Lewis y antigen promotes the proliferation of ovarian carcinoma-derived RMG-I cells through the PI3K/Akt signaling pathway
Juanjuan Liu
1
Bei Lin
1
Yingying Hao
1
Yue Qi
1
Liancheng Zhu
1
Feifei Li
1
Dawo Liu
1
Jianping Cong
1
Shulan Zhang
1
Masao Iwamori
0
0
Department of Biochemistry, Faculty of Science and Technology, Kinki University
,
3-4-1 Kowakae, Higashiosaka, Osaka, 577-8502
,
Japan
1
Department of Obstetrics and Gynecology, China Medical University Shengjing, Hospital
,
36 Sanhao Street, Heping, Shenyang, 110004
,
PR China
Background: Lewis y antigen is difucosylated oligosaccharide and is carried by glycoconjugates at cell surface. Elevated expression of Lewis y has been found in 75% of ovarian tumor, and the high expression level is correlated to the tumor's pathological staging and prognosis. This study was to investigate the effect and the possible mechanism of Lewis y on the proliferation of human ovarian cancer cells. Methods: We constructed a plasmid encoding 1,2-fucosyltransferase (1,2-FT) gene and then transfected it into ovarian carcinoma-derived RMG-I cells with lowest Lewis y antigen expression level. Effect of Lewis y on cell proliferation was assessed after transfection. Changes in cell survival and signal transduction were evaluated after -L-fucosidase, anti-Lewis y antibody and phosphatidylinositol 3-kinase (PI3K) inhibitor treatment. Results: Our results showed that the levels of 1,2-FT gene and Lewis y increased significantly after transfection. The cell proliferation of ovarian carcinoma-derived RMG-I cells sped up as the Lewis y antigen was increased. Both of -L-fucosidase and anti-Lewis y antibody inhibited the cell proliferation. The phosphorylation level of Akt was apparently elevated in Lewis y-overexpressing cells and the inhibitor of PI3K, LY294002, dramatically inhibited the growth of Lewis yoverexpressing cells. In addition, the phosphorylation intensity and difference in phosphorylation intensity between cells with different expression of 1,2-FT were attenuated significantly by the monoantibody to Lewis y and by the PI3K inhibitor LY294002. Conclusions: Increased expression of Lewis y antigen plays an important role in promoting cell proliferation through activating PI3K/Akt signaling pathway in ovarian carcinoma-derived RMG-I cells. Inhibition of Lewis y expression may provide a new therapeutic approach for Lewis y positive ovarian cancer.
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Background
Lewis y antigen is carried by glycoconjugates
(glycoproteins and glycolipids) at cell surface. It is an
oligosaccharide with two fucoses, and its chemical structure is Fuc1
2Gal1 4 [Fuc1 3]GlcNAc1 R, belonging to
the A, B, H, Lewis blood group antigens family with
specific fucosylation of the terminal end of carbohydrate
structure catalyzed by the 1,2-fucosyltransferase [1,2].
The expression of Lewis y antigen primarily occurs during
the embryogenesis period. Under physiologic conditions,
its expression in adults is limited on the surface of
granulocytes and epithelium [3]. However, elevated expression
of Lewis y has been found in 70-90% of the human
carcinomas of epithelial cell origin, including breast, ovary,
prostate, colon cancers, and the high expression level is
correlated to the tumor's pathological staging and
prognosis [4-6]. It has been reported that the Lewis y antigen
was expressed on a number of different molecular carriers,
including 2 major ovarian cancer antigens (CA125 and
MUC-1), suggesting the high incidence of Lewis y in
ovarian cancer [7].
We have established the stable ovarian cancer cell line
with high expression of Lewis y, RMG-I-H, through gene
transfection technique to introduce the gene of human
1,2-fucosyltransferase (1,2-FT) into the ovarian cancer
cell line RMG-I in our previous works. We found that the
RMG-I-H cells become highly tolerant to the anti-tumor
drugs, 5-fluorouracil, carboplatin [8,9]. It suggested that
the Lewis y antigen possessed the function of boosting the
survival ability of ovarian cancer cells.
Activation of the PI3K pathway supports survival and
proliferation of multiple cell lineages [10]. PI3K activation
results in the localized increase of phosphorylated lipid
second messengers at the plasma membrane. Key
signaling intermediates are then recruited to the
phosphorylated lipids via specialized lipid-binding domains,
pleckstrin homology (PH) domains, and are themselves
activated to initiate further signaling events [11,12]. One
key effector molecule that is activated in this manner is the
serine/threonine kinase Akt, which, when localized to
products of PI3K activation, is able to phosphorylate
multiple downstream substrates that mediate cell growth,
survival, and metabolism [13-15]. Studies found that soluble
Lewis y antigen (4A11) or its glucose analog, H-2 g, effect
angiogenesis by inducing VEGF expression and signaling
through PI3K pathway in the angiogenesis-rich
rheumatoid arthritis [16].
Here we report that the cell proliferation of ovarian cancer
cell line RMG-I sped up as the Lewis y antigen was
increased. The phosphorylation level of Akt was
apparently elevated (...truncated)