Origins of Suicide Gene Therapy

Nanotechnology and bioengineering approaches to improve the potency of mesenchymal stem cell as an off-the-shelf versatile tumor delivery vehicle

Targeting actionable mutations in oncogene-driven cancers and the evolution of immuno-oncology are the two prominent revolutions that have influenced cancer treatment paradigms and caused the emergence of precision oncology. However, intertumoral and intratumoral heterogeneity are the main challenges in both fields of precision cancer treatment. In other words, finding a universal marker or pathway in patients suffering from a particular type of cancer is challenging. Therefore, targeting a single hallmark or pathway with a single targeted therapeutic will not be efficient for fighting against tumor heterogeneity. Mesenchymal stem cells (MSCs) possess favorable characteristics for cellular therapy, including their hypoimmune nature, inherent tumor-tropism property, straightforward isolation, and multilineage differentiation potential. MSCs can be loaded with various chemotherapeutics and oncolytic viruses. The combination of these intrinsic features with the possibility of genetic manipulation makes them a versatile tumor delivery vehicle that can be used for in vivo selective tumor delivery of various chemotherapeutic and biological therapeutics. MSCs can be used as biofactory for the local production of chemical or biological anticancer agents at the tumor site. MSC-mediated immunotherapy could facilitate the sustained release of immunotherapeutic agents specifically at the tumor site, and allow for the achievement of therapeutic concentrations without the need for repetitive systemic administration of high therapeutic doses. Despite the enthusiasm evoked by preclinical studies that used MSC in various cancer therapy approaches, the translation of MSCs into clinical applications has faced serious challenges. This manuscript, with a critical viewpoint, reviewed the preclinical and clinical studies that have evaluated MSCs as a selective tumor delivery tool in various cancer therapy approaches, including gene therapy, immunotherapy, and chemotherapy. Then, the novel nanotechnology and bioengineering approaches that can improve the potency of MSC for tumor targeting and overcoming challenges related to their low localization at the tumor sites are discussed.

Magnetite-based Janus nanoparticles, their synthesis and biomedical applications

The advent of Janus nanoparticles has been a great breakthrough in the emerging field of nanomaterials. Janus nanoparticles refer to a single structure with two distinct chemical functions on either side. Owing to their asymmetric structures, they can be utilized in a variety of applications where monomorphic particles are insufficient. In the last decade, a wide variety of materials have been employed to fabricate Janus nanoparticles, and due to the great advantages of magnetite (Iron-oxide) NPs, they have been considered as one of the best candidates. With the main benefit of magnetic controlling, magnetite Janus nanoparticles fulfill great promises, especially in biomedical areas such as bioimaging, cancer therapies, theranostics, and biosensing. The intrinsic characteristics of magnetite Janus nanoparticles (MJNPs) even hold great potential in magnetite Janus forms of micro-/nanomotors. Despite the great interest and potential in magnetic Janus NPs, the need for a comprehensive review on MJNPs with a concentration on magnetite NPs has been overlooked. Herein, we present recent advancements in the magnetite-based Janus nanoparticles in the flourishing field of biomedicine. First, the synthesis and fabrication methods of Janus nanoparticles are discussed. Then we will delve into their intriguing biomedical applications, with a separate section for magnetite Janus micro-/nanomotors in biomedicine. And finally, the challenges and future outlook are provided. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Diagnostic Nanodevices Diagnostic Tools > In Vitro Nanoparticle-Based Sensing.

