Lamellarin 14, a derivative of marine alkaloids, inhibits the T790M/C797S mutant epidermal growth factor receptor.

The emergence of acquired resistance is a major concern associated with molecularly targeted kinase inhibitors. The C797S mutation in the epidermal growth factor receptor (EGFR) confers resistance to osimertinib, a third-generation EGFR-tyrosine kinase inhibitor (EGFR-TKI). We report that the derivatization of the marine alkaloid topoisomerase inhibitor lamellarin N provides a structurally new class of EGFR-TKIs. One of these, lamellarin 14, is effective against the C797S mutant EGFR. Bioinformatic analyses revealed that the derivatization transformed the topoisomerase inhibitor-like biological activity of lamellarin N into kinase inhibitor-like activity. Ba/F3 and PC-9 cells expressing the EGFR in-frame deletion within exon 19 (del ex19)/T790M/C797S triple-mutant were sensitive to lamellarin 14 in a dose range similar to the effective dose for cells expressing EGFR del ex19 or del ex19/T790M. Lamellarin 14 decreased the autophosphorylation of EGFR and the downstream signaling in the triple-mutant EGFR PC-9 cells. Furthermore, intraperitoneal administration of 10 mg/kg lamellarin 14 for 17 days suppressed tumor growth of the triple-mutant EGFR PC-9 cells in a mouse xenograft model using BALB/c nu/nu mice. Thus, lamellarin 14 serves as a novel structural backbone for an EGFR-TKI that prevents the development of cross-resistance against known drugs in this class.

Synthesis and evaluation of azalamellarin N and its A-ring-modified analogues as non-covalent inhibitors of the EGFR T790M/L858R mutant.

Azalamellarin N, a synthetic lactam congener of the marine natural product lamellarin N, and its A-ring-modified analogues were synthesized and evaluated as potent and non-covalent inhibitors of the drug-resistant epidermal growth factor receptor T790M/L858R mutant. An in vitro tyrosine kinase assay indicated that the inhibitory activities of the synthetic azalamellarin analogues were higher than those of the corresponding lamellarins. The azalamellarin analogue bearing two 3-(dimethylamino)propoxy groups at C20- and C21-positions exhibited the highest activity and selectivity against the mutant kinase [IC50 (T790M/L858R) = 1.7 nM; IC50 (WT) = 4.6 nM]. The inhibitory activity was attributed to the hydrogen bonding interaction between the lactam NH group of the B-ring and carbonyl group of a methionine residue.

IMU1003, an atrarate derivative, inhibits Wnt/ß-catenin signaling.

Aberrant activation of the canonical Wnt/ß-catenin signaling pathway triggers tumorigenesis in various tissues. This study identified an atrarate compound, IMU14, derived from filamentous fungi as an inhibitor of Wnt/ß-catenin signaling in phenotypic chemical inhibitor screening of the zebrafish eyeless phenotype. Its derivatization resulted in synthesis of IMU1003 with enhanced Wnt inhibitory activity. IMU1003 inhibited ß-catenin/TCF-dependent transcriptional activation and decreased nuclear ß-catenin level. In addition, IMU1003 selectively decreased viability and target gene products of the Wnt/ß-catenin signaling pathway in human non-colorectal cancer cell lines harboring intact APC and ß-catenin. Therefore, atrarate derivatives inhibit Wnt/ß-catenin signaling and show anticancer potential, and we developed a new class of chemical backbones for Wnt/ß-catenin signaling inhibitors.

Clotrimazole inhibits the Wnt/ß-catenin pathway by activating two eIF2α kinases: The heme-regulated translational inhibitor and the double-stranded RNA-induced protein kinase.

The Wnt/ß-catenin signaling pathway controls cell proliferation and differentiation, and therefore, when this pathway is excessively activated, it causes tumorigenesis. Our chemical suppressor screening in zebrafish embryos identified antifungal azoles including clotrimazole, miconazole, and itraconazole, as Wnt/ß-catenin signaling inhibitors. Here we show the mechanism underlying the Wnt/ß-catenin pathway inhibition by antifungal azoles. Clotrimazole reduced ß-catenin revels in a proteasome-independent fashion. By gene knockdown of two translational regulators, heme-regulated translational inhibitor and double-stranded RNA-induced protein kinase, we show that they mediate the clotrimazole-induced inhibition of the Wnt/ß-catenin pathway. Thus, clotrimazole inhibits the Wnt/ß-catenin pathway by decreasing ß-catenin protein levels through translational regulation. Antifungal azoles represent genuine candidate compounds for anticancer drugs or chemopreventive agents that reduce adenomatous polyps.

