Luminescent Biological Probes Derived from Ruthenium(II) Estradiol Polypyridine Complexes

New quinoxaline-based VEGFR-2 inhibitors: design, synthesis, and antiproliferative evaluation with in silico docking, ADMET, toxicity, and DFT studies

A new series of 3-methylquinoxaline-based derivatives having the same essential pharmacophoric features as VEGFR-2 inhibitors have been synthesized and evaluated for their antiproliferative activities against two human cancer cell lines, MCF-7 and HepG-2. Compounds 15b and 17b demonstrated a significant antiproliferative effect with IC₅₀ ranging from 2.3 to 5.8 μM. An enzymatic assay was carried out for all the tested candidates against VEGFR-2. Compound 17b was the most potent VEGFR-2 inhibitor (IC₅₀ = 2.7 nM). Mechanistic investigation including cell cycle arrest and apoptosis was performed for compound 17b against HepG-2 cells, and the results revealed that 17b induced cell apoptosis and arrested cell cycle in the G2/M phase. Moreover, apoptosis analyses were conducted for compound 17b to evaluate its apoptotic potential. The results showed upregulation in caspase-3 and caspase-9 levels, and improving the Bax/Bcl-2 ratio by more than 10-fold. Docking studies were performed to determine the possible interaction with the VEGFR-2 active site. Further docking studies were carried out for compound 17b against cytochrome P450 to present such compounds as non-inhibitors. In silico ADMET, toxicity, and physico-chemical properties revealed that most of the synthesized members have acceptable values of drug-likeness. Finally, DFT studies were carried out to calculate the thermodynamic, molecular orbital and electrostatic potential properties.

Strategies to promote permeation and vectorization, and reduce cytotoxicity of metal complex luminophores for bioimaging and intracellular sensing

Transition metal luminophores are emerging as important tools for intracellular imaging and sensing. Their putative suitability for such applications has long been recognised but poor membrane permeability and cytotoxicity were significant barriers that impeded early progress. In recent years, numerous effective routes to overcoming these issues have been reported, inspired in part, by advances and insights from the pharmaceutical and drug delivery domains. In particular, the conjugation of biomolecules but also other less natural synthetic species, from a repertoire of functional motifs have granted membrane permeability and cellular targeting. Such motifs can also reduce cytotoxicity of transition metal complexes and offer a valuable avenue to circumvent such problems leading to promising metal complex candidates for application in bioimaging, sensing and diagnostics. The advances in metal complex probes permeability/targeting are timely, as, in parallel, over the past two decades significant technological advances in luminescence imaging have occurred. In particular, super-resolution imaging is enormously powerful but makes substantial demands of its imaging contrast agents and metal complex luminophores frequently possess the photophysical characteristics to meet these demands. Here, we review some of the key vectors that have been conjugated to transition metal complex luminophores to promote their use in intra-cellular imaging applications. We evaluate some of the most effective strategies in terms of membrane permeability, intracellular targeting and what impact these approaches have on toxicity and phototoxicity which are important considerations in a luminescent contrast or sensing agent.

Design and discovery of new antiproliferative 1,2,4-triazin-3(2H)-ones as tubulin polymerization inhibitors targeting colchicine binding site

Thirty-five new colchicine binding site inhibitors have been designed and synthesized based on the 1,2,4-triazin-3(2H)-one nucleus. Such molecules were synthesized through a cascade reaction between readily accessible α-amino ketones and phenyl carbazate as a masked N-isocyanate precursor. The synthesized derivatives are cisoid restricted combretastatin A4 analogues containing 1,2,4-triazin-3(2H)-one in place of the olefinic bond, and they have the same essential pharmacophoric features of colchicine binding site inhibitors. The synthesized compounds were evaluated in vitro for their antiproliferative activities against a panel of three human cancer cell lines (MCF-7, HepG-2, and HCT-116), using colchicine as a positive control. Among them, two compounds 5i and 6i demonstrated a significant antiproliferative effect against all cell lines with IC₅₀ ranging from 8.2 - 18.2 µM. Further investigation was carried out for the most active cytotoxic agents as tubulin polymerization inhibitors. Compounds 5i and 6i effectively inhibited microtubule assembly with IC₅₀ values ranging from 3.9 to 7.8 µM. Tubulin polymerization assay results were found to be comparable with the cytotoxicity results. The cell cycle analysis revealed significant G2/M cell cycle arrest of the analogue 5i in HepG-2 cells. The most active compounds 4i, 4j, 5 g, 5i and 6i did not induce significant cell death in normal human lung cells Wl-38, suggesting their selectivity against cancer cells. Also, These compounds upregulated the level of active caspase-3 and boosted the levels of the pro-apoptotic protein Bax by five to seven folds in comparison to the control. Moreover, apoptosis analyses were conducted for compound 5i to evaluate its apoptotic potential. Finally, in silico studies were conducted to reveal the probable interaction with the colchicine binding site. ADME prediction study of the designed compounds showed that they are not only with promising tubulin polymerization inhibitory activity but also with favorable pharmacokinetic and drug-likeness properties.

