Triple negative breast cancer (TNBC) is a particularly aggressive form of breast cancer that lacks the three molecules typically targeted for treatment. It shares many characteristics with basal-type and BCRA1-related tumors; however, not all TNBC’s show these characteristics. Standard treatment methods leave much to be desired- the rates of metastasis and recurrence are high and the prognosis for most patients with TNBC is poor. One potential treatment for TNBC is photodynamic therapy, which uses compounds called photosensitizers that are taken up by all tissues in the body. The tumor is exposed to light, activating the photosensitizer and creating reactive oxygen species that cause cell death. This method is relatively pain-free, effective, and does not harm cells that aren’t exposed to light. The goal of our experiments is to assess the effectiveness as PDT agents of porphyrin derivatives <i>in vitro</i> on MDA-MB231 triple-negative breast cancer cells. An MTT assay was performed to quantify cell death. Cells that were exposed to light showed concentration-dependent cell death and the LD<sub>50</sub> of each porphyrin was measured. Cells not exposed to light only showed dark toxicity at high porphyrin concentrations. For one of the porphyrins, experiments were performed to determine the mechanism of cell death. A TUNEL assay was performed to measure DNA fragmentation, and the TUNEL-stained cells were co-stained with antibodies against caspase 3, HO1, EndoG, and OGG1 to help identify the method of cell death. Cells treated with our porphyrin PipOH and light show a significant increase in TUNEL and OGG1 staining, suggesting that the cells are dying by a cell-death mechanism induced by cytoplasmic oxidative damage. Caspase 3 levels were also elevated in cells treated with PipOH, whether or not they were exposed to light, suggesting that apoptosis induced by this treatment was mostly caspase-dependent. These experiments suggest that the cells are dying through primarily via caspase-dependent apoptosis. We would like to repeat these experiments using flow cytometry so that we can include in the staining the cells that detached from the dish during the experiment to better assay what fraction of the cells die via apoptosis, autophagy, necrosis, or another mechanism. Understanding the relative phototoxicity and mechanism of cell death for these compounds in these tumor cells will guide the design of compounds with improved properties as PDT agents.

Effectiveness and mechanism of action of modified porphyrins for photodynamic therapy of triple negative breast cancer cells

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.