Protein-based nanotechnology: antibody conjugated with photosensitizer in targeted anticancer photoimmunotherapy

Photodynamic therapy (PDT) is a minimally invasive cancer therapy that depends on the buildup of a photosensitizing drug within targeted tissue. The photosensitizer is subsequently activated by light of a specific wavelength, resulting in destruction of the targeted tissue by free radicals or singlet oxygen. Successful treatment requires delivery of critical amounts of drug into the cancerous tissue. This frequently demands high doses of the drug in the circulatory system that could lead to side effects in normal daylight due to accumulation of photodrug in normal tissue. To reduce drug load we explored the possibility of targeting cancer with antibody conjugated with photosensitizer. As a model we used LnCAP human prostate cancer cells targeted by antibody (against prostate-specific membrane antigen) which was conjugated with hematoporphyrin (HP). Our results show clearly that mAb/HP conjugates can deliver HP to the tumor cells which would result in considerably less HP in the circulation and, therefore, lower the delivery of HP to normal tissue, resulting in fewer side effects.