Synthesis and biological evaluation of atropisomeric tetrahydroisoquinolines overcoming docetaxel resistance in triple-negative human breast cancer cells.

Herein, atropisomeric 8-aryltetrahydroisoquinolines have been synthesized and biologically evaluated. Based on our structure-activity relationship study, a highly bioactive racemic compound has been produced, and it exhibited high antiproliferative activities against various cancer cell lines, including docetaxel-resistant breast cancer cell lines. Each enantiomer can be synthesized in an enantioselective manner by employing the chiral phosphoric acid-catalyzed atroposelective Pictet-Spengler cyclization. An axially (R)-configured enantiomer showed a higher biological activity compared with the axially (S)-configured enantiomer. Further biological studies suggested that the (R)-enantiomer overcomes docetaxel resistance via the downregulation of signal transducer and activator of transcription 3 activation and consequently induces cellular apoptosis in docetaxel-resistant triple-negative breast cancer cell lines.

Anti-Inflammatory Activity of Glabralactone, a Coumarin Compound from Angelica sinensis, via Suppression of TRIF-Dependent IRF-3 Signaling and NF-κB Pathways.

The dried root of Angelica sinensis (A. sinensis) has been widely used in Chinese traditional medicine for various diseases such as inflammation, osteoarthritis, infections, mild anemia, fatigue, and high blood pressure. Searching for the secondary metabolites of A. sinensis has been mainly conducted. However, the bioactivity of coumarins in the plant remains unexplored. Therefore, this study was designed to evaluate the anti-inflammatory activity of glabralactone, a coumarin compound from A. sinensis, using in vitro and in vivo models, and to elucidate the underlying molecular mechanisms of action. Glabralactone effectively inhibited nitric oxide production in lipopolysaccharide- (LPS-) stimulated RAW264.7 macrophage cells. The downregulation of LPS-induced mRNA and protein expression of iNOS, TNF-α, IL-1ß, and miR-155 was found by glabralactone. The activation of NF-κB and TRIF-dependent IRF-3 pathway was also effectively suppressed by glabralactone in LPS-stimulated macrophages. Glabralactone (5 and 10 mg/kg) exhibited an in vivo anti-inflammatory activity with the reduction of paw edema volume in carrageenan-induced rat model, and the expressions of iNOS and IL-1ß proteins were suppressed by glabralactone in the paw soft tissues of the animal model. Taken together, glabralactone exhibited an anti-inflammatory activity in in vitro and in vivo models. These findings reveal that glabralactone might be one of the potential components for the anti-inflammatory activity of A. sinensis and may be prioritized in the development of a chemotherapeutic agent for the treatment of inflammatory diseases.

Catalytic and Enantioselective Control of the C-N Stereogenic Axis via the Pictet-Spengler Reaction.

An unprecedented example of a chiral phosphoric acid-catalyzed atroposelective Pictet-Spengler reaction of N-arylindoles is reported. Highly enantioenriched N-aryl-tetrahydro-ß-carbolines with C-N bond axial chirality are obtained via dynamic kinetic resolution. The hydrogen bond donor introduced on the bottom aromatic ring, forming a secondary interaction with the phosphoryl oxygen, is essential to achieving high enantioselectivity. A wide variety of substituents are tolerable with this transformation to provide up to 98 % ee. The application of electron-withdrawing group-substituted benzaldehydes enables the control of both axial and point stereogenicity. Biological evaluation of this new and unique scaffold shows promising antiproliferative activity and emphasizes the significance of atroposelective synthesis.

Enhancing Antiproliferative Activity and Selectivity of a FLT-3 Inhibitor by Proteolysis Targeting Chimera Conversion.

