Proliferation of SAS in floating culture. SAS can proliferate in the anchorage-independent growth condition and form sphere. In this condition, activated receptors, including EGFR, assemble at lipid raft, which is a kind of platform of the plasma membrane. Not only lapatinib but also cetuximab and AG1478, inhibit the proliferation of SAS sphere. Moreover, LY294002, which is a PI3K inhibitor, and MK2206, which is an AKT inhibitor, suppress the amount of cyclin D2. Cyclin D2 is one of a regulator of cell cycle and contributes to the proliferation of SAS sphere.