We found expression of ABCG2 and Sca-1 to be upregulated in the SP cells isolated from D121 lung cancer cells when compared with that of non-SP derived from these same cancer cells as detected by flow cytometry (Figure 2A), by immunohistochemical fluorescence histology staining (Figure 2B) and RT–PCR (Figure 2C). The gene discussed is CASP3; the disease is lung cancer.