O6‐methylguanine DNA methyltransferase repairs platinum‐DNA adducts following cisplatin treatment and predicts prognoses of nasopharyngeal carcinoma

Cisplatin (CDDP) is an important anti‐cancer drug commonly used in various human cancers, including nasopharyngeal carcinoma (NPC). How to overcome the drug resistance of CDDP provides opportunities to improve clinical outcomes of NPC. O⁶‐methylguanine–DNA methyltransferase (MGMT) has been well‐characterized to be a therapeutic determinant of O⁶‐alkylguanine alkylating drugs. However, the underlying mechanism and clinical relevance between MGMT and CDDP remain poorly defined in NPC. In this study, we showed that MGMT‐proficient cells were highly resistant to the cytotoxic effects of CDDP as compared to MGMT‐deficient cells. Further studies showed that the platinum level of DNA after CDDP exposure was significantly lower in MGMT‐proficient cells than in MGMT‐deficient cells. Host cell reactivation assay revealed that MGMT protected NPC cells from CDDP‐induced DNA damage by enhancing DNA repair capacity. Importantly, we demonstrated for the first time that MGMT protein directly bound to CDDP‐induced DNA damages. Subsequently, CDDP‐bound MGMT protein became ubiquitinated and was degraded through ubiquitin‐mediated proteasome system. We further analyzed the relationship between MGMT expression and clinical survivals in a cohort of 83 NPC patients. NPC patients who received CDDP‐based concurrent chemoradiotherapy (CCRT), with high MGMT expression level, exhibited shorter progression‐free survival (PFS; p = 0.022) and overall survival (OS; p = 0.015), than patients with low MGMT expression level. Furthermore, high MGMT expression level remained to be an independent prognostic factor for worse PFS (p = 0.01, hazard ratio 2.23) and OS (p = 0.018, hazard ratio 2.14). Our findings suggest that MGMT protein is important to determine the efficacy of CDDP in NPC.     

Increased expression of SHP-1 is associated with local recurrence after radiotherapy in patients with nasopharyngeal carcinoma

Background

Nasopharyngeal carcinoma (NPC) is a major cancer in southern China. Src homology phosphatase-1 (SHP-1) is a tyrosine phosphatase that regulates growth, differentiation, cell cycle progression, and oncogenesis. We determined the clinical significance of SHP-1 expression in the tumours of NPC patients from southern China who were treated with radiotherapy.

Patients and methods.

SHP-1 expression was determined by real-time polymerase chain reaction (PCR) and western blotting of NPC tissue samples of 50 patients and nasopharyngeal tissues of 50 non-NPC patients who had chronic nasopharyngeal inflammation. SHP-1 expression was measured in NPC tissue samples of 206 patients by immunohistochemistry and survival analysis was performed.

Results

The tumours of NPC patients had significantly increased expression of SHP-1 at mRNA and protein levels relative to patients with chronic nasopharyngeal inflammation. Survival analysis of NPC patients indicated that SHP-1 expression was significantly associated with poor local recurrence-free survival (p = 0.008), but not with nodal recurrence-free survival, distant metastasis-free survival, or overall survival.

Conclusions

SHP-1 appears to be associated with radiation resistance of NPC cells and can be considered as a candidate marker for prognosis and/or therapeutic target in patients with this type of cancer.     

Upregulation of caveolin‐1 and CD147 expression in nasopharyngeal carcinoma enhanced tumor cell migration and correlated with poor prognosis of the patients