The receptor tyrosine kinase FLT-3 is frequently mutated in acute myeloid leukemia; however, current small molecule inhibitors suffer from limited efficacy in the clinic. Conversion of a FLT-3 inhibitor (quizartinib) into a proteolysis targeting chimera (PROTAC) results in a compound that induces degradation of FLT-3 ITD mutant at low nanomolar concentrations. Furthermore, the PROTAC is capable of inhibiting cell growth more potently than the warhead alone while inhibiting fewer off-target kinases. This enhanced antiproliferative activity occurs, despite a slight reduction in the PROTAC's kinase inhibitory activity, via an increased level of apoptosis induction suggesting nonkinase roles for the FLT-3 ITD protein. Additionally, the PROTAC is capable of inducing FLT-3 ITD degradation in vivo. These results suggest that degradation of FLT-3 ITD may provide a useful method for therapeutic intervention.

The roles of IP3 receptor in energy metabolic pathways and reactive oxygen species homeostasis revealed by metabolomic and biochemical studies.

Inositol 1,4,5-trisphosphate receptors (IP(3)Rs) are calcium channels modulating important calcium-mediated processes. Recent studies implicate IP(3)R in cell metabolism, but specific evidence is missing regarding IP(3)R's effects on actual metabolic pathways and key energy metabolites. Here, we applied metabolomics and molecular biology to compare DT40 cell lines devoid of IP(3)R (KO) and its wild-type (WT) counterpart. NMR and LC-MS metabolomic data showed that the KO cell line has a very different basic energy metabolism from the WT cell line, showing enhanced Warburg effect. In particular, the KO cells exhibited significant perturbation in energy charge, reduced glutathione and NADPH ratios with slower cellular growth rate. Subsequent flow cytometry results showed that the KO cell line has a higher level of general reactive oxygen species (ROS) but has a lower level of peroxynitrites. This ROS disturbance could be explained by observing lower expression of superoxide dismutase 2 (SOD2) and unchanged expression of catalase. The higher ROS seems to be involved in the slower growth rate of the KO cells, with an ROS scavenger increasing their growth rate. However, the KO and WT cell lines did not show any noticeable differences in AMPK and phosphorylated AMPK levels, suggesting possible saturation of AMPK-mediated metabolic regulatory circuit in both cells. Overall, our study reveals IP3R's roles in ROS homeostasis and metabolic pathways as well as the effects of its KO on cellular phenotypes.

Design, synthesis, and anticancer activity of C8-substituted-4'-thionucleosides as potential HSP90 inhibitors.

A series of C8-substituted-4'-thioadenosine analogs 3a-3g, 15, and 17 and their truncated derivatives 4a-4j, 23-25, and 27 have been successfully synthesized from d-ribose and d-mannose, respectively, employing Pummerer type or Vorbrüggen condensation reactions and the functionalization at the C8-position of nucleobase via Stille coupling or nucleophilic aromatic substitution reactions as key steps. All the synthesized compounds were assayed for their HSP90 inhibitory activity, but they were found to be inactive up to 100µM. However, the 8-iodo derivatives 15, 17, and 27 exhibited potent anticancer activity, indicating that different mechanism of action might be involved in their biological activity.

Regio- and stereoselective synthesis of 2'-ß-substituted-fluoroneplanocin A analogues as potential anticancer agents.

A series of 2'-ß-substituted-6'-fluoro-cyclopentenyl-pyrimidines and -purines 8 and 9 were successfully synthesized from d-ribose in a regio- and stereoselective manner. The functionalization at the C2-position of 6'-fluoro-cyclopentenyl nucleosides was achieved via regioselective protection of a hydroxyl group at the C3-position and stereoselective formation of C2-triflate followed by direct SN2 reaction with a fluoro or azido nucleophile. All the synthesized compounds were evaluated for their anticancer activities in several tumor cell lines, but were found to be neither active nor toxic.

Synthesis and biological evaluation of carbocyclic analogues of pachastrissamine.

