Therapeutic value of orally administered silibinin in renal cell carcinoma: manipulation of insulin-like growth factor binding protein-3 levels.
OBJECTIVE
To investigate if the feeding of silibinin (an anticancer flavonoid) to mice inhibits in vivo renal cell carcinoma (RCC) growth via changes in insulin-like growth factor binding protein-3 (IGFBP-3) levels.


METHODS
Male severe combined immunodeficiency disease (SCID) mice (7 weeks old), with left kidneys injected with 1 million SN12K1 cells, were fed a silibinin-containing diet (0.1%, 0.2% and 0.4% w/w) or control AIN-93G diet for 39 days from 1 day after tumour engraftment.


RESULTS
There was a reduction in tumour deposits and tumour kidney weight in SCID mice fed with a 0.4% silibinin-containing diet compared to those fed the control diet. Mice with tumour injection (silibinin or control-diet group) had constant total body weight and food consumption. The mean plasma and tumourous kidney silibinin concentrations, as measured by high-pressure liquid chromatography-tandem mass spectrometry, increased with escalating doses of silibinin. Using real-time polymerase chain reaction and enzyme-linked immunosorbent assay, the mean tissue IGFBP-3 mRNA (in SN12K1-implanted kidney) and plasma IGFBP-3 levels increased in mice fed with 0.1% silibinin (tumour IGFBP-3 mRNA levels, 156% higher vs control-diet group, P = 0.007; and plasma IGFBP-3 levels, 61% higher vs control-diet group, P = 0.002) but not in mice fed with the higher silibinin pellet strengths.


CONCLUSIONS
Oral administration of silibinin suppressed local and metastatic tumour growth in vivo in an orthotopic xenograft model of RCC. This anti-neoplastic action of silibinin might involve IGFBP-3. The exact mechanism through which IGFBP-3 promotes silibinin's anticancer effects warrants further investigation.
Cheung
Catherine W
CW
Department of Medicine, University of Queensland, Brisbane, Queensland, Australia.
Taylor
Paul J
PJ
Kirkpatrick
Carl M J
CM
Vesey
David A
DA
Gobe
Glenda C
GC
Winterford
Clay
C
Nicol
David L
DL
Johnson
David W
DW
D000284:Administration, Oral; D000704:Analysis of Variance; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage*; D000975:Antioxidants / Q000008:administration & dosage*; D002292:Carcinoma, Renal Cell / Q000188:drug therapy*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism*; D007680:Kidney Neoplasms / Q000188:drug therapy*; D008297:Male; D051379:Mice; D016513:Mice, SCID; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077385:Silybin; D012838:Silymarin / Q000008:administration & dosage
D000970:Antineoplastic Agents; D000975:Antioxidants; D018972:Insulin-Like Growth Factor Binding Protein 3; D012838:Silymarin; D000077385:Silybin