Expression of caveolin‐1 (Cav‐1) and extracellular matrix metalloproteinase inducer (EMMPRIN/CD147) and their prognostic significance were analyzed in archive NPC samples. Cav‐1 and CD147 were overexpressed in 49.48% (96/194) and 59.39% (117/197) of NPC, respectively. Both Cav‐1 and CD147 expression levels correlated significantly with metastasis (p = 0.025 and 0.017, respectively) and a lower 5‐year survival rate (p = 0.02 and 0.0009, respectively). In addition, Cav‐1 expression levels correlated significantly with local recurrence (p = 0.038). Multivariate Cox regression analysis indicated that combination of high Cav‐1 and CD147 expression was a significant, independent prognosis predictor in patients with NPC (HR = 2.135; p = 0.006). Functional studies revealed that overexpression of Cav‐1 promoted secretion of MMP‐3 and MMP‐11 (active) proteins, as well as an increase in the migratory ability of CNE1 and CNE2 cells, while siRNA‐mediated silencing of Cav‐1 or CD147 led to reduced levels of MMP‐3 and MMP‐11(active) secretion, and reduced migration capacity of CNE1 and CNE2 cells. We observed a positive correlation between Cav‐1 and CD147 expression in NPC (ρ = 0.330, p = 0.000), CD147 protein levels were upregulated in Cav‐1 overexpressing CNE1 and CNE2 cells, whereas siRNA‐mediated silencing of Cav‐1 led to the downregulation of CD147 expression. Our results indicate that Cav‐1 and CD147 overexpression predict poor NPC prognosis and enhanced tumor cell migration, which is associated with MMP‐3 and MMP‐11 (active) secretion. © 2009 UICC     

STAT3 activation contributes directly to Epstein‐Barr virus–mediated invasiveness of nasopharyngeal cancer cells in vitro

Nasopharyngeal cancer (NPC) is an Epstein‐Barr virus (EBV)‐associated head and neck cancer prevalent in Asia. Although with reasons not fully understood, the intrinsic invasiveness of NPC is believed to be EBV‐linked. Recently, EBV was found to induce STAT3 activation. Constitutive STAT3 activation correlated with advanced clinical staging in NPC. We hypothesized that STAT3 activation by EBV directly contributes to the intrinsic invasiveness of NPC cells. Phospho‐STAT3‐Tyr705 was detected in high percentage of NPC tumors (7/10 cases). Using a paired NPC cell line model, HONE‐1 and the EBV‐infected counterpart, HONE‐1‐EBV, we found that HONE‐1‐EBV expressed a higher level of phospho‐STAT3‐Tyr705 and was ～11‐fold more invasive than HONE‐1. In HONE‐1‐EBV, STAT3 siRNA targeting inhibited both spontaneous and serum‐induced invasion, as well as cell growth. Conversely, activation of STAT3 (by expressing an activated STAT3 mutant, namely STAT3C) in the parental HONE‐1, mimicking EBV‐induced STAT3 activation, significantly enhanced its invasiveness and proliferation, which was accompanied by increased expression of markers of mesenchymal status, proliferation and anti‐apoptosis. Our results demonstrated that EBV‐induced STAT3 activation is responsible for NPC cell proliferation and invasion. This was further confirmed by a small molecule inhibitor of JAK/STAT3, JSI‐124. JSI‐124 inhibited STAT3 activation in HONE‐1‐EBV, with subsequent growth inhibition, induction of PARP cleavage, abrogation of anchorage‐independent growth and invasion. We found that EBV‐independent activation of STAT3 by a growth factor, EGF, also contributed to NPC invasion. In conclusion, EBV‐induced STAT3 activation directly contributes to the intrinsic invasiveness of NPC cells and STAT3 targeting may be beneficial in treating aggressive NPC. © 2009 UICC     

Down‐modulation of keratin 8 phosphorylation levels by PRL‐3 contributes to colorectal carcinoma progression

Phosphatase of regenerating liver‐3 (PRL‐3) is a member of the PRL protein tyrosine phosphatase family and has been proposed to promote the invasiveness and metastastic capability of colorectal cancers (CRCs); however, the underlying mechanisms and target molecules of PRL‐3 protein remain unknown. On the basis of the biological significance of PRL‐3 phosphatase activity confirmed by the catalytically inactive PRL‐3 mutant (C104S) and a PRL‐3 inhibitor in CRC‐derived SW480 cells, we performed protein expression profiling to search for PRL‐3‐mediated effector proteins. By a comparative study of phosphorylated proteins that differentially expressed in wild type and C104S mutant PRL‐3‐transfected SW480 cells; the cytoskeletal intermediate filament keratin 8 (KRT8) was identified as a physiological PRL‐3‐interacting protein. Indeed, treatment with the PRL‐3 inhibitor effectively suppressed the phosphorylation of KRT8 at S73 and S431. Moreover, we detected the physiological interaction between PRL‐3 and KRT8 and their colocalization at cellular lamellipodias and ruffles in vivo. In CRC tissue samples, tumor cells with high PRL‐3 expression showed reduction or loss of phosphorylated KRT8 expression, particularly at the invasive front and in the liver metastases. In conclusion, our results indicate that PRL‐3 may play an important role for the promotion of CRC cell migration and metastatic potential through direct KRT8 dephosphorylation. © 2008 Wiley‐Liss, Inc.     

