Gain of Function (GOF) Mutant p53 in Cancer-Current Therapeutic Approaches.

Continuous development of personalized treatments is undoubtedly beneficial for oncogenic patients' comfort and survival rate. Mutant TP53 is associated with a worse prognosis due to the occurrence of metastases, increased chemoresistance, and tumor growth. Currently, numerous compounds capable of p53 reactivation or the destabilization of mutant p53 are being investigated. Several of them, APR-246, COTI-2, SAHA, and PEITC, were approved for clinical trials. This review focuses on these novel therapeutic opportunities, their mechanisms of action, and their significance for potential medical application.

Ruxolitinib-induced defects in DNA repair cause sensitivity to PARP inhibitors in myeloproliferative neoplasms.

Myeloproliferative neoplasms (MPNs) often carry JAK2(V617F), MPL(W515L), or CALR(del52) mutations. Current treatment options for MPNs include cytoreduction by hydroxyurea and JAK1/2 inhibition by ruxolitinib, both of which are not curative. We show here that cell lines expressing JAK2(V617F), MPL(W515L), or CALR(del52) accumulated reactive oxygen species-induced DNA double-strand breaks (DSBs) and were modestly sensitive to poly-ADP-ribose polymerase (PARP) inhibitors olaparib and BMN673. At the same time, primary MPN cell samples from individual patients displayed a high degree of variability in sensitivity to these drugs. Ruxolitinib inhibited 2 major DSB repair mechanisms, BRCA-mediated homologous recombination and DNA-dependent protein kinase-mediated nonhomologous end-joining, and, when combined with olaparib, caused abundant accumulation of toxic DSBs resulting in enhanced elimination of MPN primary cells, including the disease-initiating cells from the majority of patients. Moreover, the combination of BMN673, ruxolitinib, and hydroxyurea was highly effective in vivo against JAK2(V617F)+ murine MPN-like disease and also against JAK2(V617F)+, CALR(del52)+, and MPL(W515L)+ primary MPN xenografts. In conclusion, we postulate that ruxolitinib-induced deficiencies in DSB repair pathways sensitized MPN cells to synthetic lethality triggered by PARP inhibitors.

Genomic instability may originate from imatinib-refractory chronic myeloid leukemia stem cells.

Genomic instability is a hallmark of chronic myeloid leukemia in chronic phase (CML-CP) resulting in BCR-ABL1 mutations encoding resistance to tyrosine kinase inhibitors (TKIs) and/or additional chromosomal aberrations leading to disease relapse and/or malignant progression. TKI-naive and TKI-treated leukemia stem cells (LSCs) and leukemia progenitor cells (LPCs) accumulate high levels of reactive oxygen species (ROS) and oxidative DNA damage. To determine the role of TKI-refractory LSCs in genomic instability, we used a murine model of CML-CP where ROS-induced oxidative DNA damage was elevated in LSCs, including quiescent LSCs, but not in LPCs. ROS-induced oxidative DNA damage in LSCs caused clinically relevant genomic instability in CML-CP-like mice, such as TKI-resistant BCR-ABL1 mutations (E255K, T315I, H396P), deletions in Ikzf1 and Trp53, and additions in Zfp423 and Idh1. Despite inhibition of BCR-ABL1 kinase, imatinib did not downregulate ROS and oxidative DNA damage in TKI-refractory LSCs to the levels detected in normal cells, and CML-CP-like mice treated with imatinib continued to accumulate clinically relevant genetic aberrations. Inhibition of class I p21-activated protein kinases by IPA3 downregulated ROS in TKI-naive and TKI-treated LSCs. Altogether, we postulate that genomic instability may originate in the most primitive TKI-refractory LSCs in TKI-naive and TKI-treated patients.

Rac2-MRC-cIII-generated ROS cause genomic instability in chronic myeloid leukemia stem cells and primitive progenitors.

