Causal identification and functional validation of TMEM45B as a risk gene in prostate cancer

Prostate cancer (PCa) is one of the most common malignancies affecting the male urogenital system and is characterized by significant molecular and clinical heterogeneity. Although previous studies have identified key molecules involved in PCa progression by employing high-throughput gene sequencing data, expression-based screening alone is inadequate for eliminating confounding factors or establishing causal relationships. This study proposed TMEM45B as a potential therapeutic target through the integration of multiple datasets, Mendelian randomization (MR)-based causal inference, and functional validation. Three independent PCa microarray datasets were screened and integrated. Background data correction, batch effect removal, and expression matrix normalization were accomplished using the limma package. In terms of causal association inference, Mendelian randomization analysis was performed. Immune infiltration characteristics and functional signaling pathways were analyzed using CIBERSORT and clusterProfiler, respectively. Finally, the cellular function of TMEM45B was systematically verified using WB, qPCR, cell scratch, colony formation, CCK-8, and Transwell assays. A nude mouse xenograft model was established to evaluate the effect of TMEM45B on tumor growth. This study identified 5 core driver genes with directionally consistent causal effects on PCa risk: TMEM45B, SPP1, GSTP1, BNIPL, and CYP27A1. Immune infiltration analysis indicated that these genes were linked with immune activation within the tumor microenvironment. Further experiments confirmed that silencing TMEM45B significantly inhibited PCa cell proliferation, migration, and invasion, while promoting apoptosis. In addition, in vivo xenograft experiments demonstrated that TMEM45B silencing significantly suppressed tumor growth. Our study highlights the important role of TMEM45B in the malignant progression of PCa by combining multicohort transcriptome integration and causal inference strategies. Functional assays revealed that targeting TMEM45B could significantly inhibit PCa cell proliferation, migration, and invasion; induce apoptosis; and suppress tumor growth. These findings provide important theoretical clues and evidence for enhancing the understanding of tumor–immune interactions and promoting the clinical translation of precise intervention strategies for PCa.