Characterization of tumor suppressive function of P300/CBP-associated factor at frequently deleted region 3p24 in esophageal squamous cell carcinoma.

Deletion of 3p is one of the most frequent genetic alterations in many tumors, including esophageal squamous cell carcinoma (ESCC). In our recent study, deletion of 3p24 was frequently detected in ESCC and one candidate tumor suppressor gene (TSG), p300/CBP-associated factor (PCAF), was identified within the region. In this study, downregulation of PCAF was detected in 23/40 (57.5%) of primary ESCCs and 4/9 (44.4%) of the ESCC cell lines. A further study found that downregulation of PCAF was also associated with hypermethylation of the promoter region of PCAF gene. Methylation-specific PCR found that promoter methylation was detected in 28/40 (70%) of primary ESCCs and 5/9 (55.6%) of ESCC cell lines. In addition, the expression of PCAF could be reactivated in ESCC cell line KYSE510 after demethylation treatment with 5-aza-dC. Functional studies showed that PCAF was able to suppress tumorigenicity of ESCC cells both in vitro and in vivo, including foci formation, colony formation in soft agar and tumor formation in nude mice. Molecular study found that the tumor suppressive mechanism of PCAF was associated with its role in cell cycle arrest at the G1/S checkpoint by the downregulation of CDK2 and upregulation of p21(waf1/Cip1), Smad4, Rb and p27(Kip1). In conclusion, PCAF might be the target TSG responsible for the 3p24 deletion event, which has an important role in the development and progression of ESCC.

Functional polymorphisms in the BRCA1 promoter influence transcription and are associated with decreased risk for breast cancer in Chinese women.

BACKGROUND: The BRCA1 gene is an important breast-cancer susceptibility gene. Promoter polymorphisms can alter the binding affinity of transcription factors, changing transcriptional activity and may affect susceptibility to disease. METHODS AND RESULTS: Using direct sequencing of the BRCA1 promoter region, we identified four polymorphisms c.-2804T-->C (rs799908:T-->C), c.-2265C-->T (rs11655505:C-->T), c.-2004A-->G (rs799906:A-->G) and c.-1896(ACA)(1)-->(ACA)(2) (rs8176071:(ACA)(1)-->(ACA)(2)) present in Hong Kong Chinese. Each polymorphism was studied independently and in combination by functional assays. Although all four variants significantly altered promoter activity, the c.-2265T allele had stronger binding than the C allele, and the most common mutant haplotype, which contains the c.-2265T allele, increased promoter activity by 70%. Risk association first tested in Hong Kong Chinese women with breast cancer and age-matched controls and replicated in a large population-based study of Shanghai Chinese, together totalling >3000 participants, showed that carriers of the c.-2265T allele had a reduced risk for breast cancer (combined odd ratio (OR) = 0.80, 95% CI 0.69 to 0.93; p = 0.003) which was more evident among women aged >or=45 years at first diagnosis of breast cancer and without a family history of breast cancer (combined OR = 0.75, 95% CI 0.61 to 0.91; p = 0.004). The most common haplotype containing the c.-2265T allele also showed significant risk association for women aged >or=45 years without a family history of breast cancer (OR = 0.64, 95% CI 0.46 to 0.89; p = 0.008). CONCLUSION: This comprehensive study of BRCA1 promoter polymorphisms found four variants that altered promoter activity and with the most significant contribution from c.-2265C-->T, which could affect susceptibility to breast cancer in the Chinese population. Its significance in other populations remains to be investigated.

Induction of matrix metalloproteinases by Epstein-Barr virus latent membrane protein 1 isolated from nasopharyngeal carcinoma.

Epstein--Barr virus latent infection is associated with human malignancies including Burkitt's lymphoma, gastric carcinoma and the highly invasive nasopharyngeal carcinoma (NPC). Increased expression of EBV latent membrane protein 1, LMP1, is correlated with tumor progression and metastasis in NPC. LMP1 induces cellular proteins including cytokines and matrix metalloproteinases (e.g., MMP1, MMP2 and MMP9). MMPs are endopeptidases involved in the degradation of extracellular matrix proteins; and their upregulation in cancer implicates their potential role in tumor metastasis. In light of the role of LMP1 in cytokine dysregulation and the fact that MMPs are regulated by cytokines, we examined whether LMP1 promotes NPC metastasis via the induction of MMPs. To delineate the oncogenic role of LMP1 in NPC, we first investigated the induction of MMP1, MMP2, MMP3 and MMP9 in LMP1-positive NPC tumor samples (n=15) by quantitative RT-PCR. We showed a significant induction of MMP1 and MMP3 transcripts in the EBV LMP1-positive NPC tissues, compared with biopsies obtained from the adjacent non-tumor tissues. To investigate the role of LMP1 in MMP expression in NPC, we cloned the LMP1 gene from NPC samples and transiently expressed it in MRC5 cells (human lung fibroblasts). Following transfection, a time-dependent elevation of endogenous MMP3 expression was found in the LMP1-transfectants by quantitative RT-PCR and Western analysis. Taken together, we observed that MMP3 is upregulated in LMP1-positive NPC tumors and LMP1-expression in fibroblasts is associated with MMP3 and cytokine expression. Our results suggest that LMP1 may contribute to invasiveness of NPC cells via the expression of MMP3 in fibroblasts.

