A novel benzimidazole derivative binds to the DNA minor groove and induces apoptosis in leukemic cells

DNA minor groove binders are an important class of chemotherapeutic agents. These small molecule inhibitors interfere with various cellular processes like DNA replication and transcription. Several benzimidazole derivatives showed affinity towards the DNA minor groove. In this study we show the synthesis and biological studies of a novel benzimidazole derivative (MH1), that inhibits topoisomerase II activity and in vitro transcription. UV-visible and fluorescence spectroscopic methods in conjunction with Hoechst displacement assay demonstrate that MH1 binds to DNA at the minor groove. Cytotoxic studies showed that leukemic cells are more sensitive to MH1 compared to cancer cells of epithelial origin. Further, we find that MH1 treatment leads to cell cycle arrest at G2/M, at early time points in Molt4 cells. Finally multiple cellular assays demonstrate that MH1 treatment leads to reduction in MMP, induction of apoptosis by activating CASPASE 9 and CASPASE 3. Thus our study shows MH1, a novel DNA minor groove binder, induces cytotoxicity efficiently in leukemic cells by activating the intrinsic pathway of apoptosis.

An Endophytic Fungus, Talaromyces radicus, Isolated from Catharanthus roseus, Produces Vincristine and Vinblastine, Which Induce Apoptotic Cell Death

Endophytic fungi isolated from Catharanthus roseus were screened for the production of vincristine and vinblastine. Twenty-two endophytic fungi isolated from various tissues of C. roseus were characterized taxonomically by sequence analysis of the internal transcribed spacer (ITS) region of rDNA and grouped into 10 genera: Alternaria, Aspergillus, Chaetomium, Colletotrichum, Dothideomycetes, Eutypella, Eutypa, Flavodon, Fusarium and Talaromyces. The antiproliferative activity of these fungi was assayed in HeLa cells using the MTT assay. The fungal isolates Eutypella sp-CrP14, obtained from stem tissues, and Talaromyces radicus-CrP20, obtained from leaf tissues, showed the strongest antiproliferative activity, with IC50 values of 13.5 mu g/ml and 20 mu g/ml, respectively. All 22 endophytic fungi were screened for the presence of the gene encoding tryptophan decarboxylase (TDC), the key enzyme in the terpenoid indole alkaloid biosynthetic pathway, though this gene could only be amplified from T. radicus-CrP20 (NCBI GenBank accession number KC920846). The production of vincristine and vinblastine by T. radicus-CrP20 was confirmed and optimized in nine different liquid media. Good yields of vincristine (670 mu g/l) in modified M2 medium and of vinblastine (70 mu g/l) in potato dextrose broth medium were obtained. The cytotoxic activity of partially purified fungal vincristine was evaluated in different human cancer cell lines, with HeLa cells showing maximum susceptibility. The apoptosis-inducing activity of vincristine derived from this fungus was established through cell cycle analysis, loss of mitochondrial membrane potential and DNA fragmentation patterns.

Influence of recombination on acquisition and reversion of immune escape and compensatory mutations in HIV-1

Following transmission, HIV-1 adapts in the new host by acquiring mutations that allow it to escape from the host immune response at multiple epitopes. It also reverts mutations associated with epitopes targeted in the transmitting host but not in the new host. Moreover, escape mutations are often associated with additional compensatory mutations that partially recover fitness costs. It is unclear whether recombination expedites this process of multi-locus adaptation. To elucidate the role of recombination, we constructed a detailed population dynamics model that integrates viral dynamics, host immune response at multiple epitopes through cytotoxic T lymphocytes, and viral evolution driven by mutation, recombination, and selection. Using this model, we compute the expected waiting time until the emergence of the strain that has gained escape and compensatory mutations against the new host's immune response, and reverted these mutations at epitopes no longer targeted. We find that depending on the underlying fitness landscape, shaped by both costs and benefits of mutations, adaptation proceeds via distinct dominant pathways with different effects of recombination, in particular distinguishing escape and reversion. When adaptation at a single epitope is involved, recombination can substantially accelerate immune escape but minimally affects reversion. When multiple epitopes are involved, recombination can accelerate or inhibit adaptation depending on the fitness landscape. Specifically, recombination tends to delay adaptation when a purely uphill fitness landscape is accessible at each epitope, and accelerate it when a fitness valley is associated with each epitope. Our study points to the importance of recombination in shaping the adaptation of HIV-1 following its transmission to new hosts, a process central to T cell-based vaccine strategies. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license.

