Abstract 1213: Thymidine kinase 1 is on the cell surface of prostate cancer cells

Thymidine Kinase 1 (TK1) is a salvage pathway enzyme that assists in DNA repair and is characteristically expressed in the cytosol, but it also presents at an abnormally high level in the serum of cancer patients. We developed a unique mouse-anti-human TK1 antibody (A72), and used it in conjunction with Flow Cytometry, Scanning Electron Microscopy (SEM), and Confocal Microscopy, to explore the presence of TK1 on the cell surface of two prostate cancer cell lines, namely PC3 and DU145. Flow Cytometry was performed using a standard protocol. Briefly, cells were stained with A72 conjugated to FITC. Anti-NF-κB-FITC and a non-specific IgG-FITC were used as negative controls. Anti-Na+/K+-ATPase-FITC was used as positive control. Cells were then analyzed using a Flow Cytometer. SEM was carried out by first incubating cells with anti-Na+/K+-ATPase and anti-TK1 conjugated to biotin. After probing with streptavidin-gold solution, cells were imaged to examine the presence of gold particles on cell surface. Our data demonstrated TK1-positive populations after flow cytometry analysis, and the presence of gold particles on the membrane of prostate cancer cells. The presence of TK1 on plasma membrane of PC3 and DU145 was further confirmed by Confocal Microscopy. Cells were first stained with A72-FITC and a red plasma membrane stain, then consecutively imaged with a Confocal Microscope. Results showed that A72-FITC associate with the cells in the same region that the membrane had been stained red, concluding that the A72 binds to the cell membrane. These data strongly suggest that TK1 is located on the surface of prostate cancer cells, and indicate that TK1 may be used as a new immunotherapy target for prostate cancer treatment. Citation Format: Evita G. Weagel, Roger P. Chu, Wei Meng, Rachel A. Brog, Michelle H. Townsend, Richard A. Robison, Kim L. O’Neill. Thymidine kinase 1 is on the cell surface of prostate cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1213.