Irreversible Electroporation: A Technique for Ablating Pancreatic Tumor in Mouse

- Irreversible electroporation or IRE is a technique for ablating pancreatic tumors by administering short, high-voltage pulses of electrical current to the tumor, causing permanent damage to the tumor cells. IRE has high selectivity and accessibility for the target tumor area. It does not cause heat-induced damage to the nearby healthy cells, making it a promising anti-tumor therapy.

Begin by placing an anesthetized mouse on the side and dissect its abdominal cavity to locate the tumor on the surface of the pancreas. Next, use the electrodes, bracketing the tumor site, and administer targeted pulses of electric current for the desired time duration. The electric current beyond a certain threshold, causes permanent pores in the cell membrane of tumor cells, preventing the cell from returning to the state of homeostasis.

These pores cause the cell's intracellular contents to come outside, therefore leading to gradual cell death by apoptosis. Now, close the abdominal cavity and leave the mouse to recover in the home cage. Finally, monitor the pancreas for the reduction in the size of the tumor, post-electroporation. In the following protocol, we will demonstrate a method for performing irreversible electroporation to disrupt mice's pancreatic tumors.

- Before the tumor reaches 6 millimeters in diameter, place the anesthetized animal on its right side to allow access to the tumor and use clippers and an alcohol swab to clean the tumor site. Using forceps, elevate the skin directly under the tumor and insert two needle array electrodes through the skin, parallel to the body to bracket the tumor, taking care that the electrodes do not penetrate the peritoneal cavity.

Set the electroporator to deliver 100-microsecond pulses, at a 1 Hertz frequency, at 1,500 volts per centimeter for a total of 150 pulses and use the foot pedal to deliver the pulses, separating each set of 10 pulses by 10 seconds to allow heat dissipation between each set of pulses.

- As muscle twitching occurs during the IRE delivery and is more pronounced during the initial set of pulses, ensure that the electrodes are still in the desired location and that the animal is still sedated after each set of pulses.

- After no more than 200 seconds of dosing, remove the electrodes and record the actual voltage delivered as displayed on the electroporator. Then, return the mouse to its cage. For IRE of an orthotopic tumor, 8 to 10 days post tumor implantation, use blunt nosed forceps to externalize the tumor with the forceps, and tightly capture the tumor with the platinum electrodes of the tweezer-trode.

Deliver the electroporation pulses as just demonstrated, keeping the tumor externalized for the last set of pulses for at least 60 seconds to monitor for any signs of hemorrhage. Then, return the tumor to the abdominal cavity and close the incision as demonstrated, monitoring the animal until it is fully recovered.