Dual Inhibitors as a New Challenge for Cancer Multidrug Resistance Treatment

BACKGROUND

Dual-targeting in cancer treatment by a single drug is an unconventional approach in relation to drug combinations. The rationale for the development of dualtargeting agents is to overcome incomplete efficacy and drug resistance frequently present when applying individual targeting agents. Consequently, -a more favorable outcome of cancer treatment is expected with dual-targeting strategies.

METHODS

We reviewed the literature, concentrating on the association between clinically relevant and/or novel dual inhibitors with the potential to modulate multidrug resistant phenotype of cancer cells, particularly the activity of P-glycoprotein. A balanced analysis of content was performed to emphasize the most important findings and optimize the structure of this review.

RESULTS

Two-hundred and forty-five papers were included in the review. The introductory part was interpreted by 9 papers. Tyrosine kinase inhibitors' role in the inhibition of Pglycoprotein and chemosensitization was illustrated by 87 papers. The contribution of naturalbased compounds in overcoming multidrug resistance was reviewed using 92 papers, while specific dual inhibitors acting against microtubule assembling and/or topoisomerases were described with 55 papers. Eleven papers gave an insight into a novel and less explored approach with hybrid drugs. Their influence on P-glycoprotein and multidrug resistance was also evaluated.

CONCLUSION

These findings bring into focus rational anticancer strategies with dual-targeting agents. Most evaluated synthetic and natural drugs showed a great potential in chemosensitization. Further steps in this direction are needed for the optimization of anticancer treatment.

A New Strategy for Glioblastoma Treatment: In Vitro and In Vivo Preclinical Characterization of Si306, a Pyrazolo[3,4-d]Pyrimidine Dual Src/P-Glycoprotein Inhibitor

Overexpression of P-glycoprotein (P-gp) and other ATP-binding cassette (ABC) transporters in multidrug resistant (MDR) cancer cells is responsible for the reduction of intracellular drug accumulation, thus decreasing the efficacy of chemotherapeutics. P-gp is also found at endothelial cells' membrane of the blood-brain barrier, where it limits drug delivery to central nervous system (CNS) tumors. We have previously developed a set of pyrazolo[3,4-d]pyrimidines and their prodrugs as novel Src tyrosine kinase inhibitors (TKIs), showing a significant activity against CNS tumors in in vivo. Here we investigated the interaction of the most promising pair of drug/prodrug with P-gp at the cellular level. The tested compounds were found to increase the intracellular accumulation of Rho 123, and to enhance the efficacy of paclitaxel in P-gp overexpressing cells. Encouraging pharmacokinetics properties and tolerability in vivo were also observed. Our findings revealed a novel role of pyrazolo[3,4-d]pyrimidines which may be useful for developing a new effective therapy in MDR cancer treatment, particularly against glioblastoma.

In vitro biomimetic models for glioblastoma-a promising tool for drug response studies

The poor response of glioblastoma to current treatment protocols is a consequence of its intrinsic drug resistance. Resistance to chemotherapy is primarily associated with considerable cellular heterogeneity, and plasticity of glioblastoma cells, alterations in gene expression, presence of specific tumor microenvironment conditions and blood-brain barrier. In an attempt to successfully overcome chemoresistance and better understand the biological behavior of glioblastoma, numerous tri-dimensional (3D) biomimetic models were developed in the past decade. These novel advanced models are able to better recapitulate the spatial organization of glioblastoma in a real time, therefore providing more realistic and reliable evidence to the response of glioblastoma to therapy. Moreover, these models enable the fine-tuning of different tumor microenvironment conditions and facilitate studies on the effects of the tumor microenvironment on glioblastoma chemoresistance. This review outlines current knowledge on the essence of glioblastoma chemoresistance and describes the progress achieved by 3D biomimetic models. Moreover, comprehensive literature assessment regarding the influence of 3D culturing and microenvironment mimicking on glioblastoma gene expression and biological behavior is also provided. The contribution of the blood-brain barrier as well as the blood-tumor barrier to glioblastoma chemoresistance is also reviewed from the perspective of 3D biomimetic models. Finally, the role of mathematical models in predicting 3D glioblastoma behavior and drug response is elaborated. In the future, technological innovations along with mathematical simulations should create reliable 3D biomimetic systems for glioblastoma research that should facilitate the identification and possibly application in preclinical drug testing and precision medicine.

