Sleeping Beauty transposon system harboring HRAS, c-Myc and shp53 induces sarcomatoid carcinomas in mouse skin

Specific epigenetic microenvironment and the regulation of tumor-related gene expression by trichloroethylene in human hepatocytes

Trichloroethylene (TCE), an important volatile organic solvent, causes a series of toxic damage to human. Conventional genetic mechanisms cannot fully explain its toxicity and carcinogenicity, indicative of the possible involvement of epigenetic mechanisms. Our study was intended to investigate the epigenetic toxicity and underlying mechanisms of TCE. Data showed that 0.3 mM TCE treatment for 24 h increased the growth of L-02 cells transiently. In contrast, subacute exposure to TCE inhibited cell growth and induced the genomic DNA hypomethylation and histone hyperacetylation. Further studies have revealed the TCE-induced DNA hypomethylation in the promoter regions of tumor-related genes, N-Ras, c-Jun, c-Myc, c-Fos and IGF-II, promoting their protein levels in a time-dependent manner. These results reveal there is a negative relationship existing between DNA hypomethylation and protein expression in tumor-related gene after TCE exposure under specific epigenetic microenvironment, serving as early biomarkers for TCE-associated diseases.

Latest Advances for the Sleeping Beauty Transposon System: 23 Years of Insomnia but Prettier than Ever: Refinement and Recent Innovations of the Sleeping Beauty Transposon System Enabling Novel, Nonviral Genetic Engineering Applications

The Sleeping Beauty transposon system is a nonviral DNA transfer tool capable of efficiently mediating transposition-based, stable integration of DNA sequences of choice into eukaryotic genomes. Continuous refinements of the system, including the emergence of hyperactive transposase mutants and novel approaches in vectorology, greatly improve upon transposition efficiency rivaling viral-vector-based methods for stable gene insertion. Current developments, such as reversible transgenesis and proof-of-concept RNA-guided transposition, further expand on possible applications in the future. In addition, innate advantages such as lack of preferential integration into genes reduce insertional mutagenesis-related safety concerns while comparably low manufacturing costs enable widespread implementation. Accordingly, the system is recognized as a powerful and versatile tool for genetic engineering and is playing a central role in an ever-expanding number of gene and cell therapy clinical trials with the potential to become a key technology to meet the growing demand for advanced therapy medicinal products.

Precision medicine, agriculture, and genome editing: science and ethics

The era of precision medicine has generated advances in various fields of science and medicine with the potential for a paradigm shift in healthcare delivery that will ultimately lead to an individualized approach to medicine. Such timely topics were explored in 2018 at a workshop held at the Third International Conference on One Medicine One Science (iCOMOS), in Minneapolis, Minnesota. A broad range of scientists and regulatory experts provided detailed insights into the challenges and opportunities associated with precision medicine and gene editing. There was a general consensus that advances in studying the genomic traits driving differential pharmacogenomics will undoubtedly enhance individualized treatments for a wide variety of diseases. Ethical considerations, societal implications, approaches for prioritizing safe and secure use of treatment modalities, and the advent of high-throughput computing and analysis of large, complex datasets were discussed. Large biobanks, such as the All of Us Research Program and the Veterans Affairs Million Veterans Program, can aid studies of various conditions in massive cohorts of patients. As the applications of precision medicine continue to mature, the full potential and promise of these individualized approaches will continue to yield important advances in transplant medicine, oncology, public health, agriculture, pharmacology, and bioinformatics.

Development of a Mouse Model of Prostate Cancer Using the Sleeping Beauty Transposon and Electroporation

The Sleeping Beauty (SB) transposon system is non-viral and uses insertional mutagenesis, resulting in the permanent expression of transferred genes. Although the SB transposon is a useful method for establishing a mouse tumor model, there has been difficulty in using this method to generate tumors in the prostate. In the present study, electroporation was used to enhance the transfection efficiency of the SB transposon. To generate tumors, three constructs (a c-Myc expression cassette, a HRAS (HRas proto-oncogene, GTPase) expression cassette and a shRNA against p53) contained within the SB transposon plasmids were directly injected into the prostate. Electroporation was conducted on the injection site after the injection of the DNA plasmid. Following the tumorigenesis, the tumors were monitored by animal PET imaging and identified by gross observation. After this, the tumors were characterized by using histological and immunohistochemical techniques. The expression of the targeted genes was analyzed by Real-Time qRT-PCR. All mice subjected to the injection were found to have prostate tumors, which was supported by PSA immunohistochemistry. To our knowledge, this is the first demonstration of tumor induction in the mouse prostate using the electroporation-enhanced SB transposon system in combination with c-Myc, HRAS and p53. This model serves as a valuable resource for the future development of SB-induced mouse models of cancer.

[Establishment of New Zealand rabbit models of aplastic anemia]

OBJECTIVE

To screen for the optimal dose of benzene and cyclophosphamide using an orthogonal design for establishment of New Zealand rabbit models of aplastic anemia.

