We previously showed that nonsteroidal anti-inflammatory drugs (
NSAID) such as
sulindac sulfide, which has chemopreventive activity, modulate the expression of several genes detected by microarray analysis.
Activating transcription factor 3 (ATF3) was selected for further study because it is a
transcription factor involved in cell proliferation, apoptosis, and invasion, and its expression is repressed in human
colorectal tumors as compared with normal adjacent tissue. In this report, we show that ATF3
mRNA and
protein expression are up-regulated in HCT-116 human
colorectal cancer cells following treatment with
NSAIDs,
troglitazone,
diallyl disulfide, and
resveratrol. To ascertain the
biological significance of ATF3, we overexpressed full-length ATF3
protein in the sense and antisense orientations. Overexpression of ATF3 in the sense orientation decreased focus formation in vitro and reduced the size of mouse
tumor xenografts by 54% in vivo. Conversely, overexpression of antisense ATF3 was protumorigenic in vitro, however, not in vivo. ATF3 in the sense orientation did not modulate apoptosis, indicating another mechanism is involved. With microarray analysis, several genes relating to invasion and
metastasis were identified by ATF3 overexpression and were confirmed by real-time reverse transcription-PCR, and several of these genes were modulated by
sulindac sulfide, which inhibited invasion in these cells. Furthermore, overexpression of ATF3 inhibited invasion to a similar degree as
sulindac sulfide treatment, whereas antisense ATF3 increased invasion. In conclusion, ATF3 represents a novel mechanism in which
NSAIDs exert their anti-invasive activity, thereby linking ATF3 and its gene regulatory activity to the
biological activity of these compounds.