Ulcerative colitis (UC) is a
chronic disease, in which the lining of the colon becomes inflamed and develops
ulcers leading to
abdominal pain,
diarrhea, and rectal
bleeding. The extent of these symptoms depends on disease severity. The
protein arginine deiminase (PAD) family of
enzymes converts peptidyl-
Arginine to peptidyl-
Citrulline through citrullination. PADs are dysregulated, with abnormal citrullination in many diseases, including UC and
colorectal cancer (CRC). We have developed the small molecule, pan-PAD inhibitor, Chlor-amidine (
Cl-amidine), with multiple goals, including treating UC and preventing CRC. Building off our recent results showing that: 1)
Cl-amidine suppresses
colitis in vivo in a
dextran sulfate sodium (DSS) mouse model; and 2)
Cl-amidine induces
microRNA (miR)-16 in vitro causing cell cycle arrest, we tested the hypothesis that
Cl-amidine can prevent
tumorigenesis and that miR-16 induction, by
Cl-amidine, may be involved in vivo. Consistent with our hypothesis, we present evidence that
Cl-amidine, delivered in the
drinking water, prevents colon
tumorigenesis in our mouse model of
colitis-associated CRC where mice are given carcinogenic
azoxymethane (AOM), followed by multiple cycles of 2% DSS to induce
colitis. To begin identifying mechanisms, we examined the effects of
Cl-amidine on miR-16. Results show miR-16 suppression during the
colitis-to-
cancer sequence in colon epithelial cells, which was rescued by drinking
Cl-amidine. Likewise, Ki67 and cellular proliferation targets of miR-16 (
Cyclins D1 and E1) were suppressed by
Cl-amidine. The decrease in cell proliferation markers and increase in
tumor suppressor
miRNA expression potentially define a mechanism of how
Cl-amidine is suppressing
tumorigenesis in vivo.