New bis([1,2,4]triazolo)[4,3-a:3',4'-c]quinoxaline derivatives as VEGFR-2 inhibitors and apoptosis inducers: Design, synthesis, in silico studies, and anticancer evaluation

A new series of bis([1,2,4]triazolo)[4,3-a:3',4'-c]quinoxaline derivatives were designed and synthesized to have the main essential pharmacophoric features of VEGFR-2 inhibitors. VEGFR-2 inhibitory activities were assessed for the designed compounds. In addition, cytotoxic activity was evaluated for all derivatives against two human cancer cell lines namely, HepG-2 and MCF-7. The most cytotoxic compound 20 h was subjected to further biological investigations including cell cycle, apoptosis, caspase-3, caspase-9, BAX, and Bcl-2 analyses. Different in silico studies as docking, ADMET and toxicity were carried out. The results exhibited that compounds 20b, 20e, 20h and20mshowed promising VEGFR-2 inhibitory activities with IC₅₀values of 5.7, 6.7, 3.2, and 3.1 µM, respectively. Moreover, these promising members exhibited the highest antiproliferative activities against the two cell lines with IC₅₀values ranging from 3.3 to 14.2 µM, comparing to sorafenib (IC₅₀ = 2.17 and 3.43 µM against HepG2 and MCF-7, respectively). Additionally, compound 20h induced cell cycle arrest of HepG2 cells at G2/M phase. Also, such compound increased the progress of apoptosis by 3.5-fold compared to the control. As well, compound 20h showed a significant increase in the level of caspase-3 (2.07-fold), caspase-9 (1.72-fold), and BAX (1.83-fold), and a significant decrease in Bcl-2 level (1.92-fold). The in silico studies revealed that the synthesized compounds have binding pattern like that of sorafenib.

Discovery of pyridine- sulfonamide hybrids as a new scaffold for the development of potential VEGFR-2 inhibitors and apoptosis inducers

New sulfonamide derivatives have been synthesized and tested as antitumor agents. All newly synthesized compounds were tested in vitro against 60 lines of human cancer cells. Compound VIIb shows broad-spectrum activity with a mean inhibition value of 91.67% against all cell lines. It exhibited potent anticancer activity with GI50 values of 1.06-8.92 μM relative to most of the tested cancer cell lines. Compound VIIb has been tested for enzyme inhibition activity toward vascular endothelial growth factor receptor 2, where VEGFR-2 was potently inhibited at a lower IC50 value of 3.6 μM, compared with sorafenib (IC50 = 4.8 μM). Hybrid VIIb was also able to induce cell cycle disturbance and apoptosis in Renal UO-31 cells, as shown by DNA flow cytometry and Annexin V-FITC/PI assays. It has also revealed lower Bcl-2 protein expression anti-apoptotic levels and higher BAX, p53, and caspases 3 expression levels.

Development of adamantane scaffold containing 1,3,4-thiadiazole derivatives: Design, synthesis, anti-proliferative activity and molecular docking study targeting EGFR

A new series of 1,3,4-thiadiazolo-adamantane derivatives were synthesized through molecular hybridization approach, then used as starting material to synthesize chloro and cyano acetamide-thiadiazole derivatives 2, 3. The newly designed compounds 1-3 were treated with different reagents to design 5-adamantyl thiadiazole derivatives 4-17 and evaluate their in vitro anti-proliferative activity against three cancer cell lines (MCF-7, HepG-2 and A549). Doxorubicin was used as a positive control. The most promising compounds 5, 6, 10a, 10b, 14b, 14c, and 17 showed up-regulation for BAX and down-regulation of Bcl-2, these findings proved their role as hopeful apoptotic inducers. In addition, the inhibitory activity against both wild EGFR^WT and mutant EGFR^L858R-TK for these derivatives revealed that compounds 5, 14c, and 17 have IC₅₀ value ranging from 85 nM to 71.5 nM against wild EGFR^WT and 37.85-41.19 nM against the mutant type, Lapatinib was used as a reference standard with IC₅₀ values of 31.8 nM and 39.53 nM, respectively. The most potent derivatives were subjected to further evaluation against double mutant EGFR ^L858R/T790M and showed good IC₅₀ values between (0.27-0.78 nM) compared to Lapatinib (0.18 nM) and Erlotinib (0.21 nM). Among them, thiazolo-thiadiazole adamantane derivative 17 exhibited the strongest inhibitory activity to the EGFR. Molecular docking studies were performed inside the active site of EGFR (1M17), and binding energy scores ranged between (-19.19 to -22.07 Kcal/mol) compared to Erlotinib (-19.10 Kcal/mol). Furthermore, oral bioavailability beside some pharmacokinetics properties of these derivatives were also investigated in this research work.

New quinoxaline derivatives as VEGFR-2 inhibitors with anticancer and apoptotic activity: Design, molecular modeling, and synthesis

New series of [1,2,4]triazolo[4,3-a]quinoxalin-4(5H)-one and [1,2,4]triazolo[4,3-a]quinoxaline derivatives have been designed, synthesized, and biologically assessed for their anti-proliferative activities against two selected tumor cell lines MCF-7 and HepG2. Comparing to sorafenib (IC₅₀ = 2.17 ± 0.13 and 3.51 ± 0.21 µM against MCF-7 and HepG2, respectively), compound 25d, 25e, 25i, and 27e exhibited the highest activities against the examined cell lines with IC₅₀ values extending from 4.1 ± 0.4 to 11.7 ± 1.1 µM. Furthermore, VEGFR-2 inhibitory activities were assessed for all the synthesized compounds as potential mechanisms for their anti-proliferative activities. Compounds 25d, 25e, 25i, and 27e displayed prominent inhibitory efficiency versus VEGFR-2 kinase with IC₅₀ value ranging from 3.4 ± 0.3 to 6.8 ± 0.5 nM. Fascinatingly, the results of VEGFR-2 inhibitory assays were matched with that of the cytotoxicity data, where the most potent anti-proliferative derivatives exhibited promising VEGFR-2 inhibitory activities. Further studies displayed the ability of compound 25d to induce apoptosis in HepG2 cells and can arrest the growth of such cells at the G2/M phase. Also, compound 25d produced a significant increase in the level of BAX/Bcl-2 ratio (3.8-fold), caspase- 3 (1.8-fold), and caspase-9 (1.9-fold) compared to the control cells. Molecular docking studies were carried out to investigate the possible binding interaction inside the active site of the VEGFR-2.