A series of carbocyclic analogues of naturally-occurring marine sphingolipid pachastrissamine were prepared and biologically evaluated. The analogues were efficiently synthesized via a tandem enyne/diene-ene metathesis reaction as a key step. We found that the analogue 4b exhibited comparable cytotoxicity and more potent inhibitory activity against sphingosine kinases, compared to pachastrissamine. Molecular modeling studies were conducted to provide more detailed insight into the binding mode of 4b in sphingosine kinase. In our docking model, pachastrissamine and 4b were able to effectively bind to the binding pocket of sphingosine kinase 1 as co-crystalized sphingosine. However, 4b showed a hydrophobic interaction with Phe192, which suggests that it contributes to its increased inhibitory activity against sphingosine kinase 1.

Design, synthesis, and evaluation of a water-soluble antofine analogue with high antiproliferative and antitumor activity.

New water soluble antofine C-13a analogues were designed, synthesized, and evaluated for antiproliferative activity against cancer cells. Particularly, (-)-(R)-13a-hydroxymethylantofine ((-)-(R)-4b) demonstrated notable growth inhibition against a panel of human cancer cell lines. This growth inhibition was associated with the arrest of the cell cycle in the G0/G1 phases and suppression of mTOR signaling in human lung A549 cancer cells. Compound (-)-(R)-4b also overcame paclitaxel-resistance in human lung cancer cells (A549-Pa) by suppressing P-glycoprotein expression. Furthermore, compound (-)-(R)-4b significantly inhibited the tumor growth of A549 and A549-Pa xenografts in a nude mouse model, which suggests it is a promising novel antitumor agent with sufficient aqueous solubility.

All-round catalytic and atroposelective strategy via dynamic kinetic resolution for N-/2-/3-arylindoles.

As the complexity of organic molecules utilized by mankind increases, the phenomenon of atropisomerism is more frequently encountered. While a variety of well-established methods enable the control of a stereogenic center, a catalytic method for controlling a stereogenic axis in one substrate is typically unavailable for controlling axial chirality in other substrates with a similar structure. Herein, we report o-amidobiaryl as a flexible platform for chiral phosphoric acid-catalyzed atroposelective dynamic kinetic resolution. To demonstrate our strategy, three distinct types of arylindoles were utilized and reacted intermolecularly with ketomalonate in the presence of chiral phosphoric acid. An investigation of 46 substrates having an aromatic ring in different positions yields the desired products with excellent enantioselectivities. Computational investigation into the origin of enantioselectivity highlights the importance of the NH group. Given the biological significance of indoles, antiproliferative effects have been investigated; our scaffold exhibits good efficacy in this regard.

Organocatalytic Atroposelective Synthesis of Isoquinolines via Dynamic Kinetic Resolution.

Herein, a highly enantioselective Pictet-Spengler reaction for the synthesis of axially chiral tetrahydroisoquinolines via dynamic kinetic resolution is described. Chiral phosphoric acids catalyze cyclization to yield single regioisomeric isoquinolines with excellent enantioselectivities around the C-C bond up to 99% ee. The current protocol is effective for a wide range of substrates, and the observed enantiodivergence depends on the substituents on the catalysts.

A Novel cytarabine analog evokes synthetic lethality by targeting MK2 in p53-deficient cancer cells.

Most nucleoside anticancer drugs show a primary resistance to p53-deficient or p53-mutated cancer cells and are limited in the clinic to the treatment of hematological malignancies. However, 2'-fluoro-4'-seleno-ara-C (F-Se-Ara-C), a new generation of cytarabine (Ara-C) analogs, exhibited potent antitumor activity against the p53-deficient prostate cancer cell line PC-3. The distinct activity of F-Se-Ara-C was achieved by targeting the synthetic lethal interaction between p53 and mitogen-activated protein kinase-activated protein kinase-2 (MK2). MK2 is a checkpoint effector for DNA damage responses to drive cell cycle arrest and DNA repair in p53-deficient cancer cells. Therefore, targeting MK2 may be an effective therapeutic strategy that induces apoptosis for cancers deficient in p53. F-Se-Ara-C effectively induced anti-prostate cancer activity in vitro and in vivo by inhibition of MK2 activation in p53-deficient prostate cancer cells. Moreover, combining F-Se-Ara-C with cabozantinib, an anticancer drug currently in clinical use, induced synergistic antitumor activity in p53-deficient prostate cancer cells. Taken together, these data show that F-Se-Ara-C may become great anticancer drug candidate with its unique mechanism of action for overcoming the apoptotic resistance of p53-deficient cells by targeting the synthetic lethal interaction.

