We recently found that neurotensin (NTS) and its primary receptor NTSR1 play a crucial role in glioblastoma cell proliferation and invasion. However, very little is known regarding the functional role of NTS/NTSR1 signaling in glioblastoma stem cells (GSCs). Here, we showed that NTSR1 is highly expressed in GSCs than its non-GSC counterparts. Pharmacological blockade with SR48692 or lentivirus mediated knockdown of NTSR1 efficiently reduced the sphere-forming ability and expression of stem cell markers such as nestin and Sox2 in GSCs isolated from glioblastoma cell line and glioblastoma tissues. Conversely, treated GSCs with NTS led to increase of tumor sphere formation. Mechanistically, we demonstrated that EGFR-dependent enhancement of IL-8 secretion is responsible for the effect of NTS signaling in the regulation of stem-like traits. Finally, we showed that NTSR1 or IL-8 knockdown decreased the phosphorylation of transcriptional factor STAT3 at Tyr705, which is a major transcription factor implicated in the regulation of GSC stem-like traits. Although both CXCR1 and CXCR2 inhibition reduced the tumor sphere formation, we found that CXCR1, but not CXCR2, is primarily responsible for STAT3 phosphorylation. Taken together, our findings suggest that NTS/IL-8/CXCR1/STAT3 signaling is crucial for the maintenance of stem-like traits in GSCs and provides a potential therapeutic target for glioblastoma therapy.
Keywords: Cancer stem cell; Glioblastoma; Interleukin-8; Neurotensin; STAT3.
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