Synthesis and antimalarial and anticancer evaluation of 7-chlorquinoline-4-thiazoleacetic derivatives containing aryl hydrazide moieties

Twelve 7-chloroquinoline derivatives were designed and synthesized using the principle of molecular hybridization through the coupling of 2-[2-(7-chloroquinolin-4-ylthio)-4-methylthiazol-5-yl]acetic acid 1 with various benzoyl hydrazines 2a-l. The synthetic compounds were tested as antimalarials. Some of them showed an efficient in vitro activity as inhibitors of β-hematin formation and an in vivo activity in a murine model, resulting in compounds 8 and 9 as the most active ones with IC₅₀ values of 0.65 ± 0.09 and 0.64 ± 0.16 µM, respectively. The effects of the compounds on the cell viability, cell cycle, and apoptosis induction of A549 and MCF-7 cancer cell lines were also examined. Our data showed that compounds 6 and 12 were the most active agents, decreasing the cell viability of MCF-7 cells with IC₅₀ values of 15.41 and 12.99 µM, respectively. None of the compounds analyzed significantly affected the viability of peripheral blood mononuclear cells. Also, significant induction of apoptosis was observed when both cancer cell lines were incubated with compounds 6 and 12. In MCF-7 cells, treatment with these compounds led to cell cycle arrest in the G0/G1 phase. The results obtained suggest that these structures may be useful in developing new therapies for malaria and cancer treatment.

Discovery of novel triazolophthalazine derivatives as DNA intercalators and topoisomerase II inhibitors

A new series of triazolophthalazine derivatives was designed and synthesized as topoisomerase II (Topo II) inhibitors and DNA intercalators. The synthesized derivatives were evaluated in vitro for their cytotoxic activities against three human cancer cell lines: HepG2, MCF-7, and HCT-116 cells. Compound IX_b was the most potent counterpart with IC₅₀ values of 5.39 ± 0.4, 3.81 ± 0.2, and 4.38 ± 0.3 µM, as it was about 1.47, 1.77, and 1.19 times more active than doxorubicin (IC₅₀  = 7.94 ± 0.6, 6.75 ± 0.4, and 5.23 ± 0.3 µM) against HepG2, MCF-7, and HCT-116 cells, respectively. Additionally, the binding affinity of the synthesized compounds toward the DNA molecule was assessed using the DNA/methyl green assay. Compound IX_b showed an excellent DNA binding affinity with an IC₅₀ value of 27.16 ± 1.2 µM, which was better than that of the reference drug doxorubicin (IC₅₀  = 31.02 ± 1.80 µM). Moreover, compound IX_b was the most potent member among the tested compounds when investigated for their Topo II inhibitory activity. Furthermore, compound IX_b induced apoptosis in HepG2 cells and arrested the cell cycle at the G2/M phase. Additionally, compound IX_b showed Topo II poisoning effects at 2.5 μM and Topo II catalytic inhibitory effects at 5 and 10 μM. Finally, molecular docking studies were carried out against the DNA-Topo II complex and DNA, to investigate the binding patterns of the designed compounds.

Design, synthesis and molecular modeling of new quinazolin-4(3H)-one based VEGFR-2 kinase inhibitors for potential anticancer evaluation

Globally cancer is the second leading cause of death. So that this work is an attempt to develop new effective anti-cancer agents. In line with pharmacophoric features of VEGFR-2 kinase inhibitors, new nineteen quinazolin-4-one derivatives were designed, synthesized and biologically evaluated for their potential anticancer activity. All target compounds were evaluated in vitro for VEGFR-2 tyrosine kinase inhibition. Then, nine compounds of best results were further investigated by in vitro assay against three human cancer cell lines, namely HepG2, PC3 and MCF. N^'-{2-](3-Ethyl-6-nitro-4-oxo-3,4-dihydroquinazoline-2-yl)thio[acetyl}benzohydrazide (36) was found to be the most potent candidate as it showed IC₅₀ = 4.6 ± 0.06 µM against VEGFR-2 kinase. It also exhibited IC₅₀ = 17.23 ± 1.5, 26.10 ± 2.2 and 30.85 ± 2.3 µg/mL against HepG2, PC3 and MCF, respectively. At the same time it showed IC₅₀ = 145.93 ± 1.1 µg/mL against the normal human lung fibroblasts cell line (WI-38), indicating good selectivity index. Further investigation into HepG2 cell cycle showed the ability of compound 36 to induce apoptosis and arrest cell growth at G2/M phase. Moreover, docking studies demonstrated the ability of compound 36 to bind VEGFR-2 in a correct manner making three essential hydrogen bonds with the key residues Glu885, Asp1046 and Cys919. In sum, this work suggests that compound 36 can serve as a lead for development of effective anticancer agents targeting VEGFR-2.

Lipid-Raft-Targeted Molecular Self-Assembly Inactivates YAP to Treat Ovarian Cancer

The Yes-associated protein (YAP) is a major oncoprotein responsible for cell proliferation control. YAP's oncogenic activity is regulated by both the Hippo kinase cascade and uniquely by a mechanical-force-induced actin remodeling process. Inspired by reports that ovarian cancer cells specifically accumulate the phosphatase protein ALPP on lipid rafts that physically link to actin cytoskeleton, we developed a molecular self-assembly (MSA) technology that selectively halts cancer cell proliferation by inactivating YAP. We designed a ruthenium-complex-peptide precursor molecule that, upon cleavage of phosphate groups, undergoes self-assembly to form nanostructures specifically on lipid rafts of ovarian cancer cells. The MSAs exert potent, cancer-cell-specific antiproliferative effects in multiple cancer cell lines and in mouse xenograft tumor models. Our work illustrates how basic biochemical insights can be exploited as the basis for a nanobiointerface fabrication technology which links nanoscale protein activities at specific subcellular locations to molecular biological activities to suppress cancer cell proliferation.

