TGFB1 and radiation pneumonitis: Several lines of evidence have suggested that ATRA exerted protective action against radiation pneumonitis and BLM-induced lung injury in mice through anti-inflammatory effects by activating protein kinase C δ (PKC-δ), inhibiting mitogen-activated protein kinase P38 α (p38MAPK) and nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-kB), and suppressing the production of IL-6 and TGF-β [35–38].