Silibinin Inhibits Inflammatory and Angiogenic Attributes in Photocarcinogenesis in SKH-1 Hairless Mice

Abstract

Sunscreens partially filter UVB and, therefore, could partially prevent skin cancer; however, efficient approaches are desired to effectively prevent photocarcinogenesis. It is hypothesized that nontoxic pharmacologically active natural compounds can increase photoprotective effects. Our completed studies suggest that silibinin, a bioactive phytochemical, strongly prevents photocarcinogenesis; however, its mechanism is not fully understood. Herein, for the first time, we used a clinically relevant UVB dose (30 mJ/cm 2 /day) to examine the photoprotective effect and associated mechanisms of silibinin in SKH1 hairless mice. Topical or dietary silibinin treatment caused a strong protection against photocarcinogenesis in terms of delay in tumor appearance, multiplicity, and volume. Analyses of normal skin, uninvolved skin from tumor-bearing mice, and skin tumors showed a statistically significant decrease (P < 0.05-0.001) in inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) levels by silibinin. Concomitantly, phospho-signal transducers and activators of transcription 3 (Tyr 705 ) and phospho-p65(Ser 536 ) were also decreased by silibinin, which are potential up-stream regulators of iNOS and COX-2. Simultaneously, silibinin also decreased UVB-caused increase in cell proliferation and microvessel density. In tumors, hypoxia-inducible factor 1A (HIF-1A) and vascular endothelial growth factor protein levels were decreased by silibinin. Further analysis showed that silibinin inhibited UVB-caused phosphorylation and nuclear translocation of STAT3 and p65, as well as nuclear factor KB (NF-KB) DNA binding activity. Together, these results suggest that silibinin causes a strong protective effect against photocarcinogenesis via down-regulation of inflammatory and angiogenic responses, involving HIF-1A, STAT3, and NF-KB transcription factors, as well as COX2 and iNOS. [Cancer Res 2007;67(7):3483-91]

Chemopreventive effects of silymarin and silibinin on N-butyl-N-(4-hydroxybutyl) nitrosamine–induced urinary bladder carcinogenesis in male ICR mice

“…Immunohistochemical Analysis Paraffin-embedded, 5-Am-thick sections were deparaffinized and stained with primary antibodies anti -proliferating cell nuclear antigen (PCNA; DAKO) and anti-survivin (Novus) followed by 3,3-diaminobenzidine staining as recently published (15). The immunostained cells were quantified by counting the brown cells and the total number of cells at five randomly selected fields at Â400 magnification.…”

“…Immunoblot Analysis of Tissue Lysates Total tissue lysate and nuclear lysate were prepared as earlier published (15). Protein concentration in tissue lysates was determined with Bio-Rad detergent-compatible protein assay kit (Bio-Rad Laboratories) by the Lowry method and 50 to 70 Ag of protein were then subjected to immunoblot analysis as previously described (15).…”

“…Protein concentration in tissue lysates was determined with Bio-Rad detergent-compatible protein assay kit (Bio-Rad Laboratories) by the Lowry method and 50 to 70 Ag of protein were then subjected to immunoblot analysis as previously described (15). Membranes were probed with different primary antibodies for PCNA, cyclin D1, phospho -extracellular signal -regulated kinase (ERK)-1/2, total ERK1/2, cleaved caspase-3, cleaved poly(ADP-ribose) polymerase, survivin, phospho -nuclear factor nB (NF-nB) p65 (Ser 276 ), phospho -NF-nB p65 (Ser 536 ), and total NF-nB p65 (Cell Signaling).…”

Chemopreventive and Chemotherapeutic Effects of Intravesical Silibinin against Bladder Cancer by Acting on Mitochondria

“…1A). Accumulating evidence indicates that silibinin has anticancer activity in various tumor cells, including cancers of prostate (5)(6)(7)(8)(9), breast (10,11), skin (12), colon (13), lung (14), kidney (15,16), and bladder (17)(18)(19)(20). There is increasing interest in elucidating the mechanisms of action for silibinin as an effective agent for chemoprevention and chemotherapy against various types of cancers.…”

Topical delivery of silymarin constituents via the skin route

“…Both UVA and UVB cause wavelength-dependent damage to human skin including skin cancer, whose incidence is dramatically increasing [8] . Recent studies showed that silymarin constituents could strongly protect against photocarcinogenesis and inhibit UVB and chemical tumor promoterinduced skin inflammation and edema [1,[9][10][11] . Silymarin also attenuates UVA-induced damage to human keratinocytes [12] .…”