Finally, the beads were probed with Streptavidin R-Phycoerythrin for 30 min with mixing at 10 μg/mL in BSA Block, washed 6 × 250 μL briefly with TBS-T and scanned in the BeadXpress™ reader as described above. Straight sandwich immunoassays for GDF15 and CEA (but no TAA detection) were performed in the same manner except that the Anti-Human IgG Fluorescent (DyLight 649) Secondary selleck chemical Antibody probing was omitted. The p53 autoantibody

(TAA) ELISA was performed similar to published reports (Zhang et al., 2003). Briefly, the recombinant protein was diluted to 0.5 ng/μL in PBS and 100 μL used to passively coat each well of a 96-well polystyrene microtiter plate (Nunc-Immuno 96-Well Plates, PolySorp). Alectinib Plates were then washed with TBS-T and pre-treated with BSA Block. Sera/plasma samples were diluted to 1/100 in BSA Block and 100 μL added to the wells for 30 min incubation. Detection was with an HRP conjugated mouse anti-human IgG antibody followed by development with SureBlue TMB 1-Component Microwell Peroxidase Substrate. The CEA sandwich ELISA was performed according to the manufacturer’s instructions (see Section 2.1: Supplies and Reagents). Recombinant proteins were directly and covalently attached to VeraCode™ beads using standard

carbodiimide (EDC) chemistries to link amine groups on the proteins to the carboxyl groups on the beads. In the case of cell-free expressed proteins, they were affinity captured directly from the crude expression reactions by their C-terminal SBP-Tag (Keefe et al., 2001) onto streptavidin coated VeraCode™ beads. For preparation of streptavidin coated VeraCode™ beads, optimal results (data not shown) were obtained by first attaching a biotin-amine

linker to the carboxyl beads using the aforementioned carbodiimide chemistry, followed by attachment of (tetrameric) streptavidin to the biotinylated beads. With either recombinant or cell-free proteins, MycoClean Mycoplasma Removal Kit successful attachment of the proteins to the beads is readily verified (quality controlled) by detection of epitope or fusion tags present in the proteins. An example of this quality control measure is shown in Supplementary Fig. 1 with the p53 and MAP4K4 proteins. Detection of recombinant proteins was via a GST fusion tag in this case and cell-free proteins via their N-terminal VSV-G epitope tag. With the recombinant proteins, signal to background ratios were 250:1 and 125:5 for p53 and MAP4K4 respectively, and for the cell-free proteins 34:1 and 87:1 (note that all DNA clones used to produce cell-free proteins were sequence verified). First, human p53 (TP53) (Koziol et al., 2003, Saleh et al., 2004, Nozoe et al., 2007 and Reuschenbach et al., 2009) was validated as a positive control TAA using a conventional ELISA to detect autoantibodies in the serum/plasma of 47 healthy (normal) and 47 colorectal cancer patient samples (94 total patient samples) (Fig. 2, top panel).