The Influence of Hyaluronic Acid Metabolism on the Development of Chemoresistance in 3D Breast Cancer Cell Models

Abstract

Breast cancer is the most diagnosed malignancy in the world. Of the various subtypes of breast cancer cells, the ductal carcinoma is responsible for 70% to 80% of worldwide breast cancer diagnoses. Current treatments for breast cancer include hormonal therapy, surgery, radiation therapy, and chemotherapy. Unfortunately, many breast cancer tumors become resistant to these therapies overtime prompting the need for new targeted therapies. It is becoming increasingly clear that the tumor microenvironment plays a critical role in tumor cell survival and development of resistance. In particular, the CD44 receptor and its ligand hyaluronic acid (HA) have been implicated in a number of processes related to tumor progression and survival. HA is a major component of the extracellular matrix (ECM) in both normal and abnormal tissues. In this current study we focused on examining the role of HA metabolism on the resistance of breast cancers to the commonly used chemotherapeutic agent doxorubicin (dox). Specifically, we examined the influence of HA in the ductal carcinoma cell line, MCF-7 using both a 2D and 3D tumor model. The results from this study supported previous findings that 3D MCF-7 cultured cells are resistant to doxorubicin treatment when compared to 2D models and further established the novel finding that cells grown in 3D models have increased gene expression of hyaluronic acid synthase. Consequently, 4-methylumbelliferone (4MU) was chosen due to its inhibiting mechanism during HA synthesis. For this reason, 4MU’s effect was vital to our hypothesis regarding modifications of HA content to augment the strength of low concentrations of dox on tumor cells. MCF-7 cells were grown and cultured two-dimensionally and three-dimensionally using unique methods and specialized plates. Assays were used to quantify and contrast the HA content in each culture along with the specific enzymes responsible for HA’s anabolic and catabolic processes. Then, overall cellular proliferation was measured after administering dox and 4MU separately followed by combination treatments of both. Results revealed an increase in HA synthase enzymes in the 3D cultures; however, overall HA concentration was lower when compared to the 2D cultures. Cellular proliferation was repeatedly measured, and on average, 3D cultures were more resistant to individual treatments of dox and 4MU. Similar results were seen when combination treatments were administered, and cellular proliferation did not decrease in the 3D groups.