In tumor biology, there is substantial evidence that cancer cells exploit vesicular trafficking and secretion to remodel the microenvironment: by releasing soluble cytokines (e.g., IL-6, IL-8, VEGF), growth factors (e.g., TGF-β, EGF), proteases (e.g., MMP2, MMP9), and extracellular vesicles (EVs) carrying integrins, tetraspanins (CD9, CD63, CD81, CD82), and various noncoding RNAs, tumor cells can promote proliferation, invasion, angiogenesis, immune evasion, and therapy resistance [38]. The gene discussed is CD9; the disease is cancer.