Similarly, cancer‐associated fibroblasts (CAFs), a class of non‐cancerous cells that interact with the tumor, engage in a two‐way cross‐talk with ROS such that ROS converts fibroblasts into its active counterpart (CAFs) by upregulating HIF1α, and simultaneously, CAFs are also pivotal in increasing ROS concentration in cancer cells. The gene discussed is HIF1A; the disease is neoplasm.