Sodium-glucose cotransporter 2 inhibitor dapagliflozin prevents ejection fraction reduction, reduces myocardial and renal NF-κB expression and systemic pro-inflammatory biomarkers in models of short-term doxorubicin cardiotoxicity.

Background: Anthracycline-mediated adverse cardiovascular events are among the leading causes of morbidity and mortality in patients with cancer. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) exert multiple cardiometabolic benefits in patients with/without type 2 diabetes, chronic kidney disease, and heart failure with reduced and preserved ejection fraction. We hypothesized that the SGLT2i dapagliflozin administered before and during doxorubicin (DOXO) therapy could prevent cardiac dysfunction and reduce pro-inflammatory pathways in preclinical models. Methods: Cardiomyocytes were exposed to DOXO alone or combined with dapagliflozin (DAPA) at 10 and 100 nM for 24 h; cell viability, iATP, and Ca++ were quantified; lipid peroxidation products (malondialdehyde and 4-hydroxy 2-hexenal), NLRP3, MyD88, and cytokines were also analyzed through selective colorimetric and enzyme-linked immunosorbent assay (ELISA) methods. Female C57Bl/6 mice were treated for 10 days with a saline solution or DOXO (2.17 mg/kg), DAPA (10 mg/kg), or DOXO combined with DAPA. Systemic levels of ferroptosis-related biomarkers, galectin-3, high-sensitivity C-reactive protein (hs-CRP), and pro-inflammatory chemokines (IL-1α, IL-1ß, IL-2, IL-4, IL-6, IL-10, IL-12, IL17-α, IL-18, IFN-γ, TNF-α, G-CSF, and GM-CSF) were quantified. After treatments, immunohistochemical staining of myocardial and renal p65/NF-kB was performed. Results: DAPA exerts cytoprotective, antioxidant, and anti-inflammatory properties in human cardiomyocytes exposed to DOXO by reducing iATP and iCa++ levels, lipid peroxidation, NLRP-3, and MyD88 expression. Pro-inflammatory intracellular cytokines were also reduced. In preclinical models, DAPA prevented the reduction of radial and longitudinal strain and ejection fraction after 10 days of treatment with DOXO. A reduced myocardial expression of NLRP-3 and MyD-88 was seen in the DOXO-DAPA group compared to DOXO mice. Systemic levels of IL-1ß, IL-6, TNF-α, G-CSF, and GM-CSF were significantly reduced after treatment with DAPA. Serum levels of galectine-3 and hs-CRP were strongly enhanced in the DOXO group; on the other hand, their expression was reduced in the DAPA-DOXO group. Troponin-T, B-type natriuretic peptide (BNP), and N-Terminal Pro-BNP (NT-pro-BNP) were strongly reduced in the DOXO-DAPA group, revealing cardioprotective properties of SGLT2i. Mice treated with DOXO and DAPA exhibited reduced myocardial and renal NF-kB expression. Conclusion: The overall picture of the study encourages the use of DAPA in the primary prevention of cardiomyopathies induced by anthracyclines in patients with cancer.

Panobinostat synergizes with zoledronic acid in prostate cancer and multiple myeloma models by increasing ROS and modulating mevalonate and p38-MAPK pathways.

Patients with advanced prostate cancer (PCa) and multiple myeloma (MM) have limited long-term responses to available therapies. The histone deacetylase inhibitor panobinostat has shown significant preclinical and clinical anticancer activity in both hematological and solid malignancies and is currently in phase III trials for relapsed MM. Bisphosphonates (BPs), such as zoledronic acid (ZOL), inhibit osteoclast-mediated bone resorption and are indicated for the treatment of bone metastasis. BPs, including ZOL, have also shown anticancer activity in several preclinical and clinical studies. In the present report, we found a potent synergistic antiproliferative effect of panobinostat/ZOL treatment in three PCa and three MM cell lines as well as in a PCa ZOL-resistant subline, independently of p53/KRAS status, androgen dependency, or the schedule of administration. The synergistic effect was also observed in an anchorage-independent agar assay in both ZOL-sensitive and ZOL-resistant cells and was confirmed in vivo in a PCa xenograft model. The co-administration of the antioxidant N-acetyl-L-cysteine blocked the increased reactive oxygen species generation and apoptosis observed in the combination setting compared with control or single-agent treatments, suggesting that oxidative injury plays a functional role in the synergism. Proapoptotic synergy was also partially antagonized by the addition of geranyl-geraniol, which bypasses the inhibition of farnesylpyrophosphate synthase by ZOL in the mevalonate pathway, supporting the involvement of this pathway in the synergy. Finally, at the molecular level, the inhibition of basal and ZOL-induced activation of p38-MAPK by panobinostat in sensitive and ZOL-resistant cells and in tumor xenografts could explain, at least in part, the observed synergism.

