Induction of p21 protein protects against sulforaphane-induced mitotic arrest in LNCaP human prostate cancer cell line.

Abstract

Previous studies have indicated that d,l-sulforaphane (SFN), a synthetic cancer chemopreventive analogue of cruciferous vegetable-derived isomer (-)-1-isothiocyanato-(4R)-(methylsulfinyl)-butane, activates a checkpoint kinase 2 (Chk2)-dependent G(2)-M phase cell cycle arrest in p53-deficient human prostate cancer cells. Because p53 is a downstream target of Chk2 kinase and known to regulate G(2)-M transition by transcriptional regulation of cyclin-dependent kinase (Cdk) inhibitor p21(Cip1/Waf1) (p21), the present study was undertaken to determine the role of p21 in SFN-induced cell cycle arrest using wild-type p53-expressing cell line LNCaP. The SFN treatment caused a modest increase in S phase fraction and a marked increase in G(2)-M fraction in LNCaP cells in a concentration- and time-dependent manner. The SFN-induced S phase arrest correlated with a reduction in protein levels of cyclin D1, cyclin E, Cdk4, and Cdk6, whereas activation of the G(2)-M checkpoint was accompanied by induction of cyclin B1 and down-regulation of Cdk1 and Cdc25C protein levels. The SFN-treated LNCaP cells were also arrested in mitosis as revealed by immunofluorescence microscopy and increased Ser(10) phosphorylation of histone H3, a sensitive marker for mitotic cells. The SFN treatment increased activating phosphorylation of Chk2 (Thr(68)) that was accompanied by induction of p53 and p21. The SFN-induced mitotic arrest was statistically significantly increased by small interfering RNA-based knockdown of p21. However, p21 protein knockdown did not have any appreciable effect on SFN-induced cytoplasmic histone-associated DNA fragmentation (apoptosis). In conclusion, the present study indicates that induction of p21 protects against SFN-induced mitotic arrest in LNCaP cells.

• Authors: Anna Herman-Antosiewicz, Hui Xiao, Karen L Lew, Shivendra V Singh
• Journal: Molecular cancer therapeutics (Mol Cancer Ther) Vol. 6 Issue 5 Pg. 1673-81 (May 2007) ISSN: 1535-7163 [Print] United States
• PMID: 17513615 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Anticarcinogenic Agents
• CDKN1A protein, human
• Cyclin-Dependent Kinase Inhibitor p21
• Histones
• Isothiocyanates
• Sulfoxides
• TP53 protein, human
• Thiocyanates
• Tumor Suppressor Protein p53
• sulforaphane

Topics

• Anticarcinogenic Agents (pharmacology)
• Cell Cycle
• Cell Division
• Cell Line, Tumor
• Cyclin-Dependent Kinase Inhibitor p21 (metabolism)
• G2 Phase
• Gene Expression Regulation, Neoplastic
• Histones (metabolism)
• Humans
• Isothiocyanates
• Male
• Microscopy, Fluorescence
• Mitosis
• Prostatic Neoplasms (drug therapy)
• Sulfoxides
• Thiocyanates (pharmacology)
• Tumor Suppressor Protein p53 (metabolism)