A mouse surgical model for metastatic ovarian granulosa cell tumor

Abstract

We recently described a genetically engineered mouse model that develops ovarian granulosa cell tumors (GCTs) that mimic many aspects of the advanced human disease, including distant dissemination. However, because the primary tumors killed their hosts before metastases were able to form, the use of these mice to study metastatic disease required the development of a simple, reliable, and humane surgical protocol for the excision of large GCTs from debilitated mice. Here we describe a protocol involving multimodal anesthesia, tumor removal through ventral midline celiotomy and perioperative fluid therapy, and analgesia that led to the postoperative survival of more than 90% of mice, despite the removal of tumors representing as much as 10% of the animal's body weight. Intraabdominal recurrence of the GCT did not occur in surviving animals, but most developed pulmonary or adrenal metastases (or both) by 12 wk after surgery. We propose that this mouse model of metastatic GCT will serve as a useful preclinical model for the development of novel treatment modalities and diagnostic techniques. Furthermore, our results delineate anesthetic and surgical principles for the removal of large abdominal tumors from mice that will be applicable to other models of human cancers.

Figure 1.

(A) Celiotomy is performed first by incising the skin with a scalpel blade from the xyphoid process to a few millimeters cranial to the pubic rim. The abdominal cavity then is opened by cutting through the abdominal wall by using small Metzenbaum scissors. Note that the forelimbs were inserted into the anesthesia mask along with the head to stabilize the mouse and facilitate surgery. (B) The first ovarian tumor is exteriorized carefully by using small ophthalmology forceps. The tumors are friable and bleed easily, so careful manipulations are necessary to prevent hemorrhage. (C) Two GCTs isolated from a 39-d-old mouse. The scale is in millimeters. (D) The abdominal cavity of a Pten^{tm1Hwu/tm1Hwu};Ctnnb1^tm1Mmt/+;Amhr2^{tm3(cre)Bhr/+} mouse euthanized 12 wk after surgery (digestive tract and liver removed). Arrows indicate well-healed uterine stumps with no evidence of tumor recurrence. Also note the lack of intraabdominal dissemination. k, Kidney. (E) A pulmonary GCT metastasis (arrow) in the mouse shown in panel D. (F) Adrenal GCT metastases (M) in the mouse shown in panel D.

Figure 2.

Postoperative body weight. Values are presented as means (points) ± SEM (error bars), n = 5 to 10 animals per time point.