Therapy In Tumor-bearing Mice Research Articles

Abstract 4552: Pretargeted radioimmunoimaging and -therapy in tumor-bearing mice using a bioorthogonal reaction

Abstract A major challenge of radioimmunotherapy (RIT) of cancer is to enhance the nuclear radiation dose delivered to the tumor while minimizing the dose in healthy tissues. Monoclonal antibodies (mAb) circulate for a long time and only slowly accumulate in the tumor, which, when used for RIT, leads to dose-limiting side effects in healthy organs. This efficacy-limiting factor can be circumvented by pretargeting, which involves tumor targeting of a mAb followed by binding of a small radiolabeled probe to the tumor-bound mAb. The superior image contrast and the ability to administer higher (therapeutic) radiation doses compared to directly labeled mAbs is offset by the drawbacks of the current biological pretargeting systems, involving either immunogenicity issues or extensive re-engineering of the parent mAb. To address this, we designed a novel pretargeting approach based on the bio-orthogonal chemical inverse-electron-demand Diels Alder reaction, employing a trans-cyclooctene-conjugated mAb and a radiolabeled tetrazine derivative, and we evaluated the in vitro stability and reactivity, and tumor targeting in mice bearing colorectal xenografts. The in vitro stability and reactivity of 111In-labeled tetrazine and anti-TAG72 mAb CC49 functionalized with trans-cyclooctene (TCO) moieties through lysine residue conjugation were monitored in PBS, serum and blood. In vivo pretargeting was performed in LS174T-tumored mice using 125I-labeled CC49-TCO and 111In-labeled tetrazine and assessed by dual isotope biodistribution and SPECT imaging with a nanoSPECT/CT. When 111In-tetrazine was administered to mice 1 day after CC49-TCO, the chemically-tagged tumors reacted rapidly with 111In-tetrazine, resulting in pronounced radioactivity localization throughout the tumor and good tumor contrast, as demonstrated by SPECT/CT imaging of live mice 3 h post injection: 4.18%ID/g, tumor-to-muscle ratio (T/M)=13.1. In mice treated with unmodified CC49, the tumor could not be discriminated from the surrounding tissue (0.28 %ID/g, T/M=0.5). Mice treated with TCO-modified rituximab, which lacks specificity for TAG72, showed the expected retention of 111In-tetrazine in blood and non-target organs, and a much reduced tumor accumulation (1.02 %ID/g, T/M=2.1). Corresponding biodistribution experiments revealed a remarkable 52-57% reaction yield between TCO and tetrazine moieties present in tumor and blood. We have demonstrated the first use of a chemical reaction between two exogenous moieties in living animals for the non-invasive imaging of low-abundance targets in clinically relevant conditions. The inverse-electron-demand Diels Alder reaction has the potential to improve the state of the art of pretargeted RIT and can be applied to a range of antibodies due to its universal and straightforward conjugation chemistry. The validation for pre-targeted RIT in LS174T-tumored mice is underway. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. 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 4552.

Zinc phthalocyanine-loaded PLGA biodegradable nanoparticles for photodynamic therapy in tumor-bearing mice

Nanoparticles formulated from the biodegradable copolymer poly(lactic-coglycolic acid) (PLGA) were investigated as a drug delivery system to enhance tissue uptake, permeation, and targeting of zinc(II) phthalocyanine (ZnPc) for photodynamic therapy. Three ZnPc nanoparticle formulations were prepared using a solvent emulsion evaporation method and the influence of sonication time on nanoparticle shape, encapsulation and size distribution, in vitro release, and in vivo photodynamic efficiency in tumor-bearing mice were studied. Sonication time did not affect the process yield or encapsulation efficiency, but did affect significantly the particle size. Sonication for 20 min reduced the mean particle size to 374.3 nm and the in vitro release studies demonstrated a controlled release profile of ZnPc. Tumor-bearing mice injected with ZnPc nanoparticles exhibited significantly smaller mean tumor volume, increased tumor growth delay and longer survival compared with the control group and the group injected with free ZnPc during the time course of the experiment. Histopathological examination of tumor from animals treated with PLGA ZnPc showed regression of tumor cells, in contrast to those obtained from animals treated with free ZnPc. The results indicate that ZnPc encapsulated in PLGA nanoparticles is a successful delivery system for improving photodynamic activity in the target tissue.

Inhibition of matrix metalloproteinases blocks lethal hepatitis and apoptosis induced by tumor necrosis factor and allows safe antitumor therapy.

Acute and fulminant liver failure induced by viral hepatitis, alcohol or other hepatotoxic drugs, are associated with tumor necrosis factor (TNF) production. In a mouse model of lethal hepatitis induced by TNF, apoptosis and necrosis of hepatocytes, but also lethality, hypothermia and influx of leukocytes into the liver, are prevented by a broad-spectrum matrix metalloproteinase (MMP) inhibitor, BB-94. Mice deficient in MMP-2, MMP-3 or MMP-9 had lower levels of apoptosis and necrosis of hepatocytes, and better survival. We found induction of MMP-9 activity and fibronectin degradation. Our findings suggest that several MMPs play a critical role in acute, fulminant hepatitis by degrading the extracellular matrix and allowing massive leukocyte influx in the liver. BB-94 also prevented lethality in TNF/interferon-gamma therapy in tumor-bearing mice. A broad-spectrum MMP inhibitor may be potentially useful for the treatment of patients with acute and perhaps chronic liver failure, and in cancer therapies using inflammatory cytokines.