RSK Inhibition Rewires Kinase Networks and Triggers Cascading Pathway Disruption in Esophageal Cancer

RSK plays a central role in oncogenic signaling, yet
its broader
regulatory impact in esophageal squamous cell carcinoma (ESCC) remains
unclear. We performed integrated phosphoproteomics and kinase-substrate
network analysis to elucidate global signaling alterations following
RSK inhibition in ESCC cells. In Eca-109 cells, treatment with a moderate
concentration of the selective RSK inhibitor SL0101 effectively suppressed
proliferation without inducing apoptosis. To elucidate potential compensatory
survival mechanisms, we performed integrated proteomic and phosphoproteomic
analyses, which revealed that RSK inhibition provokes broad cellular
adaptations. Importantly, the magnitude of these effects varied across
pathways. Ribosome biogenesis and mitochondrial organization exhibited
substantial perturbation primarily at the proteomic level, reflecting
system-level dysregulation. Phosphoproteomic analysis revealed that
large-magnitude alterations in nuclear transport and mRNA processing,
and more subtle, fine-tuned modulation of mitotic fidelity. Kinase
activity inference further identified MAPK14, CDK2, SRPK3, AKT1, PLK1,
and PIM2 as principal regulators that may regulate compensatory signaling
in response to RSK suppression. Taken together, our study reveals
that RSK inhibition reprograms kinase networks to enforce stress adaptation,
maintaining oncogenic homeostasis despite perturbations. These findings
highlight a potential therapeutic window for early intervention strategies,
suggesting that combination strategies may enhance the efficacy of
RSK-directed therapies in ESCC.