PURPOSE:We sought to demonstrate that a single systemic administration of L19mTNFalpha (a fusion protein constituted by the scFv L19 specific for the oncofetal ED-B domain of fibronectin and tumor necrosis factor alpha, TNFalpha) in combination with melphalan induced complete and long-lasting tumor eradication in tumor-bearing mice and triggered the generation of a specific T cell-based immune response that protects the animals from a second tumor challenge, as well as from challenges with syngeneic tumor cells of different histologic origin.EXPERIMENTAL DESIGN AND RESULTS:Treatment with L19mTNFalpha, in combination with melphalan, induced complete tumor regression in 83% of BALB/c mice with WEHI-164 fibrosarcoma and 33% of animals with C51 colon carcinoma. All cured mice rejected challenges with the same tumor cells and, in a very high percentage of animals, also rejected challenges with syngeneic tumor cells of different histologic origin. In adoptive immunity transfer experiments, the splenocytes from tumor-cured mice protected naive mice both from C51 colon carcinoma and from WEHI-164 fibrosarcoma. Similar results were also obtained in adoptive immunity transfer experiments using severely immunodepressed mice. Experiments using depleted splenocytes showed that T cells play a major role in tumor rejection.CONCLUSIONS:The results show that the selective targeting of mTNFalpha to the tumor enhances its immunostimulatory properties to the point of generating a therapeutic immune response against different histologically unrelated syngeneic tumors. These findings predicate treatment approaches for cancer patients based on the targeted delivery of TNFalpha to the tumor vasculature.

Activated leukocyte cell adhesion molecule (ALCAM/CD166), a member of the immunoglobulin superfamily with five extracellular immunoglobulin-like domains, promotes heterophilic (ALCAM-CD6) and homophilic (ALCAM-ALCAM) cell-cell interactions. Here we describe a fully human single-chain antibody fragment (scFv) directed to ALCAM/CD166. We selected the I/F8 scFv from a phage display library of human V-gene segments by cell panning and phage internalization into IGROV-I human ovary carcinoma cells. The I/F8 specificity was identified as ALCAM/CD166 by matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) peptide mass fingerprinting of the I/F8-immunoprecipitated protein. The I/F8 scFv reacts with the human, monkey and murine ALCAM/CD166 molecule, indicating that the recognized epitope is highly conserved. The I/F8 scFv completely abolished binding of both ALCAM/Fc and CD6/Fc soluble ligands, whereas it did not compete with the anti-ALCAM/CD166 murine monoclonal antibodies J4-81 and 3A6 and therefore recognizes a different epitope. Engagement through I/F8 scFv, 3A6 monoclonal antibody or CD6/Fc ligand induced ALCAM/CD166 internalization, with a kinetics slower than that of transferrin in the same cells. Newly internalized I/F8-ALCAM complexes colocalized with clathrin but not with caveolin and we demonstrated, using surface biotinylation and recycling assays, that endocytosed ALCAM/CD166 recycles back to the cell surface. Such an endocytic pathway allows the efficient delivery of an I/F8 scFv-saporin immunotoxin into tumor cells, as the conjugates are able to selectively kill cell lines expressing ALCAM/CD166. Altogether these data provide evidence of the suitability of the I/F8 scFv for further functional analysis of ALCAM/CD166 and intracellular delivery of effector moieties.

We sought to enhance the selective toxicity of tumor necrosis factor alpha (TNFalpha) to permit its systemic use in cancer therapy. Because ligand-targeted therapeutics have proven successful in improving the selective toxicity of drugs, we prepared a fusion protein (L19mTNFalpha) composed of mouse TNFot and a high-affinity antibody fragment (L19 scFv) to the extradomain B (ED-B) domain of fibronectin, a marker of angiogenesis. L19mTNFalpha was expressed in mammalian cells, purified, and characterized. L19mTNFalpha was an immunoreactive and biologically active homotrimer. Radiolabeled L19mTNFalpha selectively targeted tumor neovasculature in tumor-bearing mice, where it accumulated selectively and persistently (tumor-to-blood ratio of the percentage of injected dose per gram [%ID/g] of 700, 48 hours from injection). L19mTNFa showed a greater anticancer therapeutic activity than both mTNFalpha and TN11mTNFalpha, a control fusion protein in which an antibody fragment, irrelevant in the tumor model used, substituted for L19. This activity was further dramatically enhanced by its combination with melphalan or the recently reported fusion protein L19-IL2. In conclusion, L19mTNFalpha allows concentrating therapeutically active doses of TNFalpha at the tumor level, thus opening new possibilities for the systemic use of TNFa in cancertherapy. (C) 2003 by The American Society of Hematology.