Stereoisomers in clinical oncology: why it is important to know what the right and left hands are doing

The activity of pyrazolo[4,3-e][1,2,4]triazine and pyrazolo[4,3-e]tetrazolo[1,5-b][1,2,4]triazine sulphonamide derivatives in monolayer and spheroid breast cancer cell cultures

In the last decade, an increasing interest in compounds containing pyrazolo[4,3-e][1,2,4]triazine moiety is observed. Therefore, the aim of the research was to synthesise a novel sulphonyl pyrazolo[4,3-e][1,2,4]triazines (2a, 2b) and pyrazolo[4,3-e]tetrazolo[1,5-b][1,2,4]triazine sulphonamide derivatives (3a, 3b) to assess their anticancer activity. The MTT assay showed that 2a, 2b, 3a, 3b have stronger cytotoxic activity than cisplatin in both breast cancer cells (MCF-7 and MDA-MB-231) and exhibited weaker effect on normal breast cells (MCF-10A). The obtained results showed that the most active compound 3b increased apoptosis via caspase 9, caspase 8, and caspase 3/7. It is worth to note that compound 3b suppressed NF-κB expression and promoted p53, Bax, and ROS which play important role in activation of apoptosis. Moreover, our results confirmed that compound 3b triggers autophagy through increased formation of autophagosomes, expression of beclin-1 and mTOR inhibition. Thus, our study defines a possible mechanism underlying 3b-induced anti-cancer activity against breast cancer cell lines.

The Effects of Protein Phosphatase 2A Activation with Novel Tricyclic Sulfonamides on Hepatoblastoma

BACKGROUND

The tumor suppressor, protein phosphatase 2A (PP2A), is downregulated in hepatoblastoma. We aimed to examine the effects of two novel compounds of the tricyclic sulfonamide class, ATUX-3364 (3364) and ATUX-8385 (8385), designed to activate PP2A without causing immunosuppression, on human hepatoblastoma.

METHODS

An established human hepatoblastoma cell line, HuH6, and a human hepatoblastoma patient-derived xenograft, COA67, were treated with increasing doses of 3364 or 8385, and viability, proliferation, cell cycle and motility were investigated. Cancer cell stemness was evaluated by real-time PCR and tumorsphere forming ability. Effects on tumor growth were examined using a murine model.

RESULTS

Treatment with 3364 or 8385 significantly decreased viability, proliferation, cell cycle progression and motility in HuH6 and COA67 cells. Both compounds significantly decreased stemness as demonstrated by decreased abundance of OCT4, NANOG, and SOX2 mRNA. The ability of COA67 to form tumorspheres, another sign of cancer cell stemness, was significantly diminished by 3364 and 8385. Treatment with 3364 resulted in decreased tumor growth in vivo.

CONCLUSION

Novel PP2A activators, 3364 and 8385, decreased hepatoblastoma proliferation, viability, and cancer cell stemness in vitro. Animals treated with 3364 had decreased tumor growth. These data provide evidence for further investigation of PP2A activating compounds as hepatoblastoma therapeutics.

Molecular and Functional Analysis of Sunitinib-Resistance Induction in Human Renal Cell Carcinoma Cells

Resistance in clear cell renal cell carcinoma (ccRCC) against sunitinib is a multifaceted process encompassing numerous molecular aberrations. This induces clinical complications, reducing the treatment success. Understanding these aberrations helps us to select an adapted treatment strategy that surpasses resistance mechanisms, reverting the treatment insensitivity. In this regard, we investigated the dominant mechanisms of resistance to sunitinib and validated an optimized multidrug combination to overcome this resistance. Human ccRCC cells were exposed to single or chronic treatment with sunitinib to obtain three resistant clones. Upon manifestation of sunitinib resistance, morphometric changes in the cells were observed. At the molecular level, the production of cell membrane and extracellular matrix components, chemotaxis, and cell cycle progression were dysregulated. Molecules enforcing the cell cycle progression, i.e., cyclin A, B1, and E, were upregulated. Mass spectrometry analysis revealed the intra- and extracellular presence of N-desethyl sunitinib, the active metabolite. Lysosomal sequestration of sunitinib was confirmed. After treatment with a synergistic optimized drug combination, the cell metabolic activity in Caki-1-sunitinib-resistant cells and 3D heterotypic co-cultures was reduced by >80%, remaining inactive in non-cancerous cells. These results demonstrate geno- and phenotypic changes in response to sunitinib treatment upon resistance induction. Mimicking resistance in the laboratory served as a platform to study drug responses.

