METTL1/USP48 Axis Stabilizes LCN2 Expression to Promote the Malignant Phenotypes of Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (cSCC) is a prevalent skin malignancy characterized by aggressive biological behaviors. Lipocalin 2 (LCN2) has been implicated in the progression of various cancers; however, the specific mechanisms by which LCN2 modulates malignant phenotypes of cSCC remain insufficiently understood. The expression levels of LCN2, ubiquitin specific peptidase 48 (USP48), and methyltransferase like 1 (METTL1) were analyzed in cSCC tissues, paracancerous tissues, and/or cell lines using western blotting and quantitative real-time PCR. Functional assays, including cell counting kit-8 (CCK-8), flow cytometry, wound healing, Transwell invasion, and colorimetric assays, were conducted to evaluate cell proliferation, apoptosis, migration, invasion, and ferroptosis indicators. The regulatory mechanisms were investigated via methylated RNA immunoprecipitation (MeRIP), dual-luciferase reporter, co-immunoprecipitation (Co-IP), and ubiquitination assays. Furthermore, in vivo tumorigenicity was assessed using a xenograft mouse model. LCN2 was significantly upregulated in cSCC tissues and cell lines. LCN2 expression was associated with clinical stage of cSCC patients. Knockdown of LCN2 suppressed cell proliferation, migration, and invasion, while promoting apoptosis and ferroptosis. Mechanistically, USP48 was found to interact with LCN2 and enhance its stability by removing K48-linked ubiquitin chains. Functionally, USP48 silencing inhibited the malignant behaviors of cSCC cells, whereas these effects were rescued by LCN2 overexpression. Upstream analysis revealed that METTL1 stabilized USP48 mRNA expression via m7G methylation modification. Knockdown of METTL1 inhibited the key malignant phenotypes of cSCC cells, however, these effects were effectively reversed by USP48 overexpression. Consistent with in vitro findings, USP48 silencing reduced tumor growth and LCN2 and Ki67 expression in vivo, but these inhibitory effects were attenuated by the restoration of LCN2. This study elucidated a novel oncogenic axis in cSCC, wherein METTL1 stabilized USP48 mRNA through m7G methylation modification, and USP48 in turn deubiquitinated and stabilized LCN2 protein. This axis promoted cSCC progression. Clinically, these findings identify the METTL1/USP48/LCN2 pathway as a potential therapeutic target for cSCC.