ABCG2 and small cell lung carcinoma: To identify the most invasive SCLC phenotypes, we screened six human SCLC cell lines (H1688, H1417, H69AR derived from primary tumor site in lung, H250 from metastases to brain, and H211, H1882 from metastases to bone marrow) with a panel of antibodies for surface determinants of tumor cells, including uPAR, CD13, CD29, CD44, CXCR4, CD105, CD109, CD166, and for stem cell markers CD34, CD90, CD133, ABCG2/BCRP1.