Pusey Michelle A, Pace Karma, Fascelli Michele, Linser Paul J, Steindler Dennis A, Galileo Deni S
Department of Biological Sciences, University of Delaware, Newark, DE, USA.
Whitney Laboratory, University of Florida, St. Augustine, FL, USA.
Int J Dev Neurosci. 2019 Nov;78:49-64. doi: 10.1016/j.ijdevneu.2019.08.001. Epub 2019 Aug 14.
Adult human neural progenitor and stem cells have been implicated as a potential source of brain cancer causing cells, but specific events that might cause cells to progress towards a transformed phenotype remain unclear. The L1CAM (L1) cell adhesion/recognition molecule is expressed abnormally by human glioma cancer cells and is released as a large extracellular ectodomain fragment, which stimulates cell motility and proliferation. This study investigates the effects of ectopic overexpression of the L1 long ectodomain (L1LE; ˜180 kDa) on the motility, proliferation, and differentiation of human neural progenitor cells (HNPs). L1LE was ectopically expressed in HNPs using a lentiviral vector. Surprisingly, overexpression of L1LE resulted in reduced HNP motility in vitro, in stark contrast to the effects on glioma and other cancer cell types. L1LE overexpression resulted in a variable degree of maintenance of HNP proliferation in media without added growth factors but did not increase proliferation. In monolayer culture, HNPs expressed a variety of differentiation markers. L1LE overexpression resulted in loss of glutamine synthetase (GS) and β3-tubulin expression in normal HNP media, and reduced vimentin and increased GS expression in the absence of added growth factors. When co-cultured with chick embryonic brain cell aggregates, HNPs show increased differentiation potential. Some HNPs expressed p-neurofilaments and oligodendrocytic O4, indicating differentiation beyond that in monolayer culture. Most HNP-L1LE cells lost their vimentin and GFAP (glial fibrillary acidic protein) staining, and many cells were positive for astrocytic GS. However, these cells rarely were positive for neuronal markers β3-tubulin or p-neurofilaments, and few HNP oligodendrocyte progenitors were found. These results suggest that unlike for glioma cells, L1LE does not increase HNP cell motility, but rather decreases motility and influences the differentiation of normal brain progenitor cells. Therefore, the effect of L1LE on increasing motility and proliferation appears to be limited to already transformed cells.
成人人类神经祖细胞和干细胞被认为是引发脑癌的潜在细胞来源，但可能导致细胞向转化表型发展的具体事件仍不清楚。L1细胞黏附/识别分子（L1CAM，简称L1）在人类胶质瘤癌细胞中异常表达，并以一种大的细胞外胞外域片段形式释放，该片段可刺激细胞运动和增殖。本研究调查了L1长胞外域（L1LE；约180 kDa）的异位过表达对人类神经祖细胞（HNP）运动、增殖和分化的影响。使用慢病毒载体在HNP中异位表达L1LE。令人惊讶的是，与对胶质瘤和其他癌细胞类型的影响形成鲜明对比，L1LE的过表达导致体外HNP运动性降低。L1LE过表达在未添加生长因子的培养基中导致HNP增殖维持在不同程度，但并未增加增殖。在单层培养中，HNP表达多种分化标志物。L1LE过表达导致在正常HNP培养基中谷氨酰胺合成酶（GS）和β3-微管蛋白表达丧失，而在未添加生长因子的情况下波形蛋白表达减少且GS表达增加。当与鸡胚脑细胞聚集体共培养时，HNP显示出增加的分化潜能。一些HNP表达磷酸化神经丝和少突胶质细胞O4，表明分化程度超过单层培养。大多数HNP-L1LE细胞失去波形蛋白和胶质纤维酸性蛋白（GFAP）染色，许多细胞对星形胶质细胞GS呈阳性。然而，这些细胞很少对神经元标志物β3-微管蛋白或磷酸化神经丝呈阳性，并且几乎未发现HNP少突胶质细胞祖细胞。这些结果表明，与胶质瘤细胞不同，L1LE不会增加HNP细胞运动性，而是降低运动性并影响正常脑祖细胞的分化。因此，L1LE对增加运动性和增殖的作用似乎仅限于已经转化的细胞。
