How to establish a solitary and localized VX2 lung cancer rabbit model? A simple and effective intrapulmonary tumor implantation technique

Abstract

Background: The purpose of this study is to establish a simple and effective technique for the generation of an intrapulmonary tumor model that yields solitary, localized intrapulmonary tumor, and to analyze the highlights of the technique.

Methods: After being anesthetized by slow intravenous injection of pentobarbital without oral endotracheal intubation, a right intercostal incision was made between the fifth and sixth ribs or at the next intercostal space; the inferior lobe of the right lung was exposed. A 16-gauge needle contained a strip of tumor tissue in the distal portion which connected to a 1.0-mL syringe that contained 0.1 mL air inside, was inserted into the parenchyma at an estimated depth of 1.0 cm, and the air was injected quickly to eject the tumor tissue into the pulmonary parenchyma. The air was drawn from the chest cavity by a race track, and the chest was closed. Thirty animals (Group A) received intrapulmonary tumor implantation (IPTI) as described above, and 16 animals (Group B) received IPTI using a suspension of small tumor fragment. Eight animals in each group were monitored by computed tomography (CT) scanning (Group CTA and CTB) and were used to determine survival time. Twenty-two animals in Group A and 8 animals in Group B were sacrificed and dissected at 21 d post-IPTI, followed by histological examination.

Results: Tumor take rate (tumor developed anywhere in the chest) was 80% in Group A (24/30) and 75% in Group B (12/16); there was no significant difference (P = 0.987). The rate of total chest seeding was significantly higher in Group B (66.7%, 8/12) than in Group A (12.5%, 3/24; P = 0.002). At 3 wk post-IPTI, solitary, localized tumor foci developed at the implantation site in 70% of Group A (21/30); this rate was significantly higher than the 18.8% rate of tumor foci development in Group B animals (3/16; P = 0.001). Twelve of the 16 animals monitored by CT scanning developed tumors. Among them, 7 animals that developed localized intrapulmonary tumors at early time post-IPTI survived significantly longer than the remaining 5 animals that developed extrapulmonary chest seeding tumors (P = 0.001). Intrapulmonary nodules after IPTI may develop granulomas, which were identified by histological examination. Unidentified nodules were detected in CT images, which gradually decreased in size and eventually disappeared.

Conclusion: We establish a simple and effective method for the generation of an intrapulmonary tumor model that yields solitary, localized intrapulmonary tumor. The highlights of this technique are tumor quality control and tumor dissemination control. Extrapulmonary chest seeding at early time post-IPTI contributes to short survival. It is necessary to characterize the intrapulmonary nodules using histological methods prior to the evaluation of therapy; this approach may lead to a more accurate determination of therapeutic outcomes.