Thymidine Kinase Suicide Gene Research Articles

Hypoxia-directed tumor targeting of CRISPR-Cas9 and HSV-TK suicide gene therapy using lipid nanoparticles

Hypoxia is a characteristic feature of solid tumors that contributes to tumor aggressiveness and is associated with resistance to cancer therapy. The hypoxia inducible factor-1 (HIF-1) transcription factor complex mediates hypoxia-specific gene expression by binding to hypoxia-responsive element (HRE) sequences within the promoter of target genes. HRE-driven expression of therapeutic cargo has been widely explored as a strategy to achieve cancer-specific gene expression. By utilizing this system, we achieve hypoxia-specific expression of two therapeutically relevant cargo elements: the herpes simplex virus thymidine kinase (HSV-tk) suicide gene and the CRISPR-Cas9 nuclease. Using an expression vector containing five copies of the HRE derived from the vascular endothelial growth factor gene, we are able to show high transgene expression in cells in a hypoxic environment, similar to levels achieved using the cytomegalovirus (CMV) and CBh promoters. Furthermore, we are able to deliver our therapeutic cargo to tumor cells with high efficiency using plasmid-packaged lipid nanoparticles (LNPs) to achieve specific killing of tumor cells in hypoxic conditions while maintaining tight regulation with no significant changes to cell viability in normoxia.

CSIG-19. DISRUPTION OF DNA DAMAGE RESPONSE MODULATES THE EFFICACY OF LOCAL IMMUNOTHERAPIES IN EXPERIMENTAL GLIOMA

Abstract RATIONALE Herpes virus thymidine kinase (HSV-TK) suicide gene therapy is a well-established approach for in situ tumor cell killing after administration of ganciclovir (GCV), due to the induction of lethal DNA damage in HSV-TK expressing cells. Here we investigated the effects of HSV-TK gene delivery with a non-replicating serotype 5 adenovirus (AdTK) in murine glioblastoma models in combination with the ATR-inhibitor AZD6738 to disrupt the DNA damage response (DDR). METHODS We investigated the effects of disrupted DDR signaling on AdTK therapy in vitro using cytotoxicity, cytokine and flow cytometry assays in glioblastoma cell lines and in vivo with an orthotopic syngeneic murine glioblastoma model. Therapy response was monitored with MRI. Changes in the tumor microenvironment were analyzed with CyTOF. RESULTS The combination of AZD6738 with AdTK was synergistic in cytotoxicity assays, which was complemented by a significant increase of γH2AX foci. Complex modulations of the tumor microenvironment were observed with significantly reduced expression of PD-L1, MICA/B and the pro-tumorigenic cytokines IL1b and IL-4. In vivo, the combination with AZD6738 led to an increase in long-term surviving animals (66.7%) compared to GMCI (50%) and proved to be highly significant in contrast to untreated controls (p=0.0022). However, the combination treatment did not block the growth of tumors upon rechallenge in long-term survivors. CONCLUSION DDR signaling is crucial in the therapeutic efficacy of AdTK/GCV. It significantly enhances cytotoxicity in vitro and in vivo while having complex ramifications at the immunological level, requiring further studies to determine ideal conditions for a maximized therapeutic benefit.

Peptide-guided JC polyomavirus-like particles specifically target bladder cancer cells for gene therapy

The ultimate goal of gene delivery vectors is to establish specific and effective treatments for human diseases. We previously demonstrated that human JC polyomavirus (JCPyV) virus-like particles (VLPs) can package and deliver exogenous DNA into susceptible cells for gene expression. For tissue-specific targeting in this study, JCPyV VLPs were conjugated with a specific peptide for bladder cancer (SPB) that specifically binds to bladder cancer cells. The suicide gene thymidine kinase was packaged and delivered by SPB-conjugated VLPs (VLP-SPBs). Expression of the suicide gene was detected only in human bladder cancer cells and not in lung cancer or neuroblastoma cells susceptible to JCPyV VLP infection in vitro and in vivo, demonstrating the target specificity of VLP-SPBs. The gene transduction efficiency of VLP-SPBs was approximately 100 times greater than that of VLPs without the conjugated peptide. JCPyV VLPs can be specifically guided to target particular cell types when tagged with a ligand molecule that binds to a cell surface marker, thereby improving gene therapy.