Design, synthesis, docking study and anticancer evaluation of new trimethoxyphenyl pyridine derivatives as tubulin inhibitors and apoptosis inducers

Microtubules have become an appealing target for anticancer drug development including mainly colchicine binding site inhibitors (CBSIs). A new series of novel trimethoxypyridine derivatives were designed and synthesized as tubulin targeting agents. In vitro anti-proliferative activities of the tested compounds compared to colchicine against hepatocellular carcinoma (HepG-2), colorectal carcinoma (HCT-116), and breast cancer (MCF-7) was carried out. Most of compounds showed significant cytotoxic activities. Compounds Vb, Vc, Vf, Vj and VI showed superior anti-proliferative activities to colchicine. Where compound VI showed IC₅₀ values of 4.83, 3.25 and 6.11 μM compared to colchicine (7.40, 9.32, 10.41 μM) against HCT 116, HepG-2 and MCF-7, respectively. The enzymatic activity against tubulin enzyme was carried out for the compounds that showed high anti-proliferative activity. Also, compound VI exhibited the highest tubulin polymerization inhibitory effect with an IC₅₀ value of 8.92 nM compared to colchicine (IC₅₀ value = 9.85 nM). Compounds Vb, Vc, Vf, Vj, & VIIIb showed promising activities with IC₅₀ values of 22.41, 17.64, 20.39, 10.75, 31.86 nM, respectively. Cell cycle and apoptosis test for compound VI against HepG-2 cells, indicated that compound VI can arrest cell cycle at G2/M phase, and can cause apoptosis at pre-G1 phase, with high apoptotic effect 18.53%. Molecular docking studies of the designed compounds confirmed the essential hydrogen bonding with CYS241 beside the hydrophobic interaction at the binding site compared to reference compounds which assisted in the prediction of the structure requirements for the detected antitumor activity.

Interaction of compounds VI (IC₅₀ = 8.92 nM) (A) and Vj (IC₅₀ = 10.75 nM) (B) with key amino acids of CBS.

Novel piperazine-chalcone hybrids and related pyrazoline analogues targeting VEGFR-2 kinase; design, synthesis, molecular docking studies, and anticancer evaluation

New piperazine–chalcone hybrids and related pyrazoline derivatives have been designed and synthesised as potential vascular endothelial growth factor receptor-2 (VEGFR-2) inhibitors. The National Cancer Institute (NCI) has selected six compounds to evaluate their antiproliferative activity in vitro against 60 human cancer cells lines. Preliminary screening of the examined compounds indicated promising anticancer activity against number of cell lines. The enzyme inhibitory activity against VEGFR-2 was evaluated and IC₅₀ of the tested compounds ranged from 0.57 µM to 1.48 µM. The most potent derivatives Vd and Ve were subjected to further investigations. A cell cycle analysis showed that both compounds mainly arrest HCT-116 cell cycle in the G2/M phase. Annexin V-FITC apoptosis assay showed that Vd and Ve induced an approximately 18.7-fold and 21.2-fold total increase in apoptosis compared to the control. Additionally, molecular docking study was performed against VEGFR (PDB ID: 4ASD) using MOE 2015.10 software and Sorafenib as a reference ligand.

Design, molecular docking, in vitro, and in vivo studies of new quinazolin-4(3H)-ones as VEGFR-2 inhibitors with potential activity against hepatocellular carcinoma

A series of new VEGFR-2 inhibitors were designed, synthesized and evaluated for their anti-proliferative activities against hepatocellular carcinoma (HepG-2 cell line). Compound 29_b (IC₅₀ = 4.33 ± 0.2 µg/ml) was found to be the most potent derivative as it has showed to be more active than doxorubicin (IC₅₀ = 4.50 ± 0.2 µg/ml) and 78% of sorafenib activity (IC₅₀ = 3.40 ± 0.25 µg/ml). The inhibitory profiles against VEGFR-2 were also assessed for the most promising candidates (16_b, 20_c, 22_b, 24_a, 24_b, 28_c, 28_e, 29_a, 29_b and 29_c). Compounds 29_b, 29_c and 29_a exhibited potent inhibitory activities towards VEGFR-2 at IC₅₀ values of 3.1 ± 0.04, 3.4 ± 0.05 and 3.7 ± 0.06 µM, respectively, comparing sorafenib (IC₅₀ = 2.4 ± 0.05 µM). Furthermorer, compound 29_b induced apoptosis and arrested the cell cycle growth at G2/M phase. Additionally, in vivo antitumor experiments revealed that compounds 29_b and 29_c have significant tumor growth inhibition. The test of immuno-histochemical expression of activated caspase-3 revealed that there is a time-dependent increase in cleaved caspase-3 protein expression upon exposure of HepG-2 cells to compound 29_b. Moreover, the fibroblastic proliferative index test revealed that compound 29_b could attenuate liver fibrosis. Docking studies also supported the results concluded from the biological screening via prediction of the possible binding interactions of the target compounds with VEGFR-2 active sites using the crystal structure of VEGFR-2 downloaded from the Protein Data Bank, (PDB ID: 2OH4) using Discovery Studio 2.5 software. Further structural optimization of the most active candidates may serve as a useful strategy for getting new lead compounds in search for powerful and selective antineoplastic agents.

