Investigating Triple Negative Breast Cancer Cell Internalization of Doxorubicin-Loaded Glycogen Nanoparticles and Corresponding DNA Repair Expression

Breast cancer is the leading cause of death of women, worldwide. Triple negative breast cancer is an aggressive subtype characterized by the lack of 3 essential cell receptors: estrogen, progesterone, and human epidermal growth factor 2. Due to the lack of receptors, targeted therapies are often unsuccessful. Doxorubicin is a common anthracycline chemotherapy drug that is a topoisomerase II inhibitor. It causes double strand breaks in the DNA, which causes the cells to induce apoptosis. Unfortunately, the off-target cardiotoxicity from doxorubicin treatment leaves patients with a poor quality of life. The Sun and Senejani research groups at the university of New Haven have been working on a targeted, integration-free doxorubicin-loaded nanocarrier for pH triggered release in acidic tumor microenvironments. This study aimed to compare the cellular uptake of doxorubicin versus doxorubicin-loaded glycogen nanoparticles (DLG) and to evaluate the mRNA levels of DNA repair genes (ERCC1, ERCC4, MSH2, MLH1) in treated MDA-MB-231 and MCF-10A cells. This is to determine the time-dependent kinetics of repair by monitoring the gene expression levels with the drug uptake profiles. The results showed that DLG does have a pH-dependent release of doxorubicin, and that it also has a much higher and efficient cellular uptake than free doxorubicin in both cell lines. Baseline gene expression of the DNA repair genes was also elevated in MDA-MB-231 cells. For treated cells, MDA-MB-231 had a sustained upregulation of MSH2 even after 24 hours of recovery after treatment which suggests tolerance. MCF-10A cells only had repair responses when they were almost fully saturated with the treatments and went back to normal expression levels after recovery. These findings suggest that MDA-MB-231 cells have the ability to tolerate and recognize damage without repair, leading to drug resistance regardless of formulation. This research highlights the importance of optimizing existing treatments for better delivery and efficacy and shows the potential of integration-free delivery systems for not just cancer cells, but for wide applications in the body.