Retroviral Replicating Vectors Mediated Prodrug Activator Gene Therapy in a Gastric Cancer Model

Retroviral replicating vectors (RRVs) selectively replicate and can specifically introduce prodrug-activating genes into tumor cells, whereby subsequent prodrug administration induces the death of the infected tumor cells. We assessed the ability of two distinct RRVs generated from amphotropic murine leukemia virus (AMLV) and gibbon ape leukemia virus (GALV), which infect cells via type-III sodium-dependent phosphate transporters, PiT-2 and PiT-1, respectively, to infect human gastric cancer (GC) cells. A quantitative RT-PCR showed that all tested GC cell lines had higher expression levels of PiT-2 than PiT-1. Accordingly, AMLV, encoding a green fluorescent protein gene, infected and replicated more efficiently than GALV in most GC cell lines, whereas both RRVs had a low infection rate in human fibroblasts. RRV encoding a cytosine deaminase prodrug activator gene, which converts the prodrug 5-flucytosine (5-FC) to the active drug 5-fluorouracil, showed that AMLV promoted superior 5-FC-induced cytotoxicity compared with GALV, which correlated with the viral receptor expression level and viral spread. In MKN-74 subcutaneous xenograft models, AMLV had significant antitumor effects compared with GALV. Furthermore, in the MKN-74 recurrent tumor model in which 5-FC was discontinued, the resumption of 5-FC administration reduced the tumor volume. Thus, RRV-mediated prodrug activator gene therapy might be beneficial for treating human GC.

Cell and Tissue Specific Metabolism of Nucleoside and Nucleotide Drugs: Case Studies and Implications for Precision Medicine

Many clinically used antiviral drugs are nucleoside or nucleotide analog drugs, which have a unique mechanism of action that requires intracellular phosphorylation. This dependence on intracellular activation presents novel challenges for the discovery and development of nucleoside/nucleotide analog drugs. Contrary to many small molecule drug development programs that rely on plasma pharmacokinetics and systemic exposures, the precise mechanisms that result in efficacious intracellular nucleoside triphosphate concentrations must be understood in the process of nucleoside/nucleotide drug development. The importance is highlighted here, using the following as case studies: the herpes treatment acyclovir, the cytomegalovirus therapy ganciclovir, and human immunodeficiency virus (HIV) treatments based on tenofovir, which are also in use for HIV prophylaxis. For each drug, the specificity of metabolism that results in its activation in different cells or tissues is discussed, and the implications explored. Acyclovir's dependence on a viral enzyme for activation provides selective pressure for resistance mutations. Ganciclovir is also dependent on a viral enzyme for activation, and suicide gene therapy capitalizes on that for a novel oncology treatment. The tissue of most relevance for tenofovir activation depends on its use as treatment or as prophylaxis, and the pharmacogenomics and drug-drug interactions in those tissues must be considered. Finally, differential metabolism of different tenofovir prodrugs and its effects on toxicity risk are explored. Taken together, these examples highlight the importance of understanding tissue specific metabolism for optimal use of nucleoside/nucleotide drugs in the clinic. SIGNIFICANCE STATEMENT: Nucleoside and nucleotide analogue drugs are cornerstones in current antiviral therapy and prevention efforts that require intracellular phosphorylation for activity. Understanding their cell and tissue specific metabolism enables their rational, precision use for maximum efficacy.

Suicide gene strategies applied in ovarian cancer studies

Ovarian cancer represents the most lethal gynecological malignancy among women in developed countries. Despite the recent innovations, the improvements in the 5-year survival rate have been insufficient and the management of this disease still remains a challenge. The fact that the majority of patients experience recurrent or resistant disease have substantiated the necessity of an innovative treatment. Among various strategies investigated, the recent strides made in gene delivery techniques have made gene therapy, including suicide gene strategies, a potential alternative for treating ovarian cancer. Various suicide gene candidates, which are capable of promoting cancer cell apoptosis directly after its entry or indirectly by prodrug administration, can be separated into three systems using enzyme-coding, toxin or pro-apoptotic genes. With this review, we aim to provide an overview of different suicide genes depending on therapeutic strategies, the vectors used to deliver these transgenes specifically to malignant cells, and the combined treatments of these genes with various therapeutic regimens.

