Impact of Epithelial–Stromal Interactions on Peritumoral Fibroblasts in Ductal Carcinoma in Situ

Abstract

Background A better definition of biomarkers and biological processes related to local recurrence and disease progression is highly warranted for ductal breast carcinoma in situ (DCIS). Stromal–epithelial interactions are likely of major importance for the biological, clinical, and pathological distinctions between high- and low-risk DCIS cases. Methods Stromal platelet derived growth factor receptor (PDGFR) was immunohistochemically assessed in two DCIS patient cohorts (n = 458 and n = 80). Cox proportional hazards models were used to calculate the hazard ratios of recurrence. The molecular mechanisms regulating stromal PDGFR expression were investigated in experimental in vitro co-culture systems of DCIS cells and fibroblasts and analyzed using immunoblot and quantitative real-time PCR. Knock-out of JAG1 in DCIS cells and NOTCH2 in fibroblasts was obtained through CRISPR/Cas9. Experimental data were validated by mammary fat pad injection of DCIS and DCIS-JAG1 knock-out cells (10 mice per group). All statistical tests were two-sided. Results PDGFRα(low)/PDGFRβ(high) fibroblasts were associated with increased risk for recurrence in DCIS (univariate hazard ratio = 1.59, 95% confidence interval [CI] = 1.02 to 2.46; P = .04 Wald test; multivariable hazard ratio = 1.78, 95% CI = 1.07 to 2.97; P = .03). Tissue culture and mouse model studies indicated that this fibroblast phenotype is induced by DCIS cells in a cell contact-dependent manner. Epithelial Jagged1 and fibroblast Notch2 were identified through loss-of-function studies as key juxtacrine signaling components driving the formation of the poor prognosis-associated fibroblast phenotype. Conclusions A PDGFRα(low)/PDGFRβ(high) fibroblast subset was identified as a marker for high-risk DCIS. The Jagged-1/Notch2/PDGFR stroma–epithelial pathway was described as a novel signaling mechanism regulating this poor prognosis-associated fibroblast subset. In general terms, the study highlights epithelial–stromal crosstalk in DCIS and contributes to ongoing efforts to define clinically relevant fibroblast subsets and their etiology.

Stromal integrin α11 regulates PDGFRβ signaling and promotes breast cancer progression

“…Because of technical limitation related to the lack of anti-integrin α11 antibody suitable on paraffin sections, our IHC study was restricted to frozen BC samples and is worth extending into larger cohorts. Our data are in line with a recent study showing that PDGFRβ + peritumoral fibroblasts constitute a poor prognosis-associated fibroblast phenotype in DCIS (47). In agreement with the clinical data, Itga11 deficiency in mice drastically delayed PyMT tumor growth and reduced lung metastasis.…”

Fibroblasts in urothelial bladder cancer define stroma phenotypes that are associated with clinical outcome

“…Notably, PDGFRa expression did not show an association with tumor stage or grade, neither in the single-marker analysis nor for the PDGFRa-dominant patient cluster. Three recent studies on breast cancer, suggest that PDGFRa expressing fibroblasts are resident fibroblasts also present in normal tissue [33][34][35] , and that these fibroblasts are linked to a good prognosis 33,34 .…”

“…FAP positive fibroblasts were linked to immunosuppressive functions within the tumor microenvironment [28][29][30][31][32] . Stromal PDGFRa was found to decrease with tumor progression [33][34][35] , while a high expression of stromal PDGFRb was associated with a worse prognosis in different solid tumors [36][37][38][39][40][41][42] and drug resistance 43 . Likewise, CD90 defined fibroblasts were adversely associated with clinical outcome 44,45 but were also discussed as immune-regulatory fibroblasts [46][47][48] .…”

A framework for advancing our understanding of cancer-associated fibroblasts

“…1). Contact between cancer cells and fibroblasts can promote the CAF phenotype in breast cancer through Notch signalling 55 ; however, this mechanism is unlikely to be universal as loss of Notch signalling can promote CAF phenotypes in squamous cell carcinoma 56 . Various inflammatory modulators can promote CAF activation, with interleukin-1 (IL-1) acting through NF-κB and IL-6 acting primarily on signal transducer and activator of transcription (STAT) transcription factors 57,58 .…”