Reversal of doxorubicin resistance in breast cancer cells by photochemical internalization

Abstract

Multiple drug resistance (MDR) is a problem that seriously reduces the efficacy of many chemotherapy agents. One mechanism for MDR is increased acidification of endocytic vesicles and increased cytosol pH, so weak base chemotherapeutic agents, including doxorubicin, are trapped in endocytic vesicles and exhibit a drug resistant phenotype. Treatments that selectively reverse this accumulation may therefore reverse the MDR phenotype. Photochemical internalization (PCI) is a novel technology developed for site-specific enhancement of the therapeutic efficacy of macromolecules by selective photochemical rupture of endocytic vesicles and consequent release of endocytosed macromolecules into the cytosol. This study evaluates PCI for release of doxorubicin from endocytic vesicles in MDR cells. Two breast cancer cell lines, MCF-7 and MCF-7/ADR (the latter resistant to doxorubicin), were selected. They were found equally sensitive to photochemical treatment with the photosensitiser TPPS 2a (disulfonated meso-tetraphenylporphine) and light. On exposure to doxorubicin alone, the IC 50 (drug concentration for 50% reduction in colony formation) was 0.1 lM for MCF-7 and 1 lM for MCF-7/ADR. After PCI (photochemical treatment followed by doxorubicin), the IC 50 concentration was 0.1 lM for both cell lines. Comparable changes were seen with assay of cell viability using 3-(4,5-dimethyltiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). On fluorescence microscopy in MCF-7/ADR cells, doxorubicin localised in granules identified as lysosomes. After PCI, doxorubicin was released into the cytosol and entered cell nuclei, as was seen in MCF-7 cells without PCI. In conclusion, PCI reversed the MDR phenotype of doxorubicin resistant breast cancer cells by endolysosomal release of the drug. The technique is a promising new approach to tackling the problem of MDR. ' 2006 Wiley-Liss, Inc.Key words: photodynamic therapy; photochemical internalization; doxorubicin resistant breast cancer cells Multiple drug resistance (MDR) is a major clinical problem that seriously reduces the efficacy of many chemotherapy agents. The establishment of a MDR phenotype by cancer cells is a result of complex molecular events. The most extensively studied mechanism is the over-expression of cell surface efflux pumps (the ABCtransporter family P-glycoprotein, MDR-associated protein, etc.) that can successfully purge a wide spectrum of chemotherapeutic agents from cells, 1 thereby decreasing their intracellular accumulation. 2 Other possible mechanisms are mutation of the DNA topoisomerase, or altered intracellular distribution of anticancer drugs. 2,3 Inhibition of ABC-transporters as a method to reverse MDR in cancer patients has been studied extensively, but the results have generally been disappointing. First-generation agents (e.g. cyclosporin, verapamil) were limited by unacceptable toxicity, whereas secondgeneration agents (e.g. valspodar, biricodar) had better tolerability, but were confounded by unpredictable pharmacokinetic interactions and interactio...

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.…”

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

“…PCI of gelonin and bleomycin and PCI-enhanced nonviral gene delivery has also been documented in vivo (Selbo et al, 2001;Berg et al, 2005;Dietze et al, 2005;Nishiyama et al, 2005;Ndoye et al, 2006). More recently, it was demonstrated that PCI could make the MDR breast cancer cell line MCF-7/ADR almost as sensitive to DOX as the fully sensitive cells, MCF-7, from the same origin by the intracellular release of endosome-lysosome-trapped DOX (Lou et al, 2006). Accumulation of DOX in MCF-7/ADR cells can be explained by the protonation, sequestration, and secretion (PSS) model (Altan et al, 1998), which suggests that weak base drugs are first protonated in acidified organelles of MDR cells, like lysosomes, where they are sequestered.…”

Cytotoxic Activity and Secondary Metabolite Characteristics of Sea Cucumber Actinopyga sp. Methanolic Extract

“…Interestingly, doxorubicin did not show such cytotoxic activity against W iDr cell. As Lou et al (2006) stated, doxorubicin has selective activity against cancer cell line, especially to breast cancer cell line with the LC 50 value of 0.3 µg/ml.…”