Abstract 244: Paclitaxel increases the assembly and function of the tumor microenvironment of metastasis in breast cancer

Abstract

Abstract Chemotherapy induces influx of bone marrow-derived progenitors such as mesenchymal stem cells, endothelial progenitors and proangiogenic monocytes into the primary tumor to promote angiogenesis. Thus it is feared that chemotherapy may potentiate tumor cell invasion and metastasis. Here, we show that paclitaxel delays tumor growth in several mammary carcinoma mouse and human breast cancer models, yet it significantly increases the density of microanatomical sites called “tumor microenvironment of metastasis” (TMEM) that are responsible for tumor cell intravasation and dissemination of breast cancer. The TMEM site consists of a Mena-overexpressing cancer cell in direct contact with a Tie2hi/VEGFhi macrophage and an underlying endothelial cell. Mice treated with paclitaxel have significantly more circulating tumor cells (CTCs) and metastatic foci when compared to vehicle-treated animals indicating that the chemotherapy-induced TMEM are active in assisting tumor cell intravasation. Moreover, syngeneic transplantation of Dendra2+/PyMT tumors into FVB recipients showed significantly higher incidence of Dendra2+ cells in the lung, following paclitaxel administration. In parallel experiments, paclitaxel induced the influx of macrophages and intravasation of cancer cells as observed using intravital imaging of MMTV-PyMT-Dendra2/Cfms-CFP mice, in which blood vessels were visualized with Quantum dots. Furthermore, paclitaxel treatment in experimental mice caused a significant increase in the expression of Mena at the gene and protein levels. PCR assays for total Mena (PanMena) or specific Mena isoforms (MenaINV, Mena11a) revealed that this increase was particularly attributed to the invasive Mena isoforms [i.e. MenaINV and MenaCalc (Menacalc = PanMena - Mena11a)]. These pre-clinical data are supported by the findings from a cohort of 10 breast cancer patients who received neoadjuvant dose-dense paclitaxel followed by doxorubicin/ cyclophosphamide. Of these tumors, 7/10 patients had more than 2-fold increase in TMEM density following neoadjuvant chemotherapy regimen. Moreover, chemotherapy produced an acute increase of up to 150-fold in MenaINV expression in 3/7 and up to 5.5-fold in MenaCalc in 3/4 patients who underwent serial fine needle aspiration (FNA) biopsy before and after 1-2 doses of either neoadjuvant paclitaxel or doxorubicin-cyclophosphamide. This is provocative because an increase in either MenaCalc score or TMEM density are independently associated with increased risk of distant recurrence in breast cancer patients. In conclusion, our data indicate that paclitaxel treatment induces intravasation-mediated dissemination of breast cancer cells in rodents and in certain clinical scenarios in humans by promoting increases in MenaCalc expression and TMEM intravasation sites. Citation Format: George S. Karagiannis, Allison H. Harney, Yarong Wang, Jessica Pastoriza, Jeanine Pignatelli, Jesus Anampa, Joseph A. Sparano, Joan G. Jones, David Entenberg, John S. Condeelis, Maja H. Oktay. Paclitaxel increases the assembly and function of the tumor microenvironment of metastasis in breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 244.