Louis, MO) to 1–15 μmol/L. HCC cell viability was determined at 72 hours after addition of 1–15 μmol/L sorafenib or DMSO by WST-8 assay using cell count reagent sulforaphane (Nacalai Tesque, Kyoto, Japan) as previously described.20 The small interfering RNA (siRNA) method was used

to knockdown ADAM9 as previously described.20 At 24 hours after transfection, the cells were analyzed for specific depletion of the messenger RNA (mRNA) of ADAM9 by real-time reverse transcription polymerase chain reaction (RT-PCR) according to the manufacturer’s instructions (Applied Biosystems, Foster City, HSP inhibitor CA). The following siRNAs were used: ADAM9, 5′-UGUCCAAACACAUUAAUCCCGCCUG-3′; scramble control, 5′-UGUCGCACAAACACUUAACUCCCUG-3′. HCC cells were cultured with tumor necrosis factor-α protease inhibitor-I (TAPI-I, 50 μmol/L; Calbiochem, San Diego, CA) or sorafenib (1 μmol/mL) for 24 hours and the supernatants were harvested. The supernatants of cultured HCC cells were harvested at 24 hours after transfection with siRNA. The levels of soluble MICA were determined by DuoSet MICA enzyme-linked immunosorbent assay (ELISA) kit (R&D Systems, Minneapolis, MN). For the detection selleck chemical of membrane-bound MICA, cells were incubated with anti-MICA antibody (Ab) (Santa Cruz Biotechnology, Santa Cruz, CA) and stained with phycoerythrin-goat anti-mouse

immunoglobulin (Ig) (Beckman Coulter, Fullerton, CA) as a secondary reagent and then subjected to flow cytometric analysis using a FACScan flow cytometer (Becton Dickinson, San Jose, CA). Total RNA was isolated using the RNeasy Mini Kit (Qiagen K.K., Tokyo, Japan), and was reverse transcribed using SuperScript III First-Strand Synthesis System (Invitrogen, Carlsbad, CA). The mRNA levels were evaluated using ABI-Prism 7900 Sequence Detection System (Applied Biosystems). Ready-to-use assays (Applied Biosystems)

were used for the quantification of ADAM9 (Hs00177638_m1), and β-actin (Hs99999903_m1) mRNAs according to the manufacturer’s instructions. β-Actin mRNA from each sample was quantified as an endogenous control of internal RNA. Peptides of 20 amino acid residues either partially overlapping each other, covering the α3 domain to the C-terminal end of MICA were synthesized by Sigma. Each peptide substrate (30 μM) was incubated with 50 nM of recombinant ADAM9 in a buffer containing 10 mM HEPES (pH 7.2) and 0.0015% Brij (Sigma). After digestion, the samples were passed over a C18 media (ZipTipC18; Millipore, Billerica, MA), eluted with acetonitrile, and analyzed by matrix-assisted laser desorption/ionization–time of flight/mass spectrometry (MALDI-TOF/MS) to determine the masses of the products and thereby the cleavage site recognized by ADAM9. An expression vector of MICA, pcDNA-MICA, was constructed by using specific complementary DNA (cDNA) from the human hepatoma-derived cell line, Huh-7, as described.