Analysis of Photodynamic Therapeutic Treatment of HER2-Positive Breast Cancer In Vitro

Abstract Photodynamic therapy (PDT) is a minimally invasive cancer treatment method. The antitumor effect of PDT mediated by the photosensitizer meta-tetra(hydroxyphenyl)chlorin (m-THPC) was studied in vitro on HER2-positive (HER2 + ) breast cancer cells. Since the application of m-THPC is limited due to poor tumor targeting abilities, the polymer carrier dextran-grafted-polyacrylamide (D-g-PAA) with attached gold nanoparticles was loaded with m-THPC to provide a light-responsive, tumor targeting nanocomposite. The nanocomposite was absorbed by the cancer cells within 90 min and activated through irradiation with red light at a wavelength of 660 nm. In this study, the efficiency and ideal dose of the nanocomposite were evaluated and determined based on cell viability and induction of apoptosis of HER2 + breast cancer cells and human breast epithelial cells. We demonstrate that the nanocomposite exhibited phototoxicity with cell mortality exceeding 50% for the HER2 + breast cancer cells. In contrast, the human breast epithelial cells were minimally affected at the same concentration of the nanocomposite, demonstrating the tumor-targeting abilities of the developed nanocomposite. Dark toxicity was also comparably lower, indicating the limited effect of the unactivated nanocomposite. The results revealed that apoptosis was the primary mode of cell death in HER2 + breast cancer cells. Apoptotic cell death was induced in HER2 + breast cancer cells via the caspase-3, caspase-9, and Bax pathways. In conclusion, the studied nanocomposite demonstrated excellent PDT performance with good antitumor activity under light irradiation in vitro and is worthy of further investigation as an alternative treatment for HER2 + breast cancer.