This study was conducted to understand the role of RARβ in CSCs maintenance by using lentivirusmediated shRNA for RARβ to knock down RARβ mRNA levels in A549 putative CSCs (A549 CD166+CD44+ and A549 CD166+EpCAM+) and A549 putative non- CSCs (A549 CD166-CD44- and A549 CD166-EpCAM-).