Poster G7 - Photodynamic Therapy and Triple Negative Breast Cancer: In Vitro Evaluation of Treatment Efficacy

Saturday, October 26, 2024

10:00 AM - 11:00 AM EST

Location: Exhibit Hall E, F & G

Presenting Author(s)

Landon C. Ethredge (he/him/his)

Undergraduate Researcher
Clemson University
Clemson, South Carolina, United States

Co-Author(s)

HW

Hunter S. Warren

PhD Student
Clemson University
Gaffney, South Carolina, United States

Primary Investigator(s)

BB

Brian Booth

Associate Professor
Clemson University, United States

Introduction: Triple negative breast cancer (TNBC) is an aggressive form of breast cancer, accounting for 7% of all cancer deaths and acting as a leading cause of death for women diagnosed with cancer. Photodynamic therapy (PDT) represents a minimally invasive therapeutic alternative for TNBC patients by utilizing passive-targeting in its treatment of TNBC compared to other well established yet harsh treatments. PDT uses high-energy red light to activate injected photosensitizers (PS) in the tumor area. These in turn generate reactive oxygen species (ROS) in the tumor, triggering cell death. In these studies, tetra(hydroxyphenyl)chlorin (m-THPC) was used as the PS due to its high singlet oxygen yield activated by 660-670 nm light. Owing to m-THPC’s hydrophobic nature, a hydrophilic dextran-grafted-polyacrylamide (D-g-PAA) polymer carrier was needed for the systemic circulation of the nanocomposite. After the nanocomposite is taken up by TNBC cells due to enhanced permeability and retention, D-g-PAA’s pH sensitivity encourages the release of m-THPC from the polymer’s active amide group when in the presence of the typically acidic tumor microenvironment so that m-THPC can effectively make ROS when activated. Gold nanoparticles (AuNPs) were also incorporated into the novel nanocomposite due to their hyperthermic effect on their surrounding environment when heated by the wavelengths used, thereby enhancing tumor cell death.

The aim of this study was to identify an ideal concentration of PDT nanocomposite for the treatment of human TNBC cells while causing little to no damage to normal breast epithelial cells in vitro.

Materials and

Methods: Various concentrations of PDT nanocomposite components were tested on human cell lines to identify an ideal concentration of PDT that selectively killed TNBC cells (MDA-MB-468) over normal breast epithelial cells (MCF10A-GFP). These treatments were conducted with a minimal amount of ambient light and only experimental groups were exposed to Near Infrared Light (NIR) ranging from 660-670 nm. After treatment, cell counts were conducted using flow cytometry to determine the potency of each concentration.

Once ideal concentrations of the nanocomposite components were identified, cell viability after PDT treatment was assessed using MTT assay. TUNEL assays were also conducted after PDT treatment to observe if apoptosis was the primary mechanism of cell death. Finally, Western blotting was performed on PDT treated cells to identify the presence of key apoptotic proteins like BCL-2, Caspase-9, and Caspase-7.

Results, Conclusions, and Discussions: Through this study, PDT was demonstrated to be effective in targeting and eliminating TNBC cells in vitro and a stronger understanding of the mechanism of PDT-induced cell death was gained. Cell counts indicated that an ideal concentration of our PDT nanocomposite significantly reduced TNBC cell populations without significantly impairing normal epithelial cell growth. Additionally, the results of this study suggest that apoptosis is the primary mechanism of cell death caused by PDT nanocomposite treatments. Overall, these results represent significant progress in breast cancer treatment by demonstrating PDT efficacy in killing TNBC.

Acknowledgements (Optional):