To investigate further the contribution of innate immune responses [21] to the anti-cancer efficacy of ingenol mebutate treatment, B16 cells were grown subcutaneously to 10–20 mm2 in MyD88-/- and C57BL/6 mice and were then treated twice (day 0 and day 1) with ingenol mebutate or placebo gel, and tumour growth monitored over time. The gene discussed is MYD88; the disease is cancer.