Histone deacetylases (HDACs) activity determines the acetylation status of histons, and has the ability to regulate gene expression through chromatin remodelling. HDACs are a promising target for ...pharmacological inhibition, since it has been discovered that some genes are repressed by their inappropriate recruitment. To test this we have addressed the hypothesis that histone deacetylase inhibitors SBHA and MS275 potentiate inhibitory effects of classical anti-colorectal cancer cytostatic, 5-fluorouracil (5-FU), on survival of colorectal cancer (CRC) cells
in vitro. We are reporting here that HDAC inhibitors show potent synergistic interaction with 5-FU. The observed synergism between HDAC inhibitors and 5-FU is most probably related to the augmented apoptotic signal allowed for significant (both biological and statistical) reduction of the cytotoxic doses.
Histone deacetylases (HDACs) play an important role in the epigenetic regulation of gene expression by catalyzing the removal of acetyl groups, stimulating chromatin condensation, and promoting ...transcriptional repression. Since aberrant epigenetic changes are a hallmark of cancer, HDACs appear a promising target for pharmacological inhibition. To test this we have addressed the hypothesis that histone deacetylase inhibitors (HDACi), MS275 and SBHA, potentiate inhibitory effects of classical anti-colorectal cancer cytostatic, oxaliplatin, on survival of colorectal cancer (CRC) cells
in vitro. We are reporting here that HDACi shows potent synergistic interaction with oxaliplatin. The observed synergism between HDACi and oxaliplatin is most probably related to the augmented apoptotic signal and allowed for significant reduction of doses of anticancer agents used.
The DNA methyltransferase (DNMT) inhibitors azacytidine and decitabine are the most successful epigenetic drugs to date and are still the most widely used as epigenetic modulators, even though their ...application for oncological diseases is restricted by their relative toxicity and poor chemical stability. Zebularine (1-(β-D-ribofuranosyl)-1,2-dihydropyrimidin-2-one), a more stable and less toxic cytidine analog, is another inhibitor of DNMT with concomitant inhibitory activity towards cytidine deaminase. Unfortunately, there is no new information related to the possible clinical applications of zebularine. Although many new inhibitors of DNMT have been identified, none of them can so far replace azacytidine, decitabine and, to a lesser degree, zebularine. This review summarizes the current data and knowledge about azacytidine, decitabine and zebularine, and their role in present and possible future epigenetic cancer therapy. We also discuss the molecular modes of action of these agents with consideration of their different toxicities and demethylation profiles, reflecting their complex and partially overlapping biological effects.
Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder of hematopoietic stem cells. At the molecular level, the disorder results from t(9;22)(q34;q11) reciprocal translocation between ...chromosomes, which leads to the formation of an oncogenic
gene fusion. Instead of progress in the understanding of the molecular etiology of CML and the development of novel therapeutic strategies, clinicians still face many challenges in the effective treatment of patients. In this review, we discuss the pathways of diagnosis and treatment of patients, as well as the problems appearing in the course of disease development. We also briefly refer to several aspects regarding the current knowledge on the molecular basis of CML and new potential therapeutic targets.
DNA methylation is an epigenetic phenomenon known to play an important role in the development of cancers, including colorectal cancer (CRC). Aberrant methylation of promoter regions of genes is ...potentially reversible, and if methylation is important for cancer survival, demethylation should do the opposite. To test this we have addressed the hypothesis that DNA methyltransferase inhibitors (DNMTi), decytabine and zebularine, potentiate inhibitory effects of classical anti-CRC cytostatics, oxaliplatin and 5-fluorouracil (5-FU), on survival of CRC cells in vitro.
Isobole and median effect analysis revealed that decytabine shows potent synergistic interaction with oxaliplatin and 5-FU and that this is probably not the class effect of DNMTi as zebularine shows strong antagonistic interaction with oxaliplatin. The synergistic combination treatment was also applied to the cultures to investigate their mechanisms of action. We have shown that combinations of decytabine with cytostatics produced dose-dependent growth inhibition and treatment-induced apoptosis.
