Immunotoxin targeting CD133+ breast carcinoma cells

Abstract

CD133 expression enriches for tumor-initiating cells and is a negative prognostic factor in numerous cancers. We previously developed an immunotoxin against CD133 by fusing a gene fragment encoding the scFv portion of an anti-CD133 antibody to a gene fragment encoding deimmunized PE38KDEL. The resulting fusion protein, dCD133KDEL, demonstrated potent antitumor activity following intratumoral delivery into head neck cell carcinoma xenografts. However, the efficacy against other tumors and the tolerability of systemic administration remained unclear. The purpose of this study was to evaluate the tolerability and efficacy of dCD133KDEL in a systemic human breast carcinoma model. Time course viability studies showed that dCD133KDEL selectively inhibited MDA-MB-231 ductal breast carcinoma cells that contained a minority CD133(+) subpopulation, implicating CD133(+) cells as a source for self-renewal within this cell line. Furthermore, systemic administration of dCD133KDEL caused regression or inhibition of tumor growth in mice bearing an intrasplenic MDA-MB-231 tumor challenge as a model for metastatic disease. In the same model, combined therapy with dCD133KDEL and another immunotoxin designed to target the bulk tumor mass was the most effective therapy, supporting the idea that such combination therapies might better address tumor heterogeneity. dCD133KDEL shows promise as a therapeutic agent and as a biologic tool to study cancer stem cells.

Heterodimeric Bispecific Single Chain Variable Fragments (scFv) Killer Engagers (BiKEs) Enhance NK-cell Activity Against CD133+ Colorectal Cancer Cells

“…CD133 is a well-established marker on CSC verified by sorting CD133 + cells from various tumor types and then demonstrating that these sorted cells have enhanced tumor initiation and self-renewal capabilities. Furthermore, our group has used this same anti-CD133 scFv in the construction of targeted toxins that have impressive anti-tumor affects in treating human breast [25], head and neck [26] and ovarian cancer [27] in xenograft models. Tumor free status in these studies was achieved despite the fact that only 5% of the tumor cells express CD133.…”

“…It is now believed that CSC comprise a minority population within a tumor that is able to self-renew and produce the heterogeneous lineages of cancer cells that develops into the bulk of the tumor mass [25]. Tumorigenic CSCs have proven to be highly resistant to conventional chemotherapy, so these cells are believed to be at the root cause of tumor relapse.…”

Tetraspecific scFv construct provides NK cell mediated ADCC and self-sustaining stimuli via insertion of IL-15 as a cross-linker

“…A CD133 targeting toxin and a CD133 BiKE which were constructed with the same CD133 binding site as the TetraKE showed good response rates in CD133 + bearing ovarian, gastrointestinal and breast cancer [23, 42–44] even when the CD133 + population was <10% CD133 + cells. [43]. CD133KDEL, a targeted toxin showed specific and dose dependent inhibition in human HNSCC cells in vivo by our group [22].…”

Identification and characterization of a novel scFv recognizing human and mouse CD133

“…We are currently investigating the use of anti-CD133 scFv for constructing a targeted immunotoxin, dCD133KDEL, by fusing the anti-CD133 scFv with pseudomonas exotoxin A-PE38 and a c-terminal Lys-Asp-Glu-Leu (KDEL) peptide. This toxin was found to be very potent in selectively targeting and killing CD133+ cancer stem cells in metastatic breast carcinoma [8] and head neck carcinoma xenografts in mouse [9]. Expression of CD133 is not restricted to tumor-initiating cells.…”

“…Its expression is also seen in cancer initiating cells in many tumors including that of brain, prostrate, colon and breast [5–7] and is, therefore, used widely as a molecular marker to isolate and characterize these cell phenotypes. Targeting CD133 may also enable enhanced delivery of cytotoxic therapies to cancer initiating cells [8, 9]. Further development of CD133 as a diagnostic marker and/or therapeutic target, requires highly sensitive reagents that exclusively recognize CD133.…”