Annexin A1: a new biomarker for predicting nasopharyngeal carcinoma response to radiotherapy.

Radiotherapy is the primary treatment for nasopharyngeal carcinoma (NPC), but radioresistance remains a serious obstacle to successful treatment in many cases. Therefore, the biomarkers for predicting NPC response to radiotherapy are very important for targeted therapy and individualized radiotherapy of NPC. Accumulating evidences have shown that Annexin A1 was correlated with NPC radioresistance. First, Annexin A1 is a potential tumor suppressor gene, and can regulate tumor cell proliferation and apoptosis, thus abnormal expression of Annexin A1 in NPC affects apoptosis of tumor cells induced by ionizing radiation and radiotherapeutic efficacy. Second, Annexin A1 is one of the proteins that are involved in p53-mediated radioresponse in NPC, and it might be related to NPC radioresistance. Third, the expression level of Annexin A1 is down-regulated in NPC, and is correlated with metastasis, recurrence and poor prognosis of NPC, thus Annexin A1 downregulation may increase NPC radioresistance, leading to poor prognosis. Last but not the least, Annexin A1 is closely related with tumor chemoresistance, whereas radioresistance is similar to chemoresistance in many aspects, thus Annexin A1 may also be involved in NPC radioresistance. Based on the above mentions, we hypothesize that Annexin A1 is closely correlated with NPC radioresistance and is an important new biomarker for predicting NPC response to radiotherapy.

Targeted proteomic analysis of 14-3-3sigma in nasopharyngeal carcinoma.

14-3-3sigma is a potential tumor suppressor, and loss of 14-3-3sigma expression plays an important role in carcinogenesis and metastasis. To explore the possible mechanism of 14-3-3sigma in nasopharyngeal carcinoma (NPC) invasion and metastasis, targeted proteomic analysis was performed on 14-3-3sigma-associated proteins from NPC cells. As the results, 112 proteins associated with 14-3-3sigma were identified, and four 14-3-3sigma-interacted proteins: keratin 8, epidermal growth factor receptor (EGFR), small GTP-binding protein RAB7, and p53 were confirmed by coimmunoprecipitation and Western blot analysis. The 14-3-3sigma-associated proteins could be grouped into eight clusters based on their molecule functions. Protein-protein interaction (PPI) analysis indicated that 14-3-3sigma/EGFR/keratin 8 interactions may be involved in the invasion and metastasis of NPC. 14-3-3sigma/EGFR/keratin 8 could form complexes in NPC cells. 14-3-3sigma downregulation in NPC may lead to the overexpression of EGFR and keratin 8, which increases the invasion ability of NPC cells possibly by activating the downstream signal molecules and reorganizing cytoskeleton. The data suggest that the biological functions of 14-3-3sigma in NPC are diversified, and 14-3-3sigma could inhibit the in vitro invasive ability of NPC cells possibly through 14-3-3sigma/EGFR/keratin 8 interaction.

Proteomic analysis to identify cytokeratin 18 as a novel biomarker of nasopharyngeal carcinoma.

PURPOSE: In this study, we applied laser capture microdissection and a proteomic approach to identify novel nasopharyngeal carcinoma (NPC) biomarkers. METHODS: Proteins from pooled microdissected NPC and normal nasopharyngeal epithelial tissues (NNET) were separated by two-dimensional gel electrophoresis, and differential proteins were identified by mass spectrometry. Expression of the differential protein cytokeratin 18 in the above two tissues as well as 4 NPC cell lines was determined by Western blotting. Immunohistochemistry was also performed to detect the expression of cytokeratin 18 in 62 cases of primary NPC, 28 cases of NNET, and 20 cases of cervical lymph node metastases, and the correlation of its expression level with clinicopathologic features and clinical outcomes were evaluated. siRNA and in vitro cell invasion assay were used to check the correlation between the expression of cytokeratin 18 and invasive ability of NPC. RESULTS: Thirty-six differential proteins between the NPC and NNET were identified. The expression level of cytokeratin 18 in the two types of tissues was confirmed by Western blotting and related to differentiation degree and metastatic potential of the NPC cell lines. Significant cytokeratin 18 down-regulation was observed in NPC versus NNET (P = 0.000), whereas significant cytokeratin 18 up-regulation was observed in lymph node metastasis versus primary NPC (P = 0.001). In addition, cytokeratin 18 down-regulation was significantly correlated with poor histological differentiation (P = 0.000), whereas cytokeratin 18 up-regulation was significantly correlated with advanced clinical stage (P = 0.019), recurrence (P = 0.000), and regional lymph node metastasis (P = 0.001), and distant metastasis (P = 0.000). And down-regulated cytokeratin 18 expression by siRNA significantly decreased in vitro invasive ability of 5-8F cells. Furthermore, survival curves showed that patients with cytokeratin 18 up-regulation had a poor prognosis (P = 0.000). Univariate analysis (Cox's proportional hazards model) showed that WHO histologic type (P = 0.025), lymph node metastasis (P = 0.007), distant metastasis (P = 0.005), recurrence (P = 0.000), and cytokeratin 18 (P = 0.000) were significantly associated with the prognosis of NPC. Multivariate analysis confirmed that lymph node metastasis (P = 0.012), distant metastasis (P = 0.009), recurrence (P = 0.006), and cytokeratin 18 (P = 0.001) were independent prognostic indicators. CONCLUSIONS: The data suggest that cytokeratin 18 is a potential biomarker for the differentiation and prognosis of NPC, and its dysregulation might play an important role in the pathogenesis of NPC.

