Improved Cellular Pharmacokinetics and Pharmacodynamics Underlie the Wide Anticancer Activity of Sagopilone

Abstract

Sagopilone (ZK-EPO) is the first fully synthetic epothilone undergoing clinical trials for the treatment of human tumors. Here, we investigate the cellular pathways by which sagopilone blocks tumor cell proliferation and compare the intracellular pharmacokinetics and the in vivo pharmacodynamics of sagopilone with other microtubule-stabilizing (or tubulinpolymerizing) agents. Cellular uptake and fractionation/ localization studies revealed that sagopilone enters cells more efficiently, associates more tightly with the cytoskeleton, and polymerizes tubulin more potently than paclitaxel. Moreover, in contrast to paclitaxel and other epothilones [such as the natural product epothilone B (patupilone) or its partially synthetic analogue ixabepilone], sagopilone is not a substrate of the P-glycoprotein efflux pumps. Microtubule stabilization by sagopilone caused mitotic arrest, followed by transient multinucleation and activation of the mitochondrial apoptotic pathway. Profiling of the proapoptotic signal transduction pathway induced by sagopilone with a panel of small interfering RNAs revealed that sagopilone acts similarly to paclitaxel. In HCT 116 colon carcinoma cells, sagopilone-induced apoptosis was partly antagonized by the knockdown of proapoptotic members of the Bcl-2 family, including Bax, Bak, and Puma, whereas knockdown of Bcl-2, Bcl-X L , or Chk1 sensitized cells to sagopilone-induced cell death. Related to its improved subcellular pharmacokinetics, however, sagopilone is more cytotoxic than other epothilones in a large panel of human cancer cell lines in vitro and in vivo. In particular, sagopilone is highly effective in reducing the growth of paclitaxel-resistant cancer cells. These results underline the processes behind the therapeutic efficacy of sagopilone, which is now evaluated in a broad phase II program. [Cancer Res 2008;68(13):5301-8]

Role of the c subunit of the FOATP synthase in mitochondrial permeability transition

“…Immunofluorescence microscopy was performed according to standard procedures. 72 Briefly, cells were fixed in 4% PFA for 20 min at RT, washed three times in PBS and permeabilized with 0.1% Triton X-100 (v:v in PBS) for 5 min at RT. Thereafter, unspecific binding sites were blocked by incubating cells in 2% powdered milk (w:v in PBS) for 1 h at RT.…”

Consensus guidelines for the detection of immunogenic cell death

“…22 It turned out that the unsuspected ability of doxorubicin (an anthracycline employed for the treatment of various carcinomas) to trigger ICD as a standalone intervention, hence converting dying cancer cells into a vaccine that is efficient in the absence of adjuvants, is shared by a relatively restricted set of lethal triggers. [28][29][30][31][32][33] These include, but perhaps are not limited to, mitoxantrone and epirubicin (2 other anthracyclines currently used in the clinic), [34][35][36][37] bleomycin (a glycopeptide antibiotic endowed with antineoplastic properties), 38 oxaliplatin (a platinum derivative generally employed against colorectal carcinoma), [39][40][41][42] cyclophosphamide (an alkylating agent approved for the treatment of neoplastic and autoimmune conditions), [43][44][45][46][47][48] etoposide (a topoisomerase inhibitor currently used for the treatment of several neoplasms) combined with the chemical inhibitor of glycolysis 2-deoxyglucose, 49,50 patupilone (a microtubular inhibitor that has not yet been approved for use in humans), [51][52][53] septacidin (an antifungal antibiotic produced by Streptomyces fibriatus) 54,55 specific forms of radiation therapy, 34,[56][57][58][59][60][61][62][63][64] photodynamic therapy (a clinically approved antican...…”

Trial Watch: Immunogenic cell death inducers for anticancer chemotherapy

“…3,36 Interestingly, such bona fide ICD inducers include various anticancer chemotherapeutics that have been successfully employed in the clinic for several years (Table 1), like (1) doxorubicin, an anthracycline approved by the US Food and Drug Administration (FDA) for the treatment of acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), breast carcinoma, gastric cancer, lymphoma, multiple myeloma (MM), neuroblastoma, ovarian carcinoma, small cell lung carcinoma, soft tissue and bone sarcomas, thyroid carcinoma, transitional cell bladder carcinoma and Wilms' tumor; 2,49 (2) epirubicin, an anthracycline licensed for use in breast carcinoma patients; 2,49 (3) idarubicin, an anthracycline currently employed for the treatment of AML; 19,49 (4) mitoxantrone, an anthracenedione licensed for use in individuals with AML, breast carcinoma, nonHodgkin's lymphoma (NHL) and prostate carcinoma; 2,49 (5) bleomycin, a glycopeptide antibiotic commonly employed as a palliative treatment for Hodgkin's lymphoma, NHL, penile cancer, testicular cancer, and squamous carcinomas of the head and neck, cervix and vulva; 50 (6) bortezomib, a proteasomal inhibitor approved for use in subjects with MM and mantle cell lymphoma; 17,51,52 (7) cyclophosphamide, an alkylating agent nowadays employed for the treatment of ALL, AML, chronic lymphocytic leukemia, breast carcinoma, chronic myeloid leukemia (CML), lymphoma, MM, mycosis fungoides, neuroblastoma, ovarian carcinoma and retinoblastoma; 53 and (8) oxaliplatin, a platinum derivative approved for use in combination with 5-fluorouracil and folinic acid for the therapy of advanced colorectal carcinoma. 40,44,54 Moreover, at least in some cell types, ICD can be provoked by patupilone, an experimental microtubular inhibitor of the epothilone family, [55][56][57] and by 7A7, a monoclonal antibody (mAb) targeting the murine epidermal growth factor receptor (EGFR). 58,59 However, for the reasons mentioned above, FDA-approved epothilones (i.e., ixabepilone, which is licensed for the treatment of breast carcinoma) 60 and EGFR-targeting mAbs (i.e., cetuximab and panitumumab, which are currently employed for the treatment of head and neck cancer and colorectal carcinoma) [61][62][63] may not share this ability with patupilone and 7A7, respectively.…”