Differential expression of osteoblast-specific factor 2 and polymeric immunoglobulin receptor genes in nasopharyngeal carcinoma

Background. The molecular mechanisms leading to development of nasopharyngeal carcinoma (NPC) are not well understood. To delineate the features of NPC, we tried to identify unique expression of cellular genes in the tumor biopsy specimens. Methods and Results. By use of a combination of differential display and cDNA microarray analysis, we found two genes, 3E5 and 4A5, to show unique expression in the NPC biopsy specimens compared with nontumor nasopharyngeal tissues. Expression of 3E5, the osteoblast-specific factor-2 (OSF-2) gene, was detected at significantly higher levels in NPC biopsy specimens than that in control tissues, a finding confirmed using real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). A correlation between expression of OSF-2 and its regulatory cytokine transforming growth factor-β was observed in nontumor tissues but not in NPC biopsy specimens. On the other hand, expression of 4A5, whose sequences represent the 3′ untranslated region of the polymeric immunoglobulin receptor (pIgR) gene, was detected rarely in NPC specimens but frequently in nontumor controls. The expression of pIgR in normal epithelial cells, but not in NPC tumor cells, was verified by RT-PCR and immunohistochemical staining. Conclusions. NPC shows significant upregulation of OSF-2 and downregulation of pIgR. Expression of OSF-2 is likely to play a role in the pathogenesis of NPC. In addition, expression of OSF-2 and pIgR is disassociated with the expression of their regulatory cytokines in NPC biopsy specimens, suggesting that the tumors may have altered responses to certain cytokines.