rsRNA-28S-21 promotes endometrial cancer by regulating ferroptosis through the NSUN5-FTH1/FTL pathway

rRNA-derived small RNAs (rsRNAs), processed from ribosomal RNA, represent a novel subclass of small non-coding RNAs. Studies have demonstrated their involvement in cancer progression; however, their role in endometrial carcinoma remains unclear. In this study, RIP-seq was performed to analyze NSUN5-bound rsRNAs in EC cells, and qRT-PCR was used to quantify rsRNA-28S-21 expression. Functional assays were conducted to evaluate oncogenic characteristics. Mechanistic investigations included RNA-protein interactions (RNA pull-down, FISH, and RIP), m5C modification detection (dot blot and MeRIP), iron metabolism analysis (Fe2⁺ levels, ROS production, and lipid peroxidation detection), and protein profiling (immunofluorescence and Western blot). RIP-seq analysis showed that NSUN5 binds to rsRNA-28S-21 in EC, which was confirmed by RNA pull-down, FISH, and RIP assays. qRT-PCR results showed that rsRNA-28S-21 is highly expressed in endometrial carcinoma tissues. Cell functional assays revealed that knockdown of rsRNA-28S-21 suppresses EC cell proliferation, migration, and invasion while inducing apoptosis. Mechanistically, rsRNA-28S-21 binds to NSUN5 to regulate its expression and affects the level of m5C modification in endometrial cancer cells. This increases the 5-methylcytosine level of FTH1/FTL mRNA, reduces the intracellular iron concentration, upregulates glutathione peroxidase 4 (GPX4), and downregulates ROS and lipid peroxidation products, ultimately inhibiting ferroptosis and promoting endometrial cancer cell growth.