Diana Zurlo1, Gemma Assante2, Salvatore Moricca3, Vittorio Colantuoni1, Angelo Lupo4. 1. Dipartimento di Scienze e Tecnologie, Università del Sannio, via Port'Arsa 11, 82100 Benevento, Italy. 2. Dipartimento di Patologia Vegetale, Università degli Studi di Milano, via Celoria, 2, 20133 Milano, Italy. 3. Dipartimento di Scienze delle Produzioni Agroalimentari e dell'Ambiente (DiSPAA), Università degli Studi di Firenze, Piazzale delle Cascine, 2850144 Firenze, Italy. 4. Dipartimento di Scienze e Tecnologie, Università del Sannio, via Port'Arsa 11, 82100 Benevento, Italy. Electronic address: lupo@unisannio.it.
Abstract
BACKGROUND: Cladosporol A, a secondary metabolite from Cladosporium tenuissimum, exhibits antiproliferative properties in human colorectal cancer cells by modulating the expression of some cell cycle genes (p21(waf1/cip1), cyclin D1). METHODS: PPARγ activation by cladosporol A was studied by overexpression and RNA interference assays. The interactions between PPARγ and Sp1 were investigated by co-immunoprecipitation and ChIp assays. β-Catenin subcellular distribution and β-catenin/TCF pathway inactivation were analyzed by western blot and RTqPCR, respectively. Cladosporol A-induced β-catenin proteasomal degradation was examined in the presence of the specific inhibitor MG132. RESULTS: Cladosporol A inhibits cell growth through upregulation of p21(waf1/cip1) gene expression mediated by Sp1-PPARγ interaction. Exposure of HT-29 cells to cladosporol A causes β-catenin nuclear export, proteasome degradation and reduced expression of its target genes. Upon treatment, PPARγ also activates E-cadherin gene at the mRNA and protein levels. CONCLUSION: In this work we provide evidence that PPARγ mediates the anti-proliferative action of cladosporol A in colorectal cancer cells. Upon ligand activation, PPARγ interacts with Sp1 and stimulates p21(waf1/cip1) gene transcription. PPARγ activation causes degradation of β-catenin and inactivation of the downstream target pathway and, in addition, upregulates E-cadherin expression reinforcing cell-cell interactions and a differentiated phenotype. GENERAL SIGNIFICANCE: We elucidated the molecular mechanisms by which PPARγ mediates the anticancer activity of cladosporol A.
BACKGROUND:Cladosporol A, a secondary metabolite from Cladosporium tenuissimum, exhibits antiproliferative properties in humancolorectal cancer cells by modulating the expression of some cell cycle genes (p21(waf1/cip1), cyclin D1). METHODS: PPARγ activation by cladosporol A was studied by overexpression and RNA interference assays. The interactions between PPARγ and Sp1 were investigated by co-immunoprecipitation and ChIp assays. β-Catenin subcellular distribution and β-catenin/TCF pathway inactivation were analyzed by western blot and RTqPCR, respectively. Cladosporol A-induced β-catenin proteasomal degradation was examined in the presence of the specific inhibitor MG132. RESULTS:Cladosporol A inhibits cell growth through upregulation of p21(waf1/cip1) gene expression mediated by Sp1-PPARγ interaction. Exposure of HT-29 cells to cladosporol A causes β-catenin nuclear export, proteasome degradation and reduced expression of its target genes. Upon treatment, PPARγ also activates E-cadherin gene at the mRNA and protein levels. CONCLUSION: In this work we provide evidence that PPARγ mediates the anti-proliferative action of cladosporol A in colorectal cancer cells. Upon ligand activation, PPARγ interacts with Sp1 and stimulates p21(waf1/cip1) gene transcription. PPARγ activation causes degradation of β-catenin and inactivation of the downstream target pathway and, in addition, upregulates E-cadherin expression reinforcing cell-cell interactions and a differentiated phenotype. GENERAL SIGNIFICANCE: We elucidated the molecular mechanisms by which PPARγ mediates the anticancer activity of cladosporol A.
Authors: Sabrin R M Ibrahim; Sana A Fadil; Haifa A Fadil; Bayan A Eshmawi; Shaimaa G A Mohamed; Gamal A Mohamed Journal: Toxins (Basel) Date: 2022-02-19 Impact factor: 4.546