Chronic myeloid leukemia in chronic phase (CML-CP) is induced by BCR-ABL1 oncogenic tyrosine kinase. Tyrosine kinase inhibitors eliminate the bulk of CML-CP cells, but fail to eradicate leukemia stem cells (LSCs) and leukemia progenitor cells (LPCs) displaying innate and acquired resistance, respectively. These cells may accumulate genomic instability, leading to disease relapse and/or malignant progression to a fatal blast phase. In the present study, we show that Rac2 GTPase alters mitochondrial membrane potential and electron flow through the mitochondrial respiratory chain complex III (MRC-cIII), thereby generating high levels of reactive oxygen species (ROS) in CML-CP LSCs and primitive LPCs. MRC-cIII-generated ROS promote oxidative DNA damage to trigger genomic instability, resulting in an accumulation of chromosomal aberrations and tyrosine kinase inhibitor-resistant BCR-ABL1 mutants. JAK2(V617F) and FLT3(ITD)-positive polycythemia vera cells and acute myeloid leukemia cells also produce ROS via MRC-cIII. In the present study, inhibition of Rac2 by genetic deletion or a small-molecule inhibitor and down-regulation of mitochondrial ROS by disruption of MRC-cIII, expression of mitochondria-targeted catalase, or addition of ROS-scavenging mitochondria-targeted peptide aptamer reduced genomic instability. We postulate that the Rac2-MRC-cIII pathway triggers ROS-mediated genomic instability in LSCs and primitive LPCs, which could be targeted to prevent the relapse and malignant progression of CML.

Content of Health-Promoting Fatty Acids in Commercial Sheep, Cow and Goat Cheeses.

The study aimed to examine samples of different market original sheep cow and goat cheeses, in respect of the content and profile of FA with special emphasis on health-promoting FA. The content of fatty acids in the examined cheeses was highly differentiated and depended on the sort and type of cheese. The content of fatty acid groups in milk fat varied within the limits: SFA, 55.2-67.2%; SCSFA, 10.9-23.4%; BCFA, 1.6-2.9%; MUFA, 15.2-23.4%; PUFA, 1.9-4.3%; trans-MUFA, 1.8-6.0%; and CLA, 1.0-3.1%. From among the examined cheeses, the seasonal sheep cheeses (Oscypek) and mountain cow cheeses were characterized by the highest content of health-promoting fatty acids. The content of health-promoting fatty acids in the fat fraction of these cheeses was CLA 2.1-3.1%, trans-MUFA 3.5-6%, BCFA 2.7-2.9%, and SCSFA 12-18%.

Ester derivatives of salinomycin efficiently eliminate breast cancer cells via ER-stress-induced apoptosis.

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.

HDAC inhibitors, MS275 and SBHA, enhances cytotoxicity induced by oxaliplatin in the colorectal cancer cell lines.

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.

Decytabine enhances cytotoxicity induced by oxaliplatin and 5-fluorouracil in the colorectal cancer cell line Colo-205.

BACKGROUND: 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. RESULTS: 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. CONCLUSION: 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.

Inhibitory effects of 5-fluorouracil and oxaliplatin on human colorectal cancer cell survival are synergistically enhanced by sulindac sulfide.

BACKGROUND: COX inhibitors appear to be promising agents in combination with cytostatics in the treatment of colorectal carcinoma (CRC). The aim of this study was to compare growth inhibitory effects of cytostatics (5-fluorouracil, 5-FU; oxaliplatin) and COX inhibitor sulindac sulfide (an active metabolite of sulindac), given alone or in combination, on several CRC cell lines. MATERIALS AND METHODS: A series of human CRC cell lines were incubated with various combinations of the test drugs used in concentrations from 3 to 200 microM. The cell survival was assessed by MTT assay. Isobolograms and median effect method of Chou and Talalay were used to assess the nature and quantitative aspects of interaction observed between studied drugs. Cell cycle progression and apoptosis were measured using flow cytometric methods. In addition, growth inhibitory effects of studied agents on CRC cell lines were compared with a normal (mouse fibroblast) cell line. RESULTS: Sulindac sulfide synergistically potentiated the inhibitory effects of 5-FU and oxaliplatin on CRC survival, parallel to the induction of apoptosis. A dose reduction effect for synergistic activity of sulindac sulfide with studied cytostatics (in the range of 5- to 14-fold, when compared to single agent) suggested that the inhibitory effect of cytostatics on CRC survival may be obtained at low doses. In addition, sulindac sulfide appeared to be more specific against CRC cells than normal cells. CONCLUSION: It was apparent that combination of 5-FU or oxaliplatin with sulindac sulfide results in a powerful inhibition of growth of colorectal carcinoma cells in vitro, which may be more specific for cancer than normal cells.

