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Tepotinib is a novel tyrosine kinase inhibitor recently approved for the treatment of non-small cell lung cancer (NSCLC). In this study, we evaluated the tepotinib’s potential to perpetrate pharmacokinetic drug interactions and modulate multidrug resistance (MDR). Accumulation studies showed that tepotinib potently inhibits ABCB1 and ABCG2 efflux transporters, which was confirmed by molecular docking. In addition, tepotinib inhibited several recombinant cytochrome P450 (CYP) isoforms with varying potency. In subsequent drug combination experiments, tepotinib synergistically reversed daunorubicin and mitoxantrone resistance in cells with ABCB1 and ABCG2 overexpression, respectively. Remarkably, MDR-modulatory properties were confirmed in ex vivo explants derived from NSCLC patients. Furthermore, we demonstrated that anticancer effect of tepotinib is not influenced by the presence of ABC transporters associated with MDR, although monolayer transport assays designated it as ABCB1 substrate. Finally, tested drug was observed to have negligible effect on the expression of clinically relevant drug efflux transporters and CYP enzymes. In conclusion, our findings provide complex overview on the tepotinib’s drug interaction profile and suggest a promising novel therapeutic strategy for future clinical investigations.

Novel HepG2 cell clones 1A2 C2 and 1A2 C7 were independently generated by lentiviral transduction to functionally overexpress cytochrome P450 1A2 (CYP1A2). We found similar and stable CYP1A2 transcript and protein levels in both cell clones leading to specific enzyme activities of about 370 pmol paracetamol x min-1 x mg-1 protein analyzed by phenacetin conversion. Both clones showed dramatically increased sensitivity to the hepatotoxic compound aflatoxin B1 (EC50 < 100 nM) when compared to parental HepG2 cells (EC50 ∼5 mM). Thus, newly established cell lines are an appropriate tool to study metabolism and toxicity of substances depending on conversion by CYP1A2.

The application of cytostatic drugs or natural substances to inhibit cancer growth and progression is an important and evolving subject of cancer research. There has been a surge of interest in marine bioresources, particularly algae, as well as cyanobacteria and their bioactive ingredients. Dried biomass products of Arthrospira and Chlorella have been categorized as “generally recognized as safe” (GRAS) by the US Food and Drug Administration (FDA). Of particular importance is an ingredient of Arthrospira: phycocyanin, a blue-red fluorescent, water-soluble and non-toxic biliprotein pigment. It is reported to be the main active ingredient of Arthrospira and was shown to have therapeutic properties, including anti-oxidant, anti-inflammatory, immune-modulatory and anti-cancer activities. In the present review, in vitro and in vivo data on the effects of phycocyanin on various tumor cells and on cells from healthy tissues are summarized. The existing knowledge of underlying molecular mechanisms, and strategies to improve the efficiency of potential phycocyanin-based anti-cancer therapies are discussed.

Ensartinib (X-396) is a promising tyrosine kinase inhibitor currently undergoing advanced clinical evaluation for the treatment of non-small cell lung cancer. In this work, we investigate possible interactions of this promising drug candidate with ATP-binding cassette (ABC) drug efflux transporters and cytochrome P450 biotransformation enzymes (CYPs), which play major roles in multidrug resistance (MDR) and pharmacokinetic drug-drug interactions (DDIs). Accumulation studies showed that ensartinib is a potent inhibitor of ABCB1 and ABCG2 transporters. Additionally, incubation experiments with recombinant CYPs showed that ensartinib significantly inhibits CYP3A4 and CYP2C9. Subsequent molecular docking studies confirmed these findings. Drug combination experiments demonstrated that ensartinib synergistically potentiates the antiproliferative effects of daunorubicin, mitoxantrone, and docetaxel in ABCB1, ABCG2, and CYP3A4-overexpressing cellular models, respectively. Advantageously, ensartinib’s antitumor efficiency was not compromised by the presence of MDR-associated ABC transporters, although it acted as a substrate of ABCB1 in Madin-Darby Canine Kidney II (MDCKII) monolayer transport assays. Finally, we demonstrated that ensartinib had no significant effect on the mRNA-level expression of examined transporters and enzymes in physiological and lung tumor cellular models. In conclusion, ensartinib may perpetrate clinically relevant pharmacokinetic DDIs and modulate ABCB1-, ABCG2-, and CYP3A4-mediated MDR. The in vitro findings presented here will provide a valuable foundation for future in vivo investigations.

