Cladosporol a stimulates G1-phase arrest of the cell cycle by up-regulation of p21(waf1/cip1) expression in human colon carcinoma HT-29 cells.
Cladosporols, purified and characterized as secondary metabolites from Cladosporium tenuissimum, display an antifungal activity. In this study, we tested the antiproliferative properties of cladosporol A, the main isoform of this metabolite family, against human cancer cell lines. By assessing cell viability, we found that cladosporol A inhibits the growth of various human colon cancers derived cell lines (HT-29, SW480, and CaCo-2) in a time- and concentration-dependent manner, specifically of HT-29  cells. The reduced cell proliferation was due to a G1-phase arrest, as assessed by fluorescence activated cell sorting analysis on synchronized HT-29  cells, and was associated with an early and robust over-expression of p21(waf1/cip1) , the well-known cyclin-dependent kinases inhibitor. This suggests that the drug may play a role in the control of cancer cell proliferation. Consistently, cyclin D1, cyclin E, CDK2, and CDK4 proteins were reduced and histone H1-associated CDK2 kinase activity inhibited. In addition to p21(waf1/cip1) , exposure to 20 µM cladosporol A caused a simultaneous increase of pERK and pJNK, suggesting that this drug activates a circuit that integrates cell cycle regulation and the signaling pathways both involved in the inhibition of cell proliferation. Finally, we showed that the increase of p21(waf1/cip1) expression was generated by a Sp1-dependent p53-independent stimulation of its gene transcription as mutagenesis of the Sp1 binding sites located in the p21 proximal promoter abolished induction. To our knowledge, this is the first report showing that cladosporol A inhibits colon cancer cell proliferation by modulating p21(waf1/cip1) expression.
Dipartimento di Scienze Biologiche ed Ambientali, Facoltà di Scienze, Università del Sannio, Benevento, Italy.
Diana
D
Zurlo
Cinzia
C
Leone
Gemma
G
Assante
Salvatore
S
Salzano
Giovanni
G
Renzone
Andrea
A
Scaloni
Caterina
C
Foresta
Vittorio
V
Colantuoni
Angelo
A
Lupo
D000970:Antineoplastic Agents / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000378:metabolism*; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis* / Q000235:genetics; D016213:Cyclins / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D019073:HT29 Cells; D006801:Humans; D020935:MAP Kinase Signaling System; D009154:Mutation; D009281:Naphthalenes / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D016329:Sp1 Transcription Factor / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D009281:Naphthalenes; D016329:Sp1 Transcription Factor; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C548360:cladosporol; D051357:Cyclin-Dependent Kinase 2