Abstract 1105: Tumor cells of the early metastatic process show up regulation of cytokine genes involved in migration of inflammatory cells
Authors: Tapia Coya , Su Xiaoping , Tang Ximing , Kakaral Lakshmi , Sahin Aysegul , Lu Wei , Wistuba Ignacio I. 
Published: August 2018

Background: Patients with metastatic breast cancer have poorer prognosis and distant metastasis is the main cause of breast cancer (BC) deaths. Hence, better understanding of the early metastatic process is needed. Most BC metastasize primarily lymphogenic and tumor cells within the lympho-vascular space are the first clear visible step in the metastatic process. However, these cells are hardly investigated since the tumor area is very small and therefore difficult to analyze. In this study we wanted to show that tumor cells within the lympho-vascular space can be analyzed for gene expression and that differences compared between main tumor mass and lympho vascular invasion (LVI) occur. Methods: We included 20 BCs diagnosed at UT MD Anderson Cancer Center between 2010 and 2015. The cohort showed the following characteristics: Invasive ductal (n=18), lobular (n=1), ductulo-lobular (n=1), ER positive (n=18), ER negative (n=2), PgR positive (n=15), PgR negative (n=5), Her2 negative (n=16), and Her2 positive (n=4). Suitable FFPE tissue blocks were identified for all BCs. Ten µm sections were performed, air-dried and stained with methyl-green for visualization of the morphology. Macro-dissection and measurement of the tumor area (LVI) was done under a stereo microscope. Afterwards, HTG Seq quantitative assay of the oncology biomarker panel (2,560genes) was performed with some modifications to the standard protocol. Results: The macro-dissection was successful for both, LVI and main tumor mass, in 19 BCs. The dissected areas were between 11-60mm2. Eighteen samples could be included for RNA expression analysis. The main tumor mass and LVI showed clearly different expression patterns (clustering). LVI showed down regulation of genes coding for collagens (COL3A1, COL5A1), or genes involved in the interaction with the extracellular matrix (SPARC, VCAN). Up regulation was seen for genes coding for chemotactic factors involved in migration of inflammatory cells such as CCL18 for B-lymphocytes, CCL27 that seems to play a role in homing of lymphocytes to the skin, or CCL2 that is involved in recruiting monocytes and basophils. Conclusion: We showed that RNA expression analysis is feasible on small amount of tumor cells dissected from LVI that were stained with methyl green. Additionally, we could show that tumor cells from the main tumor mass and LVI have different gene expression levels and show clear clustering. Down regulation was seen in genes interacting with the extracellular matrix may indicating that these interactions are not needed when floating in lymphatic vessels. Interestingly, LVI showed upregulation of genes involved in the migration of white blood cells what could be an indication that tumor cells might relay on the same cytokines for migration in lymphatic vessels as inflammatory cells.

Citation Format: Coya Tapia, Xiaoping Su, Ximing Tang, Lakshmi Kakaral, Aysegul Sahin, Wei Lu, Ignacio I. Wistuba. Tumor cells of the early metastatic process show up regulation of cytokine genes involved in migration of inflammatory cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1105.