Abstract 1273: A novel molecular target for lung cancer
Authors: Velazquez Edwin J. , Weagel Evita G. , Meng Wei , Townsend Michelle H. , Cummonck Alex , Chandler Craig , Downey Michael R. , Robison Richard , O’Neill Kim L. 
Published: July 2016

The purpose of this study is to provide further evidence that Thymidine Kinase I (TK1) is selectively expressed on the surface of lung cancer cells, and therefore could be utilized as a potential molecular target. TK1 is an enzyme in the pyrimidine salvage pathway whose expression is closely correlated with cell proliferation and cell turnover. It has previously been shown that upregulation of TK1 is an early event in the development of most cancers. Additionally TK1 serum levels in cancer patients correlate with tumor progression and cancer aggressiveness. Moreover TK1 levels in the original tumors have also been shown to correlate directly with tumor recurrence thus making TK1 a useful prognostic marker in clinical oncology. Recent studies in our lab have provided evidence that TK1 is localized on the plasma membrane in lung cancer cells. Using scanning electron microscopy (SEM), flow cytometry, confocal microscopy and tissue staining, we confirmed the presence of TK1 on the cell surface of H460 cells. Using normal lymphocytes as a comparative control we found TK1 expression on lung cancer cells to be significantly increased compared to control cells. For this investigation, we used three custom designed monoclonal antibodies against human TK1 conjugated with FITC, namely CB1, A72 and A74. Using flow cytometry we confirmed the presence of TK1 on the cell surface, our data shows that H460 cells stained positive for TK1 (12% for A72, 19% for A74, and 29% for CB1). Furthermore, confocal microscopy indicated a positive fluorescent signal for A72, A74 and CB1, suggesting the presence of TK1 on the plasma membrane. SEM images of lung cancer cells and normal lymphocytes stained with TK1 antibodies and gold labeling reported a positive gold signal on H460 cells with relatively no signal from human lymphocytes. Immunohistochemistry staining of carcinoma tissue array panels compared with normal tissue array panels indicated a statistical significant difference of expression levels of TK1 between normal lung tissue and lung carcinoma (P value &lt;0.05). Positive staining was considered if more than 5% of the cells were stained. There was negligible staining in normal lung tissue. Using these techniques we confirmed that TK1 is selectively expressed on the surface of H460 cells and not on normal cells. These results suggest that TK1 could be used as a possible molecular target in lung cancer therapy. Further studies are currently ongoing to monitor TK1 expression and progression to help to elucidate the mechanisms behind it's over expression in cancer cells and to track its progression and movement from the cytosol to the cell surface.

Citation Format: Edwin J. Velazquez, Evita G. Weagel, Wei Meng, Michelle H. Townsend, Alex Cummonck, Craig Chandler, Michael R. Downey, Richard Robison, Kim L. O’Neill. A novel molecular target for lung cancer. [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 1273.