title: Photochemical internalisation, a minimally invasive strategy for light-controlled endosomal escape of cancer stem cell-targeting therapeutics.
abstract: Despite progress in radio-, chemo- and photodynamic-therapy (PDT) of cancer, treatment resistance still remains a major problem for patients with aggressive tumours. Cancer stem cells (CSCs) or tumour-initiating cells are intrinsically and notoriously resistant to conventional cancer therapies and are proposed to be responsible for the recurrence of tumours after therapy. According to the CSC hypothesis, it is imperative to develop novel anticancer agents or therapeutic strategies that take into account the biology and role of CSCs. The present review outlines our recent study on photochemical internalisation (PCI) using the clinically relevant photosensitiser TPCS2a/Amphinex® as a rational, non-invasive strategy for the light-controlled endosomal escape of CSC-targeting drugs. PCI is an intracellular drug delivery method based on light-induced ROS-generation and a subsequent membrane-disruption of endocytic vesicles, leading to cytosolic release of the entrapped drugs of interest. In different proof-of-concept studies we have demonstrated that PCI of CSC-directed immunotoxins targeting CD133, CD44, CSPG4 and EpCAM is a highly specific and effective strategy for killing cancer cells and CSCs. CSCs overexpressing CD133 are PDT-resistant; however, this is circumvented by PCI of CD133-targeting immunotoxins. In view of the fact that TPCS2a is not a substrate of the efflux pumps ABCG2 and P-glycoprotein (ABCB1), the PCI-method is a promising anti-CSC therapeutic strategy. Due to a laser-controlled exposure, PCI of CSC-targeting drugs will be confined exclusively to the tumour tissue, suggesting that this drug delivery method has the potential to spare distant normal stem cells.
authors: Department of Radiation Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, Norway. selbo@rr-research.no.
authors: Pål Kristian
authors: PK
authors: Selbo
authors: Monica
authors: M
authors: Bostad
authors: Cathrine Elisabeth
authors: CE
authors: Olsen
authors: Victoria Tudor
authors: VT
authors: Edwards
authors: Anders
authors: A
authors: Høgset
authors: Anette
authors: A
authors: Weyergang
authors: Kristian
authors: K
authors: Berg
mesh_terms: D000818:Animals; D016503:Drug Delivery Systems; D011992:Endosomes / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects*; D006801:Humans; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects*; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D017319:Photosensitizing Agents; D017382:Reactive Oxygen Species