To bypass these consistent difficulties, O’Brien and coworkers established an in vitro cell culture system is serum-free conditions using DMEM/F12 cell culture medium supplemented with EGF and bFGF: this cell culture system allowed the growth of tumor spheres that were more than 100 times enriched in colon cancer-initiating cells (CC-ICs) [434]. Here, EGF is linked to neoplasm.