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Breast cancer is one of the most common cancers in women. One of the best therapeutic methods against breast cancer is gene therapy, while having an appropriate gene carrier is the biggest challenge of gene therapy. Hence, developing carriers with low cytotoxicity and high gene transfection efficiency, and preferentially with the selective function of gene delivery is a critical demand for this method. In the present study, we introduce a novel targeted carrier to deliver the inducible caspase-9 suicide gene (pLVSIN-iC9) into breast cancer cells. The carrier is composed of graphene oxide quantum dots decorated with polyethyleneimine, and S2.2; an aptamer with high affinity to MUC1 (GOQD-PEI/S2.2). Due to the overexpression of MUC1 in breast cancer cells, the designed GOQD-PEI/S2.2/pLVSIN-iC9 can selectively target cancer cells. Moreover, to better mimic solid tumor conditions, and to evaluate the selective effect of the GOQD-PEI/S2.2/pLVSIN-iC9, an organoid model derived from human dermal fibroblasts (HDF) and MCF-7 cells (coculture organoid) was generated and characterized. The results demonstrate that the coculture organoid model adapts the tissue structure of luminal breast cancer, as well. Therefore, the organoids were subjected to treatment with targeted gene therapy using GOQD-PEI/S2.2/pLVSIN-iC9. Our evidence supports the targeted killing effect of iC9 on the breast cancer cells of the organoids and suggests the good potential of the newly introduced carriers in targeted gene delivery.

Chimeric antigen receptor T (CAR-T) cell therapy is an emerging and effective cancer immunotherapy. Especially in hematological malignancies, CAR-T cells have achieved exciting results. Two Anti-CD19 CAR-T therapies have been approved for the treatment of CD19-positive leukemia or lymphoma. However, the application of CAR-T cells is obviously hampered by the adverse effects, such as cytokines release syndrome and on-target off-tumor toxicity. In some clinical trials, patients quitted the treatment of CAR-T cells due to life-threatening toxicity. Seeking to alleviate these toxicities or prevent the occurrence, researchers have developed a number of safety strategies of CAR-T cells, including suicide genes, synthetic Notch receptor, on-switch CAR, combinatorial target-antigen recognition, bispecific T cell engager and inhibitory CAR. This review summarized the preclinical studies and clinical trials of the safety strategies of CAR-T cells and their respective strengths and weaknesses.

PurposeTo investigate the synergistic effect of resveratrol on the bystander effect of TK/GCV suicide gene system in melanoma cells.MethodsThe effect of resveratrol on the growth of B16 cells and the synergistic effect of resveratrol with or without GCV were detected by MTT assay and high content screening assay. The effect of resveratrol on GJIC function was detected by flow cytometry combined with fluorescence tracer and fluorescence microscope, and the expression of gap junction protein was detected by western blotting. Synergistic killing effect of resveratrol plus TK/GCV was tested in vivo using transplanted melanoma model.ResultsIn vitro, resveratrol can enhanced GJ function and upregulated Cx32 and Cx43 protein expression in B16 cells. Resveratrol synergized with GCV to kill mixed B16 melanoma cells (20% TK+ cells and 80% TK− cells) and to improve apoptosis rate of TK− cells (the bystander effect of TK system), and the synergistic action was reversed by the GJ inhibitor AGA. In vivo, when B16 cells were mixed with 30% TK+ B16 cells, significantly reduced tumor weight and volume were observed after combinational treatment with resveratrol plus GCV as compared with GCV or resveratrol treatment alone.ConclusionsResveratrol could synergistically enhance the killing effect of TK/GCV suicide gene system in melanoma B16 cells and transplanted melanoma. It might be a promising adjuvant of TK/GCV therapy.