Prognostic significance of tumor‐infiltrating lymphocytes in nondisseminated nasopharyngeal carcinoma: A large‐scale cohort study

The American Joint Committee on Cancer (AJCC) staging system is inadequate for an accurate prognosis in nasopharyngeal carcinoma (NPC). Thus, new biomarkers are under intense investigation. Here, we investigated whether the density of TILs could predict prognosis in NPC. First, we used 1490 cases of nasopharyngeal carcinoma samples from two independent cohorts to evaluate the density and distribution of tumor‐infiltrating lymphocytes (TILs). Second, in one cohort, we assessed associations between TILs and clinical outcomes in 593 randomly selected samples (defined as the training set) and validated findings in the remaining 593 samples (defined as the validation set). Furthermore, we confirmed the prognostic value of TILs in a second independent cohort of 304 cases (defined as the independent set). Based on multivariable Cox regression analysis, we also established an effective prognostic nomogram including TILs to improve accuracy in predicting disease‐free survival (DFS) for patients with nondisseminated NPC. We found that high TILs in the training set were significantly associated with favorable DFS [hazard ratio (HR) 0.41, 95% confidence interval (CI) 0.28–0.58, p < 0.001], overall survival (OS, HR 0.42, 95% CI 0.27–0.64, p < 0.001), distant metastasis‐free survival (DMFS, HR 0.37, 95% CI 0.23–0.58, p < 0.001) and local‐regional recurrent free survival (LRRFS, HR 0.43, 95% CI 0.25–0.73, p = 0.002). Multivariate analysis showed that TILs are an independent prognostic indicator for DFS in all cohorts. In summary, this study indicated that TILs may reflect the immunological heterogeneity of NPC and could represent a new prognostic biomarker.     

Capn4 is a marker of poor clinical outcomes and promotes nasopharyngeal carcinoma metastasis via nuclear factor‐κB‐induced matrix metalloproteinase 2 expression

Calpain small subunit 1 (Capn4) plays a key role in tumor migration or invasion. In this study, expression and function of Capn4 was investigated in human nasopharyngeal carcinoma (NPC). Here we report that both mRNA and protein levels of Capn4 were elevated in NPC tissues when compared to normal NP tissues. Similarly, Capn4 was also highly expressed in multiple NPC cell lines, compared to immortalized human nasopharyngeal epithelial cell line NP69. Moreover, expression of Capn4 was significantly correlated with Epstein‐Barr virus infection, advanced stages, and lymph node or distant metastasis (P < 0.001). The patients with NPC displaying higher Capn4 had a significantly shorter overall survival (P = 0.002) and progression‐free survival (P = 0.003). Furthermore, siRNA knockdown of Capn4 suppressed cell migration and invasion in vitro and in vivo. These events resulted from Capn4 downregulation were associated with reduced expression of matrix metalloproteinase 2 (MMP2), Snail, and Vimentin. Finally, we demonstrated that Capn4 upregulated MMP2 via nuclear factor‐κB (NF‐κB) activation, manifested by increased phosphorylation of p65, a subunit of NF‐κB. Together, these findings argue a novel function of Capn4 in invasion and metastasis of NPC, and thereby suggest that Capn4 may represent an independent prognostic factor and a potential therapeutic target in NPC.     

