title: Light-controlled endosomal escape of the novel CD133-targeting immunotoxin AC133-saporin by photochemical internalization - A minimally invasive cancer stem cell-targeting strategy.
abstract: The cancer stem cell (CSC) marker CD133 is an attractive target to improve antitumor therapy. We have used photochemical internalization (PCI) for the endosomal escape of the novel CD133-targeting immunotoxin AC133-saporin (PCIAC133-saporin). PCI employs an endocytic vesicle-localizing photosensitizer, which generates reactive oxygen species upon light-activation causing a rupture of the vesicle membranes and endosomal escape of entrapped drugs. Here we show that AC133-saporin co-localizes with the PCI-photosensitizer TPCS2a, which upon light exposure induces cytosolic release of AC133-saporin. PCI of picomolar levels of AC133-saporin in colorectal adenocarcinoma WiDr cells blocked cell proliferation and induced 100% inhibition of cell viability and colony forming ability at the highest light doses, whereas no cytotoxicity was obtained in the absence of light. Efficient PCI-based CD133-targeting was in addition demonstrated in the stem-cell-like, triple negative breast cancer cell line MDA-MB-231 and in the aggressive malignant melanoma cell line FEMX-1, whereas no enhanced targeting was obtained in the CD133-negative breast cancer cell line MCF-7. PCIAC133-saporin induced mainly necrosis and a minimal apoptotic response based on assessing cleavage of caspase-3 and PARP, and the TUNEL assay. PCIAC133-saporin resulted in S phase arrest and reduced LC3-II conversion compared to control treatments. Notably, co-treatment with Bafilomycin A1 and PCIAC133-saporin blocked LC3-II conversion, indicating a termination of the autophagic flux in WiDr cells. For the first time, we demonstrate laser-controlled targeting of CD133 in vivo. After only one systemic injection of AC133-saporin and TPCS2a, a strong anti-tumor response was observed after PCIAC133-saporin. The present PCI-based endosomal escape technology represents a minimally invasive strategy for spatio-temporal, light-controlled targeting of CD133+ cells in localized primary tumors or metastasis.
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Cancer Stem Cell Innovation Center (SFI-CAST), Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.
authors.forename: Monica
authors.initials: M
authors.lastname: Bostad
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Cancer Stem Cell Innovation Center (SFI-CAST), Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.
authors.forename: Cathrine Elisabeth
authors.initials: CE
authors.lastname: Olsen
authors.affiliation: Department of Pathology, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.
authors.forename: Qian
authors.initials: Q
authors.lastname: Peng
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.
authors.forename: Kristian
authors.initials: K
authors.lastname: Berg
authors.affiliation: Cancer Stem Cell Innovation Center (SFI-CAST), Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; PCI Biotech AS, Lysaker, Norway.
authors.forename: Anders
authors.initials: A
authors.lastname: Høgset
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Cancer Stem Cell Innovation Center (SFI-CAST), Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway. Electronic address: selbo@rr-research.no.
authors.forename: Pål Kristian
authors.initials: PK
authors.lastname: Selbo
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D003106:Colon / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D016503:Drug Delivery Systems; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D000922:Immunotoxins / Q000008:administration & dosage* / Q000378:metabolism / Q000494:pharmacology; D008027:Light; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000008:administration & dosage* / Q000378:metabolism / Q000494:pharmacology; D012007:Rectum / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D054789:Ribosome Inactivating Proteins, Type 1 / Q000008:administration & dosage* / Q000378:metabolism / Q000494:pharmacology; D000076985:Saporins
chemical_list: D000922:Immunotoxins; D017319:Photosensitizing Agents; D054789:Ribosome Inactivating Proteins, Type 1; D000076985:Saporins
keywords: Autophagy; CD133; Cancer stem cells; Cancer therapy; Controlled drug delivery; Endosomal escape; Immunotoxin; Photochemical internalization; Photodynamic therapy; Targeting