TMEM170B is a transmembrane protein that functions as a tumor suppressor through negative regulation of canonical Wnt/β-catenin signaling. In breast cancer cells, TMEM170B inhibits CTNNB1 (β-catenin) stabilization and nuclear translocation, reducing expression of Wnt target genes 1. TMEM170B is a direct target of oncogenic microRNAs including miR-27a in breast cancer 1, miR-18a-5p in cervical cancer 2, and miR-27a in hepatocellular carcinoma 3, indicating its role as a key regulatory node suppressed across multiple cancer types. Clinically, TMEM170B expression correlates with improved prognosis. In pancreatic adenocarcinoma, low TMEM170B expression is significantly associated with poor differentiation and independently predicts unfavorable overall and disease-free survival 4. High TMEM170B expression correlates with enhanced antitumor immune infiltration, including B cells, T cells, dendritic cells, and M1 macrophages, while reducing immunosuppressive cell populations 4. In cervical cancer, TMEM170B overexpression attenuates tumor-promoting effects of cancer-associated fibroblast-derived exosomes 2. These findings establish TMEM170B as a promising biomarker and potential therapeutic target for multiple malignancies.