Requirement of phosphatase of regenerating liver‐3 for the nucleolar localization of nucleolin during the progression of colorectal carcinoma

Phosphatase of regenerating liver‐3 (PRL‐3) is a protein tyrosine phosphatase (PTP) that is frequently overexpressed in liver metastases of colorectal carcinomas (CRCs). The PTP activity of the PRL‐3 protein is indispensable for the promotion of distant metastasis of CRC; however, little is known about the effect of PRL‐3 on cell growth. In this study, we investigated a novel protein that can connect to PRL‐3 to modulate the proliferation of CRC cells. In CRC‐derived SW480 cells, transduction of ectopic wild‐type PRL‐3, but not the C104S catalytic “dead” mutant, up‐regulated cell proliferation and increased the population of cells at the S and G₂/M phases. Also, inhibition of PTP activity of the PRL‐3 protein by treatment with the PRL‐3 inhibitor suppressed cell proliferation in a dose‐dependent manner as well as PRL‐3 knockdown by RNA interference. Using a comparative study of monodimensional gel electrophoresis of immunoprecipitates from PRL‐3‐transfected SW480 cells and subsequent mass spectrometry analysis, nucleolar‐specific protein nucleolin (NCL) was identified as a novel PRL‐3‐binding protein. We confirmed physiological interaction between PRL‐3 and NCL, and found that PRL‐3 phosphatase activity was associated with the suppression of the phospho‐NCL levels and nucleolar assembly of NCL protein. In CRC cases, nucleolar NCL expression was correlated not only with higher levels of PRL‐3 expression but also with frequent incidence of lymph node metastasis and a higher clinicopathologic stage. These findings suggest that NCL is involved in PRL‐3‐mediated cancer progression/metastasis signaling, which plays an important role in the acceleration of CRC growth. (Cancer Sci 2010)     

Multigene pathway‐based analyses identify nasopharyngeal carcinoma risk associations for cumulative adverse effects of TERT‐CLPTM1L and DNA double‐strand breaks repair

The genetic etiology of nasopharyngeal carcinoma (NPC) and mechanisms for inherited susceptibility remain unclear. To examine genetic risk factors for NPC, we hypothesized that heritable risk is attributable to cumulative effects of multiple common low‐risk variants. With the premise that individual SNPs only confer subtle effects for cancer risk, a multigenic pathway‐based approach was used to systematically examine associations between NPC genetic susceptibility with SNPs in genes in DNA repair pathways and from previously identified cancer genome‐wide association study analyses. This case–control study covers 161 genes/loci and focuses on pathway‐based analyses in 2,349 Hong Kong individuals, allowing stratification according to NPC familial status for meaningful association analysis. Three SNPs (rs401681, rs6774494 and rs3757318) corresponding to TERT/CLPTM1L (OR 95% CI = 0.77, 0.68–0.88), MDS1‐EVI1 (OR 95% CI=0.79 0.69–0.89) and CCDC170 (OR 95% CI = 0.76, 0.66–0.86) conferred modest protective effects individually for NPC risk by the logistic regression analysis after multiple testing adjustment (p_Bonferroni < 0.05). Stratification of NPC according to familial status identified rs2380165 in BLM (OR 95% CI = 1.49, 1.20–1.86, p_Bonferroni < 0.05) association with family history‐positive NPC (FH+ NPC) patients. Multiple SNPs pathway‐based analysis revealed that the combined gene dosage effects for increasing numbers of unfavorable genotypes in TERT‐CLPTM1L and double‐strand break repair (DSBR) conferred elevated risk in FH+ and sporadic NPC patients (ORs per allele, 95% CIs = 1.37, 1.22–1.55, p_Bonferroni = 5.00 × 10^?6; 1.17, 1.09–1.26, p_Bonferroni = 4.58 × 10^?4, respectively, in TERT/NHEJ pathways). Our data suggested cumulative increased NPC risk associations with TERT‐CLPTM1L and DSBR pathways contribute to genetic susceptibility to NPC and have potential translational relevance for patient stratification and therapeutics.     

Gene expression profile changes and possible molecular subtypes in differentiated‐type nonkeratinizing nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a human malignant tumor with a high incidence and a poor prognosis in Southern China and South‐eastern Asia. In this study, we comprehensively analyzed the gene expression profiles in 24 samples of primary differentiated‐type nonkeratining NPC (DNK‐NPC) tissues, 24 samples of normal nasopharyngeal tissues and 4 DNK‐NPC cell lines using cDNA microarray technology and bioinformatics methods. We found expression level of some genes was wildly alerted in the DNK‐NPC samples. In addition, our hierarchical clustering analysis revealed 2 distinctive subtypes of gene expression patterns in DNK‐NPC tissue samples. The discriminator genes were identified using a signal‐to‐noise (S₂N) algorithm by permuting of the data set 10,000 times. To further characterize the clinical relevance of the tumor subtypes, we evaluated a surrogate marker, CCND2, differentially expressed between the 2 tumor subgroups by using immunohistochemistry in an independent set of 137 DNK‐NPC samples. CCND2 was highly expressed in the subgroups with “aggressive” features and was associated with T classification (p = 0.006) and clinical stage (p = 0.013). Patients with high level of CCND2 expression had poorer overall survival than those with low level (p = 0.034). Our results suggest that DNK‐NPC can be classified into 2 subtypes based on gene expression patterns, which can be used in determining prognosis and treatment of the tumor.     