Design, synthesis, and evaluation of A-ring-modified lamellarin N analogues as noncovalent inhibitors of the EGFR T790M/L858R mutant.

A series of A-ring-modified lamellarin N analogues were designed, synthesized, and evaluated as potential noncovalent inhibitors of the EGFR T790M/L858R mutant, a causal factor in the drug-resistant non-small cell lung cancer. Several water-soluble ammonium- or guanidinium-tethered analogues exhibited good kinase inhibitory activities. The most promising analogue, 14f, displayed an excellent inhibitory profile against the T790M/L858R mutant [IC50 (WT) = 31.8 nM; IC50 (T790M/L858R) = 8.9 nM]. The effects of A-ring-substituents on activity were rationalized by docking studies.

p38MAPK and Rho-dependent kinase are involved in anoikis induced by anicequol or 25-hydroxycholesterol in DLD-1 colon cancer cells.

Anchorage-independent growth is evidence of the malignant transformation of cells. We previously reported the characterization of anicequol, a novel inhibitor of the anchorage-independent growth of tumor cells, and here we show that the effects of 25-hydroxycholesterol (25-HC) on colon cancer cells were very similar to those of anicequol. By analyzing the effects of inhibitors and performing RNA interference experiments, we found that p38 mitogen-activated protein kinase (p38MAPK) was involved in anicequol- and 25-HC-induced anoikis in DLD-1 cells. In addition, Rho-associated, coiled-coil containing protein kinase (ROCK) was also associated with anoikis induced by anicequol or 25-HC. Taken together, our findings suggest that activation of the p38MAPK and ROCK pathways might provide a new therapeutic strategy against cancer, and raise the possibility that tumor metastasis is influenced by 25-HC under physiological conditions.

Ivermectin represses Wnt/ß-catenin signaling by binding to TELO2, a regulator of phosphatidylinositol 3-kinase-related kinases.

Ivermectin (IVM), an avermectin-derivative anthelmintic, specifically binds to glutamate-gated chloride ion channels (GluCls), causing paralysis in invertebrates. IVM also exhibits other biological activities such as Wnt/ß-catenin pathway inhibition in vertebrates that do not possess GluCls. This study showed that affinity purification using immobilized IVM B1a isolated TELO2, a cofactor of phosphatidylinositol 3-kinase-related kinases (PIKKs), as a specific IVM B1a-binding protein. TELO2 knockdown reduced cytoplasmic ß-catenin and the transcriptional activation of ß-catenin/TCF. IVM B1a bound to TELO2 through the C-terminal α-helix, in which mutations conferred IVM resistance. IVM reduced the TELO2 and PIKK protein levels and the AKT and S6 kinase phosphorylation levels. The inhibition of mTOR kinase reduced the cytoplasmic ß-catenin level. Therefore, IVM binds to TELO2, inhibiting PIKKs and reducing the cytoplasmic ß-catenin level. In conclusion, our data indicate TELO2 as a druggable target for human diseases involving abnormalities of the Wnt/ß-catenin pathway and PIKKs, including mTOR.

Identification of LY83583 as a specific inhibitor of Candida albicans MPS1 protein kinase.

Candida albicans is the most common and virulent fungus causing candidiasis in various parts of the body and can be lethal to immunocompromised patients. All currently known antifungal therapies are drugs which cause serious side effects in the host. An inhibitor specific for fungus survival is an ideal therapeutic. C. albicans MPS1 (monopolar spindle 1) has been reported as a kinase essential to its survival. Because CaMps1p shares limited sequence homology with the human ortholog (hMps1p), we screened for a chemical inhibitor in anticipation of finding one with Candida specific cytotoxicity. In vitro screening using a recombinant catalytic domain of CaMps1p identified LY83583 (6-anilino-5,8-quinolinedione), known as a guanylate cyclase inhibitor, to be blocking CaMps1p kinase activity. In addition to its in vitro kinase inhibition, LY83583 reduced the growth rate of C. albicans. Finally, we compared the inhibitory activity on CaMps1p and hMps1p among inhibitors against those kinases. LY83583 showed specific inhibition for CaMps1p with no effect on hMps1p activity. Conversely, the CaMps1p activity was not affected by known hMps1p inhibitors. These findings suggest that CaMps1p may well be an ideal target molecule for antifungal therapy.

