title: Angiopreventive efficacy of pure flavonolignans from milk thistle extract against prostate cancer: targeting VEGF-VEGFR signaling.
abstract: The role of neo-angiogenesis in prostate cancer (PCA) growth and metastasis is well established, but the development of effective and non-toxic pharmacological inhibitors of angiogenesis remains an unaccomplished goal. In this regard, targeting aberrant angiogenesis through non-toxic phytochemicals could be an attractive angiopreventive strategy against PCA. The rationale of the present study was to compare the anti-angiogenic potential of four pure diastereoisomeric flavonolignans, namely silybin A, silybin B, isosilybin A and isosilybin B, which we established previously as biologically active constituents in Milk Thistle extract. Results showed that oral feeding of these flavonolignans (50 and 100 mg/kg body weight) effectively inhibit the growth of advanced human PCA DU145 xenografts. Immunohistochemical analyses revealed that these flavonolignans inhibit tumor angiogenesis biomarkers (CD31 and nestin) and signaling molecules regulating angiogenesis (VEGF, VEGFR1, VEGFR2, phospho-Akt and HIF-1α) without adversely affecting the vessel-count in normal tissues (liver, lung, and kidney) of tumor bearing mice. These flavonolignans also inhibited the microvessel sprouting from mouse dorsal aortas ex vivo, and the VEGF-induced cell proliferation, capillary-like tube formation and invasiveness of human umbilical vein endothelial cells (HUVEC) in vitro. Further studies in HUVEC showed that these diastereoisomers target cell cycle, apoptosis and VEGF-induced signaling cascade. Three dimensional growth assay as well as co-culture invasion and in vitro angiogenesis studies (with HUVEC and DU145 cells) suggested the differential effectiveness of the diastereoisomers toward PCA and endothelial cells. Overall, these studies elucidated the comparative anti-angiogenic efficacy of pure flavonolignans from Milk Thistle and suggest their usefulness in PCA angioprevention.
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Denver, Aurora, Colorado, United States of America.
authors.forename: Gagan
authors.initials: G
authors.lastname: Deep
authors.forename: Subhash Chander
authors.initials: SC
authors.lastname: Gangar
authors.forename: Subapriya
authors.initials: S
authors.lastname: Rajamanickam
authors.forename: Komal
authors.initials: K
authors.lastname: Raina
authors.forename: Mallikarjuna
authors.initials: M
authors.lastname: Gu
authors.forename: Chapla
authors.initials: C
authors.lastname: Agarwal
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: Oberlies
authors.forename: Rajesh
authors.initials: R
authors.lastname: Agarwal
mesh_terms: D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D044947:Flavonolignans / Q000737:chemistry / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D020944:Silybum marianum / Q000737:chemistry*; D011471:Prostatic Neoplasms / Q000188:drug therapy*; D000077385:Silybin; D012838:Silymarin / Q000031:analogs & derivatives / Q000737:chemistry / Q000627:therapeutic use; D023041:Xenograft Model Antitumor Assays
chemical_list: D044947:Flavonolignans; D012838:Silymarin; D000077385:Silybin; C523198:isosilybin A