Sanjeev Meena

Synthesis and cytotoxicity evaluation of (tetrahydro-β-carboline)-1,3,5-triazine hybrids as anticancer agents

A series of tetrahydro-beta-carbolines and 1,3,5-triazine hybrids have been synthesized and evaluated for their cytotoxicity against a panel of eight human cancer cell lines and normal human fibroblasts (NIH3T3). It led us to discovery of racemic compounds 69, 71 and 75, which are selectively cytotoxic towards KB (oral cancer) cell line with IC50 values of 105.8, 664.7 and 122.2 nM, respectively; while their enantiopure forms are less active and not selective. Enantiopure compound 42 showed 2.5 times more selectivity towards MCF7 cells over normal fibroblast NIH3T3 cells with an IC50 value of 740 nM, also arrests cell cycle in G1 phase and induces apoptosis in MCF7 and MDA MB231 cell lines.

Antiproliferative action of Xylopia aethiopica fruit extract on human cervical cancer cells.

The anticancer potential of Xylopia aethiopica fruit extract (XAFE), and the mechanism of cell death it elicits, was investigated in various cell lines. Treatment with XAFE led to a dose‐dependent growth inhibition in most cell lines, with selective cytotoxicity towards cancer cells and particularly the human cervical cancer cell line C‐33A. In this study, apoptosis was confirmed by nuclear fragmentation and sub‐G0/G1 phase accumulation. The cell cycle was arrested at the G2/M phase with a decreased G0/G1 population. A semi‐quantitative gene expression study revealed dose‐dependent up‐regulation of p53 and p21 genes, and an increase in the Bax/Bcl‐2 ratio. These results indicate that XAFE could be a potential therapeutic agent against cancer since it inhibits cell proliferation, and induces apoptosis and cell cycle arrest in C‐33A cells. Copyright

Tumor heterogeneity and cancer stem cell paradigm: updates in concept, controversies and clinical relevance.

Although tumor heterogeneity is widely accepted, the existence of cancer stem cells (CSCs) and their proposed role in tumor maintenance has always been challenged and remains a matter of debate. Recently, a path‐breaking chapter was added to this saga when three independent groups reported the in vivo existence of CSCs in brain, skin and intestinal tumors using lineage‐tracing and thus strengthens the CSC concept; even though certain fundamental caveats are always associated with lineage‐tracing approach. In principle, the CSC hypothesis proposes that similar to normal stem cells, CSCs maintain self renewal and multilineage differentiation property and are found at the central echelon of cellular hierarchy present within tumors. However, these cells differ from their normal counterpart by maintaining their malignant potential, alteration of genomic integrity, epigenetic identity and the expression of specific surface protein profiles. As CSCs are highly resistant to chemotherapeutics, they are thought to be a crucial factor involved in tumor relapse and superficially appear as the ultimate therapeutic target. However, even that is not the end; further complication is attributed by reports of bidirectional regeneration mechanism for CSCs, one from their self‐renewal capability and another from the recently proposed concept of dynamic equilibrium between CSCs and non‐CSCs via their interconversion. This phenomenon has currently added a new layer of complexity in understanding the biology of tumor heterogeneity. In‐spite of its associated controversies, this area has rapidly emerged as the center of attention for researchers and clinicians, because of the conceptual framework it provides towards devising new therapies.

Pharmacophore-Based Screening and Identification of Novel Human Ligase I Inhibitors with Potential Anticancer Activity

Human DNA ligases are enzymes that are indispensable for DNA replication and repair processes. Among the three human ligases, ligase I is attributed to the ligation of thousands of Okazaki fragments that are formed during lagging strand synthesis during DNA replication. Blocking ligation therefore can lead to the accumulation of thousands of single strands and subsequently double strand breaks in the DNA, which is lethal for the cells. The reports of the high expression level of ligase I protein in several cancer cells (versus the low ligase expression level and the low rate of division of most normal cells in the adult body) support the belief that ligase I inhibitors can target cancer cells specifically with minimum side effects to normal cells. Recent publications showing exciting data for a ligase IV inhibitor exhibiting antitumor activity in mouse models also strengthens the argument for ligases as valid antitumor targets. Keeping this in view, we performed a pharmacophore-based screening for potential ligase inhibitors in the Maybridge small molecule library and procured some of the top-ranking compounds for enzyme-based and cell-based in vitro screening. We report here the identification of novel ligase I inhibitors with potential anticancer activity against a colon cancer cell line.

Synthesis of novel β-carboline based chalcones with high cytotoxic activity against breast cancer cells.

A series of novel β-carboline based chalcones was synthesized and evaluated for their cytotoxic activity against a panel of human cancer cell lines. Among them we found that two of the compounds 7c and 7d, showed marked anti-proliferative activity in a panel of solid tumor cell lines with highest effect in breast cancer. The compounds 7c and 7d showed an IC50 of 2.25 and 3.29 μM, respectively against human breast cancer MCF-7 cell line. Further, the compound 7c markedly induced DNA fragmentation and apoptosis in breast cancer cells.

