Role of BRAFV600E in the First Preclinical Model of Multifocal Infiltrating Myopericytoma Development and Microenvironment

Abstract

Myopericytoma (MPC) is a rare tumor with perivascular proliferation of pluripotent stem-cell-like pericytes. Although indolent, MPC may be locally aggressive with recurrent disease. The pathogenesis and diagnostic biomarkers of MPC are poorly understood. We discovered that 15% of benign MPCs (thyroid, skin; 3 of 20 samples) harbored BRAF(WT/V600E); 33.3% (1 of 3 samples) of BRAF(WT/V600E)-MPCs were multifocal/infiltrative/recurrent. Patient-MPC and primary MPC cells harbored BRAF(WT/V600E), were clonal and expressed pericytic-differentiation biomarkers crucial for its microenvironment. BRAF(WT/V600E)-positive thyroid MPC primary cells triggered in vitro (8.8-fold increase) and in vivo (3.6-fold increase) angiogenesis. Anti-BRAF(V600E) therapy with vemurafenib disrupted angiogenic and metabolic properties (~3-fold decrease) with down-regulation (~2.2-fold decrease) of some extracellular-matrix (ECM) factors and ECM-associated long non-coding RNA (LincRNA) expression, with no effects in BRAF(WT)-pericytes. Vemurafenib also inhibited (~3-fold decrease) cell viability in vitro and in BRAF(WT/V600E)-positive thyroid MPC patient-derived xenograft (PDX) mice (n = 5 mice per group). We established the first BRAF(WT/V600E)-dependent thyroid MPC cell culture. Our findings identify BRAF(WT/V600E) as a novel genetic aberration in MPC pathogenesis and MPC-associated biomarkers and imply that anti-BRAF(V600E) agents may be useful adjuvant therapy in BRAF(WT/V600E)-MPC patients. Patients with BRAF(WT/V600E)-MPC should be closely followed because of the risk for multifocality/recurrence.

Nuclear β-Catenin Expression is Frequent in Sinonasal Hemangiopericytoma and Its Mimics

“…Myopericytoma shows variable cellularity and a collagenous or sometimes myxoid stroma, and may also show bulging subendothelial proliferation of tumor cells within vessels walls. Consistent genetic alterations have not been identified in myopericytoma, apart from a unique variant characterized by translocation t(7; 12)(p22; q13) which results in ACTB-GLI1 fusion [30][31][32] and a report of BRAF V600E mutations in a subset of myopericytomas [33]. Similar to a prior report [34], nuclear b-catenin expression is consistently absent in myofibroma and is useful in the distinction between sinonasal HPC and myopericytoma.…”

TERT promoter mutations in thyroid cancer: a report from a Middle Eastern population

“…In vitro and in vivo studies showed significant effects of BRAF V600E mutation on the tumor microenvironment promoting invasiveness and angiogenesis. These effects were reversible by the specific anti BRAF inhibitor, Vemurafenib, in tumors harbouring BRAF V600E mutation but not in the WT BRAF tumors (Sadow et al 2014). This suggests that cells other than the epithelial follicular cells from which TC normally arises might harbour mutations that contribute to the progression of cancer.…”

“…These conflicting results might also reflect the role of tumor microenvironment. Recent studies have shown a role for BRAF V600E mutation in thyroid tumors that are mesenchymal in origin (Sadow et al 2014). Sadow et al reported the presence of BRAF V600E mutation in three benign myopericytomas, a rare frequently benign mesenchymal tumor.…”

Simultaneous suppression of the MAP kinase and NF-κB pathways provides a robust therapeutic potential for thyroid cancer

“…In turn, BRAF V600E mutation can cause constitutive activation of the MAPK signaling pathway. BRAF V600E also plays a role in the cellular microenvironment of cancer [13,14]. Thus, the MAPK pathway and its mutated BRAF can be used as therapeutic targets of TC.…”