Acquired resistance to zoledronic acid and the parallel acquisition of an aggressive phenotype are mediated by p38-MAP kinase activation in prostate cancer cells.

The nitrogen-containing bisphosphonates (N-BP) zoledronic acid (ZOL) inhibits osteoclast-mediated bone resorption, and it is used to prevent skeletal complications from bone metastases. ZOL has also demonstrated anticancer activities in preclinical models and, recently, in cancer patients, highlighting the interest in determining eventual mechanisms of resistance against this agent. In our study, we selected and characterised a resistant subline of prostate cancer (PCa) cells to better understand the mechanisms, by which tumour cells can escape the antitumour effect of ZOL. DU145R80-resistant cells were selected in about 5 months using stepwise increasing concentrations of ZOL from DU145 parental cells. DU145R80 cells showed a resistance index value of 5.5 and cross-resistance to another N-BP, pamidronate, but not to the non-nitrogen containing BP clodronate. Notably, compared with DU145 parental cells, DU145R80 developed resistance to apoptosis and anoikis, as well as overexpressed the anti-apoptotic protein Bcl-2 and oncoprotein c-Myc. Moreover, DU145R80 cells underwent epithelial to mesenchymal transition (EMT) and showed increased expression of the metalloproteases MMP-2/9, as well as increased invading capability. Interestingly, compared with DU145, DU145R80 cells also increased the gene expression and protein secretion of VEGF and the cytokines Eotaxin-1 and IL-12. At the molecular level, DU145R80 cells showed strong activation of the p38-MAPK-dependent survival pathway compared with parental sensitive cells. Moreover, using the p38-inhibitor SB203580, we completely reversed the resistance to ZOL, as well as EMT marker expression and invasion. Furthermore, SB203580 treatment reduced the expression of VEGF, Eotaxin-1, IL-12, MMP-9, Bcl-2 and c-Myc. Thus, for the first time, we demonstrate that the p38-MAPK pathway can be activated under continuous extensive exposure to ZOL in PCa cells and that the p38-MAPK pathway has a critical role in the induction of resistance, as well as in the acquisition of a more aggressive and invasive phenotype.

Vorinostat synergises with capecitabine through upregulation of thymidine phosphorylase.

BACKGROUND: Potentiation of anticancer activity of capecitabine is required to improve its therapeutic index. In colorectal cancer (CRC) cells, we evaluated whether the histone deacetylase-inhibitor vorinostat may induce synergistic antitumour effects in combination with capecitabine by modulating the expression of thymidine phosphorylase (TP), a key enzyme in the conversion of capecitabine to 5-florouracil (5-FU), and thymidylate synthase (TS), the target of 5-FU. METHODS: Expression of TP and TS was measured by real-time PCR, western blotting and immunohistochemistry. Knockdown of TP was performed by specific small interfering RNA. Antitumour activity of vorinostat was assessed in vitro in combination with the capecitabine active metabolite deoxy-5-fluorouridine (5'-DFUR) according to the Chou and Talay method and by evaluating apoptosis as well as in xenografts-bearing nude mice in combination with capecitabine. RESULTS: Vorinostat induced both in vitro and in vivo upregulation of TP as well as downregulation of TS in cancer cells, but not in ex vivo treated peripheral blood lymphocytes. Combined treatment with vorinostat and 5'-DFUR resulted in a synergistic antiproliferative effect and increased apoptotic cell death in vitro. This latter effect was impaired in cells where TP was knocked. In vivo, vorinostat plus capecitabine potently inhibited tumour growth, increased apoptosis and prolonged survival compared with control or single-agent treatments. CONCLUSIONS: Overall, this study suggests that the combination of vorinostat and capecitabine is an innovative antitumour strategy and warrants further clinical evaluation for the treatment of CRC.