Antiproliferative Activity, Proapoptotic Effect, and Cell Cycle Arrest in Human Cancer Cells of Some Marine Natural Product Extract

Bioactive constituents of numerous marine organisms have been investigated recently for their preclinical and clinical anticancer activity. Three marine organisms: black-spotted sea cucumber: Pearsonothuria graeffei (Pg), lollyfish: Holothuria atra (Ha), and sea hare: Aplysia dactylomela (Ad), were collected during winter 2019 from Gulf of Aqaba, Red Sea, Egypt, and macerated with ethanol into three different extracts: PgE, HaE, and AdE, where each was in vitro assessed for its antiproliferative and proapoptotic properties on HepG2, HCT-116, and MCF-7 cancer cells. PgE dose-dependently inhibited the growth of HepG2, HCT-116, and MCF-7 cells within IC₅₀ values 16.22, 13.34, and 18.09 μg/mL, respectively, while the IC₅₀ values for the antiproliferative activity of HaE were 12.48, 10.45, and 10.36 μg/mL, respectively, and the IC₅₀ values of AdE were 6.51, 5.33, and 6.87 μg/mL, respectively. All extracts were found to induce G₀/G₁ cell cycle arrest for HepG2 cells side by side with their inhibition of CDK2 on all three cell lines while all extracts were also showed to induce apoptosis in HepG2 cell line at pre-G ₁ phase supplemented by their anticancer activity via proapoptotic protein Bax, caspase-3, and cleavage PARP increase, and antiapoptotic protein Bcl-2 downturn. Moreover, necrosis has been relatively noticed in HepG2 cell line as an additional anticancer activity for each extract. Our data introduced three ethanolic marine extracts as natural chemotherapeutic agents to be further developed for cancer control.

Design and discovery of new 1,2,4-triazolo[4,3-c]quinazolines as potential DNA intercalators and topoisomerase II inhibitors

A new series of 1,2,4-triazolo[4,3-c]quinazoline derivatives was designed and synthesized as Topo II inhibitors and DNA intercalators. The cytotoxic effect of the new members was evaluated in vitro against a group of cancer cell lines including HCT-116, HepG-2, and MCF-7. Compounds 14_c , 14_d , 14_e , 14_e , 15_b , 18_b , 18_c , and 19_b exhibited the highest activities with IC₅₀ values ranging from 5.22 to 24.24 µM. Furthermore, Topo II inhibitory activities and DNA intercalating affinities of the most promising candidates were evaluated as a possible mechanism for the antiproliferative effect. The results of the Topo II inhibition and DNA binding tests were coherent with that of in vitro cytotoxicity. Additionally, the most promising compound 18_c was analyzed in HepG-2 cells for its apoptotic effect and cell cycle arrest. It was found that 18_c can induce apoptosis and arrest the cell cycle at the G2-M phase. Finally, molecular docking studies were carried out for the designed compounds against the crystal structure of the DNA-Topo II complex as a potential target to explore their binding modes. On the basis of these studies, it was hypothesized that the DNA binding and/or Topo II inhibition would participate in the noted cytotoxicity of the synthesized compounds.

Development of pyridazine derivatives as potential EGFR inhibitors and apoptosis inducers: Design, synthesis, anticancer evaluation, and molecular modeling studies

Novel hybrids of pyridazine-pyrazoline were synthesized aiming to develop new antiproliferative candidates. All compounds were submitted to the National Cancer Institute (NCI), USA, and many were proved to have significant antiproliferative activity. In addition, in vitro studies of the epidermal growth factor receptor (EGFR) inhibition showed that compounds IXn, IXg, IXb and IXl exhibited excellent inhibitory effect (IC₅₀ = 0.65, 0.75, 0.82 and 0.84 μM, respectively) compared to Erlotinib (IC₅₀ = 0.95 μM). The mechanistic effectiveness in cell cycle progression, apoptotic induction and gene regulation were assessed for the promising compounds IXg and IXn due to their significant EGFR inhibition. Flow cytometeric analysis indicated that compounds IXg and IXn result in increased cell numbers in phase G2/M, suggesting cell cycle arrest in phase G2/M in UO-31cells. Furthermore, real time PCR assay illustrated that compounds IXg and IXn elevated Bax/Bcl2 ratio which confirmed the mechanistic pathway of them. Moreover, the apoptotic induction of UO-31 renal cancer cells was enhanced effectively through activation of caspase-3 by compounds IXg and IXn. On the other hand, molecular docking study was performed to investigate binding mode of interaction of compounds with EGFR-PK in the active site with the aim of rationalizing its promising inhibitory activity. Finally, based on the aforementioned findings, compounds IXg and IXn could be considered as effective apoptosis modulators and promising leads for future development of new anti-renal cancer agents.

New cyanopyridine-based scaffold as PIM-1 inhibitors and apoptotic inducers: Synthesis and SARs study

Two novel series of 6-(4-benzamido-/4-phthalimido)-3-cyanopyridine derivatives were designed and synthesized as inhibitors of PIM-1 kinase. Based on cytotoxicity results via MTT assay against prostate carcinoma PC3, human hepatocellular carcinoma HepG2 and breast adenocarcinoma MCF-7 cell lines, the most potent cytotoxic cyanopyridine hits, 6, 7, 8, 12 and 13 were 1.5-3.3 times more inhibitor of cell proliferation than the reference standard, 5-FU. Selectivity profile of the latter compounds on normal human cells (WI-38), was executed, indicating that they are highly selective (IC₅₀ > 145 μM) in their cytotoxic effect. The promising compounds were further evaluated as PIM-1 kinase inhibitors. These compounds elicited remarkable inhibition of PIM-1 kinase (76.43-53.33%). Extensive studies on apoptosis were conducted for these compounds; they enhanced caspase-3 and boosted the Bax/Bcl-2 ratio 27-folds in comparison to the control. Molecular docking study of the most potent compound, 13 in PIM-1 kinase active site was consistent with the in vitro activity. Finally, prediction of chemo-informatic properties released compound 13 as the most promising ligand.

