Abstract 3963: Neoadjuvant chemotherapy promotes prometastatic changes in the primary breast tumor microenvironment in mice and humans

Abstract

Abstract Chemotherapy induces influx of bone marrow-derived proangiogenic Tie2hi monocytes in primary tumors. Tie2hi perivascular macrophages specifically induce the prometastatic Mena isoforms in tumor cells and can assemble specialized microanatomical sites called “tumor microenvironment of metastasis” (TMEM), structures that may serve as doorways for intravasation of tumor cells in mammary tumors. Both TMEM and MenaINV are required for tumor cell intravasation and dissemination. Thus, we hypothesized that chemotherapy may increase the density of TMEM sites and MenaINV-expressing, intravasation-competent tumor cells, resulting in increased tumor cell invasion and metastasis. We studied these potential pro-metastatic effects of chemotherapy in a neoadjuvant setting (NAC) by either administering paclitaxel or a combination of doxorubicin and cyclophosphamide in several mammary carcinoma mouse and human breast cancer models. As expected, chemotherapy delayed tumor growth, yet it significantly increased the recruitment of TMEM-forming, perivascular Tie2hi/Vegfhi macrophages and TMEM density. Using high-resolution multiphoton intravital imaging in live tumor-bearing mice, we observed that paclitaxel also increased the activity of TMEM sites, visualized as endothelial cell tight-junction disruption around TMEM and subsequent intravasation of the migratory cancer cell subpopulation. Indeed, paclitaxel-treated mice have higher numbers of circulating tumor cells, single cell seeding in lungs and incidence and number of micrometastatic foci, all associated with increased TMEM activity, as demonstrated by high-resolution imaging techniques. Tie2 inhibitors reversed paclitaxel-induced pro-metastatic phenotypes without affecting the assembly of TMEM, indicating that Tie2-mediated signaling is required for paclitaxel-mediated cancer cell dissemination via TMEM. Paclitaxel also caused a significant increase in the expression of MenaINV at both the gene and protein levels. Furthermore, paclitaxel treatment in Mena-/- breast tumor-bearing mice resulted in failure to assemble TMEM and to increase circulating-tumor cells and cancer cell metastasis despite the fact that Tie2hi macrophages are attracted to perivascular niches as a result of paclitaxel treatment. This indicated that Mena is involved in the paclitaxel-mediated increase in cancer cell dissemination but not required for Tie2hi macrophage recruitment. These pre-clinical data are further supported by findings from a cohort (N=20) of breast cancer patients, who received pre-operative paclitaxel-based chemotherapy and demonstrated significant increases in TMEM density and MenaINV expression. Together, our data provide solid evidence that NAC leads to metastasis in rodents via TMEM/ MenaINV-mediated mechanisms, and to cancer cell dissemination in certain clinical scenarios in humans. Citation Format: George S. Karagiannis, Jessica Pastoriza, Jeanine Pignatelli, Yarong Wang, Allison S. Harney, David Entenberg, Ved P. Sharma, Emily Xue, Esther Cheng, Timothy M. D'Alfonso, Joan G. Jones, Jesus Anampa, Thomas E. Rohan, Joseph A. Sparano, John S. Condeelis, Maja H. Oktay. Neoadjuvant chemotherapy promotes prometastatic changes in the primary breast tumor microenvironment in mice and humans [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3963. doi:10.1158/1538-7445.AM2017-3963