Inactivation of 14-3-3 sigma by promoter methylation correlates with metastasis in nasopharyngeal carcinoma.

14-3-3 sigma, the downstream target of p53, is a negative regulator of cell cycle G2-M phase checkpoint in response to DNA damage. Our previous comparative proteomics study showed that 14-3-3 sigma was downregulated or lost in nasopharyngeal carcinoma (NPC) tissue compared with non-cancerous nasopharyngeal epithelial tissue (NNET). In this study, we further investigated for the epigenetic mechanism of 14-3-3 sigma inactivation. Methylation-specific PCR showed 14-3-3 sigma promoter methylation in 100% of analyzed NPC cell lines (4/4) but not in immortalized human nasopharyngeal epithelial cell line NP69. Treatment of the four NPC cell lines with the methyltransferase inhibitor 5-aza-2'-dC resulted in the demethylation and upregulation of 14-3-3 sigma. In tissues, 14-3-3 sigma promoter methylation occurred at a higher frequency in NPC, 63/75 (84%), compared to adjacent NNET, 7/25 (28%), and fully methylated 14-3-3 sigma promoter was detected in NPC but not in any of adjacent NNET. RT-PCR, Western blotting, and immunohistochemistry showed that 14-3-3 sigma expression was downregulated or lost in NPC with methylation, and there was a negative correlation between the expression levels and methylation statuses of 14-3-3 sigma gene. In addition, the patients with methylated 14-3-3 sigma presented a higher frequency of lymph node and distant metastasis, and an advanced clinical stage, and overexpression of 14-3-3 sigma in NPC cell line 5-8F with high metastatic potential was able to inhibit its in vitro invasive ability. Our data are the first to show that 14-3-3 sigma is frequently inactivated by promoter methylation in NPC and this aberrant methylation correlates with lymph node and distant metastasis.

Increased expression of HSP27 linked to vincristine resistance in human gastric cancer cell line.

PURPOSE: To understand the mechanisms of multidrug resistance (MDR) in vincristine-resistant human gastric cancer cell line SGC7901/VCR. METHODS: Comparative proteomics involving two-dimensional gel electrophoresis (2-DE) and ESI-Q-TOF Mass Spectrometry (MS) was performed on total proteins extracts from vincristine-resistant SGC7901/VCR and its parental cell line SGC7901. Then the association of heat shock protein 27 (HSP27), one of the highly expressed proteins in SGC7901/VCR, with MDR was analyzed using antisense oligonucleotides (ASOs) inhibition. To further elucidate the biological functions executed by HSP27 in SGC7901/VCR, we investigated a comprehensive interactome map of HSP27 by coimmunoprecipitation (IP) coupled with MS. RESULTS: In this study, HSP27 was identified as a protein showing increased expression in SGC7901/VCR. The suppression of HSP27 expression by HSP27 ASOs could enhance vincristine and adriamycin chemosensitivity in SGC7901/VCR. Identified 25 HSP27-interacting proteins by IP coupled with MS could be classified into eight categories based on their functions: cytoskeleton organization, chaperones, metabolic enzymes, proteins relative to signal transduction, ribosomal proteins, DNA repair proteins, proteins involved in transcription and translation, and RNA processing, which correspond to the reported functions of HSP27 with MDR. CONCLUSION: These data clearly link HSP27 and multidrug resistance mechanisms in gastric cancer.

[Screening for differentially expressed proteins in nasopharyngeal carcinoma by laser capture microdissection and proteomic analysis].

