Blockade of CD47 signaling improves ferroptosis of lung cancer cells via activating Nrf2/FPN signaling.

CD47 plays an important role in immune evasion through suppressing macrophage phagocytosis. CD47 blockade has been widely explored in immunotherapy of cancers through enhancing macrophage phagocytosis. However, the role of CD47 in lung cancer cell apoptosis and ferroptosis is not well defined. In this study, we found that CD47 was highly expressed and ferroportin (FPN) was low expressed in lung cancer cells. Over-expression of CD47 increased the expression of Nrf2 (Nuclear factor erythroid 2-related factor 2); but suppressed the expression of FPN. Knock-down and blockade of CD47 expression and activity suppressed the expression of Nrf2 and enhanced the expression of FPN, subsequently improved lung cancer cell ferroptosis, accompanied with increased expression of pro-apoptotic protein Bax, production of reactive oxygen species (ROS) and hemosiderin deposition. Suppression of Nrf2 activity by Brusatol increased FPN expression at a concentration-dependent manner; whereas over-expression of FPN increased lung cancer cell ferroptosis. More studies in mouse model showed that knockdown of CD47 effectively attenuated lung cancer cell growth after subcutaneous inoculation of shCD47-pretreated LLC cells, associated with increased infiltration of neutrophils, CD8+ T cells and Malondialdehyde (MDA) products. Meanwhile, the expressions of TNF-α, IL-6 and IL-1β were elevated in the treated tumor tissues. IL-6 and TNF-α suppressed the expression of CD47, but increased the expression of FPN, accompanied with elevated expression of Bax, Cleaved caspase-3, NCOA4 (Nuclear receptor coactivator 4). Therefore, blockade of CD47 expression attenuated lung cancer growth through suppressing Nrf2 and subsequently increasing the expression of FPN. CD47 exerts immune evasion via Nrf2/FPN axis.