Most patient-derived tumor animal models are subcutaneously implanted, preventing the evaluation of important features of tumors and of the drug efficacy. Housing the implanted tumors within the liver facilitated this analysis without the risk of too much deviations occurring within the liver. Before beginning the procedure, spray all of the materials and instruments with 70%ethyl alcohol.
Confirm a lack of response to toe pinch in the anesthetized animal. Place the mouse in the supine position on a heating pad, and wet the fur with additional 70%ethyl alcohol. Spread the fur to visualize the skin below the left subcostal area.
Remove hair, and apply iodine to be absorbed into the skin. Place a sterile surgical drape with a two-centimeter hole over the mouse, and use curved ultra fine forceps to lift the abdominal skin. Make a one-centimeter transverse left subcostal incision into the tented skin, and insert curved scissor tips into the incision to separate the peritoneum from the skin.
Retract the scissors without opening the blades, and locate the liver under the peritoneum by its dark reddish color. Use the curved scissors to make a one-centimeter transverse incision in the peritoneum. Using the other hand, insert the edge of a cotton swab beneath the left liver lobe, and roll the swab downward to push up the liver.
Lift the swab to transfer the liver onto a nonwoven, absorbent fabric sheet. Holding a sterile number 11 scalpel blade parallel to the surface, press the blade horizontally into the liver to make a five-millimeter deep by five-millimeter wide incision in the parenchyma while softly pressing the incision site with a cotton swab. Roll the cotton swab upward to open the incision site.
Use curved ultra fine forceps to implant a one-millimeter cube of tumor tissue into the pocket. Retract the forceps while rolling the cotton swab in the reverse direction while pressing down, and remove the swab. Immediately place an absorbable hemostat on the incision site, and confirm hemostasis.
Next use blunt ended forceps to peel the liver from the fabric sheet, and return the liver to the abdominal cavity. Then close the peritoneum with a 5-0 absorbable suture and a double ligature, and close the skin with a 5-0 absorbable suture and a triple ligature. The xenograft tumor engrafts in the liver as a solitary tumor without daughter nodules.
Surgical orthotopic injection into the liver using microneedles can result in a successful engraftment of a cluster of cultured human liver metastatic uveal melanoma cells within the liver. Using this liver orthotopic patient-derived tumor model, the efficacy of the drugs injected directly into the liver can be tested with similar expected outcomes to those observed in clinical patients.
