Among women worldwide, breast cancer is the second leading cause of death. Despite improved screening techniques and new treatments such as immunotherapies and targeted hormone therapy, survival rates of advanced or metastatic disease are at 27%. Current treatments focus on the primary tumor and are generally ineffective against metastases due to the location and heterogeneity of the metastatic tumor cells. However, all cells rely on the proteostasis network (PN), a collective term for protein synthesis, folding, and degradation, consisting of both chaperones and chaperonins. Chaperonin-containing TCP-1 (CCT) consists of 16 heterologous subunits (CCT1-8) and folds ~10% of the known proteome. However, breast cancer cells rely heavily on CCT clients including oncogenes and mutated tumor suppressors as well as essential cytoskeletal proteins. The objective of my research is to investigate the role of CCT in cancer by overexpressing or depleting a single CCT subunit, CCT2 (2nd subunit of CCT) in both breast cancer and normal breast epithelial cells. We found increasing CCT2 in a 2D setting leads to a more invasive phenotype in breast cancer cells characterized by increased proliferation and migration. Additionally we observed increased tubulin, one of CCT's obligate clients as well as increasing other CCT subunits. Loss of CCT2 leads to cell death, reduction of other CCT subunits, and in vivo prevents tumors from forming. To further understand the role of CCT, we grew CCT2 overexpressing breast cancer lines as spheroids, an in vitro tumor analogue. The CCT2 overexpressing spheroids grew faster and larger than control cells. Additionally, they express increased actin, another CCT obligate client, as well as show significantly increased attachment with both cell-to-cell and cell-to-substrate connections, which could be suggestive of a metastatic phenotype. Finally, we used a CCT inhibitor, CT20p, to treat breast cancer cells and found it induces immunogenic cell death (ICD). ICD stimulates the immune system to attack the tumor cells and mice vaccinated with dying CT20p-treated cells did develop protective immunity against challenge with live cancer cells. Investigating the role of CCT in breast cancer advances both a novel marker and potential target for new cancer treatments, meeting an urgent need to reduce the mortality of advanced and metastatic breast cancer.
Doctor of Philosophy (Ph.D.)
College of Medicine
Length of Campus-only Access
Doctoral Dissertation (Campus-only Access)
Showalter, Anne, "Chaperonin-containing TCP-1 Modulates Breast Cancer Growth and Malignancy" (2020). Electronic Theses and Dissertations, 2020-. 457.