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Oncolytic viruses (OVs) are being extensively studied for their potential roles in the development of cancer therapy regimens. In addition to their direct lytic effects, OVs can initiate and drive systemic antitumor immunity indirectly via release of tumor antigen, as well as by encoding and delivering immunostimulatory molecules. This combination makes them an effective platform for the development of immunotherapeutic strategies beyond their primary lytic function. Engineering the viruses to also express tumor-associated antigens (TAAs) allows them to simultaneously serve as therapeutic vaccines, targeting and amplifying an immune response to TAAs. Our group and others have shown that vaccinating intratumorally with a poxvirus that encodes TAAs, in addition to immune stimulatory molecules, can modulate the tumor microenvironment, overcome immune inhibitory pathways, and drive both local and systemic tumor specific immune responses.

In the Abstract of this Letter, 'released' should have been 'regulated' in the sentence: 'Deletion of Atg5 in the host similarly regulated circulating arginine and suppressed tumorigenesis, which demonstrates that this phenotype is specific to autophagy function rather than to deletion of Atg7. ' This has been corrected online. CORRECTIONS & AMENDMENTS3 J A N U A R Y 2 0 1 9 |

In the version of this article initially published, Supplementary Tables 1-3 and 11-13 were omitted from the Supplementary Information file. The error has been corrected.

Thymidine Kinase 1 (TK1), a salvage pathway enzyme responsible for recycling thymine in cells for use in DNA replication and repair, is normally tightly regulated by the cell cycle; however research studies have shown that it is over-expressed and unregulated in cancer cells. Studies linking TK1 localization to the plasma membrane of lymphoma cells have suggested that this enzyme could also be used as a molecular target for cancer diagnosis and therapy. Previous research in our laboratory showed that TK1 located on the plasma membrane of different cancer cell lines had high enzymatic activity. This study was performed to support the eventual possibility of targeting TK1 for cancer diagnosis and immunotherapy in leukemias expressing high levels of TK1 on their plasma membrane. TK1 levels on plasma membrane were analyzed using a BD FACSCanto flow cytometry on lymphoblastoid cells derived from Burkitt's lymphoma (Raji cells), acute T cell leukemia (Jurkat cells), myeloblastic cells derived from promyelocytic leukemia (HL-60 cells), and normal lymphocytes from healthy individuals. Analysis was performed on unpermeabilized cells in exponential growth phase using both a mouse monoclonal anti-TK1 Ab and a rabbit polyclonal anti TK-1 Ab. Cells were incubated with human FcR blocking reagent to eliminate non-specific binding to Fc receptors. Permeabilized cells were excluded using propidium iodide staining. Using an IgG Isotype control we were able to select proper gating (0% binding). TK1 surface expression was compared to expression of sodium potassium ATPase, a common plasma membrane marker, and pan-leukocyte marker CD45. Results confirmed high levels of TK1 expression on cancer cell lines analyzed. Flow cytometry analysis showed that binding of the mouse monoclonal anti-TK1 Ab and rabbit polyclonal anti-TK1 Ab were 93.4% (SEM=1.05, N = 19) and 99.5 % (SEM=0.67, N=19) in Raji cells; 71.1% (SEM=3.41, N=19) and 89.4 % (SEM=2.74, N=19) in HL-60 cells; 63% (SEM=1.23, N=26) and 88.6% (SEM=1.81, N=27) in Jurkat cells. Lymphoblastoid cells showed significantly higher TK1 expression when compared to that of lymphocytes obtained from healthy individuals 9.9% (SEM=2.39, N=7) and 14.9% (SEM=2.43, N=3). When induced with pokeweed mitogen there was no increase in TK1 expression on the plasma membrane of normal dividing lymphocytes 7.9% (SEM=0.54, N=3) and 10.63% (SEM=2.89, N=3). Fluorescence microscopy observations provided more evidence of TK1 association with the plasma membrane of cancer cells. These results suggest that membrane-bound TK1 has potential for both diagnosis and immunotherapy in human leukemia. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3162. doi:10.1158/1538-7445.AM2011-3162

Thymidine Kinase 1(TK1) is a salvage pathway enzyme that has been shown to be elevated in many different cancer types, including breast, prostate, and colon. Previous research in our lab using plasma membrane separation has shown an increase in TK1 levels associated with the plasma membrane of cancer cells when compared to normal lymphocytes. After membrane separation the plasma membrane of normal lymphocytes showed a TK1 activity of 1,012 CPM/mg protein/hr(N=20) whereas those of cancer cells showed: Jurkat 34,096(N=28), Raji 70,195(N=20), HL60 46,217(N=34), and MDA-MB-435 50,359(N=24). In this study we sought to further investigate this association by visualizing the surface staining of fluorescently tagged antibodies to TK1. Using a primary rabbit anti-TK1 antibody and a secondary goat anti-rabbit antibody conjugated with a FITC fluorochrome we were able to stain the cells and identify TK1 bound to the cell surface. Using a fluorescent microscope we were able to visualize the fluorescent staining of TK1 in various cancer cell lines, including: Raji, Jurkat, HL60, MDA-MB-435, H358, and MCF-7. We compared these results to our control of stained normal lymphocytes, which showed significantly greater levels of staining in cancer cells. Our results further confirm the presence of membrane associated TK1, and provide further evidence of TK1's usefulness as a diagnostic marker and potential therapeutic target. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1678. doi:10.1158/1538-7445.AM2011-1678

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