田坂 慶一 大阪大学, 医学部, 講師 (50155058)
NISHIO Yukihiro Medical School, Osaka University Assistant Professor, 医学系研究科, 助手 (30303952)
MORISHIGE Kenichiro Medical School, Osaka University Assistant Professor, 医学系研究科, 助手 (90283788)
OHMICHI Masahide Medical School, Osaka University Assistant Professor, 医学系研究科, 助手 (10283764)
|Budget Amount *help
¥13,300,000 (Direct Cost : ¥13,300,000)
Fiscal Year 1999 : ¥2,800,000 (Direct Cost : ¥2,800,000)
Fiscal Year 1998 : ¥2,400,000 (Direct Cost : ¥2,400,000)
Fiscal Year 1997 : ¥8,100,000 (Direct Cost : ¥8,100,000)
Trophoblast, an important component of mammalian placenta has a unique biological features. Particularly, during the first trimester of pregnancy, trophoblasts start invading into uterine wall as far as uterine spinal arteries. Interestingly, this invasive behavior is strictly regulated so that the invasion would not go beyond uterine vessels. Recently, particular members of integrins have been described to be expressed on trophoblast. Evidence has been accumulated that these integrins play an essential role for the regulation of the invasive behavior described above. It has been shown that two main mechanisms are involved in cell-to-cell and cell-to extracellular matrix (ECM) interactions : interaction via ligand receptor binding, and comunication by soluble growth factors or cytokines such as epidermal growth factor (EGF), interleukin-6 (IL-6), transforming growth factor-beta (TGF-β), or leukemia inhibitory factor (LIF).
In this study, utilizing human BeWo choriocarcinoma cells, we ex
amined whether epidermal growth factor influences integrin expression on the surface of BeWo cells. Among integrin molecules examined by flow cytometry, α2 integrin expression was increased most effectively at 12, 24 and 48 hours after stimulation of 10 nM EGF. This increase concurrently occurred along the increase of human choriogenic gonadotropin (hCG) secretion, which indicates functional differentiation of trophoblasts. In addition, the α2 integrin transcripts were induced in response to EGF as early as 3 hours after addition.
Combined with previous knowledge, we speculated that the increase of α2 integrin play a role in the invasion activity into endometrium. An invasion assay indicated that EGF increased invasion activity of BeWo cells at biological concentration. Antibody against α2 integrin suppressed the invasion activity more effectively on EGF-treated cells than untreated cells, which may indicate that the increase of cell surface α2 integrin may contribute to augmented invasiveness into Matrigel. Furthermore, we examined the effects of EGF on BeWo cell adhesion on collagen and chemokinasis by EGF by adhesion assay and Boyden Chamber assay, respectively. EGF did not alter the adhesion of BeWo cells to collagen matrix. On the other hand, EGF augmented chemokinasis activity of BeWo cells in dose-dependant manner. Noteworthy was that the increase of chemokinasis activity was suppressed by antibody against α2 integrin antibody more effectively when the cells were treated with EGF reimniscently to the invasion assay results. Given these results, we concluded that i) α2 integrin is an inducible molecule by EGF. ii) the increase of α2 integrin by EGF accounts in part for the augmentation of invasiveness of BeWo cells, presumably due to increase of chemokinasis activity.