Chronic myelogenous leukemia, a still unsolved problem: pitfalls and new therapeutic possibilities.

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 BCR-ABL 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.

Simultaneous Inhibition of BCR-ABL1 Tyrosine Kinase and PAK1/2 Serine/Threonine Kinase Exerts Synergistic Effect against Chronic Myeloid Leukemia Cells.

Tyrosine kinase inhibitors (TKIs) revolutionized the treatment of chronic myeloid leukemia in the chronic phase (CML-CP). However, it is unlikely that they can completely "cure" the disease. This might be because some subpopulations of CML-CP cells such as stem and progenitor cells are resistant to chemotherapy, even to the new generation of TKIs. Therefore, it is important to look for new methods of treatment to improve therapeutic outcomes. Previously, we have shown 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. In this study, we aimed to determine if simultaneous inhibition of BCR-ABL1 oncogenic tyrosine kinase and PAK1/2 serine/threonine kinase exert better anti-CML effect than that of individual treatments. PAK1 was inhibited by small-molecule inhibitor IPA-3 (p21-activated kinase inhibitor III), PAK2 was downregulated by specific short hairpin RNA (shRNA), and BCR-ABL1 tyrosine kinase was inhibited by imatinib (IM). The studies were conducted by using (i) primary CML-CP stem/early progenitor cells and normal hematopoietic counterparts isolated from the bone marrow of newly diagnosed patients with CML-CP and from healthy donors, respectively, (ii) CML-blast phase cell lines (K562 and KCL-22), and (iii) from BCR-ABL1-transformed 32Dcl3 cell line. Herein, we show that inhibition of the activity of PAK1 and/or PAK2 enhanced the effect of IM against CML cells without affecting the normal cells. We observed that the combined use of IM with IPA-3 increased the inhibition of growth and apoptosis of leukemia cells. To evaluate the type of interaction between the two drugs, we performed median effect analysis. According to our results, the type and strength of drug interaction depend on the concentration of the drugs tested. Generally, combination of IM with IPA-3 at the 50% of the cell kill level (EC50) generated synergistic effect. Based on our results, we hypothesize that IM, a BCR-ABL1 tyrosine kinase inhibitor, combined with a PAK1/2 inhibitor facilitates eradication of CML-CP cells.

Biological characterization of the modified poly(dimethylsiloxane) surfaces based on cell attachment and toxicity assays.

Poly(dimethylsiloxane) (PDMS) is a material applicable for tissue and biomedical engineering, especially based on microfluidic devices. PDMS is a material used in studies aimed at understanding cell behavior and analyzing the cell adhesion mechanism. In this work, biological characterization of the modified PDMS surfaces based on cell attachment and toxicity assays was performed. We studied Balb 3T3/c, HMEC-1, and HT-29 cell adhesion on poly(dimethylsiloxane) surfaces modified by different proteins, with and without pre-activation with plasma oxygen and UV irradiation. Additionally, we studied how changing of a base and a curing agent ratios influence cell proliferation. We observed that cell type has a high impact on cell adhesion, proliferation, as well as viability after drug exposure. It was tested that the carcinoma cells do not require a highly specific microenvironment for their proliferation. Cytotoxicity assays with celecoxib and oxaliplatin on the modified PDMS surfaces showed that normal cells, cultured on the modified PDMS, are more sensitive to drugs than cancer cells. Cell adhesion was also tested in the microfluidic systems made of the modified PDMS layers. Thanks to that, we studied how the surface area to volume ratio influences cell behavior. The results presented in this manuscript could be helpful for creation of proper culture conditions during in vitro tests as well as to understand cell response in different states of disease depending on drug exposure.

DNA methyltransferase inhibitors improve the effect of chemotherapeutic agents in SW48 and HT-29 colorectal cancer cells.

