Modern medical ethics adopts the model of ethical analysis based on principles which contain the characteristics of clarity,definitude and succinctness.To some extent,this model of ethical analysis accommodates pluralism and avoids relativism.However,in the particular decision-making of medical ethics,there may be conflicts among the different moral principles,which cause difficult moral problems.This article tries to rank and demonstrate the order of four basic principles in medical ethics in order to provide a specific thought for resolving difficult moral problems caused by conflicting principles.

Objective To detect methylation of spleen tyrosine kinase (SYK)gene promoter region in nasopharyngeal carcino-ma,and to explore relationship between carcinogenesis of nasopharyngeal carcinoma and methylation of SYK gene promoter region.Methods A total of 52 patients with nasopharyngeal carcinoma and 26 patients with chronic rhinitis from Baoan People’s Hospital of Shenzhen Hospital of Peking University were enrolled in this study between February 2012 and August 2014.All cases were diagnosed by pathological examination.Methylation specific-polymerase chain reaction assay was per-formed to detect methylation status of SYK gene promoter region,the rate of methylation was compared for patients with nasopharyngeal carcinoma and patients with chronic rhinitis.Results The methylation of promoter region of SYK gene was detected for 11 biopsy samples among 52 nasopharyngeal carcinoma patients,the methylation frequency was 21.2% in naso-pharyngeal carcinoma biopsy samples,while methylation was not found in 26 chronic rhinitis biopsy samples.Conclusion Low methylation of promoter region of SYK gene was found in nasopharyngeal carcinoma.It suggests that methylation of SYK gene promoter region may contribute to carcinogenesis of nasopharyngeal carcinoma.