Purine nucleoside analog--sulfinosine modulates diverse mechanisms of cancer progression in multi-drug resistant cancer cell lines

Achieving an effective treatment of cancer is difficult, particularly when resistance to conventional chemotherapy is developed. P-glycoprotein (P-gp) activity governs multi-drug resistance (MDR) development in different cancer cell types. Identification of anti-cancer agents with the potential to kill cancer cells and at the same time inhibit MDR is important to intensify the search for novel therapeutic approaches. We examined the effects of sulfinosine (SF), a quite unexplored purine nucleoside analog, in MDR (P-gp over-expressing) non-small cell lung carcinoma (NSCLC) and glioblastoma cell lines (NCI-H460/R and U87-TxR, respectively). SF showed the same efficacy against MDR cancer cell lines and their sensitive counterparts. However, it was non-toxic for normal human keratinocytes (HaCaT). SF induced caspase-dependent apoptotic cell death and autophagy in MDR cancer cells. After SF application, reactive oxygen species (ROS) were generated and glutathione (GSH) concentration was decreased. The expression of key enzyme for GSH synthesis, gamma Glutamyl-cysteine-synthetase (γGCS) was decreased as well as the expression of gst-π mRNA. Consequently, SF significantly decreased the expression of hif-1α, mdr1 and vegf mRNAs even in hypoxic conditions. SF caused the inhibition of P-gp (coded by mdr1) expression and activity. The accumulation of standard chemotherapeutic agent – doxorubicin (DOX) was induced by SF in concentration- and time-dependent manner. The best effect of SF was obtained after 72 h when it attained the effect of known P-gp inhibitors (Dex-verapamil and tariquidar). Accordingly, SF sensitized the resistant cancer cells to DOX in subsequent treatment. Furthermore, SF decreased the experssion of vascular endothelial growth factor (VEGF) on mRNA and protein level and modulated its secretion. In conclusion, the effects on P-gp (implicated in pharmacokinetics and MDR), GSH (implicated in detoxification) and VEGF (implicated in tumor-angiogenesis and progression) qualify SF as multi-potent anti-cancer agent, which use must be considered, in particular for resistant malignancies.

Jatrophane diterpenoids with multidrug-resistance modulating activity from the latex of Euphorbia nicaeensis

Seven previously undescribed jatrophane diterpenoids, nicaeenin A-G, with eight known jatrophane diterpenoids, namely euphodendrophanes A-C, F, N, O, Q, S, were isolated from latex of Euphorbia nicaeensis collected in Serbia. The chemical structures of the compounds were determined by spectroscopic analysis including 1D and 2D NMR and HRESIMS experiments. All but one of the previously undescribed jatrophanes, showed significant potential to inhibit P-glycoprotein (P-gp) activity in two MDR cancer cells (NCI-H460/R and DLD1-TxR). The most powerful were nicaeenin F and nicaeenin G. Moreover nicaeenin G significantly stronger sensitized NCI-H460/R cells to DOX than Dex-VER.

Sulfocoumarins, specific carbonic anhydrase IX and XII inhibitors, interact with cancer multidrug resistant phenotype through pH regulation and reverse P-glycoprotein mediated resistance

New 6-triazolyl-substituted sulfocoumarins were described as potent inhibitors of the transmembrane human carbonic anhydrase isoforms, CAIX and CAXII. These membrane associated enzymes that maintain pH and CO₂ homeostasis are involved in cancer progression, invasion, and resistance to therapy. Recently, it was shown that CAXII expression associates with the expression of P-glycoprotein in multidrug resistant cancer cells. CAXII regulates P-glycoprotein activity by maintaining high intracellular pHi. In this study, the activity of three new sulfocoumarins was evaluated in three sensitive and corresponding multidrug resistant cancer cell lines with increased P-glycoprotein expression (non-small cell lung carcinoma, colorectal carcinoma and glioblastoma). Compound 3 showed the highest potential for cancer cell growth inhibition in all tested cell lines. Flow cytometric analyses showed that compound 3 induced intracellular acidification, cell cycle arrest in G₂/M phase and necrosis in non-small cell lung carcinoma cells. Compound 3 demonstrated irreversible, concentration- and time-dependent inhibition of P-glycoprotein activity in multidrug resistant non-small cell lung carcinoma cells. The suppression of P-glycoprotein activity was accompanied with increased P-glycoprotein expression suggesting a compensatory mechanism of multidrug resistant cancer cells. In addition, compound 3 was able to sensitize multidrug resistant non-small cell lung carcinoma cells to doxorubicin. Overall, results imply that compound 3 has multidrug resistance modulating effect through intracellular acidification and subsequent inhibition of P-glycoprotein activity.

