干细胞 肿瘤干细胞 胃癌 胃癌干细胞 Hedgehog 信号通路 Wnt/β-catenin 信号通路 SHH GLI1 Wnt2 β-catenin 克隆球细胞 免疫组化 阳性细胞 干细胞图片文章 stem cel s tumor stem cel s gastric cancer gastric cancer stem cel s Hedgehog signal pathway Wnt/β-catenin signal pathway SHH GLI1 Wnt2 β-catenin clone cel s immunohistochemistry positive cel s stem cel photographs-containing paper