Michal Dranitzki Elhalel

CTLA-4 · FasL Induces Alloantigen-Specific Hyporesponsiveness

The APC:T cell interface can be effectively targeted with immunotherapeutic proteins. We previously described a unique trans signal converter protein, CTLA-4 · Fas ligand (FasL), that has the inherent capacities to tether the T cell inhibitor FasL (CD95 ligand) to the surfaces of B7 (CD80 and CD86)-positive APC (via CTLA-4:B7 interaction), and in so doing, to simultaneously interfere with B7-to-CD28 T cell activation signals. Given the continuing need for agents capable of inducing allograft tolerance without generalized immunosuppression, we have explored in depth the functional activity of CTLA-4 · FasL in human allogeneic MLR. CTLA-4 · FasL inhibits 1° MLR and induces specific hyporesponsiveness in 2° MLR, with both effects only partially reversible with exogenous IL-2. Moreover, the presence of exogenous IL-2 during the 1° MLR does not affect the induction of hyporesponsiveness upon restimulation. Furthermore, CTLA-4 · FasL enables partial activation of allostimulated T cells, reduces the fraction of actively dividing cells, and increases the percentage of dead cells among dividing T cells. Taken together, these findings suggest that CTLA-4 · FasL-mediated inhibition of secondary alloantigenic responses involves both anergy induction and clonal deletion. Thus, CTLA-4 · FasL, a paradigmatic trans signal converter protein, manifests unique functional properties and emerges as a potentially useful immunotherapeutic for modulating alloresponsiveness.

Fn14•Trail effectively inhibits hepatocellular carcinoma growth.

Background New strategies for the treatment of hepatocellular carcinoma (HCC) are needed, given that currently available chemotherapeutics are inefficient. Since tumor growth reflects the net balance between pro-proliferative and death signaling, agents shifting the equilibrium toward the latter are of considerable interest. The TWEAK:Fn14 signaling axis promotes tumor cell proliferation and tumor angiogenesis, while TRAIL:TRAIL-receptor (TRAIL-R) interactions selectively induce apoptosis in malignant cells. Fn14•TRAIL, a fusion protein bridging these two pathways, has the potential to inhibit tumor growth, by interfering with TWEAK:Fn14 signaling, while at the same time enforcing TRAIL:TRAIL-R-mediated apoptosis. Consequently, Fn14•TRAILs capacity to inhibit HCC growth was tested. Results Fn14•TRAIL induced robust apoptosis of multiple HCC cell lines, while sparing non-malignant hepatocyte cell lines. Differential susceptibility to this agent did not correlate with expression levels of TRAIL, TRAIL-R, TWEAK and Fn14 by these lines. Fn14•TRAIL was more potent than soluble TRAIL, soluble Fn14, or a combination of the two. The requirement of both of Fn14•TRAILs molecular domains for function was established using blocking antibodies directed against each of them. Subcutaneous injection of Fn14•TRAIL abrogated HCC growth in a xenograft model, and was well tolerated by the mice. Conclusions In this study, Fn14•TRAIL, a multifunctional fusion protein originally designed to treat autoimmunity, was shown to inhibit the growth of HCC, both in vitro and in vivo. The demonstration of this fusion protein’s potent anti-tumor activity suggests that simultaneous targeting of two signaling axes by a single fusion can serve as a basis for highly effective anti-cancer therapies.

Fn14·TRAIL fusion protein is oligomerized by TWEAK into a superefficient TRAIL analog

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) demonstrates specific anti-cancer activity, but insufficient efficacy in patients. A fusion protein Fn14·TRAIL, that combines soluble TRAIL molecule with a specific TWEAK receptor Fn14, is a better apoptosis-inducer for hepatocellular carcinomas than soluble TRAIL. However, Fn14·TRAIL does not effectively induce apoptosis in tumors of the lymphoid origin. As malignant cell apoptosis is strongly enhanced by secondary oligomerization of TRAIL, we tested the hypothesis that soluble Fn14·TRAIL can be oligomerized and become more active by adding TWEAK, a cytokine secreted in the tumor environment. We revealed that TWEAK and Fn14·TRAIL spontaneously formed a stable complex that induced apoptosis of malignant lymphoblasts earlier and more efficiently than TRAIL. The TWEAK-modified Fn14·TRAIL oligomer bound to target cells and delivered apoptotic signaling via TRAIL receptors. The oligomer induced faster and stronger cleavage of procaspase-8, -9, and -3; BID; poly-ADP ribose polymerase; and RIP compared to TRAIL. The oligomer also reduced expression of the anti-apoptotic proteins c-FLIP short and cIAP-1. Our data indicate that Fn14·TRAIL can be converted into a highly effective TRAIL oligomer upon binding to TWEAK.

Age limitation for organ transplantation: the Israeli example

In 2013 the Israeli Ministry of Health appointed a public committee to examine the policy of placing an age limitation on candidates listed for organ transplantation. The committee rejected the use of an age limit criterion for listing candidates for transplantation and recommended to abolish it. However, opinions differed regarding the use of recipients’ age in shaping a fair organ allocation policy. The committees recommendations were adopted and put into force as of April 2014. This article unfolds the committee deliberations on accommodating values of formal equality for optimising the use of organ transplantation.