Protein Methylation as a Regulatory Logic Layer in Cancer Signaling: Interplay with Phosphorylation and Network Plasticity

Phosphorylation has long been regarded as the principal mechanism governing oncogenic signal transduction. However, it does not fully account for the diversity, persistence, and context dependence of cancer signaling outputs. Protein methylation, historically studied in the context of histone regulation, is now recognized as a widespread modification of non-histone signaling proteins, including transcription factors, DNA damage response mediators, and scaffold components. In this Review, we propose that protein methylation functions as a regulatory logic layer that shapes how oncogenic signals are amplified, stabilized, and interpreted. Rather than serving as a primary trigger of pathway activation, methylation modulates signaling behavior across four interconnected dimensions: activation threshold and signal gain, temporal persistence, network topology and complex assembly, and spatial routing. We examine major signaling axes in which methylation refines genome integrity networks, proliferative pathways, inflammatory circuits, and lineage-specific transcriptional programs. We further discuss the interdependency between methylation and phosphorylation, highlighting sequential, competitive, and feedback-mediated interactions that expand combinatorial signaling states. Finally, we explore how methylation-mediated regulatory logic contributes to signaling plasticity and adaptive resistance under therapeutic pressure, and we outline key measurement and translational challenges. Framing protein methylation within a regulatory logic paradigm provides a structured approach for integrating this modification into contemporary models of oncogenic signaling and therapeutic intervention.