Overcoming the Intrinsic Gefitinib-resistance via Downregulation of AXL in Non-small Cell Lung Cancer.

BACKGROUND: Resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), such as gefitinib, is a limited factor in the treatment of non-small-cell lung cancer (NSCLC) patients. Therefore, ongoing studies are trying to identify EGFR-TKIs-resistant mechanisms and to discover novel therapeutic strategies and targets for NSCLC treatment. METHODS: In the present study, the possibility of overcoming intrinsic gefitinib-resistance was examined by regulating the expression of AXL. A natural product-derived antitumor agent, yuanhuadine (YD) was employed to modulate the expression of AXL in the cells. RESULTS: Treatment with YD effectively downregulated AXL expression in AXL-overexpressed gefitinib-resistant H1299 cells. The combination of gefitinib and YD exhibited a synergistic grwoth-inhibitory activity in H1299 cells by downregulation of AXL expression. CONCLUSIONS: Based on these findings, AXL was found to be a promising therapeutic target to overcome the intrinsic resistance to gefitinib in NSCLC. Furthermore, YD is able to effectively regulate the expression of AXL and thus it may be applicable as a potential lead compound for the treatment of gefitinib-resistant NSCLC.

A novel selenonucleoside suppresses tumor growth by targeting Skp2 degradation in paclitaxel-resistant prostate cancer.

Prostate cancer (PC) is the most common disease in men over age 50, and its prevalence rate has been gradually increasing since 1980. Taxane-derived anticancer agents are the primary agents used to treat metastatic prostate cancer patients; however, the side effects and acquired drug resistance limit the success of these therapies. Because there is no specific treatment for paclitaxel-resistant prostate cancer, it is necessary to develop new targets and therapeutic strategies to overcome the acquired resistance. In this study, the antitumor activity of a novel selenonucleoside (4'-selenofuranosyl-2,6-dichloropurine, LJ-2618), a third-generation nucleoside, and its plausible mechanisms of action in paclitaxel-resistant prostate cancer (PC-3-Pa) cells were investigated. The established PC-3-Pa cells exhibited over 100-fold resistance against paclitaxel compared to the paclitaxel-sensitive PC-3 cells. LJ-2618, however, effectively inhibited the proliferation of both cell lines with similar IC50 values in vitro. In PC-3-Pa cells, the activated PI3K/Akt signaling pathway was suppressed by LJ-2618 treatment. In addition, Skp2 was found to be over-expressed in paclitaxel-resistant cells, and the transfection of Skp2 siRNA recovered the sensitivity of paclitaxel in PC-3-Pa cells. Furthermore, LJ-2618 significantly down-regulated Skp2 expression in PC-3-Pa cells by promoting degradation and inducing destabilization of Skp2, which triggers G2/M cell cycle arrest. In a xenograft mouse model implanted with PC-3-Pa cells, LJ-2618 (3 or 10 mg/kg) effectively inhibited tumor growth with the enhancement of Skp2 degradation and induction of p27 expression in tumor tissues. These findings suggest that LJ-2618 may have potential for overcoming paclitaxel resistance via promoting Skp2 degradation and stabilizing p27 expression in PC-3-Pa cells. Therefore, the novel selenonucleoside LJ-2618 may lead to the development of a new treatment strategy for patients with paclitaxel-resistant, castration-resistant prostate cancer.

