The slides were fixed with 2% formaldehyde in PBS and processed
for fluorescence microscopy with a Zeiss 466301 microscope. An Olympus Camedia C5060 was used for colour photography. Anchorage independent growth assay A 2 ml of 0.5% agarose gel in RPMI at 10% FCS was poured in each 35 mm well of a plastic plate and allowed to solidify at room temperature for 2 hours in a laminar flow hood. Then a 0.5 ml of a 0.33% agarose gel containing 250 cells was overlaid on top, allowed to stand for 30′ at +4°C and subsequently incubated at 37°C. After a 12–16 days incubation the cell growth was evaluated by bright field find more observation under low magnification and growing colonies photographed. Western blot analysis Immunoblot analysis was performed as previously described [36]. Cell lysis was carried out at 4°C by sonication for 1 min in Media I (0.32 M sucrose, 10 mM Tris-HCl, pH 8.0, 0.1 mM MgCl2, 0.1 mM EDTA, 1 mM phenyl-methyl-sulfonyl-fluoride (PMSF) and 10 μg/ml aprotinine) and lysates were stored at -70°C until use. Protein
content was determined by the Bio-Rad Protein Assay (Bio-Rad Laboratories Srl, click here Segrate, Italy). Proteins were separated by 12% SDS-PAGE and transferred to PVDF membranes in 25 mM Tris, 92 mM glycine containing 20% (v/v) methanol at 110 V for 1 h. Following transfer, membranes were placed for 1 h in blocking buffer (bovine serum albumin 3% in T-TBS). For tyrosinase detection, membranes were probed first with 10 ml of blocking buffer containing goat anti-tyrosinase polyclonal antibody (Santa Cruz Biotechnology Inc., CA) (1:500) for Grape seed extract 1 h at 27°C, followed by 10 ml of blocking buffer containing horseradish peroxidase-conjugated rabbit anti-goat IgG (1:5000) for 60 min at 27°C. Protein bands were visualized using luminol-based enhanced Foretinib chemo-luminescence as described by the manufacturer (Perkin-Elmer
Life Sciences). Densitometric analysis was performed using Scion Image (PC version of Macintosh-compatible NIH Image). Tyrosinase activity assay Cell monolayers were treated with trypsin/EDTA; suspensions washed with PBS and pellets recovered by centrifugation at 250 × g for 10 min. Cells were lysed by sonication (six times for 5 seconds each) in 0.5 ml of 0.1 M Na-phosphate buffer, pH 6.8, containing 0.1 mM PMSF. After centrifugation at 7,000 × g for 10 min, tyrosinase activity was assayed on supernatant according to Iozumi et al. [37]. Fifty μl of sample was incubated in 0.5 ml of a reaction mixture containing 0.1 mM L-tyrosine, 2 μCi per ml of [3H] tyrosine, 0.1 mM L-DOPA and 0.1 mM PMSF in sodium phosphate buffer 0.1 M (pH 6.8). After 2 h at 37°C, the reaction was terminated by the addition of 1 ml of charcoal (10% wt/vol in 0.1 N HCl). Samples were centrifuged at 2000 g for 10 min, the supernatant was removed and mixed with scintillation cocktail, and radioactivity was determined using the LS 6500 scintillation system (Beckman, U.S.A.).