Background Human mesenchymal stem cell (MSC)-based tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) gene delivery is regarded as an effective treatment for glioblastoma (GBM). However, adverse-free target site homing of the delivery vehicles to the tumor microsatellite nests is challenging, leading to erroneously sustained released of this suicide protein into the normal brain parenchyma; therefore, limiting off-target cytotoxicity and controlled expression of the suicide inductor is a prerequisite for the safe use of therapeutic stem cells. Methods Utilizing the intrinsic expression profile of GBM and its elevated expression of TGF-β relative to normal brain tissue, we sought to engineer human adipose-derived MSCs (hAMSC-SBE4-TRAIL) which augment the expression of TRAIL under the trigger of TGF-β signaling. We validated our therapeutic technology in a series of functional in vitro and in vivo assays using primary patient-derived GBM models. Results Our current findings show that these biologic delivery vehicles have high tumor tropism efficacy and expression TRAIL gene under the trigger of TGF-β-secreting GBMs, as well as avoid unspecific TRAIL secretion into normal brain tissue. hAMSC-SBE4-TRAIL inhibited the proliferation and induced apoptosis in experimental GBMs both in vitro and in vivo. In addition, our improved platform of engineered MSCs significantly decreased the tumor volume and prolonged survival time in a murine model of GBM. Conclusions Our results on the controlled release of suicide inductor TRAIL by exploiting an endogenous tumor signaling pathway demonstrate a significant improvement for the clinical utility of stem cell-mediated gene delivery to treat brain cancers. Harvesting immune-compatible MSCs from patients’ fat by minimally invasive procedures further highlights the clinical potential of this approach in the vision of applicability in a personalized manner. The hAMSC-SBE4-TRAIL exhibit great curative efficacy and are a promising cell-based treatment option for GBM to be validated in clinical exploration.

Reducing the pool of HIV-1 reservoirs in patients is a must to achieve functional cure. The most prominent HIV-1 cell reservoirs are resting CD4 + T cells and brain derived microglial cells. Infected microglial cells are believed to be the source of peripheral tissues reseedings and the emergence of drug resistance. Clearing infected cells from the brain is therefore crucial. However, many characteristics of microglial cells and the central nervous system make extremely difficult their eradication from brain reservoirs. Current methods, such as the “shock and kill”, the “block and lock” and gene editing strategies cannot override these difficulties. Therefore, new strategies have to be designed when considering the elimination of brain reservoirs. We set up an original gene suicide strategy using latently infected microglial cells as model cells. In this paper we provide proof of concept of this strategy.

Oncolytic adenovirus-mediated suicide gene therapy has been shown to improve local tumor control in preclinical tumor models and in the clinic. Although local tumor control is important, for most human cancers, new therapies must also target metastatic disease if they are to have an impact on survival. Here, we test the hypothesis that adding cytokine gene therapy to our multimodal platform improves both local and metastatic tumor control in a preclinical model of prostate cancer. An oncolytic adenovirus (Ad5-yCD/ mut TK SR39 rep -mIL12) expressing two suicide genes and mouse interleukin-12 (IL-12) was generated. Relative to an adenovirus lacking IL-12 (Ad5-yCD/ mut TK SR39 rep ), Ad5-yCD/ mut TK SR39 rep -mIL12 improved local and metastatic tumor control in the TRAMP-C2 prostate adenocarcinoma model, resulting in a significant increase in survival. Ad5-yCD/ mut TK SR39 rep -mIL12 resulted in high levels of IL-12 and interferon gamma in serum and tumor, increased natural killer (NK) and cytotoxic T-lymphocyte lytic activities, and the development of tumor-specific antitumor immunity. Immune cell depletion studies indicated that both the innate and adaptive arms of immunity were required for maximal Ad5-yCD/ mut TK SR39 rep -mIL12 activity. The results demonstrate that the addition of IL-12 significantly improves the efficacy of oncolytic adenovirus-mediated suicide gene therapy and provide the scientific basis for future trials targeting locally aggressive cancers.

Suicide gene therapy is a relatively novel form of cancer therapy in which a gene coding for enzymes or protein toxins is delivered through targeting systems such as vesicles, nanoparticles, peptide or lipidic co-adjuvants. The use of toxin genes is particularly interesting since their catalytic activity can induce cell death, damaging in most cases the translation machinery (ribosomes or protein factors involved in protein synthesis) of quiescent or proliferating cells. Thus, toxin gene delivery appears to be a promising tool in fighting cancer. In this review we will give an overview, describing some of the bacterial and plant enzymes studied so far for their delivery and controlled expression in tumor models.

