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ABSTRACT: The present study was to examine the effect of sphingosine kinase-1 (SPHK1) on chemotherapeutics-induced apoptosis in non-small cell lung cancer (NSCLC) cells, which is relatively insensitive to chemotherapy, and its clinical significance in NSCLC progression.
The correlation of SPHK1 expression and clinical features of NSCLC was analyzed in 218 paraffin-embedded archived NSCLC specimens by immunohistochemical analysis. The effect of SPHK1 on apoptosis induced by chemotherapeutics was examined both in vitro and in vivo, using Annexin V staining and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) assays. Western blotting and luciferase analysis were performed to examine the impact of SPHK1 on the PI3K/Akt/NF-κB signaling.
The expression of SPHK1 was markedly increased in NSCLC and correlated with tumor progression and poor survival of patients with NSCLC. Upregulation of SPHK1 significantly inhibited doxorubicin- or docetaxel-induced apoptosis, associated with induction of antiapoptotic proteins Bcl-xl, c-IAP1, c-IAP2, and TRAF1. In contrast, silencing SPHK1 expression or inhibiting SPHK1 activity with specific inhibitor, SK1-I, significantly enhanced the sensitivity of NSCLC cells to apoptosis induced by chemotherapeutics both in vitro and in vivo. Moreover, we demonstrated that upregulation of SPHK1 activated the PI3K/Akt/NF-κB pathway, and that inhibition of the PI3K/Akt/NF-κB pathway abrogated the antiapoptotic effect of SPHK1 on NSCLC cells.
Our results suggest that SPHK1 is a potential pharmacologic target for the treatment of NSCLC and inhibition of SPHK1 expression or its kinase activity might represent a novel strategy to sensitize NSCLC to chemotherapy.
Clinical Cancer Research 02/2011; 17(7):1839-49. · 7.74 Impact Factor
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ABSTRACT: The biosynthesis and metabolism of RNA play important roles in regulating gene expression. On the other hand, it has been shown that RNA expression profiling is differentially distinct between cancer and normal cells, suggesting the possibility that aberrant regulation of RNA metabolism might be associated with the development and progression of cancer. In the current study, we found that Sam68, an RNA-binding protein that links cellular signalling to RNA processing, was markedly overexpressed in breast cancer cells and tissues. Immunohistochemical analysis showed that the expression and cytoplasmic localization of Sam68 significantly correlated with clinical characteristics of patients, including clinical stage, tumour-nodule-metastasis (TNM) classification, histological grade, and ER expression. Univariate and multivariate analyses showed that the expression level and cytoplasmic localization of Sam68 were identified as independent prognostic factors. Furthermore, we found that siRNA knockdown of endogenous Sam68 inhibited cell proliferation and tumourigenicity of breast cancer cells in vitro, through blocking the G1 to S phase transition. Moreover, we demonstrated that the anti-proliferative effect of silencing Sam68 on breast cancer cells was associated with up-regulation of cyclin-dependent kinase inhibitor p21(Cip1) and p27(Kip1), enhanced transactivation of FOXO factors, and attenuation of Akt/GSK-3β signalling. Taken together, our results suggest that Sam68 might play an important role in promoting the proliferation and carcinogenesis of human breast cancer, and thereby might be a novel and useful prognostic marker and a potential target for human breast cancer treatment.
The Journal of Pathology 11/2010; 222(3):227-37. · 6.32 Impact Factor
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ABSTRACT: Previously, we have identified a novel centrosomal protein centrobin that asymmetrically localizes to the daughter centriole. We found that depletion of centrobin expression inhibited the centriole duplication and impaired cytokinesis. However, the biological significance of centrobin in the cell cycle remains unknown. In the current study, we observed that silencing centrobin significantly inhibited the proliferation of lung cancer cell A549 and prevented the cells from G1 to S transition, whereas the growth rate of lung cancer cell line H1299, a p53-null cell line, was not affected. Furthermore, we demonstrated that the G1-S-phase arrest induced by centrobin knockdown in A549 cells is mediated by the upregulation of cell-cycle regulator p53, which is associated with the activation of cellular stress induced p38 pathway instead of DNA damage induced ATM pathway. Inhibition of p38 activity or downregulation of p38 expression could overcome the cell-cycle arrest caused by centrobin depletion. Taken together, our current findings demonstrated that centrobin plays an important role in the progression of cell cycle, and a tight association between the cell-cycle progression and defective centrosomes caused by depletion of centrobin.
