DLGAP1-AS2-Mediated Phosphatidic Acid Synthesis Activates YAP Signaling and Confers Chemoresistance in Squamous Cell Carcinoma

Squamous cell carcinomas (SCC) constitute a group of human malignancies that originate from the squamous epithelium. Most patients with SCC experience treatment failure and relapse and have a poor prognosis due to de novo and acquired resistance to first-line chemotherapeutic agents. To identify chemoresistance mechanisms and to explore novel targets for chemosensitization, we performed whole-transcriptome sequencing of paired resistant and parental SCC cells. We identified DLGAP1 antisense RNA 2 (D-AS2) as a crucial noncoding RNA that contributes to chemoresistance in SCC. Mechanistically, D-AS2 affected chromatin accessibility around the histone mark H3K27ac of FAM3 metabolism regulating signaling molecule D (FAM3D), reducing FAM3D mRNA transcription and extracellular protein secretion. FAM3D interacted with the Gai- coupled G protein-coupled receptors formyl peptide receptor 1 (FPR1) and FPR2 to suppress phospholipase D (PLD) activity, and reduced FAM3D increased PLD signaling. Moreover, activated PLD promoted phosphatidic acid (PA) production and subsequent nuclear translocation of yes-associated protein (YAP). Accordingly, in vivo administration of a D-AS2-targeting anti -sense oligonucleotide sensitized SCC to cisplatin treatment. In summary, this study shows that D-AS2/FAM3D-mediated PLD/PA lipid signaling is essential for SCC chemoresistance, suggesting D-AS2 can be targeted to sensitize SCC to cytotoxic chemotherapeutic agents. Significance: This study identifies D-AS2 as a targetable lipid -related long noncoding RNA that increases phospholipase D activity to promote YAP signaling, triggering chemoresistance in SCC.