PKCδ-Drp1 Axis Mediates VIP-Induced Mitochondrial Fragmentation and Metabolic Crisis in Nasopharyngeal Carcinoma

In nasopharyngeal carcinoma, mitochondria often function abnormally. However, the precise signals that cause excessive mitochondrial division are still undefined. Levels of the neuropeptide Vasoactive Intestinal Peptide are altered in NPC tissues. How VIP influences the metabolic behavior of cancer cells is not well established. Our experiments utilized established NPC cell lines. We tested how physiological concentrations (10-100 nM) of VIP exposure affect survival and mitochondrial integrity. Morphology was analyzed using fluorescence staining. We measured functional outputs, including reactive oxygen species, ATP levels, and membrane potential. Immunoblotting and activity assays helped trace the involved molecular events. Both genetic knockdown and a highly selective pharmacological inhibitor confirmed the proposed mechanism. To address pathway generality, experiments were repeated in an additional NPC line (NPC‑TW02). Receptor identity was probed using siRNA against VPAC1 and VPAC2. Selectivity for cancer cells was tested in normal nasopharyngeal epithelial NP69 cells. Administering VIP at 10-100 nM increased oxidative stress within mitochondria in a concentration-dependent manner. The transmembrane potential collapsed. Activity of the electron transport chain's Complex IV was suppressed, and cellular ATP content diminished. These failures led to pronounced mitochondrial fragmentation. VIP treatment (100 nM) rapidly activated the kinase PKCδ. PKCδ then phosphorylated the fission protein Drp1 at serine 616, causing Drp1 to accumulate at mitochondria. When we applied the compound Rottlerin to inhibit PKCδ, it effectively blocked Drp1 modification and recruitment. Consequently, mitochondrial fragmentation was prevented and energy metabolism recovered. These findings were confirmed in NPC‑TW02 cells. VPAC1 silencing, but not VPAC2 silencing, blocked VIP effects in C666-1 cells. Normal NP69 cells showed no significant response to VIP under the tested conditions. This work defines a previously unrecognized VIP-PKCδ-Drp1 pathway that operates at physiologically relevant VIP concentrations and controls mitochondrial division and fitness in NPC cells. This signaling axis highlights a specific metabolic weak point in these tumors. Our results suggest PKCδ could be investigated as a candidate target for therapies designed to correct mitochondrial dysfunction in nasopharyngeal carcinoma.