Induction of G1 and G2/M cell cycle arrests by the dietary compound 3,3'-diindolylmethane in HT-29 human colon cancer cells

<p>Abstract</p> <p>Background</p> <p>3,3'-Diindolylmethane (DIM), an indole derivative produced in the stomach after the consumption of broccoli and other cruciferous vegetables, has been demonstrated to exert anti-cancer effects in both <it>in vivo </it>and <it>in vitro </it>models. We have previously determined that DIM (0 – 30 μmol/L) inhibited the growth of HT-29 human colon cancer cells in a concentration-dependent fashion. In this study, we evaluated the effects of DIM on cell cycle progression in HT-29 cells.</p> <p>Methods</p> <p>HT-29 cells were cultured with various concentrations of DIM (0 – 30 μmol/L) and the DNA was stained with propidium iodide, followed by flow cytometric analysis. [³H]Thymidine incorporation assays, Western blot analyses, immunoprecipitation and <it>in vitro </it>kinase assays for cyclin-dependent kinase (CDK) and cell division cycle (CDC)2 were conducted.</p> <p>Results</p> <p>The percentages of cells in the G1 and G2/M phases were dose-dependently increased and the percentages of cells in S phase were reduced within 12 h in DIM-treated cells. DIM also reduced DNA synthesis in a dose-dependent fashion. DIM markedly reduced CDK2 activity and the levels of phosphorylated retinoblastoma proteins (Rb) and E2F-1, and also increased the levels of hypophosphorylated Rb. DIM reduced the protein levels of cyclin A, D1, and CDK4. DIM also increased the protein levels of CDK inhibitors, p21^CIP1/WAF1and p27^KIPI. In addition, DIM reduced the activity of CDC2 and the levels of CDC25C phosphatase and cyclin B1.</p> <p>Conclusion</p> <p>Here, we have demonstrated that DIM induces G1 and G2/M phase cell cycle arrest in HT-29 cells, and this effect may be mediated by reduced CDK activity.</p

Examining the role of ideological and political education on university students’ civic perceptions and civic participation in Mainland China: Some hints from contemporary citizenship theory

A long existing compulsive curriculum of ideological and political education is employed by the Chinese government to promote citizenship education among Chinese university students. This article builds on the findings of a mixed-methods research that examined the role of ideological and political education on university students’ civic perceptions and civic participation. The results showed little evidence of this curriculum having a clear effect on students’ political participation such as voting, as well as their idealized broad civic participation, but did reveal relatively positive effects on students’ civic intention and civic expression. In addition, it also identified its significant role in organizing students towards attending party-related activities. It shows that ideological and political education is insufficient to achieve specified aims of citizenship education among Chinese university students. We then argue that it results from a mechanistic understanding of citizenship and participation in educational policies and structural barriers to young people’s formal participation. Hence, this article argues that the forms and contents of citizenship education in China need to be reconsidered beyond the limits of the current ideological and political education and that the analyses contributed to an argument for a broader approach to citizenship education to be developed and adopted