Enhanced tumor inhibiting effect of 131I-BDI-1-based radioimmunotherapy and cytosine deaminase gene therapy modulated by a radio-sensitive promoter in nude mice bearing bladder cancer

Radioimmunotherapy (RIT) has great potential in cancer therapy. However, its efficacy in numerous tumors is restricted due to myelotoxicity, thereby limiting the dose of radionuclide. To increase tumor radiosensitivity, we incorporated the recombinant lentivirus into the EJ cells (bladder cancer [BC] cells), and examined the combined anti-tumor effects of RIT with 131I-BDI-1(131I-monoclonal antibody against human BC-1) and gene therapy (GT). The recombinant lentivirus was constructed and packed. The animal xenograft model was built and when the tumor reached about 0.5 cm in diameter, the mice were randomly separated into four groups: (1) RIT + GT: the xenografts were continuously incorporated with the recombinant lentivirus for two days. And 7.4 MBq 131I-BDI-1 was IV-injected, and 10 mg prodrug 5-fluorocytosine (FC) was IV-injected for 7 days, (2) RIT: same dose of 131I-BDI-1 as the previous group mice, (3) GT: same as the first group, except no 131I-BDI-1, and (4) Untreated. Compute tumor volumes in all groups. After 28 days the mice were euthanized and the tumors were extracted and weighed, and the inhibition rate was computed. The RIT + GT mice, followed by the RIT mice, exhibited markedly slower tumor growth, compared to the control mice. The tumor size was comparable between the GT and control mice. The tumor inhibition rates after 28 days of incubation were 42.85 ± 0.23%, 27.92 ± 0.21% and 0.57 ± 0.11% for the four groups, respectively. In conclusion, RIT, combined with GT, suppressed tumor development more effectively than RIT or GT alone. This data highlights the potent additive effect of radioimmune and gene therapeutic interventions against cancer.

The use of adenoviral vectors in gene therapy and vaccine approaches

Adenovirus was first identified in the 1950s and since then this pathogenic group of viruses has been explored and transformed into a genetic transfer vehicle. Modification or deletion of few genes are necessary to transform it into a conditionally or non-replicative vector, creating a versatile tool capable of transducing different tissues and inducing high levels of transgene expression. In the early years of vector development, the application in monogenic diseases faced several hurdles, including short-term gene expression and even a fatality. On the other hand, an adenoviral delivery strategy for treatment of cancer was the first approved gene therapy product. There is an increasing interest in expressing transgenes with therapeutic potential targeting the cancer hallmarks, inhibiting metastasis, inducing cancer cell death or modulating the immune system to attack the tumor cells. Replicative adenovirus as vaccines may be even older and date to a few years of its discovery, application of non-replicative adenovirus for vaccination against different microorganisms has been investigated, but only recently, it demonstrated its full potential being one of the leading vaccination tools for COVID-19. This is not a new vector nor a new technology, but the result of decades of careful and intense work in this field.

Dioscin potentiates the antitumor effect of suicide gene therapy in melanoma by gap junction intercellular communication-mediated antigen cross-presentation

Dioscin (Dio), steroid saponin, exists in several medicinal herbs with potent anticancer efficacy. This study aimed to explore the effect of Dio on the immune-related modulation and synergistic therapeutic effects of the herpes simplex virus thymidine kinase/ganciclovir (HSV-Tk/GCV) suicide gene therapy system in murine melanoma, thereby providing a research basis to improve the potential immunomodulatory mechanism underlying combination therapy. Using both in vitro and in vivo experiments, we confirmed the immunocidal effect of Dio-potentiated suicide gene therapy on melanoma. The results showed that Dio upregulated connexin 43 (Cx43) expression and improved gap junction intercellular communication (GJIC) in B16 cells while increasing the cross-presentation of antigens by dendritic cells (DCs), eventually promoting the activation and antitumor immune killing effects of CD8⁺ T lymphocytes. In contrast, inhibition or blockade of the GJIC function (overexpression of mutant Cx43 tumor cells/Gap26) partially reversed the potentiating effect. The significant synergistic effect of Dio on HSV-Tk/GCV suicide gene therapy was further investigated in a B16 xenograft mouse model. The increased number and activation ratio of CD8⁺ T lymphocytes and the levels of Gzms-B, IFN-γ, and TNF-α in mice reconfirmed the potential modulatory effects of Dio on the immune system. Taken together, Dio targets Cx43 to enhance GJIC function, improve the antigens cross-presentation of DCs, and activate the antitumor immune effect of CD8⁺ T lymphocytes, thereby providing insights into the potential immunomodulatory mechanism underlying combination therapy.

Stem cells therapy for thyroid diseases: progress and challenges

Background

Thyroid hormones are indispensable for organ development and maintaining homeostasis. Thyroid diseases, including thyroiditis and thyroid cancer, affect the normal secretion of hormones and result in thyroid dysfunction.

Objective

This review focuses on therapeutic applications of stem cells for thyroid diseases.

Methods

A literature search of Medline and PubMed was conducted (January 2000–July 2021) to identify recent reports on stem cell therapy for thyroid diseases.

Results

Stem cells are partially developed cell types. They have the capacity to form specialized cells. Besides embryonic stem cells and mesenchymal stem cells, organ resident stem cells and cancer stem cells are recently reported to have important roles in forming organ specific cells and cancers. Stem cells, especially mesenchymal stem cells, have anti-inflammatory and anticancer functions as well.

Conclusions

This review outlines the therapeutic potency of embryonic stem cells, mesenchymal stem cells, thyroid resident stem cells, and thyroid cancer stem cells in thyroid cells’ regeneration, thyroid function modulation, thyroiditis suppression, and antithyroid cancers. Stem cells represent a promising form of treatment for thyroid disorders.

Enhancement of nanoparticle-mediated double suicide gene expression driven by 'E9-hTERT promoter' switch in dedifferentiated thyroid cancer cells

Differentiated thyroid cancer (DTC), such as papillary thyroid cancer, has a good prognosis after routine treatment. However, in the course of treatment, 5% to 20% of cases may dedifferentiate and can be transformed into dedifferentiated DTC (deDTC) or anaplastic thyroid cancer, leading to treatment failure. To date, several drugs have been used effectively for dedifferentiated thyroid cancer, whereas gene therapy may be a potential method. Literature reported that double suicide genes driven by human telomerase reverse transcriptase promoter (hTERTp) can specifically express in cancer cells and kill them. However, the weak activity of hTERTp limits its further research. To overcome this weakness, we constructed a novel chitosan nanocarrier containing double suicide genes driven by a ‘gene switch’ (a cascade of radiation enhancer E9 and a hTERTp). The vector was labeled with iodine-131 (¹³¹I). On one hand, E9 can significantly enhance the activity of hTERTp under the weak radiation of ¹³¹I, thereby increasing the expression of double suicide genes in deDTC cells. On the other hand, ¹³¹I also plays a certain killing role when it enters host cells. The proposed nanocarrier has good specificity for deDTC cells and thus deserves further study.

Brain HIV-1 latently-infected reservoirs targeted by the suicide gene strategy

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.

Delivery of cancer therapies by synthetic and bio-inspired nanovectors

BACKGROUND

As a complement to the clinical development of new anticancer molecules, innovations in therapeutic vectorization aim at solving issues related to tumor specificity and associated toxicities. Nanomedicine is a rapidly evolving field that offers various solutions to increase clinical efficacy and safety. MAIN: Here are presented the recent advances for different types of nanovectors of chemical and biological nature, to identify the best suited for translational research projects. These nanovectors include different types of chemically engineered nanoparticles that now come in many different flavors of 'smart' drug delivery systems. Alternatives with enhanced biocompatibility and a better adaptability to new types of therapeutic molecules are the cell-derived extracellular vesicles and micro-organism-derived oncolytic viruses, virus-like particles and bacterial minicells. In the first part of the review, we describe their main physical, chemical and biological properties and their potential for personalized modifications. The second part focuses on presenting the recent literature on the use of the different families of nanovectors to deliver anticancer molecules for chemotherapy, radiotherapy, nucleic acid-based therapy, modulation of the tumor microenvironment and immunotherapy.

