Targeting Tumor-Initiating Cancer Cells with dCD133KDEL Shows Impressive Tumor Reductions in a Xenotransplant Model of Human Head and Neck Cancer

Abstract

A novel anti-cancer agent was constructed by fusing a gene encoding the scFV that targets both glycosylated and unglycosylated forms of CD133 to a gene fragment encoding deimmunized PE38KDEL. The resulting fusion protein, dCD133KDEL, was studied to determine its ability to bind and kill tumor-initiating cells in vitro and in vivo. The anti-CD133 scFV selectively bound HEK293 cells transfected with the CD133 receptor gene. Time course viability studies showed that dCD133KDEL selectively inhibited NA-SCC and UMSCC-11B, two head and neck squamous cell carcinomas that contain a CD133 expressing subpopulation. Importantly, the drug did not inhibit the viability of hematopoietic lineages measured by long-term culture initiating cell and colony-forming assays from sorted human CD34+ progenitor cells. In addition to in vitro studies, in vivo tumor initiation experiments confirmed that CD133 sorted cells implanted into the flanks of nude mice grew faster and larger than unsorted cells. In contrast, cells that were pretreated with dCD133KDEL prior to implantation showed the slowest and lowest incidence of tumors. Furthermore, UMSCC-11B-luc tumors treated with multiple intratumoral injections of dCD133KDEL showed marked growth inhibition leading to complete degradation of the tumors, not observed with an irrelevant control targeted toxin. Experiments in immunocompetent mice showed that toxin deimmunization resulted in a 90% reduction in circulating anti-toxin levels. These studies show that dCD133KDEL is a novel anti-cancer agent effective at inhibiting cell proliferation, tumor initiation, and eliminating established tumors by targeting the CD133 subpopulation. This agent shows significant promise for potential development as a clinically useful therapy.

Photochemical internalization (PCI) of immunotoxins targeting CD133 is specific and highly potent at femtomolar levels in cells with cancer stem cell properties

“…The potent effect of PCI of CD133/1-sap (AC133-sap) in the sub pico molar range in vitro may indicate a wide therapeutic window for the use of PCI-based approach in vivo. Our experimental data demonstrate the potential of CD133 as a relevant target and are consistent with recent independent studies showing the promise of targeting CD133 using immunotoxins both in vitro and in vivo [10,11,29].…”

“…However, the role and function of this marker still remain unknown. CD133 is found expressed both on the plasma membrane and in the cytoplasm and ligands binding to CD133 are efficiently taken up by receptor mediated endocytosis [10,11], making CD133 an attractive target for delivery of targeting therapeutics. However, CD133-targeting drugs may be degraded or sequestered in endo-lysosomal compartments [12].…”

Deltonin induced both apoptosis and autophagy in head and neck squamous carcinoma FaDu cell

“…The tumor model we used in this study has been described previously [23]. Briefly, 5 × 10 6 FaDu cells per 0.2 ml were s.c. injected into 4-to 6-wk-old nude mice (BeiJing HFK Bioscience Co,.…”

Targeting Head and Neck Cancer Stem Cells

“…Anti-CD133 therapies have been investigated as targeted head and neck anti-CSC therapy. A study conjugating a bacterial toxin (cytolethal distending toxin) to an anti-human CD133 monoclonal antibody demonstrated inhibition of cell proliferation (Damek-Poprawa et al 2011), whereas another study using a single-chain variable fragment targeting CD133 showed marked reduction in tumor proliferation in cell and mouse models (Waldron et al 2011). Inhibition of CD271, as well, has been demonstrated in cell models to decrease tumor formation (Murillo-Sauca et al 2014).…”