Comparison of paired box genes 8 and 2 expression in epithelium tissues and the related tumors

Objective To explore the expressional differences between paired box genes 2(Pax2) and 8 (Pax8) protein in different kinds of epitheliums and tumors, and to investigate the clinicopathologic significance. Methods Expression levels of Pax2 and Pax8 protein were detected in 75 cases of different human epithelium tissues and 255 cases of different tumors on tissue microarray by immunohistochemistry. Results Pax2 and Pax8 selectively expressed in different tissues. The positive rates of Pax8 protein expressed in the normal epithelium of the thyroid, urinary system and female reproductive system were 100% (2/2), 60.0% (3/5) and 76.9% (10/13), respectively. The positive rates of Pax2 expressed in the epithelium tissues of urinary system and the female reproductive system were 40.0% (2/5) and 38.5% (5/13) respectively. However, the expression of Pax2 protein was not detected in the normal thyroid epithelium. The positive rate of Pax8 protein expressing in the epithelium of reproductive system was significantly higher than that of Pax2 protein (P<0.05). The tumors derived from different tissues also expressed different levels of protein Pax2 and Pax8. The positive rates of Pax8 in renal cell carcinoma, thyroid carcinoma and endometrial adenocarcinoma were 65.2% (15/23), 66.7% (10/15) and 80.0% (4/5), respectively. The positive rates of Pax2 in renal cell carcinoma, thyroid carcinoma and endometrial adenocarcinoma were 34.8% (8/23), 13.3% (2/15) and 20.0% (1/5), respectively. The positive rates of Pax8 protein expressed in renal cell carcinoma, thyroid carcinoma and endometrial adenocarcinoma were significantly higher than those of Pax2 protein (P<0.05). The positive rates of Pax8 in ovarian serous carcinoma, endometrial carcinoma and clear cell carcinoma were 92.9% (26/28), 81.8% (9/11) and 82.4% (14/17), respectively. The positive rates of Pax2 in ovarian serous carcinoma, endometrial carcinoma and clear cell carcinoma were 28.6% (8/28), 9.1% (1/11) and 17.6% (3/17), respectively. The positive rates of Pax8 protein expressed in ovarian serous carcinoma, endometrial carcinoma and clear cell carcinomawere significantly higher than those of Pax2 protein (P<0.05). Conclusions Pax2 and Pax8 are specifically expressed in female reproductive system and uritany system. However, the positive expression of Pax8 is superior to that of Pax2. The combined expression of Pax8 and Pax2 can be used in the differential diagnosis of epithelial tumors derived from different origins. Key words: Pax8; Pax2; Epithelium; Neoplasms; Immunohistochemistry; Tissue microarray