The use of human induced pluripotent stem cells (hiPSCs) and recent advances in cell engineering have opened new prospects for cell‐based therapy. However, there are concerns that must be addressed prior to their broad clinical applications and a major concern is tumorigenicity. Suicide gene approaches could eliminate wayward tumor‐initiating cells even after cell transplantation, but their efficacy remains controversial. Another concern is the safety of genome editing. Our knowledge of human genomic safe harbors (GSHs) is still insufficient, making it difficult to predict the influence of gene integration on nearby genes. Here, we showed the topological architecture of human GSH candidates, AAVS1, CCR5, human ROSA26, and an extragenic GSH locus on chromosome 1 (Chr1‐eGSH). Chr1‐eGSH permitted robust transgene expression, but a 2 Mb‐distant gene within the same topologically associated domain showed aberrant expression. Although knockin iPSCs carrying the suicide gene, herpes simplex virus thymidine kinase (HSV‐TK), were sufficiently sensitive to ganciclovir in vitro, the resulting teratomas showed varying degrees of resistance to the drug in vivo. Our findings suggest that the Chr1‐eGSH is not suitable for therapeutic gene integration and highlight that topological analysis could facilitate exploration of human GSHs for regenerative medicine applications. Our data indicate that the HSV‐TK/ganciclovir suicide gene approach alone may be not an adequate safeguard against the risk of teratoma, and suggest that the combination of several distinct approaches could reduce the risks associated with cell therapy. Stem Cells Translational Medicine 2019;8:627&638 Tumorigenesis and the risks associated with genome editing are major concerns of human induced pluripotent stem cells‐based therapies. In this report, we list the features of human genome safe harbor candidates and demonstrate that topological analysis facilitates prediction of the influence of genome editing. We also suggest that the herpes simplex virus thymidine kinase suicide gene system alone would not be an adequate safeguard.

Pancreatic cancer (PC) is one of the most lethal cancers worldwide, associated with poor prognosis and restricted therapeutic options. Clostridium perfringens enterotoxin (CPE), is a pore-forming (oncoleaking) toxin, which binds to claudin-3 and -4 (Cldn3/4) causing selective cytotoxicity. Cldn3/4 are highly upregulated in PC and represent an effective target for oncoleaking therapy. We utilized a translation-optimized CPE vector (optCPE) for new suicide approach of PC in vitro and in cell lines (CDX) and patient-derived pancreatic cancer xenografts (PDX) in vivo. The study demonstrates selective toxicity in Cldn3/4 overexpressing PC cells by optCPE gene transfer, mediated by pore formation, activation of apoptotic/necrotic signaling in vitro, induction of necrosis and of bystander tumor cell killing in vivo. The optCPE non-viral intratumoral in vivo jet-injection gene therapy shows targeted antitumoral efficacy in different CDX and PDX PC models, leading to reduced tumor viability and induction of tumor necrosis, which is further enhanced if combined with chemotherapy. This selective oncoleaking suicide gene therapy improves therapeutic efficacy in pancreas carcinoma and will be of value for better local control, particularly of unresectable or therapy refractory PC.

T lymphocytes expressing a chimeric antigen receptor (CAR) targeting the CD19 antigen (CAR.19) may be of value for the therapy of B-cell malignancies. Because the in vivo survival, expansion and anti-lymphoma activity of CAR.19 + T cells remain suboptimal even when the CAR contains a CD28 costimulatory endodomain, we generated a novel construct that also incorporates the interleukin-15 (IL-15) gene and an inducible caspase-9-based suicide gene (iC9/CAR.19/IL-15). We found that compared with CAR.19 + T cells, iC9/CAR.19/IL-15 + T cells had: (1) greater numeric expansion upon antigen stimulation (10-fold greater expansion in vitro , and 3- to 15-fold greater expansion in vivo ) and reduced cell death rate (Annexin-V + /7-AAD + cells 10±6% for iC9/CAR.19/IL-15 + T cells and 32±19% for CAR.19 + T cells); (2) reduced expression of the programmed death 1 (PD-1) receptor upon antigen stimulation (PD-1 + cells <15% for iC9/CAR.19/IL-15 + T cells versus >40% for CAR.19 + T cells); and (3) improved antitumor effects in vivo (from 4.7- to 5.4-fold reduced tumor growth). In addition, iC9/CAR.19/IL-15 + T cells were efficiently eliminated upon pharmacologic activation of the suicide gene. In summary, this strategy safely increases the anti-lymphoma/leukemia effects of CAR.19-redirected T lymphocytes and may be a useful approach for treatment of patients with B-cell malignancies.