METHODS

Following an orthogonal experimental design, the effects of 3 levels of 4 factors, namely the dose of benzene (A), the dose of cyclophosphamide (B), the number of benzene injections (C), and the number of cyclophosphamide injections (D) were tested in the establishment of New Zealand rabbit models of aplastic anemia using a L₉ (3⁴) orthogonal table, and the optimal protocol for the model establishment was selected from the 9 experimental groups. Each rabbit received subcutaneous injection of benzene on the back every other day, followed by daily cyclophosphamide injection via the ear vein for prescribed times. The blood routine was examined every 6 days, and before modeling and at 36 days after modeling, a small sample of the femoral bone was collected for bone marrow histopathological examination.

RESULTS

Comparison of the white blood cell, erythrocyte and platelet counts among the 9 groups showed successful modeling in Groups 4-9, and daily mean reduction rates of the cell counts in Groups 7, 8, and 9 differed significantly from those in the other groups (P<0.05). In Group 7, bone marrow sections showed low myelodysplasia, reduced hematopoietic tissue, reduced or even absence of megakaryocytes, and increased fat cells. Further observation found that the rabbits in Group 7 had sustained bone marrow suppression, consistent with the clinical characteristics of the disease.

CONCLUSION

Stable models of aplastic anemia can be established efficiently in New Zealand rabbits by a combination of 8 subcutaneous injections of benzene at 1.5 mL/kg and 4 intravenous injections of cyclophosphamide at 10 mg/kg.

[Establishment of New Zealand rabbit models of aplastic anemia]

OBJECTIVE

To screen for the optimal dose of benzene and cyclophosphamide using an orthogonal design for establishment of New Zealand rabbit models of aplastic anemia.

METHODS

Following an orthogonal experimental design, the effects of 3 levels of 4 factors, namely the dose of benzene (A), the dose of cyclophosphamide (B), the number of benzene injections (C), and the number of cyclophosphamide injections (D) were tested in the establishment of New Zealand rabbit models of aplastic anemia using a L9 (34) orthogonal table, and the optimal protocol for the model establishment was selected from the 9 experimental groups. Each rabbit received subcutaneous injection of benzene on the back every other day, followed by daily cyclophosphamide injection via the ear vein for prescribed times. The blood routine was examined every 6 days, and before modeling and at 36 days after modeling, a small sample of the femoral bone was collected for bone marrow histopathological examination.

RESULTS

Comparison of the white blood cell, erythrocyte and platelet counts among the 9 groups showed successful modeling in Groups 4-9, and daily mean reduction rates of the cell counts in Groups 7, 8, and 9 differed significantly from those in the other groups (P<0.05). In Group 7, bone marrow sections showed low myelodysplasia, reduced hematopoietic tissue, reduced or even absence of megakaryocytes, and increased fat cells. Further observation found that the rabbits in Group 7 had sustained bone marrow suppression, consistent with the clinical characteristics of the disease.

CONCLUSION

Stable models of aplastic anemia can be established efficiently in New Zealand rabbits by a combination of 8 subcutaneous injections of benzene at 1.5 mL/kg and 4 intravenous injections of cyclophosphamide at 10 mg/kg.

Sleeping Beauty transposon system for genetic etiological research and gene therapy of cancers

Carcinogenesis is etiologically associated with somatic mutations of critical genes. Recently, a number of somatic mutations and key molecules have been found to be involved in functional networks affecting cancer progression. Suitable animal models are required to validate cancer-promoting or -inhibiting capacities of these mutants and molecules. Sleeping Beauty transposon system consists of a transposon that carries gene(s) of interest and a transposase that recognizes, excises, and reinserts genes in given location of the genome. It can create both gain-of-function and loss-of-function mutations, thus being frequently chosen to investigate the etiological mechanisms and gene therapy for cancers in animal models. In this review, we summarized current advances of Sleeping Beauty transposon system in revealing molecular mechanism of cancers and improving gene therapy. Understanding molecular mechanisms by which driver mutations contribute to carcinogenesis and metastasis may pave the way for the development of innovative prophylactic and therapeutic strategies against malignant diseases.

Electroporation markedly improves Sleeping Beauty transposon-induced tumorigenesis in mice

The Sleeping Beauty (SB) transposon system is an important tool for genetic studies. It is used to insert a gene of interest into the host chromosome, thus enabling permanent gene expression. However, this system is less useful in higher eukaryotes because the transposition frequency is low. Efforts to improve the efficacy of the SB transposon system have focused on the method of gene delivery, but although electroporation has recently attracted much attention as an in vivo gene delivery tool, the simultaneous use of electroporation and the SB transposon system has not been studied for gene transfer in mice. In this study, electroporation was used in a model of SB transposon-induced insertional tumorigenesis. Electroporation increased the rate of tumor development to three times that of the control group. There was no difference in phenotype between tumors induced with the SB transposon system alone and those induced by the SB transposon and electroporation. Electroporation therefore may be an efficient means of improving the efficacy of gene transfer via the SB transposon system.