Abstract
Wnt inhibitory factor‑1 (WIF‑1) is an important antagonist of Wnt/β‑catenin signaling by binding to Wnt ligands. The downregulation of WIF‑1 leads to the development of non‑small cell lung cancer (NSCLC). The upregulation of WIF‑1 significantly inhibits proliferation and induces apoptosis by inhibiting Wnt/β‑catenin signaling in NSCLC. However, the mechanisms underlying the inhibition of Wnt/β‑catenin signaling by WIF‑1‑mediated autophagy are poorly understood. Thus, in this study, we aimed to shed some light into these mechanisms. The upregulation of WIF‑1‑induced autophagy in NSCLC cells was detected by transmission electron microscopy, acridine orange staining, punctate GFP‑LC3 and immunoblotting‑based LC3 flux assay. Subsequently, WIF‑1‑mediated autophagy was blocked in NSCLC cells and the effects of WIF‑1‑mediated autophagy blocking were examined on the proliferation and apoptosis of NSCLC cells in vitro. Western blot analysis was used to investigate the molecular mechanisms effected by WIF‑1‑mediated autophagy in NSCLC cells. Finally, combination treatment with WIF‑1 and an autophagy agonist was used to examine the tumor growth inhibitory effects of WIF‑1 in vivo. The results revealed that the upregulation of WIF‑1 induced autophagy in NSCLC cells. WIF‑1‑mediated autophagy was demonstrated to inhibit Wnt/β‑catenin signaling by downregulating dishevelled‑2 (Dvl2), which contributed to the inhibition of the proliferation and the promotion of the apoptosis of NSCLC cells. Moreover, the induction of autophagy mediated by WIF‑1 was associated with to suppression of the activation of the phosphoinositide 3‑kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway. Finally, we found that transfection with a WIF‑1 gene overexpression vector in combination with treatment with the autophagy agonist, everolimus (RAD001) exerted synergistic antitumor effects on A549 subcutaneous tumor xenografts and pulmonary metastasis in mice. On the whole, the findings of this study demonstrated that WIF‑1‑mediated autophagy inhibits Wnt/β‑catenin signaling by downregulating Dvl2 expression in NSCLC cells. This may a novel molecular mechanism through which WIF‑1 inhibits Wnt/β‑catenin signaling. This study may provide a theoretical basis for joint therapy of NSCLC with WIF‑1 and autophagic agonists in clinical practice.