Selenium‐binding protein 1 inhibits malignant progression and induces apoptosis via distinct mechanisms in non‐small cell lung cancer

BACKGROUND: Selenium is an essential trace element in the human body. In epidemiological and clinical studies, Se supplementation significantly reduced the incidence of lung cancer in individuals with low baseline Se levels. The significant action of selenium is based on the selenium‐containing protein as a mediator. Of note, the previous studies reported that the expression of selenium‐binding protein 1 (SELENBP1) was obviously decreased in many human cancer tissues including non‐small cell lung cancer (NSCLC). However, its roles in the origin and development of NSCLC are still unclear. METHODS: The expression of SELENBP1 was measured by qRT‐PCR, Western blotting and IHC in our collected clinical NSCLC tissues and cell lines. Next, the CCK‐8, colony formation, wound‐haeling, Millicell, Transwell, FCM assay, and in vivo xenograft model were performed to explore the function of SELENBP1 in NSCLC. The molecular mechanisms of SELENBP1 were investigated by Western blotting or IF assay. RESULTS: We further identified that the expression of SELENBP1 was significantly decreased in NSCLC tissues in TCGA database and 45 out of 59 collected clinical NSCLC tissues compared with adjacent nontumor tissues, as well as in four NSCLC cell lines compared with normal lung cells. Particularly, we unexpectedly discovered that SELENBP1 was obviously expressed in alveolar type 2 (AT‐II) cells for the first time. Then, a series of in vitro experiments uncovered that overexpression of SELENBP1 inhibited the proliferation, migration, and invasion of NSCLC cells, and induced cell apoptosis. Moreover, overexpression of SELENBP1 also inhibited growth and induced apoptosis of NSCLC cells in vivo. Mechanistically, we demonstrated that overexpression of SELENBP1 inhibited the malignant characteristics of NSCLC cells in part via inactivating the PI3K/AKT/mTOR signal pathway. Meanwhile, we found that overexpression of SELENBP1 inducing the apoptosis of NSCLC cells was associated with the activation of caspase‐3 signaling pathway under nonhigh level of oxidative stress, but overexpression of SELENBP1 facilitating the cell apoptosis might be related to its combining with GPX1 and colocalizing in the nucleus under high level of oxidative stress. CONCLUSIONS: Our findings highlighted that SELENBP1 was an important tumor suppressor during the origin and development of NSCLC. It may help to discover novel biomarkers or drug therapy targets for NSCLC.