Significance of Plk1 regulation by miR‐100 in human nasopharyngeal cancer

Polo‐like kinase 1 (Plk1) is a critical regulator of many stages of mitosis; increasing evidence indicates that Plk1 overexpression correlates with poor clinical outcome, yet its mechanism of regulation remains unknown. Hence, a detailed evaluation was undertaken of Plk1 expression in human nasopharyngeal cancer (NPC), the cellular effects of targeting Plk1 using siRNA in combination with ionizing radiation (RT) and potential upstream microRNAs (miRs) that might regulate Plk1 expression. Using immunohistochemistry, Plk1 was observed to be overexpressed in 28 of 40 (70%) primary NPC biopsies, which in turn was associated with a higher likelihood of recurrence (p = 0.018). SiPlk1 significantly inhibited Plk1 mRNA and protein expression, and decreased Cdc25c levels in NPC cell lines. This depletion resulted in cytotoxicity of C666‐1 cells, enhanced by the addition of RT, mediated by G2/M arrest, increased DNA double‐strand breaks, apoptosis, and caspase activation. Immunofluorescence demonstrated that the G2/M arrest was associated with aberrant spindle formation, leading to mitotic arrest. In vivo, transfection of C666‐1 cells and systemic delivery of siPlk1 decreased tumour growth. MicroRNA‐100 (miR‐100) was predicted to target Plk1 mRNA, which was indeed underexpressed in C666‐1 cells, inversely correlating with Plk1 expression. Using luciferase constructs containing the 3′‐UTR of Plk1 sequence, we document that miR‐100 can directly target Plk1. Hence, our data demonstrate for the first time that underexpressed miR‐100 leads to Plk1 overexpression, which in turn contributes to NPC progression. Targeting Plk1 will cause mitotic catastrophe, with significant cytotoxicity both in vitro and in vivo, underscoring the important therapeutic opportunity of Plk1 in NPC.     

Evaluation of nonviral risk factors for nasopharyngeal carcinoma in a high‐risk population of Southern China

To understand the role of environmental and genetic influences on nasopharyngeal carcinoma (NPC) in populations at high risk of NPC, we have performed a case‐control study in Guangxi Province of Southern China in 2004–2005. NPC cases (n = 1,049) were compared with 785 NPC‐free matched controls who were seropositive for IgA antibodies (IgA) to Epstein‐Barr virus (EBV) capsid antigen (VCA)—a predictive marker for NPC in Chinese populations. A questionnaire was used to capture exposure and NPC family history data. Risk factors associated with NPC in a multivariant analysis model were the following: (i) a first, second or third degree relative with NPC [attributable risk (AR)= 6%, odds ratio (OR) = 3.1, 95% confidence interval (CI) = 2.0–4.9, p < 0.001]; (ii) consumption of salted fish 3 or more than 3 times per month (AR = 3%, OR = 1.9, 95% CI = 1.1–3.5, p = 0.035); (iii) exposure to domestic wood cooking fires for more than 10 years (AR = 69%, OR = 5.8, 95% CI = 2.5–13.6, p < 0.001); and (iv) exposure to occupational solvents for 10 or less years (AR = 4%, OR = 2.6, 95% CI = 1.4–4.8, p = 0.002). Consumption of preserved meats or a history of tobacco smoking were not associated with NPC (p > 0.05). We also assessed the contribution of EBV/IgA/VCA antibody serostatus to NPC risk—32.2% of NPC can be explained by IgA+ status. However, family history and environmental risk factors cumulatively explained only 2.7% of NPC development in NPC high risk population. These findings should have important public health implications for NPC risk reduction in endemic regions. © 2009 UICC     

