Xiang-Ping Li

MiR-26a Inhibits Cell Growth and Tumorigenesis of Nasopharyngeal Carcinoma through Repression of EZH2

Several microRNAs (miRNA) have been implicated in nasopharyngeal carcinoma (NPC), a highly invasive and metastatic cancer that is widely prevalent in southern China. In this study, we report that microRNA miR-26a is commonly downregulated in NPC specimens and NPC cell lines with important functional consequences. Ectopic expression of miR-26a dramatically suppressed cell proliferation and colony formation by inducing G(1)-phase cell-cycle arrest. We found that miR-26a strongly reduced the expression of EZH2 oncogene in NPC cells. Similar to the restoring miR-26 expression, EZH2 downregulation inhibited cell growth and cell-cycle progression, whereas EZH2 overexpression rescued the suppressive effect of miR-26a. Mechanistic investigations revealed that miR-26a suppressed the expression of c-myc, the cyclin D3 and E2, and the cyclin-dependent kinase CDK4 and CDK6 while enhancing the expression of CDK inhibitors p14(ARF) and p21(CIP1) in an EZH2-dependent manner. Interestingly, cyclin D2 was regulated by miR-26a but not by EZH2, revealing cyclin D2 as another direct yet mechanistically distinct target of miR-26a. In clinical specimens, EZH2 was widely overexpressed and its mRNA levels were inversely correlated with miR-26a expression. Taken together, our results indicate that miR-26a functions as a growth-suppressive miRNA in NPC, and that its suppressive effects are mediated chiefly by repressing EZH2 expression.

MicroRNA-10b induced by Epstein-Barr virus-encoded latent membrane protein-1 promotes the metastasis of human nasopharyngeal carcinoma cells

MicroRNA-10b (miR-10b) has been reported to facilitate the metastasis of breast cancer. However, little is known about the role of miR-10b in the metastasis of nasopharyngeal carcinoma (NPC). Here, we show that high levels of miR-10b expression in Epstein-Barr virus (EBV)-positive latent membrane protein-1 (LMP1)-expressing NPC cells, and its expression is down-regulated by silencing LMP1 or Twist. Induction of miR-10b over-expression in LMP1-silent C666-1 cells promoted significant wound healing and transmembrane invasiveness in vitro. More importantly, miR-10b over-expression promoted the metastasis of NPC and accelerated the death of tumor-bearing nude mice. These findings strongly suggest that miR-10b positively regulates the metastasis of NPC.

The use of folate-PEG-grafted-hybranched-PEI nonviral vector for the inhibition of glioma growth in the rat.

Combined treatment using nonviral agent-mediated enzyme/prodrug therapy and immunotherapy had been proposed as a powerful alternative method of cancer therapy. The present study was aimed to evaluate the cytotoxicity in vitro and the therapeutic efficacy in vivo when the cytosine deaminase/5-fluorocytosine (CD/5-FC) and TNF-related apoptosis-inducing ligand (TRAIL) genes were jointly used against rat C6 glioma cells. The potency of the FA-PEG-PEI used as a nonviral vector was tested in the FR-expressed C6 glioma cells and Wistar rats. The C6 glioma cells and animal model were treated by the combined application of FA-PEG-PEI/pCD/5-FC and FA-PEG-PEI/pTRAIL. The antitumor effect was evaluated by survival assays and tumor volume. This study revealed a significant increase of cytotoxicity in vitro following the combined application of FA-PEG-PEI/pCD/5-FC and FA-PEG-PEI/pTRAIL treatments in C6 glioma cells. Animal studies showed a significant growth inhibition of the C6 glioma xenografts using the combined treatment. These results demonstrated that the combined treatment generated additive cytotoxic effect in C6 glioma cells in both in vitro and in vivo conditions, and indicated that such treatment method using both enzyme/prodrug therapy and TRAIL immunotherapy might be a promising therapeutic strategy in treating glioma.

