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Significance Host genetics, environmental factors, and EBV infection together contribute to nasopharyngeal carcinoma (NPC) development. A number of critical genetic and epigenetic events contributing to tumor development has been reported. However, the genomic alterations in NPC have not been completely deciphered. We used the whole-exome sequencing approach to study the somatic mutations in NPC, and an APOBEC-mediated mutagenesis signature was revealed. Importantly, multiple loss-of-function mutations in the NF-κB–negative regulators ( NFKBIA , CYLD , and TNFAIP3 ) were discovered in NPC tumors, and we functionally confirmed that the NFKBIA loss-of-function mutations induce damaging effects on the WT proteins. Detection of these mutations emphasizes the critical role of NF-κB signaling in NPC tumorigenesis and provides perspectives for targeting this pathway in NPC treatment.

Nidogen-2 (NID2) is a key component of the basement membrane that stabilizes the extracellular matrix (ECM) network. The aim of the study is to analyze the functional roles of NID2 in the pathogenesis of nasopharyngeal carcinoma (NPC) and esophageal squamous cell carcinoma (ESCC). We performed genome-wide methylation profiling of NPC and ESCC and validated our findings using the methylation-sensitive high-resolution melting (MS-HRM) assay. Results showed that promoter methylation of NID2 was significantly higher in NPC and ESCC samples than in their adjacent non-cancer counterparts. Consistently, down-regulation of NID2 was observed in the clinical samples and cell lines of both NPC and ESCC. Re-expression of NID2 suppresses clonogenic survival and migration abilities of transduced NPC and ESCC cells. We showed that NID2 significantly inhibits liver metastasis. Mechanistic studies of signaling pathways also confirm that NID2 suppresses the EGFR/Akt and integrin/ FAK/PLCγ metastasis-related pathways. This study provides novel insights into the crucial tumor metastasis suppression roles of NID2 in cancers., published_or_final_version

Background: Cancer is a global health burden; the outcome varies widely across all countries. Sharing of experience in setting health policy (including health expenditure) is important. However, there is yet no comprehensive comparison of cancer outcome across all countries. Furthermore, comparison of cost-effectiveness of different systems is especially complex because the incidence of different cancers varies across countries, and their chances of curability differ substantially. Aim: We aims to provide the comparisons using available data and to stimulate global attention to the association of economic parameters with different outcomes. Methods: Cancer statistics from all 184 countries and 27 major cancers listed in GLOBOCAN 2012 were analyzed. The overall outcome of cancer patients was estimated by taking the complement of age-standardized mortality/incidence ratio [1 − (ASM/ASI)] as the proxy relative survival (RS). Taking into account the variation of country-specific cancer pattern, the proxy cancer site-standardized RS (SS-RS) of individual countries were calculated by weighting the proportion of specific cancer sites as compared with the global pattern of incidence. The overall economic parameters of different countries listed by the World Bank were correlated with the corresponding proxy SS-RS. Results: The unadjusted proxy RS among the 184 countries ranged from 0.111 to 0.702 (median = 0.386), the corresponding proxy SS-RS ranged from 0.124 to 0.622 (median = 0.359). The median total health expenditure per capita (HE) increased from US$37 for countries with proxy SS-RS < 0.2, to $4255 for countries with proxy SS-RS ≥ 0.5. Results from logarithmic regression model showed exponential increase in total HE for better outcome. The expenditure varied widely among different strata, but the widest difference was observed among countries with SS-RS ≥ 0.5 (with total HE ranging from US$962 to $9361). Conclusion: Similar to age-standardization, estimation of outcome with adjustment for variation in pattern of cancer incidence is suggested for comparison among different countries, especially for studies related to assessment of health systems. Cancer outcome correlated significantly with economic parameters; the amount of HE escalated exponentially and varied widely among countries with high SS-RS ≥ 0.5. Sharing of experience among different countries will be valuable for developing the most cost-effective health system.

