ABSTRACT
Accumulating evidence supports the remarkable presence at the membrane surface of cancer cells of proteins, which are normally expressed in the intracellular compartment. Although these proteins, referred to as externalized proteins, represent a highly promising source of accessible and druggable targets for cancer therapy, the mechanisms via which they impact cancer biology remain largely unexplored. The aim of this study was to expose an externalized form of cytokeratin 8 (eK8) as a key player of colorectal tumorigenesis and characterize its mode of action. To achieve this, we generated a unique antagonist monoclonal antibody (D-A10 MAb) targeting an eight-amino-acid-long domain of eK8, which enabled us to ascertain the pro-tumoral activity of eK8 in both KRAS-mutant and wild-type colorectal cancers (CRC). We showed that this pro-tumoral activity involves a bidirectional eK8-dependent control of caspase-mediated apoptosis in vivo and of the plasminogen-induced invasion process in cellulo. Furthermore, we demonstrated that eK8 is anchored at the plasma membrane supporting this dual function. We, therefore, identified eK8 as an innovative therapeutic target in CRC and provided a unique MAb targeting eK8 that displays anti-neoplastic activities that could be useful to treat CRC, including those harboring KRAS mutations.
ABSTRACT
Interleukin-18, a pleiotropic cytokine is a member of the IL-1 family and has multiple immunoregulatory functions. IL-18 action leads to IFNgamma production by NK or T cells, induces Th1 differentiation and suppresses IgE synthesis by B cells when acting on responding cells in association with IL-12. At present two subunits of the IL-18R have been characterized: IL-18 Ralpha and IL-18 Rbeta. Both receptors belong to the IL-1R family. IL-18 Ralpha has been described as the ligand-binding chain and IL-18 Rbeta as the signal-transduction chain. Three monoclonal antibodies (mAbs) submitted to the HLDA8 workshop, designated H44 (80438), B-B46 (80228), and B-E43 (80232) were evaluated. The mAb specificity was determined by ELISA using coated recombinant IL-18 Ralpha or IL-18 Rbeta. Cell staining was analyzed by flow cytometry. A positive staining with the mAb B-E43 or H44 demonstrated that IL-18 Ralpha is expressed on several myeloid cell lines. No positive cell staining was observed with the anti IL-18 Rbeta mAb B-B46. The mAb biological activity was studied using the cell line KG1. A downmodulation of IFNgamma production was observed with the mAbs B-B46 (80228) and B-E43 (80232).
