Publications

Aims: The naturally occurring compound curcumin has been proposed for a number of pharmacological applications. In spite of the promising chemotherapeutic properties of the molecule, the use of curcumin has been largely limited by its chemical instability in water. In this work, we propose the use of water soluble proteins to overcome this issue in perspective applications to photodynamic therapy of tumors. Materials and methods: Curcumin was bound to bovine serum albumin and its photophysical properties was studied as well as its effect on cell viability after light exposure through MTT assay and confocal imaging. Key findings: Bovine serum albumin binds curcumin with moderate affinity and solubilizes the hydrophobic compound preserving its photophysical properties for several hours. Cell viability assays demonstrate that when bound to serum albumin, curcumin is an effective photosensitizer for HeLa cells, with better performance than curcumin alone. Confocal fluorescence imaging reveals that when curcumin is delivered alone, it preferentially associates with mitochondria, whereas curcumin bound to bovine serum albumin is found in additional locations within the cell, a fact that may be related to the higher phototoxicity observed in this case. Significance: The higher bioavailability of the photosensitizing compound curcumin when bound to serum albumin may be exploited to increase the efficiency of the drug in photodynamic therapy of tumors.

JTD Keywords: Cancer, Curcumin, Live cell imaging, Photodynamic therapy

Although cytotoxic chemotherapy is one of the primary pharmacological treatments for chronic hyperproliferative diseases such as cancer and psoriasis, its efficacy and tolerability are in many cases dramatically limited by off-target toxicity. A promising approach to improve these therapies is to activate the drugs exclusively at their desired place of action. In fact, in those diseases that would benefit from a highly localized treatment, a precise spatiotemporal control over the activity of a chemotherapeutic agent would allow reducing the concentration of active compound outside the targeted region, improving the tolerability of the treatment. Light is a powerful tool in this respect: it offers unparalleled opportunities as a non-invasive regulatory signal for pharmacological applications because it can be delivered with high precision regarding space, time, intensity and wavelength. Photopharmacology represents a new and emerging approach in this regard since the energy of light is used to change the structure of the drug and hence to switch its pharmacological activity on and off on demand. We describe here phototrexate, the first light-regulated inhibitor of the human DHFR. Enzyme and cell viability assays demonstrated that phototrexate behaves as a potent antifolate in its cis configuration, obtained under UVA illumination, and that it is nearly inactive in its dark-relaxed trans form. Experiments in zebrafish confirmed that phototrexate can disrupt folate metabolism in a light-dependent fashion also in vivo. Overall, phototrexate represents a potential candidate towards the development of an innovative photoactivated antifolate chemotherapy.

JTD Keywords: Cancer, Dermatology, Methotrexate, Photoactivated chemotherapy, Photodynamic therapy, Phototherapy, Psoriasis, Rheumatoid arthritis

The efficacy and tolerability of systemically administered anticancer agents are limited by their off-target effects. Precise spatiotemporal control over their cytotoxic activity would allow improving chemotherapy treatments, and light-regulated drugs are well suited to this purpose. We have developed phototrexate, the first photoswitchable inhibitor of the human dihydrofolate reductase (DHFR), as a photochromic analog of methotrexate, a widely prescribed chemotherapeutic drug to treat cancer and psoriasis. Quantification of the light-regulated DHFR enzymatic activity, cell proliferation, and in vivo effects in zebrafish show that phototrexate behaves as a potent antifolate in its photoactivated cis configuration, and that it is nearly inactive in its dark-relaxed trans form. Thus, phototrexate constitutes a proof-of-concept to design light-regulated cytotoxic small molecules, and a step forward to develop targeted anticancer photochemotherapies with localized efficacy and reduced adverse effects.

JTD Keywords: Photopharmacology, Photodynamic therapy, Antiproliferative, Arthritis, Psoriasis, Nanomedicine