ABSTRACT
Human single-strand (ss) DNA binding proteins 1 (hSSB1) has been shown to participate in DNA damage response and maintenance of genome stability by regulating the initiation of ATM-dependent signaling. ATM phosphorylates hSSB1 and prevents hSSB1 from ubiquitin-proteasome-mediated degradation. However, the E3 ligase that targets hSSB1 for destruction is still unknown. Here, we report that hSSB1 is the bona fide substrate for an Fbxl5-containing SCF (Skp1-Cul1-F box) E3 ligase. Fbxl5 interacts with and targets hSSB1 for ubiquitination and degradation, which could be prevented by ATM-mediated hSSB1 T117 phosphorylation. Furthermore, cells overexpression of Fbxl5 abrogated the cellular response to DSBs, including activation of ATM and phosphorylation of ATM targets and exhibited increased radiosensitivity, chemosensitivity and defective checkpoint activation after genotoxic stress stimuli. Moreover, the protein levels of hSSB1 and Fbxl5 showed an inverse correlation in lung cancer cells lines and clinical lung cancer samples. Therefore, Fbxl5 may negatively modulate hSSB1 to regulate DNA damage response, implicating Fbxl5 as a novel, promising therapeutic target for lung cancers.
Subject(s)
DNA Damage , DNA-Binding Proteins/metabolism , F-Box Proteins/metabolism , Mitochondrial Proteins/metabolism , Ubiquitin-Protein Ligases/metabolism , Animals , Ataxia Telangiectasia Mutated Proteins/metabolism , Cell Line, Tumor , Cullin Proteins/metabolism , F-Box Proteins/physiology , Humans , Lung Neoplasms/enzymology , Lung Neoplasms/metabolism , Male , Mice, Nude , Phosphorylation , Proteolysis , Ubiquitin-Protein Ligase Complexes , Ubiquitin-Protein Ligases/physiology , UbiquitinationABSTRACT
The large tumour suppressor 1 (LATS1) signalling network has been proved to be an essential regulator within the cell, participating in multiple cellular phenotypes. However, it is unclear concerning the clinical significance of LATS1 and the regulatory mechanisms of 17-Allylamino-17- demethoxygeldanamycin (17-AAG) in lung adenocarcinoma (LAC). The aim of the present study was to investigate the correlation of LATS1 and yes-associated protein (YAP) expression with clinicopathological characteristics in LAC patients, and the effects of 17-AAG on biological behaviours of LAC cells. Subcutaneous LAC tumour models were further established to observe the tumour growth in nude mice. The results showed that the positive expression of LATS1 was significantly lowered (26.7% versus 68.0%, P < 0.001), while that of YAP was elevated (76.0% versus 56.0%, P = 0.03) in LAC tissues compared to the adjacent non-cancerous tissues; LAST1 expression was negatively correlated with YAP expression (r = 0.432, P < 0.001) and lymphatic invasion of the tumour (P = 0.015). In addition, 17-AAG inhibited proliferation and invasion, and induced cell apoptosis and cycle arrest in LAC cells together with increased expression of E-cadherin and p-LATS1, and decreased expression of YAP and connective tissue growth factor. Tumour volumes and weight were much smaller in 17-AAG-treated groups than those in untreated group (P < 0.01). Taken together, our findings indicate that decreased expression of LATS1 is associated with lymphatic invasion of LAC, and 17-AAG suppresses growth and invasion of LAC cells via regulation of the LATS1/YAP pathway in vitro and in vivo, suggesting that we may provide a promising therapeutic strategy for the treatment of human LAC.
Subject(s)
Adaptor Proteins, Signal Transducing/metabolism , Adenocarcinoma/drug therapy , Apoptosis/drug effects , Benzoquinones/pharmacology , Lactams, Macrocyclic/pharmacology , Lung Neoplasms/drug therapy , Phosphoproteins/metabolism , Protein Serine-Threonine Kinases/metabolism , Adaptor Proteins, Signal Transducing/biosynthesis , Adenocarcinoma of Lung , Animals , Antineoplastic Agents/pharmacology , Cadherins/biosynthesis , Cell Cycle Checkpoints/drug effects , Cell Line, Tumor , Cell Proliferation/drug effects , Connective Tissue Growth Factor/biosynthesis , Female , Gene Expression Regulation, Neoplastic , HSP90 Heat-Shock Proteins/antagonists & inhibitors , Humans , Male , Mice , Mice, Inbred BALB C , Mice, Nude , Middle Aged , Neoplasm Invasiveness/pathology , Phosphoproteins/biosynthesis , Protein Serine-Threonine Kinases/biosynthesis , Signal Transduction/drug effects , Transcription Factors , Xenograft Model Antitumor Assays , YAP-Signaling ProteinsABSTRACT
OBJECTIVE: To compare the curative effect, safety and survival of Nedaplatin combined with docetaxel and docetaxel alone as a second line treatment for advanced NSCLC. METHODS: From Sep 2005 to Mar 2009, fifty-eight patients with NSCLC treated in the Shanghai Chest Hospital who failed first-line chemotherapy and receiving docetaxel or docetaxel combined with nedaplatin were retrospectively analyzed. Survival analysis was evaluated by Kaplan-Meier and Log-Rank test. There were 20 patients in the combination group, and 38 in the single-agent group. RESULTS: The PFS was 4.35 months for combination group and 4.0 months for single-agent group, there was a significant difference between the two groups (P < 0.05). The mean survival time and 1-year survival rate were 13.5 months vs. 10.6 months and 29.0% vs. 22.0%, respectively, with no significant difference. The Hematological toxicity in the combination group was higher than that in the single-agent group, 15.0% vs. 10.5% (P = 0.003), and no renal toxicity was noted in this study. CONCLUSIONS: Compared with the treatment with docetaxel alone, Nedaplatin combined with docetaxel as a second line treatment for NSCLC has a better curative effect and acceptable toxicity.