Abstract 1410: TMEM (Tumor MicroEnvironment of Metastasis) in human breast cancer is a blood vessel associated intravasation microenvironment unrelated to lymphatics

Abstract

Abstract Observations from intravital imaging (Wyckoff et al. Can Res 2007) and the analysis of Mena function in tumor cells in vivo (Roussos et al. JCS 2011) has characterized an intravasation microenvironment (ME) involved in the systemic dissemination of tumor cells from primary breast tumors. We have identified the corresponding structure in FFPE tissue and called it TMEM (Tumor MicroEnvironment of Metastasis). This microanatomic landmark is defined as the direct apposition of a Mena-overexpressing intravasation competent carcinoma cell, a perivascular macrophage, and an endothelial cell. In a case control study of 60 patients, where each matched pair differed only in their metastatic status - non-metastatic vs. metastatic - the density of TMEM was assessed and found to be significantly associated with development of systemic metastasis (p = 0.00006) (Robinson et al. Clin Can Res 2009). Although lymph node status is considered an important prognostic factor in breast cancer, the direct involvement of lymphatics in systemic tumor cell dissemination from primary tumors has not been demonstrated. In addition, the relationship of hematogenous- and lymphatic-mediated tumor cell spread is not understood. The purpose of this study was to 1) assess intratumoral lymphatic density in this same cohort, 2) determine if TMEM-like structures associated with lymphatics exist, and 3) determine if lymphaticTMEM-like structures correlate with systemic metastatic risk. Cases were stained with a triple immunostain identical to that used in the Robinson et al. study except that D2-40 (a lymphatic marker) was used, rather than CD31 (a blood vessel marker). The marker for macrophages (CD68) and invasive tumor cells (Mena) remained the same. Two pathologists, blinded to outcome, evaluated for the presence or absence of intratumoral lymphatics and quantitated the number of TMEM-like structures per 10 high power (400x) fields in areas of highest intratumoral lymphatic density. A TMEM-like structure was defined as the direct apposition of a lymphatic (D2-40) endothelial cell with a macrophage and invasive tumor cell. Intratumoral lymphatics were absent in a majority of tumors in each of the 2 groups (18 of 30 non-metastatic, 16 of 30 metastatic; p=0.6). TMEM-like structures were rare and were equally present in the 2 groups (3 metastatic and 3 non-metastatic cases). Using the Wilcoxon (paired) signed-rank test, we found no significant difference in the density of these structures between the two groups (p = 0.4). Furthermore, TMEM-like structures did not correlate with the presence of lymph node metastases (p=0.8). We conclude that lymphatic vessels do not participate in the TMEM assembly that has been associated with hematogenous metastasis. TMEM density assessment reflects a hematogenous intravasation ME and offers a novel approach to the assessment of metastatic risk. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1410. doi:1538-7445.AM2012-1410