A bioactive withanolide Tubocapsanolide A inhibits proliferation of human lung cancer cells via repressing Skp2 expression.
Withanolides are generally defined as C(28) steroidal lactones built on an intact or rearranged ergostane skeleton and have been shown to exhibit antiproliferative activity on various types of cancer cells. In this study, we investigated the effect of a new withanolide Tubocapsanolide A isolated from Tubocapsicum anomalum and addressed its molecular action. Tubocapsanolide A inhibited proliferation of A549, H358, and H226 human lung cancer cells via induction of G(1) growth arrest. We found that Tubocapsanolide A treatment led to up-regulation of cyclin E, p21, and p27, whereas other cyclins and cyclin-dependent kinases were not affected in A549 cells. Conversely, Skp2, the F-box protein that is implicated in the mediation of degradation of p21 and p27, was significantly down-regulated. Chromatin immunoprecipitation assay suggested that Tubocapsanolide A suppressed Skp2 expression by inhibiting the binding of Rel A to the nuclear factor-kappaB site of Skp2 gene promoter. In addition, we showed that inhibition of Skp2 is a critical step for the suppression of cell proliferation by Tubocapsanolide A because ectoexpression of Skp2 effectively reversed Tubocapsanolide A-induced p27 up-regulation and growth inhibition in human lung cancer cells. Collectively, we have identified Skp2 as a molecular target for Tubocapsanolide A and suggest that this withanolide may be useful for the prevention or treatment of cancer cells with Skp2 overexpression.
Chang
Hui-Chiu
HC
Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan, Republic of China. m740127@kmu.edu.tw
Chang
Fang-Rong
FR
Wang
Yu-Chu
YC
Pan
Mei-Ren
MR
Hung
Wen-Chun
WC
Wu
Yang-Chang
YC
D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004305:Dose-Response Relationship, Drug; D004354:Drug Screening Assays, Antitumor; D004875:Ergosterol / Q000031:analogs & derivatives*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy*; D010936:Plant Extracts / Q000494:pharmacology; D010946:Plants, Medicinal / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000737:chemistry; D044786:S-Phase Kinase-Associated Proteins / Q000037:antagonists & inhibitors*; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology
D000970:Antineoplastic Agents; D010936:Plant Extracts; D011506:Proteins; D044786:S-Phase Kinase-Associated Proteins; D013778:Tetrazolium Salts; D013844:Thiazoles; C522061:tubocapsanolide A; C022616:thiazolyl blue; D004875:Ergosterol