Alisertib (MLN8237), a novel Aurora A kinase inhibitor, is currently being clinically tested in late-phase trials for the therapy of various malignancies. In the present work, we describe alisertib's potential to perpetrate pharmacokinetic drug-drug interactions (DDIs) and/or to act as an antagonist of multidrug resistance (MDR). In accumulation assays, alisertib potently inhibited ABCC1 transporter, but not ABCB1 or ABCG2. The results of molecular modeling suggested a bifunctional mechanism for interaction on ABCC1. In addition, alisertib was characterized as a low- to moderate-affinity inhibitor of recombinant CYP3A4, CYP2C8, CYP2C9, CYP2C19, and CYP2D6 isoenzymes, but without potential clinical relevance. Drug combination studies revealed the capability of alisertib to synergistically antagonize ABCC1-mediated resistance to daunorubicin. Although alisertib exhibited substrate characteristics toward ABCB1 transporter in monolayer transport assays, comparative proliferation studies showed lack of its MDR-victim behavior in cells overexpressing ABCB1 as well as ABCG2 and ABCC1. Lastly, alisertib did not affect the expression of ABCC1, ABCG2, ABCB1 transporters and CYP1A2, CYP3A4, CYP2B6 isozymes on mRNA level in various systemic and tumoral models. In conclusion, our study suggests that alisertib is a drug candidate with negligible potential for perpetrating systemic pharmacokinetic DDIs on ABCB1, ABCG2 and cytochromes P450. In addition, we introduce alisertib as an effective dual-activity chemosensitizer whose MDR-antagonistic capacities are not impaired by efflux or effect on MDR phenotype. Our in vitro findings provide important pieces of information for clinicians when introducing alisertib into the clinical area.

Drug-induced liver injury (DILI) is the major reason for failures in drug development and withdrawal of approved drugs from the market. Two-dimensional cultures of hepatocytes often fail to reliably predict DILI: hepatoma cell lines such as HepG2 do not reflect important primary-like hepatic properties and primary human hepatocytes (pHHs) dedifferentiate quickly in vitro and are, therefore, not suitable for long-term toxicity studies. More predictive liver in vitro models are urgently required in drug development and compound safety evaluation. This review discusses available human hepatic cell types for in vitro toxicology analysis and their usage in established and emerging three-dimensional (3D) culture systems. Generally, 3D cultures maintain or improve primary hepatic functions (including expression of drug-metabolizing enzymes) of different liver cells for several weeks of culture, thus allowing long-term and repeated-dose toxicity studies. Spheroid cultures of pHHs have been comprehensively tested, but also other cell types such as HepaRG benefit from 3D culture systems. Emerging 3D culture techniques include usage of induced pluripotent stem-cell-derived hepatocytes and primary-like upcyte cells, as well as advanced culture techniques such as microfluidic liver-on-a-chip models. In-depth characterization of existing and emerging 3D hepatocyte technologies is indispensable for successful implementation of such systems in toxicological analysis.