Analysis of the suicide gene based-safeguard system for induced pluripotent stem cell-based therapy of Parkinson's disease

Objective: The use of human induced pluripotent stem cells (hiPSCs) and recent advances in cell engineering have opened new prospects for cell-based regeneration therapy. However, there are concerns that must be addressed prior to their broad clinical applications such as treatment for Parkinson's disease, and a major concern is tumorigenicity. We here generated knock-in hiPSCs to analyze the feasibility of the herpes simplex virus thymidine kinase (HSV-TK) suicide gene system as a safeguard against tumorigenicity.

A human Myogenin promoter modified to be highly active in alveolar rhabdomyosarcoma drives an effective suicide gene therapy

Rhabdomyosarcoma is a rare childhood soft tissue cancer whose cells resemble poorly differentiated skeletal muscle, expressing myogenic proteins including MYOGENIN. Alveolar rhabdomyosarcoma (ARMS) accounts for ~40% of cases and is associated with a poorer prognosis than other rhabdomyosarcoma variants, especially if containing the chromosomal translocation generating the PAX3-FOXO1 hybrid transcription factor. Metastasis is commonly present at diagnosis, with a five-year survival rate of <30%, highlighting the need for novel therapeutic approaches. We designed a suicide gene therapy by generating an ARMS-targeted promoter to drive the herpes simplex virus thymidine kinase (HSV-TK) suicide gene. We modified the minimal human MYOGENIN promoter by deleting both the NF1 and MEF3 transcription factor binding motifs to produce a promoter that is highly active in ARMS cells. Our bespoke ARMS promoter driving HSV-TK efficiently killed ARMS cells in vitro, but not skeletal myoblasts. Using a xenograft mouse model, we also demonstrated that ARMS promoter-HSV-TK causes apoptosis of ARMS cells in vivo. Importantly, combining our suicide gene therapy with standard chemotherapy agents used in the treatment of rhabdomyosarcoma, reduced the effective drug dose, diminishing deleterious side effects/patient burden. This modified, highly ARMS-specific promoter could provide a new therapy option for this difficult-to-treat cancer.

Gene Therapy Using Neural Stem/Progenitor Cells Derived from Human Induced Pluripotent Stem Cells: Visualization of Migration and Bystander Killing Effect.

Glioblastoma is the most aggressive brain tumor characterized by diffuse infiltration into the normal brain parenchyma. Neural stem cells are known to possess the tumor-tropic migratory capacity and thus can be used as cellular vehicles for targeted delivery of therapeutic agents. In the present study, we evaluated the efficacy of herpes simplex virus thymidine kinase (HSV-TK) suicide gene therapy for glioblastoma using neural stem/progenitor cells (NS/PCs) derived from human induced pluripotent stem cells (hiPSCs). Although transduction of hiPSCs is preferable for a safe and stable supply in the clinical setting, high-level and/or constitutive HSV-TK expression was highly cytotoxic to hiPSCs. To overcome this problem, we used the tetracycline-inducible system to control the expression of HSV-TK. hiPSC-derived NS/PCs expressing HSV-TK were transplanted in an orthotopic xenograft mouse model of human glioblastoma. Glioblastoma cell growth in mice was dramatically inhibited following ganciclovir (GCV) administration. Survival of the mice was significantly prolonged with administration of GCV compared with control groups. Time-lapse imaging of organotypic brain slice cultures first demonstrated the directional migration of NS/PCs toward glioblastoma cells and the bystander killing effect upon GCV treatment. hiPSC-derived NS/PCs with HSV-TK/GCV suicide gene system may have considerable therapeutic potential for the treatment of glioblastoma. Color images are available online.

