For lung tumorigenesis, this proposal can be supported by a recent report where Sca-1-positive-BASCs were originally proposed as cell of origin for K-Ras (G12D) driven bronchioalveolar carcinoma [59], however, within the tumors, both Sca-1-positive as well as negative cells acquired cancer stem cells properties as demonstrated by their ability to initiate secondary tumors when implanted in recipient mice [60]. Here, KRAS is linked to lung adenocarcinoma in situ.