PDZ-BINDING KINASE PROMOTES ADRENOCORTICAL CARCINOMA CELL PROLIFERATION AND TUMORIGENESIS

Adrenocortical carcinoma (ACC) is a rare and deadly disease that affects an estimated 1-12 people per million per year in the US. Currently, the only accepted clinical treatments are surgical resection and treatment with the chemotherapy agent mitotane. These interventions have had limited effectiveness, however, as the five-year survival rate of ACC patients in the US is less than 35%. Therefore, further scientific investigation of the disease is of high importance. The aim of this project was to identify potential biomarkers that may be used for developing new therapies or other novel clinical interventions. An analysis of publicly-available datasets revealed PDZ-binding kinase (PBK) as being upregulated roughly 9-fold in ACC tissue compared to normal adrenal tissue. PBK has been implicated as an oncogene in several other systems, and its expression has been shown to negatively impact patient survival. Preliminary experiments have confirmed the upregulation of PBK in H295R cells, a human ACC cell line. We were able to effectively silence PBK (>95% silencing) in H295R cells by using lentiviral shRNA constructs. Using highly and lowly expressing cells, we performed soft agar assays for colony formation, and found that the PBK-silenced cells produced two-fold fewer colonies than the vector control (p<0.05). This indicates that PBK likely plays a role in tumorigenicity. We further conducted functional studies for apoptosis and proliferation to illuminate the mechanism by which PBK increases tumorigenicity. Preliminary results from MTS assays showed that after 9 days, PBK-silenced cells proliferated significantly less than the vector control, so PBK likely increases proliferation. Together these data identify PBK as a potential therapeutic target in adrenocortical carcinoma.