Rapid Regulation of Human Mesenchymal Stem Cell Proliferation Using Inducible Caspase-9 Suicide Gene for Safe Cell-Based Therapy.

The regulation of transplanted cell proliferation and function is important to achieve safe cell-based therapies. We previously reported that the proliferation and function of transplanted cells, which expressed the herpes simplex virus thymidine kinase (HSVtk) suicide gene, could be controlled by ganciclovir (GCV) administration. However, there are some concerns regarding the use of GCV. It is reported that the inducible caspase-9 (iC9) gene, a human caspase-9-derived genetically engineered suicide gene, rapidly induces cell apoptosis in the presence of apoptosis inducers, such as AP20187. In this study, we used a combination of the iC9 gene and AP20187 to achieve rapid regulation of transplanted cell proliferation. Cells from the human mesenchymal stem cell line UE7T-13 were transfected with the iC9 gene to obtain UE7T-13/iC9 cells. AP20187 significantly reduced the number of UE7T-13/iC9 cells within 24 h in a concentration-dependent manner. This reduction was much faster than the reduction of HSVtk-expressing UE7T-13 cells induced by GCV addition. Subcutaneous AP20187 administration rapidly reduced the luminescence signal from NanoLuc luciferase (Nluc)-expressing UE7T-13/iC9 cells transplanted into mice. These results indicate that the combined use of the iC9 gene and AP20187 is effective in rapidly regulating transplanted cell proliferation.

Retraction of "Glioma Gene Therapy Using Induced Pluripotent Stem Cell Derived Neural Stem Cells".

Using neural stem cells (NSCs) with tumor tropic migratory capacity to deliver therapeutic genes is an attractive strategy in eliminating metastatic or disseminated tumors. While different methods have been developed to isolate or generate NSCs, it has not been assessed whether induced pluripotent stem (iPS) cells, a type of pluripotent stem cells that hold great potential for regenerative medicine, can be used as a source for derivation of NSCs with tumor tropism. In this study, we used a conventional lentivirus transduction method to derive iPS cells from primary mouse embryonic fibroblasts and then generated NSCs from the iPS cells. To investigate whether the iPS cell derived NSCs can be used in the treatment of disseminated brain tumors, the cells were transduced with a baculoviral vector containing the herpes simplex virus thymidine kinase suicide gene and injected into the cerebral hemisphere contralateral to a tumor inoculation site in a mouse intracranial human glioma xenograft model. We observed that NSCs expressing the suicide gene were, in the presence of ganciclovir, effective in inhibiting the growth of the glioma xenografts and prolonging survival of tumor-bearing mice. Our findings provide evidence for the feasibility of using iPS cell derived NSCs as cellular vehicles for targeted anticancer gene therapy.

Gene therapy for castration-resistant prostate cancer cells using JC polyomavirus-like particles packaged with a PSA promoter driven-suicide gene.

Prostate cancer is the second most common cancer in men globally. Prostate cancer patients at advanced stages are usually treated with androgen deprivation therapy (ADT). However, with disease progression, it often becomes the incurable castration-resistant prostate cancer (CRPC). JC polyomavirus (JCPyV) is a human DNA virus. Its virus-like particles (VLPs) exhibit similar tropism to native virions and they are capable of delivering exogenous genes to the target cells for expression. JCPyV has been detected in prostate cells; therefore, prostate cancer cells may be susceptible to JCPyV infection and JCPyV VLPs may be used as a vector for gene therapy against prostate cancer. Here we constructed a plasmid (pPSAtk) that allows expression of the thymidine kinase suicide gene only in androgen receptor (AR) positive prostate cancer cells using the prostate-specific antigen (PSA) promoter, and used JCPyV VLPs as a vector to carry pPSAtk (PSAtk-VLPs) for transcriptional targeting in prostate cancer cells. In this study, we found that PSAtk-VLPs could only kill AR-positive CRPC 22Rv1 cells in vitro and inhibit the growth of tumor nodules in the xenograft mouse model. Our results reveal that PSAtk-VLPs could potentially be used as a new option for treating CRPC patients in the future.

