Figure 6: Effect of WHSC1L1 knockdown on sensitivity of SCCHN cells to erlotinib.

(a) MTT assay of YD-10B cells treated with negative control siRNA versus WHSC1L1 specific siRNA for 48 h, and then exposed to erlotinib for 24 h (Student’s t-test, *p < 0.0001). All conditions are represented in quadruples. (b) 3D structural representation of the binding of erlotinib to the ATP-binding site of EGFR (modeled from Protein Data Bank, entry 4HJO). (c) Putative mechanism of action of WHSC1L1-mediated K721 mono-methylation of EGFR in the nucleus and cytoplasm of SCCHN cells.