Brivanib, a promising tyrosine kinase inhibitor, is currently undergoing advanced stages of clinical evaluation for solid tumor therapy. In this work, we investigated possible interactions of this novel drug candidate with ABC drug efflux transporters and cytochrome P450 (CYP450) drug-metabolizing enzymes that participate in cancer multidrug resistance (MDR) and pharmacokinetic drug-drug interactions (DDIs). First, in accumulation experiments with various model substrates, we identified brivanib as an inhibitor of the ABCB1, ABCG2, and ABCC1 transporters. However, in subsequent combination studies employing 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide proliferation assays in both Madin-Darby canine kidney II (MDCKII) and A431 cellular models, only ABCG2 inhibition was revealed to be able to synergistically potentiate mitoxantrone effects. Advantageous to its possible use as MDR antagonist, brivanib's chemosensitizing properties were not impaired by activity of any of the MDR-associated ABC transporters, as observed in comparative viability assay in the MDCKII cell sublines. In incubation experiments with eight recombinant CYP450s, we found that brivanib potently inhibited CYP2C subfamily members and the CYP2B6 isoform. Finally, in induction studies, we demonstrated that brivanib upregulated ABCB1 and CYP1A2 messenger RNA levels in systemic cell models, although this interaction was not significantly manifested at a functional level. In conclusion, brivanib exhibits potential to cause clinically relevant pharmacokinetic DDIs and act as a modulator of ABCG2-mediated MDR. Our findings might be used as an important background for subsequent in vivo investigations and pave the way for the safe and effective use of brivanib in oncological patients.

Alectinib is a tyrosine kinase inhibitor currently used as a first-line treatment of anaplastic lymphoma kinase-positive metastatic nonsmall cell lung cancer (NSCLC). In the present work, we investigated possible interactions of this novel drug with ATP-binding cassette (ABC) drug efflux transporters and cytochrome P450 (P450) biotransformation enzymes that play significant roles in the phenomenon of multidrug resistance (MDR) of cancer cells as well as in pharmacokinetic drug-drug interactions. Using accumulation studies in Madin-Darby canine kidney subtype 2 (MDCKII) cells alectinib was identified as an inhibitor of ABCB1 and ABCG2 but not of ABCC1. In subsequent drug combination studies, we demonstrated the ability for alectinib to effectively overcome MDR in ABCB1- and ABCG2-overexpressing MDCKII and A431 cells. To describe the pharmacokinetic interaction profile of alectinib in a complete fashion, its possible inhibitory properties toward clinically relevant P450 enzymes (i.e., CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4, or CYP3A5) were evaluated using human P450-expressing insect microsomes, revealing alectinib as a poor interactor. Advantageously for its use in pharmacotherapy, alectinib further exhibited negligible potential to cause any changes in expression of ABCB1, ABCG2, ABCC1, CYP1A2, CYP3A4, and CYP2B6 in intestine, liver, and NSCLC models. Our in vitro observations might serve as a valuable foundation for future in vivo studies that could support the rationale for our conclusions and possibly enable providing more efficient and safer therapy to many oncological patients.

Preclinical drug safety assessment includes in vitro studies with physiologically relevant cell cultures. As an in vitro system for hepatic toxicology testing, we have been generating cell clones of human hepatoblastoma cell line HepG2 by lentiviral transduction of phase I cytochrome P450 (CYP) enzymes. Here, we present a stable CYP2C19-overexpressing HepG2 cell clone (HepG2-2C19 C1) showing an enzyme activity of approximately 82 pmol x min−1 x mg−1 total cellular protein. The phenotypic stability over several passages of HepG2-2C19 C1 renders them to be a suitable reference cell clone for benchmarking CYP2C19 enzyme activity. In addition, we were interested to analyze acute cytotoxicity of the model drug cyclophosphamide (CPA) metabolized by HepG2-2C19 C1 and by a previously generated CYP3A4-overexpressing HepG2 cell clone. Upon 10 mM CPA exposure, we were able to detect its metabolites 4-hydroxy-cyclophosphamide and acrolein in CYP3A4- and CYP2C19-expressing cell clones, but not in parental HepG2 cell line. XTT and ATP assays showed a modest reduction of cell viability of not more than 50% with high dose (10 mM) CPA treatment. By contrast, dramatic acute cytotoxic effects of CPA were evident by the formation of nuclear γH2AX foci and by increased cell death events. These effects were paralleled by substantial decreases of cell membrane integrity as measured by the trypan blue exclusion test. Our data on CYP enzyme overexpressing HepG2 cell clones clearly show that cytotoxicity of CPA is dramatically underestimated by standard metabolic activity tests. Thus, additional tests to quantitate DNA damage formation and cell death induction might be required to realistically assess cytotoxicity of such compounds.