Sustained elevation of Epstein-Barr virus antibody levels preceding clinical onset of nasopharyngeal carcinoma.

We have monitored Epstein-Barr virus (EBV) IgA antibody levels of 39 nasopharyngeal carcinoma (NPC) cases for up to 15 years before clinical onset of NPC, and assessed preclinical serologic status of another 68 cases. Our results identify a serologic window preceding diagnosis when antibody levels are raised and sustained. This window can persist for as long as 10 years, with a mean duration estimated to as 37+/-28 months. Ninety-seven of these 107 NPC cases exhibited such a window. Cases that did not may reflect individual antibody response to EBV. Serologic screening at enrollment identified those cases who had already entered the window and became clinically manifested earlier (median=28 months) than those who entered the window after enrollment (median=90 months). The former account for 19 of 21 cases diagnosed within 2 years of screening. Nasopharyngeal carcinoma risk levels among seropositive subjects were also highest during this period. Both prediction rates and risk levels declined thereafter; cases detected at later times were composed of increasing proportions of individuals who entered the serological window after screening. Our findings establish EBV antibody as an early marker of NPC and suggest that repeated screening to monitor cases as they enter this window has considerable predictive value, with practical consequences for cancer treatment.

Chemotherapy as an adjunct to radiotherapy in locally advanced nasopharyngeal carcinoma.

BACKGROUND: A previous meta-analysis investigated the role of chemotherapy in head and neck locally advanced carcinoma. This work had not been performed on nasopharyngeal carcinoma. OBJECTIVES: The aim of the project was to study the effect of adding chemotherapy to radiotherapy on overall survival (OS) and event-free survival (EFS) in patients with nasopharyngeal carcinoma. SEARCH STRATEGY: We searched MEDLINE (1966 to October 2003), EMBASE (1980 to October 2003) and the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 3, 2003) and trial registers. Handsearches of meeting abstracts, references in review articles and of the Chinese medical literature were carried out. Experts and pharmaceutical companies were asked to identify trials. SELECTION CRITERIA: Randomised trials comparing chemotherapy plus radiotherapy to radiotherapy alone in locally advanced nasopharyngeal carcinoma were included. DATA COLLECTION AND ANALYSIS: The meta-analysis was based on updated individual patient data. The log rank test, stratified by trial, was used for comparisons and the hazard ratios (HR) of death and failure (loco-regional/distant failure or death) were calculated. MAIN RESULTS: Eight trials with 1753 patients were included. One trial with a 2 x 2 design was counted twice in the analysis. The analysis was performed including 11 comparisons based on 1975 patients. The median follow up was six years. The pooled hazard ratio of death was 0.82 (95% confidence interval (CI) 0.71 to 0.95; P = 0.006) corresponding to an absolute survival benefit of 6% at five years from chemotherapy (from 56% to 62%). The pooled hazard ratio of tumour failure or death was 0.76 (95% CI 0.67 to 0.86; P < 0.00001) corresponding to an absolute event-free survival benefit of 10% at five years from chemotherapy (from 42% to 52%). A significant interaction was observed between chemotherapy timings and overall survival (P = 0.005), explaining the heterogeneity observed in the treatment effect (P = 0.03) with the highest benefit from concomitant chemotherapy. AUTHORS' CONCLUSIONS: Chemotherapy led to a small but significant benefit for overall survival and event-free survival. This benefit was essentially observed when chemotherapy was administered concomitantly with radiotherapy.

Staging of nasopharyngeal carcinoma: suggestions for improving the current UICC/AJCC Staging System.

AIMS: To evaluate the current UICC/AJCC Staging System for nasopharyngeal carcinoma and to search for ways of improving the system. MATERIALS AND METHODS: This is a retrospective analysis of 2687 consecutive patients treated in five public centres in Hong Kong during the period 1996-2000. All patients were staged by computed tomography, magnetic resonance imaging, or both. The prognostic significance of the current stage assignment on various aspects of tumour control was evaluated. RESULTS: T-category, N-category and stage-group were all significant prognostic factors for major end points (P < 0.01). However, the distinction of prognosis between Stage I and II was insignificant (5-year cancer-specific survival being 92% vs 95%; P = 0.13). Multivariate analyses (corrected for age and sex) revealed lack of significance between T2a and T1 in hazards of local and distant failures, N3a and N2 in distant failure and subgroups of T1-2N0 in cancer-specific deaths. Corresponding down-staging of T2a to T1, N3a to N2, and subgroup T2N0 to stage I, resulted in more even and orderly increase in the hazard ratio of cancer-specific deaths (from 1 for stage I to 1.98 for II, 3.5 for III, 6.08 for IVA and 8.62 for IVB), better hazard consistency among subgroups of the same stage and more balanced stage distribution. CONCLUSIONS: The current UICC/AJCC Staging System could be further improved by the modifications suggested; validation of the current proposal by external data is urgently awaited.