Inhibition of Oncogenic Transcription Factor REL by the Natural Product Derivative Calafianin Monomer 101 Induces Proliferation Arrest and Apoptosis in Human B-Lymphoma Cell Lines.

Alan Yeo,Spandan Chennamadhavuni,John Porco,Thomas Gilmore,Adrian Whitty

doi:10.3390/molecules20057474

Alan Yeo, Spandan Chennamadhavuni + Show 3 more

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https://doi.org/10.3390/molecules20057474

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Journal: Molecules (Basel, Switzerland)	Publication Date: Apr 23, 2015
Citations: 51	License type: CC BY 4.0

Affiliation: Boston University

Abstract

Increased activity of transcription factor NF-κB has been implicated in many B-cell lymphomas. We investigated effects of synthetic compound calafianin monomer (CM101) on biochemical and biological properties of NF-κB. In human 293 cells, CM101 selectively inhibited DNA binding by overexpressed NF-κB subunits REL (human c-Rel) and p65 as compared to NF-κB p50, and inhibition of REL and p65 DNA binding by CM101 required a conserved cysteine residue. CM101 also inhibited DNA binding by REL in human B-lymphoma cell lines, and the sensitivity of several B-lymphoma cell lines to CM101-induced proliferation arrest and apoptosis correlated with levels of cellular and nuclear REL. CM101 treatment induced both phosphorylation and decreased expression of anti-apoptotic protein Bcl-XL, a REL target gene product, in sensitive B-lymphoma cell lines. Ectopic expression of Bcl-XL protected SUDHL-2 B-lymphoma cells against CM101-induced apoptosis, and overexpression of a transforming mutant of REL decreased the sensitivity of BJAB B-lymphoma cells to CM101-induced apoptosis. Lipopolysaccharide-induced activation of NF-κB signaling upstream components occurred in RAW264.7 macrophages at CM101 concentrations that blocked NF-κB DNA binding. Direct inhibitors of REL may be useful for treating B-cell lymphomas in which REL is active, and may inhibit B-lymphoma cell growth at doses that do not affect some immune-related responses in normal cells.

Highlights

Many cancer cell types show high levels of constitutive activity of NF-κB transcription factors (p50, p52, RelA/p65, c-Rel/REL and RelB) [1]
Two days later, transfected cells were treated with increasing concentrations of CM101 for 2 h, and extracts were prepared and analyzed by electrophoretic mobility shift assay (EMSA) using a consensus NF-κB probe
We investigated whether CM101 could inhibit constitutive NF-κB DNA binding in these lymphoma cells, and if so, whether CM101-induced inhibition of nuclear κB-site DNA binding correlated with the ability of CM101 to induce growth arrest and apoptosis

Summary

Introduction

Many cancer cell types show high levels of constitutive activity of NF-κB transcription factors (p50, p52, RelA/p65, c-Rel/REL and RelB) [1]. B-cell lymphoma (DLBCL), Hodgkin’s lymphoma and follicular lymphoma [2], and overexpression of wild-type and mutant forms of human REL can transform lymphoid cells in culture [3,4]. Inhibition of REL can arrest the growth of B-lymphoma cell lines in vitro [5,6,7]. All NF-κB transcription factors have a conserved N-terminal domain called the Rel Homology. The NF-κB superfamily can be divided into two subfamilies—Rel proteins (c-Rel, p65, RelB) and NF-κB proteins (p50, p52)—based on sequence similarity within the RHD, as well as in sequences C-terminal to the RHD [8].

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