Photodynamic therapy induces oxidation in breast and brain cancer cell lines

Photodynamic Therapy (PDT) is a cancer treatment modality that utilizes both a photosensitizing drug and light irradiation. To better understand how PDT induces cell death, four human breast cancer (DC4, DB46, MCF7 and MDA-MB-435) and two rat glioma (BT4C and F98) cell lines were treated with 635 nm light from a diode laser following incubation with either PhotofrinRTM or aminoleuvilinic acid (ALA). Cellular responses were evaluated by: clonogenic survival, cell cycle distribution, fluorescent microscopy, protein oxidation and lipid oxidation assays. PDT was able to induce both apoptosis and necrosis as well as protein and lipid oxidation. Even though breast cancer cells were more sensitive to Photofrin RTM as compared to ALA-mediated PDT, there was less oxidation in the PhotofrinRTM treated cells. While it appears that Photofrin RTM and ALA-mediated PDT caused cell death by two different mechanisms, bulk oxidation of either lipids or proteins was not correlative to cellular survival