Rimona Margalit

The frequent overexpression of the hyaluronan receptors CD44 and RHAMM in cancer cells opens the door for targeting by the naturally-occurring high-M(r) hyaluronan. This is the first time effective in vivo tumor targeting is reported for mitomycin C (MMC) loaded inside nano-sized hyaluronan-liposomes (denoted tHA-LIP). The severe adverse effects of free MMC made it a rational candidate for an effective targeted carrier. In vitro, loading MMC inside tHA-LIP increased drug potency 100-fold, in cells overexpressing, but not in cells underexpressing, hyaluronan receptors. Both types of liposomes were non-toxic and reduced MMC-related toxicity in healthy C57BL/6 mice. In 3 tumor models, BALB/c bearing C-26 solid tumors; C57BL/6 bearing B16F10.9 or (separately) D122 lung metastasis, tHA-LIP were long-circulating, 7-fold and 70-fold longer than nt-LIP and free MMC, respectively. tHA-LIP-mediated MMC accumulation in tumor-bearing lungs was 20% of injected dose, compared to 0.6% and 4% with free drug and nt-LIP, respectively. Tumor-free lungs showed low accumulation, irrespective of drug formulation. Key indicators of therapeutic responses, tumor progression, metastatic burden and survival, were superior (p < 0.001) in animals receiving MMC-loaded tHA-LIP, no treatment, MMC-loaded nt-LIP and free drug. In conclusion, tHA-LIP perform as tumor-targeted carriers, with promising prospects for treatment of tumors overexpressing hyaluronan receptors.

Naturally occurring high-Mr hyaluronan, bound to the surface of nanoliposomes (denoted targeted hyaluronan liposomes, or tHA-LIP), is a candidate for active targeting to tumors, many of which overexpress the hyaluronan receptors CD44 and RHAMM. The surface-bound hyaluronan also provides a hydrophilic coat that, similar to polyethylene glycol, may promote long-term circulation. We recently reported the successful targeting of mitomycin C, mediated by tHA-LIP, in tumor-bearing syngeneic mice. Hypothesizing that this targeting is carrier-specific, rather than drug-specific, we report here studies with doxorubicin (DXR)-loaded tHA-LIP, in syngeneic and human xenograft models. Saline, free DXR, DXR-loaded nontargeted liposomes (nt-LIP), and Doxil served as controls. The tHA-LIP were long-circulating, more than all controls, in healthy and tumor-bearing (C57BL/6/B16F10.9; BALB/c/C-26) mice. Mediated by tHA-LIP, DXR accumulation in tumor-bearing lungs was 30-, 6.7-, and 3.5-fold higher than free DXR, nt-LIP, and Doxil, respectively. Key indicators of therapeutic responses--tumor progression, metastatic burden, and survival--were superior (P < .001) in animals receiving DXR-loaded tHA-LIP compared with controls, in tumor-bearing syngeneic mice (BDF1/P388/ADR ascites, C57BL/6/B16F10.9 lung metastasis, and BALB/c/C-26 solid tumors), and in nude mice bearing PANC-1 solid tumors. In conclusion, tHA-LIP, performing as tumor-targeted carriers, have the potential to join the arsenal of carrier-formulated anticancer drugs.

The standard redox potential at I = 0.01, 25°C and pH 7.0 has been determined for the following species of cytochrome c : horse heart, baker's yeast isoenzyme‐1, Candida species yeast, tuna heart and turkey heart. The thermodynamic parameters of the redox reaction were evaluated and found to be identical, within experimental error, in the five species investigated. The effect of pH on the standard redox potential of horse heart cytochrome c was studied in the pH range 7.0–11.2. A single heme‐linked ionization of the oxidized protein was observed in this pH range, with a dissociation constant of 3 × 10 −9 at I = 0 and 25°C. The effects of the electrostatic media on the standard redox potential of horse heart cytochrome c depend on the nature of the anions employed. For non‐binding medium at 25°C, the observed potential dependence on the ionic strength is given by the equation: E 0 obs = 0.274–0.336 √I/(1 + 6√I). In binding medium, specific binding of ions to the protein takes place.

The delivery of drugs through targeted nanocarriers that are internalized by cells provides an alternative route to diffusion of drugs into cells. Growth factor or vitamin interactions with cancer cells represent a commonly used targeting strategy, as cancer cells often over-express the receptors for nutrition to maintain their fast-growing metabolism. In the case of circulating cancer cells, as in leukaemia and lymphoma, a therapy that targets surface antigens with high affinity and includes a carrier with a long circulating half-life may be the most efficacious. Abraxane is an albumin-bound paclitaxel nanoparticle formulation approved by the Food and Drug Administration in 2005 as a second-line treatment for metastatic breast cancer. The first angiogenesis inhibitor for treating colorectal cancer, Bevacizumab, an anti-VEGF mAb that inhibits the factor responsible for the growth of new blood vessels, was approved in 2004. Expelling drugs inevitably lowers the therapeutic effect and cancer cells soon develop resistance to a variety of drugs.