PROM1 and colonic neoplasm: PC Cluster 3 showed increased expression of Gif(gastric intrinsic factor), Cd81, a tetraspanin family member known to mark the response to γ-irradiation and correlated with the expression of ISC- and proliferation genes29, and Prom1 (prominin 1, also known as Cd133), a well-established colon cancer stem cell marker30.