Expression of interleukin-1 (IL-1) ligands system in the most common endometriosis-associated ovarian cancer subtypes

Abstract

Objectives: Endometrioid carcinoma of the ovary is one of the most types of epithelial ovarian cancer associated to endometrioisis. Endometrioid tumors as well as endometriotic implants are characterized by the presence of epithelial cells, stromal cells, or a combination of booth, that resemble the endometrial cells, suggesting a possible endometrial origin of these tumors. Pro-inflammatory cytokines, including interleukin-1 (IL-1) have been reported to be involved in both endometriosis and ovarian carcinogenesis. The major objective of this study was to determine the level expression of IL-1 ligands system (IL-1alpha, IL-1beta and IL-1RA) in the most common subtypes of ovarian cancer cells compared to endometrial cells.

Methods: We used primary endometrial cells, endometrial cell line RL-952 and different subtypes of epithelial ovarian cancer cell lines including TOV-112D (endometrioid), TOV-21G (clear cell) and OV-90 (serous). Immunofluorescence and real-time PCR analysis were used respectively for detecting IL-1 ligands at the levels of cell-associated protein and mRNA. Soluble IL-1 ligands were analyzed by ELISA.

Results: We demonstrated that IL-1 ligands were expressed by all endometriosis-associated ovarian cancer subtypes and endometrial cells. In contrast to other cancer ovarian cells, endometrioid cells exhibit a specific decrease of cell-associated IL-1RA expression and its soluble secretion.

Conclusion: Endometrioid ovarian cancer exhibits an alteration in the expression of IL-1RA, a key protector against tumorogenic effects of IL-1. This alteration evokes the same alteration observed in endometriotic cells in previous studies. This suggests a possible link between the endometrium, the tissue ectopic endometriosis and endometrioid ovarian cancer.

Figure 1

Expression of IL-1α by immunofluorescence. Expression of IL-1α protein in primary endometrial cells (A and B), endometrial cell line RL-952 (C and D) and the different subtypes of epithelial ovarian cancer cell lines TOV-112D (endometrioid), TOV-21G (clear cell) and OV-90 (serous) (E and F; G and H; I and J; respectively). Note the marked intensity of IL-1α staining in both endometrial cells (B and D) and ovarian cancer cells (F, H and J). No immunofluorescence was observed in negative controls for endometrial cells (A and C) and ovarian cancer cells (E, G, and I) in the absence of primary antibody (objective × 100).

Figure 2

Graphical illustration of IL-1α expression. IL-1α expression scores in endometrial cells (EC) and epithelial ovarian cancer cells lines (mean ± SD). A: IL-1α was immunostained and immunofluorescence was scored using iCys imaging cytometer. B: expression of IL-1α in EC and epithelial ovarian cancer cells lines was detected by real time PCR using primers specific for IL-1α and β-actin.

Figure 3

IL-1RA expression by immunofluorescence. Expression of IL-1RA protein in primary endometrial cells (A and B), endometrial cell line RL-952 (C and D) and the different subtypes of epithelial ovarian cancer cell lines TOV-112D (endometrioid), TOV-21G (clear cell) and OV-90 (serous) (E and F; G and H; I and J; respectively). Note the marked intensity of IL-1RA staining in both endometrial cells (B and D) and ovarian cancer cells (F, H and J). No immunofluorescence was observed in negative controls for endometrial cells (A and C) and ovarian cancer cells (E, G, and I) in the absence of primary antibody (objective × 100).

Figure 4

Graphical illustration of IL-1RA expression. IL-1RA expression scores in endometrial cells (EC) and epithelial ovarian cancer cells lines (mean ± SD). A: IL-1RA was immunostained and immunofluorescence was scored using iCys imaging cytometer. B: expression of IL-1RA in EC and epithelial ovarian cancer cells lines was detected by real time PCR using primers specific for IL-1RA and β-actin.

Figure 5

Graphical illustration of IL-1β. IL-1β gene expression in EC and epithelial ovarian cancer cells lines by real time PCR using primers specific for IL-1β and β actin.