Epithelial–mesenchymal transition in chemoradiation‐induced lung damage: Mechanisms and potential treatment approaches

Pulmonary injury is one of the key restricting factors for the therapy of malignancies with chemotherapy or following radiotherapy for chest cancers. The lung is a sensitive organ to some severely toxic antitumor drugs, consisting of bleomycin and alkylating agents. Furthermore, treatment with radiotherapy may drive acute and late adverse impacts on the lung. The major consequences of radiotherapy and chemotherapy in the lung are pneumonitis and fibrosis. Pneumonitis may arise some months to a few years behind cancer therapy. However, fibrosis is a long-term effect that appears years after chemo/or radiotherapy. Several mechanisms such as oxidative stress and severe immune reactions are implicated in the progression of pulmonary fibrosis. Epithelial-mesenchymal transition (EMT) is offered as a pivotal mechanism for lung fibrosis behind chemotherapy and radiotherapy. It seems that pulmonary fibrosis is the main consequence of EMT after chemo/radiotherapy. Several biological processes, consisting of the liberation of pro-inflammatory and pro-fibrosis molecules, oxidative stress, upregulation of nuclear factor of κB and Akt, epigenetic changes, and some others, may participate in EMT and pulmonary fibrosis behind cancer therapy. In this review, we aim to discuss how chemotherapy or radiotherapy may promote EMT and lung fibrosis. Furthermore, we review potential targets and effective agents to suppress EMT and lung fibrosis after cancer therapy.