Identification of Potential Pathways Involved in Induction
of Apoptosis by Butyrate and 4‑Benzoylbutyrate in HT29 Colorectal
Cancer Cells
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Abstract
Butyrate and its analogues have long been investigated as potential
chemotherapeutic agents. Our previous structure–activity relationship
studies of butyrate analogues revealed that 4-benzoylbutyrate had
comparable in vitro effects to butyrate when used to treat HT29 and
HCT116 colorectal cancer cell lines. The aim of this study was to
identify potential mechanisms associated with the antitumorigenic
effects of 4-benzoylbutyrate. In this study, butyrate, 3-hydroxybutyrate
and 4-benzoylbutyrate were also investigated for their effects on
histone deacetylase (HDAC) activity and histone H4 acetylation in
HT29 and HCT116 cells. The biological effects of these analogues on
HT29 cells were further investigated using quantitative proteomics
to determine the proteins potentially involved in their apoptotic
and antiproliferative effects. Because 3-hydroxybutyrate had minimal
to no effect on apoptosis, proliferation or HDAC activity, this analogue
was used to identify differentially expressed proteins that were potentially
specific to the apoptotic effects of butyrate and/or 4-benzoylbutyrate.
Butyrate treatment inhibited HDAC activity and induced H4 acetylation.
4-Benzoylbutyrate inhibited HDAC activity but failed to enhance H4
acetylation. Proteomic analysis revealed 20 proteins whose levels
were similarly altered by both butyrate and 4-benzoylbutyrate. Proteins
that showed common patterns of differential regulation in the presence
of either butyrate or 4-benzoylbutyrate included c-Myc transcriptional
targets, proteins involved in ER homeostasis, signal transduction
pathways and cell energy metabolism. Although an additional 23 proteins
were altered by 4-benzoylbutyrate uniquely, further work is required
to understand the mechanisms involved in its apoptotic effects