OBJECTIVE: To search for the differentially expressed proteins of nasopharyngeal carcinoma (NPC),and provide scientific evidence for identifying molecular biomarkers for NPC. METHODS: Laser capture microdissection (LCM) was used to purify the target cells from NPC and normal nasopharyngeal epithelial tissues (NNET). Two-dimensional gel electrophoresis (2-DE) was used to separate the total proteins of microdissected NPC and NNET, PDQuest software was applied to analyze 2-DE images,and the differential proteins between the 2 types of tissues were identified by both MALDI-TOF-MS and ESI-Q-TOF-MS. Western blot and immunohistochemistry of tissue microarray were used to detect the expression of the differential protein SCCA1 in NPC and NNET. RESULTS: 2-DE patterns of microdissected NPC and NNEC were established,and 36 differential proteins in the NPC and NNEC were identified,20 of which only expressed or up-regulated in NPC and 16 only expressed or up-regulated in NNET. The differentially expressed level of SCCA1 in the NPC and NNET was confirmed by Western blot and immunohistochemistry of tissue microarray. CONCLUSION: Thirty-six differentially expressed proteins identified in this study may be associated with the carcinogenesis of NPC,and may be candidate molecular biomarkers for NPC.

Identificating cathepsin D as a biomarker for differentiation and prognosis of nasopharyngeal carcinoma by laser capture microdissection and proteomic analysis.

In this study, we applied laser capture microdissection and a proteomic approach to identify novel nasopharyngeal carcinoma (NPC) biomarkers. Proteins from pooled microdissected NPC and normal nasopharyngeal epithelial tissues (NNET) were separated by two-dimensional gel electrophoresis, and differential proteins were identified by mass spectrometry. Expression of the differential protein cathepsin D in the above two tissues as well as four NPC cell lines was determined by Western blotting. Next, siRNA was used to inhibit the expression of cathepsin D in highly metastatic NPC cell line 5-8F to examine whether it associates with NPC metastasis. Immunohistochemistry was also performed to detect the expression of cathepsin D in 72 cases of primary NPC, 28 cases of NNET, and 20 cases of cervical lymph node metastases, and the correlation of its expression level with clinicopathologic features and clinical outcomes were evaluated. Thirty-six differential proteins between the NPC and NNET were identified. The expression level of cathepsin D in the two types of tissues was confirmed by Western blotting and related to differentiation degree and metastatic potential of the NPC cell lines. Down-regulated cathepsin D expression by siRNA significantly decreased in vitro invasive ability of 5-8F cells. Significant cathepsin D down-regulation was observed in NPC versus NNET, whereas significant cathepsin D up-regulation was observed in lymph node metastasis versus primary NPC. In addition, cathepsin D down-regulation was significantly correlated with poor histological differentiation, whereas cathepsin D up-regulation was significantly correlated with advanced clinical stage, recurrence, and lymph node and distant metastasis. Furthermore, survival curves showed that patients with cathepsin D up-regulation had a poor prognosis. Multivariate analysis confirmed that cathepsin D expression was an independent prognostic indicator. The data suggest that cathepsin D is a potential biomarker for the differentiation and prognosis of NPC, and its dysregulation might play an important role in the pathogenesis of NPC.

Identification of novel nasopharyngeal carcinoma biomarkers by laser capture microdissection and proteomic analysis.

PURPOSE: To identify novel nasopharyngeal carcinoma (NPC) biomarkers by laser capture microdissection and a proteomic approach. EXPERIMENTAL DESIGN: Proteins from pooled microdissected NPC and normal nasopharyngeal epithelial tissues (NNET) were separated by two-dimensional gel electrophoresis, and differential proteins were identified by mass spectrometry. Expression of three differential proteins (stathmin, 14-3-3sigma, and annexin I) in the above two tissues as well as four NPC cell lines was determined by Western blotting. Immunohistochemistry was also done to detect the expression of three differential proteins in 98 cases of primary NPC, 30 cases of NNET, and 20 cases of cervical lymph node metastases, and the correlation of their expression levels with clinicopathologic features and clinical outcomes were evaluated. RESULTS: Thirty-six differential proteins between the NPC and NNET were identified. The expression levels of stathmin, 14-3-3sigma, and annexin I in the two types of tissues were confirmed and related to differentiation degree and/or metastatic potential of the NPC cell lines. Significant stathmin up-regulation and down-regulation of 14-3-3sigma and annexin I were observed in NPC versus NNET, and significant down-regulation of 14-3-3sigma and annexin I was also observed in lymph node metastasis versus primary NPC. In addition, stathmin up-regulation and down-regulation of 14-3-3sigma and annexin I were significantly correlated with poor histologic differentiation, advanced clinical stage, and recurrence, whereas down-regulation of 14-3-3sigma and annexin I was also significantly correlated with lymph node and distant metastasis. Furthermore, survival curves showed that patients with stathmin up-regulation and down-regulation of 14-3-3sigma and annexin I had a poor prognosis. Multivariate analysis revealed that the expression status of stathmin, 14-3-3sigma, and annexin I was an independent prognostic indicator. CONCLUSION: The data suggest that stathmin, 14-3-3sigma, and annexin I are potential biomarkers for the differentiation and prognosis of NPC, and their dysregulation might play an important role in the pathogenesis of NPC.