Radiotherapy is the most common strategy for treating cancer. However, the radiation-induced inflammatory responses, acute or chronic, in the normal tissues of the irradiated region may result in undesirable side effects, such as lung injury and atherosclerosis. MALAT1 is believed to function in the onset, development, progression and metastasis of various cancers. Silencing MALAT1 may be a promising treatment for rescuing cancer. Nevertheless, whether MALAT1 promotes the radiation-induced undesirable inflammatory response is still uncovered. The present study reveals that radiation-induced DNA damage triggers cGAS signaling and subsequently increases the expression of MALAT1. Overexpression of MALAT1 inhibits the function of miR146a in the suppression of STAT1, which results in the boost of adhesion molecules and eventually induces acute lung injury and atherosclerosis. Thus, silencing MALAT1 may facilitate the reduction of radiation-induced acute and chronic complications in the radiotherapy of cancer. (C) 2020 Elsevier Inc. All rights reserved.