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1.  TWIST1 associates with NF-κB subunit RELA via carboxyl-terminal WR domain to promote cell autonomous invasion through IL8 production 
BMC Biology  2012;10:73.
Metastasis is the primary cause of death for cancer patients. TWIST1, an evolutionarily conserved basic helix-loop-helix (bHLH) transcription factor, is a strong promoter of metastatic spread and its expression is elevated in many advanced human carcinomas. However, the molecular events triggered by TWIST1 to motivate dissemination of cancer cells are largely unknown.
Here we show that TWIST1 induces the production of interleukin 8 (IL8), which activates matrix metalloproteinases and promotes invasion of breast epithelial and cancer cells. In this novel mechanism, TWIST1-mediated IL8 transcription is induced through the TWIST1 carboxy-terminal WR (Trp-Arg) domain instead of the classic DNA binding bHLH domain. Co-immunoprecipitation analyses revealed that the WR domain mediates the formation of a protein complex comprised of TWIST1 and the nuclear factor-kappaB (NF-κB) subunit RELA (p65/NF-κB3), which synergistically activates the transcriptional activity of NF-κB. This activation leads to increased DNA binding affinity of RELA to the IL8 promoter and thus induces the expression of the cytokine. Blockage of IL8 signaling by IL8 neutralizing antibodies or receptor inhibition reduced the invasiveness of both breast epithelial and cancer cells, indicating that TWIST1 induces autonomous cell invasion by establishing an IL8 antocrine loop.
Our data demonstrate that the TWIST1 WR domain plays a critical role in TWIST1-induced IL8 expression through interactions with and activation of NF-κB. The produced IL8 signals through an autocrine loop and promotes extracellular matrix degradation to enable cell invasion across the basement membrane.
PMCID: PMC3482588  PMID: 22891766
TWIST1; WR domain; RELA; NF-κB; IL8
2.  A Synergistic Role for IL-1β and TNFα in Monocyte Derived IFNγ Inducing Activity 
Cytokine  2008;44(2):234-241.
Although much is known about classic IFNγ inducers, little is known about the IFNγ inducing capability of inflammasome-activated monocytes. In this study, supernatants from LPS/ATP-stimulated human monocytes were analyzed for their ability to induce IFNγ production by KG-1 cells. Unexpectedly, monocyte-derived IFNγ inducing activity was detected, but it was completely inhibited by IL-1β, not IL-18 blockade. Moreover, size-fractionation of the monocyte conditioned media dramatically reduced the IFNγ inducing activity of IL-1β, suggesting that IL-1β requires a cofactor to induce IFNγ production in KG-1 cells. Because TNFα is known to synergize with IL-1β for various gene products, it was studied as the putative IL-1β synergizing factor. Although recombinant TNFα (rTNFα) alone had no IFNγ inducing activity, neutralization of TNFα in the monocyte conditioned media inhibited the IFNγ inducing activity. Furthermore, rTNFα restored the IFNγ inducing activity of the size-fractionated IL-1β. Finally, rTNFα synergized with rIL-1β, as well as with rIL-1α and rIL-18, for KG-1 IFNγ release. These studies demonstrate a synergistic role between TNFα and IL-1 family members in the induction of IFNγ production and give caution to interpretations of KG-1 functional assays designed to detect functional IL-18.
PMCID: PMC2648511  PMID: 18805021
Interleukin-1; caspase-1; TNFα; KG-1 cell line; IFNγ
3.  Monocyte Derived Microvesicles Deliver a Cell Death Message via Encapsulated Caspase-1 
PLoS ONE  2009;4(9):e7140.
Apoptosis depends upon the activation of intracellular caspases which are classically induced by either an intrinsic (mitochondrial based) or extrinsic (cytokine) pathway. However, in the process of explaining how endotoxin activated monocytes are able to induce apoptosis of vascular smooth muscle cells when co-cultured, we uncovered a transcellular apoptosis inducing pathway that utilizes caspase-1 containing microvesicles. Endotoxin stimulated monocytes induce the cell death of VSMCs but this activity is found in 100,000 g pellets of cell free supernatants of these monocytes. This activity is not a direct effect of endotoxin, and is inhibited by the caspase-1 inhibitor YVADcmk but not by inhibitors of Fas-L, IL-1β and IL-18. Importantly, the apoptosis inducing activity co-purifies with 100 nm sized microvesicles as determined by TEM of the pellets. These microvesicles contain caspase-1 and caspase-1 encapsulation is required since disruption of microvesicular integrity destroys the apoptotic activity but not the caspase-1 enzymatic activity. Thus, monocytes are capable of delivering a cell death message which depends upon the release of microvesicles containing functional caspase-1. This transcellular apoptosis induction pathway describes a novel pathway for inflammation induced programmed cell death.
PMCID: PMC2744928  PMID: 19779610
4.  A Novel Role for IκBζ in the Regulation of IFNγ Production 
PLoS ONE  2009;4(8):e6776.
IκBζ is a novel member of the IκB family of NFκB regulators, which modulates NFκB activity in the nucleus, rather than controlling its nuclear translocation. IκBζ is specifically induced by IL-1β and several TLR ligands and positively regulates NFκB-mediated transcription of genes such as IL-6 and NGAL as an NFκB binding co-factor. We recently reported that the IL-1 family cytokines, IL-1β and IL-18, strongly synergize with TNFα for IFNγ production in KG-1 cells, whereas the same cytokines alone have minimal effects on IFNγ production. Given the striking similarities between the IL-1R and IL-18R signaling pathways we hypothesized that a common signaling event or gene product downstream of these receptors is responsible for the observed synergy. We investigated IκBζ protein expression in KG-1 cells upon stimulation with IL-1β, IL-18 and TNFα. Our results demonstrated that IL-18, as well as IL-1β, induced moderate IκBζ expression in KG-1 cells. However, TNFα synergized with IL-1β and IL-18, whereas by itself it had a minimal effect on IκBζ expression. NFκB inhibition resulted in decreased IL-1β/IL-18/TNFα-stimulated IFNγ release. Moreover, silencing of IκBζ expression led to a specific decrease in IFNγ production. Overall, our data suggests that IκBζ positively regulates NFκB-mediated IFNγ production in KG-1 cells.
PMCID: PMC2727951  PMID: 19707556

Results 1-4 (4)