Abstract 1019: T regulatory cells are associated with the M2/alternatively activated macrophage phenotype and the basal-like breast cancer subtype
Authors: Khramtsova Galina , Liao Chuanhong , Li Shihong , Khramtsov Andrey , Nanda Rita 
Published: February 2011

Background: Studies have demonstrated that tumor-associated macrophages (TAMs) are recruited to tumors before malignant conversion and are essential for promoting angiogenesis. We have previously demonstrated that a high % of intratumoral M2/alternatively activated macrophages is associated with high tumor grade, increased microvessel density (MVD) and the basal-like subtype. Increased % of M1/classically activated macrophages is significantly associated with low tumor grade and the luminal A subtype. A recent in vitro study has suggested that T regulatory cells (Tregs) induce alternative activation of macrophages. No study to date has characterized the association between Tregs, macrophage phenotype and molecular subtype in sporadic breast cancers.

Methods: 80 breast tumors and paired normal tissue were obtained from the University of Chicago breast SPORE tissue bank under IRB approved protocols. Molecular subtype was assigned based on immunohistochemical staining into the following groups: luminal A (ER+ and/or PR+, HER2-), luminal B (ER+ and/or PR+, HER2+), HER2-like (ER/PR-, HER2+) and basal-like (ER/PR/HER2-, EGFR+ and/or CK5/6+). Macrophage phenotype was determined using double staining with CD68/CD163 (M2) and CD68/CD80 (M1). The number of Tregs was determined by staining for Foxp3. Microvessel density (MVD) was measured by staining using anti-CD34. Staining quantification was performed independently by two pathologists. To evaluate the association of Tregs with %M1, %M2 and MVD, Spearman's rho correlation coefficients were calculated. Treg density between tumor and normal was compared using the Wilcoxon signed rank test. Breast subtype and tumor grade were associated with Treg density using the Kruskal-Wallis method.

Results: Of the tumors studied, 44 were luminal A, 22 basal-like, 3 HER2-like and 3 luminal B. The mean number of Tregs per mm2 was higher in tumor as compared to paired normal breast tissue (14 vs 0, p&lt;0.001). Treg density was significantly associated with %M2 and inversely correlated with %M1 macrophages (p=0.018 and p=0.033, respectively). The basal-like subtype was associated with a higher median value of Tregs per mm2 as compared to the luminal A subtype (31.5 vs 0, p&lt;0.001). While the density of Tregs increased with grade, this difference was not statistically significant. There was no significant association between Treg density and MVD.

Discussion: We have clearly demonstrated that Treg density increases with tumor progression and is significantly associated with a high proportion of M2 macrophages in human breast tumors. Given the recent in vitro data which suggests that Tregs are responsible for M2 polarization, strategies aimed at blocking the effects of Tregs on the subsequent alternative activation of TAMs may be highly effective in preventing the release of pro-angiogenic cytokines that enable tumor progression.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1019.