Silke Aigner

CD24 mediates rolling of breast carcinoma cells on P-selectin

P‐selectin mediates rolling of neutrophils and other leukocytes on activated endothelial cells and platelets through binding to P‐selectin glycoprotein ligand‐1 (PSGL‐1). Certain PSGL‐1 negative tumor cell lines can bind P‐selectin under static conditions through the GPI‐linked surface mucin, CD24, but the physiological significance of this interaction and whether it can occur under flow conditions is not known. Here, we show that CD24+ PSGL‐1– KS breast carcinoma cells attach to and roll on recombinant P‐selectin under a continuous wall shear stress, although at a lower density and higher velocity than CD24+ PSGL‐1+ cells, such as HL‐60. Adding excess soluble CD24 or removing CD24 from the cell surface with phosphatidylinositol‐phospholipase C (PI‐PLC) significantly reduced KS cell rolling on P‐selectin. The ability of KS cells to roll on P‐selectin was positively correlated with the CD24 expression level. Comparison with three other CD24+ cell lines established that expression of sialyl‐Lewisx antigen was also necessary for CD24‐mediated rolling on P‐selectin. CD24 purified from KS cells supported rolling of P‐selectin transfectants, but not L‐selectin transfectants. Finally, KS cells rolled on vascular endothelium in vivo in a P‐selectin‐dependent manner. Together our data show that CD24 serves as a ligand for P‐selectin under physiological flow conditions. Interaction of tumor cells with P‐selectin via CD24 may be an important adhesion pathway in cancer metastasis.—Aigner, S., Ramos, C. L., Hafezi‐Moghadam, A., Lawrence, M. B., Friederichs, J., Altevogt, P., and Ley, K. CD24 mediates rolling of breast carcinoma cells on P‐selectin. FASEB J. 12, 1241–1251 (1998)

The Monoclonal Antibody nBT062 Conjugated to Cytotoxic Maytansinoids Has Selective Cytotoxicity Against CD138-Positive Multiple Myeloma Cells In vitro and In vivo

Purpose: We investigated the antitumor effect of murine/human chimeric CD138-specific monoclonal antibody nBT062 conjugated with highly cytotoxic maytansinoid derivatives against multiple myeloma (MM) cells in vitro and in vivo. Experimental Design: We examined the growth inhibitory effect of BT062-SPDB-DM4, BT062-SMCC-DM1, and BT062-SPP-DM1 against MM cell lines and primary tumor cells from MM patients. We also examined in vivo activity of these agents in murine MM cell xenograft model of human and severe combined immunodeficient (SCID) mice bearing implant bone chips injected with human MM cells (SCID-hu model). Results: Anti-CD138 immunoconjugates significantly inhibited growth of MM cell lines and primary tumor cells from MM patients without cytotoxicity against peripheral blood mononuclear cells from healthy volunteers. In MM cells, they induced G2-M cell cycle arrest, followed by apoptosis associated with cleavage of caspase-3, caspase-8, caspase-9, and poly(ADP-ribose) polymerase. Nonconjugated nBT062 completely blocked cytotoxicity induced by nBT062-maytansinoid conjugate, confirming that specific binding is required for inducing cytotoxicity. Moreover, nBT062-maytansinoid conjugates blocked adhesion of MM cells to bone marrow stromal cells. The coculture of MM cells with bone marrow stromal cells protects against dexamethasone-induced death but had no effect on the cytotoxicity of immunoconjugates. Importantly, nBT062-SPDB-DM4 and nBT062-SPP-DM1 significantly inhibited MM tumor growth in vivo and prolonged host survival in both the xenograft mouse models of human MM and SCID-hu mouse model. Conclusion: These results provide the preclinical framework supporting evaluation of nBT062-maytansinoid derivatives in clinical trials to improve patient outcome in MM.

Tregalizumab - A Monoclonal Antibody to Target Regulatory T Cells.

Regulatory T cells (Tregs) represent a subpopulation of CD4+ T cells, which are essential for the maintenance of immunological tolerance. The absence or dysfunction of Tregs can lead to autoimmunity and allergies. The restoration of functional Tregs and/or Treg cell numbers represents a novel and attractive approach for the treatment of autoimmune diseases, e.g., rheumatoid arthritis (RA). The CD4 cell surface receptor is a target for modulation of T cell function. Monoclonal antibodies (mAbs) against CD4 have previously been tested for the treatment of autoimmune diseases, including RA. Furthermore, in model systems, anti-CD4 antibodies are able to induce tolerance and mediate immunomodulatory effects through a variety of mechanisms. Despite the availability of innovative and effective therapies for RA, many patients still have persistently active disease or experience adverse events that can limit use. A growing body of evidence suggests that Treg modulation could offer a new therapeutic strategy in RA and other autoimmune disorders. Here, we describe tregalizumab (BT-061), which is a novel, non-depleting IgG1 mAb that binds to a unique epitope of CD4. Tregalizumab represents the first humanized anti-CD4 mAb that selectively induces Treg activation.

Efficacy and safety of tregalizumab in patients with rheumatoid arthritis and an inadequate response to methotrexate: results of a phase IIb, randomised, placebo-controlled trial

Objective To evaluate the efficacy, biological activity and safety of tregalizumab in patients with active rheumatoid arthritis (RA) and an inadequate response to methotrexate (MTX). Methods 321 patients were randomised (1:1:1:1) to placebo or tregalizumab 25, 100 or 200 mg once-weekly subcutaneously in addition to MTX treatment. Responders at week 12 continued the same treatment, and non-responders at week 12 were escalated to the next higher tregalizumab dose level or re-randomised from placebo to active treatment. After 24 weeks, patients could continue treatment with tregalizumab for 24 weeks (extension phase). The primary endpoint was the American College of Rheumatology 20% improvement criteria (ACR20) response rate at week 12. Safety and biological activity were monitored through week 48. Results At week 12, ACR20 response rates were not statistically significantly different between placebo and any of the tregalizumab doses. Tregalizumab injections were well tolerated; most adverse events were mild to moderate and comparable among treatment and placebo groups. Biological activity was shown by dose-dependent CD4 downmodulation. Conclusion Treatment with tregalizumab did not show significant clinical efficacy in patients with active RA compared with placebo but resulted in the expected biological effect on CD4 modulation. Tregalizumab was generally well tolerated, and no new safety findings were identified. Trial registration number NCT01999192; Results.