Study Of Expression And Clinic Significence Of Smac/DIABLO And XIAP In Nasopharyngeal Carcinoma

Purpose Second mitochondria-derived activator of caspase/directinhibitor of apoptosis-binding protein with low pI (Smac/DIABLO) wasrecently identified as a protein that is released from mitochondria inresponse to apoptotic stimuli and promotes apoptosis by antagonizinginhibitor of apoptosis proteins. However, little is known about theclinical significance of Smac/DIABLO in nasopharyngealcarinoma(NPC). The aim of this investigation is to study the expressionof Smac/DIABLO and XIAP in NPC and the association between them,to discuss status of Smac/DIABLO in pathogenesis of NPC.Methods Real-time PCR was used to detect the expression ofSmac/DIABLO and XIAP in biopsies of 31 NPC and 9 chronicnasopharyngitis to investigate the relationship between the expression ofSmac/DIABLO and XIAP of patients. And immunohistochemical S-Pstaining was used to detect the expression of Smac/DIABLO in biopsiesof 41 NPC and 10 chronic nasopharyngitis to investigate the correlationbetween Smac/DIABLO and clincical feature of NPC patients.Results The results of Real-time PCR: XIAP and Smac/DIABLOmRNA expression was found in all NPCs and chronic nasopharyngitis.Importantly,the relative Smac/DIABLO mRNA expression levels of NPCsignificantly decreased from stageâ… /â…¡to stageâ…¢/â…£.In contrast, mRNA expression levels of XIAP did not significantly change between stageâ… /â…¡to stageâ…¢/â…£. Consequently, the mRNA expression ratio betweenproapoptotic Smac/DIABLO and antiapoptotic XIAP markedly decreasedduring progression from stageâ… /â…¡to stageâ…¢/â…£. The results ofImmunohistochemical S-P staining: The expression of Smac/DIABLOwas lower in NPC compared with the autologous chronic nasopharyngitis.73.2% of NPC expressed Smac/DIABLO, whereas 90% of chronicnasopharyngitis tissues were positive. In stageâ… /â…¡NPC, 81.8% expressedSmac/DIABLO, whereas only 63.2% expressed Smac/DIABLO in stageâ…¢/â…£. Smac/DIABLO expression inversely correlated with the grade ofNPC. The expression of XIAP was higher in NPC compared with theautologous chronic nasopharyngitis. 97.6% of NPC expressed XIAP,whereas 50% of chronic nasopharyngitis tissues were positive. In stageâ… /â…¡NPC, 95.2% expressed XIAP, whereas 100% expressed XIAP instageâ…¢/â…£.Conclusion The present study demonstrates for the first time thatSmac/DIABLO expression was downregulated in NPC whereas XIAPwas upregulated. These results suggest that the expression ofSmac/DIABLO and XIAP might play important roles in the developmentof NPC.