Interleukin-1β and transforming growth factor-β cooperate to induce neurosphere formation and increase tumorigenicity of adherent LN-229 glioma cells

Abstract

IntroductionGlioma stem cells (GSCs) have the property of self-renewal and appear to be a driving force for the initiation and recurrence of gliomas. We recently found that the human tumorigenic LN-229 glioma cell line failed to form neurospheres in serum-free conditions and generated mostly small tumors in vivo, suggesting that either LN-229 GSCs are not active in these conditions or GSCs are absent in the LN-229 cell line.MethodsUsing self-renewal assay, soft-agar colony assay, cell proliferation assay, invasion assay, real time PCR analysis, ELISA and in vivo tumorigenic assay, we investigated the effects of interleukin (IL)-1β and transforming growth factor (TGF)-β on the development of GSCs from LN-229 cells.ResultsHere, we demonstrate that the combination of IL-1β and TGF-β can induce LN-229 cells to form neurospheres in serum-free medium. IL-1β/TGF-β-induced neurospheres display up-regulated expression of stemness factor genes (nestin, Bmi-1, Notch-2 and LIF), and increased invasiveness, drug resistance and tumor growth in vivo: hallmarks of GSCs. These results indicate that IL-1β and TGF-β cooperate to induce a GSC phenotype in the LN-229 cell line. Induction of nestin, LIF and Notch-2 by IL-1β/TGF-β can be reverted after cytokine withdrawal. Remarkably, however, up-regulated Bmi-1 levels remained unchanged after cytokine withdrawal; and the cytokine-withdrawn cells maintained strong clonogenicity, suggesting that Bmi-1 may play a crucial role in tumorigenesis.ConclusionsOur finding indicates that glioma cells without self-renewal capability in standard conditions could also contribute to glioma malignancy when cytokines, such as IL-1β and TGF-β, are present in the tumor environment. Targeting GSC-promoting cytokines that are highly expressed in glioblastomas may contribute to the development of more effective glioma therapies.

Pathophysiological mechanisms regulated by cytokines in gliomas

“…High TGF-b levels secreted by gliomas inactivate the immune cytotoxic response via downregulation of Natural Killer Group 2 member D (NKG2D) receptor in their surface [31]. IL-1 has also been indicated to induce the expression of Bim-1, LIF and Notch-2 proteins synergistically with TGF-b [32]. These agents are correlated with increased expression of nestin, indicating an augmented self-renewal rate of glioma stem cells.…”

“…Moreover, IL-1 action as an iNOS stimulator is responsible for the increased levels of NO in glioma cell lines with concentration-dependent effects on tumor progression or suppression [59,60]. IL-1 has also been indicated to induce the expression of Bim-1, LIF and Notch-2 proteins synergistically with TGF-b [32]. The upregulation of these proteins is responsible for the self-renewal ability of glioma cells that leads to increased proliferation rates.…”

“…These agents are correlated with increased expression of nestin, indicating an augmented self-renewal rate of glioma stem cells. In association to the increased expression of N-cadherin, SIP-1 and b-integrin which promote the invasiveness of the tumor, this leads to a more aggressive type of cancer and thus a worse prognosis [32].…”

Internal ribosome entry site of bFGF is the target of thalidomide for IMiDs development in multiple myeloma

“…The AIG of cancer cells in vitro has proved to be a useful tool to enrich cancer stem-like cells [21], a subpopulation of tumor cells with the ability to undergo self-renewal and recapitulate the entire tumor population in vitro and in vivo [35]. In our studies, we compared culture medium cultivated (RPMI8226 and U266), monolayer (FO cells) and AIG of MM cells.…”

Insulin Resistance and Inflammation in Black Women with and without Breast Cancer: Cause for Concern

“…35 IL-1-β may also mediate the function of pancreatic beta cells during diabetes development, [36][37][38] suggesting the role that IL-1-β plays in obesity and insulin resistance. In gliomas, IL1-β is postulated to be responsible for stem cell proliferation, sphere formation, and tumorigenicity, 39 and it is possible that it may have activity in other tumor types.…”