Intraoperative cytology of clear cell carcinoma of the ovary

OBJECTIVE

To describe the cytomorphology of clear cell carcinoma (CCC) of the ovary in intraoperative samples of peritoneal fluid, imprint and scraping samples of the tumour tissue.

STUDY DESIGN

Fourteen histologically confirmed cases, stained by standard cytological procedures, were analysed by light microscopy.

RESULTS

In 33.3% of peritoneal fluid samples and 92.9% of imprint and scraping cytological samples, besides variable clear cell cellular morphology, one or both distinct cytological characteristics were observed: eosinophilic, hyaline, extracellular, globular substance with or without formation of a 'raspberry' body and an eosinophilic, intracytoplasmic inclusions. These structures were clearly seen only in samples stained by May-Grünwald-Giemsa.

CONCLUSION

Using cytological analysis of imprint and scraping samples of ovarian tumours it is possible to make a precise intraoperative cytological diagnosis in most cases of CCC of the ovary.

Morphometry and digital AgNOR analysis in cytological imprints of benign, borderline and malignant serous ovarian tumours

AIM

The aim of the study was to determine values of a quantitative morphometry analysis of nuclear characteristics and argyrophilic nucleolar organizer regions (AgNORs) in differential cytodiagnosis of benign, atypically proliferating (borderline) and malignant serous ovarian tumours.

METHODS

Cytological imprints of benign (n = 20), borderline (n = 19) and malignant (n = 20) ovarian serous tumours were analysed. A computerized, digital analysis was used to determine morphometric nuclear features, the number and characteristics of single AgNORs, cluster AgNORs, total AgNOR and AgNOR area/nucleus (relative area) ratio. According to their size AgNORs were classified in three categories. A one-way variance analysis and post hoc test (Scheffé) were used for statistical analysis.

RESULTS

The morphometric nuclear analysis showed that benign, borderline and malignant serous ovarian tumours are statistically different (P < 0.001) according to the area and outline, the values being highest in malignant tumours and lowest in the borderline group. Digital analysis of AgNORs in benign, borderline and malignant groups showed that the total AgNOR number increases with progression of the lesion (meaning tumour malignancy) significantly (P < 0.001) between benign and malignant as well as between borderline and malignant serous ovarian tumours (P < 0.001). The progression of the lesion malignancy was accompanied by a significant (P < 0.001) progressive increase of the total and relative AgNOR area per nucleus. The AgNOR size increases from benign to malignant tumours and a statistically significant difference (P < 0.001) was observed in all three groups regarding small and large AgNORs.

CONCLUSION

Combining different markers of morphometric nuclear characteristics and AgNOR values could improve differential cytodiagnosis of benign, borderline and malignant serous ovarian tumours.

Development and Validation of a Long-Term 3D Glioblastoma Cell Culture in Alginate Microfibers as a Novel Bio-Mimicking Model System for Preclinical Drug Testing

Background: Various three-dimensional (3D) glioblastoma cell culture models have a limited duration of viability. Our aim was to develop a long-term 3D glioblastoma model, which is necessary for reliable drug response studies. Methods: Human U87 glioblastoma cells were cultured in alginate microfibers for 28 days. Cell growth, viability, morphology, and aggregation in 3D culture were monitored by fluorescent and confocal microscopy upon calcein-AM/propidium iodide (CAM/PI) staining every seven days. The glioblastoma 3D model was validated using temozolomide (TMZ) treatments 3 days in a row with a recovery period. Cell viability by MTT and resistance-related gene expression (MGMT and ABCB1) by qPCR were assessed after 28 days. The same TMZ treatment schedule was applied in 2D U87 cell culture for comparison purposes. Results: Within a long-term 3D model system in alginate fibers, U87 cells remained viable for up to 28 days. On day 7, cells formed visible aggregates oriented to the microfiber periphery. TMZ treatment reduced cell growth but increased drug resistance-related gene expression. The latter effect was more pronounced in 3D compared to 2D cell culture. Conclusion: Herein, we described a long-term glioblastoma 3D model system that could be particularly helpful for drug testing and treatment optimization.

Synthetic Phosphonic Acids as Potent Tools to Study Phosphonate Enzymology

Phosphonic acids are highly stable phosphorus-containing compounds, which have been proposed as important intermediates in the global phosphorus cycle. Biogenic phosphonates as well as their synthetic analogues play an important role as potential enzyme inhibitor drugs and as alternative phosphorus source for microbes. Despite these properties, their metabolism is still poorly understood. New degradative pathways and unknown compounds are identified at fast pace. However, most of these pathways include a variety of unique enzymatic transformations, which are difficult to characterize – especially without sufficient amounts of the potential substrates and intermediates of the postulated transformations in hands. Thus, there is a great need for the development of synthetic methodologies to access phosphonic acids in high yields and in enantiomerically pure form for the use in enzymatic studies and in studies on the biological activity of newly isolated natural products, which are often only obtained in low yields. In this Synpacts article we aim at highlighting our recent contributions to this field.

