Abstract
Simple SummaryTriple-negative breast cancer is an aggressive subtype of breast cancer characterized by tumor angiogenesis and poor patient survival. Here, we analyzed the function of the cell surface molecule Syndecan-1 in tumor angiogenesis in a 3D cell culture system. As a novel finding, we demonstrate that downregulation of Syndecan-1 reduces angiogenesis by decreasing the amount of angiogenesis factors of the tissue factor pathway. Furthermore, we show that the components of this pathway are associated with the prognosis of breast cancer patients. Our study identifies Syndecan-1 and the tissue factor pathway as novel potential therapeutic targets in the aggressive triple-negative subtype of breast cancer, for which no targeted therapies are currently available.Triple-negative breast cancer (TNBC) is characterized by increased angiogenesis, metastasis, and poor survival. Dysregulation of the cell surface heparan sulfate proteoglycan and signaling co-receptor Syndecan-1 is linked to poor prognosis. To study its role in angiogenesis, we silenced Syndecan-1 in TNBC cell lines using a 3D human umbilical vein endothelial cell (HUVEC) co-culture system. Syndecan-1 siRNA depletion in SUM-149, MDA-MB-468, and MDA-MB-231 cells decreased HUVEC tubule network formation. Angiogenesis array revealed reduced VEGF-A and tissue factor (TF) in the Syndecan-1-silenced secretome. qPCR independently confirmed altered expression of F3, F7, F2R/PAR1, F2RL1/PAR2, VEGF-A, EDN1, IGFBP1, and IGFBP2 in SUM-149, MDA-MB-231, and MDA-MB-468 cells. ELISA revealed reduced secreted endothelin-1 (SUM-149, MDA-MB-468) and TF (all cell lines) upon Syndecan-1 depletion, while TF pathway inhibitor treatment impaired angiogenesis. Survival analysis of 3951 patients demonstrated that high expression of F3 and F7 are associated with better relapse-free survival, whereas poor survival was observed in TNBC and p53 mutant basal breast cancer (F3) and in ER-negative and HER2-positive breast cancer (F2R, F2RL1). STRING protein network analysis revealed associations of Syndecan-1 with VEGF-A and IGFBP1, further associated with the TF and ET-1 pathways. Our study suggests that TNBC Syndecan-1 regulates angiogenesis via the TF and additional angiogenic pathways and marks its constituents as novel prognostic markers and therapeutic targets.
Highlights
Breast cancer is the most frequently diagnosed malignant tumor in women worldwide, with over 1.6 million cases each year
After the successful confirmation of siRNAmediated Sdc-1 silencing by ~80% using qPCR (Figure 1A, Supplementary Figure S1A), control and Sdc-1-silenced Triple-negative breast cancer (TNBC) cells were co-cultured with human umbilical vein endothelial cell (HUVEC) and the tube network formation was monitored under 3D co-culture conditions
Our study establishes a novel role for TNBC cell-derived Sdc-1 in regulating components of the tissue factor (TF) pathway and additional angiogenic factors, which promote angiogenesis in a 3D in vitro model
Summary
Breast cancer is the most frequently diagnosed malignant tumor in women worldwide, with over 1.6 million cases each year. It is the main cause of cancer-related mortality among female patients [1]. Based on the expression of the surrogate receptors, breast cancer can be stratified into different molecular subtypes [2] and this reflects the biological diversity of breast cancer [3]. Of the diagnosed breast cancer cases and is characterized by the expression of estrogen receptor (ER) or progesterone receptor (PR) (ER and/or PR) [4]. The TNBC subtype is ER-, PR-, and HER2-negative and represents only 13% of breast cancer cases [4]; it is an aggressive subtype associated with poor outcome
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