Abstract:

Objective To establish progestin-resistant models of human endometrial carcinoma xenografts, and explore the role of epidermal growth factor receptor (EGFR) signaling pathway in progestin resistance of human endometrial carcinoma xenografts. Methods Thirty-six nude mice were subcutaneously injected with human endometrial carcinoma progestinsensitive Ishikawa cells (n=18) or progestin-insensitive Ishikawa-pLWERNL cells (n=18), and human endometrial carcinoma xenografts were formed. Then, both nude mice treated with Ishikawa cells and Ishikawa-pLWERNL cells were divided into three groups, respectively (n=6), and were managed with medroxyprogesterone acetate (MPA)(MPA group), gefitinib (gefitinib group) and normal saline (control group), respectively. After treatment, wet weight of xenografts was recorded, and the expression of EGFR, progesterone receptor B (PR-B), ERK1/2, p-ERK1/2, AKT and p-AKT protein in xenograft tissues was detected by Western blotting. Results In nude mice treated with Ishikawa cells, the wet weight of xenografts in MPA group and gefitinib group was 43.0% and 31.5% lower than that in control group, respectively (P<0.05). In nude mice treated with Ishikawa-pLWERNL cells, the wet weight of xenografts in gefitinib group and MPA group was 35.7% and 2.9% lower than that in control group, respectively (P<0.05 and P>0.05). The expression of EGFR protein in xenograft tissues treated with Ishikawa-pLWERNL cells was significantly higher than that in xenograft tissues treated with Ishikawa cells (P<0.05), while that was opposite for the expression of PR-B protein （P=0.000）. In xenograft tissues treated with Ishikawa cells, the expression of PR-B protein in MPA group was significantly lower than that in control group （P<0.01）, while there was no significant difference between gefitinib group and control group （P>0.05）. In xenograft tissues treated with Ishikawa-pLWERNL cells, there was no significant difference in the expression of PR-B protein among groups （P>0.05）. In xenograft tissues treated with Ishikawa cells, the expression of p-ERK1/2 and p-AKT protein in gefitinib group was significantly lower than that in control group and MPA group (P<0.05). In xenograft tissues treated with Ishikawa-pLWERNL cells, the expression of p-ERK1/2 and p-AKT protein in gefitinib group was significantly lower than that in control group (P<0.05), and the expression of p-ERK1/2 and p-AKT protein in MPA group was significantly higher than that in control group (P<0.01）. Conclusion The over-expressed EGFR protein can downregulate the expression of PR-B protein in Ishikawa-pLWERNL xenografts, which results in insensitivity to MPA. Gefitinib, the EGFR tyrosine kinase inhibitors, can effectively inhibit the expression of p-ERK1/2 and p-AKT protein, especially in  progestin-insensitive Ishikawa-pLWERNL xenografts.

Key words: human endometrial carcinoma xenografts, epidermal growth factor receptor signaling pathway, progesterone receptor B;progestin resistance, gefitinib