Selective killing of spinal cord neural stem cells impairs locomotor recovery in a mouse model of spinal cord injury

BackgroundSpinal cord injury (SCI) is a devastating condition mainly deriving from a traumatic damage of the spinal cord (SC). Immune cells and endogenous SC-neural stem cells (SC-NSCs) play a critical role in wound healing processes, although both are ineffective to completely restore tissue functioning. The role of SC-NSCs in SCI and, in particular, whether such cells can interplay with the immune response are poorly investigated issues, although mechanisms governing such interactions might open new avenues to develop novel therapeutic approaches.MethodsWe used two transgenic mouse lines to trace as well as to kill SC-NSCs in mice receiving SCI. We used Nestin CreERT2 mice to trace SC-NSCs descendants in the spinal cord of mice subjected to SCI. While mice carrying the suicide gene thymidine kinase (TK) along with the GFP reporter, under the control of the Nestin promoter regions (NestinTK mice) were used to label and selectively kill SC-NSCs.ResultsWe found that SC-NSCs are capable to self-activate after SCI. In addition, a significant worsening of clinical and pathological features of SCI was observed in the NestinTK mice, upon selective ablation of SC-NSCs before the injury induction. Finally, mice lacking in SC-NSCs and receiving SCI displayed reduced levels of different neurotrophic factors in the SC and significantly higher number of M1-like myeloid cells.ConclusionOur data show that SC-NSCs undergo cell proliferation in response to traumatic spinal cord injury. Mice lacking SC-NSCs display overt microglia activation and exaggerate expression of pro-inflammatory cytokines. The absence of SC-NSCs impaired functional recovery as well as neuronal and oligodendrocyte cell survival. Collectively our data indicate that SC-NSCs can interact with microglia/macrophages modulating their activation/responses and that such interaction is importantly involved in mechanisms leading tissue recovery.

Gene therapy for human glioblastoma using neurotropic JC virus-like particles as a gene delivery vector

Glioblastoma multiforme (GBM), the most common malignant brain tumor, has a short period of survival even with recent multimodality treatment. The neurotropic JC polyomavirus (JCPyV) infects glial cells and oligodendrocytes and causes fatal progressive multifocal leukoencephalopathy in patients with AIDS. In this study, a possible gene therapy strategy for GBM using JCPyV virus-like particles (VLPs) as a gene delivery vector was investigated. We found that JCPyV VLPs were able to deliver the GFP reporter gene into tumor cells (U87-MG) for expression. In an orthotopic xenograft model, nude mice implanted with U87 cells expressing the near-infrared fluorescent protein and then treated by intratumoral injection of JCPyV VLPs carrying the thymidine kinase suicide gene, combined with ganciclovir administration, exhibited significantly prolonged survival and less tumor fluorescence during the experiment compared with controls. Furthermore, JCPyV VLPs were able to protect and deliver a suicide gene to distal subcutaneously implanted U87 cells in nude mice via blood circulation and inhibit tumor growth. These findings show that metastatic brain tumors can be targeted by JCPyV VLPs carrying a therapeutic gene, thus demonstrating the potential of JCPyV VLPs to serve as a gene therapy vector for the far highly treatment-refractory GBM.

Surfactant protein C dampens inflammation by decreasing JAK/STAT activation during lung repair.

