PROM1 and head and neck cancer: Consequently, CD133 has been considered as an important cell surface marker to represent the subpopulation of CICs in brain tumors, colon carcinoma, prostate carcinoma, hepatocellular carcinoma, thyroid carcinoma and head and neck cancer [8], [11], [12], [13], [14], [15], [16], [17], [18].