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CD147/Basigin/EMMPRIN is overexpressed in several cancerous tissues and it has been shown to induce matrix metalloproteinases (MMPs) whose expression is associated with cancer metastasis. Thus, targeting CD147 with monoclonal antibodies (mAbs) potentially has therapeutic applications in cancer immunotherapy. Here, we report the use of anti-CD147 mAbs targeting domain 1 of CD147, namely M6-1D4 (IgM), M6-1F3 (IgM), M6-2F9 (IgM) and M6-1E9 (IgG2a), against several human cancer cell lines. Strikingly, IgM but not IgG mAbs against CD147, especially clone M6-1D4, induced acute cellular swelling, and this phenomenon appeared to be specifically found with hepatocellular carcinoma (HCC) cells. Furthermore, molecular investigation upon treating HepG2 cells with M6-1D4 showed unfolded protein response (UPR) activation, autophagosome accumulation, and cell cycle arrest, but without classic apoptosis related features. More interestingly, prolonged M6-1D4 treatment (24 h) resulted in irreversible oncosis leading to necroptosis. Furthermore, treatment with a mixed lineage kinase domain-like psuedokinase (MLKL) inhibitor and partial knockout of MLKL resulted in reduced sensitivity to necroptosis in M6-1D4-treated HepG2 cells. Surprisingly however, the observed necroptotic signaling axis appeared to be non-canonical as it was independent of receptor-interacting serine/threonine-protein kinase (RIPK) phosphorylation. In addition, no cytotoxic effect on human dermal fibroblast (HDF) was observed after incubation with M6-1D4. Taken together, this study provides clues to target CD147 in HCC using mAbs, as well as sheds new light on a novel strategy to kill cancerous cells by the induction of necroptosis., (Copyright © 2022 Elsevier B.V. All rights reserved.)

CD99, a leukocyte surface glycoprotein, has been implicated in many cellular processes including cell adhesion, cell migration and T cell activation. Our previous study demonstrated the anti-CD99 monoclonal antibody (mAb) clone MT99/3 inhibited T cell activation; however, the mechanism is unclear. In this study, we demonstrated that CD99 expressed on monocytes played a role in the inhibition of T cell activation. Anti-CD99 mAb MT99/3 downregulated the expression of costimulatory molecule CD86, but upregulated IL-6, IL-10 and TNF-α production by monocytes. The inhibitory effect of mAb MT99/3 required cell to cell contact between monocytes and lymphocytes. The soluble mediators produced by monocytes alone were insufficient to induce hypo-function of T lymphocytes. In summary, we demonstrated that ligation of CD99 on monocytes by anti-CD99 mAb MT99/3 could mediate T cell hypo-responsiveness. These findings provide the first evidence of the role of CD99 on monocytes that contributes to T cell activation., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Na,K ATPase plays an important role in the regulation of Na(+) and K(+) ions that are required for normal resting membrane potential and various cellular functions. Na,K ATPase is composed of two subunits, α and β subunits. Engagement of the β subunit by an agonistic monoclonal antibody (mAb) P-3E10 inhibited T cell activation and induced the G0/G1 cell cycle arrest. In addition, mAb P-3E10 decreased CD25 expression. The mAb P-3E10, however, did not inhibit the proliferation of cell lines and the phagocytosis activity of phagocytes, and did not interfere with the Na,K ATPase activity. These results indicate that mAb P-3E10 reacts to the β subunit and, as a consequence, brings about the regulation of the T cell activation without disturbing the Na,K pump activity. By sequential immunoprecipitation, we demonstrated the expression of the β3 subunit free form apart from the α subunit. In this study, we propose that the β3 subunits of Na,K ATPase are expressed separately from the α subunit, and play a role in regulation of the immune response., (Copyright © 2015 Elsevier GmbH. All rights reserved.)