Natural history of SPP1 signaling in NF1 tumors.

Understanding the heterogeneity of Neurofibromatosis type 1 (NF1)-associated tumors and delineating the natural historical evolution of cell signaling are essential for interpreting tumor initiation, preventing tumor progression from benign plexiform neurofibromas (pNFs) to malignant peripheral nerve sheath tumors (MPNSTs), and engineering effective treatments. The neural crest-derived Schwann cell precursor (SCP)-like tumor population interacts with different cells in the tumor microenvironment (TME), particularly macrophages, continually shaping the intrinsic and extrinsic NF1 tumor heterogeneity. Through integrated analyses of single-cell RNA-seq (scRNA-seq) and spatial transcriptomics, we reveal that SPP1-CD44 signaling is initiated by SCP-like tumor cells in pNF, operating through autocrine mechanisms. However, in MPNST, a distinct subset of macrophages becomes the dominant SPP1 signaling source while the SCP-like cells maintain autocrine signaling. The role of SPP1 in tumorigenesis is validated by the significantly extended survival in the MPNST mouse model with cisNf1^+/-;Trp53^+/-;Spp1^-/- configuration. Notably, our analysis of the pre-tumor stage in the DhhCre;Nf1^-/- pNF mouse model demonstrates upregulated Spp1 expression compared to control tissue in Nes⁺ Schwann lineage cells. Together, these findings elucidate the natural historical dynamics of SPP1-CD44 signaling during tumor initiation and progression from pNF to MPNST, and highlight the SPP1-CD44 signaling axis as a potential therapeutic target to disrupt tumor stemness properties and reprogram the immune TME in malignancies.