The observed synergism between decytabine and cytostatics is most probably related to the augmented apoptotic signal and allowed for significant (both biologically and statistically) reduction of the cytotoxic doses of cytostatics used.
Tyrosine kinase inhibitors (TKIs) revolutionized the treatment of BCR-ABL1 tyrosine kinase - positive chronic myeloid leukemia in chronic phase (CML-CP). However, it is unlikely that TKIs will “cure” ...the disease in majority of patients because CML-CP cells are elusive targets even for the most advanced therapies employing second and third generation of TKIs. Therefore, new treatment modalities are necessary to improve therapeutic outcomes.
We showed before that class I p21-activated serine/threonine kinases (PAKs) remained active in TKI-naive and TKI-treated CML-CP leukemia stem and early progenitor cells. The aim of the study was to test whether simultaneous inhibition of signaling pathways activated by BCR-ABL1 and PAK kinases may improve the treatment of CML. Special attention was focused on PAK1 and PAK2, which are expressed in hematopoietic cells and can play an important role in the promotion of CML cells proliferation and survival. PAK kinases were targeted by small molecule inhibitor IPA-3 (inhibitor of PAK1) and shRNA construct for PAK2, BCR-ABL1 kinase was inhibited by imatinib. The studies were carried out using (i) primary CML-CP stem/early progenitor cells and normal hematopoietic counterparts isolated from the bone marrow of newly diagnosed CML-CP patients and healthy donors, respectively, (ii) CML-blast phase cell lines (K562 and KCL-22), and (iii) BCR-ABL1-transformed 32Dcl3 cell line cells.
We show here that inhibition of PAK1 or/and PAK2 kinases activity enhanced the effect of IM against CML cells without affecting normal counterparts. We observed that the combined use of IM with IPA-3 increased growth inhibition and apoptosis of leukemia cells. To evaluate the type of drugs interaction median effect analysis method was used. The studies revealed that the type and strength of drug interaction depend on drug concentration. Generally, combination of IM with IPA-3 at the 50% of the cell kill level (EC50) generated synergistic effect. Altogether, we postulate that BCR-ABL1 kinase inhibitor should be combined with PAK1/2 inhibitor to facilitate eradication of CML cells.
No relevant conflicts of interest to declare.
The polyether ionophore salinomycin (SAL) has been found to selectively target breast cancer cells, including those with stem-like phenotype. On the other hand, SAL amides and esters obtained through ...derivatisation of the C1 carboxyl of the ionophore were found to exhibit anticancer properties, whilst reducing potential toxicity issues which often occur during standard chemotherapy. However, the studies on the activity and especially on the mechanisms of action of this class of semi-synthetic products against breast cancer cells are very limited. Therefore, in this work, we confirmed the anti-breast cancer activity of SAL, and further investigated the potential of its selected C1 amide and ester analogs to destroy breast cancer cells, including the highly aggressive triple-negative MDA-MB-231 cells. Importantly, SAL esters were found to be more potent than the native structure and their amide counterparts. Our data revealed that SAL ester derivatives, particularly compounds 5 and 7 (2,2,2-trifluoroethyl and benzotriazole ester of SAL, respectively), increase the level of p-eIF2α (Ser51) and IRE1α proteins. Additionally, an increased level of DNA damage indicators such as γH2AX protein and modified guanine (8-oxoG) was observed. These findings suggest that the apoptosis of MCF-7 and MDA-MB-231 cells induced by the most promising esters derived from SAL may result from the interaction between ER stress and DNA damage response mechanisms.
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•Salinomycin and its ester and amide derivatives have been studied for anti-cancer activity.•ER stress-induced apoptosis is the mechanism of action against MCF-7 and MDA-MB-231 cancer cells.•When they are administered to the non-neoplastic normal breast fibroblasts displayed less toxicity.•Salinomycin and its ester derivatives 5–7 increase the level of p-eIF2α (Ser51) and IRE1α proteins.
