Hypoxia is one of the critical factors inducing HIF‐1α, which is frequently overexpressed in many cancers including colon cancer.17, 18, 19 Thus, in order to confirm whether the cellular density‐dependent induction of HIF‐1α was due to hypoxic cellular conditions, hypoxic areas were measured using the hypoxia probe. The gene discussed is HIF1A; the disease is cancer.