In vivo induction of interferon gamma expression in grey horses with metastatic melanoma resulting from direct injection of plasmid DNA coding for equine interleukin 12.

This research explored a novel treatment for melanoma in grey horses using interleukin-12 gene therapy, with positive results indicating a fast response and elimination rate in the system and confirmed biological activity.

Background

• This research paper concerns a study conducted on grey horses suffering from melanoma (a type of skin cancer). The researchers embarked on a novel approach to treat melanoma using gene therapy, specifically by the direct injection of plasmid DNA coding for equine Interleukin 12 (IL-12).
• Interleukin-12 (IL-12) is a type of cytokine that plays a crucial role in cellular immune responses and is also found to have anti-tumor activities in several animal models.
• The primary objectives of the study were to assess the pharmacokinetics of the injected plasmid, validate the in vivo gene transfer method, ascertain the pharmacodynamic properties through the evaluation of induced interferon gamma (IFN-g) expression, and determine the practicability of this method.

Methods

• Seven grey horses with melanoma were chosen and injected intratumorally, directly into the tumor, with 250 µg of naked plasmid DNA that codes for IL-12.
• Post-injection, peripheral blood and biopsies were collected from the horses at 13 different time points until day 14 to monitor and analyze the results.
• The collected samples were then examined using quantitative real-time PCR in order to measure the presence of the plasmid DNA in the blood and mRNA expression for IFN-g in tissue samples.

Findings

• From the blood samples, it was found that the plasmid DNA exhibited fast elimination kinetics, with over 99% of the plasmid disappearing from the bloodstream within 36 hours post-injection.
• The tissue samples showed that the expression of IFN-g increased quickly after the injection of the IL-12 plasmid, indicating a positive reaction. However, the level of increase varied between individual horses.
• The outcomes suggest that intratumoural injection of plasmid DNA is a practicable method for inducing transgene expression in vivo.
• The biological activity of the injected IL-12 transgene was confirmed by the detection and measurement of IFN-g expression.

Significance

• This research provides valuable insights towards developing more effective treatments for melanoma in animals and potentially humans by using gene therapy.
• The fast response and elimination rate observed signifies minimal systemic exposure, possibly reducing the chance of adverse side effects.
• The induction of IFN-g expression indicates that this method could stimulate the horses’ immune system to fight the tumors, presenting a promising addition to current anti-cancer therapies.