Master of Science
Biochemistry and Molecular Biology
Dr. W. Andrew Yeudall
Head and neck squamous cell carcinoma (HNSCC) is a type of cancer that begins in the epithelial cells that line the mucosal surfaces of the head and neck, including the oral cavity, pharynx, larynx, paranasal sinuses, nasal cavity, and salivary glands. Head and neck cancer is the sixth most common type of cancer with a 5-year survival rate of 60% for all cases. Over the past few years, a subset of cells with stem-like properties, called cancer stem cells, are believed to have tumor-initiation capabilities and are responsible for maintaining on-going tumor growth. Previous data from our lab suggested that cells grown in suspension, called spheroids, may have stem cell like properties.
We employed a model system where a primary HNSCC cell line, HN4, was used to set up spheroids. We found that expression of EPS8 and its downstream targets, FOXM1 and CXCL5, was increased in HN4 spheroids. In addition, we measured the expression of Nanog, as it is a transcription factor involved in the self-renewal of human embryonic stem cells. We also used a metastatic HNSCC cell line, HN12, to see how it compared to spheroids. We wanted to investigate the hypothesis that activation of Src potentiates EPS8 function to deregulate downstream signaling pathways. We used a small molecule tyrosine kinase inhibitor, Dasatinib, on HN4 spheroids and HN12 cells. We found that when Src is inhibited, EPS8 expression is decreased in HN4 spheroids and it also interferes with spheroid formation. The results of the current study were also able to show that the proliferation capability of HN12 cells is greatly diminished when treated with Dasatinib, due to G1 arrest in the cell cycle. When we measured for FOXM1, which is a cell cycle regulator, we found the levels were reduced in Dasatinib treated cells, preventing the cells from completing mitosis. With all of the data taken together, it suggests that Src does in fact play a role in regulating the downstream signaling pathways of EPS8, and its inhibition leads to the loss of cell proliferation. Additional studies need to be performed to discover whether Src inhibition will stop the proliferation of cancer stem cells, which are believed to be more resistant to cytotoxic therapies.
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Available for download on Wednesday, May 06, 2020