How Stemlike Are Sphere Cultures From Long-term Cancer Cell Lines? Lessons From Mouse Glioma Models

Abstract

Cancer stem cells may mediate therapy resistance and recurrence in various types of cancer, including glioblastoma. Cancer stemlike cells can be isolated from long-term cancer cell lines, including glioma lines. Using sphere formation as a model for cancer cell stemness in vitro, we derived sphere cultures from SMA-497, SMA-540, SMA-560, and GL-261 glioma cells. Gene expression and proteomics profiling demonstrated that sphere cultures uniformly showed an elevated expression of stemness-associated genes, notably including CD44. Differences in neural lineage marker expression between nonsphere and sphere cultures were heterogeneous except for a uniform reduction of β-III-tubulin in sphere cultures. All sphere cultures showed slower growth. Self-renewal capacity was influenced by medium conditions but not nonsphere versus sphere culture phenotype. Sphere cultures were more resistant to irradiation, whereas both nonsphere and sphere cultures were highly resistant to temozolomide. Nonsphere cells formed more aggressive tumors in syngeneic mice than sphere cells in all models except SMA-560. There were no major differences in vascularization or infiltration by T cells or microglia/macrophages between nonsphere and sphere cell-derived tumors implanted in syngeneic hosts. Together, these data indicate that mouse glioma cell lines may be induced in vitro to form spheres that acquire features of stemness, but they do not exhibit a uniform biologic phenotype, thereby challenging the view that they represent a superior model system.

Rapamycin promotes differentiation increasing βIII-tubulin, NeuN, and NeuroD while suppressing nestin expression in glioblastoma cells

“…It is worth being noticed that this marker was already present, albeit at very low concentrations, in control cells (representative Figure 8A). This unexpected occurrence confirms what already reported in the literature [26, 27], thus toning down the absolute significance of this antigen as a fully reliable neuronal marker. In fact, βIII-tubulin may also occur quite ubiquitously in low amount owing a non specific significance.…”

Motility of glioblastoma cells is driven by netrin-1 induced gain of stemness

“…Freshly isolated GBM cell-lines that are kept under the stem-like cell proliferation favoring culture conditions are a better model for investigating glioma stem-like cells than long cultured cell lines [1, 40]. Therefore we established primary GBM stem-like cell cultures (GBM9 and GBM10) from surgical GBM biopsies.…”

Potential use of glioblastoma tumorsphere: clinical credentialing

“…Moreover, as the cells with the classical property of CSCs are included in TS (Ahmad et al 2014), we personally think that the term ''tumorsphere'' is currently more practical than ''CSC''. However, the terms of ''tumorsphere'' and ''CSC'' or ''cancer initiating cell (CIC)'' are used as the same concept in many documents and theses (Romaguera-Ros et al 2012;Sulman et al 2008;Xu et al 2008).…”