FAM135A (Family with Sequence Similarity 135 Member A) is a gene located on chromosome 6 with roles in cancer progression and immune regulation. Primary function: FAM135A is implicated in perineural invasion in prostate cancer, where GRPR-induced FAM135A expression promotes tumor-nerve interaction through nuclear translocation mediated by RAN protein 1. The gene functions as a transcriptional regulator, with TENM3 identified as a direct transcriptional target 1. Mechanism: FAM135A exhibits nuclear enrichment and regulates downstream pathways involved in cancer cell invasion and neural interaction 1. In breast cancer, FAM135A acts as a miRNA target within the MIR17HG/miR-454-3p regulatory network, where high FAM135A expression correlates with better prognosis and reduced proliferation 2. Gene expression: FAM135A shows differential regulation across disease contexts—it is inhibited during CVB3 viral infection 3 and exhibits antagonistic expression patterns in rheumatoid arthritis and systemic lupus erythematosus 4. Disease relevance: Beyond prostate and breast cancers, FAM135A variants have been identified as candidate susceptibility loci for Alzheimer's disease in East Asian populations 5 and show mutations in pancreatic neuroendocrine tumors 6. Clinical significance: FAM135A serves as a potential biomarker and therapeutic target for prostate cancer perineural invasion and chemotherapy resistance in oral cancers 7, positioning it as a multi-disease relevant gene warranting further investigation.