Acyclic retinoid, a novel synthetic retinoid, induces growth inhibition, apoptosis, and changes in mRNA expression of cell cycle- and differentiation-related molecules in human colon carcinoma cells

Abstract

Acyclic retinoid (ACR), a novel synthetic retinoid, has been demonstrated by us to inhibit the in vitro growth of human hepatoma cells, and this effect was associated with modification of cell cycle control molecules, suggesting that this agent may be useful in the chemoprevention and therapy of various types of malignancies. However, whether or not ACR exerts anticancer activities on human colon carcinoma cells has not yet been elucidated. The purpose of this study was to examine the inhibitory effects of ACR in human colon carcinoma cells and to characterize the molecular mechanism of action of this agent. ACR inhibited the growth of the HCT116 and SW480 human colon carcinoma cell lines with IC 50 values of about 30 and 60 μM, respectively. ACR also induced G1-phase cell cycle arrest and apoptosis in these cell lines. When the HCT116 cells were treated with 5-25 μM ACR, there was a marked decrease in the cellular levels of cyclin D1 mRNA and an approximate 2.5-to 3-fold increase in those of p21 CIP1 mRNA, and this induction occurred via a p53-independent mechanism. Furthermore, ACR induced a dose-dependent mRNA elevation of differentiation markers at concentrations of ACR that affect the levels of expression of p21 CIP1 . These novel results suggest that ACR inhibits cell proliferation by inducing G1 arrest and apoptosis and that cyclin D1 and p21 CIP1 play critical roles in the molecular mechanisms of growth inhibition and differentiation induced by ACR. Collectively, these findings provide further evidence that ACR may be a potential agent for the chemoprevention and therapy of human colon cancer.

Growth inhibitory activity of ethanol extracts of Chinese and Brazilian propolis in four human colon carcinoma cell lines

“…The analysis was also performed as recently described (11,12). HCT116 and HT29 cells were plated onto 9-cm diameter culture dishes (1.5x10 5 cells per dish) in DMEM plus 10% FBS and cultured to yield 50-60% confluence.…”

“…After 72 h of treatment, both adherent floating cells were harvested, washed twice with phosphate buffered saline (PBS), fixed with 70% ethanol, centrifuged, resuspendend in 400 μl of 2 mg/ml RNase (Nacalai Tesque, Kyoto, Japan), stained with 0.1 mg/ml propidium iodide (PI, Nacalai Tesque), and filtrated through a nylon mesh (Tokyo Screen Co., Ltd., Tokyo, Japan). Flow cytometric analysis was performed on a FACSCalibur instrument (Becton-Dickinson) as previously described (11,12). The distribution of cells in the sub-G1, G1, S and G2-M phases of the cell cycle were calculated using CellQuest Pro computer program (Becton-Dickinson).…”

“…These assays were performed as recently described (11,12). Cell proliferation was measured by using an MTT assay kit (Roche Diagnostics Corp., Indianapolis, IN) that measures a purple formazan compound produced by viable cells.…”

“…These assays were performed by established procedures (11,12). Total RNA was isolated from frozen cells treated with 10 or 20 μg/ml extracts of Chinese propolis for 72 h using a TRIzol reagent (Invitrogen Life Technologies, Inc., Rockville, MD) as recommended by the manufacturer.…”

Enhancement of tongue carcinogenesis in Hras128 transgenic rats treated with 4-nitroquinoline 1-oxide

“…These assays were performed by established procedures (20). Snap-frozen histopathologically verified tongue tumors were randomly chosen and total RNA was extracted for RT-PCR assays.…”