COOPERATION OF P120-¬CATENIN DOWNREGULATION AND PIK3CA MUTATIONS IN PROGRESSION OF HEAD AND NECK SQUAMOUS CELL CARCINOMA
Open Access
- Author:
- Kidacki, Michal A
- Graduate Program:
- Biomedical Sciences
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- April 14, 2017
- Committee Members:
- Douglas Stairs, Dissertation Advisor/Co-Advisor
Douglas Stairs, Committee Chair/Co-Chair
Diane Thiboutot, Committee Member
Lisa Shantz, Committee Member
Todd Schell, Outside Member
Edward Gunther, Committee Member - Keywords:
- p120-catenin
pik3ca
hnscc
invasion
migration
anchorage-independent growth
MMP1 - Abstract:
- Head and neck squamous cell carcinoma (HNSCC) is a highly invasive cancer diagnosed in over half a million people around the world every year. This deadly disease originates from squamous epithelia in the head and neck region and is associated with tobacco smoking, alcohol consumption, and Human Papilloma Virus (HPV) and Epstein Barr Virus (EBV) infections. HNSCC develops due to many different genetic aberrations. Loss of p120-catenin (P120CTN), a tumor suppressor, is one of such events. P120CTN is downregulated or lost in many cancers of epithelial origin. This loss frequently correlates with decreased HNSCC patient survival. In addition to P120CTN dysregulation, PIK3CA mutations are often found in HNSCC. For the scope of this dissertation we demonstrate two approaches to studying HNSCC. Our first approach focuses on a P120CTN-null mouse model and the immune milieu, while our second approach focuses on the interactions of P120CTN downregulation with the most common oncogene found in HNSCC, mutant PIK3CA. We demonstrate that activating PIK3CA mutations cooperate with P120CTN in promoting cell migration and invasion. Deletion of P120CTN in the mouse oral and esophageal epithelium leads to formation of squamous tumors with a concomitant increase in Myeloid-derived Suppressor Cells (MDSCs). We have investigated whether a specific subset of MDSCs is upregulated in the P120CTN-null mice. Although we observed several trends in our results, we did not identify any significant differences in the subset frequency between P120CTN-null and P120CTN-wild-type mice. We have also studied the effects of epithelial cells on MDSCs in vitro. P120CTN-null epithelial cells did not increase MDSC survival, activation or directional migration compared to P120CTN-wild type cells. Finally, we have assayed MDSC counts from P120CTN-wild-type and P120CTN-null tissues. Previous studies determined that P120CTN-null organs experience an increase in MDSCs. We have determined that this increase is systemic and can be seen in all of the tissues of a P120CTN-null mouse. We have also investigated the cooperation of P120CTN with the most common oncogene found in HNSCC, PIK3CA. We have utilized two different activating mutations of PIK3CA, E545K and H1047R, to investigate the cooperation of PIK3CA and P120CTN on anchorage-independent growth, migration, and invasion. We performed our experiments using two cell lines, normal oral keratinocytes (NOK) and normal esophageal keratinocytes (EPC1). We used cell lines that are as close as possible to normal cells to limit interference from other mutations. Additionally, we have confirmed the findings from our normal oral keratinocyte cell line in a normal esophageal keratinocyte cell lines, the most closely related keratinocyte cell line not derived from tumor samples. We have discovered that P120CTN downregulation and PIK3CA mutations cooperate to induce migration and invasion, while only minimally increasing the anchorage-independent growth. P120CTN downregulation and PIK3CA mutations increase invasion via increased MMP1 expression. Inhibition of MMP1 abrogates the invasion induced by P120CTN downregulation and PIK3CA mutations. The in vitro data were confirmed by analyzing The Cancer Genome Atlas (TCGA) database of HNSCC tumors. We have confirmed that MMP1 expression is increased in tumors with low P120CTN expression and enhanced PI3K pathway activity compared to tumors with high P120CTN expression and basal PI3K pathway activity. The role of MMP1 in HNSCC invasion provides a possible target for future drug development that could limit invasion of this cancer