To identify new potential targets in oncology, functional approaches were developed using tumor cells as immunogens to select monoclonal antibodies targeting membrane receptors involved in cell proliferation. For that purpose cancer cells were injected into mice and resulting hybridomas were screened for their ability to inhibit cell proliferation in vitro. Based on this functional approach coupled to proteomic analysis, a monoclonal antibody specifically recognizing the human junctional adhesion molecule-A (JAM-A) was defined. Interestingly, compared to both normal and tumor tissues, we observed that JAM-A was mainly overexpressed on breast, lung and kidney tumor tissues. In vivo experiments demonstrated that injections of anti-JAM-A antibody resulted in a significant tumor growth inhibition of xenograft human tumors. Treatment with monoclonal antibody induced a decrease of the Ki67 expression and downregulated JAM-A levels. All together, our results show for the first time that JAM-A can interfere with tumor proliferation and suggest that JAM-A is a potential novel target in oncology. The results also demonstrate that a functional approach coupled to a robust proteomic analysis can be successful to identify new antibody target molecules that lead to promising new antibody-based therapies against cancers.Targeted therapies have revolutionized the treatment of cancers. However, there is a need for innovative targets susceptible to bring new medical treatments. Discovering novel cancer targets, and molecules to interfere with, is a major challenge in oncology research. Among new emerging targets, molecules implicated in cell adhesion, migration and polarity provide promising opportunities to combat tumor proliferation, invasion and metastasis. This is the case of tetraspanins for examples, 1 such as CD151 2 or CD9 3 known to exert prominent roles in cell migration and invasion. Furthermore, their interaction with distinct tyrosine kinase receptors (TKR) accounts for their capacity to modulate cell proliferation. 4 Similarly, integrins and some G protein-coupled receptors can crosstalk with TKR to modulate their activities. 5 Recently, molecules involved in cellular architecture (tight or adherent) junctions have been described as playing a role in the control of cell migration and/or proliferation. 6 The modulation of TKR can also affect cell adhesion molecules such as claudins. 7 In addition, these emerging targets can exert a direct effect by themselves on either tumor cell migration 8 or tumor growth regulation. 9 With the objective to identify new targets in oncology, we initiated a function-based approach to identify new antitumor monoclonal antibodies (Mabs). This innovative approach is based on generation and selection of Mabs that are primarily screened for their capacity to trigger cellular functions, including tumor cell proliferation or tumor apoptosis. By combining these two complementary experimental modalities, we were able to identify a set of tumor-active Mabs and subsequently, for the most potent...

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IGF-1 receptor (IGF-1R) plays a key role in the development of numerous tumors. Blockade of IGF-1R axis using monoclonal antibodies constitutes an interesting approach to inhibit tumor growth. We have previously shown that h7C10, a humanized anti-IGF-1R Mab, exhibited potent antitumor activity in vivo. However, mechanisms of action of h7C10 are still unknown. Here, we showed that h7C10 inhibited IGF-1-induced IGF-1R phosphorylation in a dose-dependent manner. Also, h7C10 abolished IGF-1-induced activation of PI3K/AKT and MAPK pathways. Cell cycle progression and colony formation were affected in the presence of h7C10 probably because of the inhibition of IGF-1-induced cyclin D1 and E expression. In addition, we demonstrated that h7C10 induced a rapid IGF-1R internalization leading to an accumulation into cytoplasm resulting in receptor degradation. Using lysosome and proteasome inhibitors, we observed that the IGF-1R aand b-chains could follow different degradation routes. Thus, we demonstrated that antitumoral properties of h7C10 are the result of IGF-1-induced cell signaling inhibition and down-regulation of IGF-1R level suggesting that h7C10 could be a candidate for therapeutic applications. '

The type IV C-X-C-motif chemokine receptor (CXCR4) is expressed in a large variety of human cancers, including hematologic malignancies, and this receptor and its ligand, stromal cell-derived factor-1 (SDF-1), play a crucial role in cancer progression. We generated a humanized immunoglobulin G1 mAb, hz515H7, which binds human CXCR4, efficiently competes for SDF-1 binding, and induces a conformational change in CXCR4 homodimers. Furthermore, it inhibits both CXCR4 receptor-mediated G-protein activation and b-arrestin-2 recruitment following CXCR4 activation. The binding of the hz515H7 antibody to CXCR4 inhibits the SDF-1-induced signaling pathway, resulting in reduced phosphorylation of downstream effectors, such as Akt, Erk1/2, p38, and GSK3b.