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There are limited effective options for treatment of triple negative breast cancer (TNBC) due to its lack of the three receptors typically used to target breast cancer. The use of photodynamic therapy (PDT) to kill cells that take up light-absorbing compounds (PDT agents) may be an effective option to treat TNBC. We tested the efficacy of modified porphyrins as PDT agents against cells from TNBC. We compared these to Foscan, which is similar in structure to porphyrins and has been approved for use in Europe. Our 1st goal was to measure which porphyrins were taken up best by TNBC cells. Measuring the uptake of some of our compounds had been problematic due to their hydrophobic nature. We optimized the uptake protocol and showed that TNBC cells take up the compounds to different extents. One of the primary side effects of PDT is skin toxicity for up to 4-6 weeks after treatment due to exposure to sunlight. Our 2nd goal was to compare the toxicity in the light and in the dark of PipOH, H2TPPC, and Foscan. In previous experiments, Foscan showed dark toxicity at low concentrations, but in these experiments there was variability in our results with Foscan so no clear comparison could be drawn. Our 3rd goal was to find combinations of PDT agent and concentration that are effective on TNBC cells at high light energy but minimize killing cells with ambient light. We measured the effect on cell killing by varying both the light dose and the concentration of 3 compounds to find concentrations that are effective at high doses of light but minimize toxicity at moderate doses. All 3 compounds show promise, but the dose must be carefully selected.



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