Objectives Glioblastoma multiforme (GBM) mostly affects elderly patients. Adequate therapy especially in case of tumor recurrence is still under discussion, since most studies focus on patients under 65 years. We evaluated the impact of second surgery in regard to progression free survival (PFS) and overall survival (OAS) in elderly patients. Patients and methods 59 patients with recurrent glioblastoma multiforme were retrospectively evaluated. Patients were divided into three subgroups: stereotactic biopsy (STX), resection and second resection. Second and third group were pooled as "surgery" after first diagnosis. The median age for all groups was 71 years.The primary endpoint was overall survival. Statistical analysis was calculated using Kaplan-Meier analysis and SPSS. Results OAS was significantly longer for patients who had undergone surgery compared to the STX group. For patients who underwent reresection OAS was not significantly longer. Age (over 71) had no significant effect on OAS. PFS was significantly increased in patients who underwent surgery compared to those who underwent STX. PFS was not significantly longer in patients who underwent second resection. Furthermore PFS was not significantly different between patients under 71 and over. Conclusion OAS and PFS were significant increased for patients who underwent surgery compared to only STX. Patients showed prolonged survival of almost 4 months after they underwent reresection (p > 0.05). Therapy of elderly patients with GBM remains an individual decision with priority on quality of life. Clinical status, comorbidities and family background) should be taken into account.

Cyclophosphamide (CPA) is one of the most successful anticancer prodrugs that becomes effective after biotransformation in the liver resulting in the toxic metabolite acrolein. Cancer is often accompanied by thromboembolic events, which might be a result of dysfunctional endothelial cells due to CPA treatment. Here, the effect of 1 mM CPA or acrolein (10/50/100/500 μM) on human umbilical vein endothelial cells (HUVECs) was analyzed after two days of treatment. The addition of CPA or 10 μM acrolein did not affect HUVECs. However, concentrations of 100 μM and 500 μM acrolein significantly reduced the number of adherent cells by 86 ± 13% and 99 ± 1% and cell viability by 51 ± 29% and 93 ± 8% compared to the control. Moreover, pronounced stress fibers as well as multiple nuclei were observed and von Willebrand factor (vWF) was completely released. Lactate dehydrogenase was 8.5 ± 7.0-fold and 252.9 ± 42.9-fold increased showing a loss of cell membrane integrity. The prostacyclin and thromboxane secretion was significantly increased by the addition of 500 μM acrolein (43.1 ± 17.6-fold and 246.4 ± 106.3-fold) indicating cell activation/pertubation. High doses of acrolein led to HUVEC death and loss of vWF production. This effect might be associated with the increased incidence of thromboembolic events in cancer patients treated with high doses of CPA.

Aminopeptidase inhibitors are receiving attention as combination chemotherapeutic agents for the treatment of refractory acute myeloid leukemia. However, the factors determining therapeutic efficacy remain elusive. Here we identified the molecular basis of acquired resistance to CHR2863, an orally available hydrophobic aminopeptidase inhibitor prodrug with an esterase-sensitive motif, in myeloid leukemia cells. CHR2863 enters cells by diffusion and is retained therein upon esterase activity-mediated conversion to its hydrophilic active metabolite drug CHR6768, thereby exerting amino acid depletion. Carboxylesterases (CES) serve as candidate prodrug activating enzymes given CES1 expression in acute myeloid leukemia specimens. We established two novel myeloid leukemia sublines U937/CHR2863(200) and U937/CHR2863(5uM), with low (14-fold) and high level (270-fold) CHR2863 resistance. The latter drug resistant cells displayed: (i) complete loss of CES1-mediated drug activation associated with down-regulation of CES1 mRNA and protein, (ii) marked retention/sequestration of the prodrug, (iii) a substantial increase in intracellular lipid droplets, and (iv) a dominant activation of the pro-survival Akt/mTOR pathway. Remarkably, the latter feature coincided with a gain of sensitivity to the mTOR inhibitor rapamycin. These finding delineate the molecular basis of CHR2863 resistance and offer a novel modality to overcome this drug resistance in myeloid leukemia cells.

