Using p38MAPK knock-in mice and tumor xenografts, others have shown that MAPK-driven HAS2 expression and consequent HA production by fibroblasts is required for their activation into CAFs and for loss of their tumor suppressing properties resulting in a pro-tumor niche and increased lung colonization (Brichkina et al., 2016). The gene discussed is HAS2; the disease is neoplasm.