Synthesis of new arylazopyrazoles as apoptosis inducers: Candidates to inhibit proliferation of MCF-7 cells

New 4-arylazo-3,5-diamino-1H-pyrazole derivatives substituted in the 4-aryl ring with the acetyl moiety were designed and synthesized. The antiproliferative activity of the novel arylazopyrazoles was examined against the MCF-7 cell line. Among all target compounds, 8b (IC₅₀ 3.0 µM) and 8f (IC₅₀ 4.0 µM) displayed higher cytotoxicity as compared with the reference standard imatinib (IC₅₀ 7.0 µM). Further studies to explore the mechanism of action were performed on the most active hit of our library, 8b, via anti-CDK2 kinase activity. It demonstrated good inhibitory effects for CDK2 (IC₅₀ 0.24 µM) with 62.5% inhibition, compared with imatinib. The cell cycle analysis in the MCF-7 cell line revealed apoptosis induction by 8b and cell cycle arrest at the S phase. Docking in the CDK2 active site and pharmacophore modeling confirmed the affinity of 8b to the CDK2 active site. Absorption, distribution, metabolism, and excretion studies revealed that our target compounds are orally bioavailable, with no permeation through the blood-brain barrier.

Design, synthesis and in silico studies of new quinazolinone derivatives as antitumor PARP-1 inhibitors

Herein, we report an eco-friendly synthesis of a new series of quinazolinone-based derivatives as potential PARP-1 inhibitors. The 4-quinazolinone scaffold was utilized as a bioisostere to the phthalazinone core of the reference compound Olaparib. Most of the synthesized compounds displayed appreciable inhibitory activity against PARP-1. Compound 12c showed inhibitory activity at IC50 = 30.38 nM comparable to Olaparib, which has IC50 = 27.89 nM. Cell cycle analysis was performed for compounds 12a and 12c, and both exhibited cell growth arrest at G2/M phase in the MCF-7 cell line. In addition, both compounds increased the programmed apoptosis compared to the control. Furthermore, molecular docking of the final compounds into the PARP-1 active site was executed to explore their probable binding modes. Also, a computational QSAR and in silico ADMET study was performed. The results of this study revealed that some of the newly synthesized compounds could serve as a new framework to discover new PARP-1 inhibitors with anti-cancer activity.

Tuning the Luminescent Properties of Ruthenium(II) Amino-1,10-Phenanthroline Complexes by Varying the Position of the Amino Group on the Heterocycle

Eight 1,10-phenanthrolines bearing one or two 2-(1-adamantyloxy)ethylamino substituents attached to different positions of the heterocyclic core were prepared according to S_N Ar or palladium-catalyzed amination reactions. Their reaction with cis-Ru(bpy)₂ Cl₂ (bpy=2,2'-bipyridine) was investigated and Ru(bpy)₂ (L)(PF₆ )₂ (phen=1,10-phenanthroline) (L=amino-substituted 1,10-phenanthroline) complexes were obtained in good yields. The electronic structure and emissive properties of these complexes are strongly dependent on the position of the amino substituent in the heterocycle. Emission bands of the complexes bearing 2- and 4-substituted 1,10-phenanthroline ligands are red-shifted (up to 56 nm) and less intense compared to that of the parent [Ru(phen)(bpy)₂ ](PF₆ )₂ . In contrast, the introduction of the substituent in 3- or 5-position of 1,10-phenanthroline ring induces only small decrease of luminescence and the brightness of the complex with the 3-substituted ligand is comparable to that of the parent complex.

Versatile Impact of Serum Proteins on Ruthenium(II) Polypyridyl Complexes Properties - Opportunities and Obstacles

Ruthenium(II) polypyridyl complexes have been extensively studied for the past few decades as promising anticancer agents. Despite the expected intravenous route of administration, the interaction between Ru(II) polypyridyl compounds and serum proteins is not well characterized and vast majority of the available literature data concerns determination of the binding constant. Ru-protein adducts can modify the biological effects of the Ru complexes influencing their cytotoxic and antimicrobial activity as well as introduce significant changes in their photophysical properties. More extensive research on the interaction between serum proteins and Ru(II) polypyridyl complexes is important for further development of Ru(II) polypyridyl compounds towards their application in anticancer therapy and diagnostics and can open new opportunities for already developed complexes.

Functional imaging of a model unicell: Spironucleus vortens as an anaerobic but aerotolerant flagellated protist

