Mesothelin, is derived from a 70kD precursor that also includes Megakaryocyte Potentiating Factor (MPF) (1-3). The 70kD precursor is expressed on the cell surface where it is cleaved at a dibasic proteolytic site to release the 32kD glycosylated MPF (3, 4). MPF is a cytokine that potentiates IL-3 induced megakaryocyte colony formation (2, 5). The term Mesothelin refers to the 40kD glycosylated protein which remains attached to the cell surface via a GPI linkage. Alternate splicing generates additional Mesothelin isoforms that have either an 8aa insertion following Ser408 or a substituted C-terminal region with no GPI anchor (6). This recombinant human Mesothelin lacks the 8aa insertion, and within aa296-580 it shares 59% sequence identity with mouse and rat Mesothelin. Mesothelin is normally expressed on mesothelial cells in the pleura, pericardium, and peritoneum as well as in the developing and postnatal pancreas (1, 7). It is up-regulated in mesotheliomas and a range of carcinomas and adenomas (8-11). Mesothelin promotes tumor cell proliferation, migration, anchorage-independent growth, and tumor progression (10, 12). It is coexpressed with the tumor antigen CA125/MUC16 on advanced ovarian adenocarcinomas and interacts with this molecule to support cell adhesion (13). A soluble form of Mesothelin is released from tumor cells into the serum or tissue effusions (11, 14, 15). Source: Recombinant corresponding to aa296-580 from human Mesothelin, fused with 6-His tag at C-terminal, expressed in mouse myeloma cell line, NSO. Molecular Weight: ~33kD Biological Activity: Measured by its binding ability in a functional ELISA. When recombinant human CA125 is coated at 2ug/ml (100ul/well), the concentration of recombinant human Mesothelin that produces 50% of the optimal binding response is found to be ~0.5-2.5ug/ml. Storage and Stability: Lyophilized powder may be stored at -20C. Stable for 12 months at -20C. Reconstitute with PBS. Aliquot to avoid repeated freezing and thawing. Store at -20C. Reconstituted product is stable for 6 months at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.
