KRAS is not only able to impair the differentiation of endodermal progenitors in vitro when exposed to retinoic acid [31], but also promotes maintenance and expansion of TICs in breast cancer [12,32], keratinocytes [33], prostate cancer [16], colon cancer [34], pancreatic cancer [14] and lung cancer [15]. The gene discussed is KRAS; the disease is lung carcinoma.