CONCLUSION

This review will help the readers to better appreciate the complexity of available nanovectors and to identify the most fitting "type" for efficient and specific delivery of diverse anticancer therapies.

Directed evolution of the B. subtilis nitroreductase YfkO improves activation of the PET-capable probe SN33623 and CB1954 prodrug

OBJECTIVES

To use directed evolution to improve YfkO-mediated reduction of the 5-nitroimidazole PET-capable probe SN33623 without impairing conversion of the anti-cancer prodrug CB1954.

RESULTS

Two iterations of error-prone PCR, purifying selection, and FACS sorting in a DNA damage quantifying GFP reporter strain were used to identify three YfkO variants able to sensitize E. coli host cells to at least 2.4-fold lower concentrations of SN33623 than the native enzyme. Two of these variants were able to be purified in a functional form, and in vitro assays revealed these were twofold and fourfold improved in k_cat/K_M with SN33623 over wild type YfkO. Serendipitously, the more-active variant was also nearly fourfold improved in k_cat/K_M versus wild type YfkO in converting CB1954 to a genotoxic drug.

CONCLUSIONS

The enhanced activation of the PET imaging probe SN33623 and CB1954 prodrug exhibited by the lead evolved variant of YfkO offers prospects for improved enzyme-prodrug therapy.

HSV-TK Expressing Mesenchymal Stem Cells Exert Inhibitory Effect on Cervical Cancer Model

A growing area of research is focused on cancer therapy, and new therapeutic approaches are welcomed. Mesenchymal stem cell (MSC)-based gene therapy is a promising strategy in oncology. Intrinsic tropism and migration to tumor microenvironment with off lights are attractive features of this type of cell carrier. In this way, suicide genes have also found a good platform for better performance and have shown a stronger anti-tumor mechanism by riding on mesenchymal cells. In this study, we investigated the anti-tumor activity of intratumoral injected MSCs transduced with a lentivector expressing the HSV/TK in a mouse cervical cancer model. Following the injection of MSCs transduced with lentivector carrying TK, MSCs alone or PBS into the mice tumor, ganciclovir was administered intraperitoneally during 14 days, and tumor size, survival time, natural killer (NK) cells and cytotoxic T lymphocyte (CTL) activities were assessed. We demonstrated that combination of suicide therapy and cell therapy leading m,to successful tumor inhibition. Significant reduction in tumor size was detected in test group in comparison with controls. Also, potent antitumor NK and CTL activity was seen in treatment group in comparison with controls. Our data demonstrated that the mesenchymal cells expressing TK had inhibitory effect on cervical cancer model.

Gene Therapy in Cancer Treatment: Why Go Nano?

The proposal of gene therapy to tackle cancer development has been instrumental for the development of novel approaches and strategies to fight this disease, but the efficacy of the proposed strategies has still fallen short of delivering the full potential of gene therapy in the clinic. Despite the plethora of gene modulation approaches, e.g., gene silencing, antisense therapy, RNA interference, gene and genome editing, finding a way to efficiently deliver these effectors to the desired cell and tissue has been a challenge. Nanomedicine has put forward several innovative platforms to overcome this obstacle. Most of these platforms rely on the application of nanoscale structures, with particular focus on nanoparticles. Herein, we review the current trends on the use of nanoparticles designed for cancer gene therapy, including inorganic, organic, or biological (e.g., exosomes) variants, in clinical development and their progress towards clinical applications.