Diastereoselective one-pot Wittig olefination–Michael addition and olefin cross metathesis strategy for total synthesis of cytotoxic natural product (+)-varitriol and its higher analogues

A stereoselective route for the total synthesis of anticancer marine natural product (+)-varitriol (1) is detailed herein. The impressive biological activity and interesting structural features of natural (+)-varitriol fuelled us to undertake the synthesis of some higher analogues (1a-j) of this molecule. The key features of the synthetic strategy include one-pot Wittig olefination followed by a highly diastereoselective oxa-Michael addition to assemble stereochemically pure tetrasubstituted THF moiety of the natural varitriol and olefin cross metathesis to couple the aromatic part with tetrasubstituted THF moiety. The total synthesis of title natural product is efficient with 21.8% overall yield for 9 linear steps from D-ribose and thus facilitates the more scaled-up practical route for the synthesis of 1 and its analogues as well. The synthetic (+)-varitriol (1) and its analogues were screened for their cytotoxicity. The present synthetic approach paves the way for preparation of numerous analogues of the title natural product for drug development.

Synthesis of 2-(pyrimidin-2-yl)-1-phenyl-2,3,4,9-tetrahydro-1H-β-carbolines as antileishmanial agents

A series of 2-(pyrimidin-2-yl)-1-phenyl-2,3,4,9-tetrahydro-1H-beta-carboline derivatives has been synthesized and evaluated for antileishmanial activity against Leishmania donovani. Compound 8 exhibited best antileishmanial activity with IC(50) value of 1.93 microg/ml against amastigotes, high selectivity index, and was more active than reference drugs sodium stilbogluconate and pentamidine.

Staurosporine induces apoptosis in human papillomavirus positive oral cancer cells at G2/M phase by disrupting mitochondrial membrane potential and modulation of cell cytoskeleton

Our study demonstrates that staurosporine (STS), a protein kinase inhibitor from Streptomyces sp., induces apoptosis in human papillomavirus positive oral carcinoma cells (KB) in a dose dependent manner. Growth inhibition studies revealed an IC(50) value of approximately 100 nM. STS induced marked nuclear fragmentation and inter-nucleosomal cleavage compared to untreated cells. It also caused dose dependent disruption of mitochondrial membrane potential and activation of caspase-3, indicating involvement of mitochondria-mediated cell death signaling in KB cell apoptosis. We found time-dependent arrest of the KB cells at G2/M phase of cell cycle. Using fluorescence microscopy, we have further shown that STS treatment disrupts microtubules and reorganizes F-actin after 6h exposure. Taken together, our results suggest that STS induces mitochondria-mediated KB cell apoptosis at G2/M phase by altering cell cytoskeletal network.

Anti-breast tumor activity of Eclipta extract in-vitro and in-vivo: novel evidence of endoplasmic reticulum specific localization of Hsp60 during apoptosis

Major challenges for current therapeutic strategies against breast cancer are associated with drug-induced toxicities. Considering the immense potential of bioactive phytochemicals to deliver non-toxic, efficient anti-cancer therapeutics, we performed bio-guided fractionation of Eclipta alba extract and discovered that particularly the chloroform fraction of Eclipta alba (CFEA) is selectively inducing cytotoxicity to breast cancer cells over non-tumorigenic breast epithelial cells. Our unbiased mechanistic hunt revealed that CFEA specifically activates the intrinsic apoptotic pathway by disrupting the mitochondrial membrane potential, upregulating Hsp60 and downregulating the expression of anti-apoptotic protein XIAP. By utilizing Hsp60 specific siRNA, we identified a novel pro-apoptotic role of Hsp60 and uncovered that following CFEA treatment, upregulated Hsp60 is localized in the endoplasmic reticulum (ER). To our knowledge, this is the first evidence of ER specific localization of Hsp60 during cancer cell apoptosis. Further, our LC-MS approach identified that luteolin is mainly attributed for its anti-cancer activities. Moreover, oral administration of CFEA not only offers potential anti-breast cancer effects in-vivo but also mitigates tumor induced hepato-renal toxicity. Together, our studies offer novel mechanistic insight into the CFEA mediated inhibition of breast cancer and may potentially open up new avenues for further translational research.

Isolation, Characterization and Anticancer Potential of Cytotoxic Triterpenes from Betula utilis Bark.

Betula utilis, also known as Himalayan silver birch has been used as a traditional medicine for many health ailments like inflammatation, HIV, renal and bladder disorders as well as many cancers from ages. Here, we performed bio-guided fractionation of Betula utilis Bark (BUB), in which it was extracted in methanol and fractionated with hexane, ethyl acetate, chloroform, n-butanol and water. All six fractions were evaluated for their in-vitro anticancer activity in nine different cancer cell lines and ethyl acetate fraction was found to be one of the most potent fractions in terms of inducing cytotoxic activity against various cancer cell lines. By utilizing column chromatography, six triterpenes namely betulin, betulinic acid, lupeol, ursolic acid (UA), oleanolic acid and β-amyrin have been isolated from the ethyl acetate extract of BUB and structures of these compounds were unraveled by spectroscopic methods. β-amyrin and UA were isolated for the first time from Betula utilis. Isolated triterpenes were tested for in-vitro cytotoxic activity against six different cancer cell lines where UA was found to be selective for breast cancer cells over non-tumorigenic breast epithelial cells (MCF 10A). Tumor cell selective apoptotic action of UA was mainly attributed due to the activation of extrinsic apoptosis pathway via up regulation of DR4, DR5 and PARP cleavage in MCF-7 cells over non-tumorigenic MCF-10A cells. Moreover, UA mediated intracellular ROS generation and mitochondrial membrane potential disruption also play a key role for its anti cancer effect. UA also inhibits breast cancer migration. Altogether, we discovered novel source of UA having potent tumor cell specific cytotoxic property, indicating its therapeutic potential against breast cancer.