Introduction: Photodynamic therapy (PDT) is a minimally invasive, FDA approved therapy for
treatment of several indications including endobronchial and esophageal cancers that are
accessible to light. Triple negative breast cancer (TNBC) and inflammatory breast cancer (IBC)
are aggressive and lethal subtypes of breast cancer that spread to chest wall and dermal
lymphatics, respectively, sites that would be accessible to light. Both TNBC and IBC patients
have a relatively poor survival rate due to lack of targeted therapies. Use of PDT is
underexplored for breast cancers but has been proposed for treatment of subtypes for which a
targeted therapy is unavailable.
Methods: We optimized and used a mammary architecture and microenvironment engineering
(MAME) model of IBC to examine the effects of PDT using two treatment protocols. The first
protocol used the benzoporphyrin derivative monoacid A (BPD) activated at doses ranging from
45 mJ/cm2 to 540 mJ/cm2. The second PDT protocol used two photosensitizers: BPD and mono-
L-aspartyl chlorin e6 (NPe6), which were sequentially activated. Effects of PDT were assessed
by live-dead assays.
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Results: Using a MAME model of TNBC and IBC, we demonstrate a significant dose-response
in photokilling by BPD-PDT. We found that sequential activation of NPe6 followed by BPD is
more effective in photokilling of tumor cells than is BPD alone. Sequential activation at a dose
of 45 mJ/cm2 each resulted in \u3e90% cell death, a response only achieved by BPD-PDT at a dose
of 360 mJ/cm2. Furthermore, our data show that volumetric measurement of 3D MAME
structures reflect efficacy of PDT treatment. We also show that the mechanism of cell death
after sequential activation of NPe6 followed by BPD is apoptosis.
Conclusion: Our study is the first to demonstrate the potential of PDT in treating MAME
structures of TNBC and IBC
