Syndecan-1 is a novel molecular marker for triple negative inflammatory breast cancer and modulates the cancer stem cell phenotype via the IL-6/STAT3, Notch and EGFR signaling pathways

Abstract

BackgroundInflammatory breast cancer (IBC), a particularly aggressive form of breast cancer, is characterized by cancer stem cell (CSC) phenotype. Due to a lack of targeted therapies, the identification of molecular markers of IBC is of major importance. The heparan sulfate proteoglycan Syndecan-1 acts as a coreceptor for growth factors and chemokines, modulating inflammation, tumor progression, and cancer stemness, thus it may emerge as a molecular marker for IBC.MethodsWe characterized expression of Syndecan-1 and the CSC marker CD44, Notch-1 & -3 and EGFR in carcinoma tissues of triple negative IBC (n = 13) and non-IBC (n = 17) patients using qPCR and immunohistochemistry. Impact of siRNA-mediated Syndecan-1 knockdown on the CSC phenotype of the human triple negative IBC cell line SUM-149 and HER-2-overexpressing non-IBC SKBR3 cells employing qPCR, flow cytometry, Western blotting, secretome profiling and Notch pharmacological inhibition experiments. Data were statistically analyzed using Student’s t-test/Mann-Whitney U-test or one-way ANOVA followed by Tukey’s multiple comparison tests.ResultsOur data indicate upregulation and a significant positive correlation of Syndecan-1 with CD44 protein, and Notch-1 & -3 and EGFR mRNA in IBC vs non-IBC. ALDH1 activity and the CD44(+)CD24(-/low) subset as readout of a CSC phenotype were reduced upon Syndecan-1 knockdown. Functionally, Syndecan-1 silencing significantly reduced 3D spheroid and colony formation. Intriguingly, qPCR results indicate downregulation of the IL-6, IL-8, CCL20, gp130 and EGFR mRNA upon Syndecan-1 suppression in both cell lines. Moreover, Syndecan-1 silencing significantly downregulated Notch-1, -3, -4 and Hey-1 in SUM-149 cells, and downregulated only Notch-3 and Gli-1 mRNA in SKBR3 cells. Secretome profiling unveiled reduced IL-6, IL-8, GRO-alpha and GRO a/b/g cytokines in conditioned media of Syndecan-1 knockdown SUM-149 cells compared to controls. The constitutively activated STAT3 and NFκB, and expression of gp130, Notch-1 & -2, and EGFR proteins were suppressed upon Syndecan-1 ablation. Mechanistically, gamma-secretase inhibition experiments suggested that Syndecan-1 may regulate the expression of IL-6, IL-8, gp130, Hey-1, EGFR and p-Akt via Notch signaling.ConclusionsSyndecan-1 acts as a novel tissue biomarker and a modulator of CSC phenotype of triple negative IBC via the IL-6/STAT3, Notch and EGFR signaling pathways, thus emerging as a promising therapeutic target for IBC.Electronic supplementary materialThe online version of this article (doi:10.1186/s12943-017-0621-z) contains supplementary material, which is available to authorized users.

Epigenetic loss of heparan sulfate 3‐O‐sulfation sensitizes ovarian carcinoma to oncogenic signals and predicts prognosis

“…Syndecan‐1 and syndecan‐4 are HSPGs with three HS moieties at the extracellular domain and show higher and denser expression in ovarian carcinoma . Syndecan‐1 regulates the IL‐6 and EGF signaling pathways in breast cancer . In endothelial cells, 3‐O‐sulfated HS inhibits VEGF signaling .…”

“…42 Syndecan-1 regulates the IL-6 and EGF signaling pathways in breast cancer. 33,43 In endothelial cells, 3-O-sulfated HS inhibits VEGF signaling. 38 Taken together, HS3ST2 modifies HS on HSPGs to fine tune ligand-receptor interactions.…”

A shift from membranous and stromal syndecan‐1 (CD138) expression to cytoplasmic CD138 expression is associated with poor prognosis in breast cancer

“…[14][15][16][17] Thirteen different studies have analyzed the impact of CD138 expression on BCa prognosis analyzing 37 to 254 cancers by immunohistochemistry and described complex staining patterns including membranous, cytoplasmic, and stromal staining. [18][19][20][21][22] The conclusions from these studies were highly controversial, however, the authors described both increased, 17,23,24 and decreased 25 CD138 expression in BCa as compared to normal breast epithelium and reported associations of high CD138 expression with possibly favorable 25 and unfavorable, 17,20,23 prognosis.…”

Identification of key molecular targets that correlate with breast cancer through bioinformatic methods

“…Paclitaxel (PTX) and alendronate (ALN) were effective drugs for the treatment of breast cancer bone metastases, and PTX–polyethylene glycol–ALN micelles achieved improved efficacy and safety profiles in syngeneic and xenogeneic mouse models of mCherry‐infected mammary adenocarcinoma . Syndecan‐1 was considered as a novel molecular marker for triple negative inflammatory breast cancer and modulated the cancer stem cell phenotype via the interleukin‐6/signal transducer and activator of transcription 3, Notch and epidermal growth factor receptor signaling pathways . In addition, the targeted delivery of Polo‐like kinase 1 siRNA was considered to be a novel nanoparticle platform with intrinsic antimetastatic properties .…”

“…6 Syndecan-1 was considered as a novel molecular marker for triple negative inflammatory breast cancer and modulated the cancer stem cell phenotype via the interleukin-6/signal transducer and activator of transcription 3, Notch and epidermal growth factor receptor signaling pathways. 7 In addition, the targeted delivery of Polo-like kinase 1 siRNA was considered to be a novel nanoparticle platform with intrinsic antimetastatic properties. 8 Based on the results of affinity purification, liquid chromatography-tandem mass spectrometry and proteomics, keratin 1 was identified as the target receptor highly expressed on breast cancer cells.…”