BCR-ABL1 fusion tyrosine kinase transforms hematopoietic stem cells (HSCs) and cause chronic myeloid leukemia in chronic phase (CML-CP), which is a stem cell (leukemia stem cell=LSC) -derived but a ...progenitor (leukemia progenitor cell=LPC)-driven disease. Tyrosine kinase inhibitors (TKIs) such as imatinib, dasatinib, nilotinib and ponatinib revolutionized the treatment of CML.
We showed that reactive oxygen species (ROS) may increase the levels oxidative DNA damage in TKI-naïve and TKI-treated Lin-CD34+CD38- LSCs, including quiescent LSCs, and in Lin-CD34+CD38+ LPCs. Since DNA repair mechanisms display reduced fidelity/activity in CML cells, overproduction of ROS may promote genomic instability (accumulation of point mutations and chromosomal aberrations) resulting in resistance to TKIs and malignant progression of the disease to accelerated (CML-AP) or blast (CML-BP) phase.
BCR-ABL1 kinase stimulates numerous signaling pathways to induce and maintain transformation of hematopoietic cells. We and others found that phosphatidylinositol-3 kinase (PI3k) plays an essential role not only in growth factor independent proliferation and protection from apoptosis of CML cells, but also in overproduction of mitochondrial ROS. Here we investigated the role of PI3k downstream effectors, AKT serine/threonine kinase and Rac GTPase in genomic instability in TKI-naïve and TKI-treated LSCs and LPCs.
Using CML-CP primary cells and an inducible model of murine CML-CP –like disease we determined that Rac2 – PAK serine/threonine pathway alters mitochondrial membrane potential and electron flow through the mitochondrial respiratory chain complex III thereby generating high levels of ROS in TKI-naïve and TKI-treated LSCs and LPCs. In addition, AKT appeared to play an essential role in generation of ROS-induced oxidative DNA damage in TKI-naïve and TKI-treated LPCs, but not in LSCs. Inhibition of AKT did not affect the activity of Rac2 and inhibition of Rac2 did not affect AKT, clearly indicating that their activation status does not depend on each other. Targeting Rac2 and AKT either by mutations/deletions/shRNAs or small molecule inhibitors/peptides reduced genomic instability resulting in diminished frequency of TKI-resistant BCR-ABL1 kinase mutations and chromosomal aberrations.
Altogether TKI-naive and TKI-treated LSCs (including quiescent LSCs) display only PI3k-Rac2-PAK pathway, whereas LPCs contain PI3k-Rac2-PAK and PI3k-AKT pathways responsibble for ROS-induced oxidative DNA damage and genomic instability. Our findings may have more broad application because other oncogenic tyrosine kinases expressed in hetatopoietic malignancies induce similar mechanisms of genomic instability.
No relevant conflicts of interest to declare.
Tyrosine kinase inhibitors (TKIs) revolutionized the treatment of chronic myeloid leukemia in chronic phase (CML-CP). Unfortunately, 25% of TKI-naive patients and 50-90% of patients developing ...TKI-resistance carry CML clones expressing TKI-resistant BCR-ABL1 kinase mutants. We reported that CML-CP leukemia stem and progenitor cell populations accumulate high amounts of reactive oxygen species, which may result in accumulation of uracil derivatives in genomic DNA. Unfaithful and/or inefficient repair of these lesions generates TKI-resistant point mutations in BCR-ABL1 kinase. Using an array of specific substrates and inhibitors/blocking antibodies we found that uracil DNA glycosylase UNG2 were inhibited in BCR-ABL1-transformed cell lines and CD34(+) CML cells. The inhibitory effect was not accompanied by downregulation of nuclear expression and/or chromatin association of UNG2. The effect was BCR-ABL1 kinase-specific because several other fusion tyrosine kinases did not reduce UNG2 activity. Using UNG2-specific inhibitor UGI, we found that reduction of UNG2 activity increased the number of uracil derivatives in genomic DNA detected by modified comet assay and facilitated accumulation of ouabain-resistant point mutations in reporter gene Na(+)/K(+)ATPase. In conclusion, we postulate that BCR-ABL1 kinase-mediated inhibition of UNG2 contributes to accumulation of point mutations responsible for TKI resistance causing the disease relapse, and perhaps also other point mutations facilitating malignant progression of CML.
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