Multiple-target drugs: inhibitors of heat shock protein 90 and of histone deacetylase.

In spite of the improvement of conventional medical therapy for cancer treatment, the impact on cancer related mortality in the last ten years has been modest especially for advanced disease in adults. On the other hand, understanding of molecular events underlining tumor development lead to the definition of new molecular targets for novel anti-tumor therapeutical approaches. On this regard, several biotechnology products selected by academic as well as industrial research are currently in clinical trials. Epigenetics as well as post-translational modifications of proteins are emerging as novel attractive targets for anticancer therapy. In addition, the heterogeneity of tumor cells within a selected neoplastic lesions as well as the redundancy of proliferative and survival pathways present in cancer cells favor the development of single drugs that are able to affect multiple pathways. Inhibitors of heat shock protein 90 and of histone deacetylase are two novel classes of multi-target agents that entered recently in clinical studies. This review will focus on the most important issues in the development of both these classes of agents.

Acetylation of proteins as novel target for antitumor therapy: review article.

Imbalance in histone acetylation can lead to changes in chromatin structure and transcriptional dysregulation of genes that are involved in the control of proliferation, cell-cycle progression, differentiation and/or apoptosis. Histone acetyltransferases (HATs) and histone deacetylases (HDACs), are two classes of enzymes regulating histone acetylation and whose altered activity has been identified in several cancers. HATs and HDACs enzymes also target non histone protein substrates, including transcription factors, nuclear import factors, cytoskeleton and chaperon proteins. HDAC inhibitors are a novel class of anticancer agents which have been recently shown to induce growth arrest and apoptosis in a variety of human cancer cells by mechanism that cannot be solely attributed to the level of histone acetylation. Several clinical studies with HDAC inhibitors are ongoing, however the molecular basis for their tumour selectivity remains unknown and represent a challenge for the cancer research community.

Allosteric properties of inosine monophosphate dehydrogenase revealed through the thermodynamics of binding of inosine 5'-monophosphate and mycophenolic acid. Temperature dependent heat capacity of binding as a signature of ligand-coupled conformational equilibria.

The thermodynamic properties of binding of the substrate, inosine monophosphate (IMP), and the uncompetitive inhibitor, mycophenolic acid, to inosine monophosphate dehydrogenase (IMPDH) were measured. Specifically, the free energy, enthalpy, entropy, and heat capacity changes were determined for each ligation state of the tetrameric enzyme, over a temperature range from 2.5 to 37 degrees C by high-precision titration microcalorimetry. It was discovered that IMP binds to IMPDH in a negatively cooperative fashion and that mycophenolic acid binding is critically dependent on the presence of IMP. Moreover, the binding of IMP is entropically driven at low temperatures and enthalpically driven at high temperatures, with an unusually large, temperature dependent heat capacity change. A thermodynamic argument, based on the general nature of the heat capacity function for a binding reaction and its temperature dependence, is used to infer the existence of an equilibrium mixture of at least two structural forms of apo-IMPDH. The equilibrium is perturbed in the presence of IMP and mycophenolic acid, suggesting a mechanism for the ligand-linked conformational changes. An allosteric model, incorporating subunit-subunit interactions nested within a concerted conformational change involving the entire tetrameric macromolecule, is proposed to account for the observed binding behavior. The implications of these findings for the design of novel "allosteric-effector" inhibitors of IMPDH, to be used for the purpose of immunosuppression, are discussed.

Inhibition of IMPDH by mycophenolic acid: dissection of forward and reverse pathways using capillary electrophoresis.

The objective of this work was to contribute to the understanding of mechanisms for IMPDH inhibition. We over-expressed hamster type II IMPDH in Escherichia coli, purified the protein to apparent homogeneity, and used capillary electrophoresis to quantify enzyme turnover events accompanying inhibition by mycophenolic acid (MPA). We dissected two convergent pathways leading to MPA-inhibition; a rapid "forward" pathway beginning with substrates and linked to enzyme catalysis, and a slower "reverse" pathway apparently not involving catalysis. MPA-inhibition occurred rapidly in the forward direction by interrupting the enzyme turnover cycle, after IMP and NAD+ binding, after hydride transfer, and after NADH release. Slow inhibition, without substrate turnover, was achieved by incubating free enzyme with excess XMP and MPA. We propose that mycophenolic acid inhibits IMPDH by trapping a transient covalent product of the hydride transfer reaction (IMPDH approximately XMP*) before a final hydrolysis step that precedes XMP and enzyme release in the forward reaction pathway. Understanding the ligand occupancy of the protein has also proven important for producing homogeneous, chemically defined complexes for structural studies. IMPDH samples inhibited by MPA in the forward and reverse pathways yielded similar, high-quality crystals that are currently undergoing X-ray diffraction analyses.

