Background Idiopathic pulmonary fibrosis (IPF) is a chronic and advanced interstitial lung disease with poor prognosis. AHNAK nucleoprotein 2 (AHNAK2) is a macromolecular protein that is important for cell migration and muscle membrane repair. The protein acts via epithelial–mesenchymal transition (EMT), which is a key mechanism in the pathogenesis of IPF. However, very few studies have elucidated the effect of AHNAK2 in the development of IPF. Therefore, we aimed to determine the role of AHNAK2 in IPF development. Methods C57BL/6 mice were induced with bleomycin, while A549 and Beas‐2b pulmonary epithelial cell lines were treated with TGF‐β1 to induce IPF model. The expression of AHNAK2 was detected using immunohistochemistry staining in vivo, and real‐time quantitative polymerase chain reaction (RT‐qPCR) and western blotting (WB) in vitro. C57BL/6 mice were injected with adeno‐associated virus (AAV)‐sh NC or AAV‐sh AHNAK2 and the pulmonary function and EMT marker expression were measured. The migratory abilities of the two transforming growth factor beta 1 (TGF‐β1)‐induced cell lines were examined using wound‐healing and Transwell assays after transfection with si‐NC, si‐AHNAK2‐1 and ‐2. EMT marker expression was detected using RT‐qPCR and WB. Smad3 and phosphorylated‐Smad3 of the two cells were examined using WB. Following Smad3 inhibition by Smad3 phosphorylation inhibitor (SIS3), TGF‐β1‐induced cell migration and EMT marker expression were evaluated again after different transfections. Results AHNAK2 expression was higher in the IPF model than in the normal model in vivo and in vitro. Partial inhibition of AHNAK2 suppressed the EMT process and improved pulmonary ventilation and compliance in the mouse model of IPF. Similarly, knockdown of AHNAK2 suppressed the migration of pulmonary epithelial cells and reversed EMT. Furthermore, Smad3 of the two TGF‐β1‐induced cell lines was not activated when AHNAK2 was inhibited. When SIS3 inhibited the activation of Smad3, the suppression of AHNAK2 had no effect on A549 and Beas‐2b, regardless of TGF‐β1 induction. Conclusions Inhibition of AHNAK2 alleviates pulmonary fibrosis and partially reverses EMT by inhibiting the TGF‐β1/Smad3 signaling pathway. Therefore, AHNAK2 is a potential therapeutic target for IPF.

Background Lung adenocarcinoma is one of the common causes of cancer‐related deaths worldwide. Histone cluster 1 H2A family member b (HIST1H2AB) is a member of the histone H2A family. Bioinformatic analyses have revealed that HIST1H2AB is highly expressed in some cancers and might be an oncogene. However, information on the function of HIST1H2AB in lung adenocarcinoma is limited. Methods The expression of HIST1H2AB was analyzed in normal lung, lung adenocarcinoma and paracancerous tissues from The Cancer Genome Atlas (TCGA) database and immunohistochemistry staining. It was further verified in the relative cell lines using real‐time quantitative polymerase chain reaction (RT‐qPCR). When the adenocarcinoma cells lines (A549 and H1299) were successfully transfected with shHIST1H2AB or an empty plasmid packaged into a lentivirus, cell proliferation was detected using Celigo fluorescence cell‐counting, colony formation and annexin V‐allophycocyanin assays. Twenty nude mice were subcutaneously injected with A549 cells transfected with shHIST1H2AB or empty plasmid; the tumor size was recorded on day 25 and then measured every 3 days thereafter. The final tumor weight was measured on day 37. Significantly differentially expressed genes were analyzed using a human gene expression array. Furthermore, the potentially relevant genes were verified using RT‐qPCR and western blotting. Results HIST1H2AB was highly expressed in lung adenocarcinoma tissues from TCGA database and immunohistochemistry staining. Similar results were seen in the lung adenocarcinoma cells. When the cells were successfully transfected with shHIST1H2AB or an empty plasmid, downregulation of HIST1H2AB inhibited the growth and promoted the apoptosis of lung adenocarcinoma cells. The xenograft results suggested that HIST1H2AB downregulation delayed tumor growth and reduced tumor weight. Moreover, interferon signaling pathway and four genes (HMGB1, FOXM1, F2RL1 and SLC4A7) might be regulated by HIST1H2AB in the development of lung adenocarcinoma as indicated through gene expression array, RT‐qPCR and western blotting analyses. Conclusions HIST1H2AB acts as an oncogenic protein and HIST1H2AB inhibition suppresses the proliferation of lung adenocarcinoma cells. It may be a novel target for lung adenocarcinoma therapy.