GBP4 reflects TME dynamics, predicting immunotherapy responsiveness in melanoma and non-small cell lung cancer, with unmethylated forms in oral cancers serving as tumor-specific markers, detectable through methylation-specific PCR, next-generation sequencing, or epigenetic profiling, offering a niche diagnostic utility [62,63,74]. This evidence concerns the gene GBP4 and lip and oral cavity carcinoma.