The resorcylic acid lactone hypothemycin selectively inhibits the mitogen-activated protein kinase kinase-extracellular signal-regulated kinase pathway in cells.

The resorcylic acid lactone hypothemycin has been shown to inactivate protein kinases by binding to a cysteine conserved in 46 protein kinases, including mitogen-activated protein kinase kinase (MEK), extracellular signal-regulated kinase (ERK) and platelet-derived growth factor receptor (PDGFR). We assessed the selectivity of hypothemycin in cellular contexts. Hypothemycin normalized the morphology and inhibited anchorage-independent growth of Ki-ras transformed normal rat kidney (NRK) cells with selectivity and potency comparable to or greater than that of the MEK inhibitor U0126. In Ki-ras-transformed and phorbol 12-myristate 13-acetate (PMA)-treated NRK cells, hypothemycin blocked ERK activation but showed a minimal effect on autophosphorylation of protein kinase D1 (PKD1), another kinase containing the conserved cysteine. Hypothemycin potently inhibited PDGFR autophosphorylation and activation of the MEK-ERK pathway in platelet-derived growth factor (PDGF)-treated NRK cells. However, the phosphoinositide-3-kinase (PI3K) pathway was only modestly attenuated. Hypothemycin also inhibited growth factor- and anchorage-independent growth of human cancer cell lines with a constitutively active MEK-ERK pathway. Although hypothemycin has the potential to inactivate various protein kinases, the results indicate that in intracellular environments, hypothemycin can inhibit the MEK-ERK axis with sufficient selectivity to normalize transformed phenotypes of cells dependent on this pathway.

Identification of the putative protein phosphatase gene PTC1 as a virulence-related gene using a silkworm model of Candida albicans infection.

Protein phosphatases are critical for the regulation of many cellular processes. Null mutants of 21 putative protein phosphatases of Candida albicans were constructed by consecutive allele replacement using the URA3 and ARG4 marker genes. A simple silkworm model of C. albicans infection was used to screen the panel of mutants. Four null mutant (cmp1Delta, yvh1Delta, sit4Delta, and ptc1Delta) strains showed attenuated virulence in the silkworm model relative to that of control and parental strains. Three of the mutants, the cmp1Delta, yvh1Delta, and sit4Delta mutants, had previously been identified as affecting virulence in a conventional mouse model, indicating the validity of the silkworm model screen. Disruption of the putative protein phosphatase gene PTC1 of C. albicans, which has 52% identity to the Saccharomyces cerevisiae type 2C protein phosphatase PTC1, significantly reduced virulence in the silkworm model. The mutant was also avirulent in a mouse model of disseminated candidiasis. Reintroducing either of the C. albicans PTC1 alleles into the disruptant strain, using a cassette containing either allele under the control of a constitutive ACT1 promoter, restored virulence in both infection models. Characterization of ptc1Delta revealed other phenotypic traits, including reduced hyphal growth in vitro and in vivo, and reduced extracellular proteolytic activity. We conclude that PTC1 may contribute to pathogenicity in C. albicans.

Design of antiangiogenic hypoxic cell radiosensitizers: 2-nitroimidazoles containing a 2-aminomethylene-4-cyclopentene-1,3-dione moiety.

We designed chiral 2-nitroimidazole derivatives containing a 2-aminomethylene-4-cyclopentene-1,3-dione moiety as antiangiogenic hypoxic cell radiosensitizers. Based on results of molecular orbital calculations, the 2-aminomethylene-4-cyclopentene-1,3-dione moiety is expected to show high electrophilicity comparable to that of the 2-methylene-4-cyclopentene-1,3-dione moiety included in TX-1123 and tyrphostin AG17. We evaluated the antiangiogenic and radiosensitizing effects of the new compounds, along with other biological properties including their activities as hypoxic cytotoxicities and protein tyrosine kinase (PTK) inhibitory activities. Among the compounds tested, 5 (TX-2036) proved to be the strongest antiangiogenic hypoxic cell radiosensitizer. All the other chiral 2-nitroimidazole derivatives having 2-aminomethylene-4-cyclopentene-1,3-dione moiety tested were also antiangiogenic hypoxic cell radiosensitizers. The PTK inhibitory activity of 5 (TX-2036) showed this to be a promising and potent EGFR kinase inhibitor, having an IC(50) value of lower than 2microM. This compound also was an Flt-1 kinase inhibitor having an IC(50) value of lower than 20microM. Our results show that these chiral 2-nitroimidazole derivatives that contain the 2-aminomethylene-4-cyclopentene-1,3-dione moiety as a potent antiangiogenic pharmacophoric descriptor are promising lead candidates for the development of antiangiogenic hypoxic cell radiosensitizers.