Surfactant protein C (SPC), a key component of pulmonary surfactant, also plays a role in regulating inflammation. SPC deficiency in patients and mouse models is associated with increased inflammation and delayed repair, but the key drivers of SPC-regulated inflammation in response to injury are largely unknown. This study focuses on a new mechanism of SPC as an anti-inflammatory molecule using SPC-TK/SPC-KO (surfactant protein C-thymidine kinase/surfactant protein C knockout) mice, which represent a novel sterile injury model that mimics clinical acute respiratory distress syndrome (ARDS). SPC-TK mice express the inducible suicide gene thymidine kinase from by the SPC promoter, which targets alveolar type 2 (AT2) cells for depletion in response to ganciclovir (GCV). We compared GCV-induced injury and repair in SPC-TK mice that have normal endogenous SPC expression with SPC-TK/SPC-KO mice lacking SPC expression. In contrast to SPC-TK mice, SPC-TK/SPC-KO mice treated with GCV exhibited more severe inflammation, resulting in over 90% mortality; there was only 8% mortality of SPC-TK animals. SPC-TK/SPC-KO mice had highly elevated inflammatory cytokines and granulocyte infiltration in the bronchoalveolar lavage (BAL) fluid. Consistent with a proinflammatory phenotype, immunofluorescence revealed increased phosphorylated signal transduction and activation of transcription 3 (pSTAT3), suggesting enhanced Janus kinase (JAK)/STAT activation in inflammatory and AT2 cells of SPC-TK/SPC-KO mice. The level of suppressor of cytokine signaling 3, an anti-inflammatory mediator that decreases pSTAT3 signaling, was significantly decreased in the BAL fluid of SPC-TK/SPC-KO mice. Hyperactivation of pSTAT3 and inflammation were rescued by AZD1480, a JAK1/2 inhibitor. Our findings showing a novel role for SPC in regulating inflammation via JAK/STAT may have clinical applications.

ExVivo Selection of Transduced Hematopoietic Stem Cells for Gene Therapy of β-Hemoglobinopathies.

Although gene transfer to hematopoietic stem cells (HSCs) has shown therapeutic efficacy in recent trials for several individuals with inherited disorders, transduction incompleteness of the HSC population remains a hurdle to yield a cure for all patients with reasonably low integrated vector numbers. In previous attempts at HSC selection, massive loss of transduced HSCs, contamination with non-transduced cells, or lack of applicability to large cell populations has rendered the procedures out of reach for human applications. Here, we fused codon-optimized puromycin N-acetyltransferase to herpes simplex virus thymidine kinase. When expressed from a ubiquitous promoter within a complex lentiviral vector comprising the βAT87Q-globin gene, viral titers and therapeutic gene expression were maintained at effective levels. Complete selection and preservation of transduced HSCs were achieved after brief exposure to puromycin in the presence of MDR1 blocking agents, suggesting the procedure’s suitability for human clinical applications while affording the additional safety of conditional suicide.

Clinical effect of recombinant adenovirus containing thymidine kinase suicide gene in preventing postoperative recurrence of hepatocellular carcinoma

Clinical effect of recombinant adenovirus containing thymidine kinase suicide gene in preventing postoperative recurrence of hepatocellular carcinoma

A murine model of suicide gene therapy in the brainstem demonstrates efficacy without toxic inflammation, suggesting possible use as a treatment for diffuse intrinsic pontine glioma (DIPG)

Abstract Diffuse intrinsic pontine glioma (DIPG) is a rare pediatric brainstem tumor that is the leading cause of death among pediatric brain malignancies. Despite over 200 clinical trials, no significant progress has been made, leading our lab to consider suicide gene therapy. The brainstem has particularly sensitive anatomy, creating the potential for toxic inflammation. Furthermore, the clinical standard of care for DIPG includes conventional radiation therapy (RT) followed by dexamethasone (DEX), each of which can alter the efficacy of gene therapy. In this study we found that a variety of gliomas, including human DIPG and murine glioma cell lines, are infectable in vitro with a replication-competent Moloney murine leukemia virus (MoMLV) (currently in Phase 2/3 clinical trials) and susceptible to ganciclovir (GCV)-mediated killing via the HSV thymidine kinase (tk) suicide gene. A B16 melanoma cell line expressing HSV tk implanted into the brainstem of mice, extended median survival with GCV therapy from 13 days to 38.5 days (p=.0006) with no signs of toxic inflammation. Pre-treatment with RT and DEX did not affect therapeutic efficacy. We have shown that GCV/TK therapy is mediated by NK and CD8 cells in subcutaneous tumors, and we are investigating whether a similar immunologic mechanism is involved in this brainstem model. These preclinical data will pave the way for novel clinical trials for the treatment of DIPG.