Background and Aim: Adjuvant chemoradiation (CRT) after curative gastrectomy was introduced to our hospital in 1998. The present study aims to examine the impact of CRT on survival among Chinese. Methods: From our gastric cancer registry, patients who received R0 gastrectomy, with UICC stage II or above, M0 disease and ASA grades I and II were analyzed. Adjuvant CRT was offered and given if patients agreed. The regimen consisted of five cycles of 5-fluoruracil (5FU)/leucovorin chemotherapy and 45 Gy/25 fractions concurrent with cycles 2 and 3. Results: From January 1998 to December 2004, 134 patients fulfilled the criteria. Sixty had surgery alone and 74 patients received CRT after gastrectomy. One hundred and two (76%) patients received radical gastrectomy with D2 lymphadenectomy. Toxicity ≥ grade 3 was seen in 65% of patients without mortality. The overall and relapse-free 5-year survival rates were 45.8% and 42.0%, respectively. On univariate analysis, early disease stage and adjuvant CRT were associated with better prognosis. Cox regression analysis showed that adjuvant CRT (P = 0.01, HR 2.31, 95% CI: 1.4–3.9) predict better survival after adjustment with the other factors. Conclusion: In the present study, postoperative adjuvant chemoradiation is associated with better overall survival in patients with adenocarcinoma of the stomach after curative gastrectomy.

Aims: The docetaxel and cyclophosphamide (TC) regimen is increasingly popular as adjuvant chemotherapy for operable breast cancers. We conducted a retrospective study in Hong Kong to evaluate the toxicity of this regimen in Chinese patients. Methods: Between January 2007 and May 2008 76 female Chinese patients with resected stage I–III operated invasive breast cancer were treated with 4 cycles of TC (75 and 600 mg/m2, respectively, administered i.v. every 3 weeks for four cycles) in two public regional cancer centers of Hong Kong. A total of 24 (32%) patients also received primary prophylactic ciprofloxacin (500 mg twice daily, day 5–14). Chemotherapy-related toxicities were graded by the CTCAE version 3.0. Results: The median age was 50 (range 26–67). A total of 68 (89%) patients successfully completed four cycles of chemotherapy. 72 (95%) and 16 (21%) patients developed grade 3–4 neutropenia and febrile neutropenia (FN) infection, respectively, in one or more cycles. However, no grade 3–4 anemia or thrombocytopenia events were observed. Other grade 3–4 non-hematological toxicities were also uncommon, apart from allergic reactions in two (3%) patients. No viral reactivation was observed among the 8 hepatitis B carriers. Patients with prophylactic ciprofloxacin had less grade 3–4 FN infection (13% vs 25%, P = 0.214) and a higher chance of receiving the full scheduled dose (88% vs 62%, P = 0.045) than patients without. Conclusion: The myelotoxicity of TC was substantially higher in Chinese patients compared with non-Chinese patients in developed countries. Routine prophylactic measures are recommended to maintain the dose levels and reduce the risk of FN.

Incorporating various new and conventional risk factors, the 2005 St Gallen risk categorization is a potentially useful prognostic tool for breast cancers. We conducted a retrospective study to evaluate its application in Hong Kong. Of the 902 included female breast cancers with median follow-up of 5.4 years, 7%, 63% and 30% patients were classified as low-, intermediate- and high-risk categories, respectively. Their corresponding 5-year distant disease-free survivals (DDFS) were 100%, 92% and 72%, respectively (p0.00005). In the intermediate-risk category, node-positive patients had marginally inferior 5-year DDFS than node-negative patients (89% vs. 93%, p=0.0551). In the high-risk category, patients having HER2 overexpressed tumors and 1-3 positive nodes had significantly better DDFS than other patients withor = 4 positive nodes (89% vs. 65%, p=0.0001). Overall, the 2005 St Gallen risk categorization had high prognostic value. However, the impact of HER2 overexpression might be affected by reproducibility of HER2 tests.

Nasopharyngeal carcinoma (NPC) is an EBV-associated epithelial malignancy prevalent in southern China. Presence of treatment-resistant cancer stem cells (CSC) may associate with tumor relapse and metastasis in NPC. ICG-001 is a specific CBP/β-catenin antagonist that can block CBP/β-catenin-mediated transcription of stem cell associated genes and enhance p300/β-catenin-mediated transcription, thereby reducing the CSC-like population via forced differentiation. In this study, we aimed to evaluate the effect of ICG-001 on the CSC-like population, and the combination effect of ICG-001 with cisplatin in the C666-1 EBV-positive NPC cells. Results showed that ICG-001 inhibited C666-1 cell growth and reduced expression of CSC-associated proteins with altered expression of epithelial-mesenchymal transition (EMT) markers. ICG-001 also inhibited C666-1 tumor sphere formation, accompanied with reduced SOX2 hi /CD44 hi CSC-like population. ICG-001 was also found to restore the expression of a tumor suppressive microRNA-145 (miR-145). Ectopic expression of miR-145 effectively repressed SOX2 protein expression and inhibited tumor sphere formation. Combination of ICG-001 with cisplatin synergistically suppressed in vitro growth of C666-1 cells and significantly suppressed growth of NPC xenografts. These results suggested that therapeutically targeting of the CBP/β-catenin signaling pathway with ICG-001 can effectively reduce the CSC-like population and combination with cisplatin can effectively suppress the growth of NPC., link_to_OA_fulltext