Molecular determinants of pro-arrhythmia proclivity of d- and l-sotalol via a multi-scale modeling pipeline

Drug isomers may differ in their proarrhythmia risk. An interesting example is the drug sotalol, an antiarrhythmic drug comprising d- and l- enantiomers that both block the hERG cardiac potassium channel and confer differing degrees of proarrhythmic risk. We developed a multi-scale in silico pipeline focusing on hERG channel – drug interactions and used it to probe and predict the mechanisms of pro-arrhythmia risks of the two enantiomers of sotalol. Molecular dynamics (MD) simulations predicted comparable hERG channel binding affinities for d- and l-sotalol, which were validated with electrophysiology experiments. MD derived thermodynamic and kinetic parameters were used to build multi-scale functional computational models of cardiac electrophysiology at the cell and tissue scales. Functional models were used to predict inactivated state binding affinities to recapitulate electrocardiogram (ECG) QT interval prolongation observed in clinical data. Our study demonstrates how modeling and simulation can be applied to predict drug effects from the atom to the rhythm for dl-sotalol and also increased proarrhythmia proclivity of d- vs. l-sotalol when accounting for stereospecific beta-adrenergic receptor blocking.

Comparison of the levogyre and dextro-levogyre forms of leucovorin in a phase III trial of bimonthly LV5FU2 versus monthly 5-fluorouracil and high-dose leucovorin for patients with stage II and III colon cancer (GERCOR C96.1)

BACKGROUND

These analyses compare the safety and efficacy of 2 forms (levogyre [L] and dextro-levogyre [DL]) of leucovorin (LV) when used with 5-fluorouracil (5-FU) for the adjuvant treatment of patients with stage II and III colon cancer.

MATERIALS AND METHODS

The analysis used primary efficacy and safety data of a phase III trial comparing monthly 5-FU/LV or bimonthly LV5FU2 (LV 200 mg/m2 intravenously over 2 hours followed by 5-FU 400 mg/m2 bolus and then 600 mg/m2 continuous intravenous infusion over 22 hours, days 1 and 2, every 2 weeks). In both regimens, depending on the choice made by each center, patients received either DL-LV (200 mg/m2) or L-LV (100 mg/m2).

RESULTS

L-LV and DL-LV were administered respectively to 60% (n = 519) and 40% (n = 357) of the patients. Important prognostic characteristics were well balanced between the 2 groups. The proportion of any grade 3/4 toxicity was 20% in the L-LV group and 17% in the DL-LV group. There was no statistical difference in terms of toxicity between the 2 groups. The median follow-up time was 6.1 years. There were no statistically significant differences between L-LV and DL-LV in terms of either disease-free survival (66.7% vs. 67.2%; hazard ratio [HR], 1.03; 95% CI, 0.82-1.31; P = .78) or overall survival (78.2% vs. 74.5%; HR, 1.28; 95% CI, 0.97-1.69; P = .078).

CONCLUSION

This study supports the use of either DL (200 mg/m2) or L (100 mg/m2) LV in association with 5-FU as adjuvant treatment of patients with colon cancer.

Drug disposition in three dimensions: an update on stereoselectivity in pharmacokinetics

Many marketed drugs are chiral and are administered as the racemate, a 50:50 combination of two enantiomers. Pharmacodynamic and pharmacokinetic differences between enantiomers are well documented. Because of enantioselectivity in pharmacokinetics, results of in vitro pharmacodynamic studies involving enantiomers may differ from those in vivo where pharmacokinetic processes will proceed. With respect to pharmacokinetics, disparate plasma concentration vs time curves of enantiomers may result from the pharmacokinetic processes proceeding at different rates for the two enantiomers. At their foundation, pharmacokinetic processes may be enantioselective at the levels of drug absorption, distribution, metabolism and excretion. In some circumstances, one enantiomer can be chemically or biochemically inverted to its antipode in a unidirectional or bidirectional manner. Genetic consideration such as polymorphic drug metabolism and gender, and patient factors such as age, disease state and concomitant drug intake can all play a role in determining the relative plasma concentrations of the enantiomers of a racemic drug. The use of a nonstereoselective assay method for a racemic compound can lead to difficulties in interpretation of data from, for example, bioequivalence or dose/concentration vs effect assessments. In this review data from a number of representative studies involving pharmacokinetics of chiral drugs are presented and discussed.

Kinetic study of CYP3A4 activity on verapamil by capillary electrophoresis

The use of capillary electrophoresis (CE) for the determination of CYP3A4 activity with verapamil as a substrate was investigated. CYP3A4 activity was determined by the quantitation of the product, norverapamil, based on separation by CE. The separation conditions were as follows: capillary, 80.5 cm (75 microm i.d., 72 cm effective length); 50 mM sodium phosphate buffer (pH 8.8); 20 kV (100 microA) applied voltage; UV detection at 200 nm; capillary temperature, 25 degrees C. With the developed CYP3A4 activity assay and the Lineweaver-Burk equation, the Michaelis-Menten parameters Km and Vmax for formation of norverapamil from verapamil in the presence of CYP3A4 were determined and were 22.8+/-2.5 microM and 7.67+/-0.26 pmol/min/pmol (or 983 pmol/min/mg) CYP3A4, respectively.