Disclosing the Parameters Leading to High Productivity of Retroviral Producer Cells Lines: Evaluating Random Versus Targeted Integration.

Gammaretrovirus and lentivirus are the preferred viral vectors to genetically modify T and natural killer cells to be used in immune cell therapies. The transduction efficiency of hematopoietic and T cells is more efficient using gibbon ape leukemia virus (GaLV) pseudotyping. In this context gammaretroviral vector producer cells offer competitive higher titers than transient lentiviral vectors productions. The main aim of this work was to identify the key parameters governing GaLV-pseudotyped gammaretroviral vector productivity in stable producer cells, using a retroviral vector expression cassette enabling positive (facilitating cell enrichment) and negative cell selection (allowing cell elimination). The retroviral vector contains a thymidine kinase suicide gene fused with a ouabain-resistant Na+,K+-ATPase gene, a potential safer and faster marker. The establishment of retroviral vector producer cells is traditionally performed by randomly integrating the retroviral vector expression cassette codifying the transgene. More recently, recombinase-mediated cassette exchange methodologies have been introduced to achieve targeted integration. Herein we compared random and targeted integration of the retroviral vector transgene construct. Two retroviral producer cell lines, 293 OuaS and 293 FlexOuaS, were generated by random and targeted integration, respectively, producing high titers (on the order of 107 infectious particles·ml-1). Results showed that the retroviral vector transgene cassette is the key retroviral vector component determining the viral titers notwithstanding, single-copy integration is sufficient to provide high titers. The expression levels of the three retroviral constructs (gag-pol, GaLV env, and retroviral vector transgene) were analyzed. Although gag-pol and GaLV env gene expression levels should surpass a minimal threshold, we found that relatively modest expression levels of these two expression cassettes are required. Their levels of expression should not be maximized. We concluded, to establish a high producer retroviral vector cell line only the expression level of the genomic retroviral RNA, that is, the retroviral vector transgene cassette, should be maximized, both through (1) the optimization of its design (i.e., genetic elements composition) and (2) the selection of high expressing chromosomal locus for its integration. The use of methodologies identifying and promoting integration into high-expression loci, as targeted integration or high-throughput screening are in this perspective highly valuable.

Selective elimination of long INterspersed element-1 expressing tumour cells by targeted expression of the HSV-TK suicide gene.

In gene therapy, effective and selective suicide gene expression is crucial. We exploited the endogenous Long INterspersed Element-1 (L1) machinery often reactivated in human cancers to integrate the Herpes Simplex Virus Thymidine Kinase (HSV-TK) suicide gene selectively into the genome of cancer cells. We developed a plasmid-based system directing HSV-TK expression only when reverse transcribed and integrated in the host genome via the endogenous L1 ORF1/2 proteins and an Alu element. Delivery of these new constructs into cells followed by Ganciclovir (GCV) treatment selectively induced mortality of L1 ORF1/2 protein expressing cancer cells, but had no effect on primary cells that do not express L1 ORF1/2. This novel strategy for selective targeting of tumour cells provides high tolerability as the HSV-TK gene cannot be expressed without reverse transcription and integration, and high selectivity as these processes take place only in cancer cells expressing high levels of functional L1 ORF1/2.

Allogeneic Genetically Modified T Cells (HSV-TK) As Adjunctive Treatment in Haploidentical Hematopoietic Stem-Cell Transplantation (haplo-HSCT) of Adult Patients with High-Risk Hematological Malignancies: A Pair-Matched Analysis from the Acute Leukemia Working Party of EBMT

