Disrupting lipid homeostasis with CAV2 in OSCC triggers apoptosis, lipolysis, and mitochondrial dysfunction by transcriptional repression of PPARγ.

Abstract

Background: Abnormal lipid droplet (LD) dynamics in oral squamous cell carcinoma (OSCC) indicate lipid metabolism alterations that facilitate malignancy progression. However, the specific mechanisms by which disruptions in lipid homeostasis affect malignancy processes remain poorly understood. This study investigated the role of LD-associated protein Caveolin2 (CAV2) in OSCC lipid homeostasis and progression.

Methods: The clinical relevance of CAV2 in OSCC was assessed through transcriptomics, single-cell sequencing, and functional validation in OSCC cells. CAV2 knockdown via shRNA was used to analyze its effects on growth, apoptosis, lipid homeostasis, and mitochondrial function. RNA sequencing, lipidomics, and molecular docking elucidated mechanisms of lipid metabolic disruption. Lipolysis was evaluated via glycerol release, lipidomics, and expression of related genes and proteins. Seahorse assays were used to evaluate mitochondrial dysfunction by analyzing mitochondrial respiration, while additional experiments assessed ROS levels, MMP, morphology, mass, and organelle interactions. In vivo, studies examined tumor progression in nude mice implanted with CAV2-knockdown OSCC cells. The regulatory role of PPARγ on CAV2 was explored through bioinformatics, correlation analysis, and dual-luciferase assays. Coimmunoprecipitation assessed CAV2 and NCOR1 binding with PPARγ, while the PPARγ inverse agonist T0070907 was used to enhance NCOR1-mediated repression of CAV2.

Results: CAV2 was upregulated in OSCC and correlated with poor clinical outcomes. CAV2 knockdown increased apoptosis, reduced proliferation, and disrupted lipid homeostasis, elevating polyunsaturated fatty acids (PUFAs). Regulatory networks responsible for PUFA accumulation were mapped in CAV2-knockdown OSCC cells, from upstream regulators to downstream effects. Furthermore, lipolysis and mitochondrial dysfunction were also enhanced following CAV2 silencing. In vivo, CAV2 knockdown suppressed OSCC progression. Mechanistically, PPARγ regulated CAV2 transcription via NCOR1, but OSCC cells disrupted this repression. The PPARγ inverse agonist T0070907 restored NCOR1-mediated repression, synergistically enhancing the effects of CAV2 knockdown on apoptosis, lipolysis, and mitochondrial dysfunction.

Conclusions: Alteration of CAV2 disrupted lipid homeostasis and inhibited OSCC progression by affecting key processes, including apoptosis, lipolysis, and mitochondrial dysfunction. The disruption was driven by the dysregulation of the PPARγ/NCOR1 axis, highlighting the potential of targeting CAV2 and its interaction with PPARγ as a therapeutic strategy for OSCC.