Increased expression of importin13 in endometriosis and endometrial carcinoma

Abstract

Background: Importin13 (IPO13) is a novel potential marker of corneal epithelial progenitor cells. We investigated the expression and localization of IPO13 in endometrial, endometriotic and endometrial carcinoma tissue.

Material/methods: IPO13 expression in endometrial, endometriotic and endometrial carcinoma tissue was examined by immunohistochemistry, qPCR and Western blot.

Results: Immunohistochemistry studies showed that IPO13 protein was expressed mainly in cytoplasm of glandular epithelial cell and stromal cells. The rate of importin13-positive cells in proliferative phase endometrium was higher (by about 6-fold) than that in secretory endometrium (P<0.05) and the rate of importin13-positive cells in endometriosis and endometrial carcinoma was higher than that in normal secretory phase endometrial tissues (by about 4- and 9-fold, respectively). Immunofluorescence microscopy revealed co-localization of IPO13 with CD34, CD45, c-kit, telomerase, CD90 and CD146. QPCR revealed significantly increased IPO13 mRNA in endometriosis and endometrial carcinoma versus secretory phase endometrium (by about 2- and 10-fold, respectively). Western blot analysis showed that IPO13 protein is enhanced in endometriosis and endometrial carcinoma versus secretory phase endometrium (p<0.05).

Conclusions: These results demonstrate an increased expression of IPO13 in endometriosis and endometrial carcinoma, which could be involved in the pathogenesis of endometriosis and endometrial carcinoma; IPO13 can serve as an endometrial progenitor/stem cell marker.

Figure 1

Representative immunohistochemical staining patterns of IPO13 in human proliferative phase endometrium, secretory phase endometrium, endometriosis and endometrial carcinoma. (A) IPO13-expressing cells in proliferative phase endometrium; ×400 magnification. (B) IPO13-expressing cells in secretory phase endometrium; ×400 magnification. (C) IPO13-expressing cells in endometriosis; ×200 magnification. (D) IPO13-expressing cells in endometrial carcinoma; ×400 magnification.

Figure 2

Distribution of IPO13-positive cells in proliferative phase endometrium, secretory phase endometrium, endometriosis and endometrial carcinoma. (A) Significantly increased number of IPO13-positive cells in endometriosis and endometrial carcinoma vs. secretory phase endometrium. (B) Significantly increased percentage of IPO13-positive cells in the basalis compared to the functionalis layer of proliferative phase endometrium. * p<0.05; error bars, SEM.

Figure 3

Co-localization of IPO13 and CD90, CD34, CD45 in human endometrium. The sections were immunostained with a goat polyclonal IPO13 antibody (red fluorescent secondary antibody) and polyclonal rabbit antibodies (green fluorescent secondary antibody) including anti-CD90, anti-CD34 and anti-CD45. Yellow staining in the merged pictures denotes co-localization of the 2 progenitor cell marker proteins. Blue, DAPI nuclear staining. (A) Putative endometrial progenitor cell displaying co-localization of IPO13 and CD45. (B) Putative endometrial progenitor cell displaying co-localization of IPO13 and CD90. (C) Putative endometrial progenitor cell displaying co-localization of IPO13 and CD34.

Figure 4

Co-localization of IPO13, telomerase, CD146 and c-kit in human endometrium. The sections were immunostained with a goat polyclonal IPO13 antibody (red fluorescent secondary antibody), a mouse monoclonal CD146 antibody (green fluorescent secondary antibody) and polyclonal rabbit antibodies (green fluorescent secondary antibody) including anti-telomerase, anti-telomerase and anti-c-kit. Yellow staining in the merged pictures denotes co-localization of the 2 progenitor cell marker proteins. Blue, DAPI nuclear staining. (A) Putative endometrial progenitor cell displaying co-localization of IPO13 and telomerase. (B) Putative endometrial progenitor cell displaying co-localization of IPO13 and CD146. (C) Putative endometrial progenitor cell displaying co-localization of IPO13 and c-kit.

Figure 5

Quantitative real-time PCR analysis of IPO13 mRNA expression in human endometrium, endometriosis and endometrial carcinoma. Relative increase of IPO13 expression in endometriosis and endometrial carcinoma vs. secretory myometrium, as calculated by the 2^−ΔΔCt method. Error bars, SEM; * p<0.05.

Figure 6

Western blot analysis of IPO13 in human endometrium, endometriosis and endometrial carcinoma. The upper and lower panels show the intensity of IPO13 and β-actin bands, respectively. (A) proliferative endometrium (B) secretory endometrium (C) endometriosis (D) endometrial carcinoma