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Silibinin inhibits renal cell carcinoma via mechanisms that are independent of insulin‐like growth factor‐binding protein 3
Author(s) -
Cheung Catherine W.,
Vesey David A.,
Nicol David L.,
Johnson David W.
Publication year - 2007
Publication title -
bju international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.773
H-Index - 148
eISSN - 1464-410X
pISSN - 1464-4096
DOI - 10.1111/j.1464-410x.2007.06571.x
Subject(s) - silibinin , viability assay , cell growth , microbiology and biotechnology , apoptosis , chemistry , endocrinology , biology , biochemistry , cancer research
OBJECTIVE To investigate whether silibinin, a flavonoid antioxidant with anticancer properties that inhibits cellular growth via the up‐regulation of insulin‐like growth factor binding protein 3 (IGFBP‐3), inhibits renal cell carcinoma (RCC) growth via the IGFBP‐3 pathway. MATERIALS AND METHODS Cell morphology, DNA synthesis by thymidine incorporation, viability assessed by 3,4,5 dimethylthiazol‐2,5 diphenyl tetrazolium bromide (MTT) assays, trypan blue exclusion, and lactate dehydrogenase (LDH) release, apoptosis and IGFBP‐3 protein (Western blotting) were evaluated in silibinin‐treated SN12K1 cells (a cell line derived from metastatic RCC) in the presence or absence of IGFBP‐3 immunoneutralization. RESULTS Silibinin suppressed SN12K1 DNA synthesis at 24 and 48 h incubation by a mean ( sd ) of at least 68 (10)% of the control values at ≥2 µmol/L ( P < 0.05). At high concentrations (>80 µmol/L) cell viability was compromised, as shown by decreased MTT uptake of 62 (10)% of control values ( P < 0.001), reduced cell counts of ≥77 (9)% of control values ( P < 0.05), elevated LDH release of 212 (49)% of control ( P < 0.001), and the presence of necrotic and apoptotic cells on immunofluorescence staining. Removing endogenous IGFBP‐3 by neutralizing with anti‐IGFBP‐3 antibody increased DNA synthesis by 240 (35)% of control for 24 h, ( P < 0.001). However, on Western blot analysis of IGFBP‐3 levels in conditioned media incubated in the presence of silibinin there was down‐regulation of protein expression. CONCLUSION Silibinin suppresses SN12K1 cell growth and, at high doses, increases cell death. These effects are independent of IGFBP‐3.