Identification of CD90 as a marker for lung cancer stem cells in A549 and H446 cell lines.

Accumulating evidence supports that cancer stem cells (CSCs) are responsible for tumor initiation, progression, distal metastasis and even drug resistance. Although CD90 has been identified as a marker for several types of stem cells, such as liver CSCs, the potential role of CD90 as a marker for lung CSCs has yet to be fully characterized. Our previous study demonstrated that the lung cancer stem-like cells isolated from A549 tumor spheres, which were cultured in serum-free conditioned medium, had stronger proliferation and self-renewal abilities, and expressed higher levels of the stem cell markers Sox2 and Oct4 as compared to A549 adherent cells. In the present study, we identified CD90 as a novel surface marker of CSCs in lung cancer cells. Furthermore, we isolated CD90+ CSCs from lung cancer cell lines A549 and H446. Our results revealed that the CD90+ cells, but not the CD90- cells, from lung cancer cells displayed higher tumorigenic capacity. These findings suggest that CD90 could be a potential marker of lung CSCs and thus provide new insight into further therapeutic strategies of lung cancer.