Extract of Vernonia condensata, Inhibits Tumor Progression and Improves Survival of Tumor-allograft Bearing Mouse

Medicinal plants are considered as one of the ideal sources for cancer therapy due to their bioactive contents and low toxicity to humans. Vernonia genus is one of the common medicinal plants, which has wide spread usage in food and medicine. However, there are limited studies to explore its anticancer properties. In the current study, we have used Vernonia condensata, to explore its anticancer activity using various approaches. Here, we show that extract prepared from Vernonia condensata (VCE) exhibits cytotoxic properties against various cancer cells in a dose- and time-dependent manner. Interestingly, when treated with VCE, there was no significant cytotoxicity in peripheral blood mononuclear cells (PBMCs). Flow cytometry analysis revealed that although VCE induced cell death, arrest was not observed. VCE treatment led to disruption of mitochondrial membrane potential in a concentration dependent manner resulting in activation of apoptosis culminating in cell death. Immunoblotting studies revealed that VCE activated intrinsic pathway of apoptosis. More importantly, VCE treatment resulted in tumor regression leading to significant enhancement in life span in treated mice, without showing any detectable side effects. Therefore, for the first time our study reveals the potential of extract from Vernonia condensata to be used as an anticancer agent.

Mitochondrial selectivity and remarkable photocytotoxicity of a ferrocenyl neodymium(III) complex of terpyridine and curcumin in cancer cells

A series of four novel neodymium(III) complexes of the formulation Nd(R-tpy)(O-O)(NO3)(2)] (1-4), where R-tpy is 4'-phenyl-2,2': 6', 2''-terpyridine (Ph-tpy; 1, 2) and 4'-ferrocenyl-2,2': 6', 2''-terpyridine (Fc-tpy; 3, 4); O-O is the conjugate base of acetylacetone (Hacac; 1, 3) or curcumin (Hcurc; 2, 4), are synthesized and characterized. The single crystal structure of 1 shows that the complex is a discrete mononuclear species with the Nd(III) centre in a nine coordinate environment provided by a set of O6N3 donor atoms. Complexes 1 and 3 having the simple acac ligand are prepared as control compounds. Complex 4, possessing an appended ferrocenyl (Fc) and the curcumin moiety, is remarkably photocytotoxic to HeLa and MCF-7 cancer cells in visible light giving respective IC50 values of 0.7 mu M and 2.1 mu M while being significantly less toxic to MCF-10A normal cells (IC50 = 34 mu M) and in the dark (IC50 > 50 mu M). The phenyl appended complex 2, lacking a ferrocenyl moiety, is significantly less toxic to both the cell lines when compared with 4. Complexes 1 and 3, lacking the photoactive curcumin moiety, do not show any apparent toxicity both in light and in the dark. The cell death is apoptotic in nature and is mediated by the light-induced formation of reactive oxygen species (ROS). Fluorescence imaging experiment with HeLa cells reveals mitochondrial accumulation of complex 4 within 4 h of incubation. The complexes bind to calf thymus (ct) DNA with moderate affinity giving K-b values in the range of 10(4)-10(5) M-1. The curcumin complexes 2 and 4 cleave plasmid supercoiled DNA to its nicked circular form in visible light via O-1(2) and (OH)-O-center dot pathways. The presence of the ferrocenyl moiety is likely to be responsible for the enhanced cellular uptake and photocytotoxicity of complex 4. Thus, the mitochondria targeting complex 4, being remarkably cytotoxic in light but non-toxic in the dark and to normal cells, is a potential candidate for photochemotherapeutic applications.