk-luc tumors in the right dorsal flank were intravenously administered with NanoVNB, InNanoX, InVNBL, or NanoX as a control, every 7 days for 3 times. The therapeutic efficacy was evaluated by body weight loss, tumor growth inhibition (using calipers and bioluminescence imaging) and survival fraction. The scintigraphic imaging of tumor mouse was performed during and after treatment. Results The biodistribution study of InVNBL revealed a clear inverse correlation (r 2 = 0.9336) between the tumor uptake and the tumor mass ranged from 27.6 to 623.9 mg. All three liposomal drugs showed better therapeutic efficacy in small-tumor mice than in large-tumor mice. Tumor-bearing mice treated with InVNBL (a combination drug) showed the highest tumor growth inhibition rate and survival fraction compared to those treated with NanoVNB (chemodrug only) and InNanoX (radionuclide only). Specific tumor targeting and significantly increased tumor uptake after periodical treatment with InVNBL were evidenced by scintigraphic imaging, especially in mice bearing small tumors. Conclusion The significant differences in the outcomes of cancer treatment and molecular imaging between animals bearing small and large tumors revealed that tumor burden is a critical and discriminative factor in cancer therapy using PEGylated liposomal drugs.

A pharmacokinetics study of radiolabeled micelles of a poly(ethylene glycol)-block-poly(caprolactone) copolymer in a colon carcinoma-bearing mouse model.

A copolymer of poly(ethylene glycol)-b-poly(caprolactone) (PEG-PCL) was modified with a benzyl moiety and labeled with I-131. A micelle system, (131)I-benzyl-micelles, formed from (131)I-benzyl-PEG-PCL and PEG-PCL-PC, was created and used for in vitro characterization and in vivo evaluation. Administration of (131)I-benzyl-micelles to a colon carcinoma-bearing mouse model gives a 4.9-fold higher tumor-to-muscle ratio at 48 h post-injection than treatment with the unimer (131)I-benzyl-PEG-PCL. Scintigraphic imaging, biodistribution results and pharmacokinetical evaluation all demonstrated that (131)I-benzyl-micelles are a plausible radioactive surrogate for PEG-PCL copolymer micelles. Modifying the amphiphilic copolymer with a benzyl moiety and labeled it with iodine-131 should make possible the real-time and noninvasive evaluation of the pharmacokinetics of copolymer micelles in vivo.

Pharmacokinetics and Dosimetry of 111In/188Re-Labeled PEGylated Liposomal Drugs in Two Colon Carcinoma-Bearing Mouse Models

PEGylated liposomes are important drug carriers for nanomedicine cancer therapy. PEGylated liposomes can encapsulate radio- and chemo-drugs and passively target tumor sites via enhanced permeability and retention effect. This study estimated the pharmacokinetics and dosimetry after administration of radio-chemotherapeutics ((111)In-labeled vinorelbine [VNB]-encapsulated liposomes, InVNBL, and (188)Re-labeled doxorubicin [DXR]-encapsulated liposomes, ReDXRL) for radionuclide therapy in two colon carcinoma-bearing mouse models. A C26 colon carcinoma tumor/ascites mouse model and a subcutaneous solid tumor-bearing mouse model were employed. Biodistribution studies of InVNBL and ReDXRL after intraperitoneal administration in tumor/ascites-bearing mice (protocol A) and intravenous administration in subcutaneous solid tumor-bearing mice (protocol B) were performed. The radiation dose to normal tissues and tumors were calculated based on the results of distribution studies in mice, using the OLINDA/EXM program. The cumulated activities in most organs after administration of InVNBL in either the tumor/ascites-bearing mice (protocol A) or the subcutaneous solid tumor-bearing mice (protocol B) were higher than those of ReDXRL. Higher tumor-to-normal-tissues absorption dose ratios (T/NTs) were observed after administration of InVNBL than those of ReDXRL for protocol A. The T/NTs for the liver, spleen, and red marrow after injection of InVNBL for protocol B were similar to those of ReDXRL. The critical organ was found to be red marrow, and thus the red marrow absorption dose defined the recommended maximum administration activity of these liposomal drugs. Characterization of pharmacokinetics and dosimetry is needed to select the appropriate radiotherapeutics for specific tumor treatment applications. The results suggest that InVNBL is a promising therapeutic agent, which is as good as ReDXRL, in two mouse tumor models.