The proapoptotic effects of sulindac, sulindac sulfone and indomethacin are mediated by nucleolar translocation of the RelA(p65) subunit of NF-κB

Abstract

Understanding the mechanisms that underlie the antitumour activity of non-steroidal anti-inflammatory drugs (NSAIDs) against colorectal cancer will allow the development of more effective and specific chemopreventative agents. Modulation of the NF-jB pathway has been implicated as a key effector of the antitumour effect of aspirin, but the effects of non-aspirin NSAIDs on this pathway have yet to be fully defined. Here, we demonstrate that sulindac, sulindac sulfone and indomethacin activate the NF-jB pathway in colorectal cancer cells, as determined by western blot analysis of cytoplasmic levels of IjBa and immunocytochemical analysis of nuclear NFjB/RelA. Furthermore, we show that all of these NSAIDs induce nucleolar translocation of the RelA subunit of NFjB. Using RelA deleted for the previously described nucleolar localization signal, we demonstrate that this response is causally involved in the apoptotic effects of these agents. Finally, we demonstrate that NSAIDmediated nucleolar translocation of RelA is associated with downregulation of NF-jB-driven transcription and of the NF-jB target gene, ICAM-1. These data identify nucleolar translocation of RelA and the associated repression of the NF-jB-driven transcription as a central molecular mechanism of NSAID-mediated growth inhibition and apoptosis. As well as providing new understanding of the molecular determinants of RelA function, these findings also have relevance to the development of novel chemotherapeutic and chemopreventative agents.

Nucleolar Targeting of RelA(p65) Is Regulated by COMMD1-Dependent Ubiquitination

“…One post-induction mechanism that we have identified for regulating NF-κB transcriptional activity and apoptosis is the nuclear/nucleolar distribution of RelA. We have shown that in response to specific stress-inducing stimuli, including UV-C radiation, serum deprivation, and aspirin and related agents, RelA translocates from the cytoplasm to the nucleoplasm and then to the nucleolus (11)(12)(13). We identified a signal at the NH 2 terminus of RelA [amino acids (aa) [27][28][29][30] that is required for nucleolar translocation of the protein and showed, using a dominant-negative mutant deleted for this domain, that nucleolar translocation of RelA is causally involved in the downregulation of NF-κB-driven transcription and the induction of apoptosis.…”

Nucleolar NF-κB/RelA mediates apoptosis by causing cytoplasmic relocalization of nucleophosmin

“…However, we described an alternative mechanism for this repression involving nucleolar sequestration of RelA. 13,14 We demonstrated that upon stimulation of the NF-kB pathway by specific stresses (including UV-C radiation, serum deprivation, cyclin-dependent kinase 4 inhibition and aspirin/related agents) the RelA component of NF-kB translocates from the cytoplasm to the nucleoplasm and then to the nucleolus. 13,15 We identified a signal at the N-terminus of RelA (aa [27][28][29][30] that was essential for nucleolar translocation of the protein and, using a dominant negative mutant deleted for this domain (green fluorescent protein (GFP)-RelADNoLS), demonstrated that nucleolar sequestration of RelA is causally involved in the repression of NF-kB-driven transcription and the induction of apoptosis.…”

Clinical Prevention of Recurrence of Colorectal Adenomas by the Combination of Difluoromethylornithine and Sulindac: An Important Milestone

“…Sulindac sulfone is clearly yet another multifunctional drug. Both sulindac sulfide and sulindac sulfone are effective inducers of apoptosis and effective preventive agents in animal models of intestinal neoplasia (14,15,18,19).…”