Department of Pathology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi, 755-8505, Japan.
Department of Basic Laboratory Sciences, Yamaguchi University Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi, 755-8505, Japan.
J Cancer Res Clin Oncol. 2019 Feb;145(2):363-371. doi: 10.1007/s00432-018-2797-z. Epub 2018 Nov 21.
Glioblastoma is still intractable despite the progress in therapies, and the intractability is attributable to a minor population of stem-like tumor cells. As a niche harboring quiescent stem-like tumor cells with potentially high tumorigenicity, we have specified an area around large ischemic necrosis, termed 'peri-necrotic niche', in glioblastoma. In this study, the behavior of tumor cells inside and outside the peri-necrotic niche was analyzed to find out molecules responsible for reactivation of quiescent stem-like tumor cells to proliferate outside the niche.
Expression of Ki-67 and GINS complex composed of SLD5, PSF1, PSF2 and PSF3 was analyzed by immunohistochemistry in human glioblastoma tissue samples. Proliferation assays, immunoblotting and siRNA experiments were performed using a glioblastoma cell line.
Immunohistochemical analysis revealed quiescent and proliferative phenotypes of tumor cells inside and outside the niche, respectively, and the proliferation was spatially correlated with the expression of GINS components in tumor cells. To mimic the tissue microenvironment inside versus outside the niche, glioblastoma cells were cultured under hypoxic versus normoxic conditions, or without versus with serum. Quiescence and proliferation of tumor cells were reversibly determined by the microenvironment inside and outside the niche, respectively, and proliferative activities paralleled the expression levels of GINS components. Furthermore, the reactivation of proliferation after reoxygenation or serum replenishment was suppressed in quiescent tumor cells with PSF1 knockdown.
These findings indicate the essential role of GINS complex in the switch between quiescence and proliferation of tumor cells inside and outside the peri-necrotic niche.
尽管在治疗方面取得了进展，但胶质母细胞瘤仍然难以治疗，其难以治疗的原因是存在一小部分具有干细胞样特征的肿瘤细胞。作为一个含有静止的干细胞样肿瘤细胞的小生境，这些细胞具有潜在的高致瘤性，我们将胶质瘤中围绕大片缺血性坏死的区域称为“坏死周小生境”。在这项研究中，分析了坏死周小生境内外肿瘤细胞的行为，以找出负责使静止的干细胞样肿瘤细胞重新激活并在小生境外增殖的分子。
通过免疫组织化学分析人类胶质母细胞瘤组织样本中 Ki-67 和由 SLD5、PSF1、PSF2 和 PSF3 组成的 GINS 复合物的表达。使用胶质母细胞瘤细胞系进行增殖测定、免疫印迹和 siRNA 实验。
免疫组织化学分析显示，小生境内外肿瘤细胞分别呈现静止和增殖表型，并且增殖与肿瘤细胞中 GINS 成分的表达呈空间相关。为了模拟小生境内外的组织微环境，将胶质母细胞瘤细胞在低氧与常氧、或无血清与含血清条件下培养。肿瘤细胞的静止和增殖分别由小生境内外的微环境决定，增殖活性与 GINS 成分的表达水平平行。此外，用 PSF1 敲低使静止肿瘤细胞的再氧合或血清补充后的增殖再激活受到抑制。
这些发现表明 GINS 复合物在坏死周小生境内外肿瘤细胞的静止和增殖之间的转换中起关键作用。