Introduction. Current approaches to haplo-HSCT rely either on T-cell depletion to overcome the HLA disparity or on the administration of the lymphotoxic agent cyclophosphamide several days after stem cell infusion, with the goal of selectively depleting activated alloreactive lymphocytes in vivo. In both approaches, haplo-HSCT can be associated with prolonged immunodeficiency post-transplantation. Thus, effective approaches to hastening immune reconstitution following transplantation are needed. Zalmoxis¨ is an Advanced Therapy Medicinal Product based on somatic T-cells genetically modified to express the Herpes Simplex Thymidine Kinase (HSV-TK) suicide gene and a truncated form of the human Low Affinity Nerve Growth Factor Receptor (ΔLNGFR) genes (for identification of transduced cells). The expression of the HSV-TK gene, as a suicide gene allows the selective killing of dividing cells upon administration of the pro-drug ganciclovir (GCV). If GvHD occurs, ganciclovir/valganciclovir can be administered. Here we report the results of a pair-matched analysis which compared the outcome of patients who received HSV-TK cells infusion post haplo-HSCT versus those who did not receive any cellular therapy post-transplant.Patients and Methods. The HSV-TK patients' group included 45 patients who were treated as part of 2 prospective trials with various types of high-risk hematologic malignancies. These patients were compared to patients treated with haplo-HSCT reported to the acute leukemia working party registry of the EBMT. Inclusion criteria for the pair-matched analysis encompassed haplo-HSCT transplants performed in adult patients diagnosed with AML/ALL/sAML in CR or relapse at transplantation. To equate the distribution of baseline characteristics between the HSV-TK and control group and to reduce bias in treatment effect estimation, a pair-matched analysis was performed.This analysis, in which pairs of HSV-TK and control subjects sharing similar baseline characteristics were formed, used the following parameters as pair matching factors: patient age, diagnosis (AML, ALL and sAML), disease status at HSCT (CR1, CR2, CR3 or relapse) and time from diagnosis to HSCT. The planned ratio of HSV-TK patients to control patients was one to four. Efficacy outcome measures of this pair-matched analysis were OS, LFS, NRM and relapse incidence (RI). Cumulative incidence rates of chronic GVHD were also analyzed.Results. Overall, 37 HSV-TK-treated patients matched with 140 controls (71 from PT-Cy cohort and 69 from TCD cohort transplanted between 2005 and 2013). The recommended dose and schedule of HSV-TK cells was 1x107 cells/kg given as IV infusion every 30 days for a maximum of 4 times until a circulating T-cell count higher than 100 per μL. The 1st administration should occur between day 21 to day 49 after HSCT. Baseline characteristics of the HSV-TK treated and the control patient population are summarized in the below table.OS at 1-year was significantly improved in the HSV-TK-group compared with the control group (p=0.01). The survival rates were 49% and 37% for HSV-TK- and control group, respectively. The NRM at 1-year was also improved upon treatment with HSV-TK, with 43% for the control group and 22% for the HSV-TK-group (p=0.014). A difference in favor of the HSV-TK-group could also be observed for the 1-year incidence of chronic GvHD with 25% for the control group vs 9% for the HSV-TK-group (p=0.04). The LFS and the RI were not different between the groups. Interestingly, these differences remained similar whether considering the TCD or the PT-CY subgroups). Together the data suggest that the benefit seen in OS is driven by a reduction in the NRM. A further analysis of NRM data revealed that in the control group 34 of 140 (24%) patients died due to infection and 8 of 140 (6%) succumbed due to GvHD. In the HSV-TK population 4 (11%) patients died because of infection and no patient died due to GvHD. This suggests that the reduction in NRM mortality in the HSV-TK population is caused both by a reduction in death due to infection and due to GvHD. Concerning safety, no death was attributed to HSV-TK cells. Acute GvHD resolved in all cases, and activation of the suicide gene by treatment with GCV has contributed to the control of GvHD.Conclusion. The above pair-matched analyzis confirmed the positive impact and benefit of HSV-TK cells as adjunctive treatment in haplo-HSCT with an acceptable safety pattern. [Display omitted] DisclosuresBonini:Molmed SpA: Consultancy; TxCell: Membership on an entity's Board of Directors or advisory committees. Ciceri:MolMed SpA: Consultancy.

Gene Therapy for Human Lung Adenocarcinoma Using a Suicide Gene Driven by a Lung-Specific Promoter Delivered by JC Virus-Like Particles.