Altered patterns of DNA methylation are key features of cancer. Nasopharyngeal carcinoma (NPC) has the highest incidence in Southern China. Aberrant methylation at the promoter region of tumor suppressors is frequently reported in NPC; however, genome-wide methylation changes have not been comprehensively investigated. Therefore, we systematically analyzed methylome data in 25 primary NPC tumors and nontumor counterparts using a high-throughput approach with the Illumina HumanMethylation450 BeadChip. Comparatively, we examined the methylome data of 11 types of solid tumors collected by The Cancer Genome Atlas (TCGA). In NPC, the hypermethylation pattern was more dominant than hypomethylation and the majority of de novo methylated loci were within or close to CpG islands in tumors. The comparative methylome analysis reveals hypermethylation at chromosome 6p21.3 frequently occurred in NPC (false discovery rate; FDR=1.33 × 10(-9) ), but was less obvious in other types of solid tumors except for prostate and Epstein-Barr virus (EBV)-positive gastric cancer (FDR10(-3) ). Bisulfite pyrosequencing results further confirmed the aberrant methylation at 6p in an additional patient cohort. Evident enrichment of the repressive mark H3K27me3 and active mark H3K4me3 derived from human embryonic stem cells were found at these regions, indicating both DNA methylation and histone modification function together, leading to epigenetic deregulation in NPC. Our study highlights the importance of epigenetic deregulation in NPC. Polycomb Complex 2 (PRC2), responsible for H3K27 trimethylation, is a promising therapeutic target. A key genomic region on 6p with aberrant methylation was identified. This region contains several important genes having potential use as biomarkers for NPC detection.

Nasopharyngeal carcinoma (NPC) is a cancer that occurs in high frequency in Southern China. A previous functional complementation approach and the subsequent cDNA microarray analysis have identified that serum amyloid A1 (SAA1) is an NPC candidate tumor suppressor gene. SAA1 belongs to a family of acute-phase proteins that are encoded by five polymorphic coding alleles. The SAA1 genotyping results showed that only three SAA1 isoforms (SAA1.1, 1.3 and 1.5) were observed in both Hong Kong NPC patients and healthy individuals. This study aims to determine the functional role of SAA1 polymorphisms in tumor progression and to investigate the relationship between SAA1 polymorphisms and NPC risk. Indeed, we have shown that restoration of SAA1.1 and 1.3 in the SAA1-deficient NPC cell lines could suppress tumor formation and angiogenesis in vitro and in vivo. The secreted SAA1.1 and SAA1.3 proteins can block cell adhesion and induce apoptosis in the vascular endothelial cells. In contrast, the SAA1.5 cannot induce apoptosis or inhibit angiogenesis because of its weaker binding affinity to αVβ3 integrin. This can explain why SAA1.5 has no tumor-suppressive effects. Furthermore, the NPC tumors with this particular SAA1.5/1.5 genotype showed higher levels of SAA1 gene expression, and SAA1.1 and 1.3 alleles were preferentially inactivated in tumor tissues that were examined. These findings further strengthen the conclusion for the defective function of SAA1.5 in suppression of tumor formation and angiogenesis. Interestingly, the frequency of the SAA1.5/1.5 genotype in NPC patients was ~2-fold higher than in the healthy individuals (P=0.00128, odds ratio=2.28), which indicates that this SAA1 genotype is significantly associated with a higher NPC risk. Collectively, this homozygous SAA1.5/1.5 genotype appears to be a recessive susceptibility gene, which has lost the antiangiogenic function, whereas SAA1.1 and SAA1.3 are the dominant alleles of the tumor suppressor phenotype.