Sensitisation of Cancer Cells to MLN8237, an Aurora-A Inhibitor, by YAP/TAZ Inactivation.

BACKGROUND: Transcriptional co-activators YES-associated protein (YAP) and transcriptional coactivator with PDZ-motif (TAZ) stimulate the expression of cell cycle-related genes to permit for tumour cell growth. MLN8237 is a potent aurora-A kinase inhibitor; however, patients responding to MLN8237 are limited. Therefore, rational combination therapy could enhance their response. MATERIALS AND METHODS: YAP and TAZ were depleted using siRNA and then treated with MLN8237 in YAP/TAZ-dependent OVCAR-8 and MDA-MB-231 cell lines. MLN8237 was combined with fluvastatin, an agent constraining nuclear localisation of YAP/TAZ for potential combination therapy in vitro. RESULTS: Depletion of either YAP or TAZ sensitised these cell lines to MLN8237, resulting in apoptosis and reduction in aurora-A. MLN8237 reduced YAP/TAZ expression. A combination of MLN8237 with fluvastatin effectively reduced the cell viability of OVCAR-8 and MDA-MB-231 cell lines. CONCLUSION: A combination of MLN8237 and small-molecule agents inactivating YAP/TAZ, such as statins, could be a novel therapeutic strategy for YAP/TAZ-dependent cancer.

Augmentation of the therapeutic efficacy of WEE1 kinase inhibitor AZD1775 by inhibiting the YAP-E2F1-DNA damage response pathway axis.

The main reasons for failure of cancer chemotherapy are intrinsic and acquired drug resistance. The Hippo pathway effector Yes-associated protein (YAP) is associated with resistance to both cytotoxic and molecular targeted drugs. Several lines of evidence indicate that YAP activates transcriptional programmes to promote cell cycle progression and DNA damage responses. Therefore, we hypothesised that YAP is involved in the sensitivity of cancer cells to small-molecule agents targeting cell cycle-related proteins. Here, we report that the inactivation of YAP sensitises the OVCAR-8 ovarian cancer cell line to AZD1775, a small-molecule WEE1 kinase inhibitor. The accumulation of DNA damage and mitotic failures induced by AZD1775-based therapy were further enhanced by YAP depletion. YAP depletion reduced the expression of the Fanconi anaemia (FA) pathway components required for DNA repair and their transcriptional regulator E2F1. These results suggest that YAP activates the DNA damage response pathway, exemplified by the FA pathway and E2F1. Furthermore, we aimed to apply this finding to combination chemotherapy against ovarian cancers. The regimen containing dasatinib, which inhibits the nuclear localisation of YAP, improved the response to AZD1775-based therapy in the OVCAR-8 ovarian cancer cell line. We propose that dasatinib acts as a chemosensitiser for a subset of molecular targeted drugs, including AZD1775, by targeting YAP.

Inhibition of fungal ABC transporters by unnarmicin A and unnarmicin C, novel cyclic peptides from marine bacterium.

Novel inhibitors of fungal ATP-binding cassette transporters were obtained by screening compounds and crude extracts from marine-derived fungi and bacteria using disk diffusion assays of Saccharomyces cerevisiae strains overexpressing a variety of fungal multi-drug efflux pumps. The cyclodepsipeptides unnarmicin A and unnarmicin C were able to sensitize cells overexpressing azole drug pumps ScPdr5p, CaCdr1p, CgCdr1p, and CgPdh1p to sub-MIC concentrations of fluconazole without affecting the growth of CaCdr2p and CaMdr1p overexpressing cells. Unnarmicin A and unnarmicin C were potent inhibitors of rhodamine 6G efflux of CaCdr1p expressing cells with IC50 values of 3.61 and 5.65 microM, respectively. They inhibited the in vitro CaCdr1p ATPase activity at IC50 values of 0.495 and 0.688 microM, respectively. And most importantly, they were able to sensitize azole-resistant Candida albicans clinical isolates to fluconazole. Unnarmicin A and unnarmicin C are candidate efflux pump inhibitors with the potential to be used as adjuvants for antifungal chemotherapy.

Construction of a pair of practical Nocardia-Escherichia coli shuttle vectors.

