CA: A Cancer Journal for Clinicians publishes information about the prevention, early detection, and treatment of cancer, as well as nutrition, palliative care, survivorship, and additional topics of interest related to cancer care.

Photodynamic therapy (PDT) is an emerging cancer therapy that uses the combination of non-toxic dyes or photosensitizers (PS) and harmless visible light to produce reactive oxygen species and destroy tumors. The PS can be localized in various organelles such as mitochondria, lysosomes, endoplasmic reticulum, Golgi apparatus and plasma membranes and this sub-cellular location governs much of the signaling that occurs after PDT. There is an acute stress response that leads to changes in calcium and lipid metabolism and causes the production of cytokines and stress response mediators. Enzymes (particularly protein kinases) are activated and transcription factors are expressed. Many of the cellular responses center on mitochondria and frequently lead to induction of apoptosis by the mitochondrial pathway involving caspase activation and release of cytochrome c. Certain specific proteins (such as Bcl-2) are damaged by PDT-induced oxidation thereby increasing apoptosis, and a build-up of oxidized proteins leads to an ER-stress response that may be increased by proteasome inhibition. Autophagy plays a role in either inhibiting or enhancing cell death after PDT.

Fullerenes are a class of closed-cage nanomaterials made exclusively from carbon atoms. A great deal of attention has been focused on developing medical uses of these unique molecules especially when they are derivatized with functional groups to make them soluble and therefore able to interact with biological systems. Due to their extended π-conjugation they absorb visible light, have a high triplet yield and can generate reactive oxygen species upon illumination, suggesting a possible role of fullerenes in photodynamic therapy. Depending on the functional groups introduced into the molecule, fullerenes can effectively photoinactivate either or both pathogenic microbial cells and malignant cancer cells. The mechanism appears to involve superoxide anion as well as singlet oxygen, and under the right conditions fullerenes may have advantages over clinically applied photosensitizers for mediating photodynamic therapy of certain diseases.

Photodynamic therapy (PDT) is a rapidly developing cancer treatment that utilizes the combination of nontoxic dyes and harmless visible light to destroy tumors by generating reactive oxygen species...