The FTO-regulated circNFATC3/miR-23b-3p axis promotes RAI14-mediated gastric cancer progression via lipid metabolic reprogramming

Aim To determine the mechanism by which fat mass and the obesity-associated protein (FTO)-regulated circNFATC3/miR-23b-3p axis influence RAI14-mediated gastric cancer (GC) progression. Methods Retinoic acid-induced protein 14 (RAI14), adenosine 5′-monophosphate-activated protein kinase (AMPK), mTOR (mTOR), sterol regulatory element-binding protein 1 (SREBP1), ATP citrate lyase (ACLY), fatty acid synthase (FASN), and miR-23b-3p expression was assessed via quantitative real-time polymerase chain reaction and/or western blotting. Cell viability, proliferative and migratory were determined via MTT, colony formation, and Transwell assays. Tumor growth was monitored in vivo via a xenograft model, and protein expression was evaluated viaimmunohistochemical staining. RNA immunoprecipitation (RIP) and methylated RNA immunoprecipitation (MeRIP) assays were performed to examine the direct interaction between FTO and circNFATC3 and to assess the m6A modification level of circNFATC3. N6-methyladenosine (m6A)-regulated genes targeted by circNFATC3 were predicted via the miRanda algorithm. Results RAI14 overexpression decreased miR-23b-3p and AMPK expression but increased mTOR, SREBP1, ACLY, and FASN expression in GC cells. AMPK, mTOR, and SREBP1 modulation affects GC cell growth and invasiveness. circNFATC3 overexpression facilitated tumor growth in vivo, accompanied by elevated RAI14, FTO, mTOR, SREBP1, ACLY, FASN, and Ki67 expression and decreased AMPK expression. circNFATC3 depletion inhibited tumor growth. RIP assays confirmed the direct binding of FTO protein to circNFATC3 RNA. MeRIP assays demonstrated that FTO overexpression/knowdown decreased/increased m6A modification on circNFATC3. FTO overexpression/depletion increased/decreased circNFATC3 expression and decreased/increased miR-23b-3p expression. FTO enhances GC cell proliferation and invasion by influencing circNFATC3 expression. Analysis of human GC tissues revealed lower AMPK expression than that in adjacent normal tissues. Conclusion Lipid synthesis and metabolic reprogramming play critical roles in energy metabolism, growth, and proliferation in GC. FTO directly binds to circNFATC3 and regulates the circNFATC3/miR-23b-3p/RAI14 axis during GC progression through an m6A-dependent mechanism.