Therefore, a number of further studies with large sample sizes are needed to address this issue. Several limitations might be included in this study. Since most of the included studies have conducted on Asians and a few on Caucasians, the results must be interpreted with caution. Further studies concerning populations in other areas such as African and American are required to diminish the ethnic variation-produced biases. Additionally, MK5108 mouse a possible publication bias might have been introduced as only published studies written in English and Chinese as well as French that could be searched from Medline database were included. Notably, we did
not use the funnel plots and Egger’s linear regression test  for assessment of any possible publication biases because of the limited number of the included studies. Moreover, many factors may affect the results the funnel plots, leading to a misunderstanding of the publication biases [34, 35]. However, the fail-safe numbers failed to indicate evident publication biases. In this study, the
sample sizes of several studies in the meta-analyses are rather small, and, the pooled analyses were based upon a thousand cases and a thousand controls, this website which are under power to give a confirmed conclusion. Only two studies include three hundred cases and rest studies included less than one hundred cases. Authors need more cautions about their results. Furthermore, the controls of several studies were hospital-based normal individuals or patients with other Selleck TPCA-1 diseases. eltoprazine In addition, whether
the NPC and control groups were from the same socio-economic status or the same geographic area have not been clearly stated in some of the original papers. Hence, any selection biases might exist. Therefore, a number of further investigations regarding GSTM1 and GSTT1 polymorphisms and NPC risk are required. In conclusion, the data of the present meta-analyses indicate GSTM1 polymorphism as a risk factor for NPC and failed to show a significant association of GSTT1 polymorphism with NPC risk. Acknowledgements This work was supported by no funds. References 1. Lin CL, Lo WF, Lee TH, Ren Y, Hwang SL, Cheng YF, Chen CL, Chang YS, Lee SP, Rickinson AB, Tam PK: Immunization with Epstein-Barr Virus (EBV) peptide-pulsed dendritic cells induces functional CD8+ T-cell immunity and may lead to tumor regression in patients with EBV-positive nasopharyngeal carcinoma. Cancer Res 2002, 62: 6952–6958.PubMed 2. O’Neil JD, Owen TJ, Wood VH, Date KL, Valentine R, Chukwuma MB, Arrand JR, Dawson CW, Young LS: Epstein-Barr virus-encoded EBNA1 modulates the AP-1 transcription factor pathway in nasopharyngeal carcinoma cells and enhances angiogenesis in vitro. J Gen Virol 2008, 89: 2833–2842.