Gastric cancer is the fifth most common cancer worldwide and Hippo-Yap is the novel signaling pathway which plays an important role in gastric cancer tumor development and progression. However, little insight is available to date regarding the specific role of Yes-associated protein (Yap) in gastric cancer. In the present study, we identified the mechanism through which Yap sustains gastric cancer viability and migration. Yap was greatly upregulated in gastric cancer cells and its expression promoted cellular migration and survival. Functional studies found that knockdown of Yap reduced the mitophagy activity, which subsequently caused mitochondrial apoptosis and cellular oxidative stress. The latter impaired adhesive protein expression, alleviated F-actin expression, blunted lamellipodium formation, leading to inhibition of cancer cell motility. Mechanistically, Yap preserved Sirtuin 1 (SIRT1) activity which manipulated mitofusin 2 (Mfn2) expression and subsequent mitophagy. Loss of Yap reduced SIRT1 expression and inhibited Mfn2-mediated mitophagy. Collectively, our results identified Hippo-Yap as a tumor promoter in gastric cancer that was mediated via activation of the SIRT1/Mfn2/mitophagy axis, with potential applications to gastric cancer therapy involving cancer survival and migration.

Tumor necrosis factor α (TNFα)-based immunotherapy is the vital host defense system against the progression of gastric cancer (GC) as a pro-inflammatory and pro-apoptotic cytokine. However, resistance limits its therapeutic efficiency. Therefore, an increasing number of studies are focusing on the development of drugs or methods with which to enhance the treatment efficacy of TNFα. Nuclear receptor subfamily 4 group A member 1 (NR4A1) has been shown to exert antitumor effects through several mechanisms, such as by inhibiting proliferation, as well as pro-apoptotic and potent pro-oxidant effects. In this study, we examined the effects and mechanisms of action of NR4A1 on the apoptosis of GC cells treated with TNFα, with particular focus on mitochondrial homeostasis. We found that TNFα treatment decreased NR4A1 expression. Moreover, the overexpression of NR4A1 in the presence of TNFα further increased GC cell apoptosis. Mechanistically, the overexpression of NR4A1 augmented caspase-9-dependent mitochondrial apoptosis, as evidenced by reduced mitochondrial membrane potential, reactive oxygen species (ROS) overproduction, mitochondrial permeability transition pore (mPTP) opening and the leakage of cytochrome c (Cyt-c) leakage. Moreover, NR4A1 overexpression also evoked mitochondrial energy disorder via the suppression of mitochondrial respiratory complex expression. Furthermore, we found that TNFα treatment activated Parkin-dependent mitophagy. Excessive Parkin-dependent mitophagy blocked mitochondrial apoptosis, undermining the toxic effects of TNFα on cells. However, NR4A1 overexpression suppressed Parkin-dependent mitophagy via the inhibition of c-Jun N-terminal kinase (JNK). Re-activation of the JNK/Parkin pathway abrogated the inhibitory effects of NR4A1 on mitophagy, eventually limiting cell apoptosis. Collectively, this study confirmed that NR4A1 sensitizes GC cells to TNFα-induced apoptosis through the inhibition of JNK/Parkin-dependent mitophagy.

ObjectiveTo study the relationship between TRIM14 expression and chemotherapy resistance of gastric cancer (GC) cells.MethodsThe expression of TRIM14 in 5‐fluorouracil (5‐FU)‐ and oxaliplation (L‐OHP)‐resistant GC tissues and cells were determined by qRT‐PCR and western blotting. PcDNA3.1‐TRIM14 and shRNA‐TRIM14 vector were transfected to 5‐FU‐resistant GC cells (SGC7901/5‐FU), and the proliferation and apoptosis of cells were measured. Animal experiments on 5‐FU‐resistant GC mice were performed to study the effect of TRIM14 expression on tumor size and weight, GC cell migration, and proliferation. pcDNA3.1‐MK‐3903 plasmid was transfected to SGC7901/5‐FU cells with TRIM14 silence. The cell proliferation and apoptosis were determined. The protein expressions of Trim14, LC3, and BECLIN1 were measured by western blotting.ResultsTRIM14 was significantly upregulated in 5‐FU‐ and L‐OHP‐resistant GC tissues and cells. The overexpression of TRIM14 promoted the proliferation and autophagy of SGC7901/5‐FU cells, and inhibited the apoptosis. Moreover, in vivo experiment verified that the silence of TRIM14 reduced the tumor size and weight, and inhibited the migration and proliferation of GC cells in 5‐FU‐resistant GC mice. The overexpression of MK‐3903 reversed the inhibiting role of TRIM14 knockout on the proliferation and autophagy of SGC7901/5‐FU cells.ConclusionTRIM14 promoted chemotherapy resistance of GC cells by regulating AMPK/mTOR pathway, and may be a new biomarker for treating GC.