Cell-cycle arrest at G2/M and growth inhibition by apigenin in human colon carcinoma cell lines.

Wang W ，Heideman L ，Chung CS ，Pelling JC ，Koehler KJ ，Birt DF ... -  《MOLECULAR CARCINOGENESIS》

Individual and interactive effects of apigenin analogs on G2/M cell-cycle arrest in human colon carcinoma cell lines.

Apigenin has been previously shown to induce G2/M cell-cycle arrest in human colon cancer cell lines. The present study assessed the individual and interactive influence of seven apigenin analogs on cell cycle, cell number, and cell viability in human SW480 and Caco-2 colonic carcinoma cells. Cellular concentration of selected apigenin analogs was further assessed by high-performance liquid chromatography to assess cellular availability. The apigenin analogs studied were acacetin, chrysin, kampherol, luteolin, myricetin, naringenin, and quercetin. DNA flow cytometric analysis indicated that treatment with either chrysin or acacetin at 0 to 80 microM for 48 h resulted in cell-cycle arrest at the G2/M phase in a dose-dependent manner in the SW480 cells but not in the Caco-2 cells. The percentage of SW480 cells at G2/M also increased when cells were treated with kampherol, luteolin, or quercetin between 5 and 30 microM, but the percentage of cells in G2/M decreased at doses greater than 40 microM. Cell number was significantly decreased in a time- and dose-dependent manner following the treatments with each analog except for naringenin and myricetin. The interactive effects of these analogs with apigenin were further assessed by combining each analog at doses from 0 to 80 microM with apigenin at 20 microM, a dose at which apigenin was found to double the proportion of SW480 cells in G2/M. When either acacetin, chrysin, luteolin, kampherol, or quercetin at doses between 5 and 30 microM were combined with apigenin at 20 microM, there was an increase of 22% in the proportion of G2/M cells over that observed with 20 microM apigenin alone (P < 0.05). At doses higher than 40 microM, however, the interaction became antagonistic, and the proportion of cells in G2/M decreased below that observed with apigenin alone. Cell viability, as assessed by Trypan blue exclusion assay, significantly decreased by treatments with high doses of each agent or each agent combined with apigenin. Cellular concentration of apigenin, chrysin, or naringenin in SW480 cells significantly increased at doses of 40 microM or greater, but it was not correlated with their impact on G2/M cell-cycle arrest. The induction of cell-cycle arrest by five of seven tested apigenin analogs and the additive induction by the combination of flavonoids at low doses suggest that apigenin-related flavonoids may cooperatively protect against colorectal cancer through conjoint blocking of cell-cycle progression.

Wang W ，VanAlstyne PC ，Irons KA ，Chen S ，Stewart JW ，Birt DF ... -  《NUTRITION AND CANCER-AN INTERNATIONAL JOURNAL》

Apigenin inhibits growth and induces G2/M arrest by modulating cyclin-CDK regulators and ERK MAP kinase activation in breast carcinoma cells.

Yin F ，Giuliano AE ，Law RE ，Van Herle AJ ... -  《ANTICANCER RESEARCH》

Regulation of the cell cycle at the G2/M boundary in metastatic melanoma cells by 12-O-tetradecanoyl phorbol-13-acetate (TPA) by blocking p34cdc2 kinase activity.

12-O-Tetradecanoyl phorbol-13-acetate (TPA) inhibits the growth of most malignant melanoma cells but stimulates the growth of normal human melanocytes. We previously showed that addition of TPA inhibits the growth of the human metastatic melanoma cell line, Demel, by blocking cells at both the G1/S and G2/M cell cycle transitions (D. L. Coppock et al., 1992, Cell Growth Differ. 3, 485-494). To examine the G2/M transition, we developed a method to synchronize the cells in early S phase using Lovastatin and mevalonate, followed by treatment with hydroxyurea (HU). TPA (30 nM) was effective in blocking cells from entering mitosis and reentering G1 when added up to the end of G2. These cells arrested in G2. Examination of the levels of cyclins A and B1 demonstrated that the levels of these cyclins were not limiting for entrance into M. However, the addition of TPA blocked the increase in p34(cdc2)/cyclin B1 kinase activity. In cells treated with TPA, most p34(cdc2) was found in the slowly migrating forms on Western blots, which contained increased levels of phosphotyrosine. In addition, the level of the cyclin-dependent kinase inhibitor p21(Cip1/Waf1), but not of p27(Kip1), was increased. We examined the expression of protein kinase C (PKC) isoforms in Demel cells using Western blots to understand which types were involved in the G2 arrest. Demel cells expressed the PKC alpha, betaI, betaII, delta, epsilon, iota/lambda, zeta, and mu isozymes. PKC eta and PKC theta were not detected. Addition of TPA did not completely down regulate any PKC isozymes over a 12-h period in these synchronized cells. PKC alpha, betaI, betaII, delta, and epsilon isozymes were translocated to the membrane fraction from the cytosolic fraction when treated with TPA. PKC delta appeared as a doublet and the addition of TPA shifted a majority to the slower migrating form. The level of PKC mu was constant; however, a slow mobility form was observed in TPA-treated cells. This reduced mobility was at least partially due to phosphorylation. Thus, the arrest of growth in G2 appears to be due to the inhibition of the p34(cdc2) kinase activity which is associated with the increased expression of p21(Cip1/Waf1) and increased phosphorylation on tyrosine of p34(cdc2). This arrest, in turn, is associated with a shift of PKC isozymes PKC alpha, PKC betaI, PKC betaII, PKC delta, PKC epsilon, and PKC mu to the membrane fraction which is induced by addition of TPA.

Arita Y ，Buffolino P ，Coppock DL 《EXPERIMENTAL CELL RESEARCH》

Effect of arsenic trioxide on cell cycle arrest in head and neck cancer cell line PCI-1.

Arsenic trioxide (As(2)O(3)) has been shown to inhibit the proliferation of hematologic malignant cells. However, little is known about the effect of As(2)O(3) on solid tumor. In this study, we investigated the antitumoral effect of As(2)O(3) on head and neck cancer cell lines in vitro. Treatment of As(2)O(3) inhibited the proliferation of all of 4 cell lines examined in a dose-dependent manner. To address the mechanism of antitumoral effect of As(2)O(3), cell cycle analysis was attempted in As(2)O(3)-most sensitive PCI-1 cells. Treatment of As(2)O(3) (2 microM) induced efficiently G2/M arrest in PCI-1 cells following 3 days of exposure. During the G2/M arrest, cyclin-dependent kinase inhibitor, p21, was increased in a time-dependent manner. Analysis of cell cycle regulatory proteins demonstrated that As(2)O(3) (2 microM) did not change the steady-state levels of CDK2, CDK4, CDK6, cyclin D1, cyclin E and cyclin A, but decreased the protein levels of cdc2 and cyclin B1. Furthermore, treatment of As(2)O(3) markedly enhanced the binding of p21 with cdc2, and the activity of cdc2 kinase was decreased in a time-dependent manner. These results suggest that As(2)O(3) inhibits the proliferation of head and neck cancer cells via G2/M arrest in association with the induction of p21 and the reduction of cdc2 kinase activity.

Seol JG ，Park WH ，Kim ES ，Jung CW ，Hyun JM ，Kim BK ，Lee YY ... -  《BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS》