Figure 7. AXL mediates acquired resistance to cetuximab in HNSCC.

(A) Ctx^R cell clones (SP7, SP8, and SP11) and the Ctx^S parental cell line (SP) were treated with increasing doses of cetuximab (1 nM, 10 nM, and 100nM) for 72 hr prior to performing proliferation assays. Proliferation is plotted as a percentage of growth relative to vehicle treated cells (n=5 for 3 independent experiments). (B) Whole cell lysate was harvested from cells followed by immunoblotting for the indicated proteins. α-Tubulin was used as a loading control. Total AXL protein expression was quantitated using Image J software. (C) Cells were incubated with AXL siRNA (siAXL) or non-targeting (NT) siRNA for 72 hr prior to performing proliferation assays or isolation of whole cell lysate and immunoblotting for indicated proteins. α-Tubulin was used as a loading control. Proliferation is plotted as a percentage of growth relative to NT transfected cells (n=3 for 3 independent experiments). Data points are represented as mean± SEM. *p<0.05, **p<0.01.