In accord with the cancer stem cell (CSC) theory, only a small subset of cancer cells are capable of forming tumors. We previously reported that CD44 isolates tumorigenic cells from head and neck squamous cell cancer (HNSCC). Recent studies indicate that aldehyde dehydrogenase (ALDH) activity may represent a more specific marker of CSCs.
Six primary HNSCCs were collected. Cells with high and low ALDH activity (ALDHhigh/ALDHlow) were isolated. ALDHhigh and ALDHlow populations were implanted into NOD/SCID mice and monitored for tumor development.
ALDHhigh cells represented a small percentage of the tumor cells (1% to 7.8%). ALDHhigh cells formed tumors from as few as 500 cells in 24/45 implantations, whereas only 3/37 implantations of ALDHlow cells formed tumors.
ALDHhigh cells comprise a subpopulation cells in HNSCCs that are tumorigenic and capable of producing tumors at very low numbers. This finding indicates that ALDH activity on its own is a highly selective marker for CSCs in HNSCC. © 2010 Wiley Periodicals, Inc. Head Neck, 2010