Abstract
TNFR superfamily (TNFRSF) members have important immunoregulatory functions and are of clear interest for cancer immunotherapy. Various TNFRSF agonists have been clinically evaluated, but have met with limited efficacy and/or toxicity. Recent insights indicate that ‘first-generation’ TNFRSF agonists lack efficacy as they do not effectively cross-link their corresponding receptor. Reversely, ubiquitous TNFRSF receptor(s) cross-linking by CD40 and Fas agonistic antibodies resulted in dose-limiting liver toxicity. To overcome these issues, we developed a novel pretargeting strategy exploiting recombinant fusion proteins in which a soluble form of TRAIL, FasL or CD40L is genetically fused to a high-affinity anti-fluorescein scFv antibody fragment (scFvFITC). Fusion proteins scFvFITC:sTRAIL and scFvFITC:sFasL induced potent target antigen-restricted apoptosis in a panel of cancer lines and in primary patient-derived cancer cells, but only when pretargeted with a relevant FITC-labelled antitumour antibody. In a similar pretargeting setting, fusion protein scFvFITC:sCD40L promoted tumour-directed maturation of immature monocyte-derived dendritic cells (iDCs). This novel tumour-selective pretargeting approach may be used to improve efficacy and/or reduce possible off-target toxicity of TNFSF ligands for cancer immunotherapy.
Highlights
The TNF-receptor superfamily (TNFRSF) serves various key immunoregulatory functions and includes Death Receptors that trigger apoptosis in cancer cells and receptors that provide co-stimulatory signals to anti-tumour T cells
Similar pretargeting activity by scFvFITC:sTRAIL was detected towards CD20pos/CD7neg B-cell lines BJAB, Z138 and PRI only when pretargeted with RTX-FITC, with no activity upon pretargeting with an irrelevant FITC-labelled anti-CD7 antibody (Fig. 1D and E)
The capacity of fusion protein scFvFITC:sCD40L to promote tumour-directed maturation of immature monocyte-derived dendritic cells was significantly enhanced when tumour cells were pretreated with a relevant FITC-labelled anti-tumour antibody
Summary
The TNF-receptor superfamily (TNFRSF) serves various key immunoregulatory functions and includes Death Receptors that trigger apoptosis in cancer cells and receptors that provide co-stimulatory signals to anti-tumour T cells. It is well established that both solid and non-solid malignancies show antigen heterogeneity due to genomic instability, epigenetic alterations and microenvironmental differences[23,24] To address these issues, we here report on a two-step approach which involves pretargeting of cancer cells with fluorescein-labelled anticancer antibodies, followed by treatment with a recombinant scFv:TNFSF fusion protein with high-affinity binding capacity for fluorescein derivatives. We here report on a two-step approach which involves pretargeting of cancer cells with fluorescein-labelled anticancer antibodies, followed by treatment with a recombinant scFv:TNFSF fusion protein with high-affinity binding capacity for fluorescein derivatives These scFv:FITC:sTNFSF fusion proteins only gain full agonistic activity upon binding to cancer cells pretargeted with a FITC-labelled antibody. In a similar pretargeting setting, fusion protein scFvFITC:sCD40L promoted tumour-directed maturation of immature monocyte-derived dendritic cells (iDCs)
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