Abstract
Abstract
Recent evidence strongly supports the hypothesis that the capability to sustain tumor formation, growth and resistance to chemotherapy in ovarian cancer exclusively resides in a small proportion of tumor cells termed cancer stem cells (CSC) overexpressing the CD44 marker. If this hypothesis is correct, development of novel, more specific approaches to target and eradicate the CD44+ ovarian CSC population remains a high priority. Our group has recently reported high expression of claudin-4 tight junction protein in CD44+ ovarian CSC. Because this protein is the natural high affinity receptor for Clostridium Perfringens Enterotoxin (CPE), we have evaluated the in vitro targeting potential of fluorescent (i.e. Coumarin 6 loaded) poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NP) conjugated with the C-terminus binding domain of CPE (CPE-peptide) against ovarian CSC and the in vivo biodistribution of these NP after intravenous (IV) injection in SCID mice harboring intraperitoneal CD44+ ovarian CSC tumor. Using flow cytometry, we report a higher time and dose-dependent in vitro uptake of fluorescent PLGA NP conjugated to CPE peptide (CPE-peptide NP) in CD44+ ovarian CSC when compared to unconjugated NP (i.e., control NP, Mean-Fluorescence-Intensity = MFI of 37.1 and 15.0 respectively; p=0.037). Of interest, confocal microcopy images clearly show internalization of CPE-peptide NP within tumor cells after NP exposure. More importantly, when SCID mice harboring claudin-4 overexpressing CD44+ ovarian CSC tumors were injected via the tail vein (IV) with 25 μg/g of CPE-peptide NP or the same concentration of unconjugated NP, a 4 fold increase in fluorescence was detected in tumors excised from mice injected with CPE-peptide NP compared to controls 48 hours after NP administration (mean ± STDV 33159.6 2707 and 6655.8 ±1391 respectively; p<0.01). Finally, non specific NP uptake in healthy organs calculated as the ratio between organs and tumor fluorescence was found to be significantly lower after injection of CPE-peptide NP than the unconjugated control NP. Taken together these results suggest that the CPE-peptide, when conjugated to NP, may confer high specificity in targeting claudin-4 overexpressing CD44+ ovarian CSC tumors in vivo. CPE-peptide NP may represent an unconventional, potentially highly effective strategy to specifically target chemotherapy-resistant CD44+ ovarian CSC for diagnostic and/or therapeutic purposes.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 364. doi:1538-7445.AM2012-364
