CAF-like state in primary skin fibroblasts with constitutional BRCA1 epimutation sheds new light on tumor suppressor deficiency-related changes in healthy tissue

Abstract

Constitutive epimutations of tumor suppressor genes are increasingly considered as cancer predisposing factors equally to sequence mutations. In light of the emerging role of the microenvironment for cancer predisposition, initiation, and progression, we aimed to characterize the consequences of a BRCA1 epimutation in cells of mesenchymal origin. We performed a comprehensive molecular and cellular comparison of primary dermal fibroblasts taken from a monozygous twin pair discordant for recurrent cancers and BRCA1 epimutation, whose exceptional clinical case we previously reported in this journal. Comparative transcriptome analysis identified differential expression of extracellular matrix-related genes and pro-tumorigenic growth factors, such as collagens and CXC chemokines. Moreover, genes known to be key markers of so called cancer-associated fibroblasts (CAFs), such as ACTA2, FAP, PDPN, and TNC, were upregulated in fibroblasts of the affected twin (BRCA1 mosMe ) in comparison to those of the healthy twin (BRCA1 wt ). Further analyses detected CAF-typical cellular features, including an elevated growth rate, enhanced migration, altered actin architecture and increased production of ketone bodies in BRCA1 mosMe fibroblasts compared to BRCA1 wt fibroblasts. In addition, conditioned medium of BRCA1 mosMe fibroblasts was more potent than conditioned medium of BRCA1 wt fibroblasts to promote cell proliferation in an epithelial and a cancer cell line. Our data demonstrate, that a CAF-like state is not an exclusive feature of tumor-associated tissue but also exists in healthy tissue with tumor suppressor deficiency. The naturally occurring phenomenon of twin fibroblasts differing in their BRCA1 methylation status revealed to be a unique powerful tool for exploring tumor suppressor deficiency-related changes in healthy tissue, reinforcing their significance for cancer predisposition.

Hyaluronan, Cancer-Associated Fibroblasts and the Tumor Microenvironment in Malignant Progression

“…Although less well-studied, evidence suggests that chronic inflammation and pro-fibrotic changes in host stroma precede and instruct primary tumor initiation or formation of metastatic colonies by creating a microenvironment or niche favorable for transformation and growth. As examples, in healthy individuals with BRCA1 mutations that are at risk for breast cancer, stromal fibroblasts exhibit a CAF-like activation state (Etzold et al, 2016 ). Similarly healthy individuals with Li Fraumeni syndrome who bear germ line mutations in TP53 and are at an elevated risk of cancer exhibit “cancerization” of their stromal tissues (Pantziarka, 2015 ).…”

“…(DeFilippis et al, 2012 ) and this in breast cancer tissue is strongly associated with poor outcome. Other examples include evidence that primary dermal fibroblasts exhibit a CAF-like state with a germ-line BRCA1 epi-mutation (Etzold et al, 2016 ). These fibroblasts stimulate rather than suppress epithelial proliferation and migration, express CAF markers including ACTA2, FAP, PDPN, and TNC, and are highly proliferative and migratory relative to normal counterparts from other patients.…”

Helicobacter pylori‐activated gastric fibroblasts induce epithelial‐mesenchymal transition of gastric epithelial cells in vitro in a TGF‐β‐dependent manner

“…Corresponding chemokine gradients within gastric walls may direct epithelial cells toward the stroma and promote their further transitions toward the malignant phenotype. This can be accomplished through the establishment of an appropriate “niche” that can contribute to the local colonization of stroma . It may be further facilitated by destabilization of intercellular contacts between epithelial cells .…”

Hypermethylation of RAD9A intron 2 in childhood cancer patients, leukemia and tumor cell lines suggest a role for oncogenic transformation

“…We have previously described monozygotic twin sisters discordant for childhood leukemia and a constitutive mosaic epimutation in the BRCA1 TS gene [16]. Furthermore, we could show that affected broblasts phenotypically resemble cancer-associated broblasts (CAF) [17]. Based on our previous expression ndings [18] we performed an epimutation analysis of RAD9A in a unique cohort, consisting of broblasts derived from individuals who survived childhood cancer and subsequently developed a second primary cancer (2N) and matched ( rst tumor, manifestation age, sex) individuals with childhood cancer but without second cancer (1N).…”