// Sarah Kammerer 1, 2 , Armin Sokolowski 1, 9 , Hubert Hackl 3 , Dieter Platzer 1 , Stephan Wenzel Jahn 4 , Amin El-Heliebi 5 , Daniela Schwarzenbacher 6 , Verena Stiegelbauer 6 , Martin Pichler 6, 7 , Simin Rezania 1, 2 , Heidelinde Fiegl 8 , Florentia Peintinger 4 , Peter Regitnig 4 , Gerald Hoefler 4 , Wolfgang Schreibmayer 1, 2 , Thomas Bauernhofer 2, 6 1 Molecular Physiology Group, Institute of Biophysics, Medical University of Graz, Austria 2 Research Unit on Ion Channels and Cancer Biology, Medical University of Graz, Austria 3 Division of Bioinformatics, Biocenter, Medical University of Innsbruck, Austria 4 Institute of Pathology, Medical University of Graz, Austria 5 Institute of Cell Biology, Histology and Embryology, Medical University of Graz, Austria 6 Division of Oncology, Department of Internal Medicine, Medical University of Graz, Austria 7 Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA 8 Department of Gynecology and Obstetrics, Medical University of Innsbruck, Austria 9 Present address: Division of Prosthodontics, Restorative Dentistry, Periodontology and Implantology, Medical University of Graz, Austria Correspondence to: Thomas Bauernhofer, email: thomas.bauernhofer@medunigraz.at Keywords: KCNJ3, GIRK1, biomarker, estrogen receptor positive breast cancer, RNA in situ hybridization Received: June 04, 2016 Accepted: October 26, 2016 Published: November 08, 2016 ABSTRACT Numerous studies showed abnormal expression of ion channels in different cancer types. Amongst these, the potassium channel gene KCNJ3 (encoding for GIRK1 proteins) has been reported to be upregulated in tumors of patients with breast cancer and to correlate with positive lymph node status. We aimed to study KCNJ3 levels in different breast cancer subtypes using gene expression data from the TCGA, to validate our findings using RNA in situ hybridization in a validation cohort (GEO ID GSE17705), and to study the prognostic value of KCNJ3 using survival analysis. In a total of > 1000 breast cancer patients of two independent data sets we showed a) that KCNJ3 expression is upregulated in tumor tissue compared to corresponding normal tissue ( p < 0.001), b) that KCNJ3 expression is associated with estrogen receptor (ER) positive tumors ( p < 0.001), but that KCNJ3 expression is variable within this group, and c) that ER positive patients with high KCNJ3 levels have worse overall ( p < 0.05) and disease free survival probabilities ( p < 0.01), whereby KCNJ3 is an independent prognostic factor ( p

Mechanical interaction between cells - specifically distortion of tensional homeostasis-emerged as an important aspect of breast cancer genesis and progression. We investigated the biophysical characteristics of mechanosensitive ion channels (MSCs) in the malignant MCF-7 breast cancer cell line. MSCs turned out to be the most abundant ion channel species and could be activated by negative pressure at the outer side of the cell membrane in a saturable manner. Assessing single channel conductance (GΛ) for different monovalent cations revealed an increase in the succession: Li(+)Na(+)K(+) ≈Rb(+) ≈ Cs(+). Divalent cations permeated also with the order: Ca(2+)Ba(2+). Comparison of biophysical properties enabled us to identify MSCs in MCF-7 as ion channels formed by the Piezo1 protein. Using patch clamp technique no functional MSCs were observed in the benign MCF-10A mammary epithelial cell line. Blocking of MSCs by GsMTx-4 resulted in decreased motility of MCF-7, but not of MCF-10A cells, underscoring a possible role of Piezo1 in invasion and metastatic propagation. The role of Piezo1 in biology and progression of breast cancer is further substantiated by markedly reduced overall survival in patients with increased Piezo1 mRNA levels in the primary tumor.

