Adenovirus infection promotes the formation of glioma stem cells by glioblastoma cells through the TLR9/NEAT1/STAT3 pathway

Abstract

BackgroundGlioma stem cells (GSCs) are glioma cells with stemness and are responsible for a variety of malignant behaviors of glioma. Evidence has shown that signals from tumor microenvironment (TME) enhance stemness of glioma cells, but the identity of the signaling molecules and underlying mechanisms have been incompletely elucidated.MethodsHuman samples and glioma cell lines were cultured in vitro to determine the effects of viral infection by sphere formation, qRT-PCR, Western blot, FACS and immunofluorescence; for in vivo analysis, mice subcutaneous tumor model was carried; while bioinformatics analysis and qRT-PCR were applied for further mechanistic studies.ResultsIn this study, we show that infection of patient-derived glioma cells with adenovirus (ADV) increases the formation of tumor spheres. ADV infection upregulated stem cell markers, and the resultant tumor spheres held the capacities of self-renewal and multi-lineage differentiation, and had stronger potential to form xenograft tumors in immune-compromised mice. ADV promoted GSC formation likely via TLR9, because TLR9 was upregulated after ADV infection, and knockdown of TLR9 reduced ADV-induced GSCs. Consistently, MYD88, as well as total STAT3 and phosphorylated (p-)STAT3, were also upregulated in ADV-induced GSCs. Knockdown of MYD88 or pharmaceutical inhibition of STAT3 attenuated stemness of ADV-induced GSCs. Moreover, we found that ADV infection upregulated lncRNA NEAT1, which is downstream to TLRs and play important roles in cancer stem cells via multiple mechanisms including strengthening STAT3 signaling. Indeed, knockdown of NEAT1 impaired stemness of ADV-induced GSCs. Lastly, we show that HMGB1, a damage associated molecular pattern (DAMP) that also triggers TLR signaling, upregulated stemness markers in glioma cells.ConclusionsIn summary, our data indicate that ADV, which has been developed as vectors for gene therapy and oncolytic virus, promotes the formation of GSCs via TLR9/NEAT1/STAT3 signaling.