Enthalpy of hydrogen bond formation in a protein-ligand binding reaction.

Parallel measurements of the thermodynamics (free-energy, enthalpy, entropy and heat-capacity changes) of ligand binding to FK506 binding protein (FKBP-12) in H2O and D2O have been performed in an effort to probe the energetic contributions of single protein-ligand hydrogen bonds formed in the binding reactions. Changing tyrosine-82 to phenylalanine in FKBP-12 abolishes protein-ligand hydrogen bond interactions in the FKBP-12 complexes with tacrolimus or rapamycin and leads to a large apparent enthalpic stabilization of binding in both H2O and D2O. High-resolution crystallographic analysis reveals that two water molecules bound to the tyrosine-82 hydroxyl group in unliganded FKBP-12 are displaced upon formation of the protein-ligand complexes. A thermodynamic analysis is presented that suggests that the removal of polar atoms from water contributes a highly unfavorable enthalpy change to the formation of C=O...HO hydrogen bonds as they occur in the processes of protein folding and ligand binding. Despite the less favorable enthalpy change, the entropic advantage of displacing two water molecules upon binding leads to a slightly more favorable free-energy change of binding in the reactions with wild-type FKBP-12.

Probing hydration contributions to the thermodynamics of ligand binding by proteins. Enthalpy and heat capacity changes of tacrolimus and rapamycin binding to FK506 binding protein in D2O and H2O.

The stabilities of native proteins and protein-ligand complexes result from differential interactions among numerous polar and nonpolar atoms within the proteins and ligands and of these atoms with water. Delineation of the various energetic contributions of the stabilities of proteins or protein-ligand complexes in aqueous solution, and an evaluation of their structural basis, requires a direct account of the changes, in the interactions of the protein with the solvent, that accompany the folding or binding reactions. Two largely nonpolar, structurally related macrolide ligands, tacrolimus (also known as FK506) and rapamycin, each bind with high affinity to a common site on a small FK506 binding protein (FKBP-12) and inhibit its peptidylprolyl cis-trans-isomerase activity. In an effort to elucidate the influence of water on the thermodynamics of their binding reactions, we have measured the enthalpies of tacrolimus and rapamycin binding to FKBP-12, in buffered solutions of H2O (at pH 7.0) or D2O (at pD 7.0), by high-precision titration calorimetry in the temperature range 5-30 degrees C. For both tacrolimus and rapamycin binding, a large enthalpic destabilization of binding is observed in D2O relative to H2O, in the temperature range examined. Additionally, large negative constant pressure heat capacity changes are observed for the binding of the ligands in both H2O and D2O. A thermodynamic analysis is presented to identify the structural determinants of the differences in the energetics of binding in light and heavy water. The analysis suggests that a chief contributor to the observed enthalpic destabilization is the differential hydration, of protein and ligand atoms, by light and heavy water.

Resonance Raman spectroscopy of chemically modified hemoglobins.

Hemoglobin obtained from out-dated human blood was stripped of 2,3-diphosphoglycerate and modified with the crosslinking agents glyoxalic acid, 1,2-cyclohexadione, or fumarate to stabilize the tetramer. The resulting hemoglobins, which show alterations in their oxygen transport capability, have been studied in their oxy, deoxy and fluoro-met forms using resonance Raman spectroscopy with Soret excitation. The resonance Raman spectra of oxy-hemoglobins cross linked with glyoxalic acid and 1,2-cyclohexadione show that these cross linking agents force the heme into a high spin structure. The resonance Raman spectra of the fluoro-met hemoglobins, however, indicate that the same cross linking agents force the heme into a lower spin structure. Absorption spectroscopy and molecular orbital considerations suggest that protein constraints at the sixth ligand of the heme can account for the change in spin state in the glyoxalic acid and 1,2-cyclohexadione cross linked hemoglobins.