Nevertheless, other tumor populations with stem cell markers (CXCR4+CD49f− in B16 and CXCR4+CD49f+, c-Kit−CD133+Sca-1+, c-Kit+CD133−Sca-1+ in LLC) detected in vivo in spheroid-plug model cannot be simply linked with induction of these populations by in vitro 3D conditions, as they were either not detected or were differentially regulated by in vitro spheroid culture. The gene discussed is CXCR4; the disease is neoplasm.