Abstract 1090: Type 2 endometrial cancer is associated with an M1 subtype, tumor associated macrophage polarization in the stromal compartment
Authors: Kelly Michael G. , Francisco Antonio M.C. , Cimic Adela , Wofford Anne , Fitzgerald Nora , Yu Jie , Taylor Robert N. 
Published: May 2015

Objectives: The more aggressive behavior of type 2 than type 1 endometrial cancers may be due to differences in their tumor microenvironments. In other solid cancers, tumor associated macrophages (TAMs) play a pivotal role in orchestrating the microenvironment. TAMs differentially polarize into M1 or M2 macrophages with distinct cytokine secretion patterns and actions. The aim of our work is to characterize the density, subtype and distribution of TAMs in endometrial hyperplasia and cancer.

Methods: Five patients with complex atypical hyperplasia (hyperplasia), 5 patients with grade 1, non-invasive endometrioid adenocarcinoma (type 1) and 5 patients with uterine papillary serous carcinoma (type 2) were included. Formalin-fixed, paraffin-embedded sections from each specimen were stained with anti-CD68 and anti-CD163 monoclonal antibodies as markers for total TAMs and M2 TAMs, respectively. M1 macrophages were estimated by subtraction of CD163+ from CD68+ densities. Macrophages were counted at 40x magnification in 10 fields per slide by 4 observers. Repeated measure models, accounting for intra- and inter-observer correlation were contstructed and the compound symmetry covariance method was used to determine the relationship between macrophages and cancer. To establish an in vitro model, immortalized histiocytic lymphoma (U937) cells were differentiated to macrophages and treated with LPS to induce a M1 phenotype. Supernatants were applied to Cytokine C1000 microarray (RayBiotech) to screen for differentially expressed cytokines.

Results: The correlation between the 4 observers was robust (r=0.71). Most TAMs were located in the stromal (mean=41.0/field) compared to epithelial (mean=11.0) or luminal (mean=11.6) compartments (p&lt;0.0001). The mean total TAM density was highest in patients with type 2 cancers (mean=90.1/field), followed by type 1 cancers (mean=51.4) and hyperplasias (mean=41.1, p&lt;0.0001). The calculated density of M1 macrophages was higher in type 2 cancers (mean=71.7) compared to type 1 cancers (mean =36.4, p&lt;0.0001). This difference was only observed in the stromal compartment (p&lt;0.0001). In the in vitro M1 macrophage model, ENA-78, a neutrophil chemo-attractant, and IL-6 were expressed at the highest concentrations.

Conclusions: Type 2 cancers have nearly twice the TAM density of type 1 cancers. This difference is due to M1 macrophage predominance in the stroma of type 2 cancers. We postulate that cytokines produced by M1 TAMs within the tumor stroma contribute to the aggressive biology of these cancers. Future experiments will determine how well the in vitro model mimics M1 TAMs in the tumor microenvironment.

Citation Format: Michael G. Kelly, Antonio M.C. Francisco, Adela Cimic, Anne Wofford, Nora Fitzgerald, Jie Yu, Robert N. Taylor. Type 2 endometrial cancer is associated with an M1 subtype, tumor associated macrophage polarization in the stromal compartment. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1090. doi:10.1158/1538-7445.AM2014-1090