Mechanical stress is increasingly recognized as a cancerogenic factor in breast cancer. We investigated the biophysical characteristics of mechano-sensitive channels (MSCs) in the breast cancer cell line MCF7 with patch clamp methods.MSCs were present in 132 out of 258 cell-attached membrane patches. MSCs could be activated by negative pressure at the outer side of the membrane in a saturable manner (EP50: 41.2 ± 0.5 mbar (N=13).When K+ was predominantly present in the extracellular pipette solution, single channel conductance exerted to be 25.6± 0.4 pS (N=8). When complete ion selectivity was assessed, conductivity was found to increase in the following order: Li+ < Na+ < K+≈Rb+ ≈ Cs+. Furthermore, conductivity was smaller for divalent cations (100 mmole/L compared to 153 mmole/L) with the order: Ca2+ < Ba2+ < K + ≈ Rb + ≈ Cs +. We compared the biophysical properties of MSCs with a recently discovered mechanosensitive cation channel, the human Piezo1 protein, heterologously overexpressed in HEK293 cells. Single channel conductances were indistinguishable between MSCs from MCF7 and hPiezo1 in HEK293 cells, both when 100% K + and 50% K + / 50% Na + were used as permeant ions.MSCs occur in MCF7 breasts cancer cells, providing a sensorium for mechanical stress. Ion selectivity studies show that divalents like Ca2+ can permeate to a considerable extend. Moreover, permeation of monovalents is apparently restricted by the size of the ions hydrate shell, as indicated by the smaller conductivities for Na + and Li +, respectively, indicating that the ion permeation mechanism through MSCs may be different to the cation channels crystallized so far.This research is supported by grants from the Austrian Research Foundation (FWF22974 (WS); KLIF182 (TB)).

Mortality of breast cancer is very high when it metastases to distant organs. New early tumor markers and mechanistic insight into carcinogenesis and metastasisation are needed to treat the disease at curable stages. GIRK channels are activated by GPCRs and regulate resting potential and excitability of neurons, myocytes and other cells. Recently GIRK proteins have been associated with endocrine adenomas and also breast cancer (Stringer et al.2001, Brevet et a.l 2008 and Choi et al.2009). In this study we analyzed the vital parameters of cancerous and noncancerous breast cell lines when human GIRK1 and splice variants (hG1a, hG1c, hG1d) are overexpressed or silenced.GIRK1a, GIRK1c and GIRK1d were stably overexpressed and knocked out in breast cell lines MCF7, MDA-MB-231 and MCF 10A. Vital parameters including invasion, wound healing, adhesion, proliferation and motility were evaluated.Our findings revealed that overexpression of GIRK1a significantly increased the velocity 0.102±0.035 (μm/min) in overexpresssed vs. 0.05±0.02 in vector control cells (P˂0.001) and motility coefficient 0.2±0.3 (μm2/min) in overexpresssed vs. 0.05±0.06 in vector control cells (P˂0.001) of the MCF7 cell lines. Overexpression of hG1c in MCF7 significantly increased invasiveness of the cells (P˂0.001) as measured by matrigel assay. Overexpression of the GIRK1 and splice variants didn't have significant effect on proliferation, wound healing and adhesion of the MCF7 cells.Stably overexpression of GIRK1 and splice variants in MCF7 cause increased velocity, motility coefficient and invasion of the cells. Expression of GIRK might be a new diagnostic biomarker of breast cancer and possibly is causally involved in metastasisation.Acknowledgements: The research is funded by the Austrian Science Foundation (FWF; P22974-B19 to W. S and KLIF 182 to T. B).