It is well established that primary tumour can modify secondary organs long before the circulating tumor cells reach their metastatic targets. These modifications are mainly exerted through tumor-secreted factors and can act on several cell types to form what is called the pre-metastatic niche. Pre-metastatic endothelial niche play a key role in the extravasation process during metastasis. Here we describe the effect of the mixture of secreted factors by tumor cells over endothelial changes that facilitates tumor cell transendothelial migration.
Adhesion assay Human umbilical vein endothelial cells (HUVEC) cells were stimulated or not with TNF-α [10ng/ml] or Tumor Secreted Factors (TSFs) [10 µg/ml] from MDA-MB-231 or MCF-7 cell lines. HUVEC monolayers were co-cultured with a U937(3H) cells. After 3h firm attached U937(3H) were lysed and radioactivity was measured. Vascular permeability assay HUVEC monolayers were cultured in Boyden chambers. Cells were stimulated or not with TNF-α [10ng/ml] or TSFs [10 µg/ml] and incubated for 12h. Afterwards a dextran-FITC solution was added for 20 min and the bottom well fluorescence was quantified. Transendothelial migration assay HUVEC monolayers were cultured in Boyden chambers. Cells were stimulated or not with TNF-α [10ng/ml] or TSFs [10 µg/ml] and incubated for 10h. Fluorescent labeled MDA-MB-231 cell suspension 2x104 was added (24h) and the migrant cells were counted under an epifluorescence microscope.
Adhesion assay revealed that HUVEC stimulated with MDA-231 TSFs attached U937 cells 6-fold comparing to the MCF-7 TSFs or control, in a similar way as TNF-α did. The MDA-TSFs were able to increase the HUVEC monolayer permeability exceeded about 30% of the TNF-α induced permeability. A 1.5-fold increase of transendothelial migration cells was observed in HUVEC stimulated with MDA-MB-231 TSFs.
Tumor secreted factors derived from highly metastatic cell line MDA-MB-231 are capable to induce a premetastatic-like endothelial state, increasing the tumor cell transendothelial migration, adhesion to the HUVEC monolayer as well as vascular permeability enhancement.
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Legal entity responsible for the study
Instituto de Investigaciones Biomédicas, UNAM
Programa de Doctorado en Ciencias Biomédicas, Universidad Nacional Autónoma de México (UNAM), fellowship 509589 from CONACYT.
All authors have declared no conflicts of interest.