Photochemical Internalization of Therapeutic Macromolecular Agents: A Novel Strategy to Kill Multidrug-Resistant Cancer Cells

Abstract

Drug resistance is a major problem for chemotherapy. Entrapment of anticancer drugs in endolysosomal compartments or active extrusions by plasma membrane proteins of the ATPbinding cassette (ABC) superfamily are important resistance mechanisms. This study evaluated photochemical internalization (PCI) of membrane-impermeable macromolecules that are not the target of ABC drug pumps for treating multidrug-resistant (MDR) cancer cells. We used the drug-sensitive uterine fibrosarcoma cell line MES-SA and its MDR, P-glycoprotein (P-gp)-overexpressing derivative MES-SA/Dx5 with the photosensitizer disulfonated meso-tetraphenylporphine (TPPS 2a ) and broad spectrum illumination. The PCI of doxorubicin, the ribosome-inactivating protein gelonin and adenoviral transduction were assessed in both cell lines, together with the uptake and excretion of TPPS 2a and of two fluid phase markers easily detectable by fluorescence [lucifer yellow (LY) and fluorescein isothiocyanate (FITC)-dextran], as a model of gelonin uptake. Both cell lines were resistant to PCI of doxorubicin, but equally sensitive to PCI of gelonin, even though the endocytosis rates of LY and FITC-dextran were significantly lower in the MDR cells. In control studies, MES-SA/Dx5 cells were more resistant to photodynamic therapy (TPPS 2a ϩ light only). This was not mediated by P-gp, as there were no differences in the uptake and efflux of TPPS 2a between the cell lines. After adenoviral infection, PCI enhanced gene delivery in both cell lines. In conclusion, PCI of macromolecular therapeutic agents that are not targets of P-gp is a novel therapeutic strategy to kill MDR cancer cells.

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

“…Interestingly, treating prostate cancer cells with short-term differentiation therapy resulted in enhanced photosensitisation of prostate cancer cells [42]. PCI of ITs may have the advantage over chemotherapy and radiation therapy by targeting quiescent CSC since all nucleated cells undergo endocytosis, thereby, overcoming potential therapy resistance [23,[43][44][45]. Differentiated cells of the tumor are likely to be killed due to photodynamic induced shutdown of tumor vasculature by formation of reactive oxygen species (ROS) and also direct cell killing by apoptosis or necrosis [43].…”

“…Cell viability was evaluated by the 3-(4.5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide (MTT) method (tetrazolium dye reduction) 120 h after light exposure with Lumisource®. Cell survival was assessed by the clonal cell survival method 7-10 days after light exposure [23].…”

Photodynamic therapy of cancer — Challenges of multidrug resistance

“…Although PCI might reverse or bypass the MDR phenotype by endo-lysosomal release of the MDR substrate drug, PCI of macromolecular therapeutic agents that are not targets of MDR transporters represents another therapeutic strategy to treat MDR cancer. 71,72 Taking advantages of nanocarriers might further extend the e±cacy of PDT and PCI. [73][74][75] PCI of numerous macromolecules has been demonstrated in vitro and in vivo.…”

Photodynamic therapy for photochemists

“…However, if the membranes of these intracellular organelles are broken down by photochemical internalization (PCI), the macromolecules can become biologically active. This mechanism has been shown to overcome the resistance of some breast cancer cells to chemotherapy agents such as doxorubicin [40] and may be a way of undertaking gene transfer [41]. Preliminary clinical trials are already underway on the PCI of bleomycin using the photosensitizer TPCS2a (Amphinex, a chlorin derivative), on advanced head and neck cancers.…”