1 Introduction2 Phosphonates as Alternative Phosphorus Source

3 The Application of Phosphonates in Enzymatic Studies

4 Conclusion

Mutual regulation and targeting of multidrug resistance and cancer stem phenotype

Targeting stemness mechanisms leads to the suppression of ABC transporter activity and elimination of CSCs.

[Clinical manifestations of neuroblastoma in children and their effect on prognosis]

There are many prognostic factors in neuroblastoma. In this paper we analyzed the prognostic importance of some clinical factors like age, stage of disease, primary localization and neurological manifestations in children with neuroblastoma. We analyzed 58 children with neuroblastoma who were treated from 1970 to 1988 at the Haematology Department of Children's University Hospital in Belgrade. According to statistical evaluation presence of neurological manifestations and age were not important prognostic factors in children with neuroblastoma. Only primary localization of the tumour and stage of the disease had significant influence on prognosis.

Parenteral Nanoemulsion for Optimized Delivery of GL-II-73 to the Brain-Comparative In Vitro Blood-Brain Barrier and In Vivo Neuropharmacokinetic Evaluation

Background/Objectives: GL-II-73 is a positive allosteric modulator that is selective for α5GABAA receptors and has physicochemical properties that favor nanocarrier formulations when parenteral delivery to the central nervous system is desired. Our aim was to develop an optimized nanoemulsion containing GL-II-73 and subsequently test whether this would improve permeation across the blood-brain barrier (BBB) and availability in the brain. Methods: The nanoemulsions were formulated and subjected to detailed physiochemical characterization. The optimized formulation was tested in comparison to a solution of GL-II-73 in the appropriate solvent in an in vitro model of the blood-brain barrier based on human induced pluripotent stem cell-derived microvascular endothelial cells, astrocytes, and pericytes. Plasma and brain exposure to GL-II-73 and its metabolite MP-III-022 was investigated in an in vivo neuropharmacokinetic study in rats exposed to the selected nanoemulsion and the conventional solution formulation. Results: The selected biocompatible nanoemulsion exhibited satisfactory physicochemical properties for parenteral administration, with a Z-ave of 122.0 ± 1.5, PDI of 0.123 ± 0.009 and zeta potential of -40.7 ± 1.5, pH of 5.16 ± 0.04, and adequate stability after one year of storage, and allowed the localization of GL-II-73 in the stabilization layer. The permeability of GL-II-73 through the BBB was twice as high with the selected nanoemulsion as with the solution. The availability of GL-II-73 and MP-III-022 (also a positive allosteric modulator selective for α5GABAA receptors) in the brain was 24% and 61% higher, respectively, after intraperitoneal administration of the nanoemulsion compared to the solution; the former increase was statistically significant. Conclusions: The increased permeability in vitro proved to be a good predictor for the improved availability of GL-II-73 in brain tissue in vivo from the formulation obtained by encapsulation in a nanoemulsion. The putative additive effect of the parent molecule and its metabolite MP-III-022 could lead to enhanced and/or prolonged modulation of α5GABAA receptors in the brain.

Treatment of climacteric complaints with oestriol

150 women with serious climacteric complaints were continuously treated from January, 1970, up to April, 1972, with Ovestin¿, an orally effective preparation containing 1 mg of oestriol per tablet. After one month of treatment subjective complaints were already considerably improved. Oestrogenic activity was markedly increased, according to vaginal smears and total gonadotrophin excretion in the urine. Its high tolerance and beneficial therapeutic effect make Ovestin the preparation of choice in the treatment of the climacteric syndrome.

