The pathogenesis of schwannomatosis remains unresolved (S.R. Plotkin et 2018). Previous research has identified mutations in the LZTR1 or SMARCB1 genes in 86% of familial cases and 40% of sporadic cases of schwannomatosis (Kehrer-Sawatzki et 2017; S.R. Plotkin et 2013; C. Louvrier,2018). Tumor development in schwannomatosis often involves mutations in multiple tumor suppressor genes, frequently mediated by large heterozygous deletions on chromosome 22q. These deletions typically encompass SMARCB1, LZTR1, and the NF2 gene (L.B. Jacoby et 1999; S. Mansouri et 2021). The combined loss of these tumor suppressor genes leads to variations in 22q fragments, which are associated with the development of schwannomatosis (J. Antinheimo et 2000; A. Piotrowski et 2022; R. Caltabiano et 2017)However, clear pathogenic mutations are often absent in most sporadic cases of schwannomatosis(R. Sestini et 2008; J. Swensen et 2009)
This study aims to elucidate the molecular differences between schwannomatosis and spinal schwannomas, assess the diagnostic value of candidate genes for schwannomatosis, and analyze potential pathophysiological mechanisms underlying the multiplicity and recurrence of spinal schwannomas. Using sequencing on the Illumina platform, we identified 249 differentially expressed genes (DEGs) between the experimental and control groups, with 70 genes upregulated and 179 downregulated. Through PPI analysis and other machine learning techniques, we highlighted OXTR, CSH1, SNCAIP, and DPP4 as key genes associated with the disease. The diagnostic model constructed with Alignment Diagram and ROC analysis validated these genes, suggesting their collective role in the development of multiple intramedullary schwannomas.
Quantitative PCR (qPCR) results revealed elevated expression of CSH1 in schwannomatosis. CSH1 encodes chorionic somatomammotropin hormone 1 (CSH1), a hormone secreted by placental cells during pregnancy. This protein, produced in the placenta of higher primates, including humans, regulates various metabolic processes during pregnancy (Adu-Gyamfi et 2024). The CSH1 gene is located on human chromosome 17 and is part of the same family as growth hormone (GH) and prolactin (PRL). These hormones influence breast growth, milk secretion, and response to other hormones༈C.-W. Chang et 2022; M.-F. Hivert et 2024༉. While CSH1 plays a crucial role during normal pregnancy by regulating maternal metabolism and stimulating insulin production, its expression is generally low or absent in non-pregnant states. Data from the National Center for Biotechnology Information (NCBI) (PRJEB2445) show that CSH1 expression is minimal in the normal human nervous system (Fig. 12). However, CSH1 has been found to be overexpressed in various tumor cells, including choriocarcinoma(B. Marsh et 2022). The increased expression of CSH1 in schwannomatosis may provide insights into its role in the multiplicity of intramedullary schwannomas.
DEGs were analyzed using KEGG and GO enrichment analyses, which highlighted potential links to immune regulation and inflammatory responses. Key pathways such as Neuroactive Ligand-Receptor Interaction and the PI3K-Akt signaling pathway were identified as central to signal transduction, immune-inflammatory responses, and tumor development. Gene Set Enrichment Analysis (GSEA) further underscored the importance of pathways like PI3K/Akt and mTOR. The PI3K/Akt signaling pathway is critical in numerous physiological processes and plays a pivotal role in disease development, particularly tumors. mTOR, a downstream protein of this pathway, exists in two complexes, mTORC1 and mTORC2, and regulates cellular functions such as transcription, translation, and proliferation through downstream targets like 4E-BP1 and p70S6K. Aberrant activation of mTOR is associated with tumor progression, as seen in gliomas and breast cancer (G. Choe et 2003; M.J. Smith et 2015)
GSEA results for the biomarkers OXTR, CSH1, SNCAIP, and DPP4 revealed significant associations with immune and inflammatory pathways. Notably, the CSH1 gene, which is highly expressed in schwannomatosis, appears to influence the PI3K-Akt-mTOR pathway. This gene may contribute to abnormal mTOR activation, potentially serving as a common risk factor for schwannomatosis (V.L. Merker 2012; Z. Chen et 2020). Therefore, the occurrence of multiple intradural schwannomas in schwannomatosis may be driven by factors associated with the PI3K-Akt signaling pathway and neuroactive ligand-receptor interactions, among other inflammatory responses.
Currently, the treatment of schwannomatosis primarily involves surgical intervention (R.N. Hernandez et 2021). Surgical resection is indicated for cases with spinal cord compression or symptoms related to schwannomas, such as pain or sensory-motor abnormalities, with the goal of controlling symptoms and preserving neurological function (X. Su et 2012; A. Gonzalvo et 2011). However, the surgical management of nerve tumors often risks nerve function damage. There are no established guidelines for radiotherapy, chemotherapy, or targeted therapy in schwannomatosis patients (O. BushML 2011). For patients with extensive spinal schwannomas or very rare malignant schwannomas that are not amenable to surgery(D. Miricescu et 2020; Z. Zou et 2020), targeted therapies are still under investigation. Research into candidate genes and associated pathways like PI3K-Akt may offer insights into potential therapeutic targets. Drugs such as mTOR inhibitors, including Everolimus (RAD001), MLN0128, and AZD014, have been extensively studied for their effects in hematological cancers and solid tumors(H. Li et 2021) However, there is no precedent for their use in schwannomatosis, and further research is needed.
This study aims to elucidate the molecular relationships between spinal schwannomas and schwannomatosis, develop diagnostic models, and identify candidate genes while exploring the mechanisms underlying multiple schwannomas. Clinical application and measurement of these biomarkers require further investigation. Future research should validate the roles of these genes and related pathways through RNA interference, overexpression studies, and pathway inhibition at both cellular and animal levels. Targeting relevant pathways could potentially provide new therapeutic strategies for patients with multiple schwannomas who are not suitable candidates for surgical treatment.