Study Of Protein Expression And Methylation Of P16in Nasopharyngeal Carcinoma

Objective To study the expression of p16in nasopharyngeal carcinoma (NPC) andnormal mucous membrane of nasopharynx(NMMN), and investigate the relationshipamong methylation of p16, mRNA expression and differentiation in NPC.Methods48paraffin-embedded tissue specimens of NPC were confirmed by twopathological doctors and16cases of NMMN were served as the normal control in thestudy; Firstly, study the role of p16protein in the occurrence and development ofNPC by detecting the expression of p16in NPC and NMMN withimmunohistochemistry SP method and analyzing correlation between expression ofp16and clinicopathological features of NPC with SPSS statistical software. Afterextracting DNA and RNA from biopsy specimens of NPC (4cases) and NMMN (2cases), analyze the relationship between methylation of p16gene and differentiationand mRNA expression of NPC by detecting the promoter methylation of p16withMethylation-specific PCR (MSP) and detecting the mRNA expression with RT-PCR..Results1.The loss ratio of p16expression were70.8%(34/48) in NPC and37.5%(6/16) in NMMN; the loss ratio of p16expression in NPC were significantly higherthan that in NMMN (P＜0.05). The loss ratio of p16expression were75.0%(30/40)in poorly differentiated NPC and50.0%(4/8)in moderately differentiated NPC, andthe difference were significant(P＜0.05).2. The expression of p16were related with clinical stage, lymphatic metastasis,distant metastasis and recurrence of NPC (P＜0.05), but without relationship to ageand gender (P＞0.05).3. The expression of unmethylated amplified products from MSP primers was higherthan methylated products in2cases of NMMN, which indicated that all the pomoters were unmethylated(UM)with the highest mRNA expression; Both unmethylated andmethylated amplified products from MSP primers were expressed in2cases ofmoderately differentiated NPC, which indicated that the promoters were partlymethylated(PM)with medium mRNA expression. The expression of methylatedamplified products from MSP primers was higher than unmethylated products in2cases of poorly differentiated NPC, which indicated that promoters were totallymethylated(TM)with the lowest or loss of mRNA expression.Conclusion1. The loss of p16expression in NPC was obviously higher than that inNMMN; and p16expression is negative related to clinical stage, easily lymphaticmetastasis, distant metastasis, differentiation degree and recurrence of NPC.2. Loss or down-regulation of p16expression in NPC was due to its promoterhypermethylation.