Suppression of tumorigenicity by MicroRNA-138 through inhibition of EZH2-CDK4/6-pRb-E2F1 signal loop in glioblastoma multiforme

Deregulation of microRNAs (miRNAs) is implicated in tumor progression. We attempt to identify the tumor suppressive miRNA not only down-regulated in glioblastoma multiforme (GBM) but also potent to inhibit the oncogene EZH2, and then investigate the biological function and pathophysiologic role of the candidate miRNA in GBM. In this study, we show that miRNA-138 is reduced in both GBM clinical specimens and cell lines, and is effective to inhibit EZH2 expression. Moreover, high levels of miR-138 are associated with long overall and progression-free survival of GBM patients from The Cancer Genome Atlas dataset (TCGA) data portal. Ectopic expression of miRNA-138 effectively inhibits GBM cell proliferation in vitro and tumorigenicity in vivo through inducing cell cycles G1/S arrest. Mechanism investigation reveals that miRNA-138 acquires tumor inhibition through directly targeting EZH2, CDK6, E2F2 and E2F3. Moreover, an EZH2-mediated signal loop, EZH2-CDK4/6-pRb-E2F1, is probably involved in GBM tumorigenicity, and this loop can be blocked by miRNA-138. Additionally, miRNA-138 negatively correlates to mRNA levels of EZH2 and CDK6 among GBM clinical samples from both TCGA and our small amount datasets. In conclusion, our data demonstrate a tumor suppressive role of miRNA-138 in GBM tumorigenicity, suggesting a potential application in GBM therapy.

miR-26a inhibits invasion and metastasis of nasopharyngeal cancer by targeting EZH2

Nasopharyngeal carcinoma (NPC) is a highly invasive and metastatic type of cancer that is widely prevalent in Southern China. Studies have shown that several microRNAs (miRNAs) are implicated in NPC metastasis. Our previous studies have demonstrated that miRNA miR-26a inhibits cell growth and tumorigenesis of NPC through the repression of enhancer of zeste homolog 2 (EZH2). However, the role of miR-26a in NPC metastasis remains unknown. In this study, we showed that ectopic expression of miR-26a inhibited the migratory and invasive capacities of NPC cells in vitro. Additionally, we used a murine model to investigate the role of miR-26a in NPC metastasis and results showed that miR-26a overexpression suppresses the metastatic behavior of NPC cells in vivo. Furthermore, the data demonstrated that miR-26a decreased the expression levels of EZH2 in vitro and in vivo, suggesting that the antimetastatic effect of miR-26a in NPC was mediated by regulating EZH2. Therefore, these findings indicate that miR-26a functions as an antimetastatic miRNA in NPC and that its antimetastatic effects are mediated mainly by repressing EZH2 expression.

TBX2 and TBX3: The special value for anticancer drug targets

Abstract TBX2 and TBX3 are members of the T-box family of transcription factors, which are implicated in embryonic development. Unlike most members of the T-box family, TBX2 and TBX3 are the only mammalian T-box factors which function as transcriptional repressors, mediated by the repression domain in the C-terminal. In addition to a role in development, recent evidence suggests that TBX2 and TBX3 are overexpressed in a number of cancers, including melanoma, breast, liver, lung, pancreas, ovarian, and cervical cancers. However, there is little information about the mechanisms for how these T-box genes contribute to tumorigenesis. Upregulation of TBX2 and TBX3 suppresses the expression of p14ARF and p21CIP1 and promotes bypass of senescence through inactivation of p53 pathway. TBX2 functionally interacts with pRb, and pRb modulates TBX2 functional specificity. In addition, TBX2 is a player of Wnt signaling while TBX3 is a downstream target of the Wnt/beta-catenin pathway, and overexpression of TBX2 and TBX3 represses the expression of E-cadherin, which is demonstrated to be a prerequisite for epithelial tumor cell invasion. Moreover, TBX2 is shown to interact with EGR1 to block multiple downstream tumor suppressors. Here, we review the current knowledge on TBX2 and TBX3 in tumorigenesis and prospect their special value for development of target-based anticancer drugs.

Correlation of pepsin-measured laryngopharyngeal reflux disease with symptoms and signs

