PDCD4: A Double-Edged Sword in Neurological Diseases.

Programmed Cell Death 4 (PDCD4) is a multifunctional regulator with critically divergent, context-dependent roles: it acts as a tumor suppressor in neuro-oncology but a pathogenic driver in neuroinflammatory and degenerative conditions. Elucidating this functional duality is clinically relevant because PDCD4 dysregulation directly contributes to disease progression in both contexts. Its dual role is governed by disease-specific molecular environments, differential downstream mRNA targeting, and dynamic regulation of its expression and interactions. In gliomas, PDCD4 is frequently downregulated via promoter methylation, non-coding RNA inhibition (e.g., miR-21), and signaling pathway dysregulation (e.g., FAT1-STAT1 axis)-compromising key anti-tumor functions including cell cycle arrest, apoptosis induction, negative regulation of autophagy-lysosomal activity, and reversal of therapy resistance. Conversely, in conditions such as neural injury, neurodegenerative diseases, and mood disorders, PDCD4 is pathologically upregulated. Here, it exacerbates damage by driving the activation of pro-inflammatory pathways (e.g., MAPK/NF-κB, NLRP3 inflammasome), inducing neuronal death (apoptosis/ferroptosis), and impairing repair processes such as axonal growth by suppressing neurotrophic factors like brain-derived neurotrophic factor (BDNF). A multilayered regulatory network centered on miRNA-mediated control (notably miR-21), and expanded by epigenetic modifications and competitive endogenous RNA mechanisms, orchestrates its context-specific expression and activity. Current research gaps include an incomplete understanding of regulatory synergies, cell-type-specific functions, and key molecular interactions. Future studies employing multi-omics and cell-specific tools are needed to decipher these mechanisms and develop targeted therapeutic strategies.