Advances in optical microscopy are continually narrowing the chasm in our appreciation of biological organization between the molecular and cellular levels, but many practical problems are still limiting. Observation is always limited by the rapid dynamics of ultrastructural modifications of intracellular components, and often by cell motility: imaging of the unicellular protist parasite of ornamental fish, Spironucleus vortens, has proved challenging. Autofluorescence of nicotinamide nucleotides and flavins in the 400-580 nm region of the visible spectrum, is the most useful indicator of cellular redox state and hence vitality. Fluorophores emitting in the red or near-infrared (i.e., phosphors) are less damaging and more penetrative than many routinely employed fluors. Mountants containing free radical scavengers minimize fluorophore photobleaching. Two-photon excitation provides a small focal spot, increased penetration, minimizes photon scattering and enables extended observations. Use of quantum dots clarifies the competition between endosomal uptake and exosomal extrusion. Rapid motility (161 μm/s) of the organism makes high resolution of ultrastructure difficult even at high scan speeds. Use of voltage-sensitive dyes determining transmembrane potentials of plasma membrane and hydrogenosomes (modified mitochondria) is also hindered by intracellular motion and controlled anesthesia perturbs membrane organization. Specificity of luminophore binding is always questionable; e.g. cationic lipophilic species widely used to measure membrane potentials also enter membrane-bounded neutral lipid droplet-filled organelles. This appears to be the case in S. vortens, where Coherent Anti-Stokes Raman Scattering (CARS) micro-spectroscopy unequivocally images the latter and simultaneous provides spectral identification at 2840 cm^-1. Secondary Harmonic Generation highlights the highly ordered structure of the flagella.

Molecular Design of Bioorthogonal Probes and Imaging Reagents Derived from Photofunctional Transition Metal Complexes

For more than 15 years, bioorthogonal chemistry has received increasing attention due to its successful applications in the detection and imaging of biomolecules in their native biological environments. The method typically proceeds with the incorporation of a biological substrate appended with a bioorthogonal functional group (chemical reporter), followed by the introduction of the substrate to biological systems. Biomolecules containing the substrate are then recognized by an exogenously delivered bioorthogonal probe. Despite the fact that many useful chemical reporters and bioorthogonal reactions have been developed, most of the bioorthogonal probes reported thus far are fluorescent dyes. A limitation is that stringent washing is required due to the interference caused by the background fluorescence of unreacted probes. Thus, fluorogenic probes with turn-on emission properties upon bioorthogonal labeling have been designed as an alternative strategy. These probes are highly appealing because excellent images can be obtained without the need for washing steps. Nearly all fluorogenic bioorthogonal probes designed are essentially organic dyes, their emission is limited to fluorescence, and the utilization of the probes is confined to bioimaging applications. Recently, there has been a growing interest in the bioimaging and therapeutic applications of luminescent inorganic and organometallic transition metal complexes due to their intriguing photophysical and photochemical properties, high membrane permeability, controllable cellular uptake, intracellular localization, and cytotoxicity. We anticipate that photofunctional transition metal complexes can be exploited as valuable bioorthogonal probes due to these appealing advantages. In this Account, we introduce the molecular design, photophysical and photochemical properties, and biological applications of various bioorthogonal probes and imaging reagents based on photofunctional transition metal complexes. The presence of a cationic metal center significantly enhances the bioorthogonal reactivity of the probes, yet their stability in aqueous solutions can be maintained. Interestingly, some of these metal complexes are strategically modified to display phosphorogenic properties, that is, phosphorescence turn-on upon bioorthogonal labeling reactions. Importantly, these probes not only exhibit favorable photophysical properties after bioorthogonal labeling, but also efficient photoinduced singlet oxygen (¹O₂) generation. This interesting bioorthogonal reaction-triggered photosensitization capability allows the modulation of ¹O₂ generation efficiency and contributes to the development of controllable photocytotoxic agents. The exploration of transition metal complex-based probes not only significantly widens the scope of bioorthogonal labeling but also further highlights the unique advantages of these complexes in the design of theranostic reagents. The development of these innovative reagents is expected to contribute to the basic understanding of biological processes in living systems and provide exciting opportunities for new diagnostic and therapeutic applications.

Benzoxazole derivatives as new generation of anti-breast cancer agents

New 2-substituted benzoxazole derivatives were synthesized and screened for their in vitro anti-proliferative activities against MCF-7 and MDA-MB-231 cell lines. Compounds 4b, 4d and 11c eliciting the highest activity against MCF-7 cells were further assayed for their cytotoxic activities against A431 and HCC827 cancer cells in addition to their in vitro inhibition of wild and mutated epidermal growth factor receptor (EGFR) enzymes. Compound 11c was the most active against A431 cells and it displayed a potent inhibition of EGFR^WT while compounds 4b and 4d elicited higher potencies than erlotinib against mutated EGFR^L858R. Compounds 4a, 6c and 8a showed the most potent cytotoxic activity against MDA-MB-231 cancer cells where compounds 4a and 6c were slightly less potent aromatase (ARO) inhibitors than letrozole. MCF-7 cells treated with compounds 4b, 4d, 11c and MDA-MB-231 cells treated with compounds 4a, 6c and 8a showed remarkable over-expression of caspase-9 protein level and elicited pre G1 apoptosis and cell cycle arrest at G2/M phase in addition to high annexin V binding affinity indicating significant apoptosis. Chemo-informatic and docking properties were also predicted. Docking results revealed that docked compounds displayed binding modes with EGFR and ARO enzymes comparable to that of the reference ligands. The benzoxazole derivatives 11c and 6c possessing amide and dithiocarbamate moieties respectively were found to be potent apoptosis-inducing anti-breast cancer agents with acceptable physicochemical properties. They exert their activity via inhibition of EGFR and ARO enzymes respectively.

