NF-κB-Induced IL-6 Ensures STAT3 Activation and Tumor Aggressiveness in Glioblastoma

Abstract

Glioblastoma (GBM) is the most aggressive, neurologically destructive and deadly tumor of the central nervous system (CNS). In GBM, the transcription factors NF-κB and STAT3 are aberrantly activated and associated with tumor cell proliferation, survival, invasion and chemoresistance. In addition, common activators of NF-κB and STAT3, including TNF-α and IL-6, respectively, are abundantly expressed in GBM tumors. Herein, we sought to elucidate the signaling crosstalk that occurs between the NF-κB and STAT3 pathways in GBM tumors. Using cultured GBM cell lines as well as primary human GBM xenografts, we elucidated the signaling crosstalk between the NF-κB and STAT3 pathways utilizing approaches that either a) reduce NF-κB p65 expression, b) inhibit NF-κB activation, c) interfere with IL-6 signaling, or d) inhibit STAT3 activation. Using the clinically relevant human GBM xenograft model, we assessed the efficacy of inhibiting NF-κB and/or STAT3 alone or in combination in mice bearing intracranial xenograft tumors in vivo. We demonstrate that TNF-α-induced activation of NF-κB is sufficient to induce IL-6 expression, activate STAT3, and elevate STAT3 target gene expression in GBM cell lines and human GBM xenografts in vitro. Moreover, the combined inhibition of NF-κB and STAT3 signaling significantly increases survival of mice bearing intracranial tumors. We propose that in GBM, the activation of NF-κB ensures subsequent STAT3 activation through the expression of IL-6. These data verify that pharmacological interventions to effectively inhibit the activity of both NF-κB and STAT3 transcription factors must be used in order to reduce glioma size and aggressiveness.

Therapeutic CK2 inhibition attenuates diverse prosurvival signaling cascades and decreases cell viability in human breast cancer cells

“…Complementary DNA was synthesized and analyzed by quantitative PCR as previously described [52] using the following primers/probe sets purchased from Applied Biosystems: IL-6 (Hs00174131_m1) , SOCS3 (Hs02330328_s1) , IL-8 (Hs00174103_m1) and 18S (Hs99999901_s1).…”

“…The cells were then treated with the indicated doses of CX-4945 for 48 h, and the WST-1 cell viability assay was performed as previously described [52]. For the wound healing assay, MDA-MB-231 cells were plated at confluency and were then scratched once horizontally and thrice vertically using a p200 pipette tip.…”

NF-κB and STAT3 in glioblastoma: therapeutic targets coming of age

“…DHMEQ treatment also synergizes with TMZ and radiation, indicating strong therapeutic potential [69]. Recently, we published in vivo data demonstrating Withaferin A (WA), an IKKβ inhibitor, showed promise at inhibiting NF-κB and GBM growth [70]. Although WA is currently being used in a clinical trial of schizophrenia (NCT01793935), it is not under consideration for use in GBM.…”

“…NF-κB and STAT3 are, for example, known to directly interact with one another in the promoter of ICAM1 post-irradiation [113]. Our lab has also recently demonstrated a feedback mechanism by which NF-κB can induce STAT3 signaling [70]. TNF-α treatment of GBM cell lines in vitro leads to robust NF-κB activation.…”

Down-regulation of Forkhead box protein A1 (FOXA1) leads to cancer stem cell-like properties in tamoxifen-resistant breast cancer cells through induction of interleukin-6

“…Although the precise molecular mechanism of FOXA1-mediated inhibition of expression of these genes is still unknown, our present data suggest that FOXA1 functions as a transcriptional repressor by binding to the promoter regions of these genes. At the IL6 promoter, the canonical NF-B complex binds to the region close to the transcription start site (TSS) and promotes IL6 gene expression (29). In contrast, the FOXA1-binding sites are located at the regions that are several thousands (BS2) or hundreds (BS3) of bases far away from the TSS.…”