Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.1.21 (thymidine kinase)
 7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The herpes simplex virus thymidine kinase gene (HSV-TK) in combination with ganciclovir (GCV), is currently being used in gene therapy-based clinical trials for cancer treatment. Its therapeutic effect is based on a "bystander effect" whereby HSV-TK gene-modified tumor cells are toxic to nearby unmodified tumor cells when exposed to the antiviral drug GCV. We have recently hypothesized that the in vivo mechanism of this bystander effect is due to alterations in the tumor microenvironment in response to release of cytokines and an infiltration of leukocytes after treatment with HSV-TK gene-modified tumor cells and GCV, which results in tumor regression. Expression of B7, a recently identified costimulatory molecule that is important for T-cell stimulation, has been shown to be modulated by stimulatory cytokines interferon-gamma, tumor necrosis factor-alpha, and inhibited by interleukin-10. In the present study, we investigated whether the cytokines released after HSV-TK and GCV treatment could include the expression of the costimulatory molecules B7-1 and B7-2 and the adhesion molecule (ICAM)-1 in the tumor. Furthermore, we investigated whether this altered environment affected the antitumor properties of host lymphocytes. An in vitro model was developed to establish the effects of HSV-TK gene-modified tumor cells and GCV on tumor infiltrating cells. The murine macrophage cell line (IC21) was exposed to either supernatants or cell lysates collected from a mixture of HSV-TK-transduced (KBALB-STK) and non-transduced (KBALB) murine fibrosarcoma tumor cells previously exposed to GCV (experimental). Immunohistochemical analysis showed a significant expression (P < .0001) of B7-1 and B7-2 post exposure of IC21 cells to either supernatant or lysate. In contrast, the level of expression in IC21 cells exposed to the control lysate or supernatant remained unchanged for B7-1 and B7-2. In vivo analysis for B7-1 and B7-2 expression by immunohistochemistry in tumor tissues from experimental mice receiving HSV-TK gene-modified tumor cells and GCV treatment showed a significant expression of B7.1 (35%, P < .0001) and B7.2 (38.2%, P < .0001) on tumor-infiltrating mononuclear cells. In contrast, tumor-bearing control animals showed low levels of B7-2 expression (5.8%), whereas B7-1 was undetectable, as confirmed by reverse-transcriptase polymerase chain reaction. In addition, a significant up-regulation of ICAM expression (50%) on tumor tissues was observed in the experimental group (P = .0317) as compared with the control group (25%). Furthermore, T cells isolated from experimental mice showed a significant in vitro proliferative response (p = .0202) when exposed to syngeneic tumor cells as compared with the control group. These data demonstrated that the use of HSV-TK gene-modified tumor cells and GCV as a suicide gene in the treatment of an intraperitoneal tumor resulted in the expression of the B7 costimulatory molecules and ICAM-1 adhesion molecule and enhanced proliferative response of host T cells. These findings help to understand the mechanism of tumor cell killing in vivo using HSV-TK gene-modified tumor cells.
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PMID:Expression of costimulatory molecules: B7 and ICAM up-regulation after treatment with a suicide gene. 898 40

In a cancer gene therapy model recombinant adenoviruses expressing the herpes simplex virus thymidine kinase (HSVtk) gene were injected into tumors in situ, either alone or in combination with adenoviruses (Avs) engineered to express IL-2, IL-6 or the costimulatory molecule B7-1. HSVtk phosphorylates the prodrug ganciclovir, thus converting it into an antimetabolite which kills not only HSVtk expressing cells, but also by the 'bystander effect', neighboring untransduced tumor cells. The tumors regressed in 80% of mice upon AvTK/ganciclovir treatment: combinations with AvIL-2, AvIL-6, or AvB7-1 did not improve these results. Cured mice were protected from further challenge with wild-type tumor but not from challenges with an unrelated syngeneic tumor cell line. Since cytotoxic T lymphocyte responses in this tumor model were weak, we analyzed cytokine secretion from spleen cells of treated animals. The best correlate of antitumor immunity in this model was enhanced secretion of GM-CSF, while secretion of IL-2, IL-6 and IFN gamma was also frequently increased but not as consistently. The enhanced IFN gamma secretion associated with unchanged IL-4 secretion suggests that AvTK treatment results in a predominantly Th1-mediated antitumor immune response.
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PMID:Characterization of the antitumor immune response generated by treatment of murine tumors with recombinant adenoviruses expressing HSVtk, IL-2, IL-6 or B7-1. 947 56

Imaging strategies to monitor chimeric antigen receptor (CAR) T-cell biodistribution and proliferation harbor the potential to facilitate clinical translation for the treatment of both liquid and solid tumors. In addition, the potential adverse effects of CAR T cells highlight the need for mechanisms to modulate CAR T-cell activity. The herpes simplex virus type 1 thymidine kinase (HSV1-tk) gene has previously been translated as a PET reporter gene for imaging of T-cell trafficking in patients with brain tumor. The HSV1-TK enzyme can act as a suicide gene of transduced cells through treatment with the prodrug ganciclovir. Here we report the molecular engineering, imaging, and ganciclovir-mediated destruction of B7H3 CAR T cells incorporating a mutated version of the HSV1-tk gene (sr39tk) with improved enzymatic activity for ganciclovir. The sr39tk gene did not affect B7H3 CAR T-cell functionality and in vitro and in vivo studies in osteosarcoma models showed no significant effect on B7H3 CAR T-cell antitumor activity. PET/CT imaging with 9-(4-[18F]-fluoro-3-[hydroxymethyl]butyl)guanine ([18F]FHBG) of B7H3-sr39tk CAR T cells in an orthotopic model of osteosarcoma revealed tumor homing and systemic immune expansion. Bioluminescence and PET imaging of B7H3-sr39tk CAR T cells confirmed complete tumor ablation with intraperitoneal ganciclovir administration. This imaging and suicide ablation system can provide insight into CAR T-cell migration and proliferation during clinical trials while serving as a suicide switch to limit potential toxicities. SIGNIFICANCE: This study showcases the only genetically engineered system capable of serving the dual role both as an effective PET imaging reporter and as a suicide switch for CAR T cells.
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PMID:PET Reporter Gene Imaging and Ganciclovir-Mediated Ablation of Chimeric Antigen Receptor T Cells in Solid Tumors. 3295 48