Lung adenocarcinoma, the most commonly diagnosed type of lung cancer, has a poor prognosis even with combined surgery, chemotherapy, or molecular targeted therapies. Most patients are diagnosed with an in-operable advanced or metastatic disease, both pointing to the necessity of developing effective therapies for lung adenocarcinoma. Surfactant protein B (SP-B) has been found to be overexpressed in lung adenocarcinoma. In addition, it has also been demonstrated that human lung adenocarcinoma cells are susceptible to the JC polyomavirus (JCPyV) infection. Therefore, we designed that the JCPyV virus-like particle (VLP) packaged with an SP-B promoter–driven thymidine kinase suicide gene (pSPB-tk) for possible gene therapy of human lung adenocarcinoma. Plasmids expressing the GFP (pSPB-gfp) or thymidine kinase gene (pSPB-tk) under the control of the human SP-B promoter were constructed. The promoter’s tissue specificity was tested by transfection of pSPB-gfp into A549, CH27, and H460 human lung carcinoma cells and non-lung cells. The JCPyV VLP’s gene transfer efficiency and the selective cytotoxicity of pSPB-tk combined with ganciclovir (GCV) were tested in vitro and in a xenograft mouse model. In the current study, we found that SP-B promoter–driven GFP was specifically expressed in human lung adenocarcinoma (A549) and large cell carcinoma (H460) cells. JCPyV VLPs were able to deliver a GFP reporter gene into A549 cells for expression. Selective cytotoxicity was observed in A549 but not non-lung cells that were transfected with pSPB-tk or infected with pSPB-tk–carrying JCPyV VLPs. In mice injected with pSPB-tk–carrying JCPyV VLPs through the tail vein and treated with ganciclovir (GCV), a potent 80% inhibition of growth of human lung adenocarcinoma nodules resulted. The JCPyV VLPs combined with the use of SP-B promoter demonstrates effectiveness as a potential gene therapy against human lung adenocarcinoma.

A double suicide gene system driven by vascular endothelial growth factor promoter selectively kills human hepatocellular carcinoma cells.

The aim of the present study was to investigate the selective killing effect on hepatocellular carcinoma (HCC) cells of an adenovirus (Ad)-mediated cytosine deaminase (CD) in combination with thymidine kinase (TK) suicide gene system, driven by the vascular endothelial growth factor promoter (VEGFp), in vitro and in vivo. A double suicide gene system with VEGFp, named Ad-VEGFp-CDglyTK, was constructed and transfected into human HCC cells (BEL-7402 or HepG2; the latter cell type is deficient in VEGF) and human umbilical vein vascular endothelial cells (HUVEC). Green fluorescent protein expression was detected by fluoroscopy to verify transfection efficiency, and CDglyTK gene expression was detected by reverse transcription-polymerase chain reaction (PCR). The selective killing effect of Ad-VEGFp-CDglyTK was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and flow cytometry (FCM) in vitro and by xenograft studies in vivo. PCR revealed that the transgenic CDglyTK gene was expressed in BEL-7402 cells and HUVEC, but not in HepG2 cells. The cell survival rate significantly decreased in line with increasing concentrations of the prodrugs, ganciclovir (GCV) alone, 5-fluorocytosine (5-FC) alone or a combination of the two, in HUVEC and BEL-7402 cells with the transfected CDglyTK gene, but not in untransfected HUVEC or BEL-7402 cells, or in transfected or untransfected HepG2 cells. This result was additionally confirmed by FCM. GCV and 5-FC inhibited the HUVEC and BEL-7402 cells containing the transfected CDglyTK gene and also inhibited adjacent unmodified cells via the 'bystander effect'. No similar results were observed in HepG2 cells. Compared with the control group, tumors with the transfected CDglyTK gene were smaller and the microvessel density of the tumor tissue was significantly decreased. It was concluded that a combination TK/GCV and CD/5-FC suicide gene system driven by VEGFp may provide a promising treatment strategy for HCC.