Phosphatase of regenerating liver‐3 as a convergent therapeutic target for lymph node metastasis in esophageal squamous cell carcinoma

Phosphatase of regenerating liver‐3 (PRL‐3) is a molecule associated with metastasis in a diverse of cancers, which, however, remains largely unknown in esophageal squamous cell carcinoma (ESCC). We examined both the clinical significance of PRL‐3 expression and its biological roles, and assessed possibilities as a therapeutic target in ESCC. PRL‐3 expression was found in 78% (69 of 88) of the primary ESCC on immunohistochemistry; it was the strong independent predictor for lymph node metastasis (LNM) on a multivariate logistic regression model (p = 0.0014, relative risk =15.20). Additionally, gene amplification was found in 3 (7.9%) of the 38 primary tumors with PRL‐3 overexpression by fluorescence in situ hybridization, but in none of the 19 tumors without it. PRL‐3 small interfering RNA robustly repressed cell proliferation, anchorage‐independent colony formation and invasion and augmented 5‐FU‐induced apoptosis in all the tested ESCC cell lines with PRL‐3 overexpression, irrespective of its gene amplification status. PRL‐3 inhibitor (1‐4‐bromo‐2‐benzylidene rhodanine) also suppressed such metastatic properties in the cell lines with PRL‐3 overexpression, but not with its low expression. Inverse effects were observed by PRL‐3 forced expression. Collectively, PRL‐3 overexpression is a frequent event associated with LNM and plays a causative role in promoting cancer progression. Moreover, the expression status may be a landmark to select patients with benefit from PRL‐3‐targeted therapy. Thus, PRL‐3 could be a convergent therapeutic target against ESCC with LNM.     

miR‐185‐3p regulates nasopharyngeal carcinoma radioresistance by targeting WNT2B in vitro

Aberrant microRNA (miRNA) expression contributes to a series of malignant cancer behaviors, including radioresistance. Our previous study showed differential expression of miR‐185‐3p in post‐radiation nasopharyngeal carcinoma (NPC) cells. To investigate the role of miR‐185‐3p in NPC radioresistance, CNE‐2 and 5‐8F cells were transfected with miR‐185‐3p mimic and miR‐185‐3p inhibitor, respectively. CCK‐8 assay and colony formation experiment confirmed that the expression of miR‐185‐3p affected the radioresistance of NPC cells. A negative correlation between miR‐185‐3p and WNT2B expression was observed in NPC cells and tissues. Luciferase reporter assays confirmed that miR‐185‐3p directly targeted the coding region of WNT2B. Furthermore, we found radioresistance decreased in WNT2B‐silenced NPC cells. Activation of the WNT2B/β‐catenin pathway was accompanied by epithelial–mesenchymal transition biomarker changes in NPC. We concluded that miR‐185‐3p contributed to the radioresistance of NPC via modulation of WNT2B expression in vitro.     

微小RNA hsa-miR-93靶向STAT3提高鼻咽癌对放疗敏感性的机制研究

目的 研究hsa-miR-93在鼻咽癌放疗抗拒过程中的作用及分子机制。方法 以人鼻咽癌细胞株CNE-1、CNE-2、CNE-2R、HONE1、C666.1以及鼻咽上皮永生细胞NP460为研究对象,采用实时荧光定量PCR(qRT-PCR)法检测各组细胞经放疗后hsa-miR-93的表达;采用Western blot法检测各组细胞经放疗后STAT3蛋白的表达;通过miRWalk软件和RNAHybrid软件预测hsa-miR-93和STAT3的结合作用及结合位点;通过双荧光素酶报告基因法检测hsa-miR-93对STAT3靶向结合情况;瞬时转染小分子模拟物或抑制剂调控hsa-miR-93的表达后,采用qRT-PCR和Western blot法检测STAT3的表达;转染siSTAT3沉默STAT3的表达后,通过细胞集落形成实验检测鼻咽癌细胞经放疗后的集落形成能力。结果 与CNE-1、CNE-2细胞(相对放疗敏感)相比,hsa-miR-93在HONE1、CNE-2R细胞(相对放疗抗拒)中表达降低(P＜0.001),且各组鼻咽癌细胞经放疗后hsa-miR-93的表达呈剂量及时间依赖性降低(P＜0.05);与CNE-1、CNE-2细胞相比,STAT3在HONE1、CNE-2R细胞中表达升高,且各组鼻咽癌细胞经放疗后表达呈剂量及时间依赖性升高;经预测,hsa-miR-93可直接靶向结合STAT3。过表达hsa-miR-93可以在mRNA以及蛋白水平上显著抑制STAT3的表达(P＜0.05),而抑制hsa-miR-93的表达可以显著上调STAT3的表达(P＜0.05);过表达hsa-miR-93或沉默STAT3均使鼻咽癌细胞的集落形成显著减少(P＜0.001);抑制hsa-miR-93减弱了鼻咽癌对放疗的敏感性,而同时抑制hsa-miR-93和STAT3后,可提高鼻咽癌对放疗的敏感性。结论 hsa-miR-93可能通过靶向STAT3提高鼻咽癌对放疗的敏感性。     

