Investigating the Role of CD44 in HER2+ Breast Cancer Cells During Cancer Cell Redirection

Author

Holly Caroline Jordan Campbell, Clemson UniversityFollow

Date of Award

12-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Bioengineering

Committee Chair/Advisor

Dr. Booth

Committee Member

Dr. Mount

Committee Member

Dr. Alexander-Bryant

Committee Member

Dr. Dunn

Abstract

Despite a rise in survival rates of breast cancer patients due to advances in modern medicine, breast cancer is the most common type of cancer in women and is the second leading cause of cancer death in the United States. Early detection and a more personalized treatment of breast cancer has slowly improved patient outcomes. Nevertheless, there are impediments to better patient outcomes due to the complexity of the disease physiology. Therefore, there is a demand for a comprehensive understanding of cancer development as well as a need to understand tumor progression for enhanced therapies for patients.

Previous in vivo studies showed that the normal mammary microenvironment influences non-mammary cells and tumor-derived cancer cells to participate in normal mammary gland development. The tumorigenic cells lose their tumor-forming capabilities and are “redirected” into normal, non-tumorigenic epithelial cells. We have named this behavior “cancer cell redirection.” We developed and validated an in vitro model to mimic the in vivo mammary microenvironment to study cancer cell redirection. We found that when breast cancer cells that overexpress HER2⁺ are redirected in our redirection model, phospho-HER2⁺ is silenced. We use HER2⁺ phosphorylation as a marker for cancer cell redirection though not a mechanism for cancer cell redirection. Earlier studies demonstrated and validated cancer cell redirection in both in vitro and in vivo models but have yet to answer how or why tumorigenic cells are “redirected” into normal, non-tumorigenic cells.

For this study, we first identified notable genes and pathways that could be used as potential targets during cancer cell redirection. Using gene expression data for cancer cell redirection, we found that CD44, a biomarker for breast cancer stem cells, played a significant role in cancer cell redirection. We validated that CD44 expression was altered in HER2⁺ breast cancer cells for both in vitro and in vivo cancer redirection models. Second, we investigated how CD44 expression functioned during normal cancer progression. We used a novel targeting peptide to knockdown CD44 using siRNA. After knockdown of CD44, we compared the function and 3D development of untreated HER2⁺ breast cancer cells to HER2⁺ breast cancer cells treated with peptide. Lastly, we combined our redirection model with the novel targeting peptide to further investigate how CD44 expression functioned during cancer cell redirection. Following knockdown of CD44, the treated HER2⁺ breast cancer cells were used in our in vitro cancer cell redirection model and compared to untreated HER2⁺ breast cancer cells. Expression levels of CD44 and 3D development were studied and compared for treated and untreated HER2⁺ breast cancer cells.

This study’s objective was to explore the mechanisms that play a role in cancer cell redirection. We have identified and verified that CD44 expression is a key factor in cancer cell redirection and that knockdown of CD44 affects its mammosphere development and phopho-HER2 expression. Manipulation of these mechanism have a valuable potential for therapeutic treatment in a clinical setting, and future studies should focus on further examination of these mechanisms.

Recommended Citation

Campbell, Holly Caroline Jordan, "Investigating the Role of CD44 in HER2+ Breast Cancer Cells During Cancer Cell Redirection" (2024). All Dissertations. 3855.
https://open.clemson.edu/all_dissertations/3855

Author ORCID Identifier

C21371073