To confirm blocking RAC1/RAC3 activity increases cetuximab sensitivity with EHOP-016 is not an off-target (RAC1/RAC3 non-specific) pharmacological effect, we utilized short hairpin RNA (shRNA)-expressing lentivirus to knockdown RAC1 or RAC3 expression in HNSCC cells and detected whether cells’ sensitivity to cetuximab increased. This evidence concerns the gene RAC3 and head and neck squamous cell carcinoma.