The leaky, heterogeneous vasculature of human tumors prevents the even distribution of systemic drugs within cancer tissues. However, techniques for studying vascular delivery systems in vivo often require complex mammalian models and time-consuming, surgical protocols. The developing chicken embryo is a well-established model for human cancer that is easily accessible for tumor imaging. To assess this model for the in vivo analysis of tumor permeability, human tumors were grown on the chorioallantoic membrane (CAM), a thin vascular membrane which overlays the growing chick embryo. The real-time movement of small fluorescent dextrans through the tumor vasculature and surrounding tissues were used to measure vascular leak within tumor xenografts. Dextran extravasation within tumor sites was selectively enhanced an interleukin-2 (IL-2) peptide fragment or vascular endothelial growth factor (VEGF). VEGF treatment increased vascular leak in the tumor core relative to surrounding normal tissue and increased doxorubicin uptake in human tumor xenografts. This new system easily visualizes vascular permeability changes in vivo and suggests that vascular permeability may be manipulated to improve chemotherapeutic targeting to tumors.

BackgroundDiphtheria toxin (DT) has been utilized as a prospective anti-cancer agent for the targeted delivery of cytotoxic therapy to otherwise untreatable neoplasia. DT is an extremely potent toxin for which the entry of a single molecule into a cell can be lethal. DT has been targeted to cancer cells by deleting the cell receptor-binding domain and combining the remaining catalytic portion with targeting proteins that selectively bind to the surface of cancer cells. It has been assumed that “receptorless” DT cannot bind to and kill cells. In the present study, we report that “receptorless” recombinant DT385 is in fact cytotoxic to a variety of cancer cell lines.Methods In vitro cytotoxicity of DT385 was measured by cell proliferation, cell staining and apoptosis assays. For in vivo studies, the chick chorioallantoic membrane (CAM) system was used to evaluate the effect of DT385 on angiogenesis. The CAM and mouse model system was used to evaluate the effect of DT385 on HEp3 and Lewis lung carcinoma (LLC) tumor growth, respectively.ResultsOf 18 human cancer cell lines tested, 15 were affected by DT385 with IC50 ranging from 0.12–2.8 µM. Furthermore, high concentrations of DT385 failed to affect growth arrested cells. The cellular toxicity of DT385 was due to the inhibition of protein synthesis and induction of apoptosis. In vivo, DT385 diminished angiogenesis and decreased tumor growth in the CAM system, and inhibited the subcutaneous growth of LLC tumors in mice.ConclusionDT385 possesses anti-angiogenic and anti-tumor activity and may have potential as a therapeutic agent.

The use of rodent models to evaluate efficacy during testing is accompanied by significant economic and regulatory hurdles which compound the costs of screening for promising drug candidates. Vasopermeation Enhancement Agents (VEAs) are a new class of biologics that are designed to increase the uptake of cancer therapeutics at the tumor site by modifying vascular permeability in the tumor to increase the therapeutic index of co-administered drugs. To evaluate the efficacy of a panel of VEA clinical candidates, we compared the rodent Miles assay to an equivalent assay in the ex ovo chicken embryo model. Both model systems identified the same candidate (PVL 10) as the most active promoter of vasopermeation in non-tumor tissues. An ex ovo chicken embryo system was utilized to test each candidate VEA in two human tumor models at a range of concentrations. Vasopermeation activity due to VEA was dependent on tumor type, with HEp3 tumors displaying higher levels of vasopermeation than MDA-MB-435. One candidate (PVL 10) proved optimal for HEp3 tumors and another (PVL 2) for MDA-MB-435. The use of the ex ovo chicken embryo model provides a rapid and less costly alternative to the use of rodent models for preclinical screening of drug candidates.

Necrosis is induced by ischemic conditions within the core of many solid tumors. Using fluorescent fusion proteins, we provide in vivo evidence of histone trafficking among cancer cells in implanted tumors. In particular, the most abundant H1 isoform (H1.2) was found to be transported from necrotic tumor cells into surrounding viable cells where histones are selectively taken up by energy-dependent endocytosis. We propose that intercellular histone trafficking could function as a target for drug delivery. This concept was validated using an anti-histone antibody that was co-internalized with histones from dead cells into viable ones surrounding the necrotic regions of a tumor, where some of the most chemoresistant cells reside. These findings demonstrate that cellular translocation of conjugated drugs using anti-histone antibodies is a promising strategy for targeted drug delivery to chemoresistant tumors.

e21090 Background: Given the reported association between incisional procedures performed on cancer patients and subsequent increases in metastasis, as well as the established inverse relationship between metastasis and patient survival, this study establishes the extent to which incisional core needle biopsies (CNB) affects tumor growth and metastatic dissemination in two distinct breast cancer animal models. Methods: Using the chick embryo system (CES) and murine breast cancer model (MuBC)the impact of CNB on cancer metastases was evaluated. Human MDA-MB-231 and MDA-MB-435 cancer cells were used in the xenograft / CES, and murine 4T1 Breast cancer cells for the syngeneic MuBC . In each model, tumors were biopsied in half of the animals while the other half were left undisturbed (CES:n=40, MuBC:n=40). The impact of CNB on tumor growth, necrosis and metastases was assessed. Metastases levels in the CES was determined by quantitative PCR for human alu sequence DNA in chick tissue extracts. Metastatic burden in the MuBC model was evaluated by microscopic quantification of metastatic areas in sectioned and H-E stained mouse organs. Results: When biopsied and un-biopsied groups were compared, both models showed significant difference in pulmonary metastasis. MDA-MB-435 CES (p=0.025) and 4T1 MuBC (p=0.026). MDA-MB-231 CES showed no significant change in lung metastases in the CES but did however show increased Chorioallantoic Membrane (CAM) metastasis (p=0.018) and both cell lines showed statistically significant alteration in Liver metastasis, (MDA-MB-231 CES (p=0.006); MDA-MB-435 CES (p=0.004)). Interestingly only MDA-MB-435 (CES) tumor growth was significantly increased after CNB (p=0.002). Conclusions: These results offer the first experimental evidence that core needle biopsies result in an increased risk of metastatic dissemination and affect metastatic tropic behavior. They also reinforce the concept of a multi-step metastatic pathway and suggest involvement of extrinsic factors that influence the extravastion and intravasation steps. The clinical implications are considerable and follow-up studies examining potential mechanisms and countermeasures are urgently required