Transforming growth factor-beta dependent signaling drives tumor growth and aberrant extracellular matrix dynamics in NF1-associated plexiform neurofibroma

Plexiform neurofibromas (PNF) are benign tumors of the peripheral nervous system that represent a major source of morbidity in persons with neurofibromatosis type 1 (NF1). A significant proportion of individuals do not respond to current therapies or experience intolerable side effects. Here, we performed a systematic transcriptomic characterization of murine and human PNF at the bulk and single cell level and identified TGF-beta (TGFβ) signaling as a key upstream regulator in PNF, driving aberrant production of basement membrane (BM) proteins by both neoplastic Schwann cells and fibroblasts. Furthermore, we show that conditional overexpression of TGFβ1 in Nf1 deficient Schwann cells driven by Hoxb7-Cre promotes PNF growth and malignant transformation in vivo. Conversely, pharmacologic inhibition of the type I TGFβ receptor (TGFβRI) reduced PNF tumor burden in Nf1 mutant mice. Proteomic characterization of the extracellular matrix (ECM) revealed a reduction in BM proteins in response to TGFβRI inhibition. Collectively, these studies implicate the TGFβ pathway as a potential therapeutic target in PNF and provide insights into the role of TGFβ signaling in orchestrating ECM dynamics in the PNF microenvironment. PNF bearing sciatic nerve tissues pooled from five, 11-month-old Nf1flox/flox;PostnCre+ mice were harvested, flash frozen at -80°C and shipped on dry ice to Novogene for single nucleus capture, library preparation and sequencing. Single nuclei suspensions were loaded onto Chromium Chips (10x Genomics) for 3’ library preparation according to the manufacturer’s recommendations. Library quality control was performed by Qubit 2.0 for preliminary determination of the library concentration, Agilent 2100 to determine the insert size, and Q-PCR to precisely quantify the library effective concentration. The resulting library was sequenced on an Illumina sequencing platform at a depth of 106,831 mean reads per cell across an estimated 6,881 cells with 24,062 total genes detected and a median of 1,654 genes per cell.