Cellular signalling 05/2010; 22(5):857-64. · 4.09 Impact Factor
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ABSTRACT: Overexpression of sphingosine kinase-1 (SPHK1) has been demonstrated to be associated with the development and progression in various types of human cancers. The current study was to characterize the expression of SPHK1 in salivary gland carcinomas (SGC) and to investigate the association between SPHK1 expression and progression of SGC.
The expression of SPHK1 was examined in 2 normal salivary gland tissues, 8 SGC tissues of various clinical stages, and 5 pairs of primary SGC and adjacent salivary gland tissues from the same patient, using real-time PCR and western blot analysis. Furthermore, the SPHK1 protein expression was analyzed in 159 clinicopathologically characterized SGC cases by immunohistochemistry. Statistical analyses were performed to determine the prognostic and diagnostic associations.
SPHK1 expression was found to be markedly upregulated in SGC tissues than that in the normal salivary gland tissues and paired adjacent salivary gland tissues, at both mRNA and protein levels. Statistical analysis revealed a significant correlation of SPHK1 expression with the clinical stage (P = 0.005), T classification (P = 0.017), N classification (P = 0.009), M classification (P = 0.002), and pathological differentiation (P = 0.013). Patients with higher SPHK1 expression had shorter overall survival time, whereas patients with lower SPHK1 expression had better survival. Importantly, patients in the group without adjuvant therapy who exhibited high SPHK1 expression had significantly lower overall survival rates compared with those with low SPHK1 expression. Moreover, multivariate analysis suggested that SPHK1 expression might be an independent prognostic indicator for the survival of SGC patients.
Our results suggest that SPHK1 expression is associated with SGC progression, and might represent as a novel and valuable predictor for adjuvant therapy to SGC patients.
BMC Cancer 01/2010; 10:495. · 3.01 Impact Factor
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ABSTRACT: FOXO transcription factors are key tumor suppressors in mammalian cells. Until now, suppression of FOXOs in cancer cells was thought to be mainly due to activation of multiple onco-kinases by a phosphorylation-ubiquitylation-mediated cascade. Therefore, it was speculated that inhibition of FOXO proteins would naturally occur through a multiple step post-translational process. However, whether cancer cells may downregulate FOXO protein via an alternative regulatory mechanism is unclear. In the current study, we report that expression of miR-96 was markedly upregulated in breast cancer cells and breast cancer tissues compared with normal breast epithelial cells (NBEC) and normal breast tissues. Ectopic expression of miR-96 induced the proliferation and anchorage-independent growth of breast cancer cells, while inhibition of miR-96 reduced this effect. Furthermore, upregulation of miR-96 in breast cancer cells resulted in modulation of their entry into the G1/S transitional phase, which was caused by downregulation of cyclin-dependent kinase (CDK) inhibitors, p27(Kip1) and p21(Cip1), and upregulation of the cell-cycle regulator cyclin D1. Moreover, we demonstrated that miR-96 downregulated FOXO3a expression by directly targeting the FOXO3a 3'-untranslated region. Taken together, our results suggest that miR-96 may play an important role in promoting proliferation of human breast cancer cells and present a novel mechanism of miRNA-mediated direct suppression of FOXO3a expression in cancer cells.
PLoS ONE 01/2010; 5(12):e15797. · 4.09 Impact Factor
