title: Silibinin inhibits aberrant lipid metabolism, proliferation and emergence of androgen-independence in prostate cancer cells via primarily targeting the sterol response element binding protein 1.
abstract: Prostate cancer (PCA) kills thousands of men every year, demanding additional approaches to better understand and target this malignancy. Recently, critical role of aberrant lipogenesis is highlighted in prostate carcinogenesis, offering a unique opportunity to target it to reduce PCA. Here, we evaluated efficacy and associated mechanisms of silibinin in inhibiting lipid metabolism in PCA cells. At physiologically achievable levels in human, silibinin strongly reduced lipid and cholesterol accumulation specifically in human PCA cells but not in non-neoplastic prostate epithelial PWR-1E cells. Silibinin also decreased nuclear protein levels of sterol regulatory element binding protein 1 and 2 (SREBP1/2) and their target genes only in PCA cells. Mechanistically, silibinin activated AMPK, thereby increasing SREBP1 phosphorylation and inhibiting its nuclear translocation; AMPK inhibition reversed silibinin-mediated decrease in nuclear SREBP1 and lipid accumulation. Additionally, specific SREBP inhibitor fatostatin and stable overexpression of SREBP1 further confirmed the central role of SREBP1 in silibinin-mediated inhibition of PCA cell proliferation and lipid accumulation and cell cycle arrest. Importantly, silibinin also inhibited synthetic androgen R1881-induced lipid accumulation and completely abrogated the development of androgen-independent LNCaP cell clones via targeting SREBP1/2. Together, these mechanistic studies suggest that silibinin would be effective against PCA by targeting critical aberrant lipogenesis.
authors.affiliation: Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, USA. School of Life Sciences, Jawaharlal Nehru University, India.
authors.forename: Dhanya K
authors.initials: DK
authors.lastname: Nambiar
authors.affiliation: Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, USA. University of Colorado Cancer Center, Aurora, CO, USA.
authors.forename: Gagan
authors.initials: G
authors.lastname: Deep
authors.affiliation: School of Life Sciences, Jawaharlal Nehru University, India.
authors.forename: Rana P
authors.initials: RP
authors.lastname: Singh
authors.affiliation: Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, USA. University of Colorado Cancer Center, Aurora, CO, USA.
authors.forename: Chapla
authors.initials: C
authors.lastname: Agarwal
authors.affiliation: Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, USA. University of Colorado Cancer Center, Aurora, CO, USA.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Agarwal
mesh_terms: D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D050356:Lipid Metabolism / Q000187:drug effects; D008297:Male; D015741:Metribolone / Q000037:antagonists & inhibitors / Q000494:pharmacology; D058990:Molecular Targeted Therapy; D010766:Phosphorylation; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D064129:Prostatic Neoplasms, Castration-Resistant / Q000517:prevention & control; D011725:Pyridines / Q000494:pharmacology; D000077385:Silybin; D012838:Silymarin / Q000494:pharmacology*; D051780:Sterol Regulatory Element Binding Protein 1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D051782:Sterol Regulatory Element Binding Protein 2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism; D013844:Thiazoles / Q000494:pharmacology; D014162:Transfection
chemical_list: D011725:Pyridines; C497387:SREBF1 protein, human; C497390:SREBF2 protein, human; D012838:Silymarin; D051780:Sterol Regulatory Element Binding Protein 1; D051782:Sterol Regulatory Element Binding Protein 2; D013844:Thiazoles; C545733:fatostatin; D015741:Metribolone; D000077385:Silybin