Radiation‐induced sarcoma in patients with nasopharyngeal carcinoma

BACKGROUND:

The increasing incidence of radiation‐induced sarcoma (RIS) has become a significant problem that can limit long‐term survival. The objective of the current study was to analyze the clinicopathologic characteristics, treatment outcomes, and prognostic factors of RIS after radiotherapy for nasopharyngeal carcinoma (NPC).

METHODS:

Institutional electronic medical records of patients with NPC who received definitive radiotherapy between February 1964 and 2003 were reviewed. Fifty‐three patients who developed RIS and fulfilled the study criteria were included.

RESULTS:

The median follow‐up after a diagnosis of RIS was 15.5 months (range, 0.4‐90.3 months), and the median latency between radiotherapy for NPC and an RIS diagnosis was 9.3 years (range, 3.2‐26.6 years). Fibrosarcoma was the most frequent histologic type observed, followed by osteosarcoma, and malignant fibrous histiocytoma. The 3‐year overall survival (OS) rate for 49 patients who received treatment was 32.4%, and the median survival was 21.2 months (95% confidence interval, 8.7‐33.8 months). The median OS was 41.3 months, 8.4 months, and 11 months for the complete resection group, the incomplete resection group, and the chemotherapy group, respectively (P<.0001). The only independent predictive factor that was associated with better OS was complete surgical resection.

CONCLUSIONS:

This retrospective study confirmed the rarity and poor prognosis of RIS in patients with NPC. Complete surgical resection was a significant prognostic factor for survival. The authors concluded that long‐term follow‐up is necessary for the early detection of RIS in patients with NPC. Cancer 2010. © 2010 American Cancer Society.     

Functional characterization of THY1 as a tumor suppressor gene with antiinvasive activity in nasopharyngeal carcinoma

THY1 was previously identified as a candidate tumor suppressor gene (TSG) associated with lymph node metastases in nasopharyngeal carcinoma (NPC) through functional studies. It was identified by oligonucleotide microarray analysis as an interesting differentially expressed gene. However, direct functional evidence is still lacking for THY1 being a TSG in NPC, as in vivo tumorigenicity assays have not been previously reported in our last study of THY1. In this study, a tetracycline‐inducible expression vector, pETE‐Bsd, was used to obtain stable transfectants of THY1. The stringent in vivo tumorigenicity assay results show that the activation of THY1 suppresses tumor formation of HONE1 cells in nude mice, and the tumor formation ability was restored in the presence of doxycycline (a tetracycline analog), when the gene is shut off. Functional inactivation of this gene is observed in all the tumors derived from the tumorigenic transfectant. The tumor suppressive effect could be repressed by knockdown of THY1 expression in nontumorigenic microcell hybrids. Further studies indicate that expression of THY1 inhibits HONE1 cell growth in vitro by arresting cells in G₀/G₁ phase. It greatly reduces the ability for anchorage‐independent growth. The invasiveness of HONE1 cells was also inhibited by the expression of THY1. These findings suggest that THY1 is a TSG in NPC, which is involved in invasion and shows an association with tumor metastasis. Taken together, THY1 clearly plays an important functional role in tumor suppression in NPC.