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ASCT2 (SLC1A5) is an EGFR-associated protein that can be co-targeted by cetuximab to sensitize cancer cells to ROS-induced apoptosis.
Lu, H, Li, X, Lu, Y, Qiu, S, Fan, Z
Cancer letters. 2016;(1):23-30
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Abstract
Therapeutic targeting of ASCT2, a glutamine transporter that plays a major role in glutamine uptake in cancer cells, is challenging because ASCT2 also has a biological role in normal tissues. In this study, we report our novel finding that ASCT2 is physically associated in a molecular complex with epidermal growth factor receptor (EGFR), which is often overexpressed in human head and neck squamous cell carcinoma (HNSCC). Furthermore, we found that ASCT2 can be co-targeted by cetuximab, an EGFR antibody approved for treating metastatic HNSCC. We demonstrated that cetuximab downregulated ASCT2 in an EGFR expression-dependent manner via cetuximab-mediated EGFR endocytosis. Downregulation of ASCT2 by cetuximab led to decreased intracellular uptake of glutamine and subsequently a decreased glutathione level. Cetuximab thereby sensitized HNSCC cells to reactive oxygen species (ROS)-induced apoptosis and, importantly, it is independent of effective inhibition of EGFR downstream signaling by cetuximab. In contrast, knockdown of EGFR by siRNA or inhibition of EGFR kinase with gefitinib, an EGFR kinase inhibitor, failed to sensitize HNSCC cells to ROS-induced apoptosis. Our findings support a novel therapeutic strategy for EGFR-overexpressing and cetuximab-resistant cancers by combining cetuximab with an oxidative therapy.
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Prognostic Value of VEGF in Hepatocellular Carcinoma Patients Treated with Sorafenib: A Meta-Analysis.
Cao, G, Li, X, Qin, C, Li, J
Medical science monitor : international medical journal of experimental and clinical research. 2015;:3144-51
Abstract
BACKGROUND Hepatocellular carcinoma (HCC) is characterized by rich vascularization in the tumor, and vascular endothelial growth factor (VEGF) plays important roles in vascularization. The results of the roles of VEGF in predicting efficacy of sorafenib in HCC are conflicting. In this meta-analysis, we aimed to investigate the prognostic and predictive value of VEGF in HCC patients receiving sorafenib. MATERIAL AND METHODS PubMed, Embase, and Cochrane library electronic databases were systematically searched for eligible studies. The baseline characteristics were recorded and overall qualities of the eligible studies were assessed by 2 reviewers independently. VEGF levels and data relevant to efficacy of sorafenib were extracted and used for meta-analysis. RESULTS The comprehensive search yielded 9 studies that evaluated the relationship between VEGF level and clinical outcome in advanced HCC patients treated with sorafenib. Pooled estimates suggested that high level of VEGF was associated with poor overall survival (HR=1.85; 95% CI: 1.24-2.77; P=0.003) and poor progression-free survival (HR=2.09; 95% CI: 1.43-3.05; P<0.01) in HCC. Mutation of VEGF had a favorable effect on hand-foot skin reaction in HCC patients treated with sorafenib (P<0.05). CONCLUSIONS High level of VEGF is associated with poor outcomes in HCC patients treated with sorafenib, indicating that VEGF could be used as an indicator of clinical efficacy in patients with HCC. However, more well-designed studies are needed to strengthen our findings.
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Oridonin up-regulates expression of P21 and induces autophagy and apoptosis in human prostate cancer cells.
Li, X, Li, X, Wang, J, Ye, Z, Li, JC
International journal of biological sciences. 2012;(6):901-12
Abstract
BACKGROUND Oridonin (ORI) could inhibit the proliferation and induce apoptosis in various cancer cell lines. However, the mechanism is not fully understood. METHODS Human prostate cancer (HPC) cells were cultured in vitro and cell viability was detected by the CCK-8 assay. The ultrastructure changes were observed under transmission electron microscope (TEM). Chemical staining with acridine orange (AO), MDC or DAPI was used to detect acidic vesicular organelles (AVOs) and alternation of DNA. Expression of LC3 and P21 was detected by Western Blot. Apoptotic rates and cell cycle arrest were detected by FACS. RESULTS Our study demonstrated that after ORI treatment, the proliferations of human prostate cancer (HPC) cell lines PC-3 and LNCaP were inhibited in a concentration and time-dependent manner. ORI induced cell cycle arrest at the G2/M phase. A large number of autophagosomes with double-membrane structure and acidic vesicular organelles (AVOs) were detected in the cytoplasm of HPC cells treated with ORI for 24 hours. ORI resulted in the conversion of LC3-I to LC3-II and recruitment of LC3-II to the autophagosomal membranes. Autophagy inhibitor 3-methyladenine (3-MA) reduced AVOs formation and inhibited LC3-I to LC3-II conversion. At 48 h, DNA fragmentation, chromatin condensation and disappearance of surface microvilli were detected in ORI-treated cells. ORI induced a significant increase in the number of apoptotic cells (PC-3: 5.4% to 27.0%, LNCaP: 5.3% to 31.0%). Promoting autophagy by nutrient starvation increased cell viability, while inhibition of autophagy by 3-MA promoted cell death. The expression of P21 was increased by ORI, which could be completely reversed by the inhibition of autophagy. CONCLUSIONS Our findings indicated that autophagy occurred before the onset of apoptosis and protected cancer cells in ORI-treated HPC cells. P21 was involved in ORI-induced autophagy and apoptosis. Our results provide an experimental basis for understand the anti-tumor mechanism of ORI as treatment for prostate cancer.