86 Potent anti-tumor activity of T-DM1 antibody–drug conjugate in combination with chemotherapeutic agents in breast tumor cells

Although IFN-α was reported to promote the survival of peripheral B-lymphocytes via the PI3-kinase-Akt pathway, the triggered signalling pathways involved in the protection of B cell from apoptosis need to be clarified. Using flow cytometry and western blot analysis, we have found that type 1 IFNs (IFN-α/β) protect human B cells in culture from spontaneous apoptosis and from apoptosis mediated by anti-CD95 agonist, in a dose- and time-dependant manner. IFN-α/β-mediated anti-apoptotic effect on human B cells was totally abrogated by blockade of IFNR1 chain. Our data indicate that PI3Kδ, Rho-A, NFκB and Bcl-2/BclXL are active downstream of IFN receptors and are the major effectors of IFN-α/β-rescued B cells from apoptosis. Furthermore, immunohistochemical results show marked reduction in numbers of CD20 positive B cell in both spleen and Peyer’s patches from mice treated with anti-IFNR1 blocking antibody compared with control group. Moreover, ultrastructural observations of these organs show an obvious increase in apoptotic cells from mice treated with anti-IFNR1 blocking antibody. Our results provide more details about the triggered signalling pathways and the phosphorylation cascade which are involved in the protection of B cell from apoptosis after treatment with IFN-α/β.