Background: Despite salted fish being a classical risk factor of Nasopharyngeal Carcinoma (NPC), whether secular trends in salted fish consumption worldwide accounted for changes in NPC rates were unknown. The relationship between vegetable and cigarette consumption to NPC risk worldwide were also largely uncertain. We investigated the longitudinal trends in standardised NPC incidence/mortality rates across 8 regions and their associations with secular trends in salted fish, vegetable and tobacco consumptions. Methods: Age standardised mortality rate (ASMR) and age standardised incidence rate (ASIR) of NPC were obtained from the WHO cancer mortality database and Hong Kong Cancer Registry. Per capita consumption of salted fish, tobacco and vegetables in Hong Kong and 7 countries (China, Finland, Japan, Portugal, Singapore, United Kingdom and United States) were obtained from the Food and Agriculture Organization of the United Nation (FAO) and Hong Kong Trade and Census Statistics. Pearson correlation and multivariate analysis were performed to examine both crude and adjusted associations. Results: There were markedly decreasing trends of NPC ASIR and ASMR in Hong Kong over the past three decades, which were correlated with corresponding secular changes in salted fish consumption per capita (Pearson r for 10 cumulative years : ASIR = 0.729 (male), 0.674 (female); ASMR = 0.943 (male), 0.622 (female), all p < 0.05 except for female ASMR). However such associations no longer correlated with adjustments for decreasing tobacco and increasing vegetable consumption per capita (Pearson r for 10 cumulative years: ASIR = 2.007 (male), 0.339 (female), ASMR = 0.289 (male), 1.992 (female), all p > 0.05). However, there were no clear or consistent patterns in relations between NPC ASIR and ASMR with salted fish consumption across 7 regions in 3 continents. Conclusions: Our results do not support the notion that changes in salted fish consumption had played an important role in explaining secular trends of NPC rates in Hong Kong and worldwide. Further studies should explore other lifestyle and genetic factors. However, our findings do support the potentially protective effects of vegetable consumption against NPC., published_or_final_version

This study identified LTBP-2 as a pleiotropic tumor suppressor in nasopharyngeal carcinoma, which safeguards against critical malignant behaviors of tumor cells. LTBP-2 expression was significantly decreased or lost in up to 100% of NPC cell lines (7/7) and 80% of biopsies (24/30). Promoter hypermethylation was found to be involved in LTBP-2 silencing. Using a tetracycline-regulated inducible expression system, we unveiled functional roles of LTBP-2 in suppressing colony formation, anchorage-independent growth, cell migration, angiogenesis, VEGF secretion, and tumorigenicity. Three-dimensional culture studies suggested the involvement of LTBP-2 in maintenance of tumor cell dormancy in a growth factor favorable microenvironment.

Alpha B-crystallin (CRYAB) maps within the nasopharyngeal carcinoma (NPC) tumor-suppressive critical region 11q22-23 and its downregulation is significantly associated with the progression of NPC. However, little is known about the functional impact of CRYAB on NPC progression. In this study we evaluated the NPC tumor-suppressive and progression-associated functions of CRYAB. Activation of CRYAB suppressed NPC tumor formation in nude mice. Overexpression of CRYAB affected NPC progression-associated phenotypes such as loss of cell adhesion, invasion, interaction with the tumor microenvironment, invasive protrusion formation in three dimensional Matrigel culture, as well as expression of epithelial-mesenchymal transition-associated markers. CRYAB mediates this ability to suppress cancer progression by inhibition of E-cadherin cytoplasmic internalization and maintenance of β-catenin in the membrane that subsequently reduces the levels of expression of critical downstream targets such as cyclin-D1 and c-myc. Both ectopically expressed and recombinant CRYAB proteins were associated with endogenous E-cadherin and β-catenin, and, thus, the cadherin/catenin adherens junction. The CRYAB α-crystallin core domain is responsible for the interaction of CRYAB with both E-cadherin and β-catenin. Taken together, these results indicate that CRYAB functions to suppress NPC progression by associating with the cadherin/catenin adherens junction and modulating the β-catenin function.

Annual surveillance mammography is commonly recommended after breast conservation therapy (BCT). We retrospectively reviewed its effectiveness on 511 invasive and non-invasive breast cancers treated with BCT between 1994 and 2003. The median follow-up was 5.9 years. The 5-year actuarial ipsilateral breast tumour recurrence (IBTR) rate was 4.5% and contralateral breast cancer (CBC) rate was 2.0% (representing eight times increase in risk). IBTR of 43% and 62% CBC were first detected by surveillance mammography. The IBTR detection rates per 1000 mammograms were 5.2 for patients (n=349) with one or more IBTR risk factors (age 45, positive/close margins or histological grade 3) and 0.6 for patients (n=162) without. No survival difference was observed between different modes of IBTR detection (p=0.342). In conclusion, a risk-adapted approach of limiting ipsilateral surveillance to patients with IBTR risk is possible but its implementation will be complicated by the continued need of contralateral surveillance.

