Enhancement of reporter gene detection sensitivity by insertion of specific mini-peptide-coding sequences

Molecular Imaging of Stem Cells

Regenerative medicine with the use of stem cells has appeared as a potential therapeutic alternative for many disease states. Despite initial enthusiasm, there has been relatively slow transition to clinical trials. In large part, numerous questions remain regarding the viability, biology and efficacy of transplanted stem cells in the living subject. The critical issues highlighted the importance of developing tools to assess these questions. Advances in molecular biology and imaging have allowed the successful non-invasive monitoring of transplanted stem cells in the living subject. Over the years these methodologies have been updated to assess not only the viability but also the biology of transplanted stem cells. In this review, different imaging strategies to study the viability and biology of transplanted stem cells are presented. Use of these strategies will be critical as the different regenerative therapies are being tested for clinical use.

Asymmetric Waveforms Decrease Lethal Thresholds in High Frequency Irreversible Electroporation Therapies

Irreversible electroporation (IRE) is a promising non-thermal treatment for inoperable tumors which uses short (50-100 μs) high voltage monopolar pulses to disrupt the membranes of cells within a well-defined volume. Challenges with IRE include complex treatment planning and the induction of intense muscle contractions. High frequency IRE (H-FIRE) uses bursts of ultrashort (0.25-5 μs) alternating polarity pulses to produce more predictable ablations and alleviate muscle contractions associated with IRE. However, H-FIRE generally ablates smaller volumes of tissue than IRE. This study shows that asymmetric H-FIRE waveforms can be used to create ablation volumes equivalent to standard IRE treatments. Lethal thresholds (LT) of 505 V/cm and 1316 V/cm were found for brain cancer cells when 100 μs IRE and 2 μs symmetric H-FIRE waveforms were used. In contrast, LT as low as 536 V/cm were found for 2 μs asymmetric H-FIRE waveforms. Reversible electroporation thresholds were 54% lower than LTs for symmetric waveforms and 33% lower for asymmetric waveforms indicating that waveform symmetry can be used to tune the relative sizes of reversible and irreversible ablation zones. Numerical simulations predicted that asymmetric H-FIRE waveforms are capable of producing ablation volumes which were 5.8-6.3x larger than symmetric H-FIRE waveforms indicating that in vivo investigation of asymmetric waveforms is warranted.

The impact of non-electrical factors on electrical gene transfer

Electrical pulses directly and effectively boost both in vitro and in vivo gene transfer, but this process is greatly affected by non-electrical factors that exist during electroporation. These factors include, but are not limited to, the types of cells or tissues used, property of DNA, DNA formulation, and expressed protein. In this mini-review, we only describe and discuss a summary of DNA properties and selected DNA formulations on gene transfer via electroporation. The properties of DNA were selected for review because a substantial amount of remarkable work has been performed during the past few years but has received less notice than other works, although DNA properties appear to be critical for boosting electroporation delivery. The selected formulations will be covered in this mini-review because we are only interested in the simple formulations that could be used for cell or gene therapy via electroporation. Plus, there was an extensive review of DNA formulations in the first edition of this book. The formulations discussed in this mini-review represent novel developments in recent years and may impact electroporation significantly. These advancements in DNA formulations could prove to be important for gene delivery and disease treatment.

Discovery of a linear peptide for improving tumor targeting of gene products and treatment of distal tumors by IL-12 gene therapy

Like many effective therapeutics, interleukin-12 (IL-12) therapy often causes side effects. Tumor targeted delivery may improve the efficacy and decrease the toxicity of systemic IL-12 treatments. In this study, a novel targeting approach was investigated. A secreted alkaline phosphatase (SEAP) reporter gene-based screening process was used to identify a mini-peptide which can be produced in vivo to target gene products to tumors. The coding region for the best peptide was inserted into an IL-12 gene to determine the antitumor efficacy. Affinity chromatography, mass spectrometry analysis, and binding studies were used to identify a receptor for this peptide. We discovered that the linear peptide VNTANST increased the tumor accumulation of the reporter gene products in five independent tumor models including one human xenogeneic model. The product from VNTANST-IL-12 fusion gene therapy increased accumulation of IL-12 in the tumor environment, and in three tumor models, VNTANST-IL-12 gene therapy inhibited distal tumor growth. In a spontaneous lung metastasis model, inhibition of metastatic tumor growth was improved compared to wild-type IL-12 gene therapy, and in a squamous cell carcinoma model, toxic liver lesions were reduced. The receptor for VNTANST was identified as vimentin. These results show the promise of using VNTANST to improve IL-12 treatments.