Tumor-associated macrophages drive spheroid formation during early transcoelomic metastasis of ovarian cancer
Mingzhu Yin, … , Ge Lou, Wang Min
Mingzhu Yin, … , Ge Lou, Wang Min
Published October 10, 2016
Citation Information: J Clin Invest. 2016;126(11):4157-4173. https://doi.org/10.1172/JCI87252.
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Research Article Inflammation Oncology

Tumor-associated macrophages drive spheroid formation during early transcoelomic metastasis of ovarian cancer

Abstract

Tumor-associated macrophages (TAMs) can influence ovarian cancer growth, migration, and metastasis, but the detailed mechanisms underlying ovarian cancer metastasis remain unclear. Here, we have shown a strong correlation between TAM-associated spheroids and the clinical pathology of ovarian cancer. Further, we have determined that TAMs promote spheroid formation and tumor growth at early stages of transcoelomic metastasis in an established mouse model for epithelial ovarian cancer. M2 macrophage–like TAMs were localized in the center of spheroids and secreted EGF, which upregulated αMβ2 integrin on TAMs and ICAM-1 on tumor cells to promote association between tumor cells and TAM. Moreover, EGF secreted by TAMs activated EGFR on tumor cells, which in turn upregulated VEGF/VEGFR signaling in surrounding tumor cells to support tumor cell proliferation and migration. Pharmacological blockade of EGFR or antibody neutralization of ICAM-1 in TAMs blunted spheroid formation and ovarian cancer progression in mouse models. These findings suggest that EGF secreted from TAMs plays a critical role in promoting early transcoelomic metastasis of ovarian cancer. As transcoelomic metastasis is also associated with many other cancers, such as pancreatic and colon cancers, our findings uncover a mechanism for TAM-mediated spheroid formation and provide a potential target for the treatment of ovarian cancer and other transcoelomic metastatic cancers.

Authors

Mingzhu Yin, Xia Li, Shu Tan, Huanjiao Jenny Zhou, Weidong Ji, Stefania Bellone, Xiaocao Xu, Haifeng Zhang, Alessandro D. Santin, Ge Lou, Wang Min

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Figure 5

Clinical relevance of spheroid formation between EGF+ TAMs and EGFR+ tumor cells in OC patients.

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Clinical relevance of spheroid formation between EGF+ TAMs and EGFR+ tum...
(A and B) Macrophages and spheroids in human OC. (A) H&E and CD68 IHC staining of primary tumors and spheroids isolated from OC patients. Scale bars: 50 μm (H&E); 25 μm (CD68). (B) Statistical analysis of CD68-positive cells in primary tumors and spheroids of OC patients. n = 128. Data are presented as mean ± SEM. ***P < 0.001 (2-sided Student’s t test). (C and D) Correlations between macrophages and cancer cell proliferation in spheroids. (C) Immunostainings of CD68 and Ki67 in small, medium, and large spheroids of human OC. DAPI is used for nucleus staining. Representative images are shown. Scale bars: 5 μm. (D) Quantifications of CD68- and Ki67-positive cells in spheroids. n = 30. Small spheroid (0–50 cells/spheroid); medium cell cluster (50–500 cells/spheroid); large spheroid (≥500 cells/spheroid). Data are presented as mean ± SEM. **P < 0.01; ***P < 0.001 (2-sided Student’s t test) comparing medium and large spheroids with small spheroids. (E) Immunofluorescent staining of spheroids harvested from ascites of OC patients. Costainings of CD68 with EGF or EGFR (E). Representative images of spheroids from n = 128 OC patients are shown. CD68+EGF+ TAMs in the center of spheroids are indicated by arrows. Scale bars: 10 μm. (F) Statistical analysis of CD68+ cells in OC spheroids with different histological differentiation (2-sided Student’s t test, A–F). (G) Kaplan-Meier curves for OS in 128 OC patients with low (≤14.5%) or high (≥14.5%) percentage of CD68+ cells in OC spheroids (analyzed with log-rank test)