Depletion of end-binding protein 1 (EB1) promotes apoptosis of human non-small-cell lung cancer cells via reactive oxygen species and Bax-mediated mitochondrial dysfunction

Abstract

Although end-binding protein 1 (EB1) is well known to regulate microtubule dynamics, the role of EB1 in apoptosis of non-small cell lung cancer (NSCLC) is poorly understood. Here, we investigated the molecular mechanism by which EB1 regulates apoptosis in H460, A549, and H1299 cells. Depletion of EB1 in A549 and H1299 cells, which express high levels of EB1, induced cell death in a p53-independent manner through over-production of reactive oxygen species (ROS) and Bax induction. This phenomenon was potentiated in radiation-treated EB1-knockdown cells and was largely blocked by N-acetyl-L-cysteine, a scavenger of ROS. ROS accelerated the activation of nuclear factor-kappa B (NF-κB) to promote transcriptional activity of Bax, an action that was accompanied by cytochrome c translocation and apoptosis-inducing factor (AIF) release. The NF-κB inhibitor, BAY 11-7082, potently inhibited the apoptosis induced by EB1 knockdown and radiation treatment, in association with diminished activity of the mitochondrial death pathway. Conversely, ectopic overexpression of EB1 in H460 cells, which express low levels of EB1, remarkably abrogated radiation-induced apoptosis and NF-κB-mediated mitochondrial dysfunction. Our data provide the first demonstration that down-regulation of EB1 promotes NSCLC cell death by inducing ROS-mediated, NF-κB-dependent Bax signaling cascades, a process in which cytochrome c and AIF play important roles, indicating a potential therapeutic benefit of EB1 in lung cancer.

Knockdown of end-binding protein 1 induces apoptosis in radioresistant A549 lung cancer cells via p38 kinase-dependent COX-2 upregulation

“…Cell death assay. Cell death was assessed as previously described (8). Apoptotic death was also determined by alterations in cellular morphology.…”

“…Conversely, COX-2 overexpression inhibited the cell cycle and tumor progression in osteosarcoma cells (12). Although our previous study revealed that EB1 knockdown promoted reactive oxygen species (ROS)-induced apoptosis in NSCLC cells via nuclear factor-κB (NF-κB) activation (8), the correlation between COX-2 and NSCLC cell death and the association between COX-2 regulation and EB1 remain unclear.…”

“…In addition, EB1 regulates the migration of B16F1 melanoma cells by modulating the balance between lamellipodia and filopodia protrusions (7). Previously, we reported that EB1 was a biomarker of radioresistance in non-small cell lung carcinoma (NSCLC) (8). Although several studies elucidating EB1 function have been performed using different human tumor tissues, the precise role of EB1 and its molecular mechanism of action related to cytotoxicity in cancer remains to be elucidated.…”

The +TIP coordinating protein EB1 is highly dynamic and diffusive on microtubules, sensitive to GTP analog, ionic strength, and EB1 concentration

“…Additionally, EB1 misregulation has been linked to cancer, possibly due to its interaction with the tumor suppressor APC (adenomatous polyposis coli) [Honnappa et al, ; Nishigaki et al, ; Liu et al, ; Dong et al, ]. Specifically, up‐regulation of EB1 has been observed as an early event of colorectal carcinogenesis [Stypula‐Cyrus et al, ], while depletion of EB1 promotes apoptosis of lung cancer cells [Kim et al, ].…”

Computational Studies on Different Types of Apoptotic Proteins Docked With a Dietary Flavonoid Eriodictyol in Colon Cancer

“…In mitochondria, cytochrome c causes the release of an apoptosis-inducing factor, activation of Bcl-2 -associated X protein (BAX), biological downregulation of B-cell lymphoma (Bcl)-2, and release of molecules involved in reactive oxygen species [9]. In addition, p53 consists of N-terminal activation domain, a basic DNA-binding domain with residues within 100-300, and C-terminal basic domain, residues 356-393 [10,11].…”