Abstract P1-07-27: Neutrophil elastase modulates breast cancer progression by fostering collective cell detachment and tumor emboli dissemination
Authors: Marchio Caterina , Annaratone Laura , Balmativola Davide , Scalzo Maria Stella , Bolla Stefania , Grasso Silvia , Russo Isabella , Fusella Federica , Macrì Luigia , Brancaccio Mara , Defilippi Paola , Sapino Anna 
Published: May 2015

Abstract
Proteases constitute a large family of enzymes involved in several processes, including degradation and remodeling of the extracellular matrix to drive dissemination of cancer cells into adjacent tissue. Within this large family, the serine protease neutrophil elastase (NE) has been proven clinically meaningful in breast cancer. Indeed, high levels of NE correlate with poor outcome and endocrine resistance in breast cancer patients.
In an experimental model it has been demonstrated that estrogen receptor positive (ER+) MCF7 breast cancer cells grow in suspension as 3D-spheroids in NE-addicted medium, thus resembling the micropapillae of a human breast cancer characterized by high propensity to metastasize, i.e. the micropapillary carcinoma. We hypothesized that NE may produce disarrangement of tumor cell adhesion to the substrate fostering neoplastic lymphovascular invasion (LVI) and metastasis. ER+/E-Cadherin (E-CAD)+/HER2- (MCF7, T-47D, ZR-75-1), ER+/E-CAD+/HER2+ (BT-474), ER-/E-CAD-/HER2+ (SK-BR-3) and ER-/E-CAD-/HER2- (MDA-MB-231) cells were grown with serine proteases (NE, cathepsin-G), hyaluronidase and collagenase. NE and cathepsin-G led to 3D-spheroid formation of ER+/E-CAD+ cells only. In 3D-spheroids from MCF7 cells grown with NE the luminal Epithelial Membrane Antigen (EMA) lined the external border of cell clusters, which faced cancer associated fibroblasts in co-cultures experiments, thus recapitulating the inverted polarity of MPCs. MCF7 3D-spheroids were tamoxifen resistant. Injection of NE in tumors of MCF7 cells in SCID mice triggered neoplastic cluster detachment, micropapillae, vascular emboli similar to 3D-spheorids and metastases. In a cohort of human breast carcinomas with LVI the MCF7-3D-spheroid-alike pattern was the most prevalent in tumor emboli. Immunohistochemical NE expression was mainly detected in polymorphous neutrophilic granulocytes (PMNs) within vessels and in the stroma and PMNs were significantly higher in breast carcinomas with LVI. In fully developed metastases within lymph-nodes, which reverted the EMA expression as in the primary tumor, no NE+ PMNs were observed. Our results may explain why high levels of NE negatively act on patient prognosis by creating a favorable environment for breast cancer invasion and metastasis.
Citation Format: Caterina Marchio, Laura Annaratone, Davide Balmativola, Maria Stella Scalzo, Stefania Bolla, Silvia Grasso, Isabella Russo, Federica Fusella, Luigia Macrì, Mara Brancaccio, Paola Defilippi, Anna Sapino. Neutrophil elastase modulates breast cancer progression by fostering collective cell detachment and tumor emboli dissemination [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-07-27.