Background: Nasopharyngeal carcinoma (NPC) has the highest incidence in Guangdong province and Hong Kong in Southern China. Early detection of NPC is necessary to improve patient survival. Although aberrant methylation at promoter region of the tumour suppressors were often reported in NPC, genome-wide methylation changes have not been comprehensively investigated. Aim: We aimed to examine the methylation profile of NPC patient tumours using a high-throughput approach to discover candidate biomarkers for early detection of NPC. Methods: We systematically analyzed methylome data in the primary tumours and matched normal adjacent tissues from 25 NPC patients collected by Area of Excellence (AoE) NPC Tissue Bank using the Illumina HumanMethylation450 BeadChip platform. Comparatively, methylome data of solid tumours including prostate cancer, invasive breast cancer, pancreatic cancer, kidney cancer, thyroid cancer, liver cancer, rectal cancer, colon cancer, head and neck cancer, lung adenocarcinoma and lung squamous cell carcinoma collected by The Cancer Genome Atlas (TCGA) were examined. A quantitative method, bisulfite pyrosequencing, was applied to evaluate the aberrant methylation in an independent NPC patient cohort. Results: In NPC, the hypermethylation pattern was more dominant than hypomethylation, where over 90% of the differentially methylated loci were hypermethylated within or close to CpG islands in tumours. The comparative methylome analysis reveals aberrant methylation at chromosome 6p frequently occurred in NPC (FDR = 1.33×10-9), but was rare in other types of solid tumours. Evident enrichment of the repressive mark H3K27me3 was found at this region, indicating both DNA methylation and histone modification function together, leading to epigenetic deregulation. Bisulfite pyrosequencing results further confirmed the aberrant methylation at 6p in an additional patient cohort, and 76.9% of the early-stage NPC patients can be detected by aberrant methylation on 6p. Furthermore, aberrant methylation at this region was observed in NPC recurrent tumours and matched metastatic lymph nodes, indicating the potential use of genes in this region for prognosis. Conclusion: Our study highlights the importance of epigenetic deregulation in NPC. A novel genomic region on 6p with aberrant methylation was identified. This region contains several important genes that have great potential to be used as biomarkers for NPC early detection. The global genome-wide unbiased approach is useful to discover potential biomarkers for early diagnosis and prognosis in cancers. Acknowledgements: NPC AoE funding was provided by the Hong Kong Research Grants Council (AoE/M-06/08) to MLL and HKU Small Project Funding to WD. Citation Format: Wei Dai, Arthur Kwok Leung Cheung, Josephine Mun Yee Ko, Hong Zheng, Yue Cheng, Roger Kai Cheong Ngan, Wai Tong Ng, Anne Wing Mui Lee, Chun Chung Yau, Victor Ho Fu Lee, Maria Li Lung. Aberrant methylation at chromosome 6p as novel biomarkers for diagnosis and prognosis of nasopharyngeal carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4773. doi:10.1158/1538-7445.AM2015-4773

NF-κB is a well-characterized transcription factor, widely known as a key player in tumor-derived inflammation and cancer development. Herein, we present the functional and molecular relevance of the canonical NF-κB p65 subunit in nasopharyngeal carcinoma (NPC). Loss- and gain-of-function approaches were utilized to reveal the functional characteristics of p65 in propagating tumor growth, tumor-associated angiogenesis, and epithelial-to-mesenchymal transition in NPC cells. Extracellular inflammatory stimuli are critical factors that trigger the NF-κB p65 signaling; hence, we investigated the components of the tumor microenvironment that might potentially influence the p65 signaling pathway. This led to the identification of an extracellular matrix (ECM) protein that was previously reported as a candidate tumor suppressor in NPC. Our studies on the Latent Transforming Growth Factor-β Binding Protein 2 (LTBP2) protein provides substantial evidence that it can modulate the p65 transcriptional activity. Re-expression of LTBP2 elicits tumor suppressive effects that parallel the inactivation of p65 in NPC cells. LTBP2 was able to reduce phosphorylation of p65 at Serine 536, inhibit nuclear localization of active phosphorylated p65, and impair the p65 DNA-binding ability. This results in a consequential down-regulation of p65-related gene expression. Therefore, the data suggest that the overall up-regulation of p65 expression and the loss of this candidate ECM tumor suppressor are milestone events contributing to NPC development.

