Non-small-cell lung cancer cell lines A549 and NCI-H460 express hypoxanthine guanine phosphoribosyltransferase on the plasma membrane

Michelle H Townsend, Michael D Anderson, Evita G Weagel, Edwin J Velazquez, K Scott Weber, Richard A Robison, Kim L O’Neill Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT, USA Abstract: In both males and females, lung cancer is one of the most lethal cancers worldwide and accounts for >30% of cancer-related deaths. Despite advances in biomarker analysis and tumor characterization, there remains a need to find suitable biomarker antigen targets for treatment in late-stage lung cancer. Previous research on the salvage pathway enzyme TK1 shows a unique relationship with cancer patients as serum levels are raised according to cancer grade. To expand this analysis, the other salvage pathway enzymes were evaluated for possible upregulation within lung cancer. Adenine phosphoribosyltransferase, deoxycytidine kinase, and hypoxanthine guanine phosphoribosyltransferase (HPRT) were assessed for their presentation on two non-small-cell lung cancer cell lines NCI-H460 and A549. In the present study, we show that deoxycytidine kinase and adenine phosphoribosyltransferase have no significant relationship with the membrane of NCI-H460 cells. However, we found significant localization of HPRT to the membrane of NCI-H460 and A549 cells. When treated with anti-HPRT antibodies, the average fluorescence of the cell population increased by 24.3% and 12.9% in NCI-H460 and A549 cells, respectively, in comparison with controls. To ensure that 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 energy-dispersive analysis X-ray. Further confirming HPRT presence, the gold weight percentage of the sample increased significantly when NCI-H460 cells were exposed to HPRT antibody (P=0.012) in comparison with isotype controls. Our results show that HPRT is localized on the surface of these non-small-cell lung cancer cell lines. Keywords: non-small-cell lung cancer, NCI-H460, A549, surface antigen, hypoxanthine guanine phosphoribosyltransferas

Biomarker analysis and clinical relevance of TK1 on the cell membrane of Burkitt’s lymphoma and acute lymphoblastic leukemia

Evita G Weagel,1 Wei Meng,1 Michelle H Townsend,1 Edwin J Velazquez,1 Rachel A Brog,1 Michael W Boyer,2 K Scott Weber,1 Richard A Robison,1 Kim L O’Neill1 1Department of Microbiology and Molecular Biology, Brigham Young University, Provo, 2Division of Hematology and Hematologic Malignancies, Department of Medicine, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT, USA Abstract: TK1 is an enzyme involved in DNA synthesis and repair. TK1 is usually found elevated in cancer patients’ serum, which makes it a useful tumor proliferation biomarker that strongly correlates with cancer stage, metastatic capabilities, and recurrence risk. In this study, we show that TK1 is upregulated and localizes on the plasma membrane of Burkitt’s lymphoma, acute promyelocytic leukemia, T cell leukemia, and acute lymphoblastic leukemia (ALL). Using flow cytometry, we confirmed that TK1 localizes on the surface of Raji, HL60, and Jurkat cell lines and on ALL clinical samples. Using fluorescent microscopy, we found a strong association of TK1 with the plasma membrane in Raji, HL60, and Jurkat cell lines. These findings were also confirmed by scanning electron microscopy. Our study also shows that this phenomenon does not occur on normal resting or proliferating lymphocytes. In addition, we show that membrane TK1 is found in all oligomeric forms ranging from monomer to tetramer and exhibits enzymatic activity. These findings suggest TK1 as a possible target for immunotherapy with the potential to be utilized in the treatment of hematological cancers. Keywords: Burkitt’s lymphoma, acute lymphoblastic leukemia, ALL, thymidine kinase 1, surface antige