Abstract 1239: The expression of salvage pathway enzymes in non-small cell lung cancer cells
Authors: Townsend Michelle H. , Weagel Evita G. , Anderson Michael D. , Velazquez Edwin , Robison Richard A. , O'Neill Kim L. 
Published: July 2017

The aim of this study is to evaluate the expression of the salvage pathway enzymes DCK, APRT, and HPRT in lung cancer cells to determine if they could serve as biomarkers for lung cancer diagnosis and potential treatment. In both men and women, lung cancer is the most lethal cancer in the world, and accounts for more than 30% of cancer-related deaths. We chose to evaluate the salvage pathway enzymes due to an established relationship between the serum biomarker Thymidine Kinase 1 (TK1) and lung cancer. Two non-small cell lung carcinoma cell lines were utilized for this analysis (NCI-H460 and A549) along with cancer tissue and healthy tissue from 27 lung squamous carcinoma patients. The surface localization of these enzymes was determined utilizing flow cytometry, confocal microscopy, and scanning electron microscopy, while upregulation within tissue was assessed using immunohistochemistry (IHC). Throughout our investigation, we found no significant expression of DCK or APRT on the surface of non-small cell lung cancer cells, but found a significant presence of HPRT on the plasma membrane of both NCI-H460 and A549 cells. The average population florescence of cells treated with HPRT antibodies increased by 24.3% and 12.9% in NCI-H460 and A549 cells, respectively, in comparison to controls. To ensure expression was not attributed to cytoplasmic HPRT, confocal microscopy was performed to visualize HPRT binding on the plasma membrane. After staining NCI-H460 cells treated with both fluorescent antibodies and a membrane-specific dye, we observed direct overlap between HPRT and the membrane of the cancer cells. Additionally, gold conjugated antibodies were used to label and quantify the amount of HPRT on the cell surface using scanning electron microscopy and EDAX. Further confirming HPRT presence, the gold weight percentage of the sample increased significantly when NCI-H460 cells were exposed to HPRT antibody (p-value 0.012) in comparison to isotype controls. Finally, the general upregulation of the protein was observed in patient tissue samples, with approximately 44% of lung cancer tissues showing significant HPRT upregulation when compared to healthy tissue samples. This differential upregulation shows an altered HPRT expression within some patients, which may help explain the presence of this presumed cytosolic enzyme on the surface of lung cancer cells. These results strongly indicate a unique relationship between cancer cells and HPRT and suggest HPRT as a possible biomarker for the detection and treatment of non-small cell lung cancers.

Citation Format: Michelle H. Townsend, Evita G. Weagel, Michael D. Anderson, Edwin Velazquez, Richard A. Robison, Kim L. O'Neill. The expression of salvage pathway enzymes in non-small cell lung cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1239. doi:10.1158/1538-7445.AM2017-1239