TMEM101 (transmembrane protein 101) is a cell surface protein implicated in cancer progression and immune regulation. While annotated as potentially activating NF-κB signaling pathways, its primary characterized role involves regulating cell proliferation and migration. Functionally, TMEM101 promotes cell proliferation and migration in triple-negative breast cancer cells in vitro 1, suggesting oncogenic activity. In hepatocellular carcinoma, TMEM101 shows significantly elevated mRNA expression correlating with poor overall survival, higher histological grade, and advanced clinical stage, functioning as an independent prognostic factor 2. TMEM101 expression is regulated by DNA methylation, with reduced promoter methylation observed in HCC and promoter hypermethylation associated with decreased expression in ARID1A-deficient ovarian clear cell carcinoma 3. Gene expression profiling identifies TMEM101 as part of diagnostic signatures distinguishing ovarian cancer histological subtypes 4 and predicting recurrence risk in early-stage triple-negative breast cancer 1. Mechanistically, TMEM101's pro-tumor effects may involve modulating tumor microenvironment immunity by reducing anti-tumor M1 macrophages and CD4+ T cells while promoting M0 macrophage infiltration 2. These findings position TMEM101 as a potential therapeutic target and biomarker across multiple cancer types, particularly for prognosis and treatment response prediction.