Tanyel Kiziltepe

Temporal targeting of tumour cells and neovasculature with a nanoscale delivery system.

In the continuing search for effective treatments for cancer, the emerging model is the combination of traditional chemotherapy with anti-angiogenesis agents that inhibit blood vessel growth. However, the implementation of this strategy has faced two major obstacles. First, the long-term shutdown of tumour blood vessels by the anti-angiogenesis agent can prevent the tumour from receiving a therapeutic concentration of the chemotherapy agent. Second, inhibiting blood supply drives the intra-tumoural accumulation of hypoxia-inducible factor-1α (HIF1-α); overexpression of HIF1-α is correlated with increased tumour invasiveness and resistance to chemotherapy. Here we report the disease-driven engineering of a drug delivery system, a ‘nanocell’, which overcomes these barriers unique to solid tumours. The nanocell comprises a nuclear nanoparticle within an extranuclear pegylated-lipid envelope, and is preferentially taken up by the tumour. The nanocell enables a temporal release of two drugs: the outer envelope first releases an anti-angiogenesis agent, causing a vascular shutdown; the inner nanoparticle, which is trapped inside the tumour, then releases a chemotherapy agent. This focal release within a tumour results in improved therapeutic index with reduced toxicity. The technology can be extended to additional agents, so as to target multiple signalling pathways or distinct tumour compartments, enabling the model of an ‘integrative’ approach in cancer therapy.

A dual-color fluorescence imaging-based system for the dissection of antiangiogenic and chemotherapeutic activity of molecules

We have developed a simple yet sensitive dual color fluorescence‐based technique for dissecting the tumor‐neovascularization relationship and evaluated the susceptibility of each component to therapeutic interventions. Green fluorescent protein (GFP)‐expressing melanoma cells were cocultured with endothelial cells on different three‐dimensional (3‐D) matrices and exposed to multiple growth factors and molecules with established anti‐angiogenic or anticancer activities. Cells were fixed and stained with propidium iodide, imaged using a confocal microscope, and stereologically analyzed. Three‐dimensionality of the system was tested by depth‐coding and pseudocolor 3‐D reconstruction in the z‐axis. Selective ablation of the tumor cells was affected by the anthracycline antibiotic doxorubicin. Treatment with vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) promoted the neovascular responses on matrigel and collagen‐1 matrices. VEGF‐induced angiogenesis was inhibited after treatment with combretastatin and thalidomide. In contrast, HGF exerted a protective effect against these anti‐angiogenics in a matrigel matrix. However, this effect was lost when the matrix was substituted with collagen, suggesting that the extracellular matrix impinges on cellular function, possibly through an Akt‐mediated mechanism. The VEGF‐receptor antagonist PTK787 also selectively ablated the VEGF‐induced angiogenic effect without inhibiting the HGF‐induced response, demonstrating the sensitivity of the system to detect modulation of distinct signal cascades. The current model encompasses the possibility of studying tumor‐angiogenesis‐matrix interaction on the same platform, expanding the rapid screening of novel molecules in a simulated clinicopathological setting.