Effect of Diphtheria Toxin-Based Gene Therapy for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a major global malignancy, responsible for >90% of primary liver cancers. Currently available therapeutic options have poor performances due to the highly heterogeneous nature of the tumor cells; recurrence is highly probable, and some patients develop resistances to the therapies. Accordingly, the development of a novel therapy is essential. We assessed gene therapy for HCC using a diphtheria toxin fragment A (DTA) gene-expressing plasmid, utilizing a non-viral hydrodynamics-based procedure. The antitumor effect of DTA expression in HCC cell lines (and alpha-fetoprotein (AFP) promoter selectivity) is assessed in vitro by examining HCC cell growth. Moreover, the effect and safety of the AFP promoter-selective DTA expression was examined in vivo using an HCC mice model established by the hydrodynamic gene delivery of the yes-associated protein (YAP)-expressing plasmid. The protein synthesis in DTA transfected cells is inhibited by the disappearance of tdTomato and GFP expression co-transfected upon the delivery of the DTA plasmid; the HCC cell growth is inhibited by the expression of DTA in HCC cells in an AFP promoter-selective manner. A significant inhibition of HCC occurrence and the suppression of the tumor marker of AFP and des-gamma-carboxy prothrombin can be seen in mice groups treated with hydrodynamic gene delivery of DTA, both 0 and 2 months after the YAP gene delivery. These results suggest that DTA gene therapy is effective for HCC.

Diagnosis and Treatment of Breast Cancer in the Precision Medicine Era

Breast cancer is one of the most leading causes of death for women worldwide. According to statistics published by the International Agency for Research on Cancer (IARC), the incidence of breast cancer is on the rise year by year in most parts of the world. The existence of heterogeneity limits the early diagnosis and targeted therapy of breast cancer. Nowadays, precision medicine brings a new perspective to personalized diagnosis and targeted therapy, overcomes the heterogeneity of different patients, and provides an opportunity for screening of high-risk populations. As a clinician, we are committed to using genomic to provide a favorable perspective in the field of breast cancer. The current review describes the recent advances in the understanding of precision medicine for breast cancer in the aspect of the genomics which could be applied to improve our ability to diagnose and treat breast cancer individually and effectively.

Gene Therapy for Liver Cancers: Current Status from Basic to Clinics

The liver is a key organ for metabolism, protein synthesis, detoxification, and endocrine function, and among liver diseases, including hepatitis, cirrhosis, malignant tumors, and congenital disease, liver cancer is one of the leading causes of cancer-related deaths worldwide. Conventional therapeutic options such as embolization and chemotherapy are not effective against advanced-stage liver cancer; therefore, continuous efforts focus on the development of novel therapeutic options, including molecular targeted agents and gene therapy. In this review, we will summarize the progress toward the development of gene therapies for liver cancer, with an emphasis on recent clinical trials and preclinical studies.

Alteration of mitochondrial DNA homeostasis in drug-induced liver injury

Mitochondrial DNA (mtDNA) encodes for 13 proteins involved in the oxidative phosphorylation (OXPHOS) process. In liver, genetic or acquired impairment of mtDNA homeostasis can reduce ATP output but also decrease fatty acid oxidation, thus leading to different hepatic lesions including massive necrosis and microvesicular steatosis. Hence, a severe impairment of mtDNA homeostasis can lead to liver failure and death. An increasing number of investigations report that some drugs can induce mitochondrial dysfunction and drug-induced liver injury (DILI) by altering mtDNA homeostasis. Some drugs such as ciprofloxacin, antiretroviral nucleoside reverse-transcriptase inhibitors and tacrine can inhibit hepatic mtDNA replication, thus inducing mtDNA depletion. Drug-induced reduced mtDNA levels can also be the consequence of reactive oxygen species-mediated oxidative damage to mtDNA, which triggers its degradation by mitochondrial nucleases. Such mechanism is suspected for acetaminophen and troglitazone. Other pharmaceuticals such as linezolid and tetracyclines can impair mtDNA translation, thus selectively reducing the synthesis of the 13 mtDNA-encoded proteins. Lastly, some drugs might alter the mtDNA methylation status but the pathophysiological consequences of such alteration are still unclear. Drug-induced impairment of mtDNA homeostasis is probably under-recognized since preclinical and post-marketing safety studies do not classically investigate mtDNA levels, mitochondrial protein synthesis and mtDNA oxidative damage.