The transfected cells were cultured with GEM for zero (untreated), one, four or 24?hours. of the protein to the plasma membrane. Other molecules associated with immune-sensitivity, such as TRAIL receptors (TRAILRs) and NKG2D ligands have also been reportedly induced by chemotherapies in various cancer types15,16. The work presented here aims to show whether chemotherapies, including the antimetabolite nucleoside analogue gemcitabine (GEM) which is primarily used in pancreatic, non-small cell lung, breast and ovarian cancers and has been used experimentally in colorectal cancers, can increase expression of CD95 on the surface of a panel of tumour cell lines and whether any increase is functional in terms of induced-cell death. Moreover, in-line with recent reports additional signs of immune sensitivity will be explored in terms of expression of death receptors and immune effector ligands. Materials and Methods Cell Culture The human cancer cell lines; A549 (lung), HCT116 (colon) and MCF-7 (breast) (Public Health England, Porton Down, UK), were grown in complete medium, DMEM (Sigma-Aldrich, Dorset, UK), supplemented with 10% foetal bovine serum (FBS) Vcam1 (Invitrogen, Paisley, UK), 2?mM and 1% penicillin/streptomycin (Sigma). For all experiments cells were seeded at 1??105 cells/ml and allowed to attach overnight before addition of drugs or other reagents for 24?hours. Drugs, Inhibitors and CD95 cross-linking reagents GEM, oxaliplatin (OXP) and cyclophosphamide (CPM) (Sigma) were reconstituted in phosphate buffered saline (PBS) (Sigma). ERK signalling was inhibited with U0126 (New England Biolabs, Hitchin, UK) while SP600125 (Sigma) was used to block the JNK pathway. For experiments involving ligation of CD95, his-tagged CD95L was used at 50?ng/ml with AZ-20 a cross-linking polyhistidine monoclonal antibody (both R & D Biosystems, Abingdon, UK) at 3?g/ml. Ligation of CD95 was AZ-20 blocked using an antibody antagonistic to CD95 (Prospec, East Brunswick, USA). Flow Cytometric Analysis Cells were stained with fluorochrome-conjugated antibodies specific for CD95 (Biolegend, London, UK); ULBP2/5/6 (R & D) and TRAILR 1 and 2 (Biolegend). MICA/B was stained using an unconjugated primary antibody and anti-species secondary antibody (both Biolegend). Cells were washed prior to resuspending in Cellfix (Becton Dickinson AZ-20 (BD), Oxford, UK). Acquisition of data was performed within 24?hours using an LSRII flow cytometer (BD Biosciences) by gating on live cells and measuring median fluorescence intensity (MFI). MTT Assay The methylthiazoletetrazolium (MTT) assay was used to measure cell number. Briefly, 0.4?mg/ml MTT (Sigma) was added to cell cultures and plates incubated for 60?minutes. After this time, medium was aspirated AZ-20 off, 200?l DMSO added to each well and plates agitated gently for before measuring optical density at 540?nm using a microplate reader (Dynex-MRX II, Dynex Technologies Ltd. West Sussex, UK)). Illumina microarrays RNA was isolated from HCT116 cells using the Qiagen (Manchester, UK) mini-kit protocol following manufacturers instructions. Microarrays were performed by Dr Jayne Dennis at the St. Georges, University of London Biomics Centre. Biotinylated cRNA was generated from 100?ng total RNA using the Illumina TotalPrep RNA Amplification Kit (Applied Biosystems, Warrington, UK) according to manufacturers instructions. Equal amounts (750?ng) of cRNA were hybridised to the Illumina human HT12-v3 arrays for 18?hours and subsequently processed according to manufacturers instructions before scanning on an Illumina BeadArray Reader. The image data were processed using default values in GenomeStudio v2009.1 with imputation of missing data, before loading onto GeneSpring v9.0 for data normalisation and filtering. Cignal Reporter Assay The Cignal Finder? RTK 10-Pathway Reporter Array (Qiagen) was used to assess activation of various signalling pathways in HCT116 cells. The manufacturers suggested protocol was followed with some modifications. Briefly, 50?l of Opti-MEM? medium was added to each well of the array plate to resuspend the signalling-pathway-related transcription-factor-responsive reporter and control constructs. Then, 0.5?l lipofectamine? LTX? in 50?l Opti-MEM? medium was added to the plate before incubating for 20?minutes at room temperature. HCT116 tumour cell suspension was then added at 3.5??104 cells/ml. The plate was incubated overnight, before culturing for a further 24?hours with or without the addition of GEM. The transfected cells were cultured with GEM for zero (untreated), one, four or 24?hours. Pathway-specific transcription factor activity in response to GEM was determined using the Dual-Luciferase? Reporter Assay System (Promega, Southampton, UK) following manufacturers instructions. Luminescent activity from each sample was quantified with a Promega GloMax? Multi?+?Detection Reader. Results Chemotherapy induces expression of CD95 in tumour cell lines Our previous studies showed an increase in expression of MHC class I on selected tumour cell lines in response to relatively low concentrations of GEM. Also observed AZ-20 were alterations in other components of the antigen processing machinery17 suggesting that a coordinated alteration of immunophenotype is occurring in GEM-treated cells..