Intravenous Nanoemulsions Loaded with Phospholipid Complex of a Novel Pyrazoloquinolinone Ligand for Enhanced Brain Delivery

Background/Objectives: The novel pyrazoloquinolinone ligand CW-02-79 shows a unique profile of selective binding to σ2 receptors, but its poor solubility in both water and lipids makes its research and development a burdensome task. We aimed to develop a phospholipid-complex-based nanoemulsion formulation containing CW-02-79 suitable for intravenous administration in preclinical research. Methods: The decorated and undecorated nanoemulsions were formulated and subjected to detailed physiochemical characterization. The delivery and exposure to CW-02-79 from selected nanoemulsions were examined in the in vitro blood-brain barrier model based on human-induced pluripotent stem-cell-derived microvascular endothelial cells, astrocytes, and pericytes, and in vivo neuropharmacokinetic study in rats, respectively. Results: The developed biocompatible nanoemulsions loaded with a CW-02-79-phospholipid complex at a mass ratio of 1:10 exhibited a small droplet size and narrow size distribution, with satisfactory physicochemical stability during steam sterilization and short-term storage at 25 °C. The analysis of protein binding interactions revealed that the PEGylated nanoemulsions had fewer observable interactions compared to the undecorated nanoemulsions, especially when 0.2% DSPE-PEG2000 and 0.1% DSPE-PEG2000-mannose were combined. An in vitro BBB study demonstrated that a substantial part of CW-02-79 present in the applied nanoemulsion is able to permeate the barrier. The quantification of CW-02-79 in plasma/brain homogenate and calculated pharmacokinetic parameters confirmed good systemic and brain availability after intravenous administration. There were subtle differences in the pharmacokinetic parameters in favor of a dual surface-functionalized nanoemulson containing the glucose transporter-1-targeting ligand (mannose). Conclusions: The developed and characterized nanoemulsions enable substantial brain exposure to CW-02-79 as a prerequisite for a pharmacologically and clinically relevant selective modulation of σ2 receptors.

[The importance of work conditions in the textile industry to worker absenteeism]

A study was performed in the "Belgrade Wool Co." as a retrospective epidemiological investigation, for a three-year period (1985-1987), on a sample of 134 blue-collar female workers. The following statistically significant facts were established: in favourable working conditions (sewing department) the older workers (above the age of 35 years) were absent from work because of illness longer than the younger workers; the number of the younger workers (age 35 years or under) with sick absences increased as working conditions worsened (wool-mills compared to sewing departments). Respiratory diseases made the most frequent cause of absence from work. Harder working conditions influenced the morbidity structure as cause of absenteeism resulting in the rise of prevalence of mental disorders among the younger workers, and of locomotor and circulatory diseases among the older ones. The younger workers showed a rising trend in the severity and frequency of injuries as causes of absence from work, which correlated with the degree of deterioration of working conditions. Finally, under extremely hard working conditions (wool-mills) the rate of occupationally induced injuries among the younger workers was as much as three times higher than among the older ones, and the duration of sick absences was longer.

[Dexamethasone modifies development of human long-term bone marrow culture in dose dependent manner]

Dexter's long-term bone marrow cultures were performed to evaluate the effects of exponentially decreasing concentrations of dexamethasone (10(-2) M to 10(-8) M) on proliferation, differentiation and oxidative burst of the human bone marrow cells. High concentrations of dexamethasone show antiproliferative effect on stromal and haemopoietic cells. There was a small number of adipocytes and macrophages, with predominance of fibroblasts. Cultures, grown in lower concentration of dexamethasone (10(-4) M to 10(-7) M) consisted of a greater number of adipocytes and macrophages. The number of haematopoietic islands was increased and differentiation of haematopoietic cells was pronounced. The adipocytes proliferation was more pronounced, while their maturation was slowed down when low concentrations of dexamethasone were used. The size and the number of haematopoietic islands were reduced. Optimal concentration of dexamethasone for normal growth of both stromal and haematopoietic cells were between 10(-5) M and 10(-7) M. NBT reduction ability of myeloid and stromal cells increased using the higher concentrations of dexamethasone. However, only myeloid cells were NBT positive when lower concentrations were used. Dexamethasone acted as functional and maturational factor for oxidative burst of stromal, as well as myeloid haematopoietic cells.

[The effect of a preventive health care program in a textile plant]

A two-month field experiment was carried out on a sample of 95 women spinners and weavers in a textile plant. In the experimental group, which consisted of 54 workers, a programme of four preventive health measures was applied. The workers were asked to wear a combination of ear-muffs and cotton-wool offering optimal hearing protection and to take up individual mini programmes of physical exercise at work; they were offered a meal of the Pliva dietetic preparation Vitamalt before work and Donat-Mg natural mineral water from Zdravilisce Rogaska Slatina as a magnesium supplement. The measures from the programme were accepted and respected by 85-94% of the workers. As a result, fatigue at work was significantly reduced, and the subjectively estimated work satisfaction was markedly improved. A statistically insignificant trend towards the rise of productivity was also noticed during the period of programme application.