Background. The purpose of this study was to evaluate the efficacy and toxicity of cisplatin plus gemcitabine as induction chemotherapy in advanced nasopharyngeal carci- noma (NPC). Methods. Thirty-seven patients with stage IV(A-B) NPC were treated with 3 cycles of cisplatin plus gemcitabine (cisplatin 80 mg/m 2 on day 1; gemcitabine 1250 mg/m 2 on days 1 and 8) 3-weekly as induction chemotherapy, followed by another 3 cycles of concurrent cisplatin (100 mg/m 2 on day 1) 3-weekly with accelerated radiotherapy (RT) at 70 Gy in 2-Gy fractions, 6 daily fractions per week. Results. The overall response rate to induction chemother- apy was > 90%, and side effects other than uncomplicated he- matologic toxicities were uncommon. All patients completed RT, with 92% receiving � 5 cycles of chemotherapy. At a median fol- low-up of 2.9 years, the 3-year overall survival (OS) and disease- free survival (DFS) rates were 76% and 63%, respectively. Conclusions. Cisplatin plus gemcitabine is a well-tolerated, effective, and convenient induction chemotherapy regimen and warrants further studies to confirm its benefit in advanced NPC. V C 2006 Wiley Periodicals, Inc. Head Neck 28: 880-887, 2006

1512 Background: Nasopharyngeal carcinoma (NPC) is well known for its peculiarly skewed distribution with highest incidence in Southern Chinese population. As familial aggregation is evident, scree...

11019 Background: Breast cancer risk categories were revised by the St Gallen international expert consensus meeting in 2005. This study was to validate their application in Hong Kong. Methods: The clinical outcomes of female breast cancer patients presented from 1994 to 2002 were retrospectively analyzed. Patients with non-invasive cancers, unknown HER-2 status, unclear primary (T) or nodal (N) stage, distant metastases at presentation, induction chemotherapy or no definitive surgery were excluded. Results: 902 breast cancers were eligible for further analysis. Adjuvant radiotherapy, hormonal therapy and chemotherapy were given in 74%, 68% and 56% of patients respectively. The median follow-up was 5.4 years (range 0.3- 12.5 years). The risk categories were highly predictive of all survival outcome parameters (p [Table: see text] No significant financial relationships to disclose.

Background Nasopharyngeal carcinoma (NPC) is an epithelial malignancy strongly associated with Epstein-Barr virus (EBV). AT13387 is a novel heat shock protein 90 (Hsp90) inhibitor, which inhibits the chaperone function of Hsp90 and reduces expression of Hsp90-dependent client oncoproteins. This study aimed to evaluate both the in vitro and in vivo antitumor effects of AT13387 in the EBV-positive NPC cell line C666-1. Results Our results showed that AT13387 inhibited C666-1 cell growth and induced cellular senescence with the downregulation of multiple Hsp90 client oncoproteins EGFR, AKT, CDK4, and restored the protein expression of negative cell cycle regulator p27. We also studied the ability of AT13387 to restore p27 expression by downregulation of AKT and the p27 ubiquitin mediator, Skp2, using AKT inhibitor and Skp2 siRNA. In the functional study, AT13387 inhibited cell migration with downregulation of a cell migration regulator, HDAC6, and increased the acetylation and stabilization of α-tubulin. We also examined the effect of AT13387 on putative cancer stem cells (CSC) by 3-D tumor sphere formation assay. AT13387 effectively reduced both the number and size of C666-1 tumor spheres with decreased expression of NPC CSC-like markers CD44 and SOX2. In the in vivo study, AT13387 significantly suppressed tumor formation in C666-1 NPC xenografts. Conclusion AT13387 suppressed cell growth, cell migration, tumor sphere formation and induced cellular senescence on EBV-positive NPC cell line C666-1. Also, the antitumor effect of AT13387 was demonstrated in an in vivo model. This study provided experimental evidence for the preclinical value of using AT13387 as an effective antitumor agent in treatment of NPC.