DNA methylation is an epigenetic phenomenon known to play an important role in the development and progression of human cancer. Enzyme responsible for this process is DNA methyltransferase 1 (DNMT1) that maintains an altered methylation pattern by copying it from parent to daughter DNA strands after replication. Aberrant methylation of the promoter regions of genes critical for normal cellular functions is potentially reversible. Therefore, inactivation of DNMT1 seems to be a valuable target for the development of cancer therapies. Currently, the most popular DNMT inhibitors (DNMTi) are cytidine analogues like 5-azacytidine, 5-aza-2'-deoxycytidine (decitabine) and pyrimidin-2-one ribonucleoside (zebularine). In colorectal cancer, epigenetic modifications play an essential role at each step of carcinogenesis. Therefore, we have addressed the hypothesis that DNA methyltransferase inhibitors may potentiate inhibitory effects of classical chemotherapeutic agents, such as oxaliplatin and 5-fluorouracil (5-FU), commonly used in colorectal cancer therapy. Here, our report shows that DNMTi can have positive interactions with standard chemotherapeutics in colorectal cancer treatment. Using pharmacological models for the drug-drug interaction analysis, we have revealed that the combination of decitabine with 5-FU or oxaliplatin shows the most attractive interaction (synergism), whereas the effect of zebularine in combinations with chemotherapeutics is moderate and may be depended on genetic/epigenetic background of a cell line or secondary drug used in combination. Our results suggest that DNMTi administered in combination with standard chemotherapeutics might improve the treatment of patients with colorectal cancers.

DNA methyltransferase inhibitors and their emerging role in epigenetic therapy of cancer.

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-(ß-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.

A microfluidic system to study the cytotoxic effect of drugs: the combined effect of celecoxib and 5-fluorouracil on normal and cancer cells.

We have investigated the response of normal and cancer cells to exposure a combination of celecoxib (Celbx) and 5-fluorouracil (5-FU) using a lab-on-a-chip microfluidic device. Specifically, we have tested the cytotoxic effect of Celbx on normal mouse embryo cells (Balb/c 3T3) and human lung carcinoma cells (A549). The single drugs or their combinations were adjusted to five different concentrations using a concentration gradient generator (CGG) in a single step. The results suggest that Celbx can enhanced the anticancer activity of 5-FU by stronger inhibition of cancer cell growth. We also show that the A549 cancer cells are more sensitive to Celbx than the Balb/c 3T3 normal cells. The results obtained with the microfluidic system were compared to those obtained with a macroscale in vitro cell culture method. In our opinion, the microfluidic system represents a unique approach for an evaluation of cellular response to multidrug exposure that also is more simple than respective microwell plate assays. Figureᅟ

Evaluation of inhibition of cancer cell proliferation in vitro with different berries and correlation with their antioxidant levels by advanced analytical methods.

Dimethylsulfoxide extracts of Chilean berries [Myrteola nummularia, 'Murtilla-like'] vs. well known 'Murtilla', Chilean and Polish blueberries, and Chilean raspberries were investigated for their antioxidant, quenching and antiproliferative activities. The significantly highest levels of polyphenols, flavonoids, flavanols and their antioxidant activities were estimated in 'Murtilla' (MT) berries (P<0.05), than in other investigated samples. DPPH kinetic measurements were calculated to compare, distinguish and discriminate the antiradical activity among berry extracts by multivariate analysis. The lowest IC(50) values, 751 and 858 µg/ml, were obtained for MT extract on colon cancer cell lines HT-29 and SW48. HT-29 cells treated with MT extract showed a decrease in G1 phase cells from 77% to 56% (P<0.05). At the highest concentration of 2000 µg/ml MT extract caused 90-100% cell growth inhibition. Percentage of death cells treated with MT extract was 80.1% and 72.5% for SW48 and HT-29 cells, respectively. The inhibition of cancer cell proliferation highly correlated with the levels of polyphenols, flavonoids and their antioxidant activities. The interaction between drugs and serum albumin plays an important role in the distribution and metabolism of drugs, therefore the complexation reaction between flavonoids, and berries extracts, and bovine serum albumin (BSA) was investigated by 3-D fluorescence and FTIR spectroscopy. The results indicated that flavonoids and polyphenol extracts have strong ability to quench the intrinsic fluorescence of BSA by forming complexes. A shift in the maximum of amides FTIR-bands appeared. In conclusion, these findings suggest that the intake of a new kind of berry, as a source of natural antioxidants, may reduce colon cancer risk.

MS275 enhances cytotoxicity induced by 5-fluorouracil in the colorectal cancer cells.

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.