We constructed a pair of Nocardia-Escherichia coli shuttle vectors, pNV18 and pNV19, by combining the mycobacterial plasmid pAL5000 with the E. coli vector pK18 or pK19. These vectors have a number of useful features, including small size (4.4 kb), a multiple cloning site, and blue/white selection. To our knowledge, pNV18 and pNV19 are the first cloning vectors for practical use in Nocardia spp.

Dynamic Phenotypic Transition of Breast Cancer Cells In Vitro Revealed by Self-floating Cell Culture.

BACKGROUND: Breast tumor heterogeneity leads to phenotypic diversity, such as tumor-initiating and metastatic properties and drug sensitivity. MATERIALS AND METHODS: We found that a self-floating cell (SFC) culture enriches a drug-resistant subpopulation in a HER2-positive breast cancer cell line. SFCs were analyzed for cancer stem cell markers, gene expression profiles, and sensitivity for anticancer drugs. RESULTS: SFCs expressed cancer stem cell markers, such as aldehyde dehydrogenase (ALDH) activity and elevated HER2 autophosphorylation. Gene expression profiles of SFCs showed a dramatic difference compared to those of parental or forced floating cells. SFCs also expressed CD133, a marker of drug resistance, and resisted cytotoxic drugs by drug efflux transporters. In contrast, HER2 kinase inhibitors efficiently reduced SFC viability. CONCLUSION: SFCs enrich drug-resistant subpopulations even in vitro and might reflect the highly plastic nature of breast cancer cells even in vitro.

Modification of pyrimidine derivatives from antiviral agents to antitumor agents.

2,4-Diaminopyrimidine derivatives, that were originally developed as antiviral agents, were modified to antitumor agents by: (i) introducing an amino group at C-5 on the pyrimidine ring, (ii) changing the alkyl group and the ring size of the cycloalkyl group on the beta-position of the omega-hydroxyalkylamino group, (iii) replacing the phenylalkyl group on the cycloalkyl group with the 3,4,5-trimethoxyphenylalkyl group, (iv) the esterification of the primary alcohol with diethyl phosphate and (v) introducing the thiomethyl group at C-2 on the pyrimidine ring. Among the 21 compounds prepared, 6, which has cyclobutyl at the beta-position, exhibited potent activity towards P-388 leukemia. In addition, 14, with methoxyl groups on the phenyl ring and 17, with the thiomethyl group on the pyrimidine ring, showed specific inhibition for the EGFR protein kinase. Moreover, 15 and 16, which carry the diethyl phosphoryl group on the primary alcohol, exhibited inhibitory activity towards P-glycoprotein.

Design of hypoxia-targeting protein tyrosine kinase inhibitor using an innovative pharmacophore 2-methylene-4-cyclopentene-1,3-dione.

We review in this report our strategy and tactics for the design of 2-hydroxyarylidene-4-cyclopentene-1,3-diones as protein tyrosine kinase (PTK) inhibitors having low mitochondrial toxicities and/or hypoxia-targeting function. We based our synthetic design on an innovative pharmacophore, 2-methylene-4-cyclopentene-1,3-dione. We first showed the effectiveness of this pharmacophore in the development of 2-methylene-4-cyclopentene-1,3-dione as PTK inhibitor that have lower mitochondrial toxicity than the potent PTK inhibitor tyrphostin AG17. Our results show that the cyclopentenedione-derived TX-1123 is a more potent antitumor tyrphostin and also shows lower mitochondrial toxicity than the malononitrile-derived AG17. The O-methylation product of TX-1123 (TX-1925) retained its tyrphostin-like properties, including mitochondrial toxicity and antitumor activities. However, the methylation product of AG17 (TX-1927) retained its tyrphostin-like antitumor activities, but lost its mitochondrial toxicity. Our comprehensive evaluation of these agents with respect to PTK inhibition, mitochondrial inhibition, antitumor activity, and hepatotoxicity demonstrates that PTK inhibitors TX-1123 and TX-1925 are more promising candidates for antitumor agents than tyrphostin AG17. Secondly, as a further investigation of the promising power of this 4-cyclopentene-1,3-dione as an innovative pharmacophore, we discuss our strategy of development of hypoxia-targeting PTK inhibitor TX-1123 analogues, 2-nitroimidazole-aminomethylenecyclopentenediones, such as TX-2036, for cancer treatment, especially for pancreatic cancers, which have a high level of hypoxia.