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[Protein microarray analysis on changes in protein phosphorylation in recurrent nasopharyngeal carcinoma].

OBJECTIVE
To compare the differential phosphorylation level of proteins between relapsed nasopharyngeal carcinoma (rNPC) and primary nasopharyngeal carcinoma (pNPC).


METHODS
Total protein was extracted from 4 pNPC tissue and 4 rNPC tissue samples from January 2003 to September 2005. Then it was analyzed by antibody microarray with 656 antibodies. The differential phosphorylation level of proteins was screened and clustering analysis conducted. The phosphorylation status of the protein sites and its functional pathways were analyzed via an online database of PhosphoSite Plus. The protein expressions were detected by immunohistochemistry.


RESULTS
Relapsed and primary nasopharyngeal carcinomas had differential phosphorylation level of proteins. And 6 differentially expressed proteins were identified. The phosphorylation levels of KIT, ATP1A1, Synapsin, SEK1 and histone H2AX were up-regulated in rNPC (P = 0.007 - 0.048) while c-Jun was down-regulated (P = 0.030). The expression of P-H2AX in rNPC was significantly higher than that in pNPC [0.390 (0.175) vs 0.290 (0.155)], but p-c-Jun was significantly lower in rNPC than that in pNPC [0.625 (0.145) vs 0.725 (0.178)] (both P < 0.05). Among them, the changes in the phosphorylation levels of c-Jun, histone H2AX, SEK1 and KIT might play important roles in the relapse of NPC through improving DNA damage repair ability, inhibiting apoptosis and promoting tumorigenesis.


CONCLUSION
The changes of protein phosphorylation may help to explain the recurrent mechanisms of NPC and provide new therapeutic anti-recurrence targets.