From Epigenetic Constraint to Evolutionary Escape: Cell-State Transitions and Selective Pressures During Malignant Transformation in Lower-Grade Gliomas.

Lower-grade gliomas (LGGs) often follow a relatively protracted clinical course; however, a substantial proportion eventually undergo malignant transformation to high-grade, treatment-refractory disease. This process has traditionally been interpreted in the context of stepwise histopathologic progression and recurrent genetic alterations. Increasing evidence, however, suggests that malignant transformation is more accurately understood as an evolutionary process shaped by the interplay among epigenetic constraints, cell-state plasticity, and selective pressures. In this review, we examine current evidence supporting a model in which early LGGs, particularly isocitrate dehydrogenase (IDH)-mutant tumors, are initially maintained in relatively restricted cellular states by metabolically imposed epigenetic programs, but progressively escape these constraints under the cumulative influence of therapy, hypoxia, immune remodeling, and genomic instability. We summarize recent advances demonstrating that progression from lower-grade to high-grade disease is accompanied by cell-state transitions characterized by altered lineage identity, acquisition of stem-like features, increased proliferative capacity, and adaptation to cellular stress. We further discuss how these transitions are reinforced by microenvironmental evolution, including vascular remodeling, extracellular matrix reorganization, and changes in immune composition, thereby creating conditions that favor clonal expansion, invasion, and therapeutic resistance. Particular attention is given to longitudinal, single-cell, and spatially resolved studies, which collectively indicate that malignant transformation is not a discrete event but a continuous process of evolutionary selection and phenotypic reprogramming. Finally, we discuss the translational implications of this framework for early risk stratification, biomarker development, and mechanism-based therapeutic intervention. By reframing malignant transformation in LGGs as a process of cell-state escape under persistent selective pressure, this review aims to provide an integrated view of glioma progression and to highlight new opportunities for precision monitoring and treatment.