Design, eco-friendly synthesis, molecular modeling and anticancer evaluation of thiazol-5(4H)-ones as potential tubulin polymerization inhibitors targeting the colchicine binding site

In recent years, suppressing tubulin polymerization has been developed as a therapeutic approach for cancer treatment. Thus, new derivatives based on thiazol-5(4H)-ones have been designed and synthesized in an eco-friendly manner. The synthesized derivatives have the same essential pharmacophoric features of colchicine binding site inhibitors. The anti-proliferative activity of the new derivatives was evaluated on three human cancer cell lines (HCT-116, HepG-2, and MCF-7) using MTT assay procedure and colchicine was used as a positive control. Compounds 4f, 5a, 8f, 8g, and 8k showed superior antiproliferative activities against the three tested cell lines with IC50 values ranging from 2.89 to 9.29 μM. Further investigation for the most active cytotoxic agents as tubulin polymerization inhibitors was also performed in order to explore the mechanism of their anti-proliferative activity. Tubulin polymerization assay results were found to be comperable with the cytotoxicity results. Compounds 4f and 5a were the most potent tubulin polymerization inhibitors with an IC50 value of 9.33 and 9.52 nM, respectively. Further studies revealed the ability of 5a to induce apoptosis and arrest cell cycle growth at the G2/M phase. Molecular docking studies were also conducted to investigate possible binding interactions between the target compounds and the tubulin heterodimer active site. From these studies, it was concluded that inhibition of tubulin polymerization yields the reported cytotoxic activity.

Targeted live-cell nuclear delivery of the DNA 'light-switching' Ru(II) complex via ion-pairing with chlorophenolate counter-anions: the critical role of binding stability and lipophilicity of the ion-pairing complexes

We have found recently that nuclear uptake of the cell-impermeable DNA light-switching Ru(II)-polypyridyl cationic complexes such as [Ru(bpy)2(dppz)]Cl2 was remarkably enhanced by pentachlorophenol (PCP), by forming ion-pairing complexes via a passive diffusion mechanism. However, it is not clear whether the enhanced nuclear uptake of [Ru(bpy)2(dppz)]2+ is only limited to PCP, or it is a general phenomenon for other highly chlorinated phenols (HCPs); and if so, what are the major physicochemical factors in determining nuclear uptake? Here, we found that the nuclear uptake of [Ru(bpy)2(dppz)]2+ can also be facilitated by other two groups of HCPs including three tetrachlorophenol (TeCP) and six trichlorophenol (TCP) isomers. Interestingly and unexpectedly, 2,3,4,5-TeCP was found to be the most effective one for nuclear delivery of [Ru(bpy)2(dppz)]2+, which is even better than the most-highly chlorinated PCP, and much better than its two other TeCP isomers. Further studies showed that the nuclear uptake of [Ru(bpy)2(dppz)]2+ was positively correlated with the binding stability, but to our surprise, inversely correlated with the lipophilicity of the ion-pairing complexes formed between [Ru(bpy)2(dppz)]Cl2 and HCPs. These findings should provide new perspectives for future investigations on using ion-pairing as an effective method for delivering other bio-active metal complexes into their intended cellular targets.

A nuclear permeable Ru(ii)-based photoactivated chemotherapeutic agent towards a series of cancer cells: in vitro and in vivo studies

Ru(ii) polypyridyl complexes which can undergo photo-induced ligand dissociation and DNA covalent binding are considered as potential photoactivated chemotherapeutic (PACT) agents. Herein four pyridine-2-sulfonate (py-SO3-) ligand based Ru(ii) complexes [Ru(N-N)2(py-SO3)]+ (1-4) were synthesized and studied. All the complexes can undergo fast py-SO3- ligand dissociation and DNA covalent binding upon visible light irradiation. However, only complex 4 exhibited high photo-induced anticancer activities towards a series of cancer cells, with half maximal inhibitory concentration (IC50) values in 100-300 nM regions and phototoxicity index (PI) values of about 100. In particular, complex 4 can also kill cisplatin resistant SKOV-3 and A549 cancer cells with IC50 values in 200-400 nM regions and PI values of about 50, which should be the first report of Ru(ii) based PACT agents that are also effective towards cisplatin resistant cancer cells. Complex 4 exhibited much higher cell uptake and nuclear accumulation levels, which may be the main reasons for its high anticancer activities. The in vivo anticancer experiments indicated that complex 4 can inhibit tumor growth significantly with fewer side effects. Our results may provide guidelines for developing novel photoactivatable Ru(ii) anticancer agents.

Discovery and antiproliferative evaluation of new quinoxalines as potential DNA intercalators and topoisomerase II inhibitors

In continuation of our previous work on the design and synthesis of topoisomerase II (Topo II) inhibitors and DNA intercalators, a new series of quinoxaline derivatives were designed and synthesized. The synthesized compounds were evaluated for their cytotoxic activities against a panel of three cancer cell lines (Hep G-2, Hep-2, and Caco-2). Compounds 18b, 19b, 23, 25b, and 26 showed strong potencies against all tested cell lines with IC₅₀ values ranging from 0.26 ± 0.1 to 2.91 ± 0.1 µM, comparable with those of doxorubicin (IC₅₀ values ranging from 0.65 ± 0.1 to 0.81 ± 0.1 µM). The most active compounds were further evaluated for their Topo II inhibitory activities and DNA intercalating affinities. Compounds 19b and 19c exhibited high activities against Topo II (IC₅₀ = 0.97 ± 0.1 and 1.10 ± 0.1 µM, respectively) and bound the DNA at concentrations of 43.51 ± 2.0 and 49.11 ± 1.8 µM, respectively, whereas compound 28b exhibited a significant affinity to bind the DNA with an IC₅₀ value of 37.06 ± 1.8 µM. Moreover, apoptosis and cell-cycle tests of the most promising compound 19b were carried out. It was found that 19b can significantly induce apoptosis in Hep G-2 cells. It has revealed cell-cycle arrest at the G2/M phase. Moreover, compound 19b downregulated the Bcl-2 levels, indicating its potential to enhance apoptosis. Furthermore, molecular docking studies were carried out against the DNA-Topo II complex to examine the binding patterns of the synthesized compounds.