Synthesis, structural characterization and biological evaluation of 4'-C-methyl- and phenyl-dioxolane pyrimidine and purine nucleosides.

Nucleoside analogues play an important role in antiviral, antibacterial and antineoplastic chemotherapy. Herein we report the synthesis, structural characterization and biological activity of some 4'-C -methyl- and -phenyl dioxolane-based nucleosides. In particular, α and ß anomers of all natural nucleosides were obtained and characterized by NMR, HR-MS and X-ray crystallography. The compounds were tested for antimicrobial activity against some representative human pathogenic fungi, bacteria and viruses. Antitumor activity was evaluated in a large variety of human cancer cell-lines. Although most of the compounds showed non-significant activity, 23α weakly inhibited HIV-1 multiplication. Moreover, 22α and 32α demonstrated a residual antineoplastic activity, interestingly linked to the unnatural α configuration. These results may provide structural insights for the design of active antiviral and antitumor agents.

Multiplicity of acquired cross-resistance in paclitaxel-resistant cancer cells is associated with feedback control of TUBB3 via FOXO3a-mediated ABCB1 regulation.

Acquired drug resistance is a primary obstacle for effective cancer therapy. The correlation of point mutations in class III ß-tubulin (TUBB3) and the prominent overexpression of ATP-binding cassette P-glycoprotein (ABCB1), a multidrug resistance gene, have been protruding mechanisms of resistance to microtubule disruptors such as paclitaxel (PTX) for many cancers. However, the precise underlying mechanism of the rapid onset of cross-resistance to an array of structurally and functionally unrelated drugs in PTX-resistant cancers has been poorly understood. We determined that our established PTX-resistant cancer cells display ABCB1/ABCC1-associated cross-resistance to chemically different drugs such as 5-fluorouracil, docetaxel, and cisplatin. We found that feedback activation of TUBB3 can be triggered through the FOXO3a-dependent regulation of ABCB1, which resulted in the accentuation of induced PTX resistance and encouraged multiplicity in acquired cross-resistance. FOXO3a-directed regulation of P-glycoprotein (P-gp) function suggests that control of ABCB1 involves methylation-dependent activation. Consistently, transcriptional overexpression or downregulation of FOXO3a directs inhibitor-controlled protease-degradation of TUBB3. The functional PI3K/Akt signaling is tightly responsive to FOXO3a activation alongside doxorubicin treatment, which directs FOXO3a arginine hypermethylation. In addition, we found that secretome factors from PTX-resistant cancer cells with acquired cross-resistance support a P-gp-dependent association in multidrug resistance (MDR) development, which assisted the FOXO3a-mediated control of TUBB3 feedback. The direct silencing of TUBB3 reverses induced multiple cross-resistance, reduces drug-resistant tumor mass, and suppresses the impaired microtubule stability status of PTX-resistant cells with transient cross-resistance. These findings highlight the control of the TUBB3 response to ABCB1 genetic suppressors as a mechanism to reverse the profuse development of multidrug resistance in cancer.

Antitumor activity of phenanthroindolizidine alkaloids is associated with negative regulation of Met endosomal signaling in renal cancer cells.

Met is a receptor tyrosine kinase for hepatocyte growth factor. Met mutations have been considered as a major cause of primary resistance to Met tyrosine kinase inhibitors (TKIs). Mutated Met enhances its endosomal signaling, which includes internalization, signaling within endosomes, recycling to membrane, and sorting for degradation. These sequential events lead to a plausible mechanism for resistance. (-)-Antofine, a phenanthroindolizidine alkaloid, has exhibited potent antitumor activity but the precise underlying mechanism has been poorly understood. We found that (-)-antofine effectively inhibited the proliferation of Met-mutated Caki-1 cells, which were resistant to well-known Met TKIs. (-)-Antofine negatively regulated Met endosomal signaling and consequently inhibited the nuclear translocation of STAT3 both in vitro and in vivo. These findings emphasize the potential of Met endosomal signaling as a novel target for Met TKI-resistant cancers and (-)-antofine as a novel lead compound associated with the suppression of Met endosomal signaling.

