Abstract
BackgroundCytokine-based cancer therapies have attracted a great deal of attention in recent years. Unfortunately, resistance to treatment limits the efficacy of these therapeutics. Therefore, the aim of our study was to explore the mechanism of IL-2-based therapy for hepatocellular carcinoma in an attempt to increase the efficiency of this treatment option.MethodsHepG2 cells were treated with IL-2. Then, siRNA against TZA was used to transfected into HepG2 cells. Cellular apoptosis was measured via MTT assay, TUNEL assay and caspase-3 activity. Cellular proliferation was evaluated via EdU assay and western blotting. Cellular migration was detected via Transwell assay. Mitochondrial function was monitored by mitochondrial potential analysis, ROS staining, immunofluorescence and western blotting. Pathway blocker and activator were used to establish the role of JNK/F-actin/mitochondrial fission signaling pathway in HepG2 cells stress response.ResultsOur study found that IL-2 treatment significantly reduced the viability, mobility and proliferation of HepG2 cells in vitro. We also demonstrated that IL-2 treatment was accompanied by an increase in the expression of transcriptional co-activator with PDZ-binding motif (TAZ). Interestingly, genetic ablation of TAZ in the presence of IL-2 further promoted apoptosis, inhibited mobility, and arrested proliferation in HepG2 cells. At the molecular level, IL-2 administration activated excessive mitochondrial fission via the JNK/F-actin pathway; these effects were further enhanced by TAZ deletion. Mechanistically, TAZ knockdown further increased the expression of mitochondrial fission-related proteins such as Drp1, Mff and Fis. The augmented mitochondrial fission stimulated ROS overproduction, mediated redox imbalance, interrupted mitochondrial energy generation, reduced mitochondrial membrane potential, promoted leakage of the pro-apoptotic molecule cyt-c into the nucleus, and initiated caspase-9-related mitochondrial death. Further, we demonstrated that the anti-proliferative and anti-metastatic effects of IL-2 in HepG2 cells were enhanced by TAZ deletion, suggesting that IL-2 sensitizes HepG2 cells to IL-2-based cytokine therapy. However, JNK/F-actin pathway blockade could abrogate the inhibitory effects of TAZ deletion on HepG2 migration, proliferation and survival.ConclusionsTaken together, our data indicate that the anti-tumor effects of IL-2-based therapies may be enhanced by TAZ deletion in a JNK/F-actin pathway-dependent manner. This finding provides a novel combinatorial therapeutic approach for treating hepatocellular carcinoma that might significantly increase the efficacy of cytokine-based therapies in a clinical setting.
Highlights
Cytokine-based cancer therapies have attracted a great deal of attention in recent years
Taken together, our data indicate that the anti-tumor effects of IL-2-based therapies may be enhanced by transcriptional co-activator with PDZ-binding motif (TAZ) deletion in a Jun N-terminal kinase (JNK)/F-actin pathway-dependent manner
These findings indicate that IL-2-induced mitochondrial apoptosis in HepG2 cell is attributable to activated mitochondrial fission, which is enhanced by TAZ deletion
Summary
Cytokine-based cancer therapies have attracted a great deal of attention in recent years. Cytokine-based cancer therapies have experienced increased attention in recent years and include TNFαmediated apoptosis of gastric cancer [1], IL-16-induced arrest of prostate cancer growth [2] and IFN-triggered inhibition of lung cancer metastasis [3]. IL-2, a pro-inflammatory cytokine, functions to suppress cancer progression by indirectly boosting the anti-tumor immune response in liver [6] and by directly promoting cancer cell death [7]. These results, obtained from basic research and/or clinical practice, indicate the clinical relevance of IL-2 in repressing cancer development and the necessity of developing IL-2-based therapies to control cancer survival and migration in the liver tissue. Elucidating the molecular mechanisms of IL-2-mediated anti-tumor effects in HepG2 cell is critical to increase the clinical efficiency of cytokinebased therapies
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