OBJECTIVE: Pepsin detection in throat sputum has been posited as a reliable biological marker of laryngopharyngeal reflux disease (LPRD). This study was designed to further correlate pepsin concentration with symptoms and signs of LPRD. STUDY DESIGN: Cross-sectional study. SETTING: Nanfang Hospital of Southern Medical University. SUBJECTS AND METHODS: Fifty-six laryngitis patients were divided into a reflux laryngitis group and a chronic laryngitis group based on the reflux symptom index (RSI), reflux finding score (RFS), and proton pump inhibitor treatment for two weeks. Oral and hypopharyngeal secretions from the study patients and from 15 healthy subjects were collected. Thirty-six obstructive sleep apnea (OSA) patients were divided into a mild-moderate group and a severe group by the apnea-hypopnea index (AHI). Bedtime and first-morning oral secretions were collected. Enzyme-linked immunosorbent assay was used to measure the pepsin concentration. RESULTS: In laryngitis patients, the total score of RSI and RFS (P < 0.05), and the symptoms, including clearing throat often, coughing, and sensing a lump in the throat (P < 0.006), were more severe in the pepsin-positive group. No significant differences were found between the oral and hypopharyngeal secretions. In OSA, pepsin levels in the first-morning oral secretions were correlated with AHI, mean SaO2, and mini SaO2 (P < 0.01). However, RSIs were not significantly correlated with these indicators. CONCLUSION: Higher levels of pepsin in sputum were associated with higher RSI and RFS in cases of laryngitis. There was no relationship between pepsin levels and RSI in cases of OSA. There were no differences of pepsin concentration in sputum collection methods or in collection timing.

Diagnostic and prognostic value of plasma microRNA deregulation in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is uncommon worldwide but often highly invasive in late stages. Due to its special location and lack of specific symptoms, NPC is hardly detected in regular medical examination at the beginning. Development of sensitive and specific biomarkers should help to save lives against this type of disease. In the present report, we investigated the value of plasma miRNAs for diagnosis and prognosis of NPC. Using candidate approach, we selected 21 miRNAs from literature to compare their expression levels in the plasma of NPC patients and controls. As a result, 5 miRNAs showed diagnostic potentials (P < 0.01). Among them, miR-16, -21, -24, and -155 had increased levels in NPC patients, whereas the level of miR-378 was decreased. There was a negative correlation between plasma miRNA expression and cancer progression, where miR-21 was statistically significant in T and N staging and miR-16 and 24 were significant in N staging only. Combination of miR-16, -21, -24, -155, and -378 gives 87.7% of sensitivity and 82.0% of specificity for NPC diagnosis. Without miR-16, combination of the rest 4 miRNAs gives the same sensitivity but a slightly reduced specificity. After treatment, all 5 miRNAs were somewhat back to normal levels in patients without cancer recurrence but the prognostic value was not statistically significant. In conclusion, plasma miRNA expression is a useful biomarker for NPC diagnosis but not for its prognosis. More importantly, it is simple, effective, and non-invasive. Combination of several plasma miRNAs can increase both NPC diagnostic sensitivity and specificity.

Inhibition of human nasopharyngeal carcinoma growth and metastasis in mice by adenovirus-associated virus–mediated expression of human endostatin

Nasopharyngeal carcinoma (NPC) is a highly malignant and frequently metastasized tumor. Endostatin has been shown to inhibit NPC growth, but its efficacy against NPC metastasis has not been shown in vivo. Here, we established a NPC metastasis model in mice by transplanting EBV-positive NPC cells, C666-1, in the livers of nude mice and observed lung metastasis. Furthermore, we showed that tail vein injection of recombinant adeno-associated virus encoding human endostatin (rAAV-hEndo) significantly prolonged the median survival rate of NPC metastasis–bearing mice (from 22 to 37 days, P < 0.01). The rAAV-hEndo treatment resulted in a statistically significant reduction in tumor growth and microvessel formation. It also increased the apoptotic index in the primary liver tumor but not in the normal liver tissue. Importantly, no formation of liver or lung metastasis was detected. The potent inhibition of NPC metastasis suggests the feasibility of combining rAAV-hEndo gene therapy with other therapies for the prevention and treatment of NPC metastasis. [Mol Cancer Ther 2006;5(5):1290–8]

Gold(III) porphyrin 1a inhibited nasopharyngeal carcinoma metastasis in vivo and inhibited cell migration and invasion in vitro

A physiologically stable gold compound, gold(III) meso-tetraphenylporphyrin (gold-1a), has been shown to be effective in inducing apoptosis and prolonging the survival of hepatocellular carcinoma (HCC)-bearing rats as well as inhibiting the tumor growth of mice bearing nasopharyngeal carcinoma (NPC), neuroblastoma and colon carcinoma. In this study, we showed that gold-1a prolonged the survival of NPC metastasis-bearing mice and inhibited intrahepatic and lung metastasis. Histologically, gold-1a markedly reduced tumor microvessel formation. Consistently, in in vitro studies, gold-1a inhibited migration and invasion of C666-1 human NPC cells. The data strongly support the use of gold(III) compounds to treat cancer metastasis.