Photochemotherapy in the treatment of cancer.

The development of therapies which are selective for tumor tissues is one of the most important goals in anticancer research. Within this framework photochemotherapy can be considered a very promising approach. Its therapeutic effectiveness depends on two connected factors: drug and light. The drug (photosensitizer) is able to exert an antiproliferative effect only after interaction with suitable light. Both the photosensitizing drug and light alone are ineffective at doses used for these treatments. Nowadays, photochemotherapy is used in the treatment of cutaneous T-cell lymphoma and cavitary tumors. In the first case the photosensitizer is a psoralen derivative (P) and long-wavelength ultraviolet radiation (UVA) is used (PUVA therapy). In the second case, the treatment with porphyrins, porphyrin-based and non porphyrin-based photosensitizers is followed by irradiation with 600-1000 nm light (photodynamic therapy, PDT). This review is concerned with PUVA and PDT treatments of cancer. The molecular mechanisms considered accountable for the photochemotherapeutic effects are discussed, the development of new chemical structures aimed at improving the effectiveness and/or overcoming some undesired side effects will also be reported. Moreover, some clinical applications will be described.