Expression regulation of LRP16 gene by 17¦Âª²estradiol and its significance in human endometrial cancer Ishikawa cells

    MENG Yuanª²Guang1, HAN Weiª²Dong2, HUANG Ke1, WU Zhiª²Qiang2, ZHAO Yaª²Li2, MU Yiª²Ming3, SONG Lei1

    1Department of Obstetrics and Gynecology, 2Department of Moleª²cular Biology, Institute of Basic Medicine, 3Department of Endocrinology, Chinese PLA General Hospital, Beijing 100853, China

    ¡¾Abstract¡¿ AIM: To explore the regulation of LRP16 gene expression by 17¦Âª²estradiol (E2) in ER¦Áª²positive human endoª²metrial cancer Ishikawa cell line, and to investigate the effect of LRP16 overexpression on the proliferative potential and invasive growth of Ishikawa and the possible molecular mechanism. METHODS: The LRP16 mRNA level in Ishiwaka cells was determined by Northern blot analysis. The relative luciferase activity was measured using Dualª²luciferase reporter assay system. The effect of LRP16 overexpression on Ishiwaka proliferation was examined by the Trypan Blue exclusion method. The invasiveness of Ishikawa was evaluated by using the Matrigelª²coated Transwell assay. The protein levels in Ishikawa were determined by Western blot analysis. In addition, the Eª²cadherin mRNA level was also examined by Nothern blot. RESULTS: 17¦Âª²E2 induced an increase in LRP16 mRNA levels in Ishikawa cells, whereas, its pure antagonist, ICI 182 780 reduced the LRP16 mRNA level. Ectopic ER¦Á transfection in Ishikawa increased the expression of LRP16 gene. The significant increase of the relative luciferase activity in Ishikawa cells cotransfected by pGL3ª²S5 and ER¦Á plasmids was observed compared with that in the control cells transfected by pGL3ª²S5 alone. Stimulative effect of LRP16 overexpression on the proliferation of Ishikawa cells was not observed in this study. Thirtyª²persent increase of the invasive capacity was observed in Ishikawa cells with LRP16 overexpression. The mRNA and protein levels of Eª²cadherin gene was nearly 3ª²fold decreased in Ishikawa cells with the overexpression of LRP16, while the protein levels of MMP2, MMP9 and CD44 were not different between LRP16ª²overexpressed Ishikawa cells and the control cells. CONCLUSION: Estrogen upª²regulated the LRP16 mRNA level by activation of ER¦Á and the LRP16 expression was dependent on the estrogen in ER¦Áª²positive endometrial cancer cells. Upª²regulation of LRP16 did not promote the proliferation of the endometrial cancer cells, but increased its invasive potential possibly by suppressing the Eª²cadherin expression level. ......