Downregulation of OPCML Is Associated with Activation of AKT Signaling and Aggressive Phenotypes in Glioblastoma Cells

Zhixin Liu¹Chunhua Xu²Wu Zhou³Yihao Liu^4*Wenrui Wu^5*

• ¹First Affiliated Hospital of Fujian Medical University, Fuzhou, China
• ²The First Affiliated Hospital of Nanchang University, Nanchang, China
• ³The Affiliated Hospital of Jiangxi University of Traditional Chinese Medicine, Nanchang, China
• ⁴Xiangyang Central Hospital, Xiangyang, China
• ⁵Nanchang County People's Hospital, Nanchang, China

Background: OPCML, a GPI-anchored IgLON adhesion molecule with brain-enriched expression, has tumour-suppressive roles in several epithelial cancers, but its position in glioblastoma (GBM) biology is unclear. Methods: We integrated two bulk microarray cohorts to derive a reproducible GBM signature and re-analysed scRNA-seq data to localise OPCML at single-cell resolution. Tissue distribution and clinical associations were evaluated using HPA and TCGA, with survival modelling and a nomogram. Co-expression, STRING-based protein interaction, and GO/KEGG enrichment analyses outlined the molecular context. Immune infiltration was profiled by ssGSEA and cross-checked on TIMER2. Functional validation used a single OPCML siRNA with a non-targeting siRNA control (siNC) in U87 and U251 cells with Transwell invasion, wound-healing, colony formation, CCK-8 proliferation, and western blotting for p-AKT and p-mTOR, with LY294002 rescue. Results: OPCML was consistently down-regulated in GBM and across multiple cancers; within GBM, lower expression associated with higher grade, older age, IDH-wild type, and poorer overall survival. At single-cell level, OPCML transcripts were largely confined to a neuron–glia-hybrid population and were scarce in classical malignant clusters. Genome-wide correlations in GBM showed positive links to extracellular-matrix/synaptic programs and negative links to cell-cycle/DNA-replication pathways. In vitro, OPCML knockdown increased invasion, migration, clonogenic growth, and CCK-8 readouts, and was associated with elevated p-AKT and p-mTOR; PI3K inhibition reversed the signaling changes. Pan-cancer, OPCML tracked with denser immune signatures, whereas in GBM it correlated inversely with multiple effector populations and with CAF estimates across deconvolution methods. Conclusions: OPCML marks a neuron-leaning, less aggressive state and is associated with the regulation of PI3K–AKT–mTOR signaling in GBM. Loss of OPCML aligns with proliferative programmes and a GBM-specific immune pattern. These data nominate OPCML as a prognostic marker and a surface-level modulator that could be leveraged alongside RTK/PI3K-axis inhibitors in GBM.