A previous study showed that ERK1/2 could be activated when the intracellular levels of reactive oxygen species (ROS) were elevated by circulatory treatment in TNBC MDA‐MB‐231 cells.[35] Therefore, we investigated whether ROS could be generated during a separate co‐culture of MDA‐MB‐231 with Raw264.7 by using a fluorescent dye of CM‐H2DCFDA (DCFDA) to stain the cancer cells. This evidence concerns the gene MAPK3 and cancer.