Immunohistochemical detection of a specific receptor for lipocalin2 (solute carrier family 22 member 17, SLC22A17) and its prognostic significance in endometrial carcinoma

Background

We previously reported the overexpression of lipocalin2 (LCN2), a 25 kDa secretory protein involved in iron-transportation, in endometrial carcinoma and its possible contribution to endometrial carcinogenesis. Recently, a specific receptor for LCN2, solute carrier family 22 member 17 (SLC22A17), was identified. The present study was undertaken to investigate the expression of SLC22A17 in endometrial carcinoma.

Methods

The expression of the SLC22A17 and LCN2 proteins was examined immunohistochemically using 69 cases of endometrial carcinoma and adjacent normal endometrial tissues. Immunoreactivity was evaluated according to the percentage of positive cells and described as a positivity index (PI, full score 100).

Results

The expression of SLC22A17 was negligible in normal endometria, but positive staining for SLC22A17 (PI ≧ 1) was observed in 35 cases of endometrial carcinoma. The PI for SLC22A17 was significantly higher in cases with histological grade 3 (P < 0.0005), advanced FIGO stage (P = 0.002), deep myometrial invasion (P = 0.029), positive lymph-vascular space invasion (P = 0.029), positive intraperitoneal cytology (P = 0.020) and adnexal metastasis (P = 0.029). The expression of SLC22A17 and LCN2 was positively correlated with a significant difference (P = 0.002), and the patients who overexpressed both SLC22A17 and LCN2 showed poorer survival than those without the expression of SLC22A17 or LCN2 (P = 0.002). Moreover, the overexpression of both SLC22A17 and LCN2 was indicated to be an independent prognostic factor by multivariable analysis.

Conclusions

These results suggested that SLC22A17, in cooperation with LCN2, to be involved in the acquisition of aggressive behavior among endometrial carcinoma cells.