Pharmacological importance of stereochemical resolution of enantiomeric drugs

Drug enantiomers have identical properties in an achiral environment, but should be considered as different chemical compounds. This is because they often differ considerably in potency, pharmacological activity and pharmacokinetic profile, since the modules with which they interact in biological systems are also optically active. Within biological systems, the metabolism of one isomer may be via a different pathway or occur at a different rate from that of the other isomer. Preferential binding of one isomer to plasma proteins may cause differences in circulating free drug and hence alter concentrations at active sites. Interactions of both isomers may differ at the active sites through which pharmacological action is mediated. Actions and levels of activity of the stereoisomers in vivo may also differ. All the pharmacological activity may reside in a single enantiomer, whereas several possibilities exist for the other enantiomer-- it may be inactive, have a qualitatively different effect, an antagonistic effect or produce greater toxicity. Two isomers may have nearly identical qualitative pharmacological activity, qualitatively similar pharmacological activity but quantitatively different potency, or qualitatively different pharmacological activity. To avoid adverse effects and optimise the therapeutic value of enantiomeric drugs, it is necessary that methods for the resolution of racemates be evolved and devolved to determine isomeric purity, establish the effectiveness of isomers of the drug, and detect the presence of an enantiomer with lower therapeutic activity and undesirable adverse effects. Even if a drug is given as a pure enantiomer, methods to discriminate between enantiomers are required because racemisation can occur both in vitro and in vivo. Methods developed for resolution of drug enantiomers should facilitate routine testing of single isomers and their metabolites, studies of pharmacological, toxicological and clinical effectiveness, routine analysis of racemates, pure enantiomers or intermediates in manufacturing processes, and investigation of the potential for inversion of an enantiopure drug substance during the early stages of drug development and therapeutic drug monitoring.

Inhibitory effect of calcium channel blockers on human mesangial cell growth: evidence for actions independent of L-type Ca2+ channels

Calcium channel blockers (CCB) are known to affect the outcome of glomerulosclerosis in vivo and to suppress mesangial cell proliferation and cytokine production in vitro. It is uncertain, however, whether (i) human adult mesangial cells (HMC) express L-type Ca2+ channels and (ii) whether the effect of CCB on HMC is mediated by inhibition of L-type Ca2+ channels. In single cell preparations of HMC, the L-type Ca2+ channel agonist Bay K 8644 and K+-depolarization of the cell membrane caused a transient increase of cytosolic free Ca2+ ([Ca2+]i) in 60 to 80% of the cells. The CCB verapamil and nifedipine partially inhibited the effect of Bay K 8644 and K+-depolarization on [Ca2+]i. Binding experiments confirmed these functional studies by showing specific binding at the phenylalkylamine binding site of L-Type Ca2+ channels. Quiescent HMC were stimulated with fetal calf serum (FCS) or growth factors (platelet derived growth factor A/B, epidermal growth factor, angiotensin II, endothelin 1) in the presence of various concentrations (10(-10) to 10(-5) M) of different CCB: either (R)-verapamil, (S)-verapamil or the raceme of verapamil, and nifedipine or diltiazem, respectively. In addition, the enantiomers of devapamil were studied, because their action on the L-type Ca2+ channel is more stereoselective than that of the enantiomers of verapamil. At high concentrations (10(-6) to 10(-5) M) (R,S)-verapamil decreased cell numbers in cultures of quiescent HMC, increased LDH in the supernatant, and caused loss of trypan blue exclusion (cytotoxicity). At lower concentrations (R,S)-verapamil showed no cytotoxicity, but had two effects: (1.) concentration dependent (down to 10(-8) M) inhibition of indices of cell proliferation, that is, (i) stimulated (FCS or growth factor) 3H-thymidine incorporation and (ii) increment in cell number; and (2.) inhibition of indices of cell or matrix protein synthesis, that is, (i) stimulated 3H-methionine incorporation and (ii) 3H-proline incorporation. At equimolar concentrations the dihydropyridine nifedipine was equipotent with verapamil, whereas the benzothiazepine diltiazem was conspicuously less effective. Even at the lowest effective concentration (10(-8) M) comparison of (R)- and (S)-verapamil showed no significant difference between the enantiomer with weak or with strong effect on L-type Ca2+ channels, and this was true even when the more stereoselective enantiomers of devapamil were tested. These observations argue against the notion that effects of CCB result from specific interaction with L-type Ca2+ channels. The data are more consistent with the idea that interactions with targets other than L-type Ca2+ channels are involved.