Humanized mouse model of ovarian cancer recapitulates patient solid tumor progression, ascites formation, and metastasis

Abstract

Ovarian cancer is the most common cause of death from gynecological cancer. Understanding the biology of this disease, particularly how tumor-associated lymphocytes and fibroblasts contribute to the progression and metastasis of the tumor, has been impeded by the lack of a suitable tumor xenograft model. We report a simple and reproducible system in which the tumor and tumor stroma are successfully engrafted into NOD-scid IL2Rγ(null) (NSG) mice. This is achieved by injecting tumor cell aggregates derived from fresh ovarian tumor biopsy tissues (including tumor cells, and tumor-associated lymphocytes and fibroblasts) i.p. into NSG mice. Tumor progression in these mice closely parallels many of the events that are observed in ovarian cancer patients. Tumors establish in the omentum, ovaries, liver, spleen, uterus, and pancreas. Tumor growth is initially very slow and progressive within the peritoneal cavity with an ultimate development of tumor ascites, spontaneous metastasis to the lung, increasing serum and ascites levels of CA125, and the retention of tumor-associated human fibroblasts and lymphocytes that remain functional and responsive to cytokines for prolonged periods. With this model one will be able to determine how fibroblasts and lymphocytes within the tumor microenvironment may contribute to tumor growth and metastasis, and will make it possible to evaluate the efficacy of therapies that are designed to target these cells in the tumor stroma.

Figure 1. Histology of the original tumor.

A section of a papillary serous adenocarcinoma of the ovary stained with hemotoxylin and eosin (H&E). Shown in A 100× magnification and in B 400× magnification clusters of tumor cells (T) that show lymphocytic infiltration (L), along with fibrous connective tissue (F).

Figure 2. Presence of tumor, T cells and fibroblasts in tumor cell aggregates.

Histology and immunohistochemistry of tumor-derived cell aggregates derived by mild disruption of a primary ovarian tumor. H&E staining show clusters of cells of different sizes (A) Immunohistochemical staining for human CD45 (B) and CD3 (C) shows evidence of human leukocytes and T cells, i.e. dark brown stained cells. Trichrome staining (D) reveals the presence of collagen which is produced by fibroblasts and stains aquamarine. Tumor cells stain dark brown with immunohistochemical stain for cytokeratin (E). All figures are at 400× magnification.

Figure 3. Tumor and stroma in multiple organs in NSG mice following injection of tumor aggregates.

H&E staining shows evidence of tumor (see arrows) in peritoneal nodule from omentum (Aa and Ab), ovary and periovarian fat (Ac), pancreas (Ad), uterus (Ae), spleen (Af), and liver (Ag). These tumors resulted from the i.p. injection of tumor-derived cell aggregates derived from a papillary serous carcinoma of the ovary. Mice were sacrificed 140 days post inoculation. Lymphocytes (arrow) were observed in juxtaposition with tumor cell (arrowhead) (Ba). Immunohistochemical staining (B) shows the presence of human CD45+ leukocytes (Bb), CD3+ T cells (Bc), CD20+ B cells (Bd), CD138+ plasma cells (Be), and HLA+ tumor nodule adjacent to the ovary (Bf). Proliferation of tumor cells is shown by positive stain with KI67 (Bg), and evidence of stromal fibroblasts illustrated by trichrome staining of collagen see arrows (Bh). Arrow head shows tumor cells. All sections in A are at 100× magnification and in B the sections are at 400× magnification.

Figure 4. Spontaneous metastasis of tumor xenograft into the lung.

H&E staining (100× magnification) reveals the presence of tumor in the diaphragm (A), and in the lung 100× magnification (B) and 400× magnification (C). The immunohistochemical staining of the tumor in the lung for HLA Class I (D) establishes that these tumors are of human origin. The sections were made from the tissues of a mouse 16 weeks after the i.p. injection of a suspension of tumor = derived cell aggregates.