Design, Synthesis, and Biological Activity of Sulfonamide Analogues of Antofine and Cryptopleurine as Potent and Orally Active Antitumor Agents.

Due to their profound antiproliferative activity and unique mode of action, phenanthroindolizidine and phenanthroquinolizidine alkaloids, represented by antofine and cryptopleurine, have attracted attention recently as potential therapeutic agents. We have designed, synthesized, and evaluated the methanesulfonamide analogues of these natural alkaloids with the hope of improving their druglikeness. The analogues showed enhanced growth inhibition of human cancer cells compared with the parent natural products. In particular, a methanesulfonamide analogue of cryptopleurine (5b) exhibited improved bioavailability and significant antitumor activity, which suggests that 5b is a promising new anticancer agent. Our studies suggest that the inhibition of cancer cell growth by 5b is associated with the induction of G0/G1 cell cycle arrest via nicotinamide N-methyltransferase-dependent JNK activation in Caki-1 renal cancer cells. In addition, compound 5b significantly inhibited the migration and invasion of Caki-1 cancer cells by modulating the p38 MAPK signaling pathway.

Suppression of MAPK Signaling and Reversal of mTOR-Dependent MDR1-Associated Multidrug Resistance by 21α-Methylmelianodiol in Lung Cancer Cells.

Lung cancer is the leading cause of cancer-related deaths worldwide and remains the most prevalent. Interplay between PI3K/AMPK/AKT and MAPK pathways is a crucial effector in lung cancer growth and progression. These signals transduction protein kinases serve as good therapeutic targets for non-small cell lung cancer (NSCLC) which comprises up to 90% of lung cancers. Here, we described whether 21α-Methylmelianodiol (21α-MMD), an active triterpenoid derivative of Poncirus trifoliate, can display anticancer properties by regulating these signals and modulate the occurrence of multidrug resistance in NSCLC cells. We found that 21α-MMD inhibited the growth and colony formation of lung cancer cells without affecting the normal lung cell phenotype. 21α-MMD also abrogated the metastatic activity of lung cancer cells through the inhibition of cell migration and invasion, and induced G0/G1 cell cycle arrest with increased intracellular ROS generation and loss of mitochondrial membrane integrity. 21α-MMD regulated the expressions of PI3K/AKT/AMPK and MAPK signaling which drove us to further evaluate its activity on multidrug resistance (MDR) in lung cancer cells by specifying on P-glycoprotein (P-gp)/MDR1-association. Employing the established paclitaxel-resistant A549 cells (A549-PacR), we further found that 21α-MMD induced a MDR reversal activity through the inhibition of P-gp/MDR1 expressions, function, and transcription with regained paclitaxel sensitivity which might dependently correlate to the regulation of PI3K/mTOR signaling pathway. Taken together, these findings demonstrate, for the first time, the mechanistic evaluation in vitro of 21α-MMD displaying growth-inhibiting potential with influence on MDR reversal in human lung cancer cells.

Synthesis and biological evaluation of 2'-substituted-4'-selenoribofuranosyl pyrimidines as antitumor agents.

The 2'-substituted-4'-selenoribofuranosyl pyrimidines 3a-3j were synthesized from D-ribose and assayed for anticancer activity. The 2'-azido and 2'-fluoro groups with a ribo configuration were introduced by the regioselective opening of the O2,2'-anhydronucleosides with sodium azide and (HF)x-pyridine, respectively. Among the compounds tested, only 2'-fluoro derivative 3j was found to exhibit significant anticancer activity, but was much less potent than the corresponding 2'-arabino analogue 2c. This study will provide medicinal chemists with the insight into the identification of structural requirements for the anticancer activity for the developments of biologically active nucleosides.