Pan-cancer analysis of role of LOXL4 and experiment validation in osteosarcoma.

Background: Osteosarcoma is an aggressive bone malignancy with high metastatic potential and poor prognosis, primarily affecting children and adolescents. Although lysyl oxidase-like 4 (LOXL4) has been implicated in tumor progression, its functional role and mechanistic contributions in Osteosarcoma remain unclear.

Methods: We performed integrated bioinformatics analysis using GTEx, TARGET, and TCGA datasets to evaluate LOXL4 expression and prognostic significance across cancers. Genetic alteration, immune infiltration, and RNA methylation analysis were carried to explore the different roles of LOXL4 in tumors. Functional assays, including Cell Counting Kit-8 (CCK-8), colony formation, and Matrigel transwell assays, were conducted in Osteosarcoma cell lines. Besides, western blotting and gene set enrichment analysis (GSEA) were used to explore LOXL4's mechanistic roles.

Results: LOXL4 was significantly upregulated in Osteosarcoma tissues and associated with poor patient survival. Pan-cancer analysis revealed LOXL4 is upregulated in multiple cancer types and exhibits tumor-type-specific genetic alteration patterns, most frequently mutated in melanoma and amplified in endometrial carcinoma. Besides, LOXL4 expression significantly correlated with immune infiltration levels, the expression of immune checkpoint molecules, and RNA methylation across multiple cancers. Functional experiments demonstrated that LOXL4 knockdown suppressed cell proliferation, invasion, and epithelial-mesenchymal transition (EMT), whereas LOXL4 overexpression enhanced these malignant phenotypes. Mechanistically, LOXL4 activated the Wnt/β-catenin signaling pathway. Inhibition of Wnt/β-catenin signaling with XAV-939 reversed LOXL4-induced oncogenic effects.

Conclusion: LOXL4 promotes Osteosarcoma progression via Wnt/β-catenin-mediated EMT and cell proliferation. Its pan-overexpression and associations with the tumor immune microenvironment underscore its potential as a therapeutic target. Targeting LOXL4 or its downstream pathway may offer novel therapeutic strategies for Osteosarcoma.